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This is to certify that the
thesis entitled
THE PREPARATION AND STRUCTURE
CHARACTERIZATION OF SmSYBrl3
presented by

Paul Anthony Pezzoli

has been accepted towards fulfillment
of the requirements for

Mo 5. - degree in - $3er

 

   
 

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aj professor

Date )ZG’UT 01 /77'f7

0-7639

THE PREPARATION AND STRUCTURE

CHARACTERIZATION OF Sm YBr

5 13

BY

Paul Anthony Pezzoli

A THESIS
Sumbitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of
MASTER OF SCIENCE

Department of Chemistry

1977

ABSTRACT

THE PREPARATION AND STRUCTURE

CHARACTERIZATION OF smSYBr13

BY
Paul Anthony Pezzoli

A unique compound, SmSYBrl3, was prepared upon the
reaction of samarium metal with samarium tribromide and
yttrium tribromide. This samarium yttrium bromide phase was
identified and characterized by analytical techniques and X-
ray diffractometry. The gray-black product was found to
exhibit monoclinic symmetry. The space group for this
compound is C2/c. Unit cell lattice parameters calculated
by least squares regression analysis are: a = 44.310 x
A and

O O
A, E = 7.139 r 0.008 A, E = 7.651 + 0.007

1 4 2 l ‘ 5
0
angle g = 98.451 i 0.068 . This phase was identified as a

0.05

member of a class of compounds of the general formula
Mnx2n+l where n=6, which exhibit a vernier-type structure.
Single crystals of SmsYBr13 were prepared for future struc-
tural analysis.

Attempts to prepare the hafnium analog, SmSHfBrl3,

were unsuccessful.

ACKNOWLEDGEMENTS

The author wishes to express sincere appreciation
to Professor Harry A. Eick for the guidance, patience
and assistance he provided during the course of this
research.

My parents are acknowledged, in particular for
their encouragement and hOpes in the attainment of this
educational goal.

The members of the High Temperature Group are
acknowledged for their help and fruitful discussions.

Appreciation is extended to Lisa Ittner, who spent
many long hours typing this manuscript.

Finally, the financial and moral support of The Dow
Chemical Company and, in particular the management of the
Central Research Inorganic Laboratory, is most gratefully

acknowledged.

ii

Chapter
I

II

III

TABLE OF CONTENTS

INTRODUCTION . . . . . . . . . . .

BACKGROUND AND THEORETICAL CONSIDERATIONS.

PREPARATION OF RARE EARTH HALIDES.
Rare Earth Trihalides . . . .
Rare Earth Dihalides. . . . .

Single Crystal Preparation. .

Mixed Valence Rare Earth Halides.

STRUCTURAL INFORMATION . . . . . .

Samarium Tribromide . . . . .

A. Anhydrous Samarium Tribromide

B. Samarium Tribromide Hexahydrate

Samarium Dibromide. . . . . .

A. Anhydrous Samarium Dibromide.

B. Samarium Dibromide Monohydrate.

Mixed Valence Samarium Bromide.

Yttrium Tribromide. . . . . .

Hafnium Tetrabromide. . . . .
EXPERIMENTAL PROCEDURES. . . . . .
CHEMICALS AND MATERIALS. . . . . .
HANDLING PROCEDURES. . . . . . . .

iii

Page

10
10
10
10
10
ll
11
ll

14
15
15

Chapter Page
PREPARATIVE PROCEDURES. . . . . . . . . . 15
Anhydrous Samarium Tribromide. . . . 15

Reduced and Mixed Valence Samarium

Bromides . . . . . . . . . . . . . . 18
A. Sealed Containers. . . . . . . . 18
l. Samarium Dibromide . . . . . 18

2. Sm6Br13. . . . . . . . . . . 18

3. SmSYBrl3 . . . . . . . . . . 19

4. SmstBrl3. . . . . . . . . . 19

B. Open Containers. . . . . . . . . 20
l. Samarium Dibromide . . . . . 20

2. SmGBrlB. . . . . . . . . . . 21

3. SmSYBrl3 . . . . . . . . . . 21

4. SmSHfBrIB. . . . . . . . . . 21
Samarium Tribromide Hexahydrate. . . 22
Samarium Dibromide Monohydrate . . . 22
Yttrium Tribromide . . . . . . . . . 22
Single Crystal Preparation . . . . . 23
ELEMENTAL ANALYSES. . . . . . . . . . . . 23
Samarium Oxide Bromide . . . . . . . 23
Metal Analyses . . . . . . . . . . . 24
A. Conversion to Oxide. . . . . . . 24
B. Atomic Absorption Spectrosc0py . 24
Bromide Analyses . . . . . . . . . . 25
A. Volhard Titration. . . . . . . . 25
. 26

B. Atomic Absorption Spectrosc0py

iv

Chapter Page

x-RAY POWDER DIPPRACTION PATTERNS. . . . 26
IV RESULTS. . . . . . . . . . . . . . . . . 28
ELEMENTAL ANALYSES . . . . . . . . . . . 29

x-RAY POWDER DIFFRACTION ANALYSES. . . . 29
CALCULATION OF LATTICE PARAMETERS. . . . 31

SINGLE CRYSTAL PREPARATION . . . . . . . 36

v DISCUSSION . . . . . . . . . . . . . . . 37
VI CONCLUSION . . . . . . . . . . . . . . . 46
REFERENCES. . . . . . . . . . . . . . . . . . . . 49
APPENDICES. . . . . . . . . . . . . . . . . . . . 53

Table

II

III

IV

VI

LIST OF TABLES

Metal Halide Compositions Defined by the
Series Mnx2n+l . . . . . . . . . . . . .
Structural Information on the Samarium

Bromides . . . . . . . . . . . . . . . .

Analytical Results of Several Samarium
Bromide Phases . . . . . . . . . . . . .

Properties of Space Group C2/c . . . . .

Data on SmSYBrl3 . . . . . . . . . . . .

Comparison of Lattice Parameters of

Sm6Br13 and SmSYBrl3 . . . . . . . . . .

vi

Page

12

30
32

34

35

Figure

LIST OF FIGURES

Page
The Vernier Structures of SmSBrll,
SmllBr24 and Sm6Brl3 (As Outlined in
Table II). . . . . . . . . . . . . . . . 13
Samarium Bromide Preparation Apparatus . 1?
Representation of Space Group C2/c . . . 33
Projection of M6Xl3 on (001) (Space
Group IZ/a). . . . . . . . . . . . . . . 41
Metal Atom Coordination in the M6Xl3
Lattice. . . . . . . . . . . . . . . . . 43

vii

Appendix

A

LIST OF APPENDICES

The Positional and Thermal Parameters
Of smBrz O .0 O O O O O O C O O C O O I
The Positional and Thermal Parameters

of SmsBrll. . . . . . . . . . . . . .

The Positional and Thermal Parameters

of Sm6Brl3 and SmSYBr13 . . . . . . .

X-Ray Powder Diffraction Pattern of
Tetragonal SmBrz. . . . . . . . . . .

X-Ray Powder Diffraction Pattern of

Orthorhombic SmBrZ-HZO. . . . . . . .

X-Ray Powder Diffraction Pattern of
Orthorhombic SmBr3..a . . . . . . . .
X-Ray Powder Diffraction Pattern of
Monoclinic SmBr3-6H20 . . . . . . . .

X-Ray Powder Diffraction Pattern of
of Tetragonal SmOBr . . . . . . . . .

X-Ray Powder Diffraction Pattern of
Vernier SmsBrll . . . . . . . . . . .

X-Ray Powder Diffraction Pattern of
Vernier Sm6Br13 . . . . . . . . . . .

X-Ray Powder Diffraction Pattern of
Monoclinic YBr3 . . . . . . . . . . .

X-Ray Powder Diffraction Pattern of
Vernier SmSYBrl3. . . . . . . . . . .

X—Ray Powder Diffraction Pattern of
cubic HfBr4 O O O O O O O O O O O O 0

Least Squares Refinement of SmSYBrl3
Lattice Parameters. . . . . . . . . .

viii

Page

53

54

55

56

57

58

59

61

62

64

66

67

69

70

CHAPTER I

INTRODUCTION

INTRODUCTION

 

During the past decade the preparation and character-
ization of lower valence and mixed valence compounds have
received considerable attention. Much of the research
effort has been concentrated in the area of the rare earth
halides. Stable reduced valence metal halides have been

studied extensively and are reviewed by Corbett.l’2

Many
systems studied recently can be defined by a homologous
series MnX2n+l where M is a rare earth metal and X is a
halide. Compounds in the series exhibit a complex vernier-
type structure.

Several of the mixed valence rare earth halides have
been characterized and their structures determined by
single crystal x-ray structure analysis.3 Others have been
prepared as polycrystalline phases and the resultant struc-
tures determined from powder diffraction patterns. One
such system is the SmBrx system which has been studied in
detail by Haschke.4 He could not isolate Single crystals of
the compounds.

The inability to prepare single crystals of Yb6C1l3
was reported by Lfike and Eick.5 Single crystals of the
desired structure were obtained only after Er3+ was par-

3+ in the preparation. Erbium was

tially substituted for Yb
chosen for the system because its ionic radius was similar

to that of ytterbium.

3

The objective of this work was to study further the

SmBrx system, and more specifically the compound Sm Br .

6 13

As in the YbClX system, it was thought possible to prepare
and isolate single crystals of this structure if another ion
Of similar ionic radius was substituted for samarium in the
lattice. Substitution of a transition metal into the
lattice of a rare earth halide could result in the deter-
mination of the site symmetry of the trivalent and divalent
metal ions since the electron density of a first or second
row transition metal is significantly less than that of a
rare earth metal. The metals used in this investigation
were yttrium and hafnium. Attempts were made to prepare the
compounds SmSYBrl3 and SmstBrl3. X-Ray powder diffraction

analysis was used to determine if these compounds exhibited

the same structure as Sm63r13.

CHAPTER II

BACKGROUND AND THEORETICAL CONSIDERATIONS

PREPARATION OF RARE EARTH HALIDES

Rare Earth Trihalides

 

Aqueous solutions of rare earth trihalides can be
readily prepared. However, only highly hydrated products
separate from these solutions (uSually six moles of bound
water). Most of the water can be removed through dehydra-
tion at low temperatures but the last mole is difficult to
remove without decomposing the halide to the oxide halide.

In the past few years many methods have been developed
to produce relatively pure anhydrous rare earth trihalides.
Most of the preparative procedures involve the trichlorides.
Matignon6 first described the preparation of rare earth
trichlorides by dehydration of the hydrated trichloride with
HCl. The method is described in detail by Taylor.7 There
has also been extensive work done on the conversion of rare
earth oxides to trihalides. The general method for chlorin-
ation of oxides with SZCl2 and C12 was first reported near
the turn of the century.8 A modification of the same

procedure involves the use of thionyl chloride. Carbon

11

tetrachloride and phosqene12 have also been used to

convert rare earth oxides to trichlorides. Other rare earth
trichloride preparative procedures are outlined by Taylor.7
The chlorination of rare earth oxides with ammonium chloride
is reported by Domning and Schechter.13 High purity
trichlorides also have been prepared from the reaction of a

. . . l4
rare earth oxide and various amine hydrochlorides.

6

Fewer methods have been perfected for preparing anhy-
drous rare earth tribromides than exist for preparation of
the trichlorides. Borisov et al.15 prepared several rare
earth tribromides by reaction of the oxide with carbon and
bromine. While most of the procedures outlined above for
the preparation of the trichlorides can be adapted for the
preparation of the tribromides, the most successful and
widely used one is that described by Taylor and Carter.16
The procedure involves careful dehydration of the hydrated
tribromide in the presence of an excess of ammonium bromide.
Because of its acidic nature, the excess ammonium bromide is
believed to prevent hydrolysis of the rare earth tribromide.
Haschke and Eickl7 extensively studied the eur0pium bromide
system using a modification of the Taylor-Carter process.
Rare earth tribromides can also be prepared from the reac-
tion of a rare earth metal and an excess amount of mercuric

bromide at elevated temperatures.18

Rare Earth Dihalides.

Most of the work involving rare earth dihalides has
been done in the past twenty years. As in the case of the
trihalides, the dichlorides have received the most atten-

19

tion. Polyachenok and Novikov studied the thermodynamics

of the reaction

fl

3MC12(S)'—*-2MC13(S) + M(S) (1)
frheir calculations showed that many rare earth dichlorides

existronly in a metastable state.

7
Many ways have been used to reduce rare earth trihal-

ides to the dihalides. One method involves reduction of

the trihalide by hydrogen.20 Another technique, reported

by DeKock and Radtke,21

uses zinc as a reducing agent in

a zinc chloride melt. Whenever the dihalide is only
slightly stable toward disprOportionation the metal of the
cation involved is the most obvious and suitable reducing

agent. The procedure for the reaction

2MX3(1) + M(s,1)—-3MXZ(1) (2)

where X = Cl, Br, I

has been outlined by Corbett.2

Single Crystal Preparation
The preparation and growth of single crystals of rare

earth halides have been described by Cox and Fong22 and

23

Mroczkowski. These techniques involve very slow cooling

of a liquid melt.

Mixed Valence Rare Earth Halides

The preparation and characterization of rare earth
dihalides and mixed valence halide compositions have been
widely reported recently. Mixed valence rare earth halides
have been prepared either by reaction of the metal with the
trihalide or reaction of the trihalide with the dihalide.
The compounds were isolated from a melt which was
contained in reaction vessels of tantalum, gold, carbon or

quartz. Corbett and co-workers have done extensive work on

the systems MX<1 5, which exhibit a high degree of metal-

24 25

metal bonding. The compounds Gd C13, Sc2C13 and SczBr,

2
Sc7C11026 and ScCl27 have been isolated. The monochlorides

of gadolinium and terbium have also been prepared.28 The

crystal structures of the rare earth monochlorides are

sheet-like and are similar to the phases reported for ZrBr29

and HfC1.30

Some mixed valence halides exhibit vernier-type struc-

31

tures. Such structures were reviewed by Hyde et a1. and

were identified as the crystal structure for the compounds
32 33 34
Y706F9, Nb22r6017 and zr108N98Fl38'
An examination of the reported intermediate valence
phases shows that some compositions are consistent with an

Mnx2n+2 series. Reported compounds in this series include
4 35 36 37
SmllBr24, Lasllz, PrSBr12 and Yb6C1l4.
Mixed valence rare earth halides also exist as com-

pounds which can be assigned to the homologous series

M X The compounds in this series which have been

n 2n+1'
isolated and characterized are listed in Table I. Mixed-
metal rare earth halides that also belong to this series

3 5
have been reported. They are Sr4DyClll and YbSErCI13

where n = 5 and 6 respectively.

STRUCTURAL INFORMATION
Samarium Tribromide
A. Anhydrous Samarium Tribromide

Anhydrous samarium tribromide exists in the PuBrB-type

 

 

TABLE I: Metal Halide Compositions Defined
by the Series Mnx2n+l
Theoretical
in X:M Reported Compositions Ref.
3 2.333 NdC12.33’ PrC12.3l, SmFZ.35 39, 40, 41
4 2.250 NdC12.25, NdC12.27, YbClz.26 38, 39, 40
5 2.200 SmBr2.20, NdC12.20, SmC12.20, 4, 39, 43
DyC12.20, HoC12.20 43, 44
6 2.167 SmBr2.l72 4
9 2.111 DYC12.11’ TmC12.ll 45, 46
10 2.100 TmC12.lo 46
11 2.091 TmC12.090 46
12 2.080 TmC12.080 46
13 2.077 TmC120074 46
15 2.067 TmC12.067 46
25 2.040 TmC12.04O 46

 

10

structure and is isostructural with NdBr

TbBr3.47 The compound exhibits orthorhombic symmetry and

3, EuBr3 and

is consistent with space group Ccmm.

B. Samarium Tribromide Hexahydrate
Samarium tribromide hexahydrate is isostructural with
the NdCl3-6H20-type structure48 and the other rare earth
49

tribromide hexahydrates. The compound exhibits monoclinic

symmetry and is consistent with space group P2/n.

Samarium Dibromide

 

A. Anhydrous Samarium Dibromide

 

Anhydrous samarium dibromide is isostructural with
eurOpium dibromide which exhibits X-ray patterns that are
assignable to a tetragonal SrBrz-type structure.4

Systematic extinctions are consistent with space group P4/n.

B. Samarium Dibromide Monohydrate
Samarium dibromide monohydrate, which exhibits a

17 has not been

structure similar to that of EuBrZ-HZO,
prepared in pure form. X-Ray data for the compound assigns
it to space group ana with an orthorhombic BaClZ-HZO-type

structure . 4

11

Mixed Valence Samarium Bromides

The three compositions isolated in the SmBrx system
all exhibit a vernier-type structure with monoclinic
symmetry. Conditions for extinction show that SmsBrll and

SmllBr24 are assignable to space group 92. To facilitate

Br Sm Br

comparison of the structure with that of Sm ll' 6 13

5
has been indexed in Space group I2/a.
Structural information for the various samarium bromide
phases is detailed in Table II. The vernier structures of
the samarium bromide phases as deduced by Béirnighausen3 are
shown in Figure 1. Vernier structures are layered
structures with two metal atom layers (the open and filled

circles) and two anion layers (the solid and broken line

networks).

Yttrium Tribromide
Yttrium tribromide is isostructural with AlCl3 and
YCl3. X-Ray data shows the compound to be of monoclinic

symmetry and is indexable in the space group C2/m.

Hafnium Tetrabromide
Hafnium tetrabromide exhibits cubic symmetry.

Systematic extinctions are consistent with space group

Pa3.

12

 

gees

 

 

mane A>VmH.Hm ams.h mn.sv Hmo.a m\mH oflcfldoocos umflcum> mHHmSmSm
m L>Vom.aa ama.h «v.44 avm.a m\~H oacfiaoocoe umflcum> maumeem
m Imeaa.oa omH.a ~6.Hm mmm.a :\~a oflcndoocos uwflcum> amumaaam
m havem.oa HNH.~ H~.hm ~mo.a Exam oHcAHoocoe Hoficum> 2Swan.
4 mam.v -¢.HH Shaka mesa oflnsoeuozuuo Omm.maomm o~:.~umem
a ooH.~ mmm.HH :\vm decommuumu munum mumem
a .mcnm.mm mma.m ~ma.m mo.oH :\~a oficflaoocos O~m6.maoez Omme.mum2m
Se ama.a oon.ma mao.a sSoo canoszuoeuno mumsm mnmem
.mmm on>.m A<v 0 Adv n Amy M msouo auumEENm musuosuum mmwommm
o o o mommm
mmpfleoum Esfluwamm mnu co cofiumfiuomcH amusuosuum "HH mamme

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure I

From Top to Bottom: The Vernier Structures of Sm5 Br,1 , Sm11 Br?4 and Sm6 Br13

(As Outlined in Table II)

CHAPTER III

EXPERIMENTAL PROCEDURES

14

CHEMICALS AND MATERIALS

The chemicals and materials used were: (a) samarium
oxide and yttrium oxide, 99.9%, Michigan Chemical Corp., St.
Louis, MI; (b) samarium metal, samarium bromide, yttrium
bromide, 99.9% and hafnium bromide, 98%, Cerac/Pure Chemical
Co., Milwaukee, WI; (c) hydrobromic acid, 48% aqueous
solution, Fisher Scientific Co., Fair Lawn, NJ; (d) ammoni-
um bromide and ferric ammonium sulfate, reagent grade,
Matheson, Coleman and Bell Chemical Co., Norwood, 0H; (e)
silver nitrate and potassium thiocyanate, reagent grade,
3: T. Baker Chemical Co., Phillipsburg, NJ: (f) argon, Air
Reduction Co., New York, NY; (g) vitreous carbon combustion
boats, Beckwith Carbon Co., Van Nuys, CA; and (h) quartz

tubing, Corning Glass Works, Corning, NY.

HANDLING PROCEDURES

The handling and storage of air and moisture sensitive
materials such as SmBr3, YBr3, Sm, HfBr4, and the mixed
valence bromides were performed in a recirculating argon-

50 has described the glove

atmosphere glove box. Hariharan
box in detail. All weighings were done in the glove box.
Samples were tranSported outside the glove box in evacuated

. ®
Schlenk tubes or protected by a covering of Parafilm M.

PREPARATIVE PROCEDURES
Anhydrous Samarium Tribromide
Samarium tribromide was prepared according to a

15

l6
modification of the method of Taylor and Carter.16 The

overall reaction is as follows:

Sm O

2 3 + 6HBr(,aq)

 

2[SmBr3-6H20-xNH4Br]
NH Br (3a)

(excess)

A
SmBr3-6H20-xNH4Br =:SmBr3 + 6H20(g) + xNH4Br(g) (3b)

Ar,Vac

One gram of oxide was added to a 15 ml volume of 48%
hydrobromic acid in a 150 ml beaker. The solution was
heated on a hot plate and stirred until it became clear.
Ammonium bromide (3.5 g) was added in a 13:1 molar ratio of
ammonium bromide to metal ion. The mixture was heated to
boiling until all the solids dissolved. The hot Solution
was transferred to a porcelain evaporating dish and heated
to dryness. The resultant cream-colored powder was trans-
ferred to a vitreous carbon combustion boat and placed in
the apparatus shown in Figure 2.

The sample was purged with dry argon for 30 minutes
and heated to 200°C for 30 minutes. The temperature was
increased in one hundred centigrade degree increments each
hour up to 600°C. The sample was cooled to room tempera-
ture and heated to 500°C for one hour under a pressure of

-4 to 10"5 torr. The sample was cooled, and transferred

10
to an argon-filled Schlenk tube. The tube was evacuated
and transferred to an argon-filled glove box where the

sample was stored in a screw-capped glass vial.

17

3859? c2559... 62:55 5235mm

3.2% m «SET
.5 28:5

fish‘s-”Pd”...

i .
Q J as: 2.222.. :7 3

LP 1

  

J

_ rig hi confine F 1.. 52
will . LU“

 

 

 

 

 

 

 

 

 

 

  

 

 

 

 

 

 

 

 

 

 

(

 

 

 

18

Reduced and Mixed Valence Samarium Bromides

A. Sealed Containers

 

l. Samarium Dibromide

 

Anhydrous samarium dibromide was prepared according to

the following reaction:
Sm + ZSmBr3-———---3SmBr2 (4)

A 0.165 9 sample of -40 mesh samarium metal and a 0.840 g
sample of anhydrous samarium tribromide were placed in an
outgassed 8 x 120 mm quartz ampoule. The ampoule, after
evacuation, was sealed with an oxygen-methane torch.

The sealed ampoule was placed in a horizontal tube
furnace, heated to 800°C for a period of up to five hours,
and annealed at 450°C for five hours. -The ampoule was
agitated periodically to insure homoqeneity of the melt.
The ampoule was cooled, transferred to a glove box, and the
contents examined. The gray-black powder product was

stored in a snap—capped glass vial in the glove box.

2. SmGBrl3

Mixed valence samarium bromide was prepared in a
manner similar to that described for preparation of samarium

dibromide. The reaction proceeded according to the follow-

ing stoichiometry:

5 13 .-
-3-Sm + —-3-SmBr3 -—'-Sm6Brl3 (J)

19

A 0.129 9 sample of samarium metal was mixed and allowed
to react with a 0.871 9 sample of anhydrous samarium
tribromide.

The resultant product was a fused black mass which

exhibited a gray-black color when crushed.

3. SmsYBrl3

Samarium yttrium bromide was prepared in a manner
similar to that described for preparation of samarium
dibromide. Samarium metal, samarium tribromide and yttrium
tribromide were reacted in evacuated, sealed quartz ampoules

in the following stoichiometry:

5 10 '
38m + —§--SmBr3 + YBr3 SmSYBrl3 (6)

A 0.147 g sample of samarium metal was allowed to react with
a mixture of 0.692 g samarium tribromide and 0.174 g

yttrium tribromide.

The resultant product was a fused black mass that was

gray-green to gray-black in color when ground.

4. SmSHfBrl3

An attempt was made to prepare samarium hafnium bromide
according to the procedure outlined for the preparation of
samarium dibromide. A sample of 0.153 g samarium metal,

(3.593 g samarium tribromide and 0.253 g hafnium tetrabromide

was allowed to react according to:

20

2Sm + 3SmBr + HfBr —--Sm HfBr

3 4 5 13

The resultant fused black powder exhibited a gray-black
color when crushed.

Since the quartz reaction vessels were potential
samarium metal scavengers, slight stoichiometric excesses

of metal were used routinely.

B. Open Containers
l. Samarium Dibromide
Sealed quartz ampoules proved inadequate for the
preparation of reduced and mixed valence samarium bromides

due to formation of samarium oxide bromide:

2SmBr3 + Si02'-—-*-ZSmOBr + SiBr4 (8)

The reaction is discussed in detail by Corbett.51

Samarium dibromide, without oxide bromide contamina-
tion, was prepared in the following manner. A mixture of
0.165 g samarium metal and 0.840 g samarium tribromide was
placed in a vitreous carbon combustion boat and a tantalum
foil cover was tightly fitted over the boat. The boat was
placed in a horizontal tube furnace, heated to 700°C for one
hour under an argon pressure of one atmosphere, and annealed
at.450°C for four hours. The product was cooled and trans-
ferred to a glove box. The resultant dibromide was a fused

tslack mass which was gray-black in color when ground.

21

2. Sm6Br13

 

Mixed valence samarium bromide was prepared in vitreous
carbon combustion boats by a procedure similar to that used
for the preparation Of samarium dibromide. A mixture of
0.128 g samarium metal and 0.869 g samarium tribromide was
allowed to react to form a fused black mass of Sm6Brl3

which was gray-black in color when crushed.

3. SmsYBrl3

Samarium yttrium bromide was prepared in vitreous
carbon combustion boats according to the procedure used in
the preparation of samarium dibromide. A mixture of 0.397 g
samarium metal, 2.078 g samarium tribromide and 0.520 g
yttrium tribromide was heated to 950°C for 15 minutes, 800°C
for 1 hour, and annealed at 450°C for five hours. The
resultant black fused product was gray-black in color when

ground.

4. SmSHfBrl3

An attempt was made to prepare samarium hafnium bromide
according to the procedure outlined for the preparation of
samarium dibromide. A mixture of 0.154 g samarium metal,
0.596 g samarium tribromide and 0.253 g hafnium tetrabromide
was allowed to react to form a fused black mass which was

gray-black in color when ground.

22

Samarium Tribromide Hexahydrate

Hydrated samarium tribromide was prepared from the
anhydrous tribromide. The anhydrous cream-colored tribro-
mide was exposed to air at room temperature for 24 hours.
The resultant white product was determined by X-ray powder

diffraction to be SmBr3-6H20.

Samarium Dibromide Monohydrate

Hydrated samarium dibromide was prepared in a manner
similar to that described by Haschke.4 Black, anhydrous
dibromide was exposed to air for a short period of time. The
resultant monohydrate was red in color. Extended exposure
of the monohydrate to atmospheric moisture resulted in the

formation of the white, hydrated tribromide.

Yttrium Tribromide

Yttrium tribromide was prepared in a manner similar to
that described for the preparation of anhydrous samarium
tribromide. A 2 9 sample of Y203 was dissolved in a 30 ml
volume of 48% HBr. The solution was heated and a 7 9
sample of NH4Br was added. The resultant yellow solution
was transferred to a porcelain evaporating dish and heated
to dryness. The dry, white powder was transferred to a
vitreous carbon combustion boat and heated in the apparatus
shown in Figure 2. The product was heated according to the

:schedule previously described for the preparation of

ainhydrous samarium tribromide.

23

Single Crystal Preparation

Single crystals of SmsYBrl3 were prepared upon crys-
tallization of a liquid melt upon slow cooling.

A sample of 0.147 g samarium metal, 0.695 g samarium
tribromide and 0.174 g yttrium tribromide was sealed under
vacuum in an outgassed quartz ampoule, heated to lOOO°C for
one hour and cooled to 675°C over a period of several days
at a rate of 5°C/hour. The sample was then cooled to room
temperature at a rate of 100°C/6 hours. The ampoule was
transferred to a glove box, broken Open and the gray product
was lightly crushed. Examination of the product showed the

existence of single crystals.

ELEMENTAL ANALYSES

Samarium Oxide Bromide

All bromide samples were analyzed for oxide bromide
content. A l 9 sample of soluble bromide was dissolved in a
100 m1 volume of water and the resultant mixture was acidi-
fied to pH 3-4 with 6 M nitric acid. The solution was
stirred and filtered through a weighed, dry, glass-fritted
weighing crucible. The crucible was heated to 300°C for
four hours to dry the SmOBr.

The filtrate was saved and used for metal and bromide

analyses.

24

Metal Analyses
A. Conversion to Oxide
All unsubstituted samarium bromides were analyzed for
samarium content by firing the bromide to the oxide,
e.g.:
ZSmBrX + %OZ-—-*-Sm O + xBr

2 <9)

2 3

A 0.5 g sample of samarium bromide was placed in a weighed,
dry, procelain crucible. The crucible was fired to 900°C in
a muffle furnace for six hours and cooled to room tempera-
ture. The crucible was reweighed and the amount of szo

3
formed was determined.

B. Atomic Absorption Spectroscopy

 

Transition-metal-substituted bromides and selected
samarium bromides were analyzed for metal content by atomic
absorption spectroscopy. Analyses were performed on a
Perkin-Elmer instrument located in the 1602 Building Analyt-
ical Lab of the Michigan Division of The Dow Chemical
Company, Midland, MI. All metals were analyzed using a
reducing nitrous oxide-acetylene flame. Samarium was ana-
lyzed at 429.7 nm wavelength, yttrium at 410.2 nm and
hafnium at 307.3 nm. Samarium and yttrium were partially
ionized by a nitrous oxide-acetylene flame. Potassium
nitrate solution was added at a concentration of 2000 ppm
and 4000 ppm, respectively, to suppress ionization.

Ionization of hafnium was minimal.

25

Bromide Analyses

Samarium bromide products were analyzed for bromide
content by precipitation titration with silver nitrate and
ferric ammonium sulfate or by atomic absorption

SpectrOSCOpy.

A. Volhard Titration

The Volhard method is applicable for the determination
of bromide in acid solution. The method is based on the
insolubility of silver thiocyanate and uses ferric ion as
the indicator to show when excess thiocyanate is present.

In the analysis a measured excess of standard silver
solution is added to a bromide sample and the excess silver

is titrated by a standard solution of thiocyanate:

 

 

Ag+ (excess) + Br- AgBr + Ag+ (10)
Ag+ + SCN‘ AgSCN (11)
Pe3+ + 65CN'———-Pe(SCN)2' (red) (12)

A 0.1 9 sample of soluble bromide was dissolved in a 50 ml
volume of water. The solution was acidified to pH 3-4 with
1:1 nitric acid. A 25 ml volume of 0.1 M silver nitrate was
added to the solution and the resultant mixture was titrated
with 0.1 M potassium thiocyanate. Several drops of a
saturated solution of ferric ammonium sulfate in 1:1 nitric

acid was used as the indicator.

26

B. Atomic Absorption Spectroscopy

All samarium bromide products were analyzed for bromide
content by atomic absorption SpectrOSCOpy. Analyses were
performed on a Varian Techtron instrument located in the
Larkin Lab Building of the Central Research Inorganic Labo-
ratory of The Dow Chemical Company, Midland, MI.

Bromide was analyzed by atomic absorption spectroscopy
in a manner similar to that used in a Volhard titration;
determination of excess silver added to a bromide solution.
The excess silver was analyzed using an oxidizing air-
acetylene flame at 338.3 nm wavelength. The presence of

' other halides interferes with the analyses.

X-RAY POWDER DIFFRACTION PATTERNS

 

Powder diffraction patterns of the various products
were obtained using a Guinier focusing x-ray powder dif-
fraction camera equipped with a fine focus copper X-ray
tube (An = 1.54050 A). The camera had an effective radius
of 80 mm. Platinum powder (a = 3.9237:o.ooo3 A) was includ-
ed in the samples prepared for powder diffraction analyses.
The interplanar d-spacings of the powder patterns were based
on this platinum standard.

Both a sample and a small amount of platinum powder
were secured to an X-ray planchet (a steel disc with a 5 mm
hole in the center) with amorphous transparent tape and

. ® . . . . .
covered with a piece of Parafilm M barrier film to minimize

hydrolysis, which occurred upon prolonged exposure to air.

27

The planchet was placed in the X-ray holder, a magnet revolv-
ing at 50 rpm, with the back side of the tape against the
magnet. The film cassette, which contained a 20 x 140 mm
strip of Ilford Type G Industrial X-ray film encased in two
sheets of black paper to prevent light exposure, was placed
on the pin point triangular support of the camera box. The
incident beam stop on the camera was opened, the camera box
closed for safety purposes, and the shutter on the X-ray
tube was Opened for ten seconds to expose the film to the
incident beam. The beam stOp was closed and the camera box
was evacuated with a mechanical pump. The films were ex-
posed to X-rays for six to twelve hours (35 kv at 20 ma,
Picker Nuclear x-Ray Generator). Two noncoincident images
were recorded on the film due to the sharp lines obtained
and the angle of intersection of the diffracted beam with
the film. Since an image was recorded on both sides of the
film, one layer of film emulsion had to be removed. This
was accomplished with a small wire brush after the film had
been densensitized by a fixing solution.

The diffraction lines on the film were measured pre-
cisely, to the nearest 0.001 inch, using a vernier-type

2

film reader. Sin 8 and d-spacing values were calculated from

obServed data. Powder diffraction patterns were also

calculated by a modification of the program, ANIFAC, prepared

52

by Larson et al. All cell parameters for the compound

were calculated from the powder diffraction pattern
53

SmSYBr13

by least squares regression analysis (Program Guinier).

CHAPTER IV

RESULTS

28

ELEMENTAL ANALYSES

 

All prepared phases were analyzed for metal and bromide
content. Corrections were made for SmOBr formation. Sample
contamination by the oxide bromide was generally less than
one percent by weight. The analytical results of several
samarium bromide phases are outlined in Table III.

Prepared samples of the phase Sm HfBr

5 13 showed an ab-
sence of hafnium metal when analyzed by atomic absorption

SpectrOSCOpy.

X-RAY POWDER DIFFRACTION ANALYSES

 

Some assumptions were made in'the X-ray powder dif-
fraction analyses of several samarium bromide phases. The
positional parameters used in the ANIFAC determination of

an SmBr2 powder pattern were those obtained for a similar

compound, SrBr2.54 The powder pattern of SmSBrll was calcu—

lated from the positional parameters obtained for DySClll.3

The thermal parameters of DySClll were modified for SmSBrll
due to density differences of the atoms. The powder

patterns of Sm6Brl3 and SmSYBr13 were calculated with the

positional parameters obtained for YbSErC1.5 The positional

parameters of Sm6Brl3 and SmSYBrl3 were corrected from those

5
5 13

parameters were used for the powder pattern calculations

of Yb ErCl by x-1/4; y-l/4; and z. Isotropic thermal '

since the program ANIFAC would not evaluate anisotropic

thermal parameters. The positional and thermal parameters
used in the x-ray powder diffraction analyses of various

29

30

 

 

 

.coHuucHEmucoo umOEm MOM pwuomuuoo coon U>m£ muasmmu dads
mH.OHos.Ho In- so.oflhm.mm ov.am In- sm.mm mumSm
~H.OHsa.mm mo.oamn.v om.onam.om a~.mm mn.e oo.ov maumSmsm

. - . . - . . . mu S
OH o+mo mm .t: we o+~m we mm mm In- we we um Sm
«H.0HON.Hm ls: mo.ofima.ma mm.Hm In: ne.aa mumEm

Haw SW Ems umw we Smw mmmea
Ranches emumdsonO
mommnm mpflsoum Esflumsmm Hmum>mm mo muasmmm HMOfluhaucd "HHH mqmda

31

samarium bromide phases are listed in Appendices A, B and
C.

Samarium yttrium bromide was indexed in Space group
C2/c for all X-ray powder diffraction intensity and lattice
parameter calculations. The properties of space group C2/c
are listed in Table IV. A representation of the symmetry
of this space group is illustrated in Figure 3.

The X-ray powder diffraction patterns of all prepared

compounds are outlined in Appendices D-M.

CALCULATION OF LATTICE PARAMETERS

 

The lattice parameters of the compound, SmSYBr13, were
refined by a least squares regression analysis. The crystal
was of a monoclinic symmetry with a c-centered lattice.

The refinement was based on the indexed reflections of the
X-ray powder diffraction patterns. For the final calcula-
tion 58 reflections were used. The refined constants ob-
tained were then used to calculate sinze values. The
result of the least squares refinement of the SmSYBrl3
lattice parameters is detailed in Appendix N.

The data obtained for SmSYBrl3 are listed in Table V.
As previOusly mentioned, the lattice parameters of Sm6Brl3
calculated by Béirnighausen3 are likewise based on powder
diffraction photographs. A comparison of the lattice param—
eters of Sm6Brl3 is shown in Table VI. All parameters are

based on the assignment of the compounds to space group

C2/c.

32

 

 

TABLE IV: Properties of Space Group C2/c55
Point Coordinates of
Positions Symmetry Equivalent Positions
(010107 é‘r‘li'rq) +
8f 1 x,y,z; 355.5; X.y.-12- 2;
l — 3
4e 2 OIYI-4-l Oly1-4-
_. l l l. 2 l 0
4d 1 4I4I2I 4’4,
,— 3 1 1
4c 1 %,%-,0; TI"?
1 1
4b 1— 01%10; Gift?
_ 1
4a 1 0:010! 0:017

 

V4

V4

V.

‘A

74

V2+O

‘/2+Q

33

 

 

 

 

 

 

 

 

OVz- -O
0* ‘/=+®
'0 0V"

V=+O 0+
014- -O
0" '/2+®
P , 1% I P
i I i | i
: o : o :
I I : l :
<5 } Q : Q
l | '
s <:> z A 5
2t . I l s
Figure3

Representation of Space Group C2/c55

CV:-

072-

V.

V.

V4

34

TABLE V:
Data on SmSYBrl3

 

Space Group C2/c
Unique axis 2
O
a (A)* 44.31i0.05
O
Q (A) 7.139t0.008
0
g (A) 6.651t0.008
Q (°) 98.45:0.007
°3
Z (A ) 2394
.2. 4
Formula Weight 1897.5
D (g/cm3) 5 21+0 03
calc ° ‘ '
t (°C) 23:3
0
A (A) 1.54050
General positions (x,y,z)
(i)
(x,% - 1.2)

Glide at z

'1

('2‘ + xI-XIZ + Z)

Glide at y = 0.25
= 0.25

 

*Least squares fit.

35

TABLE VI: Comparison of Lattice Parameters*

of SmGBrl3 and SmSYBr

 

43

 

Parameter .SmGBrIB SmsYBrl3
a (A) 43.97i0.08 44.31:o.os
p (A) 7.139:o.ooz 7.139:0.008
g (A) 7.649t0.002 7.651:0.008
5 (°) 98.58:0.07 98.45:o.o7

-3
. 2 5.21:0.03
Dcalc(g/cm ) 5 34
2 (A3) 2401 2394

 

*Space group C2/C

SINGLE CRYSTAL PREPARATION

A mixture of SmBr3, Sm and YBr3 was melted in a sealed,
evacuated, quartz vessel and slowly cooled. The resultant
product was crushed and examined visually under a micro-

scope. The product included gray polycrystalline material

and rectangular-prismatic crystals.

35

CHAPTER V

DISCUSSION

37

DISCUSSION

 

Unusual intermediate valence rare earth halides are
well known. One such system that has been recently char-
acterized is the SmBrx system.4 Reported compositions
include SmSBrll, SmllBr24 and Sm63r13. Two of the compounds
are defined by a well-studied homologous series, Mnx2n+l’
of rare earth halides. All of these compounds can also be
described as members of the series Mnx2n+2 where n = 10, 11
and 12, respectively.56 A major problem in studying mixed
valence rare earth halides has been the inability to produce
single crystals. Consequently, the lattice parameters of
these compounds have been solved from the X-ray powder dif-
fraction photographs of polycrystalline samples. Single'
crystals of DySClll were produced but they could not be
Obtained in the YbClX or SmBrx systems. Single crystals of
an intermediate valence ytterbium chloride were obtained as
a mixed-metal phase. The resultant compound, YbsErCll3, was
characterized by single crystal techniques and shown to be
isostructural with the desired ytterbium phase. It is
possible that substitution of another metal into the SmBrx
lattice could also result in single crystal formation.

The close similarity between the ytterbium chloride,
dysprosium chloride and samarium bromide systems can be
understood by a simple radius-ratio argument. A comparison
of the ionic radii of Cl/Yb and Br/Sm indicates a ratio of

57

1.84 and 1.80, reSpectively, when the trivalent ions, with

coordination number eight, are used for the rare earths.

38

39

The use of divalent rare earth radii should result in
comparably identical ratios. The Cl/Dy ratio of 1.75 is
similar to the Br/Sm value. Similarities among ratios can
be expected elsewhere in the rare earth series, particularly
among the bromide and iodide systems.

Mixed-metal rare earth halides have only been reported
in isolated cases. As previously mentioned, such systems
have resulted in excellent single crystal formation.
Looking at the SmBrX system several metals could be substi-
tuted into the crystal lattice. One such metal is yttrium.
Trivalent yttrium, with an coordination number of eight has

0
an crystal radius of 1.02 A.57

The resultant Br/Y ratio is
1.90. The samarium-yttrium-bromide system is unique in that
no transition metal has yet been substituted into the struc-
ture of a mixed valence rare earth halide. The compound

3

Sr DyClll has been reported but the substituted metal,

4
strontium, is not a d-block metal and the rare earth,
dysprosium, is not in a reduced valence state. The most
interesting feature of yttrium, and some other transition
metals, however, is their significantly lower electron
density than the lanthanide metals. Incorporation of yttri-
um into the samarium bromide lattice should allow detection
by X—ray analysis, of an ordered structure, if one exists.

. . + 3+ . .
Presently, distinction between the M2 and M Sites in the

lattice cannot be made.

Another possible metal substitute is hafnium. Hafnium

usually exists in the tetravalent state with an effective

40
radius of 0.83 A. Trivalent hafnium has been reported, as
HfI3.58 The radius of trivalent hafnium is expected to be
larger than 0.83 A and may yield a Br/Hf ratio similar to
that seen for samarium and yttrium. The use of a bromide
system may also help to stabilize hafnium in the trivalent
state.
and Sm HfBr

l3 5 13’
exhibit structures similar to those reported for Dy5C1

The proposed compounds, SmSYBr should

ll'
Sm6Brl3 and YbSErCll3. These compounds apparently belong to

a class of vernier-type structures. This structure type has

. . 32 33
also been isolated in the compounds Y706F9, NbZZrGOl7
and zr108N98F138’34 and is discussed in detail by Hyde et
al 31

The vernier structures are of monoclinic symmetry. The
structures are fluorite-type lattices. Compared to the
fluorite structure, however, vernier unit cells contain
additional anions, and the space required to accommodate
these extra anions is obtained by transforming one half of
the cubic anion packing into a hexagonal Closest packing.
Superimposition of these two anion layers leads to a ver-
nier-type structure. For discussion purposes it is easier.
to visualize the structure in space group I2/a. A projec-
tion of the M6Xl3 structure on (001) in such an orientation
is shown in Figure 4. In this projection the metal atom ar-
rangement in a fluorite lattice can be seen. The anion ar-

rangement consists of two layers of atoms at z = 1/4 and z -

3/4. The lower layer is rectangular between y 0 and

ER. 955 33m.
:8. co axes. ao 528.95

V 633.4

 

R
\
. \
I
r
A
/
\
\

(.3...

l

41

\

 

I

«I— —-O-

\
\

-9.-.
o.

 

 

/

 

 

 

'\ '-""-\

 

 

 

 

vv---'\"'--'-\

1...... _.

 

 

 

/
§

 

 

 

«\.u>

42
y = 1/2, and the upper is a triangular net; the arrangement
is reversed between y = 1/2 and y = 1. This arrangement
allows for the space needed to accommodate the two extra
anion rows. The Open and filled circles indicate the posi-
tion of the metal atoms at z = 0 and z = 1/2, respectively.

The anion coordination around the metal atoms is illus-
trated in Figure 5. One half of the unit cell is shown.
The coordination around Ml can be regarded as a capped
octahedron. The M2 Site coordination may be regarded as a
trigonal base-tetragonal base. A bicapped trigonal-pris-
matic coordination is observed surrounding M3. The struc-
tures of SmSYBrl3 and SmSHfBrl3 are expected to be similar
to that of the detailed M6xl3 structure. Single crystal
analyses of the two compounds may result in identification
of the positions occupied by divalent and trivalent metal
atoms.

The compound SmSYBrl3 can be prepared from a homogenous
melt of samarium metal, samarium tribromide and yttrium
tribromide. The reaction can be carried out in quartz
reaction vessels but a high degree of product contamination
by oxide bromide occurs. Quartz is also a samarium metal
scavenger. A more suitable and practical reactor material
is vitreous carbon. Haschke4 used carbon to prepare the
mixed valence samarium bromide phases. A modification Of

his procedure proved effective in the preparation of

SmSYBr13.

700-800°C under high vacuum (<10-4 torr). This preparation

The SmBrx preparation involved a reaction at

43

 

 

 

8.3....— n.

x as. 65 E cozacfitooo EOE .865.

m expat

x1

 

l
1

A
U

f .

-——-—---y‘ ———----
i
i
I w:
l
I
l
l

 

 

 

 

 

 

 

 

44

resulted in large losses of the tribromide through subli-
mation. Tribromide loss was minimized by heating the
samarium-yttrium-bromide system under a one atmosphere
pressure of dried argon.

The procedure used in the preparation of SmSYBrl3 was
not effective in the preparation of SmSHfBrl3. Hafnium
tetrabromide sublimes at 420°C (one atmosphere pressure).
Open containers of vitreous carbon proved unsuitable for
preparation of this phase. The samarium hafnium bromide,
likewise, could not be prepared in sealed quartz reactors.
The unsuccessful attempts to produce SmstBrl3 may be at-
tributed to the inability to reduce hafnium to the trivalent
state. The use of hafnium metal to form HfBr3, with the
subsequent reaction with samarium, may lead to formation of

Sm HfBr Samarium in the lattice exists in the divalent

5 13'
state and could be produced separately (according to equa-

tion (4)) or £3 bitu.

l 3
1 2 5 10 14
-H4 f + 4HfBr4 + jSm + —§SmBr3 -—---Sm5HfBrl3 ( l

The compound SmsYBrl3 can be indexed in either the C2/c
or I2/a space group. Lattice parameters calculated by
least squares linear regression indicate SmSYBrl3 is iso—
structural with Sm63r13. Examination of the parameters
shows the respective unit cells to be almost identical in

3+ °
size. Since the radius Of Y3+ is smaller than Sm (1.02 A

45

0
compared to 1.09 A) lattice parameters for SmSYBr13 would be

expected to be slightly smaller than those of Sm Br This

6 13'
size difference could also account for a Slight decrease in
the 8 angle.

A secondary objective of this work was to determine the
ability of isolating single crystals of transition-metal-
substituted samarium bromides. The ability to obtain Single
crystals supports the assumption that transition metals can
be substituted into a stable, vernier lattice. The limit of
non-lanthanide metal substitution is left to speculation.
The information Obtained in the growth of SmSYBrl3 single

crystals could be extended and adapted to other intermediate

valence rare earth halide phases.

CHAPTER VI

CONCLUSION

46

CONCLUS ION

 

The purpose of this work was to investigate a mixed
valence rare earth halide. The system chosen was the

vernier-structured compound, Sm Br

6 13’ Since single crystals
'of this compound had not been isolated, one of our goals was
to produce a substituted samarium bromide that could be
prepared in the form of single crystals. WOrk in the
ytterbium chloride system5 yielded single crystals after
some substitution was made of another metal, with an ionic
radius similar to ytterbium, into the crystal lattice.

On the basis of the ionic radius of Sm3+, r = 1.09 A,
two metals were chosen as possible candidates; Y3+ where
r = 1.02 A and hafnium. Hafnium normally exists in the
tetravalent state, r = 0.83 A, but the existence of triva-

58 Trivalent hafnium should

0
have an r > 0.83 A and may approximate the radius of Sm3+.

lent hafnium has been reported.

It was felt that the bromide ion in the system and the

3+. Transition metals,

lattice energy might stabilize Hf
rather than rare earth metals, were chosen. The substitu-
tion of transition metals into the lattice of a rare earth
halide may allow detection of an ordered structure if one
exists. Also, the incorporation Of transition metals into
the vernier structure of rare earth halides has not been re--
ported.

The unique compound, SmSYBrl3 was prepared by reacting

samarium metal with a mixture of samarium and yttrium

tribromides at a temperature greater than the melting point

47

48

of the tribromides. The gray—black powder was analyzed by
X-ray powder diffractometry. Least squares refinement of
the powder pattern yielded unit cell lattice parameters
comparable to those reported for Sm6Br13. The vernier
structure of SmSYBrl3 was also confirmed.

The attempts to produce Single crystals of a transi-
tion-metal-substituted samarium bromide were successful.
Growth of single crystals by the Slow cooling of a homoge-
neous melt in quartz reactors was confirmed by microscopic
observation. The crystals were of a rectangular-prismatic
shape. Atomic parameter refinement of single crystals of
Sm YBr

5 13
All attempts to prepare Sm

Should be an objective for future research.

HfBr from samarium metal,

5 l3
samarium tribromide and hafnium tetrabromide were unsuc-
cessful. The inability to isolate this compound may be a
result Of the failure to reduce hafnium to the trivalent
state. It might be possible to prepare the SmSHfBr13 phase
if hafnium metal is used to initiate reduction of
tetravalent hafnium.

The ability to prepare and characterize the phase

Sm YBr has led to an increase in the understanding of the

5 13
structural aspects of mixed valence rare earth halides.
The success of substituting another metal into the system
to stabilize the lattice as well as the use of trivalent

transition metals should lead to fruitful new areas of

research.

REFERENCES

10.

ll.
12.
13.

14.

15.

16.

17.

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s

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R.9A§)Sallach and J. D. Corbett, Inorg. Chem., 2, 457
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(1969).

 

APPENDICES

Appendix A:

The Positional and Thermal
Parameters of SmBr2*

 

 

Atom x y z B(£2)**
Sm(1) 0.1045 0.5856 0.2476 2.15
Sm(2) 0.2500 0.2500 0.8483 1.25
Br(1) 0.1531 0.4590 0.6258 3.33
Br(2) 0.3388 0.4572 0.0963 2.43
Br(3) 0.2500 0.7500 0.0000 2.90
Br(4) 0.2500 0.7500 0.5000 2.44

 

*Based upon SrBr2

**Estimated

53

Appendix B:

The Positional and Thermal
Parameters of Sm Br *

 

 

 

5 ll
Atom x y z B(A2)**
Sm(1) 0.3343 0.44475 0.0232 1.43
Sm(2) 0.7404 0.34558 0.0138 1.38
Sm(3) 0.3285 0.25000 0.0156 1.31
Sm(4) 0.8351 0.44492 0.4711 1.31
Sm(S) 0.2439 0.34504 0.4795 1.42
Sm(6) 0.8352 0.25000 0.4797 1.07
Br(1) 0.6100 0.49107 0.2317 2.05
Br(2) 0.6577 0.41724 0.8107 2.21
Br(3) 0.5353 0.39504 0.3037 2.05
Br(4) 0.3733 0.33080 0.8728 1.94
Br(5) 0.5453 0.29628 0.3144 1.52
Br(6) 0.6887 0.25000 0.8596 3.20
Br(7) 0.1035 0.49212 0.2732 2.52
Br(8) 0.1499 0.41714 0.6738 1.89
Br(9) 0.0247 0.39582 0.1938 1.69
Br(10) 0.1164 0.32758 0.6312 2.37
Br(ll) 0.0305 0.29662 0.1885 1.40
Br(12) 0.1979 0.25000 0.6093 2.46
*Based upon DySClll§
**Estimated

54

Appendix C:

The Positional and Thermal Parameters

 

 

of SmsBrl3 and SmSYBrl3*
Atom** x y z 3(AZ)***
Sm(1) 0.4542 0.2747 0.8750 1.32
Sm(2) 0.3705 0.2718 0.4010 1.32
Sm(3) 0.2900 0.2684 0.7407 1.32
Br(1) 0.4925 0.4816 0.6367 2.11
Br(2) 0.4307 0.0696 0.5347 2.11
Br(3) 0.4122 0.4452 0.1516 2.11
Br(4) 0.3555 0.1059 0.7419 2.11
Br(5) 0.3299 0.4400 0.0693 2.11
Br(6) 0.2838 0.1193 0.3678 2.11
Br(7) 0.2500 0.4413 0.0001 2.11

 

*Based upon YbsErCll3

. . l
**Corrected POSitional Parameters are x - %; y - 7; z - I

***Estimated

55

Appendix D:

X-Ray Powder Diffraction Pattern
of Tetragonal SmBr

2

 

O
d-value (A)

 

Observed
h h Calculated -Observed Intensity
1 1 8.1940 8.1011 w
0 0 3.5500 3.5627 m
0 1 3.3943 3.3936 0w
1 1 3.2574 3.2170 vw
1 2 2.9287 2.9339 w
0 3 2.6138 2.6111 w
2 4 2.5912 2.5843 w
l 3 2.5497 2.5477 w
2 4 2.4341 2.4314 vw
1 4 2.2035 2.2149 m
l 2 2.1528 2.1527 uw
2 5 2.0593 2.0584 w
4 5 1.6123 1.6138 m

 

56

Appendix E:

X-Ray Powder Diffraction Pattern

 

 

of Orthorhombic SmBrZ-HZO
,1

d-value (A) Observed
h k 8 Calculated Observed Intensity
2 0 0 4.5890 4.5821 w
l 2 1 3.2239- 3.2289 w
2 0 1 3.1436 3.1376 vw
3 0 0 3.0593 3.0771 w
2 l 1 3.0310 3.0452 w
3 1 0 2.9552 2.9533 w
0 3 1 2.8556 2.8785 vw
2 2 1 2.7542 2.7826 w
3 2 0 2.6970 2.6703 w
3 0 1 2.4957 2.5097 m
3 1 1 2.4382 2.4493 vw
0 0 2 2.1575 2.1573 vw
0 1 2 2.1200 2.1208 vw

 

57

Appendix F:

of Orthorhombic SmBr3

X-Ray Powder Diffraction Pattern

 

O
d-value (A)

 

Observed
h h K Calculated Observed Intensity
0 1 1 7.4112 7.300 w
0 2 0 6.3530 6.3905 m
0 2 1 5.2136 5.2478 w
0 0 2 4.5620 4.5606 m
1 1 1 3.5485 3.5416 w
1 0 2 3.0253 3.0148 w
1 1 2 2.9431 2.9454 w
1 3 0 2.9241 2.9264 m
1 3 1 2.7846 2.7876 4
0 3 2.7432 2.7434 m
1 2 2 2.7314 2.7240 m
0 3 3 2.4704 2.4717 w
1 1 3 2.3870 2.3857 A
1 2 3 2.2498 2.2510 A
1 3 3 2.1079 2.1064 w
2 0 2.0210 2.0219 m
2 1 0 1.9959 2.0078 m
2 1 1 1.9498 1.9487 m

 

58

Appendix G:

X-Ray Powder Diffraction Pattern

 

 

of Monoclinic SmBr3°6H20
d-value (A) Observed

h h 4 Calculated Observed Intensity
0 0 1 8.1422 8.0792 w
0 l 0 6.7620 6.8446 m
I 0 1 6.6184 6.6110 4
1 0 1 6.1324 6.2048 6

l 0 5.6034 5.6750 m
0 0 1 5.2020 5.2576 m
2 0 0 5.0053 5.0398 m
'1' 1 1 4.6930 4.7269 4
l 1 1 4.5426 4.5676 6
0 0 2 4.0711 4.1037 6
1 0 2 3.6918 3.7042 4
2 1 1 3.5372 3.5596 4
0 1 2 3.4878 3.5064 W
0 2 0 3.3810 3.3885 w
2 0 2 3.2592 3.2762 vw
l 2 0 3.2032 3.2125 m
3 0 1 3.1574 3.1734 uw
0 2 1 3.1225 3.1314 m
3 0 1 3.0223 3.0302 m
‘1' 2 1 3.0013 3.0046 m
l 2 1 2.9608 2.9723 m
2 1 2 2.9360 2.9477 m

59

Appendix G (Cont'd):

60

 

d-value (A)

 

Observed
h h £ Calculated Observed Intensity
3 1 1 2.8609‘ 2.8697 0w
2 2 0 2.8017 2.8006 4
3 1 1 2.7592 2.7696 w
3 2 1 2.6781 2.6851 m
2 2 1 2.6213 2.6262 m
0 2 2 2.6010 2.6098 m
1 0 3 2.5792 2.5884 m
I 2 2 2.5421 2.5491 m
3 0 2 2.5054 2.5098 m
1 2 2 2.4934 2.4864 m
1 1 3 2.4099 2.4188 m
3 2 0 2.3750 2.3791 a
4 0 1 2.3514 2.3571 m
3 1 2.3076 2.3111 3
4 1 1 2.2911 2.2945 w
4 1 1 2.2210 2.2237 w
2 1 3 2.1995 2.2056 m
1 3 0 2.1989 2.1978 m
I 3 1 2.1302 2.1342 m
0 2 3 2.1165 2.1185 m
3 2 2 2.0922 2.0961 m
4 o 2 2.0751 2.0768 w
2 3 0 2.0552 2.0562 0w

 

Appendix H: X—Ray Powder Diffraction Pattern
of Tetragonal SmOBr

 

in,
d-value (A)

 

Observed

Calculated Observed Intensity
0 0 7.9041 7.9475 m
0 0 3.9672 3.9556 vw
1 0 3.5312 3.5110 w
1 1 2.7944 2.7976 m
l 1 2.2780 2.2488 vw
1 0 2.1934 2.2082 uw
2 0 1.9758 1.9720 w
2 0 1.9151 1.9028 w
2 0 1.7677 1.7543 w
2 1 1.7230 1.7098 w
2 1 1.6146 1.6131 m
0 0 1.3172 1.3079 vw
1 0 1.2490 1.2405 m

 

61

Appendix I:

of Vernier Sm Br

5 11

X-Ray Powder Diffraction Pattern

 

O
d-value GA)

 

Observed
izh £ Calculated Observed4 Intensity
1 1 0 7.0536 7.028 a
1 1 I 5.2281 5.235 w
5 1 1 4.2879 4.285 m
7 1 I 4.2270 4.269 m
2 0 2 3.8346 3.837 w

12 0 0 3.6670 3.722 w
1 l 2 3.3740 3.371 w
3 1 2 3.3639 3.357 w
2 2‘I 3.2278 3.225 w
6 2 0 3.2121 3.214 w
7 1 2 3.1339 3.101 m
4 2 1. 3.0487 3.058 m

11 1 1 3.0237 3.028 m

13 1 I 2.9810 2.967 w
9 1 2 2.9522 2.957 w
6 2 1 2.8901 2.870 w

12 0 2 2.8597 2.861 w

10 o 2 2.6801 2.667 4
2 2‘2 2.6141 2.615 m
0 0 2.6004 2.600 w

12 2 0 2.5591 2.615 a
2 2 2 2.5520 2.536 w

62

Appendix I (Cont'd):

63

 

d-value (A)

 

Observed

h h l Calculated Observed Intensity
4 2 2 2.4742 2.469 m
12 0 2 2.4577 2.456 w
3 1 3 2.4070 2.408 m
1 1 3 2.3981 2.402 m
17 1 1 2.2275 2.242 m
5 3 1 2.1767 2.174 m
7 3 1 2.1687 2.168 m
16 0 2 2.0824 2.082 w
9 1 3 2.0318 2.020 w

 

'lilllll'lili)‘li.ll1”

 

 

Appendix J:

X-Ray Powder Diffraction Pattern

of Vernier Sm Br

6 13

 

O
d-value (A)

 

Observed
h'k £ Calculated Observed Intensity
3 1 0 6.4177 6.3715 w
1 1 I 5.2183 5.2138 w
3 1'2 5.0578 5.0005 vw
7 1 0 4.7149 4.6891 w
5 1 1 4.2848 4.3030 A
7 1 1 4.2165 4.2428 m
2 0 2 3.8233 3.7024 A
1 1 2 3.3662 3.3809 vw
8 0 2 3.3553 3.3509 w
2 2 1 3.2232 3.1979 m
3 1 2 3.1704 3.1740 vw
4 2 1 3.0459 3.0681 vw
6 2 1 3.0252 3.0290 m
11 1 1 3.0223 2.9999 w
13 1 1 2.9743 2.9626 w
9 1 2 2.9428 2.9418 w
12 0 2 2.8497 2.8530 w
7 1 2 2.8029 2.7990 m
10 0 2 2.6785 2.6601 w
14 0 2 2.6126 2.6093 0w
2 2 2 2.6091 2.5932 0w
12 2 0 2.5564. 2.5502 w

64-

Appendix J (Cont'd):

65

 

6
d-value (A)

 

Observed
h h L Calculated Observed Intensity
2 2 2 2.5489 2.5198 m
4 2 2 2.4712 2.4696 “m
9 l 3' 2.2654 2.2316 um
12 2 2 2.2271 2.2210 vw
7 3 I 2.1657 2.1669 0w
10 2 2 2.1424 2.1480 w
7 3 1 2.1052 2.0926 w
16 0 2 2.0816 2.0776 uw
15 1 3 1.9865 2.0080 w
2 0 3 1.9086 1.9137 um
10 4 I 1.6345 1.6379 we
19 3 1.5819 1.6039 vw

 

Appendix K: X-Ray Powder Diffraction Pattern

of Monoclinic YBr3

 

 

 

d-value (A) d-value (A)
Observed Intensity Observed Intensity
8.3924 vw 2.7970' 6
7.5313 m 2.7495 vw
7.1219 vw 2.7066 w
6.7456 0w 2.6085 w
(6.4499 m 2.5596 uw
6.0259 4 2.5301 uw
5.6154 m 2.4965 m
5.2240 uw 2.4770 m
5.0042 m 2.3521 w
4.6738 vw 2.2331 w
4.5990 m 2.2110 m
4.0415 w 2.1774 w
3.6598 w 2.1089 w
3.5958 w 2.0793 m
3.5064 m 2.0498 m
3.3295 m 2.0394 m
3.1945 m 1.9155 vw
3.1400 w 1-8595 w
3.1003 m 1.8250 0w
3.0403 w 1.7889 0w
3.0054 m 1.7480 vw
2.9750 m 1.6590 vw

 

66‘

Appendix L:

of Vernier Sm YBr

5 13

X-Ray Powder Diffraction Pattern

 

0
d-value (A)

 

Observed
h h L Calculated Observed Intensity-
5 1 0 5.5356 5.5970 uw
1 1 I 5.2191 5.2038 0w
5 1 1 4.2826 4.2885 w
7 i‘I 4.2114 4.2478 w
1 1 2 3.3671 3.3755 w
8 0 2 3.3525 3.3581 w
2 2 I 3.2234 3.2217 w
3 1 2 3.1709 3.1843 w
7 1 2 3.1226 3.1164 w
4 2 1 3.0456 3.0350 m
11 1 1 3.0176 3.0291 m
18 i'I 2.9678 2.9702 w
6 2 1 2.8868 2.8698 0w
7 1 2 2.8020 2.8199 6
10 o 2 2.6763 2.6675 w
14 0 2' 2.6077 2.6308 w
2 2 2 2.6095 2.6044 um
12 2 0 2.5529 2.5686 w
4 2 2 2.4713 2.4650 m
12 0 2 2.4539 2.4687 m
8 2 2 2.4437 2.4378 w
3 1 3 2.4010 2.4008 w

67

68

 

 

Appendix L: (Cont'd):
A d-value (A) Observed—_-

h h L Calculated Observed Intensity
3 3 1 2.2854 2.2455 w
13 l 2 2.2334 2.2347 w
12 2‘2 2.2249 2.2319 w
20 0 0 2.1943 2.2021 w
7 3 I 2.1650 2.1659 uw
16 0 2 2.0786 2.0779 w
11 l 3 1.9281 1.9280 vw
15 3 0 1.8452 1.8470 um
24 0 0 1.8262 1.8278 um
13 1 4' 1.7128 1.7174 vw
3 3 3 1.6992 1.6985 vw
26 0 0 1.6857 1.6857 vw
l7 3 1 1.6677 1.6722 vw
10 4 I 1.6340 1.6371 um
17 1 I 1.6030 1.6046 w
19 3 1 1.5835 1.5853 vw
15 3 3 1.5599 1.5607 um
10 2 4 1.4985 1.4977 vw
22 0 4 1.4852 1.4780 um
21 3 3 1.4038 1.4044 vw
22 2 I 1.3713 1.3750 vw

 

Appendix M:

X-Ray Powder Diffraction
Pattern of Cubic HfBr

 

 

4
d-value (£) Observed
h Z Calculated Observed Intensity
1 1 6.2937 6.3427 w
0 0 5.4662 5.4789 w
1 1 3.3022 3.2552 w
2 2 3.1500 3.0350 0w
2 1 2.9147 2.9231 w
0 0 2.7276 2.7380 vw
1 1 2.0991 2.1062 w
2 1 1.9933 1.9468 b
2 2 1.9004 1.8997 w
0 0 1.8185 1.8281 w
1 1 1.3431 1.3769 m

 

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