I ‘ 0' . ' I x . I. I“ . 5. I .‘.. b v . o. ‘ 1! | O u ' .l " ,' '1' t I . I a ' II . '. .- ‘.:.I.nu.I' 7-. 1;. ' .\ ' . ' "I. I 'I . . n;:| r ”L’SF'IJ'WLV u ~-~‘_'.‘. . ' I n . r . 1 4.. :4 q f. 1 I'IIII.‘ II- IIIII ; . [It ' lift” II.” ' ” . 5'. " '3'» p1; -.~. :1. fig}. I '1'” '9*'.$.' 1': u'o ‘ l"‘ u "'|‘s nu: “Lu. |',1"y"“ & " 5W w «w a 5' 5:5. ' ‘ m5 . Ian-{235$ .. I II !‘ III! ql. ‘i. I-I ' . .I... '. -ILI 5.”. 5“- '5. ‘ . . . \ .‘ _ II I n U ‘ .. .,I 5\,"."‘.\-, ' .u'i-s .’ 'J._i'5'r~‘:a»;._'414"}.EII. - ~ ’---' t I 0’ 5 ' 'Ié' 34 ”:3, \Ibllg“ >‘I ‘I‘ I". “Z"; QM" LIA" :. ,' ‘x‘ u. A.“ 3' | ~ . ‘ I I , g. 1‘ J . 4 ”03,1“ .Jf'.' tr~5 3:55-01“ fir, ' u; ‘y'\+',f. {\(I‘: 5'.“ . - a ‘u I..I I 1...-an ~ 0 .' - u .':\""“ I” ”Win-In- “1‘“: prII , 4, .‘ JIhI _. V . -. V . (v I. I5-{Ir .. ." Mr ‘o'N" w 4;,“ .- u.\' .‘.'..‘..';/13 ._r . I V - I I, , "v. -ll<-u . 0" "'l‘.#'"" ‘ .H'u.‘ n . . u ¢.. '..‘. ”SI ‘I._" -In '5. I.« I . : : ‘- .I;. I z ‘ u .'.I. mi. ‘Hx‘.l’?.'5 i) .fl’xt 'L‘f‘ 1-6.1: 5.. KL“ 5.\'-!‘5;1i;;{?i;.. ' fisé‘fi 2323?.”‘14? «19:72:33., A. :‘ ;_-7_;~.- '.-~ ...'I..|5:IL..',.‘r'II\ -,‘ ,.-,- "W”‘leE- 4.5. .,4._-£.--..-f 15“ :«p ‘5“- ‘ ‘ I ‘5 v ”Lu—"1",- 4 ALI‘ I I’ ~v ‘d.".. at“ 1 u ~""’“wb("'.\-“ 4 "‘35-" I '- . 1.. - .wummw “L a v 1{1-~_|- .3 5])..T' ."\’.‘ y, '5‘? - n ’ 4'3: ‘ ‘. arr 17:}: 2‘: . ‘:'A','.C-."". "to" E. a )5] uh)! Thug) '. .r " \‘I" 1 '- *5 J . :3,- l .'. 45,." .: .1. .9597? :Liiw' ".5 5. 35.4w}?! 5 --A‘ - 5g - «#52515: M» J L. ,I‘a'u'u (aqua? (“16:“). &:.'7 £sz .. ' , v. w. -~ ES. . .- 55:5 H‘I’ . .”31rd:wwhwqfi.‘ - -:‘<‘ v ‘ .I III . ' I ”I , _ . .. I '39 l . _' " ‘ q - '3.“ IJ:," 1'3].sz 6 '1“; l - .' 52’ -- [haw 5» .‘zg' I ;.'.5.I\i:t~‘?.I-u.1v "E-ng} '5'" "4”." .5 i <5.-’;$r25'£52:4.i“{|".‘ 21.5535.“ 9‘ W 5, V); ' 2573:} :.'3' per-$9 .. . 0‘71- “_ 1’ “Inn. 7.” a Tran -0. o ‘ 355515) Ice ‘5 :7 Lil" I I If; “3% q I . j ' ‘ 3 ‘3‘ '3-"fx‘fitgf'tp I . ,5 5| I - I? -_ 5‘ .‘ . ‘3‘ ,' - "5.2?- zis‘ryw‘é’k »- ‘ . I - .-O l . II - 3 _ ‘ A ZIW'I-Kfl“ I” quffiiv't". ’ Vb xk‘y ' .I «light f 1L? \ . .3 w . . v-.- , '35.;- wk: a W .213 . mam-:1 5 ; .. 34%. .- ‘. g~ fi. 5\ 7'50" '1 h -'\: - V {N ~ , ". ‘ ‘ I“ I"~ 5 ’9' 1 IA "1 u Ytfl. . (" "‘11::‘3 “£393.!- . N. A'.' ‘r ‘- . 5 " :‘H": 4‘ nu 5‘" .‘ a . 5 w - .1:- é-CQ" 5‘ v: If: ',.}'\ 515?}.‘f1v :651' . . 7 TE" '§5‘L“t€{-‘-§' ’34-'35 -,o . a 5: ti»?! ' .1.“ k t \ I _ 1‘ Ni: «.4 437.559 . c 5L -* r- I 455ss*aé< I 5333; ' '. '1’. .L“ . -?r;~. H“ Is. m;- ' L - 0:»; 1;! ' 5 int)! 'i Ax 7. o L.‘ ' Fl: 2 ‘. 9153 N55- }; K1 :I‘qu' . a“ L353? ' .‘._1 q '-\. .‘q . - \ M, In ‘I' ': .: ‘1'" I '~ 5 : I1! [r’hilll _ .l If. :5 at 553% 'L1 «as. -. m‘ -. --""7‘4¢V\'.‘» 1 .5:.')'-'~.'w'-"“‘\'I 5D "pity-‘1“; 5"?" 4.7.1.5 1’?- '1): ' “Eats fl .mm IA 9‘“, Gaugurg, :‘ fl -..:.‘.n:..-= r.1.__.‘_r., .‘U‘U‘Iik-;. ”Ema” . 24.39ng I. -c—n‘h Luke-ruq This is to certify that the thesis entitled SYNTHESIS OF YTTERBIUM DIHALIDES AND AN X-RAY DIFFRACTION STUDY OF YTTERBIUM MIXED DIHALIDE SYSTEMS presented by Christine Voos—Esquivel has been accepted towards fulfillment of the requirements for M. S . degree in Chemistry 7/429, / {a r professor Date fl ,/¢_,/fl/ 0.7639 MS U is an Affirmative Action/Equal Opportunity Institution MSU LIBRARIES .—_—. RETURNING MATERIALS: Place in book drop to remove this checkout from your record. FINES will be charged if book is returned after the date stamped below. SYNTHESIS OF YTTERBIUII DIHALIDES AND AN X-RAY DIFFRACTION STUDY OF YTTERBIUIC MIXED DIHALIDE SYSTEMS By Christine A. Voos-Esquivel A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Chemistry 1986 ABSTRACT SYNTHESIS OF YTTERBIUM DIHALIDES AND AN X-RAY DIFFRACTION STUDY OF YTTERBIUM MIXED DIHALIDE SYSTEMS By Christine Voos-Esquivel Many diverse synthetic routes have been developed for the preparation of ytterbium dihalides. Most of these routes either involve multistep reactions or are otherwise complicated. In this work a high temperature synthetic procedure was developed for the preparation of YbCh and YbBr3, and a low temperature procedure for the preparation of th. The pure ytterbium dihalides were combined by high temperature fusion techniques to produce mixed halides and the mixed halide systems; Yblz-YbCla, YbIa-YbBra and YbCh-YbBr: were characterized by x-ray diffraction. The YbCh-YbBrz system exhibited the Srh-type structure throughout the entire composition region. In the other two mixed halide systems, new phases were identified but not characterized. Phase diagrams are presented and are compared to those observed in other mixed halide systems. ACKNOWLEDGMENTS I acknowledge the professors at Virginia Tech., especially Dr. Taylor, Dr. Ogliaruso, Dr. Bell, Dr. Kingston, Dr. Wightman and Dr. McNair. They taught me the fundamentals of chemistry. A special acknowledgment goes to Dr. Mason. His encouragement helped me to continue my pursuit of a chemistry degree. Turning to Michigan State, Dr. Harrison’s role as a teacher gave me a different perspective of chemistry, and his role as advisor helped me to surmount some seemingly impossible obstacles. To Dr. Eick, he assumed many roles including teacher, advisor and research director. He has been a major factor in transforming my dream of becoming a chemist into a tangible degree. And lastly, to my husband, Benjamin, whose emotional and psychological support has always been constant throughout my five year struggle. I thank you. All of you have been a major influence in my growth as a chemist. I would like to acknowledge the support provided by the National Science Foundation, Division of Materials Research (DMR 84-00739). ii TABLE OF CONTENTS Page LIST OF TABLES ................. . . . . . . . . . iv LIST OF FIGURES . . . . ..................... vi INTRODUCTION ........................... 1 Practical Uses ....................... 1 General Background. . . ............... . . . 2 Goals ........................... 3 HISTORICAL ............................ 4 General Synthetic Methods ..... . . . . . . ...... 4 X-Ray Diffraction . ............ . . . ..... 12 EXPERIMENTAL ................... . . . . . . . . 18 Reagenta. O O O O O O O O O 000000000 O O 18 General Synthetic and X-Ray Equipment .......... . 20 Synthetic Procedures ............. . . . . . . . 27 Procedures for Melt Experiments .............. 34 Procedures for X-Ray Diffraction ....... . . . . . . . 38 RESULTS ............................ 41 Synthetic .......... . . . . . . . . . . . . . . . 41 X-Ray Diffraction .................... . 48 DISCUSSION ......... . ..... . . . . . . . . . . . . . 58 Synthetic ..... . ..... . . . . . . . . ...... 58 X-Ray Diffraction ............ . . . ..... . 68 YbBrz-YbClz System ........... . ...... 68 YbClz-Yblz System . . ....... . . . . ..... 78 YbBrz-Yblz System .................. 82 Conclusion .............. . . . . . . . . 87 FUTURE EXPERUMENTS. . . . .................... 91 REFERENCES ...... . . . . . . . . ..... . . . . ..... 93 APPENDICES. . . . . . ........ . . . . . . . . . ..... 97 iii Table 10 11 12 13 14 15 16 17 LIST OF TABLES Reagents Used for Synthetic Work. . . . ......... Laboratory Data for YbClz-Yblz Melt Experiments ..... Laboratory Data fer YbBrz-YbC12 Melt Experiments ..... Laboratory Data for YbBra-Yblz Melt Experiments . . . . . . Percent Yields of YbClz, YbCla and YbIz ......... Percent Yields of YbBrz and YbBra ............ Percent Recovery - YbClz/YbIz System. .......... Percent Recovery - YbBrz/YbClz System. ....... . . . . Percent Recovery - YbBrz/Yblz System ........... A Comparison of Ytterbium Dihalides to Ytterbium Oxide Halides by X.R.D. Patterns ............. Lattice Parameter Composition Data for YbClz /YbBr2 Syst- .................... Lattice Parameter Composition Data for the Hexagonal, CdIz-Type Structure-YbClz/Yblz System. . . . . . Lattice Parameter Composition Data for the Orthorhombic, Srlz-Type Structure-YbClz/YbIz System . . . . Lattice Parameter Composition Data for YbErz /YbIz System .................... Structure-Types Examined in an Attempt to Index Unexplained Reflections in YbBrz/YbClz System . . Structure-Types Examined in an Attempt to Assign Reflections of the New Phase in YbClz/Yblz System . . . . Average Yb-Br Interatamic Distances, Coordination Number of Anion and Cation, and Geometry of Er Anions of the Four Structure Types fer YbBrz ...... . . . . . iv Page 19 35 36 37 42 43 46 47 50 52 53 55 56 57 7O Table Page 18 Comparison of Observed and Calculated Intensities for Low Angle Reflections in YbClz/YbBrz System at 75 and 55 Mole Percent YbBrz. ............... 75 19 Phases Exhibited in YbBr/Yblz(RéO)x System. . . . . . . . . 85 LIST OF FIGURES Figure Page 1 Structure of SrIz. ........ . ............ l4 2 Simple Orthorhombic Bravais Lattice ............. 15 3 Hexagonal Dravais Lattice .................. 16 4 Simple Tetragonal Dravais Lattice .............. l7 5 Three Types of Glassware Used in Synthesis Experiments . . . 21 6 Vacuum Apparatus Used for Synthetic Methods ......... 22 7 Induction Generator for Synthesis Experiments. . . . . . . . 23 8 Equipment Used for Melt Experiments ..... . . ...... 24 9 Glass Boat Used to Support and Transport Melt Experiments. . 25 10 Optics of Guinier X-Ray Diffraction Instrument ....... 26 11 A Plot of Lattice Parameters and Unit Cell Volumes for YbClz/YbBrz System ..... . ......... 51 12 A Plot of Orthcrhcmbic and Hexagonal Lattice Parameters and Unit Cell Volumes for YbClz/YbIz System . . . 54 13 Structure Types for the YbBrz/YbIz System .......... 86 vi INTRODUCTION Practical Uses Alkyl ytterbium dihalides are used as grignard-type“ reagents in organometallic chemistry. The grignard reagent has the general formula of RMgX ( R = alkyl, X = halide). A typical reaction of RMgX is with aldehydes and ketones to yield alcohols. The R group functions as a nucleophile which readily transfers its electrons to the electropositive carbon of the carbonyl group of a specific ketone or aldehyde. The electrophilic portion, MgX, attacks the oxygen of the carbonyl group. Finally, the addition of water removes the Mg)! and an alcohol is formed. Before 197 7, lanthanide dihalides were generally synthesized by reduction of the trihalide with hydrogen or a metal at high temperatures. In 1977, a room temperature preparatory procedure was reported” in which ytterbium metal reacts with THF solutions of 1,2- diiodoethane. The reactivities of these powerful reducing agents, YbXa, have been appliedn to conjugated double bond compounds such as cinnamic acid which have been reduced to 3-phenylpropionic acid. Octanal can be converted to l-octanol. By an exchange reaction, new divalent compounds, such as Yb(OEt): and Yb(0Ac):” were synthesized by use of YbIa as an intermediate and RONa ( R = Et or Ac) as a reactant. Recently, ytterbium metal has been explored for use as a catalyst.“ Butadiene has been reduced to butenes at 20-64°C by a Yb- Ar-TI-IF matrix and hydrogen. General Background Ytterbium metal is a powerful reducing agent, (1%“ 4» 3e“ -> Yb, E' = -2.27 V)(Yb" + e' 9 Yb”, 8' = -l.21 V). In all MSU synthetic preparations, oxidation of ytterbium by the metal halogen compound was pursued (for example, Yb 4- ZnCh + YbCh 4- Zn). Ytterbium can be considered a transition metal by the following arguments. Another metal, lanthanum is placed in the periodic chart in group IIIB position, but Jensen”( 1982) and other chemists put lutetium in this place. In the case of lutetium, the highest common oxidation state is ’3 with a [lie ] 4f1 ‘ electron configuration. Likewise, one common oxidation state for ytterbium is +2 with a [Xe]4f“ electron configuration. If Lu can be considered a transition element due to its [Xe]6s’4 f1 ‘5d1 electron configuration, and is placed in group IIIB with Sc [Ar](3d‘4s2) and Y [Ar](4di5sz), then ytterbium 2+ can likewise be considered a transition metal based on the comparison of the electron configuration of Yb(+2) to Lu(+3). La would be placed at the beginning of the lanthanide series instead of Ce. Atomic radii, ionization potential, and electronegativity trends of the Sc-Y-Lu group versus those of other transition metal groups support Lu being in the group IIIB position. The elements Sc, Y and Lu have the following common properties: oxidation state, structure of the metal at room temperature, structure of the oxide and structure of the chloride. The elements Sc, Y and La don’t have these common properties. 92215 By continuing to pursue an understanding of new phase formation of mixtures of two solids, the area of solid state chemistry with practical applications in material science will be explored through the following goals: 1. 2. Development of a one-step, fast high temperature preparatory procedure for YbClz. All reported preparations involve one or more of the following: 1) two step reactions 2) extended time period (one week) 3) special conditions--low temperature or solvents Development of a one-step high temperature preparatory procedure for YbBrz. All reported preparations involve low temperature techniques, solvents at room temperature or two-step reactions. Development of a one-step low temperature preparatory procedure for YbIz. All reported preparations involve one or more of the following: 1) Yb(s) + Ia(g) which is potentially hazardous 2) low temperature 3) room temperature with solvents Characterization by X.R.D. (x-ray diffraction) of the high temperature mixed halide systems: YbIz-YbClz; YbIa-YbBrz and YbClz-YbBrz. Identification of and reasons for new phase formation will be examined. HISTORICAL General Synthetic Methods This historical section presents an extensive chronological review of reported synthetic techniques for both ytterbium dihalides and trihalides. This section ends with a summary of ytterbium dihalide and trihalide preparatory procedures. Unusual oxidation states of selected actinide and lanthanide elements including ytterbium are discussed in a 1960 review article.’1 The first reported preparation of YbCh was that of Klemm and Schuth (1929)" by hydrogen reduction of YbCh at Goo-620°C. Taylor (1962)1 discussed the preparation of anhydrous lanthanide halides from lanthanide oxides or hydrates. He presented a comprehensive summary of all the published work up to 1961. At that time, pure lanthanide metals were not available, so direct metal-halogen synthetic routes were impossible. Lanthanide trichlorides were synthesized by dehydration of hydrated trichlorides in a stream of HCl at 350°C or N340] at 300°C or by conversion of oxides by use of 8:013 and Cl: at 700-800°C. Also, lanthanide oxide has been added to 001: at 400-500°C. Reported lanthanide tribromide preparations involved treatment of hydrated bromide salts with HBr at 600°C and NmBr at 350°C. Lanthanide triiodides were prepared by conversion of the oxide by N841 at 350°C. Lanthanide trihalides, LnXa, were produced when lanthanide oxide was combined with NR¢X and RX, where X = Cl, Br or I as indicated in a later literature report.’ These reactants were combined in a beaker, dissolved to produce a clear solution, and subsequently evaporated to dryness on a hot plate. The resulting solid was transferred to a Pyrex glass tube which was evacuated. The tube was placed in an oven and heated to 200°C so the starting materials can react. During this heating, water was also removed. The temperature was then increased to 430°C to sublime the ammonium halide. After cooling the tube and filling it with nitrogen, the lanthanide halide was removed to a dry box. A similar procedure was used successquy for preparation of all lanthanide halides except SmIa and Sub. To determine the vapor pressure of dea,’ ytterbium dichloride was synthesized from YbCh, mixed with a two fold excess of Zn in a quartz ampoule which was coated internally with molybdenum, evacuated and filled with argon. These reactants were heated at 900-950°C for 30 min. The YbCla was made by the addition of chlorine gas to Yb:Oa at GOO-700°C. Lanthanide triiodides were prepared by the reaction of elemental lanthanides with th at 500°C for 2 hours.‘ YbIa could not be prepared by this procedure, but was synthesized by confining elemental Ia and Yb in a thick walled quartz tube. The quartz tube was cooled in an ice bath, evacuated and sealed. This sealed ampoule was placed in a capped steel pipe to prevent damage in case of an explosion, and the assembly was heated in a muffle furnace at 500°C. YbCla was synthesized“ for a dissociation pressure measurement by the reaction of ytterbium oxide in a stream of chlorine gas saturated with 001; vapor. This reaction took place in a tubular furnace at 700- 720°C for 10-15 hours. Howell and Pytlewski (1969) wrote two papers, one on the synthesis of divalent europium and ytterbium halides in liquid ammonia' and the other on the decomposition products of both metals in liquid ammonia.’ Yb and Eu halides were made by the following reaction: M + 2mm: “N" ,MX: + 2N3. + H: M : Eu, Yb; X = Cl, Br, I Each metal-halogen compound was analyzed for metal, halogen, nitrogen and hydrogen content. In the Yan and YbCl: analyses, 0.05% and 0.2%, respectively, were not accounted for. Oxygen could be a likely contaminant as shown from the MSU experimental work. For the YbIa synthesis, the analysis showed a 0.44% excess which could be hydrate by-products. A further extension of the Taylor procedure' for preparation of YbCh was tried.” In the DeEock and Radtke procedure,“ the appropriate metal oxide is added to BC], 1011401 and ZnCh. Then, this mixture is evaporated to dryness. Elemental zinc is added to the resulting solid which is placed in a quartz tube and heated at 200°C under vacuum to remove 11:0 and excess mum. A metal and chlorine analysis showed 0.41% not accounted for. Again, oxygen could have been a by-product. Anhydrous ytterbium trichloride and dichloride were made by the following procedures:u l. Hydrated ytterbium trichloride was placed in a vitreosil boat which was situated in a silica combustion tube through which anhydrous hydrogen chloride was passed. The temperature was increased slowly to 150°C. The flow of the HCl gas was stopped and the pressure inside the tube was reduced to remove the water. The result was anhydrous YbCls. 2. YbCh was made by heating YbCh and Yb in a molybdenum crucible at a temperature of 850-900°C for 3 hours. 3. YbCla was mixed with zinc and heated to produce YbCh. A 0.5% w.w. oxide contaminate was found. 4. Yb was heated in a stream of H: and HCl at 850-900°C. A mixed valence compound, 3YbCla-5YbCl: resulted. Corbett (1972)u postulated that lanthanide triiodide reacts with an SiOs quartz reaction vessel at 800°C by the following equation, 2LnIa(s) + SiOa(s) + 2LnOI(s) + Silo(g). Therefore, the suitability of quartz as a reaction vessel for iodides was put into question. A new method” for preparing lanthanide trihalide was proposed. In this method, the metal was allowed to react with an excess of molten mercuric halide in a Pyrex tube at a temperature of 300°C. All trihalides except that of Yb were made. The excess mercuric halide and mercury were removed by sublimation. All metal trihalides were then purified and sublimed in a tantalum container under vacuum. Corbett (1973)” synthesized rare earth trihalides by reaction of the metal with RC1, Br: or I3. Molybdenum boats were used for the chloride synthesis whereas tungsten boats were used for the bromide and iodide syntheses. The rare earth trihalides were distilled and the metal-metal trihalide phase diagram was determined. Both YbCla—Yb and YbIa-Yb systems were examined in this study. A sodium reduction of ytterbium trihalides in BMPA (hexamethyl phosphoramide) at room temperature yielded YbX2.”'1’ The anhydrous ytterbium trihalides were prepared by the ammonium halide method. All work was done in a dry box filled with argon. In 1977, the first reaction of ytterbium with 1,2-diiodoethane under an argon atmosphere in a T.H.F. solvent at room temperature was reported.” YbIz was produced. In another report, ytterbium metal in T.H.F. is added to the appropriate mercuric halide at room temperature in a Schlenk assembly under dry nitrogen.“ The ytterbium trihalide produced is extracted in a soxhlet assembly. The properties of ytterbium 2+ in solutions of HMPA, acetonitrile and ethanol were reported.” YbIz and YbCl: were prepared by the following high temperature methods and later dissolved in each solvent. YbIa was prepared by the addition of Yb to CuI and YbCla was reduced by Yb to YbClz. YbBrz(THF)z was isolated in 60-80% yield by a method which allowed Yb to react with 1,2-dibromomethane in T.H.F. at room temperature.23 Also, YbIa(THF)a and YbIz(CHsCN)s were isolated by the Yb-diiodoethane synthetic route. The synthesis of YbIz by the action of diiodoalkanes (alkane = methane, butane) on ytterbium metal in T.H.F. in a Schlenk apparatus at room temperature was reported.” Dioxan, diethylether, and dimethoxyethane were tried unsuccessfully as other solvents in lieu of T.H.F. Ytterbium dichloride2° was obtained by the reduction of the trichloride with hydrogen at 650°C or Yb in a molybdenum or quartz ampoule at 750°C . Reactions of organolanthanoid'" compounds are summarized. The synthesized complexes yield YbClz or YbI: as undesired end products. A study of the kinetics of the oxidation of ytterbium 2+ in aqueous and an aqueous/ethanol solution was reported.” The YbCla was made by adding 99.9% pure Yb metal to YbCla and heating the mixture to 800°C in a molybdenum crucible in an oxygen free argon atmosphere. The temperature and time dependence of the iodination of ytterbium was studied” by reacting metallic Yb with iodine to form YbIz and YbIs. The reaction vessel was quartz which was evacuated to 1x10" torr and cooled in liquid nitrogen. The melting point of YbI: was found to be 772 i 4°C. The synthetic methods for preparing divalent ytterbium halides vary from: 1. 5. 6. 8. 10 YbXaU) + Hz(g)(reduction) X=Cl"' YbX:(1) + Yb(s)(reduction) X301“ Ysz(s) + Zn(1)(reduction) X=CI3 YbXa(s) + Al,Sn(l)(reduction) X=Cl5 Yb( s) + Xz(g)(halogenation) le” Yb(s) + NH4X(solv) in liq. NH3(low temperature) X=Cl,Br,I' szOa(s) + HX(aq) + NH4X(aq) + ZnX2(1) + Zn(1)(reduction) X=Cli° YbX3(s) + Na(s) in HMPA(reduction)(room temperature) X = Cl, Br, I ‘3 Yb(s) + XCI-laCI-I:X(s) in T.H.F.(room temperature) X=I°° 11 10. Yb( s) + CuX( 1) (oxidation) X = I ’3 The synthetic methods for preparing trivalent ytterbium halides vary from: 1. Yb203(s) + Xz(g), HX(aq), (halogenation) X2 Cl: in 00149 8:01: and Cl: ‘ HX NI-IsBr + HBr 3 mm + HI 3 NH401 + 1101 3 2. Ln(s) + Hng(l)(oxidation) Ln except Yb; X = Cl, Br, I ‘ Ln 2 Yb; X(in THF) : Cl, Br, I (room temperature)” 3. YbXa-H30(s) + HX, NH¢X(dehydration) X:Cl,Br,I1 4. Ysz(s) + Xa(g) (halogenation) X:I‘ 5. Yb(s) + HX(g)or Xa(g)(oxidation) X=Cl,Br,I” 12 HISTORICAL X-Ray Diffraction This section presents a brief chronological review of the papers on x-ray diffraction that concern both ytterbium dihalide and ytterbium mixed halide systems. The structure of YbIz was determined (1960) to be hexagonal with the following lattice parameters: a = 4.503(3) and c = 6.972(4)A“ The YbI: was synthesized by the reaction of Yb with YbIa at 550°C under vacuum. Also, YbIa prepared by reaction of Yb dissolved in liquid NH: with NHaI was found to exhibit a cubic structure with the following lattice parameter: a = 4.404(2)A“ The crystal structure for YbBr: was reported (1971) to be isostructural" with that of CaClz with the following lattice parameters: a = 6.63, b = 6.93, and c = 4.37A The same paper states that YbI: is isostructural with CdIa and YbClz is isostructural with SrIz. The last structure, that of YbClx, was known (1971) to have the following lattice parameterszlwo a = 13.18, b = 6.96, and c = 6.70A A book“ on lanthanide, halides, actinide halides and oxide halides describes the YbCla structure as a seven coordinate Yb cation with four halogens at the corners of a square and three other halogens at the corners of an equilateral triangle (Figure 1). One of the YbBr: structures exhibits a distorted rutile type structure with octahedrally coordinated cations. Finally, YbIz exhibits a CdIa layered structure containing octahedrally coordinated cations (Figure 3). 13 Yan was found to be polymorphic with an SrIa type phase" with lattice parameters, a = 13.786, b = 7.358 and c = 7.088A Later, YbBr: was found to exhibit four temperature dependent structure types (1981)” as follows: Srlz (Figure 1), a—PbO: (Figure 2), CaCl: (Figure 2) and rutile (Figure 4). Lattice parameters for all these structure types were reported. 14 Figure 1. Structure of Srla, adapted from reference 48. 15 Figure 2. Simple Orthorhombic (P) Bravais lattice with three unequal orthogonal axes indicated. Both s—Pb02 and CaCla structures exhibit this symmetry. 50' ,, Figure 3. Hexagonal (P) Bravais lattice with cell edges and non- orthogonal angle indicated. 17 Figure 4. Simple Tetragonal (P) Bravais lattice with orthogonal edges indicated. Rutile (Ti0:) exhibits this symmetry. 18 EXPERIMENTAL Reagents In any synthetic experiment, the percent purity and the impurities of each the reagents used is very important. The reagents selected for this work are listed in Table 1. Table 1. Compound or Element Ytterbium-Yb (Yb-Ma-141D) Ytterbium-Yb (62973)(ultrapure) Mercuric Iodide HgIz Zinc Chloride ZnClz Zinc Bromide ZnBr2(85131) Hydrochloric Acid HCl Mercuric Bromide HgBrz Tantalum Ta Mercuric Chloride M12 19 Reagents Used for Synthetic Work. Purity (X) Impurities (X) 99.9 0.03 Mg (0.01 others 99.9 all ppm levels Analytical Hg Matter-0.10 Reagent Grade Other (0.02 Reagent Substance not ACS 97.0 pptd. (NHA)2S-0.2 SOs-0.01 Other < 0.005 99.83 No other information ACS (0.001 electronic grade 36.5-38.0 Reagent C1-0.25 Grade insol ACS in MeOH‘ 0.05 unavail. unavail. Certified Residue ACS Grade after ignition (0.018 Fe 0.0008 Manufacturer Research Chem. Phoenix, AZ. Research Chem. Phoenix, AZ. Mallinckrodt St. Louis, MO. Matheson, Coleman & Bell Norwood, OH. Alfa Products Danvers, MA. Columbus Chemical Ind. Columbus, WI. Matheson, Coleman & Bell Norwood, OH. Fansteel N. Chicago, IL. Fisher Scientific Fairlawn, NJ. 20 General Synthetic and X-Ray Equipment The purity of the reagents and the laboratory equipment are essential parts of a successful synthetic experiment. In this section, the following laboratory equipment will be shown: Figure 5: Three types of glassware designed for synthesis experiments. Figure 6: Vacuum apparatus used for synthetic methods. Figure 7: Induction generator. Figure 8: Synthetic equipment used for melt experiments. Figure 9: Glass boat for melt experiments. Figure 10: Guinier X-ray diffraction instrumentation. 21 was» ems—u £45 03.. 3.336 A0 033.. mafia £33 9.5 use?“ 3 can» smflm 233 0:0 mocha As mason—means sewage—chm 5 cos: semi—woman no momma 09:3. .m 0.53m 358. m1: . UN Us UM U 3 V” w .. 353. 2x3 . .mposaoa 05239? new con: 2.59395 .5525 e 2%: p >< ) _...-...J 95:. 3262.00... see b 5.3:... a: eh Figure 7. 23 OpticolTowsr H0 H0 2 H 112 WP” 1FHT llll llll llll llll IIII llll llll llll llll llll llll llll llll llll IIII llll llll A llll BIOKV 8 1"” unr 8I-2am,2so'KHe-r.t o IIII llll o O llll llll 0 g IIII mu 8 O NH llll 8 0 I'll iii' 0 o IIII Ill! 0 8 llll (Ill 8 O :::| llll O I llll O _ O o llll llll O O llll IIII O I.‘.‘.I I."LI Vacuum System Induction generator for synthesis experiments. 24 deco—5.393 :03 new con: asoanwsdm .m 0.53% ) l I I 0 9.3.. 39.55.... 95 5.2.3:. e... eh 25 eases—€093 £05 tons—no.5 was «.5955 3 com: anon mesa so; nob 33> 02m .m ssaumm 26 Jase—3.52.: composer‘s henna sou—:50 no mofiQo / .I. .2 2%: 27 Synthetic Procedures The first synthesis in which the procedure developed by other laboratories was to be modified was that of YbCla. In the literature procedure,1° ytterbium oxide is added to ammonium chloride and zinc chloride in an excess of HCl to yield a matrix of hydrated ytterbium trichloride, NHICI and ZnCla as the initial product. This initial mixture is heated in a beaker to dryness to remove excess water and excess hydrochloric acid. The dried mixture is transferred to a quartz tube, and zinc is then added. The quartz tube was evacuated by a mechanical pump and heated to remove the remaining water and excess ammonium chloride. The system was pressurized to one atmosphere with Na and the temperature was increased so the zinc chloride and zinc became molten. This molten mixture reacted with the solid YbCla to produce YbClz. Heating at a lower temperature removed excess ammonium chloride and at a higher temperature removed excess zinc and zinc chloride. This procedure takes about one week. In synthesis number one at MSU, 16.0g (0.12 mole) of ZnCl: was added to a two bulb Pyrex tube (see Figure 5b) and placed in a horizontal tubular furnace. This Pyrex tube was evacuated by a mechanical pump (see Figure 6) and heated at 340°C until the ZnCla melted. By opening the oven, the tube was cooled and later was sealed by a methane/oxygen torch. This sealed tube was placed in another tubular furnace and heated to 450°C for an overnight period to separate any non—volatile (ZnO) impurity. The next morning, 1.5 cm of the tube was pulled out of the furnace. After the ZnClz has condensed in the top of the bulb, the tube was cooled and partially cracked by a file mark touched by the methane/oxygen torch. It was immediately placed 28 in the glove-box. Next, an empty quartz tube (see Figure 5c) was heated under vacuum for two hours at 700°C and cooled. A piece of Parafilm was placed on the tube opening and the tube was immediately put in the glove box. Eight g (0.059 mole) of purified ZnCl: were added to 2.5 g (0.014 mole) of Yb in the quartz tube in the glove box (060b/84). Parafilm was then placed on the top of the quartz tube, and the tube removed from the glove box. This tube was placed on a vacuum line, evacuated and sealed with a torch. The tube was heated in a furnace at a 45° angle at 550°C for a three day period. The upper part of the tube was gradually pulled out, 1.5 cm at a time until all the ZnCh and Zn had condensed in this cooler region. The tube was cooled, scratched with a file and placed in the glove-box. The product (YbCh?) in the lower bulb was placed in a bottle and stored in the glove-box. The presumed equation for the reaction is: Yb(s) + ZnCla(1) -’ YbClz(s) + Zn(g) In a second attempt, 10 g (0.073 mole) of ZnClz was placed in a two bulb Pyrex tube and heated at 340°C in a tubular furnace for one half an hour. Then, the oven was opened and the tube cooled. The tube was sealed, scratched with a file and placed immediately in the glove-box. An empty quartz tube was heated at 1000°C in an oven for 3 h while under vacuum. The tube was cooled under vacuum, and parafilm was placed on the top of the tube. Immediately, the tube was placed in the glove-box. In the glove—box, 3.30 g (0.024 mole) of purified ZnCh and 2.0 g (0.012 mole) of Yb were added to the quartz tube (068b/84). This tube was placed on a vacuum line, sealed and heated in a tubular furnace overnight at 550°C. Again, the upper part of the tube was 29 pulled out of the furnace 1.5 cm at a time to effect separation of the Zn and ZnCh. The X.R.D. pattern from this synthesis (060b/84) indicated YbCl: was not pure so an attempt was made to remove the Zn and ZnCh impurity. In the glove-box, the YbCl: complex (075b/84) was placed in a 5.5 cm by 1.8 cm by 0.7 cm pyrolytic graphite boat which was put in a larger glass boat for stability (see Figure 9). These boats were put in a glass tube with a stopcock and a removable top (see Figure 8). This apparatus was connected to a 66 cm by 2.5 cm cylindrical quartz tube which was connected to a vacuum system. Both boats were transferred to the middle of the cylindrical quartz tube and heated to 540°C for 15 min. Excess Zn and ZnCla distilled to the colder ends of the quartz tube. Due to the low two g yield in all previous synthetic preparations of YbClz, a new synthetic route was tried. This is the proposed equation of the two step reaction: 1. 2Yb(s) + 3HgClz(l) + 2YbCla(s) + 3Hg(g) 2. Yb(s) + 2YbCls(l) -> 3YbClz(s) In step one, 4 g (0.023 mole) of Yb and 40 g (0.15 mole) of HgClz (085b/85) were added to a Pyrex two bulb tube. This tube was placed on a vacuum line, sealed and heated in a tubular furnace for three days at 360°C. Next, 1.1 g (0.0064 mole) of Yb and 3.85 g (0.014 mole) of YbCh were added in the glove-box to a 7.6 cm by 0.5 cm tantalum tube (089b/85). The open end of the tantalum tube was crimped shut in the glove-box and both ends were welded under argon or helium. This 30 welded tube was suspended in the coil region of the induction heating assembly (see Figure 7) and heated at 1000°C for 15 min. The second synthesis tried was the preparation of YbBrz. Two g (0.012 mole) of Yb and 12 g (0.053 mole) of ZnBrz were added in the glove-box to a previously heated quartz tube (058a/84). Parafilm was placed on the open top of the quartz tube as a barrier to oxygen and water from the air. Then, the quartz tube was connected vertically to a vacuum line. The tube was evacuated by a mechanical pump and after ten minutes, the system was pressurized with argon to ~130 torr. The tube was heated with a vertical tubular furnace to 200°C. The temperature of the oven was increased very gradually over a one-day period to 340°C. Then, the sample was heated overnight at 340°C. The sample was cooled and evacuated with a mercury diffusion pump. The temperature was set at 380°C and increased to 500°C over the course of one day. The sample was heated for one week at 500°C to remove excess Zn and ZnBrz. Then, the quartz tube was cooled and removed to the glove-box. The product was purified further by transferring it to another quartz tube. (Note: all empty quartz tubes were heated for 2 hours at 700°C while under high vacuum.) This tube was sealed under vacuum and heated to 650°C to remove any remaining Zn and ZnBra by sublimation to the cooler and of the tube. The presumed equation is shown below: 1. Yb(s) + ZnBra(l) +YbBr2(s) + Zn(g) In the second synthesis (064b/84), the same masses of Yb and ZnBrz were placed in a two bulb quartz tube. The tube was sealed and put in a tubular furnace which was heated at 400°C for one day. This 31 sample was placed in a large tubular furnace. The lower bulb was heated at 420°C and the upper bulb at 394°C in order to separate the Zn and ZnBra into the upper bulb. Within one day, the temperature of the lower bulb was increased to 500°C and that of the upper bulb to 430°C. In the next synthetic attempt, 5.2 g (0.23 mole) of ZnBr: and 2 g (0.012 mole) of Yb were placed in a quartz tube which was evacuated and sealed (068a/84). Then, the quartz tube was heated overnight in a tubular furnace at 550°C. The upper end of the tube was pulled out of the furnace 1.5 cm to separate the Zn which was produced by the reaction. The tube was reheated at a 45° angle at 550°C to remelt the Zn in the upper bulb and allow it to mix with the YbBra product in the lower part of the tube. The following equations are suggested: 1. 2Yb(s) + 3ZnBrz(l) -' 2YbBr3(s) + 3Zn(g) 2. 2YbBrs(l) + 3Zn(l) +2YbBra(s) + ZnBr:(l) + 22n(g) Then, the tube was heated at 550°C for one day. The temperature was increased to 580°C to remove the Zn and ZnBr: and the upper end of the bulb was pulled out of the furnace 1.5 cm at a time to effect separation of the volatile substances by condensation in the upper part of the bulb. The next YbBrz synthetic attempt was addition of 2 g (0.012 mole) of Yb and 5.2 g (0.023 mole) of ZnBr: to a 3.5 cm by 1.5 cm cylindrical Ultra Carbon brand non-pyrolytic graphite crucible which was placed in a quartz tube (070b/84). The empty graphite crucible and the quartz tube had been heated to 800°C for 2 hours. The crucible was placed in a quartz tube and heated in the vertical tube furnace at 550°C for one day under 2:130 torr argon. The quartz tube was then cooled and later 32 evacuated with the mechanical pump. The temperature was raised over one day to 580°C to remove the Zn and ZnBra. For the next synthetic attempt, 2 g (0.012 mole) of Yb and 5.4 g (0.024 mole) ZnBra were added to a quartz tube which had been heated empty for 3 hours at 1000°C (073a/84). The quartz tube was evacuated, sealed and heated in a tubular furnace at 550°C for two days. Then, the temperature was set to 540°C and the upper part of the tube was pulled 1.5 cm out of furnace to separate the Zn and ZnBr: by condensation. The product of this reaction was purified by the same technique as that used in the YbCh synthesis (090a/85). The tubular furnace was preheated to 650°C and set on a 10°C per minute scan rate with a linear temperature programmer. The graphite boat with the sample and the heating tube assembly (see Figure 8) was placed in the heated oven with a dry ice cooled trap arranged to condense any halogen gases that might be evolved. The oven was heated to 780°C and cooled quickly. The next YbBr: synthesis was tried in a Pyrex tube by adding 1.98 g (0.11 mole) of Yb and 5.35 g (0.024 mole) of ZnBra (076b/84). The tube was evacuated, sealed and heated in a tubular furnace for one day at 400°C. The product was placed in a pyrolytic graphite boat and placed in the heating tube assembly (see Figure 8). The oven was preheated to 540°C and the product was placed in the oven for 10 min to remove the Zn and ZnBrz. The product was further purified by heating it a second time at 780°C. The next synthetic attempt was the preparation of YbBra. YbBr: was reduced by Yb to YbBra. In a Pyrex tube, 2.5 g (0.014) Yb was added to 32.15 g (0.089 mole) of HgBrz (076a/84). This tube was 33 evacuated, sealed and heated in a tubular furnace at 260°C for three days. Then, the upper end of the bulb was pulled out of the furnace 1.5 cm to condense Hg, HgBr: and ngBrz. To a 7.6 cm by 0.5 cm tantalum tube, 5.53 g (0.013 mole) of YbBra was added to 1.22 g (0.0071 mole) of Yb (079b/84). The same procedure as that used for the YbCla synthesis was followed except that the product was heated in the induction heating assembly (see Figure 7) for 15 min at 1040°C. Later, the product was purified of excess Yb by placing it in a 16.0 cm by 2.5 cm by 1.0 cm pyrolytic graphite boat and heating the boat under high vacuum at 650°C (see Figure 8) (083b and 088a/84). Then, the linear temperature programmer was turned on at a 10°C per minute scan rate and stopped at 750°C. The oven was opened and the product was allowed to cool under vacuum. The following equations are suggested: 1. 2Yb(s) + 3HgBrz(l) 4 2YbBra(s) + 3Hg(g) 2. Yb(s) + 2YbBra(l) -° 3YbBr2(s) Another synthesis in tantalum was tried with 3.173 g (0.0077 mole) of YbBra and 0.68 g (0.0039 mole) of Yb. The induction heating assembly was heated to 960°C for 15 min (12/85). Finally, the last synthetic route attempted was the preparation of Ybla. In a Pyrex tube 2.5 g (0.014 mole) of Yb was added to 27 g (0.059 mole) of HgIa in air (053b/84). The tube was evacuated, sealed and placed in a tubular furnace at 285°C for three days. Then, the upper part of the bulb was pulled out of the furnace 1.5 cm until all Hg, nglz, and HgIa had condensed. The cooled Pyrex tube was scratched with a file and transferred quickly into the glove-box. The following equation is suggested: 34 1. Yb(s) + HgIa(l) +YbI:(8) + 118(8) A11 percent yields were calculated by the following formula: X yield = a/b -/- c/d x 100 a = actual weight of Ysz(g) b = molecular weight per mole of YbX2(g/mole) c = actual weight of Yb(g) d = atomic weight per mole of Yb(g/mole). Procedures for Melt Experiments In the glove—box appropriate molar quantities of Ysz-YbXa’ were weighed in 1 g or less quantities. (Note that X and X’ represent different halogen atoms.) The two components were ground intimately together in an agate mortar with a pestle to insure homogeneity. The entire sample was placed in a 5.5 cm by 1.8 cm by 0.7 cm pyrolytic graphite boat which was then placed in a large alundum or glass boat (see Figure 9). The apparatus was transferred to a vacuum heating assembly by using a transfer tube with a stopcock and a connecting top (see Figure 8). All glass connections were sealed with an Apiezon grease. The vacuum heating assembly was evacuated immediately after insertion of the transfer tube. Both boats were transferred to the middle of the 66 cm x 2.5 cm cylindrical quartz tube. The entire heating assembly was subjected to the high vacuum of the mercury diffusion pump. The mixture was heated by a tubular furnace so the temperature exceeded the melting point of at least one of the YbX: components (see Tables 2, 3, and 4 for actual temperatures and conditions). 3S .meme oxmsmsz. .eEou aecmw on .anu queues“ seem .:ME\UomN mo one» snow ”ouoz oz can -- mem.o cae.o em-phxe me a «max owe ~cn.o men.o mw-nsmo me H can owe ow~.o HNm.e mw-mmwc co oe can -- w~m.o eme.o em-noao om ce one one omv.o ems.o mw-aomo we N can one omm.c mm~.o ma-«mmo as N one one cNe.c Nme.e mw-avmo mm m com -- ase.o mem.c ew-mmac mN m sea -- a-.c mc~.c em-nwao ON nae m u.cee moose w oom.o w ch.o mw-n~wc o2 .aaoe emcee .esoe .esoe in» so can» so topssz Neon» as «see emcee Hmeue=_ sauce: beans: A sea: .mucoeweoexm was: -c>--ua> how sumo stHseocmg .N oanmh 36 .UomN me: .aaeu “Mac: =o>o seem eo>oaoe so: mafia: .~ .aaeu Macaw ou .asou Hewufisw seem .:ME\Uom~ mo sums seem .a "ouoz ~ one one me.o ms~.o mm- vmc cc m own ewe m~o.o emm.e mm-n~mc ma m amp cue emc.c ~ce.c mm-emmc mm m one ewe NcH.c Hae.o mm-nomo mm m emu cmo ~c~.c Hm~.o ma-cnwc mo ~ own one ~m~.c ~m~.c mm-smwc mm N emu owe ccm.o ~cv.o mm-mcmc om sea H Uoomn vocab m ~om.o m cm~.c mw-mnwc mm mace .aaoe .QEQP Neon» so ~umn» mo tuaaaz -mn> Hazel Heaueae sauna: cameo: « mac: .mucosweoaxm was: ~Huc>-~emc> how mama xeoumuocmq .m oases 37 .man Macaw ou.aaou deepen“ Eoew .:«E\Uom~ mo owes snow "ouoz ON“ cox cas.c ~m¢.o mm-ammc mm ONA cox mee.c mmm.c mm-neme cm can e~a amu.o ase.° ma-~vao me ova ewe ac~.e Hm~.o mm-pemo as can ONA aeN.c me~.c mm-ammo om ova cNB ame.o soH.o mm-mamo me see oNA ~m~.c ~c~.o mm-ahme we owe cNA moe.o coN.c mm-nsao ow sea ems me~.c mce.c mm-neac mm och ONA Ncm.c ecm.o mm-nqme cm Nae ON“ Nae.e ecH.o mm-amae mN ewe o.oma ooomh a ”mm.c u mec.c mm-nmmc we cane .agoe .asoe Nan» so Nuns» so tonasz Nuns» eases Madness Heme»: sauce: 3 ode: .mueoeweoaxm was: Nuc>-~smn> sow seen Acoumaocma .e emcee 38 The two boats containing the melted specimen were moved from the 66 cm x 2.5 cm cylindrical quartz tube to the transfer tube while the apparatus was under vacuum. The system was removed from high vacuum by turning the stopcock of the mercury diffusion pump in an off position. Then, the system was filled with dried argon, and the transfer tube was removed from the line. The tube was capped quickly and transferred to the glove-box. Each melt was weighed and stored in a one ounce bottle. An X.R.D. pattern was taken. All percent recoveries were calculated by the following formula: X recovery = a/b x 100 a final weight of ytterbium mixed halide(g) b initial weight of ytterbium mixed halide(g) Procedures for X-Ray Diffraction Interplanar d-spacings and corresponding sinafl values were obtained from a 100 mm evacuated Guinier-Hagg camera fitted with a quartz monochromator with Cu Km x-ray radiation. Samples were placed on Scotch brand tape affixed to metallic donuts and protected from the atmosphere by a film of paraffin oil dried over metallic sodium. The oil was subsequently covered by a very thin piece of glass which was part of a broken glass bubble. The x-ray photographs were calibrated by an internal standard of elemental silicon (so = 5.43082 i 0.00004» which was obtained from the National Bureau of Standards. Distances between the fiducial mark generated by the direct x-ray beam and the reflections on the photographic film from the Guinier-Hagg camera were determined by a Charles Supper film measuring device modified to permit easier identification of the line position and relative intensities which were estimated visually. Values of d and sin'B were 39 calculated by a linear regression program on a Hewlett Packard calculator with the Si reflections as the standard. The d-spacings were indexed (assigned h,k,l’s) by comparison to literature data or to the output of program ANIFAC" run on the CDC CYBER 750 computer. The program ANIFAC generated the reflection intensities, d-values, sin’fl values and Miller indices, h,k,l, for selected space group from input which consisted of lattice parameter variables (a,b,c,¢,fl,‘r) obtained from the literature or estimated from literature data; atomic position variables of similar compounds which possess the same structure types obtained from the literature, and isotropic thermal parameters. Literature values of isotropic thermal parameters were used when available; when unavailable, they were estimated, with the parameter of the cation typically set at 0.8-1.0 AF and that of the anion 3/2 to 2x this value. Atomic scattering factors were taken with appropriate dispersion correction terms from the "International Tables. "“ Consistent with the geometry of the Guinier camera, absorption terms were not included in the calculations. Lorentz polarization and multiplicity terms were calculated by the program. Lattice parameters were refined and errors calculated by a linear regression program on a Hewlett Packard Series 80 computer. Lattice parameters were calculated for all molar ratios within a given system, and lattice parameters and volume versus composition were plotted. A linear sloping line was considered indicative of a solid solution whereas a line of zero slope was considered indicative of the presence of a new phase. Determination of whether anion site occupancy of mixed halides was random or ordered was effected with the aid of the program 40 ANIFAC. Calculated intensity data for selected reflections were compared with those determined from a Philips diffractometer (Cu Kc radiation). 41 RESULTS “Synthetic The percent yields for syntheses of YbCh, YbCls, YbIz, Yan and YbBra are reported in Tables 5 and 6. Percent recoveries for the ytterbium chloride-iodide, bromide-chloride and bromide-iodide systems are tabulated, respectively, in Tables 7, 8 and 9. In Table 10, the x-ray reflections and their intensities calculated or reported for ytterbium oxide halides are tabulated together with reflections observed in the compounds; YbCh, YbIz and YbBra. These compounds potentially might contain oxide halide impurities. 42 Table 5. Percent Yields of YbClz, YbCls and YbIz 9.992994 11293.1: £139.19! 99.1.93: YbClz b 060b-84 24.9 grey/white YbClz ‘3 068b-84 40. 1 grey/white YbClz b 07la-84 74.7 grey/white YbClz b 075b-85 90.8 grey/white YbClz c 089b-85 a yellow YbCls d 085b-85 90.5 white YbIz ° 053b-84 92.7 green YbIz ° 082a-85 85.3 green YbIz ° 057b-84 96.2 green a. X.R.D. indicated YbCla-YbClz mixture. b. Yb(s) + ZnC12(I) ->YbC12(s) + Zn(g). c. Yb(s) + 2YbCla(]) + 3YbC12(s). d. 2Yb(s) + 3HgClz(1) +2YbCla(s) + 3Hg(g). e. Yb(s) + Hg12(1) +YbI2(s) + Hg(g). 43 Table 6. Percent Yields of YbBrz and YbBra @9929 Numbes i,X.i..91...<_! Color YbBrz c 058a-84 96.5 black/green YbBrz ° 064b-84 55.9 yellow YbBrz C 068a-84 67.7 yellow/green YbBrz C 070b-84 none‘ -—- YbBr2(step 1)c 073a-84 90.8 yellow/grey YbBr2(step 2) 090ar85 70.8 green YbBr2(step 2)c 076b-84 21.0 green/white YbBr2(step l)d 079b-84-E 91.9 red Yb8r2(step 2) 083b-84 noneb black/green YbBr2(step 2) 088a-84 36.9 green YbBr2(step 1)d 091a-84-E 54.6 green YbBr2(step 2) 091a-84 41.7 black YbBrz d 146-10-85 93.9 green YbBrz ‘3 12-85-E 95.6 green YbBra 9 0763-84 97.4 green/white a. YbBrz was absorbed into graphite cylindrical crucible. b. YbBrz adhered to the boat. c. Yb(s) + ZnBr2(l) 4*YbBr2(s) + Zn(g). d. Yb(s) + 2YbBr3(1) 4’3YbBr2(s). e. 2Yb(s) + 3HgBr2(l) e'ZYbBra(s) + BHg(g). 44 Table 7. Percent Recovery - Ytterbium Chloride/Iodide System. Mole x YbClz 10 20 25 35 40 45 50 60 65 75 yumber 081b-85 078b-84 0738284 084a-85 0838-85 0808-85 070b-84 085a-85 081b-85 077b-84 a. No yield reported. b. Melt difficult to remove from boat. §WEESQXEEX 70. 48. 81. 66. 66. 78. 0 4030000 Color of Melt green/black/yellow green/black black/yellow green/black green/black green/black/yellow green/black green/black green/black green/black 45 Table 8. Percent Recovery - Ytterbium Bromide/Chloride System Hole 3 “:8 r2 21.92.1195 5..-.39991952 25 087a-85 84.7 40 054-75 31.2 (book 2) 50 086a-85 37.7 55 089a-85 55.3 65 087b-85 51.0 55 0925-35 75.4 75 086b—85 55.3 35 089a-85 57.9 95 0955-35 71.9 Table 9. Mole X YbBrz 15 25 30 35 4o 42 45 50 so 75 80 85 $9999: 095b-85 0933-85 094b-85 096b—85 096b-85 097b-85 0973-85 093b-85 097b-85 094a-85 096b-85 095a-85 46 5139992953 53. 73. 74. 76. 59. 76. 62. 59. 80. 72. 62. 73. QOCDOO 9 Percent Recovery - Ytterbium Bromide/Iodide System Color of Melt black/yellow black/yellow black/yellow black/yellow black/yellow black/yellow black/yellow black/green black/yellow black/green black/green black/green Table 10. 99589299 X9919 2919 Y9??? 47 A comparison of ytterbium dihalides to respective ytterbium oxide halides in terms of d-spacings and intensities of X.R.D. patterns. 99595229 9919219599 59299: 9 i 9: i 068b-84 9.3088 w. 9.2757 95.4 --- -—- 3.2053 32.0 --- —-- 2.9273 100.0 --— --- 2.3658 39.4 -—- --- 1.8530 33.1 d 1 9? i 053b-84 3.0082 w- 2.953 100 2.7228 w 2.737 55 —-- --- 2.409 25 under Si --- 1.938 40 1.5177 8 1.522 55 1.3786 w 1.372 30 08313-855 9! .‘1. 95. .i. --— ——- 2.80 100 --- --- 2.57 100 1.8922 8 1.89 50 1.553 w 1.57 50 48 329.52. 0545434 4 LI. 515. .i. 2 . 79919 M 2 . 80 100 2.67735 M 2.67 100 d _-.. ___ _... d __.- --- __._ a. Intensity and d spacing from computer progran ANIFAC for YbOCl; 1.p.-ref. 50; a.p.-ref 50. b. Intensity and d spacing - ref. 44; 16-60-Yb0I. c. Intensity and d spacingbref. 44; 12-1465-YbOBr. d. d values not read. X-Ray Diffraction A summary of the SrIa-type orthorhombic lattice parameters for YbCh, YbBrz and the YbClz/YbBr: mixed halide system and respective unit cell volumes are presented in Table 11. A graphic presentation of lattice parameters and unit cell volumes for this system is plotted in Figure 11. Lattice parameters and volumes are given in Table 12 for the hexagonal, CdI: structure type observed for part of the YbCh/YbI: system. Data on another portion of this system indexed as the orthorhombic, SrI: structure type is presented in Table 13. These lattice parameters and the respective unit cell volumes to which they correspond are displayed graphically in Figure 14. In the YbBra/Ybla system, the hexagonal CdIz type structure was found in the 0 and 35 mole percent YbBrz samples. In contrast, the orthorhombic, CaClz structure type which is one of four structure types reported for YbBrz was observed in the 80, 85 and 100 mole percent YbBrz samples. This result is also given in Table 14. Structure types 49 which were considered in an attempt to identify unexplained reflections in YbCh/YbBra system are exhibited in Table 15. Attempts were also made to fit the new phase reflections observed in the YbClz/Ybla system to known structure types. These structure types are listed in Table 16. 50 Table 11. Lattice parameter composition data for the orthohodaic SrIz- type structure, YbClz/YbBrz system. The standard deviation of the least significant digit is indicated in parentheses. Mole X YbBrz a b c volume 0 13.158(6)A 6.960(3)A 6.708(3)A 614.18A 3 25 13.316(8) 7.045(5) 6.759(8) 634.07 40 13.52(l) 7.116(5) 6.809(4) 654.41 55 l3.547(9) 7.178(5) 6.882(5) 669.16 65 l3.579(9) 7.213(5) 6.944(6) 679.94 75 13.630(9) 7.255(4) 6.998(5) 691.85 85 l3.7l(1) 7.330(7) 7.063(5) 709.59 95 13.764(7) 7.336(5) 7.073(4) 714.08 100 l3.80(l) 7.359(4) 7.093(4) 720.12 .somzmonaoo «o cameos—am a as 639? Aon>\€mn> 05 5 vo>somno oEEo> Sl :00 3:: 05. 9.308933 03.53 owns—03.3.3.3 0.3 no sea < ‘P .: 959.3 «can» :32}. so: 8 8 ON 0 . .. ‘ i. O o 0.0 {l (l ‘5 0 {v y. °< 52 Table 12. Lattice parameter composition data for the hexagonal CdIz- type structure, YbClz/YbIz system. The standard deviation of the least significant digit is given in parentheses. Mole X YbClz a c Volume 0 4.508(3)A 6.978(3)A 122.74? 10 4.485(6) 6.967(9) 121.37 20 4.451(5) 6.955(7) 119.27 25 4.442(5) 6.949(8) 118.73 35 4.450(6) 6.953(8) 119.17 40 4.451(6) 6.957(9) 119.29 45 4.450(7) 6.95(l) 119.14 50 4.46(3) 6.96(4) 119.73 53 Table 13. Lattice parameter composition data for the orthorhoduic SrIz-type structure, YbClz/YbIz systu. The standard deviation of the least significant digit is given in parentheses. Mole X YbClz a b c Volume 100 13.158(6)A 6.960(3)A 6.708(3)A 614.1853 75 l3.l75(5) 6.956(3) 6.702(4) 614.07 65 13.182(8) 6.960(4) 6.711(6) 615.57 60 13.18(2) 6.955(7) 6.71(1) 613.70 50 l3.ll(4) 6.94(2) 6.68(2) 606.86 .Esmhm .Hn>\«~on> one 5 vo>aomno 0330> :oo 3:: 23 new? sonaomg Jason—mama 005.3— Ecomaos was 033920420 «0 .33 < .2 93.3% .3 a» 2853 as: S4 55 Table 14. Lattice parameter composition data for the hexagonal CdIz- type structure and orthorhodfic CaClz type structure, YbBrz/YbIz system. The standard deviation of the least significant digit is given in parentheses. Mole X YbBrz a b c Volume 0 4.508(3) A ~—-— 6.978(3)A 122.74A 3 35 4.457(5) --- 6.901(7) 118.72 80 6.708(4) 7.019(5)A 4.408(2) 207.54 85 6.680(4) 7.001(5) 4.401(3) 205.82 100 6.6320 6.9320 4.3720 200.99 56 Table 15. Structure types examined in an attempt to index unexplained reflections in the YbBrz/YbClz system. 1. Rutile3° 2. CaClz 30'15 3. aerOz 3° 4. YbOBr 4‘ 5. YbOCl 5° 57 Table 16. Structure types examined in an attempt to assign reflections of the new phase observed in the YbClz/Yblz system. 1. CaClz 15'3° 2. s-Pb02 3° 3. PbClz - high pressure form 5° 4. PbClz ‘2 5. CdClz 5° 6. Rutile 30,53 7. YbOBr 4‘ 8. PbClF“ 9. SrIz 17"3 10. YbOI “ ll. YbOCl 5° 12. SrIz (II)°° l3. CdIz ‘7'54 l4. BiSI 5° 58 DISCUSSION «use-wwumsmom In any synthesis, obstacles that inhibit progress appear. Following is a summary of the problems encountered in this work: 1. YbClz synthesis method 1: removal of Zn and ZnClz. 2. YbClz synthesis method 2: formation of a YbCla-YbClz-TaCIx mixture. 3. YbIz synthesis: Possible formation of YbIz hydrate. 4. YbBrz synthesis method 1: YbOBr impurity, and a complex X.R.D. pattern due to four known temperature dependent structure types for YbBrz. 5. YbBrz synthesis method 2: formation of a YbBra-YbBrz-TaBrx mixture. 6. Mixed halide systems: low recoveries. All six problems will be discussed in this section. The first five problems are concerned with impurities in ytterbium dihalide syntheses. All impurities had to be removed before these materials could be used as reactants for the mixed halide studies. Problem six deals with the mixed halide systems. In the YbClz synthesis by method one [Yb(s) + ZnClz(l) -’ YbCh(s) + Zn(g)], Zn and excess ZnCl: proved difficult to separate at 550°C from YbClz by the method of choice, sublimation. The vapor pressures of the individual components are a key factor in the sublimation process, and are: ZnCh - 40 torr“ at 566°C, Zn - 10 torr“ at 593°C and YbClz - 2.6 x 10" torr” at 550°C. Since the sublimation Occurred at a temperature of 550°C, the Zn and ZnClx should have been 59 removed easily from the desired YbCl: product based on vapor pressure factors. X—ray diffraction results showed YbClz and other unidentified compounds to be present in the lower part of the quartz bulb (060b/84). The upper bulb contained both a brown solid (YbCh and other unidentified compounds), and a white solid (no YbClz, but other unidentified compounds). Raoult’s law considerations can provide an explanation for the presence of unidentified compounds, probably Zn and ZnCl: in the lower bulb. In this case, an ideal solution of Zn, ZnCh and YbCl: is assumed. The law states that the total vapor pressure is the sum of the vapor pressures of each individual component. As such, Pm» = P21: + Puma + Pncu, where P2. = XzaP°u (P:- = vapor pressure of pure Zn, Xx- : mole fraction of Zn, etc.). As the number of moles of zinc approaches zero, the absolute vapor pressure of zinc in the lower bulb approaches that of YbCla and zinc ceases to be transported from the lower to the upper bulb at a reasonable rate. The same argument holds for transport of ZnClz. Therefore, some amount of all three reactants, Zn, ZnCl: and YbClz is contained in the lower bulb. The reaction time for the next YbCla synthesis (068b-84) was reduced from three days to overnight to accelerate the overall synthetic procedure. The sublimation time for removal of Zn and ZnCl: was reduced from three days to one day in an attempt to minimize transport of YbCla to the upper bulb. X-ray diffraction data indicated the presence of YbClz in lower bulb, but the yield was low (40.1%). This lower yield is apparently due to transport of YbClz to the upper bulb and adhesion of YbClz to walls of quartz tube. Apparently, the YbCl: 60 was transported into the upper bulb along with Zn and ZnClz. This is due to the high transport rate of Zn and ZnClz caused by experimental conditions. This hypothesis is given more validity by the results in the next synthesis in which a larger surface area graphite boat cleanly separated Zn and ZnCh from YbClz. In the YbCl: synthesis (07la/84), sublimation time was reduced further to one hour, and the Zn complex was only partially removed. Complete removal of the ZnCl: and Zn was completed in ten minutes at a temperature of 540°C. The sample was placed in a medium sized graphite boat and placed in a vacuum heating assembly (see Figure 8). A 90.8% yield was achieved on the last YbClz synthetic attempt (075b- 84). The products of YbCh synthesis (089b/85) by method two, [Yb(s) + 2YbCla(l) -* 3YbClz(s)], were analyzed by X.R.D. and found to be a YbCla—YbCla-TaClx mixture. A possible explanation is reaction between YbCl: and the tantalum tube. This reaction apparently produced a TaClx compound which expanded the tantalum tube. This expansion was undoubtedly due to the fact that TaCls can only exist as a gas“ at 1000°C. In a thesis written by one of Baernighausen’s students,” TaBrs and TaBru were confirmed by chemical tests to be present in the reaction product formed between YbBra and a tantalum container. The following equation is suggested for formation of the YbCla-YbClz- TaClx mixture: 1. Ta + YbCla -’ TaClx + YbCla Yb metal was also found in the tantalum tube which might suggest the following equation: 2. Ta + YbCl: 7' TaClx + Yb(s) 61 Alternately, since the YbCla and Yb were mixed in the stoichiometric ratio required to produce YbCh, any YbCla that reacted with Ta would of necessity require that Yb metal remain in the reaction tube. This latter explanation (equation 1) seems thermodynamically more feasible than equation 2. No YbOCl was found in any YbCla preparation (see Table 10). In the YbIz synthesis, the yields were high due to the high vapor pressure of the following reagents: HgI: - 100 torr“ at 261.8°C; and Hg - 100 torr“ at 261.7°C. Another possible product, nglz decomposes at 357°C. The vapor pressure of YbI: is 1.9 x 10‘“ torr" at a temperature of 260°C which was calculated from a AH° of Eulz, and vapor pressure of YbI: of 2 torr at 790°C.“ These large vapor pressure differences allowed a clean separation of YbIa from Hg and HgI: by the sublimation process and according to LeChatelier’s principle, forced the reaction to completion. Consequently, all the YbIa synthesis yields were high. The less than 100% yield observed could be the result of two causes: (1) the transport of YbIa to the upper bulb as mentioned in YbCl: synthesis discussion, and (2) incomplete reaction if the metal particles were too large to have reacted completely with HgIz before the end of the tube was pulled from the furnace and the HgIz removed. The major problem with the YbIz synthesis was the presence of unexplained reflections in the X.R.D. pattern. The following approaches were taken to identify the unexplained reflections: (1) YbIz is know to exhibit the CdIz structure type which forms polytypes“ in which the cell dimensions vary only in the direction perpendicular to the stacked layers. To approximate polytype 411 by computer, the a11 lattice parameter calculated from the X.R.D. pattern of an M80 synthetic preparation of YbIz was combined with the doubled c lattice parameter of the same material. Interplanar d- spacings generated by the computer from these parameters did 62 not match the unexplained reflections in X.R.D. pattern of the MSU preparation of YbIz. The polytype 611 was also approximated by computer by tripling the c lattice parameter. This computer calculation of interplanar d- values was not the solution either. On the assumption that the reflections were superstructure reflections of the parent cell, an attempt was made to fit them by the method of ITO!"8 to a new larger cell. They could not be fit. (2) Potential impurities were checked by comparison of observed d values with those from the ASTM Powder Diffraction File.“ Reflections for the following compounds did not match the unexplained reflections: a) YbOI b) HgIz c) Yb d) H8212 e)H8 A possible solution was found when an X.R.D. pattern of a 50 mole percent YbCh-50 mole percent Yblz sample, which had been confined in the glove-box for many months, was examined. The YbIa reflections found in the original 50/50 YbClz-YbIz X.R.D. film were absent in the rerun and the unexplained reflections were more intense. It is possible that the YbI: in the 50/50 YbClz-Yblz rerun could have formed a hydrate or could have oxidized. However, no YbOI was present in the 50/50 YbIz-YbClz rerun. Therefore, it was assumed that the reflections belong to a Yblrhydrate, and this assumption was pursued by experimental methods. In the glove-box, 0.1 g of YbIz was weighed into a 2 ml reacti-vial. The top was sealed with a Teflon' septum and capped. The vial was removed from the glove—box and 5 microliter of deionized water was injected by a 10 microliter syringe. Then, the vial was placed in the glove-box and an X.R.D. pattern taken. The observed d values of this X.R.D. pattern called the YbIa-hydrate were identical to 63 those of the unexplained reflections of the 50/50 YbCla-YbIz rerun. No Ybe was present in Yblx-hydrate or the 50/50 YbCh/YbI: rerun. Ytterbium iodide hydrate compounds have not been reported, so no d values against which to make comparisons are available in the literature. No YbOI was found in any YbI: product (see Table 10). In Table 10, the first two observed reflections in YbI: (053b-84) were confirmed to be Yblz'flle): and the last two d reflections are identified as YbIa. Even though the reflections observed in the YbIa product (053b-84) matched the theoretical YbOI d values, the intensities of these reflections do not match calculated values. Therefore, YbOI is not present. A major problem with YbBr: synthesis method 1, [Yb(s) + ZnBr2(l) + YbBra(s) + Zn(g)], was a YbOBr impurity (see Table 10-064b/84). The following steps were followed in an effort to eliminate YbOBr formation: (1) The quartz tube was evacuated with a Hg diffusion pump (10"5 torr) versus a mechanical pump (10‘3 torr) before the tube was sealed to remove 1120 vapor. ( 2) The quartz tube was heated to 1000°C under vacuum for 3 hours to fuse all open silanol sites and remove water present in the tube. (3) Yb and ZnBrz were mixed in an argon filled glove-box fitted with a purification train which contained molecular sieves to remove 820 and BASF catalyst to remove oxygen from the argon. Solid P205 was placed inside of the glove-box to further reduce the residual 1120 partial pressure. (4) The quartz tube was cooled under vacuum after being heated to 1000°C for 3 hours. The tube was removed frem the vacuum line with argon and Parafilm was immediately placed on the end. Then, the tube was placed in the glove-box with the Yb and ZnBrz reactants. Possible reasons for YbOBr presence: (1) Reaction of YbBrz with the quartz tube. Schafer"9 reported reaction of AlzCls with a quartz tube at 300°C to produce AlOCl. At more elevated temperatures, A1203 is formed. A low temperature (400°C) preparation of YbBrz by use of a Pyrex tube instead of a quartz tube was attempted at MSU. 64 Yb and ZnBrz were added to the tube in the glove-box and the tube was sealed under vacuum. YbOBr was found by X.R.D. (2) Any attempt at M.S.U. to produce SmIz showed that oxygen was present in the glove-box. A new BASF catalyst apparatus was prepared to remove oxygen from both the glove-box and the attached trap. A Na-K alloy was placed in the glove-box to remove the residual oxygen and water vapor. YbBrz could be more subject to hydrolysis or oxidation than the Yblz or YbClz samples. Huheey” points out a number of unusual characteristics of those main group elements, in this case, bromine, which follow the first complete 3d block. In the YbClz/YbIz system, an alundum boat was used successfully to contain the samples during heating without oxidation. However, in the YbBrz/YbClz system, an alundum boat was used and a YbOBr impurity resulted. (3) It was reported that water desorbed from the walls of a heated quartz tube.” This desorption occurred when the tube was sealed by a torch at temperatures in excess of 1000°C. Desorbed water could have hydrolyzed the YbBr: and produced YbOBr. All samples prepared by method one (Yb + ZnBra + YbBrz) contained YbOBr. Samples synthesized by method two, (Yb + 2YbBr3 '° 3YbBr2) did not show the presence of YbOBr (Table 10-083b/85). This observation is interpreted to mean that the source of oxygen is not the glove-box, but is either the quartz tube or moisture (oxygen) generated when the quartz tube was sealed off with a torch. Confirmation that YbBrz had indeed been prepared was difficult until a dissertation of one of Dr. Baernighausen’s students”, Dr. Bossert, was received. In this dissertation, four temperature dependent structure-types for YbBrz are reported. Bossert used the high temperature Guinier X.R.D. technique to identify the four structure types. The equation suggested for their YbBrz synthesis was: 727°C-827°Cl YbBra (Ta container) YbBra(s) + TaBr5(g) + TaBru(s) 65 An important fact observed during Bossert’s synthetic procedure was the presence of TaBrs and TaBru. An open tantalum crucible was filled with Yan and placed in an evacuated quartz tube. In the upper part of the quartz tube, an orange-red solid was found which was identified as TaBrs. A darker solid was found closer to the Yan sample. This solid was amorphous by X.R.D. and by chemical means was found to be TaBru. The YbBra synthesized by Bossert was placed in the X.R.D. instrument and heated to 500°C. X-ray diffraction photographic films were taken at the following temperatures with the suggested structure types indicated: SrIa-207°C; s—Pb02-267°C; Cams-447°C and rutile-477°C. Samples of YbBra were prepared at MSU by the following methods: 1. Yb(s) + ZnBra(l) 3“ °° Yb8r2(s) + Zn(g) ————o 2. Yb(s) + 2YbBra(l) fl3YbBrds) All X.R.D. patterns of samples prepared by synthetic method 1 (Table 6) were the same as that of YbBra listed in appendix 6. These YbBrz samples were a mixture of CaCh and SH: structure types. Neither s-PbO: nor rutile type YbBr: phases were found in samples prepared by method 1. By synthetic method 2, all X.R.D. patterns from samples (Table 6) showed X.R.D. patterns as seen in Appendices 3 and 5. Method two was a high temperature (960°C) preparation so the high temperature forms of YbBra, CaCh and rutile were expected. Samples 146—10-85 and 12-85 prepared by method 2 showed the SrIx structure. Whereas, 091a-85 and 079b-84 also prepared by method 2, showed a Cam: and SrIa structure. A rationalization for presence of 66 only two structure types of YbBr: from the four known is found in x- ray diffraction discussion section. In the first YbBra preparation by method two (079b/84), the reaction took place at 1040°C for a 15 minute time period in a tantalum container. A red solid was produced and in addition, the tantanlum container expanded. This expansion may be due to formation of TaBrx compounds. Bossert’o found that TaBrs and TaBru were formed by the reaction of YbBra with tantalum in an open evacuated container at 727°C. TaBrx compounds have similar physical properties to TaClx. Since the boiling point“ of TaCls is 233.9°C, the compound is gaseous at 1040°C. Therefore, it is likely that TaBra is gaseous at 1040°C. Expansion of the sealed tantalum container is thus very predictable. Synthesis of YbBra by method two at a temperature of 960°C (091a/84, 12/85) yielded only a green solid so no TaBrs was present and the tantalum tube did not expand. Some of the above facts are summarized below: 1. No tantalum-YbBra reaction at 960°C. 2. A temperature difference between the tantalum-YbBrz reaction at MSU (1040°C) versus tantalum-YbBra reaction of Bossert (727°C). These results are probably due to the rate of heating. The YbBrz preparation at 960°C was heated at a very slow rate. The YbBra reacted with Yb at a temperature far below 960°C and YbBrz, once formed, does not react with tantalum. A faster rate of heating pursued for the 1040°C preparation caused YbBr: to react with the hot tantalum before it could react with Yb. The faster heating rate led to the formation of TaBrs. 67 The low recoveries in some of the mixed halide systems were due to the adhesion of melt or powder to the graphite boat. Reaction with the graphite boats, all of which had a very smooth surface, was not observed. 68 DISCUSSION X-Ray Diffraction YbBra-YbCh System. The standard deviations of the lattice parameters derived from the least-squares fit of the Srla-type Miller indices to the observed reflections were consistently less than 20.00911 for the Yan/YbCh system (see Table 11). Such a good fit is considered evidence that the SrIz-type structure or some closely related modification thereof prevailed throughout the system. The presence of only the SrI: structure-type was unexpected since YbBr: synthetic preparations had yielded the CaCla and SrI: structure-types. Thus, a rationalization for the presence of only the SrIa structure-type in this system is necessary. The SrI: structure-type is the only reported structural form for YbClz.“ In contrast, four know temperature dependent structure- types” are reported for YbBrz. The highest temperature structural form is reported to be that of rutile (477°C), then at progressively lower temperatures the 051013, s-PbO: and the lowest temperature form, SrIa. Therefore, one reason that the SrI: structure-type might be favored is because it is the only structure-type common to both YbCh and YbBrz. Mixed chloride-bromide phases then, would be expected to exhibit the common SrI: structure-type. In addition, a rationalization for the presence of only two of the four known structure-types will be necessary to explain . the YbBrz synthetic preparations. Such an explanation will be attempted here. Both the YbBr2/YbClz mixtures heated at 750°C, as expected, and the YbBr: preparations in tantalum 69 heated to 960°C for 15 minutes (146-10-85, 12-85) were found to exhibit only the Srh structure-type. Other YbBr: preparations heated in tantalum to 1040°C for 15 min (079b/84; 091a/85) and to 550°C in quartz for 3 days exhibited both SrIa and CaCla structure-types. According to the data of Bossert, YbBra, on cooling, transforms from the CaCh structure to the s-PbO: structure-type at 477°C, and from the s—PbO: structure-type to the SrI: structure-type at 100°C.“ Thus if a preparation were cooled too quickly for equilibrium to be established, the resultant mixture would be expected to be that of the s-PbO: and the Srla-types, not the 013013 and SrIs-types. Some phenomenon other than thermodynamic equilibrium must be stabilizing the CaCh-type structure. As stated previously, the CaCh structure-type was observed in samples that had been heated for either extended time periods or at the highest temperature. A possible explanation might be the presence of an impurity phase. A tantalum impurity might have been introduced in the highest temperature preparation. Whereas, a silicon impurity may have been introduced in the low temperature preparation. However, such impurities would most likely have been less than 1 or 2 percent which is below the x-ray diffraction detection limit. These trace impurities in the YbBr: end product could have stabilized the 013013 structure-type. An alternative explanation for the presence of only two structure- types can be developed in terms of the Yb-Br crystal radii, coordination number of cation and anion, and geometry of anion coordination. Data relative to the four structure-types of Yan are summarized in Table 17. 70 Table 17. Average Yb-Br interatomic distances, coordination number of anion and cation, and geometry of bromide anions of the four structure-types for YbBrz. Anion Coordination Coordination Structure-Type d(Yb-Br)3°(£0 Number Geometry Cation Anion SrIz 3.008 7 3 trigonal 7 4 tetrahedral 08012 2.913 6 3 trigonal ser02 2.920 6 3 trigonal rutile 2.924 6 3 trigonal 71 Unfortunately, an ionic radius for three-coordinated bromide ions is not available, but it is safe to assume the radius is constant in all three—coordinated structure-types. From the Yb-Br interatomic distances listed in Table 17, the three high temperatures forms (rutile, CaCh, ¢-Pb02) are seen to have essentially identical interatomic distances with the low temperature form (SrIs) to have a slightly larger interatomic distance consistent with the higher coordination number. Thus of the four possible structure-types, three are almost identical; one is different. A slight kinetic stability edge must be present for the CaCls-type structure. This kinetic barrier could be shallow enough that under equilibrium conditions, the CaCh-type structure reverses to the e-Pb03-type structure, and then to the SrIs-type structure. But in a typical heating experiment where samples were quenched, the CaCh-type structure could not transform quickly enough. A third explanation may be deduced from the laboratory observations and literature sources. In the laboratory when a slight excess of Yb metal was added to the tantalum tube (equation - Yb 4- 2YbBra + 3YbBr2), the Srls-type YbBr: products were found to be a solidified green melt with some black product on top. This apparently less-dense black material could be a Yb” cation rich product. The black color could result from electrons being trapped in anion sites. For YbCh, only the SrIa-type structure is stable over the entire solid temperature range; whereas for YbBr: the same structure-type is stable over a very limited low temperature range. It can be inferred that the Srla-type structure is more stable as the ratio: radius cation/radius anion increases, i.e. rYb"/rCl" = rYb"/ 1.811 vs. rYb’VrBr’ = rYb3*/2.2A (The truthfulness of this hypothesis can be 72 verified by examining the TmBr: phase diagram, in which rTm'VrBr' is larger than rYb“/rBr'.)’° If an electron is substituted for the bromide ion in some of the anion sites, a feet which could happen if excess Yb dissolved in the molten YbBra and the melt was cooled quickly, the average anion size would be decreased, so therefore the Pasties/testes ratio would increase. Then SrIa-type structure would become more chloride-like and more stable. On the other hand, if Yb“ is present as an impurity in the structure, the structure could accommodate the charge imbalance by leaving one Yb" cation site vacant for every two Yb” ion present in the structure (charge balance). The effect of both having the smaller Yb” ion on a Yb" cation site, and some cations absent from the structure, would be to decrease the effective size of the cation. Such a decrease in effective cation size would cause the ratio: rung/rum to decrease, and would further destabilize the SrIa—type structure (i.e. lower the transition temperature possibly to below room temperature), making the CaCh-type structure, which apparently has a slight stability edge over the other two structural-types, the more stable form. Results of the Yb-Br-I phase study, discussed later in this thesis, substantiate this size hypothesis. When the iodide ion is substituted for the bromide ion, the cation-anion ratio is effectively decreased, the Srla structure is destabilized, and the CaCh-type structure is predicted to be stable. The CaCh-type structure was indeed observed. A Yb-Br-I phase with minimal iodide concentration, if cooled to liquid nitrogen temperatures, might be expected to exhibit the SrIr-type structure. Divalent thulium, which is slightly larger than divalent ytterbium transforms at 427°C from the SrIa-type structure to the s—PbO: 73 structure. Tm“, being larger than Yb", would increase the rest ion/remiss ratio, and the SrIs-type structure should exist over a larger temperature range. As compared to Yb(II), the smaller calcium ion in CaBr: does not form either the SH: or s-Pb02-type structures. At room temperature, CaBr: exists as a CaCh structure-type and under heating can be transformed only to the rutile structure. A comparison of the YbBra/YbCh system to other mixed halide systems will be undertaken. Of particular interest are strontium and calcium mixed halide systems because these two systems most closely resemble the present one. Beck“ noted that under high pressure, stronium chloride (face centered Can-type structure) transforms to the more dense, more highly coordinated PbCla-type.” Indeed the 13be type structure is commonly found not only in these, but in other mixed halide systems as well.“ The reason for the formation of this structure probably resides in its greater density and higher coordination number. Mixed halide phases essentially create an internal pressure and thus favor high coordination.“ One reason that the PbClr-type structure was not found in the YbBra/YbCla system could be due to the short time (maximum - 3 minutes) at the final temperature of 750°C. The combination of the time, temperature and quench did not create an internal pressure sufficient for transformation to the PbCl: structure- type. Next a comparison of Yb(II) halide system versus the Sr(II) and Ca(II) halide systems is necessary. The Yb(II) and Sr(II) halide systems are not similar because of their differing crystal radius size, that of Yb(II) - 1.22A and that of Sr(II) - 1.35A. However, if cation radius is the sole criterion the Yb—Cl-Br system should be comparable to that of 74 Ca-Cl-Br“ because the crystal radius of Yb(II) (1.225) is approximately equal to that of Ca(II) (1.265). The Ca-Cl-Br system was reported to exhibit a single phase solid solution of pseudo-rutile-type structure. It would thus seem that in this instance the cation radius is an excellent predictor of system behavior. Another good predictor of mixed halide behavior has been high pressure structural modifications. Unfortunately such structural studies are not available for ytterbium halides, hence, prediction of mixed ion behavior based upon them cannot be made. The observed volume change with composition presented in Figure 11, was expected since the smaller Cl anion was being replaced by a larger Hr anion. However, Vegards’ law is not obeyed in this system as can be seen by the nonlinearity in the region of high molar percent of Yan. If this law were obeyed, each lattice parameter increase should be directly proportional to the increasing mole percent of YbBra. Variations from this law as indicated by the nonlinearity on the YbBrz side could be interpreted as evidence for ordering of the anions into the two anion sites as compared to random site occupancy. To check for anion ordering, x-ray powder diffraction intensity calculations were effected with the program POWDERIZ” for the 75 and 55 mole percent bromide specimens. The results of these calculations are presented in Table 18. Three structural arrangements were considered: 1. random occupancy of the anion sites by both ions, 2. the bromide ion only in the tetrahedral site, and 3. the bromide ion only in the trigonal site. For these calculations the structural and thermal parameters reported for YbClx " were used in conjuction with lattice parameters derived in 75 Table 18. Comparison of observed and calculated intensities for low angle reflections in the YbClz-YbBrz system at the compositions: 0.25YbClz-0.75Yb8r2(A) and 0.45YbClz- 0.55YbBr2(B). Composition hkl Intensity Br in X(l) Br in X(2) obs random (trigonal) (tetrahedral) 200 vw 4 0 10 A 210 w 8 ll 5 111 vw 2 3 1 211 vvs 100 100 100 200 w 4 0 17 B 210 m 8 15 3 111 vw 2 4 1 211 vvs 100 100 100 76 this work. Polynomial scattering factors included in the program were used.“ Neither an absorption correction nor anomalous dispersion terms were included in the calculations, but a correction was made for the incident beam monochromator. On the basis of these observations it is clear that the anions do not uniquely occupy the tetrahedral hole, and it is probable that they do not uniquely occupy the trigonal site. The occupancy appears to be random. The absence of the larger bromide ion in only the trigonal site is not surprising since in the YbCln structure the average Yb—Cl distance for the trigonal site is 0.07 A less than that in the tetrahedral site. As was noted on Table 3, the YbCh-YbBra melts were cooled slowly to room temperature. It was found that rapid cooling of these samples produced broadened X.R.D. reflections. During rapid cooling, the molten samples solidified so quickly through the liquid-solid region to the solid region that a homogeneous composition did not result. Therefore, some parts of the solidified sample could be more chloride or bromide rich, a situation which would cause a slight variation in lattice parameters, and broadened X.R.D. lines. An alternative explanation for the presence of broad X.R..D. reflections is the solidification of rapidly cooled molten samples into a semi amphorous, disordered solid. Slow cooling through the liquid-solid region would minimize this problem and produce a crystalline, ordered solid. Still another explanation for broad X.R.D. lines can be given by the fact that YbBr: exhibits four temperature dependent forms; each of which has a unique X.R.D. pattern which is very closely related to that 77 of the other phases. In the rapidly cooled sample, small regions of high temperature structural forms may have been quenched and be present in addition to the SrIa-type structure. It is possible that SrIa-type and high temperature type reflections might be superimposed. Where superimposition occurred, broadened X.R.D. reflections would result. For the YbBra/YbCl: system, interplanar d-values and relative intensities of unexplained reflections are tabulated in Appendix 4. Attempts were made to fit the various structure-types listed in Table 15 to these unexplained reflections. The interplanar d-values for the rutile, CaCla and m—PbO: structure-types were compared to the unexplained interplanar d-values in the YbBrn/YbCl: system. All three temperature dependent structure-types (rutile, CaCla, s—PbOa) exist for Yan. The interplanar d-values of the last two structures found in Table 15, YbOBr and YbOCl were compared because of the potential oxidation of YbBrz or YbCh. Reflections of these five structures did not match the unexplained reflections in this system. The possibility that these reflections might be the result of superstructure from anion ordering was also considered even though x- ray intensity calculations indicated this to be an unlikely possibility. But because the lattice parameters are so large a doubling of any one leads to such a plethora of reflections that meaningful assignments could not be made. A final preparation of a 45 mole percent YbBra sample which was made long after the original work was complete yielded an X.R.D. pattern where every reflection could be indexed on the basis of the SrIx-type structure. It is thus believed that the spurious reflections belong to an impurity phase which is probably a hydrate 78 that occurred either during the preparatory or x-ray diffraction process. YbCh-th System. Four regions were identified in this system. These regions can be described as follows: from zero to 20 mole percent YbCh, a single phase solid solution region of Cdls-type structure; from 20 to 45 mole percent YbCh, a two phase region with a new, unidentified phase designated A and a single phase CdIc-type structure; from 45 to 60 mole percent YbCh, one solid phase A, and from 60 to 100 mole percent YbCh, a two phase region with phase A and a solid solution region of SrIa-type structure. The presence of phase A is confirmed by the zero slope for volume and lattice parameters as observed in Figure 12 and also the presence of numerous reflections which could not be assigned to a structure in the X.R.D. pattern. Phase A reflections reached maximum intensity near the 50/50 YbCls-Yblx composition region. The two phase regions described above are consistent with the phase rule: F = C - P + 2. (F = number of independent variables or degrees of freedom, C = number of components, and P = number of phases). This system contains three elements (Yb, Cl, 1), but these are constrained to the compositions YbCh and Ybla, hence this must be considered a pseudo two component system. There is only one independent composition variable, Cl, since when one component is fixed, the other also is fixed (l-Cl). Substituting C = 2 into the phase rule and rearranging, one obtains F + P : 2 + 2 = 4 Since measurements were made at atmospheric pressure and room temperature, the vapor pressure of the components is negligible. 79 Therefore, vapor pressure as a variable can be neglected, and one degree of freedom is lost. This assumption reduces the phase rule equation by one to: F + P = 3. The number of degrees of freedom plus the number of phases thus is constrained to equal 3, and when one phase is present there are two variables, temperature and Cl composition; when two phases are present, there is only one variable, temperature. Application of these conclusions to the YbCh-Ybla system indicates that for a single phase region two variables, temperature and composition, prevail; whereas for a two phase region only one variable, temperature, prevails. Thus in a two phase region, composition is fixed and lattice parameters will be invariant to yield a lattice parameter- composition curve of zero slope; whereas, in a single phase region composition is variable, and lattice parameters will change. In the one solid phase region from zero to 20 mole percent YbCla, the cell volume is shown as a line with decreasing linear slope due to the fact that chloride ions are substituted for iodide ions in a Cdlx-type structure. As the chloride ion concentration in the CdIs lattice increases, the lattice parameters decrease because the chloride anion is smaller than the iodide anion. When phase A grows in at 20 mole percent YbCh, two solid phases are present. The probable composition of the phase A is YbCluloa or 60 mole percent YbCla. This composition is based on the assumption that the break in the "a" lattice parameter curve at about 70 mole percent YbCla does not represent a change from a two (solid) phase region to a single phase region. If a change to a single phase region does occur, then the composition of phase A would be YbClosIm or 45 80 mole percent YbCh, the median composition between the initial and final appearance of phase A. The 50 mole percent YbCl: lattice parameter data are not included in Figure 12 because the standard deviation of each lattice parameter is greater than t 0.02A This large deviation is probably due to phase A reflections superimposed on very weak Ybe reflections with the consequence of inaccurate determination of line positions. The "a" lattice parameter can be interpreted to change at 70 mole percent YbCh. Such a variation can be rationalized with the aid of Figure l, a drawing of the SrI: structure. In this figure, anion 2 occupies a tetrahedral site; whereas anion 1 occupies a trigonal site. The smaller balls represent the Sr atoms. If one starts with pure YbCh, one can imagine an iodide ion substituting for a chloride ion in the SrIx-type structure as the YbCla/YbI: melt is cooled. The CN VI crystal radius of the iodide ion (2.065) is 0.39A larger than that of the chloride ion." The space group of this structure and the atom site numbering scheme are identical to those used by Baernighausen, et al. in reporting the YbCh structure.“ The structural data for YbCh can thus be viewed directly in this figure. In the YbCl: structure the distances between the anions labeled 1,1’, and 1" are 3.83-3.89A those between the anions labeled 2,2',2" and 2’" are 3.35-3.36A The Yb-Cl(2) distances are slightly longer than the Yb-Cl(l) distance, probably an indication that Cl(2)-Cl(2) anion contact is preventing the Yb atom from closer contact with the site (2) anions. If the site 2 anions are in contact, it seems probable that the larger iodide anion will prefer to occupy site (1) positions when substitution occurs. Because of their shorter Yb-Cl(1) distance, the anions labeled (1) are 81 presumed to have strong metal-anion contacts and weaker anion-anion contacts. An iodide substituting in one of these sites would therefore increase the metal anion distance (the a parameter) more than the anion- anion distance (the b and c parameters). However, if iodide ions were substituted for 30 percent of the chloride ions in the unit cell, the volume expansion expected on the basis of the CN VI anion radii," with no structural rearrangement, would be {41(2.06'-1.67’)/3), 171! per iodide ion or 82!! {0.30x16x17fi) per unit cell. How well this theoretical volume difference between the anions approximates the actual volume change of the unit cell can be determined from an analysis of the opposite end of the system where the presence of solid solution was confirmed. It was pointed out (Figure 12) that 20 mole percent YbClz could be substituted for YbIa in the CdIa-type structure. The formula of the unit cell of the 20 mole percent substituted material would be YinsClM, and the volume change expected from the substitution is {0.2x2x17fi), or 6.8”. The observed volume charge of ~3R is about half this value, indicative not only of the extensive structural rearrangements that occur, but also that about s 40H (half of 82R) volume change should occur if 30 mole percent substitution occurred at the chloride rich end. The observed expansion of about 2” is totally inconsistent with this calculation, and leads to rejection of the hypothesis that iodide substitution has occurred to the 30 percent level. The composition of phase A is therefore inferred to be YbChans (60 mole percent YbCh), and only minimal iodide substitution must occur in the YbCl: structure. Due to the presence of 25 unindexed reflections in the 20 to 65 mole percent YbCls/Ybla samples, the X.R.D. patterns of the various 82 structure-types listed in Table 16 were calculated and compared to these unassigned reflections. The CaCla, s-Pb03, rutile, SrIa, Srh(II) and YbOBr structure-types were considered because the radius of the Br anion is intermediate to that of the chloride and iodide anions. The PbCla structure-type was considered because it has been identified in some stronium halide systems as has been discussed in the YbCla/YbBra X.R.D. discussion section. Two other structure-types, CdIa and CdCh were considered because one member of the system, YbIz exhibits the CdIa structure-type. Since both YbClx and YbIa are susceptible to oxidation, YbOCl and YbOI were considered. The very common PbFCl structure-type is found in compounds LaOI, LaClSe, ThOSe and ThOS which have ionic radii similar to those of YbClI. The last structure listed, BiSI was considered because of results obtained from application of both the Hess-Lipson and Ito’s procedures“ to phase A reflections. These procedures yielded lattice parameters of a = 11.14, b = 9.47, c = 6.6244 and p = 102.7°. Since these lattice parameters describe an RX: monoclinic cell, Wycoff“ was searched for a similar structure and only BiSI was found. Ito’s method“ was also tried alone with the interplanar d-values that could be assigned to phase A reflections with the VAX program ITO-9.“ The necessary figure of merit of greater than 10 with 18 out of 20 lines indexed was not found. It is concluded that this phase A exhibits either a new or relatively uncommon type of structure. YbBre-th System. The results of six successful melt experiments run for this system are summarized in Table 14. These results may be described as follows: zero to 35 mole percent YbBra; a single phase CdIa structure-type and from 80—100 mole percent YbBrz; a 83 single phase CaCl: structure-type. An increase in the percent bromine from zero to 35 mole percent YbBr: causes the size of the CdIa-type lattice to decrease because the Br anion is smaller than the I anion. A similar result is seen when the 100 mole percent YbBra sample is compared to the 80 and 85 mole percent YbBr: samples; the CaCh-type lattice is found to increase in size. The results of the 35, 80 and 85 mole percent YbBra samples, and the three remaining melt samples (45, 60 and 75 mole percent YbBra) are presented in Figure 13. These remaining melt samples were identified from the X.R.D. films as follows: 45 mole percent YbBrr-new phase A; 60 mole percent YbBr2-a two phase region with new phase A and new phase B; and 75 mole percent YbBrr-a two phase region with one phase of the CaCh structure-type and the other consistently of new phase B. The X.R.D. patterns of neither phase A nor phase 8 could be explained by either the Cde or CaCla structure-type. An additional five melt samples were found to contain YbBr2/Ybla(HaO)x as shown in Table 19. The 15, 25 and 30 mole percent YbBr: melt samples in which a single phase CdI: structure—type was found confirmed the earlier results of the zero to 35 mole percent YbBrx samples. One result that needs comment is the presence of the CaClz structure-type in the 80 and 85 mole percent YbBr: samples. As discussed in YbCla-YbBr: section, substitution of a larger iodide ion for a bromide ion is equivalent to decreasing the l‘cettee/Pssies ratio. It was postulated in the YbCh/YbBra discussion section that as the reason/rum ratio decreases (i.e. compare radius ratio rYb”/rCl' versus rYb’terr'), the Srlz-type structures destabilizes and a mixture 84 of CaCh and Srh-type structures are exhibited. In the Yb-Br-I system, the radius ratio decrease may have destabilized the SrIx-type structure because the CaCh-type structure alone was exhibited. A literature reference to the existence of a th hydrate was investigated. No reference for YbI:(H:O)x could be found, but hydrates of other divalent metal halide systems have been studied extensively. The monohydrate is found to be the most common among metal(II)-halide systems. The following monohydrates crystallize in an orthorhombic form with space group ana: SrBrg-Hso fl', EuBrrHaO fl’, Rule-H30 71, SmBrrHaO ", BaCeraO 7' and SrCla'on.‘M The large differences in the cation/anion ratios of the above monohydrates would lead one to expect YbIa-HaO to crystallize in the same easily indentified structure. On the other hand, the hemihydrates, 28aC1rH30 7' and ZSrCeraO '" crystallize in a structure that has not been characterized. The interplanar d-values of the YbI: hydrate are reasonably similar to those of the two uncharacterized hemihydrates, but are very different from the well characterized monohydrates. The formula of the hydrate is therefore suspected to be 2YbIa°H30. 85 Table 19. Phases exhibited in YbBrz/YbIz(H20)x system. Mole X YbBrz Phase 15 Cdlz-Type 25 CdIz-Type 30 CdIz-Type 40 New Phase A 42 New Phase A Note: Phases determined by visual comparison of X.R.D. films in which the CdIz-type structure and phase A were found. No d-values were calculated for the above samples. Therefore, no mole percent limit can be set for phase A. 86 OR: .Egmhm .um .vw .Ha>\€ma> one new mom»? menace—saw 3.5.; a woos. AV? seas ~88 on». «68 AJIT .2 959a on A as: N. 8 87 Conclusion Ytterbium mixed dihalide systems are compared to the europium(II) and calcium mixed halide systems. These comparisons are made because europium, like ytterbium, is a member of the lanthanide series of elements. Europium(II) has a half-filled f shell; whereas ytterbium(II) has a filled f shell. On the other hand, calcium and ytterbium(II) have the same size ionic radii. The europium and ytterbium mixed dihalide systems are compared first. In the YbClz-YbBrs system, one solid solution of an Srla-type structure was found. The EuCla-EuBr: system“ exhibited three regions: zero to 5 mole percent EuCh, a single phase SrBrr-type structure; 5 to 15 mole percent EuCla; two phases indexed with lattice parameters of the terminal phases-m5 mole percent EuCh and 15 mole percent EuCh and from 15 to 100 mole percent EuCh, a single phase PbCl: structure-type. One explanation for the differences between the above two systems may be attributed to the structure types of each individual lanthanide dihalide; i.e., for the Yb-Cl-Br system, both YbCl: and YbBr: exhibit an SrIa structure-type. For the Eu-Cl-Br system, EuCla exhibits a PbCla structure-type and EuBrz exhibits a SrBr: structure-type. In view of this evidence, a multiphase system would seem more likely to be found in the Eu-Cl-Br system in contrast to the Yb-Cl-Br system. The smaller ytterbium(II) ion apparently is able under the internal pressures created by the mixed anion system to accommodate both anions. Under higher pressures, the PbCh structure- type would probably form. On the other hand, the calcium bromide- chloride system,‘° like that of ytterbium is characterized by one solid solution of pseudo Ti03 structure-type. Each of parent phases, CaBr: 88 and CaCla exhibit the orthorhombic CaCh-type structure. From these data, it would seem that size constraints are the predominant predictor of structure-type. The YbCla-Yblz system formed a total of four regions as follows: from zero to 20 mole percent YbCh, a single phase CdIz-type structure; from 20 to 45 mole percent YbCh, two phases with phase A and a single phase of CdIa-type structure; from 45 to 60 mole percent YbCh, a single phase labeled A and from 60 to 100 mole percent YbCh, two phases--one labeled A and the other an Srh-type structure. The Eu-Cl-I system“ formed three principal regions as follows: from 0 to 50 mole percent EuClx, two phases both with lattice parameters typical of PbCh-type structures; 50 mole percent EuCla, a PbCh-type structure and from 50 to 100 mole percent EuCla, two phases with PbCh-type structures. The parent phases are as follows: EuCh, PbCla-type structure and Eula, both the SrIa-type structure and an m—EuI: structure. A PbCh-type structure did not form in the Yb-Cl-Br system, and it was not found to correspond to phase A of the Yb-Cl-I system. Even in the absence of the structural type exhibited by phase A, it is apparent that these systems are very different. In contrast, the Ca-Cl-I system“ contains three regions, from 0 to 5 mole percent CaCh, CdI: structure-type; from 5 to 97.5 mole percent CaCh, two phases - CdI: and CaCh, and from 97.5-100 mole percent CaCh, CaCla structure-type. While the Yb-Cl-I and Ca-Cl-I systems are similar at the iodide end, there is a significant difference between these two systems at the chloride and. Also, the presence of a discrete, unique phase of intermediate composition was found in the Yb-Cl-I system and no new phase was found in the Ca-Cl-I system. This difference in behavior points out, (in contrast to the 89 apparent conclusion derived from the Yb-Cl-Br system) that radius ratio or size is not the sole criterion in determining the structures of mixed halides. The complexity of the Eu-Br-I system‘1 with seven distinct regions is similar to that of the Yb-Br-I system with five distinct regions. A comparison between the two solid solution regions found in the Yb-Br-I versus the Ca-Br-I systems are as follows: one solid solution region of CaBrxlx-x, from 0 < x < 0.4 versus YbBrxla-x, from 0 < x < 0.7 and a second region of CaBrs-yly, from 0 < y < 0.2 versus YbBrz-ny, from 0 < y < 0.4. Outside of these solid solution regions a two phase region is exhibited in the Cs-Br-I system and is composed of the terminal phases. It is interesting to note that the solid solution region in the ytterbium system is much greater at both ends than in the calcium system. In this case, size is not a factor because the coordination number six radii indicate only a 0.02A difference between Yb(II)-1.1611 versus Ca(II)-1.1419" In addition, two new uncharacterized phases occur in the ytterbium system, while there is no new phase formation in the calcium system. In conclusion, the results presented in this thesis indicate both radius ratio alone (i.e., Yb-Cl-I versus Ca-Cl-I) and high pressure structure types alone (i.e., Yb-Cl-Br versus Eu-Cl-Br) to be poor criteria to use to analyze the behavior of mixed halide systems. However, Pearson’s hard/ soft acid-base theory may help explain the behavior of the Yb-Cl—Br system versus those of the comparable Eu(II) and Ca(II) systems. In the Ca-Cl-Br system, a pseudo TiO: structure was exhibited with a coordination number for the calcium ion of six and a 1.14A size.” 90 The Yb-Cl-Br system also exhibited only one Srlz-type phase in which the coordination number of the ytterbium is 7 with a 1.22A size." A PbClr-type structure was found in the Eu-Cl—Br system (from 15 to 100 mole percent EuCh) where the cation coordination number is nine with a 1.44A size. Therefore, the actual sizes of the atoms are significantly different. In an extrapolation of Pearson’s theory, a small size cation like Ca(II) in the Ca-Cl—Br system can be equated to "hardness", whereas a larger ion like Eu(II) can be equated to "softness" and be more able to form covalent-er bonds as compared to Ca(II). The "softer" the ion is, the more easily it will deform, and therefore, allow multiple phase formation to occur as was found in the Eu-Cl-Br system. On the other hand, the "hard" calcium(II) ion should not be susceptible to the internal pressure from mixed halide size difference and should not form multiple phases. This is confirmed by the fact that only one phase is exhibited in the Ca-Cl-Br system. 91 FUTURE EXPERIMENTS In all three ytterbium dihalide systems further work should be done. The question of whether the anion site occupancy of the Yb-Cl- Br system is random or ordered should be clarified definitively. This determination can be made most convincingly by line profile analysis of digital x-ray powder intensity data. The new phase, labeled A, which was observed in the Yb-Cl-I system should be characterized. X-ray positional and intensity data should be made from a melt of a 55 mole percent YbIa sample because the new phase is presumed "pure" at that composition. The composition of the YbIa hydrate should be determined. In order to eliminate formation of the YbIr(H:O)x in the YbI: synthesis, the Pyrex tube must be completely freed of absorbed water. The mercuric iodide should be sublimed and mixed with small pieces of ytterbium in an absolutely dry glove box. In the Yb-Br-I system the two new phases labeled A and B should be characterized by mixing a 40—42 mole percent YbBra sample to identify phase A and by mixing a 65 mole percent YbBrx sample to identify phase 8. Since the 55 mole percent YbBrz sample is a mixture of phases A and B, this mixture may help confirm the finding of the 40 and 65 mole percent YbBr: melt samples. The hypothesis that the CaCh-type YbBra structure is stabilized by ytterbium(III) impurities may be tested by spectrophotometric techniques. Properties of oxygen free aqueous and aqueous-ethanol solutions of ytterbium(II) have been studied spectrophotometrically, so 92 therefore, ytterbium(III) might be identified with this technique.” A second hypothesis stating that elemental ytterbium can be dissolved in YbBra, should be tested. If electrons are indeed trapped in anion sites or at F-centers, this material may exhibit semiconducting preperties. 1. 2. 3. 4. 10. 11. 12. 13. 14. 15. 16. 17. 18. 93 REFERENCES M. D. Taylor, QQQQLWBng 62, 503(1962). M. D. Taylor and C. P. Carter, J. Inorg. Nucl. Chem., 24, 387(1962). O. G. Polyachenok and G. I. Novikov, J. Gen. Chem. U.S.S.R., 33(3), 2725(1963). L. B. Asprey, T. K. Keenan and F. H. Kruse, Inorghghem. 3, 1137(1964). O. G. Polyachenok and G. I. Novikov, Russ. J. Inorg. Chem., 9, 429(1964). L. B. Asprey, T. K. Keenan and F. H. Kruse, "Proc. Conf. Rare Earths," Phoenix, Arizona, 1964, pp. 527-34. D. T. Cromer, private communication. J. K. Howell and L. L. Pytlewski, J. Less Comm. Metals, 18, 437(1969). J. K. Howell and L. L. Pytlewski, J. Less Comm. Metals, 19, 399(1969). 0- W- DeKock and D- D- Radtke. JInorarNuchhem: 32» 3687(1970). K. E. Johnson and J. R. MacKenzie, JInorg Nucl. Chem., 32, 43(1970). J. D. Corbett, Inorg. Nucl. Chem. Lett., 8, 337(1972). F. L. Carter and J. F. Murray, Mater. Res. Bull., 7, 519(1972). "International Tables for X-Ray Crystallography," Vol. IV, Kynoch Press, Birmingham, England (1974). H. Baernighausen, H. P. Beck and H. W. Grueninger, "Proc. Rare Earth Res. Conf." Vol. I, 1971, p. 74. H. Baernighausen and H. P. Beck, Z. Anorg. Align. Chem., 386, 221(1971). J. M. Haschke, "Handbook on the Physics and Chemistry of Rare Earths," North Holland Publishing 00., Vol. IV, New York, New York, 1979, p. 89. N. B. Mikheev, A. N. Kamenskaya, N. A. Konovalova and T. A. Zhilina, Russ. J. Inorg. Chem., 22, 955(1977). 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 94 A. N. Kamenskaya, N. B. Mikheev and N. A. Konovalova, Rugs; :1. Inorg. Chem., 22, 1152(1977). V. F. Goryushkin, A. I. Poshevneva and D. M. Lapter, 395313; Inorg. Chem., 27, 140(1982). P. Girard, J. L. Namy and H. B. Hagan, J. Amer. Chem. Soc., 102, 2693(1980). G. B. Deacon and A. J. Koplick, Inorg. Nucl. Chem. Lett., 15, 263(1979). P. L. Watson, J. Chem. Soc., Chem. Comm., 652(1980). H. Imamura, A. Ohmura and S. Tsuchiya, 993.9;1931'4' 203, (1984). J. L. Namy, P. Girard and H. B. Hagan, Nouv. J. Chim., 5, 479(1981). nem..-d-v-pum-’~wvsfi Inorg. Chem. 27, 1229(1982). - —.|'- “'5 l.‘ -‘I‘T J‘."".’J‘N" m .— l—l G. B. Deacon, P. I. Mackinnon and T. D. Tuong, Aust. J. Chem., 36, 43(1983). 1r- 1 W. B. Jensen, J. Chem. Educ. 59, 634(1982). A. K. Molodkin, A. M. Karagodina, A. G. Dudareva, A. G. Krokhina and V. S. Tupolev, Russ. J. Inorg. Chem., 29, 14(1984). W. Bossert, Ph.D. Thesis, University of Karlsruhe, Germany, 1981. L. B. Asprey and B. B. Cunningham, Profiqunorg. Chem., 8, 267 (1960). J. D. Corbett, Rev. Chim. Miner., 10, 239(1973). A. N. Kamenskaya, N. B. Mikheev and A. I. Strekalov, Russ Inorg. Chem., 28, 965(1983). O. G. Polyachenok and G. I. Novikov, Russ. Inorg. Chem., 8, 1378(1963). A. N. Kamenskaya, K. Bukietynska, N. B. Mikheev, V. I. Spitsyn and B. Jezowska-Trzebiatowska, Russ. Inorg. Chem., 5, 633(1979). D. A. Johnson, "Advances in Inorganic Chemistry and Radiochemistry," Vol. 20, Academic Press, New York, 1977, pp. 1- 131. W. Klemm and W. Schuth, Z. Anorg. Allg. Chem., 184, 352(1929). J. L. Namy, P. Girard and H. B. Kagan, Nouv. J. Chim., l, 5(1977). H- Schafer: 42.....49993:....4..1.1.5.:_....Qh9a-. 445: 129(1978>- 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 95 H. Baernighausen, Z. Anorg. Allg. Chem., 403, 45(1974). L. B. Asprey and F. H. Kruse, J. Inorg. Nucl. Chem., 13, 32(1960). N. A. Fishel and H. A. Eick, J. Inorg. Nucl. Chem., 33, 1198(1971). J. K. Howell and L. L. Pytlewski, J. Appl. Crystallogrfl 3, 193(1970). Powder Diffraction File, Inorganic Phases, Alphabetical Index, JCPDS International Centre for Diffraction Data, Swarthmore, Penn., 1983. D. E. Cox and F. K. Fong, J. Cryst. Growth, 20, 233(1973). D. F. Evans, G. V. Fazakerley and R. F. Philips, J. Chem. Soc. A., 1931(1971). R. S. Mitchell, 92...-Kfilfi19139559 108, 296(1956). E.Th. Rietschel and H. Baernighausen, Z. Anorg. Allg. Chem., 368, 62(1969). P. Gordon, "Principles of Phase Diagrams in Materials Systems," McGraw-Hill Book Company, New York, 1968. G. Brandt and R. Diehl, Mater. Res. Bull., 9, 411(1974). G. Schmidt and R. Gruehn, J. Cryst. Growth, 57, 585(1982). CRC Handbook of Chemistry and Physics, 58th Ed., CRC Press Inc., Cleveland Ohio(1978). D. Brown, "Halides of Lanthanides and Actinides," J. Wiley- Interscience Publication, New York, 1968, p. 151. J. of Phy. and Chem. Ref. Data, 7, 892(1978). JANAF Tables, Second Edition, United States Department of Commerce, Washington D.C. R. W. G. Wycoff, "Crystal Structures," Second Ed., Vol. 1, Interscience Publishers, New York, 1963. A. V. Hariharan and H. A. Eick, High Temp. Sci., 4, 379(1972). J. W. Visser, J. Appl. Cryst., 2, 89(1969). J. E. Huheey, "Inorganic Chemistry," Third Ed., Harper and Row, New York, 1983. H. P. Beck, Z. Anorg. Allg. Chem., 459, 72(1979). 61. 62. 63. 64. 65. 66. 67. 68. 69. 700 71. 72. 73. 74. 96 E. K. Hodorowicz, S. A. Hodorowicz and H. A. Eick, J. Solid State Chem. 52, 156(1984). S. A. Hodorowicz and H. A. Eick, J. Solid State Chem. 46, 313(1983). S. A. Hodorowicz and H. A. Eick, J. Solid State Chem., 43, 271(1982). R. M. Bozorth, J. Amer. Chem. Soc., 44, 2232(1922). E. K. Hodorowicz, S. A. Hodorowicz and H. A. Eick, J. Solid State Chem., 49, 362(1983). S. A. Hodorowicz, E. Hodorowicz and H. A. Eick, Crystal Res. and Techno}, l9, 1377(1984). R. D. Shannon, Acta. Cryst., A32, 751(1976). B. G. Hyde, L. A. Bursill, M. O’Keeffe, S. Anderson, Nature~ (London) Phys. Sci., 237, 35(1972). D. K. Smith, M. C. Nichols and M. E. Zolensky, "A FORTRAN IV program for Calculating X-Ray Powder Diffraction Pattern-Version 10" The PennsylvaniaWState University, University Park, PA (1983). J. M. Haschke and H. A. Eick, J. Inorg. Nucl. Chem. 32, 2153(1970). J. M. Haschke, 199.983.911.259” 15, 508(1976). J. M. Haschke, Inorg. Chem., 15, 298(1976). H. D. Lutz, W. Becker, Ch. Mertins and B. Engelin, Z. Anorg. Allg. Chem" 457, 84(1979). H. D. Lutz, B. Frischemeier, Ch. Mertins and W. Becker, .Z...:..-.飑9£8.-z 4.1.1.82--.Ch.9!!!n 441: 205(1978). 97 Appendix 1. Interplanar d-spacings and relative intensities observed for YbClz (068b/84) versus those calculated from literature data. 9.1 .1. 1.1.15.1" <13. .1..." 6.58488 W 200 6.5750 3.8 4.78099 W 210 4.7737 7.6 4.53132 W 111 4.5242 1.9 3.88408 8 211 3.8864 100.0 3 47686 M 020 3.4710 10.3 3.35061 M 002 3.3465 14.5 3 29273 W 400 3.2875 9.4 3 24893 W 102 3.2431 2.5 3 09338 W 021 3.0813 3.7 3 01135 W 121 3.0000 2.4 2 97535 W‘ 410 2.9712 1.7 2 79906 W 221 2.7901 3.3 2 74637 M 212 2.7402 7.2 2.71900 M 411 2.7156 9.5 2.66593 W 302 2.6599 3.1 2.41321 M 022 2.4091 21.1 2.38898 M 420 2.3868 17.0 2.34727 M 402 2.3452 19.3 2.31245 W‘ 511 2.3085 0.0 2.26832 W 222 2.2621 3.4 98 Appendix 1 continued. S! .1. hkl.‘ <13. if 2.25133 M 421 2.2482 9.4 2.22621 hr 412 2.2218 1.1 2.18750 M 230 2.1828 10.7 2.10354 W 113 2.0968 2.5 2.07955 M 231 2.0752 12.1 € 2.02388 M 213 2.0212 17.6 1.99600 M 611 1.9950 19.3 1.94756 M 422 1.9432 7.1 a. Computer program ANIFAC, l.p.-ref. 40; p. 46 and atomic - parameters—ref. 40; p. 48. 99 Appendix 2. Interplanar d-spacings and relative intensities observed for the YbBr2(55)/YbClz(45) melt sample. 9 1 hisi 6.77526 W 200 4.91763 M 210 4.68883 W* 111 3.99197 SD 211 3.58427 W 020 3.43388 Wb 002 3.38868 W 400 3.32947 WV 102 3.11459 W 121 3.06322 W 410 2.87592 W 221 2.79216 WD 411 2.73169 W 302 2.48119 M 022 2.45905 M 420 2.40826 WP 402 2.31844 WD 421 2.25405 M 230 2.13966 M 231 2.07581 WT 213 2.05162 M 611 2.00399 Wt 422 Appendix 2 continued. 1.96626 1.91050 1.88499 1.84393 1.73346 1.64806 1.60871 =2==i==9=5=i 1.54513 0" = broad 313 620 602 621 240 810 304 441 100 101 Appendix 3. Interplanar d-spacings and their relative intensities of the YbBrz (146-10-858) sample and theoretical values calculated for SrIz-type YbBr2 from literature data. 51 .1. 1315.1“ (13. .i 6.878 W 200 6.8993 8.2 5.0259 W 210 5.0331 11.2 4.7789 W‘vb 111 4.7895 4.4 4.3260 ? —-- -- --- 4.0973 SH 211 4.1048 100.0 3.6729 WP 020 3.6794 6.3 3.5438 W+ 002 3.5467 14.8 3.4482 ? 400 3.4497 5.2 3.2454 “P 220 3.2465 8.8 3.1753 WD 121 3.1783 11.5 3.1211 M‘ --- —-- --- 3.0089 ? ——— -—— ——— 2.9486 M 221 2.9520 17.5 2.8959 Mb 212 2.8992 26.5 2.8553 M 411 2.8586 32.2 2.8043 WD 302 2.8087 12.4 2.5525 S 022 2.5535 47.1 2.5158 S 420 2.5166 28.7 2.4703 Mb 402 2.4729 32.0 2.3930 “F 222 2.3947 13.2 2.3692 “F 421 2.3717 20.7 . . ads .03 102 Appendix 3 continued. 9 .1. 415.1.“ 93. .1. 2.3101 S 230 2.3112 31.3 2.2213 W 113 2.2217 9.7 2.1964 M 231 2.1975 16.5 2.1383 Mb 213 2.1401 22.8 2.0957 M 611 2.0970 37.8 2.0206 W 313 2.0219 6.0 1.9881 W 023 1.9891 3.6 1.9685 W 123 1.9698 8.9 1.9501 W 620 1.9502 3.3 1.9351 WD 232 1.9363 10.5 1.7814 W' 041 1.7808 5.0 1.7777 W“ 240(?) 1.7776 5.4 9’ Computer program ANIFAC, 1.p.-ref. 17; p. 119 and atomic parameters-ref. 48, p. 63. b = broad Appendix 4 . 103 Intensities and interplanar d—values of unexplained reflections observed in the YbBrz/YbCh system and compiled as a function of mole percent YbBrz. 25 40 65 75 85 95 10.24211 W' 9.57574 39 4.28260 W 4.28142 M 4.58981 W" 5.17943 W 5.91766 W 4.00469 W" 4.6455 W 4.17544 W' 4.17452 W 4.31368 W' 4.34035 W' 3.90287 W' 3.93491 W 3.87189 W 3.86998 W 3.90971 W' 4.22099 W' 3.50459 W" 3.91366 W 3.03140 W' 2.97549 W 3.01004 W' 3.92089 W' 2.87539 W' 3.614321 W 2.98403 W" 2.72451 W‘ 2.20217 W 2.75929 W‘ 2.63658 W' 3.37264 W 2.77054 W‘ 2.40687 W' 1.40086 W” 2.56218 M 2.41356 M 2.77931 M 2.72393 W‘ 2.21834 W' 2.31947 W‘ 2.35896 W" 2.67684 W' 2.54060 W' 2.14102 W— 2.18277 W’ 2.34748 W 2.43571 W 2.35862 W' 1.68977 W‘ 1.40306 W 2.38701 W' 2.27740 W 2.37673 W' 1.38694 W' 1.38256 W' 2.21008 W 1.93131 W 1.36390 W' 1.37679 W' 2.03144 M 1.55098 W' 1.36389 W" 1.94591 W 1.46975 W” 1.89330 W” 1.42966 W° 1.83507 W‘ 1.53890 W‘ 1.51277 W' Note: b represents a broad reflection line. 104 Appendix 5. Sinzfl, interplanar despacings and relative .5393} OOOOOOOOOOOOOOOOOOOOOOO .00836 .02228 .02590 .03512 .04333 .04449 .04927 .05734 .06035 .06301 .06492 .07159 .07997 .08921 .09085 .09399 .09785 .10026 .10365 .11043 .12445 .12942 .13420 intensities for YbBrz (083b-85) with h,k,l’s from literature data. d i .851. 8.42381 W' 5.16020 hr 4.78640 S° llO-CaClz(a) 4.10998 W 211-SrI2(b) 3.70025 M 011-CaClz(a) 3.65188 S 101-CaClz(a) 3.47002 W 020-Ca012(a) 3.21677 8 lll-CaClz(a) 3.13521 Si none 3.06855 M 120-CaClz(a) 3.02306 W 2.87875 W 411/212 SrI2(b) 2.72378 W 2.57881 W 2.55544 W 022-SrIz(b) 2.51238 S 420—SrI2(b)/121-Ca012(a) 2.46236 S 211-C8012(a) 2.43258 W 2.39250 S 222-SrI2(b)/220-CaC12(a) 2.31783 W 2.18341 S 002/130-CaClz(a) 2.14109 W 213-Sr12(b) 2.10258 W 611-Sr12(b)/310-CaC12(a) Appendix 5 continued. 0.14995 0.15328 0. 15857 0. 15092 0. 15570 0.17158 0.17318 0. 18719 0.20285 0.21101 0.21821 0.22127 0.22814 0.23344 0.24272 0.24922 0.25294 0. 25953 0 . 25045 0. 25522 0.29199 0.29529 0.30568 .03958 .98912 .96740 .93432 .92032 .89224 .85953 .85089 .78031 .71015 .67678 .64891 .63709 .6121 .59419 .56344 .54291 .53151 .51194 .50928 .49284 .4254? .41506 .39316 105 his; 031-CaClz(a) 112-CaC12(a) 123-Sr12(b). 232-SrIz(b) none 311-CaClz(a) 320-CaC12(a) 022-Ca012(a) 122-CaClz(a) 32l-CaC12(a) 140-Ca012(a) 233—SrI2(b) none 222-CaClz(a) 330-Ca012(a) l4l-CaC12(a) 132-Ca012(a) 240-CaC12(a) 312-CaClz(a) 411-CaC12(a) 420-CaClz(a) 103-CaClz(a) 322-Ca012(a) 113-CaClz(a) 106 Appendix 5 continued. £1.93! 9! .1. his}. 0.31713 1.36777 W' 340-CaC12(a) 0.32185 1.35819 Si none 0.38220 1.24566 Si none 5. a.p. Reference 30, page 25; 1.p., Reference 15, page 79. b. a.p. Reference 48, page 63; 1.p. Reference 17, page 119. Note: no rutile as YbBrz (Reference 30); sbe02 as YbBrz (Reference 30); Ta (Reference 44); TaBr2.83 (Reference 44); TaBrs (Reference 44). 107 Appendix 6. 311120, interplanar d-spacings and relative intensities for YbBrz (064b/84) with hkl’s from literature data. 91939 9 I 951 0 00857 8.27157 8 0.01245 5.89907 ur 0.01757 5.79495 w- 0.02245 5.13988 8r 0.02349 5.02530 w- 0.02505 4.77155 s llO-Srlz(b)/110-Ca012(a) 0.03151 4.33887 Mr 0.03318 4.22851 3r 0.03535 4.09571 3 0.04344 3.59545 M Oll-SrIz(b)/Oll Cac12(a) 0.04472 3.54230 3 101-SrI2(b)/101 Ca012(a) 0.04729 3.54192 w 0.04945 3.45337 w— 020-CaC12(a) 0.04987 3.44900 5r 101-YbOBr(c) 0.05714 3.22214 s lll-SrI2(b)/lll-CaClz(a) 0.05895 3.17205 8 0. 05035 3.13580 31 none 0. 05081 3. 12355 w— 0.05314 3.05528 M 120-SrI2(b)/120-CaClz(a) 0.05805 2.95240 w~ 0.05959 2.91974 8 0.07041 2.90277 3r 0.07255 2.85748 8 0.07572 2.79919 M 102-YbOBr(c) Appendix 6 continued. 108 2.1.9.2.! 9 .i. 8.; 0.08277 2.67735 M 110-Yb08r(c) 0.09109 2.55208 M 0.09432 2.50795 S 121-Sr12(b)/121-CaClz(a) 0.09822 2.45766 S 211—SrIz(b)/211-CaC12(a) 0.10053 2.42937 hr 0.10401 2.38835 M 220-SrI2(b)/220-CaClz(a) 0.10544 2.37211 W 0.11118 2.30999 W 0.11449 2.27637 W‘ 0.11679 2.25390 Wb 0.11837 2.23874 W‘ 103-YbOBr(c) 0.11994 2.22406 Wk 0.12259 2.19987 W‘ 002-CaClz(a) a. a.p. Reference 30, page 25; 1.p. Reference 15, page 79. b. a.p. Reference 48, page 63; 1.p. Reference 17, page 119. c. Reference 44, page 1039. Note: No aer02 as YbBrz (Reference 30); rutile as YbBr2(Reference 30); Zn (Reference 44); ZnBrz (Reference 56).