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ABSTRACT

THE PREPARATION AND SOME PROPERTIES
OF NEW LANTHANIDE DIBORIDEDICARBIDES

by Norman Allen Fishel

The previously unreported diboridedicarbides of
cerium, samarium and thulium have been prepared. These
have beenstudied by X-ray diffraction techniques and
have been shown to be members of the isostructural
lanthanide diboridedicarbide series. Indications for
the existence of an Eu3202 phase are reported.

An examination of LnBZC2 stability with varying
metal oxidation number has been conducted. A discussion
of the diboridedicarbide structure and bonding is related
to anomalous lattice parameters observed for YbBZCZ'

The failure to observe diboridedicarbides for calcium,
strontium, barium, thorium and metal mixtures is

considered.

THE PREPARATION AND SOME PROPERTIES
OF NEW LANTHANIDE DIBORIDEDICARBIDES

By
Norman Allen Fishel

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Chemistry

1968

ACKNOWLEDGMENTS

The author is especially indebted to Professor
Harry A. Eick for his guidance and personal interest
throughout the course of this research.

Particular thanks are due to my colleagues in the
High Temperature Group. Their interest and suggestions
and the rapport of the laboratory were very helpful in
producing these results.

This work would not have been possible without
the encouragement, support and patience of my wife
Grace. The author is particularly grateful for her
understanding.

Financial support of this research by the United
States Atomic Energy Commission under contract number

AT (11-1)-716 has been very welcome.

ii

TABLE OF CONTENTS

Page

I. INTRODUCTION . . . . . . . . . . . . . . . 1

A. Preface O O O O O O O O O O O 0 O 0 I
B. Incentives for this research. . . . . I
-C. Historical. . . . . . . . . . . . . . 2
D. Thesis organization . . . . . . . . . 4
II. EXPERIMENTAL METHODS . . . . . . . . . . . 6
A. IntrOdUCtion. O O O O 0 0 O O O O O O 6
B. Sample preparation. . . . . . . . . . 6
1. Starting mixtureS. . . . . . . . 6

2. Reactant preparation . . . . . . 7

3. Arc-melter . . . . . . . . . . . 8

4. Tantalum bombs . . . . . . . . . 9

5 O CruCibles O O O O O O O O 0 O 0 0 IO

6. Quartz ampoules. . . . . . . . . 10

C. Sample characterization . . . . . . . 10
1. X-ray analysis . . . . . . . . . 10

2. Micrographic analysis. . . . . . 12

II I 0 RESULTS 0 O O O 0 0 O O 0 O O 0 0 0 0 0 O O 13
A. Synthesis experiments . . . . . 13
1. Lanthanum diboridedicarbide. . . 13

2. Cerium diboridedicarbide . . . . 13

3. Samarium diboridedicarbide . . . 13

4. Europiummboron-carbon. . . . . . 18

5. Thulium diboridedicarbide. . o . 18

6. Other diboridedicarbides . . . . 18

7. Other preparations . . . . . . 22

.B. Diboridedicarbide characterization. . 22
1. Appearance 0 o o o o o o o o o o 22

2 Hydrolysis . . . . . . . . . . . 25

3 Vaporization . . . . . . . . . . 25

4. Annealing. . . . . . . . . . . . 26

iii

TABLE OF CONTENTS - Continued

IV. DISCUSSION 0 o o o o o o o o o o o a

A. Lattice parameter variations. .
1. Correct unit cell. . . . .
2. Chemical bonding . . . .

B. The problem.of europium
diboridedicarbide . . . . . .

C. Suggestions for future research

BIBLImRAPHY O O O 0 O O O O O O O O O 0
APPENDICES O O O O O O O O O O O O O O 0

iv

Page
27
27
29

32
33

35
37

LIST OF TABLES

TABLE Page

1. X-ray diffraction data for a cerium(lV)
oxide-boron-graphite reaction product
Copper Kfizradiation . . . . . . . . . . . 14

II. X-ray diffraction data for SmB2C2
Copper Kfi'radiation . . . . . . . . . . . 16

III. X-ray diffraction data for an EuZOZ-
B-C reaction product
Copper Kal radiation. . . . . . . . . . . 19

IV. X-ray diffraction data for a Tm203-
B-C reaction product. . . . . . . . . . . 20

V. Lattice parameters for
tetragonal LnB2C2 . . . . . . . . . . . . 23

FIGURE

11.
III.

LIST OF FIGURES

Page

X-ray diffraction data for LnBZC2
Copper K62 radiation .

O O O O O O O O O 17

LnBZC2 lattice parameter variation. . . 24

LnBZCZ StruCtureo o o o o o o o o o o o 28

vi

LIST OF APPENDICES

APPENDIX

1.

11.

Sources and purities of
materials employed. . . .

Index to X-ray records. .

vii

I. INTRODUCTION

A. Preface

The recent rapid advances in nuclear and space
technologies have necessitated the development of mater-
ials for high temperature applications. Binary compounds
of the lanthanides are of particular interest for their
unusual electrical and thermal properties which are
exhibited along with high temperature thermodynamic
stability.

In particular, the lanthanide borides and carbides
have been studied frequently, but for many of the phases
the physical and thermochemical properties have been only
partially characterized. Only the most basic information

is available about ternary lanthanide-boron-carbon systems.
B. Incentives for this research

The search for an explanation of the two following
observations provided the incentives for this research.
First, while trying to study the equilibrium pressure of
carbon monoxide for the reaction

Sm203(s) + 3340(3) = 28m86(s) + 3CO(g) [1]

1

Butherus observed a new pseudo-cubic phase which he

thought was a borocarbide. Second, P. K. Smith and

2

Gilles in a study of the lanthanide diboridedicarbides,

LnBZCZ’ were unable to prepare this phase for samarium.

1

The possibility that these two observations were related

set the initial course of this research.
C. Historical

Metal borides and carbides frequently are prepared
by the carbo-thermal reduction of the metal oxidesB.
Because of the great reactivity of borides at high temper-
atures, carbon impurities are often present in the form
of occlusions of binary or ternary compounds.

The first report of a ternary compound in a lantha-
nide-boron-carbon system was the observation by Brewer
and Haraldsen4 that CeB4(s) was not stable in the presence
of graphite. Post 25 al.5 in attempting to prepare
lanthanide borides by reaction of the sesquioxides with
boron in a graphite crucible, observed tetragonal phases
of composition MBx ( x was reported as either three or
four; M was La, Pr, Gd or Yb ). In preparations of
samarium borides they reported some indications of this
MBx phase, but definite identification was not made. They
believed that the phases may have been stabilized by
small amounts of carbon.

Johnson and Daane6 although unsuccessful in their
attempts to prepare the MBx phase reported by Post 9; 3;.
observed that "a eutectic reaction" of carbon with
lanthanumeboron alloys yielded a ternary compound of the

7,8

estimated formula LaBC. Binder obtained an yttrium

phase similar to the MBx one and described it as having

 

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an approximate composition of YBZC. Eick9 reacted ErB4
with graphite in high vacuum at elevated temperatures
(>'22000) and obtained a hard brittle substance similar
to the other MBx borides.
1n the reaction of B203 with either La203 or CeOz,

10,11

Markovskii g£_2I. noted that borocarbides similar

in properties to alkaline-earth borocarbides were formed.

Hoyt and Chorne'12

hot pressed lanthanide oxides with.
boron in graphite dies and determined that the resulting
borides were boron deficient due to reaction between the
borides and graphite. They also reported that the heating
of lanthanide tetraborides and hexaborides in graphite
crucibles yielded only boron carbide and lanthanide
carbides.

P. K. Smith and Gillesz’13 prepared the Nd, Gd, Tb,
Dy, Ho, Br and Yb diboridedicarbides by arc-melting stoi-
chiometric mixtures of the respective tetraborides and
graphite. Four other phases in the Gd-B-C system.were
deduced from the ternary phase diagram and reported as
h‘V1ns °°mP°Siti°n9 °f Gdo.4oBo.3SCo.25’ Gd0.3sBo.19co.46’
Gd0.3580.45C0.20 and Gd0.3030.4000.30. The reaction of
either lanthanum or samarium hexaboride with graphite
failed to yield the diboridedicarbide. The analagous

14 by arc-melting

Lu3202 was prepared by Nordine g; 2;.
mixtures of the elements. X-ray powder diffraction
analyses indicated that these LnB2C2 phases were identical

with the previously recorded MBx phases.

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The crystal structure for the homologous lanthanide
diboridedicarbide series was determined by P. K. Smith
22 2;.15 from X-ray diffraction data for a single crystal
of TbBZC2 and intensity data from powdered HOBZCZ°

G. S. Smith g;,gi.16

reported the crystal structure of
ScB2C2 to be of orthorhombic symmetry and therefore to not
be isostructural with the lanthanide diboridedicarbides
which possess tetragonal symmetry.

A summary of investigations in the actinide-boron-
carbon systems is given by Rudy17. In the uranium and
thorium.aystems there is no evidence for the existence of
any actinide diboridedicarbide phases.

Curtis18

studied the precipitation of graphite from
the lanthanide hexaborides for reaction mixtures which had
been heated to temperatures in excess of 20000. The
products from.mixtures of NdB6, PrB6, CeB6 and LaB6 and
carbon were the respective hexaboride and recrystallized

graphite. Both YbB6 and YB6 formed with carbon the

diboridedicarbides and the hexaborides.
D. Thesis organization

This work involves primarily a) the preparation of
samarium diboridedicarbide from a number of varied
starting mixtures and a wide range of reaction conditions,
and b) an examination of LnBZC2 stability with varying
metal oxidation number. The SmBZC2 samples were charac-

terized by several methods and the results are presented.

 

 

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5
The study included the attempted preparation of other
isostructural MBZC2 phases in which M was La, Ce, Eu, Gd,
Tm, Yb, Lu, Y, Ca, Sr, Ba and Th and mixtures of the fol-

lowing: Sm-Ca, Sm-Th and Ca-Th.

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II. EXPERIMENTAL METHODS

A. Introduction

Materials which were used as reactants, crucibles
and bombs are listed in Appendix 1 along with their sources
and purity levels. Appendix 11 lists by record number and
research notebook reference those phases identified by

X-ray diffraction analysis.
B. Sample preparation

1. Starting mixtures

A variety of starting mixtures was used to prepare
the diboridedicarbides. Equations [2] through [9] are
intended to represent approximate starting stoichiometries

and not necessarily simple reactions.

LnB6(s) + 30(s)* = LnB2C2(s) + B4C(s) Ba
2LnB4(s) + 50(3) = 2LnB2C2(s) + B4C(s) Efl
Ln203(s) + B40(s) + 6C(s) = 2LnB2C2(s) + 300(g) Ba
Ln203(s) + 43(3) + 7C(s) = 2LnB2C2(s) + 300(3) [5]
Ln203(s) + 21320302.) + 130(3) = 2LnB2C2(s) + 900(3) [6]
2Ln(s) + B40(s) + 3C(s) = 2LnB2C2(s) DU
Ln(s) + 2B(s) + 2C(s) = 2LnB202(s) Efl
LnB6(s) + 2Ln(s) + 6C(8) = 3LnB2C2(s) B8

The synthetic starting mixtures were usually chosen
* g833t§8£§SSGnts the graphitic form of carbon in these

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to approach one of the ratios listed above. In selected

cases a large excess of one of the components was used.

2. Reactant preparation

All of the reactants except samarium and europium
metals, SmB4 and SmB6 were available in the form of powders.
Samarium metal powder obtained by filing an ingot of the
metal was sometimes used after iron contamination had
been removed magnetically. Although Sm metal can be
oxidized by air, the reaction is slow enough so that oxide
contamination was minimal since exposure to air was brief.
All handling of Eu metal was performed in a helium filled
glove box.

Metal borides were prepared either by direct reaction
of the elements or by reduction of metal oxides19 in the
arc-melter. The reacted pellets were crushed in a dia-
mond steel mortar and then ground finely with an agate
mortar and pestle. The boride samples were washed suc-
cessively with 50% HCl and distilled water and allowed
to air dry at room temperature. Alkaline-earth oxides
were prepared by calcining the metal carbonate or hydroxide
at 850° for two days.

The weighed starting compositions were mixed thor-
oughly either by grinding with an agate mortar and pestle
or by shaking in a plastic container mounted on a Wig-L-
Bug amalgamator (Crescent Dental Co., Chicago, Illinois).
If the sample was to be heated by arc-melting, the mixed

powder was compacted into a one-quarter inch diameter

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pellet using a hardened steel die under a hydraulic press
(Carver Laboratory Press, Fred S. Carver, Inc., Summit,
New Jersey) employing a press pressure of about 3000 psi.
Solid metal chips when used were placed together with the

powdered reactants in the reaction vessel.

3. Arc-melter

The majority of the samples were fused in an arc-
melter equipped with both a water-cooled electrode and a
water-cooled copper hearth. A detailed description of
this equipment has been given by Butheruszo.

A one-quarter inch diameter tungsten electrode was
used for all preparations except one in which a graphite
electrode was used. Arc currents varied from 20 to 200
amperes direct current with 75 to 100 amperes being most
common. If currents lower than 75 amperes were used,
incomplete melting of the sample was often observed, while
currents of greater than 100 amperes frequently caused
sputtering.

An electric arc was struck by momentarily touching
the electrode to the hearth. The arc was then played upon
the sample pellet which heated rapidly and then melted.
The temperature could be controlled coarsely by raising
or lowering the electrode or by operating a foot treadle
which controlled the welding generator output. After the
sample was fused, heating was continued for approximately

one minute after which the sample solidified almost

9

immediately. It was then turned over and remelted to
promote homogenity. There was some evidence of pitting
of the copper hearth but copper contamination was assumed
to be minimal.

The arc-melter was filled with helium which was
purged of active gases by arcing a zirconium button before
the melting of each pellet. A few reactions were con-

ducted with a carbon monoxide atmosphere.

4. Tantalum bombs

An alternative to arc-melting for sample preparation
was to confine the reactants in a tantalum tube which was
sealed by welding prior to heating. Before its use as a
bomb the tubing was outgassed by inductively heating it
at temperatures up to 21000 in high vacuum for periods of
up to eight hours. One end of the tube was sealed by
heliarc welding, the reactants were placed in the tube
Which was then placed in a welding chamberh The chamber-was
alternately evacuated and then flushed with helium several
times and finally the open end of the bomb was welded.
The bomb was heated by induction. Temperatures were meas-
ured using a disappearing filament optical pyrometer
(Leeds and Northrup Co., Philadelphia, Pennsylvania) by
sighting onto the outer wall of the bomb. No correction
was made for window or prism transmittance or for the

emissivity of the tantalum surface.

10

5. Crucibles

In one preparation the reactants were placed in a
tungsten crucible which was heated inductively. Although
a product composition based upon starting stoichiometry
was not obtained because of the interaction of tungsten
with boron and boride samples at high temperaturesZI, the
diboridedicarbide was the major product. Several attempts
to prepare samarium diboridedicarbide in a graphite

crucible were unsuccessful - samarium dicarbide was the

major product.

6. Quartz ampoules

Quartz was found unsatisfactory for SmBZC2 prepar-
ation because of its degradation by the boron. Attempts
to use a platinum foil liner to shield the quartz were
equally unsatisfactory because of formation of a platinum-

samarium alloyzz.

C. Sample characterization

1. X-ray analysis

All reaction products were subjected to X-ray dif-
fraction analysis. This technique normally detects
phases present to the extent of ten per cent or more in
a mixture of phases. In the majority of preparations
more than one phase was present and it was not always
possible to identify all the phases. Quantitative ele-
mental analyses were not performed because of the inability

to prepare a pure diboridedicarbide phase.

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Debye-Scherrer powder X-ray diffraction analysis
with copper K radiation (h& = 1.54183) was used for most
of the samples. The mass absorption coefficient for
copper K radiation reaches a maximum near samarium23 so
that long exposure times were required for the X-ray films.
Film.backgrounds were greatly darkened by the fluorescence
radiation from samarium. This condition was partially
alleviated by masking the film with a layer of aluminum
foil which acted as a screen. Alternately, exposures
were made with iron K radiation (A2! = 1.93733) for which
the mass absorption coefficient for samarium is low.

Some preparations were examined using a Guinier
foward focusing24 X-ray powder diffraction camera
(Ingenibrsfirman Instrumenttjflnst, Sundbyberg 1, Sweden)
employing copper K&;radiation. Focusing and separation
of the Kx'radiation of the unfiltered primary beam are
achieved by isolating the (1051) reflection from a curved
single crystal quartz plate. The sample was mounted by
adhering a thin layer of the powdered sample on Scotch
transparent tape covering the hole in the sample disc.

Intensity data using copper K radiation were taken
with a Siemens Kristalloflex IV X-ray generator, diffrac-
tometer and scaling equipment (Siemens America Inc., New
York, New York). Powdered samples were mounted on
40x40x1 mm glass slides using Canada Balsam (Fisher Sci-
entific Co., Pittsburgh, Pennsylvania). Platinum powder

(Englehard Industries Inc., Newark, New Jersey) was mixed

12
with the samples to provide an internal standard. The
Siemens equipment was also used in the fluorescence mode
of operation with a LiF analyzing crystal and tungsten
white radiation to determine if tantalum was present as
a contaminant in those samples prepared by the bomb
technique.
Precise lattice parameters were obtained by a Nelson-
Riley extrapolation for Debye-Scherrer data and by a
25

(cos a cot ¢) extrapolation for diffractometer data .

A CDC 3600 computer was used for these computations.

2. Micrographic analysis

Some of the arc-melted pellets were examined micro-
graphically with magnifications up to 800x with a Bausch
and Lamb model DMZ-D3 Dyna-Zoom Metallograph (Bausch and
Lomb,1nc., Rochester, New York). The samples were pre-
pared for examination by encapsulating them using Meta-
Test Cold Mount (Precision Scientific Co., Chicago,
Illinois) and then polishing with silicon carbide papers
of successively finer grits. Samples were observed under ‘
a variety of viewing conditions (dark field, polarized
light, green field) and after having been treated with a
variety of etchant solutions (HCI, HN03, HNOZ). Distin-
guishable domains were never seen even with a sample which
was later shown by X-ray analysis to contain more than

one phase.

III. RESULTS

A. Synthesis experiments

1. Lanthanum diboridedicarbide

Two samples which were prepared by arc-melting nearly
stoichiometric mixtures of the sesquioxide, boron and
graphite in accordance with equation [3] , contained
LaBZC2 as the major product with LaB6 and other uniden-
tified phases as minor constituents. The calculated
lattice parameters are a0 = 3.816 t 0.002* and co - 3.975

t 0.003%.

2. Cerium diboridedicarbide

The preparation of CeB'ZC2 was conducted in a manner
similar to that used for the LaBZC2 preparation. X-ray
powder diffraction data for a typical preparation, a
cerium(lV) oxide-boron-graphite reaction product, are
given in Tablefil. The extrapolated lattice parameters

are a0 a 3.817 t 0.001 and Co = 3.852 : 0.0013.

3. Samarium diboridedicarbide

The first two syntheses were conducted with a carbon
monoxide atmosphere in the arc-melter in the belief that
the reaction was represented by equation [F] . Subsequent

arc-melter syntheses were conducted with a helium atmos-

phere. The phase which was identified later as SmB2C2

* Errors reported are standard deviations.
13

14

 

 

 

 

 

 

 

 

Table I. X-ray diffraction data for a cerium(lV) oxide-
boron-graphite reaction product
Copper Kai radiat ion
(§§B2 2C2 (R)CeB6
NO. (1 d * 2
calc.# (hkl). calc. (hkl) sin eobs. d (R)obs.
.1 , _i
1 4.103 100 0.0353 4.103
2 3.832 001 0.0405 3.832
3 3.781 100 0.0416 3.781
4 graphite (002) 0.0536 3.331
5 0.0617 3.102
6 2.901 110 0.0702 2.909
7 2.712 101 0.0818 2.697
8 2.369 111 0.1051 2.378
9 0.1228 2. 200
10 1.928 002 0.1605 1.924
11 1.908 200 0.1641 1.903
12 1.835 200 0.1742 1.847
13 1.;20 102 0.2011 1.719
14 1. 10 201
1.716 210 0.2052 1.712
15 1.625 211 0.2248 1.626
16 1.568 112 0.2427 1.567
17 1.560 211 0.2448 1.558
18 1.368 300 0.3134 1.377
19 1.356 202 0.3242 1.354
20 1.349 220 0.3255 1.351
21 1.297 310 0.3482 1.306
22 1.278 212 0.3650 1.276
23 1:273 33% 0.3671 1.272
24 1.237 311 0.3840 1.242
25 1.237 311 0.3867 1.240
%g 1.21; 103 0.3998 1.219
1.20 301
1.206 310 0.4082 1.207
28 1.160 113 0.4417 1.160
29 1.151 311 0.4509 1.148
30 0.4705 1.123
# a0 - 3.7813, c0 = 3.8322

8 a0 - 4.1038

15
was found to be a reaction product whenever graphite or
a carbon containing Compound was present as a reactant.

The purest samples of SmBZC2 were obtained when
either the sesquioxide or metal was arc-melted with boron
and graphite. SmBZC2 was a product when any of the mix-
tures represented by equations [4] through [9] was arc-
melted. Samarium tetraboride was never prepared free of
the hexaboride, so the stoichiometry given in equation Efl
could not be tested. Attempts to prepare SmBZC2 from the
hexaboride and graphite [2] were unsuccessful.

SmBZC2 was the major product in bomb preparations
from metal, boron and graphite. Contamination by tantalum
borides was often evident. Differences in product com-
position were not noted for preparations at temperatures
from 1100° to 16400.

X-ray diffraction data for SmB2C2 are presented in
Table II. The extrapolated lattice parameters are
a0 = 3.796 t 0.001 and co = 3.696 t 0.0018. A comparison
among the diffraction patterns for GdBZC2 and SmB202 and
other diboridedicarbides is presented in Figure 1.

Although additional phases were frequently present
in the SmB2C2 preparations it was not possible to index
the diffraction data on cubic or tetragonal symmetries.
None of these phases was identified as being similar to
the four other borocarbides reported by P. K. Smith in

the Gd-B-C ternary system.

l6

 

 

 

 

 

 

 

 

Table II. X-ray diffraction data for SmBZC2
Copper K 3‘ radiation
ml1/:: [a (8) a (8) sin2 oca1c# (hkl)
obs. calc. obs. '
1 3.796 3.761 0.04123 100
2 36 3.696 3.657 0.04351 001
3 48 3.684 3.667 0.08247 110
4 100 2.648 2.630 0.08474 101
5 25 2.172 2.160 0.12598 111
6 32 1.898 1.889 0.16494 200
7 28 1.848 1.840 0.17403 002
8 40 1.698 1.692 0.20617 210
9 36 1.688 1.683 0.20844 201
10 36 1.662 1.655 0.21526 102
11 38 1.543 1.537 0.24968 211
12 32 1.522 1.517 0.25650 112
13 16 1.342 1.339 0.32987 220
14 20 1.324 1.321 0.33896 202
15 5 1.265 1.264 0.37110 300
16 8 1.262 1.259 0.37338 221
17 25 1.250 1.248 0.38020 212
18 1.232 0.39156 003
19 16 1.200. 1.196 0.41234 310
20 1.197 0.41461 301
21 5 1.172 1.170 0.43279 103
22 5 1.142 1.140 0.45585 311
23 5 1.120 1.118 0.47403 113
24 1 1.086 1.086 0.50390 222
25 1 1.053 1.050 0.53604 320
26 5 1.044 1.043 0.54513 302
27 1 1.033 1.032 0.55650 203
28 1 1.013 1.012 0.57957 321
29 5 1.007 1.006 0.58637 312
30 1 1.000 0.997 0.59770 213
31 0.949 0.65974 400
32 0.924 0.69611 004
33 0.920 0.70098 410
34 0.919 0.70325 401
35 5 0.915 0.915 0.71007 322
# ao - 3.6968, co = 3.7968

17

Figure I. X-ray powder diffraction data for LnB202
Copper K66 radiation

 

 

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. IJ II II llIlll III
m «1 50 60
Cerium
9.
83 8%

    

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

E
E130 ‘ 31 :J l:
\\ 50 40 so 60
+4
\21 8 Samarium
to: lg _ SN Sgg 51‘:
(7) I l I IT JL 1 1|
2: m m) «a so 60
EE' § Gadolinium
g. TI 3 8‘8 888 as
:I 1 I . I I1 11 H
<( m i 1% fi) &
—J *
159' Thulium
$ 3g 2§ a S 85% 3 S 2
o + I i 1 at I g
m a: 40 50 oo
1 . *
Lutetium
:1 1 i T.§ T T 5
° 28 ' ' 4' ' .1 J.

.i in
DEGREE S (29)

* Relative intensities were not determined.

ll. 1.4111111- ll 11.3.1144

 

18

4. Europium-boron-carbon

Tantalum bomb preparations from the metal, boron
and graphite yielded europium hexaboride, europium dicar-
bide and graphite. When EuZOB-B-C mixtures were arc-melted,
the products were EuB6, graphite and an unknown phase or
phases. Table 111 lists the Guinier X-ray powder dif-
fraction record for the products from the arc-melter. A
partial indexing of the unknown lines was achieved on
tetragonal symmetry with lattice parameters of a0 = 3.771
and co = 4.0283. The diffraction pattern of the unknown
phase was always of poor quality so that relative inten-
sities of the lines could not be compared with the relative

intensities of the diboridedicarbide lines.

5. Thulium diboridedicarbide

The products of arc-melted mixtures of TmZOB-B-C
were Tm3202 and a mixture of thulium borides. Table IV
lists the diffraction lines for a typical arc-melted sam-

ple. The extrapolated lattice parameters for TmBZC2 are
so . 3.776 t 0.011 and Co = 3.477 1 0.0088.

6. Other diboridedicarbides

The diboridedicarbides for gadolinium, ytterbium,
lutetium and yttrium were prepared by arc-melting mix-
tures of the respective sesquioxides, boron and graphite.
Calculated lattice parameters for all the diboridedicar-
bides are compared with the values previously reported in

Table V. Figure 11 is a graphical display of the varia-

19

Table III. X-ray diffraction data for an Eu203-B-C

L

reaction product
Copper Kml radiation

 

 

 

 

 

 

EuB6 Unknown phase
No. 8 (8) sin2 e a (8)# (hkl) a (8),, I (hkl)
obsL obs1L caIg}. chc.

1 4.276 0.0325

2 4.178 0.0340 4.178 100

3 4.075 0.0358

4 4.028 0.0369 4.028 001
5 3.939 0.0383

6 3.771 0.0417 3.771 100
7 3.676 0.0440

8 3.570 0.0466

9 3.457 0.0497
10 3.336 0.0532 graphite (002)

11 3.046 0.0604

12 2.926 0.0692 2.955 110

13 2.795 0.0760

14 2.783 0.0767 2.753 101
15 2.664 0.0837 2.667 110
16 2.608 0.0873

17 2.402 0.1028 2.410 111

18 2.316 0.1108

19 2.221 0.1216 2.223 111
20 2.073 0.1382 2.087 200

21 2.014 002
22 1.915 0.1620

23 1.886 200
24 1.854 0.1727 1.867 210

25 1.789 0.1857

26 1.761 0.1916 1.776 102
27 1.675 0.2118

 

 

# a0 = 4.1788

* a0 = 3.7718, c. = 4.0288

20

Table IV. X-ray diffraction data for a Tm203-B-C
reaction product

 

 

 

 

 

 

mB C TmB TmB
2 2 4 2
No. a ( ) d (8 d (R) d (R)
calc.#l (hkl) calcgk l (hkl) calcjlfl (hkl) Eobs.
1 6.622
2 5.448
3 4.368/(111)
4 3.976 001 3.995
5 3.775 100 3.731 001 3.771l(200)
6 3.519 200 3.497
7 3.458
8 3.363
9 3.229
10 3.147 210 3.146
11 3.026
12 2.946
13 2.833
14 2.736
15 2.669 110 2.666
16 2.635 201 2.628
17 2.602{(220)
18 2.557 101 2.555
19 2.468 211 2.470
20 2.374
21 2.249 101 2.249[(311)
22 2.226 310 2.227
23 2.117 111 2.115
24 1.988 002 1.992
25 1.942 311 1.942
26 1.888 200 1.886 002 1.884
27 1.846 112 1.849
28 ' 1.812
29 1.731 321 1.737
30 1.719/(331)
31 1.707 410 1.706
32 1.688 210 1.681 212 1.684
33 1.660 201 1.659 330 1.656
34 1.565 102 1.578
35 1.518 211 1.516
36 1.483 312 1.456
37 1.335 220 1.333
38 1.304 511 1.318 201 1.306
39 1.295 412 1.297
40 1.278 202 1.274 332 1.277
41 1.258 300 1.257
42 1.246 221 1.240 203 1.244
43 1.231

44 1.222 213 1.226 112 1.226

21

 

 

 

 

 

 

 

Table IV. Continued
T§BZC2 TmB2 R
No. cald? l<hkl) caldgmB (hkl) aéhl (hkl) gbé.)
45 1.211 212 1.210
46 1.194 310 1.192
47 1.183 301 1.182
48 1.156 531 1.157
49 1.129 311 1.129
50 1.108
51 1.058 222 L 062
52 1.047 320 1.045
53 1.019 302 1.018
54 1.002 321 1. 002
55 0.983
56 0.955
57 0.944 400 0.942
58 0.916 410 0.915
59 8.897 322 0.896
60 .890 330
0.885 411 0'889

61 0.875
62 0.862 331 0.861
63 0.852 303 0. 852
64 0.844 420 0. 847
65 0.832
66 0.829 402 0. 829
67 0.820 421 0.820
68 0.810 412 0. 810
69 0.792 332 0. 792
70 0.789

# a0 = 3.7758, co = 3.4768

* a0 a 7.0718, co = 3.9978

17/; a0 = 3.2508, Co - 3.7318

/ These lines can be assigned to TmB12 a0 = 7.4763

22
tion of the diboridedicarbide lattice parameters with
ionic radii. Both a0 and co are plotted on the same

scale to emphasize the difference.

7. Other preparations

Attempts to prepare isostructural tetragonal dibor-
idedicarbides for calcium, strontium, barium, thorium and
mixtures of samarium with calcium or thorium and calcium
with thorium were all unsuccessful. The method of prepar-
ation was arc-melting a mixture of the respective oxides,
boron and graphite.

For the mixed metal preparations, the samarium con-
tent was varied from 90 to 10 atom per cent. There was
no variation of the lattice parameters when SmBZC2 was
observed as one of the products. In the samarium-thorium
preparations containing about 50 atom per cent or more of
thorium, the diffraction pattern of the products was com-
plex. It was not possible to determine if any of the

17

actinide borocarbides reported by Rudy was present since

he gave no diffraction data.

B. Diboridedicarbide characterization

1. Appearance

All samples containing LnBZC2 were hard, brittle
substances colored black or dark grey. The samples had
no characteristic appearance even when viewed with low

power magnification.

23

 

 

 

 

 

Table V. Lattice parameters for tetragonal LnBZC2
This work Other work
L“ a. (8) c. (8) a. (8) c. (8)
La 3.816 3.975 3.82 3.96 (a)
- Ce 3.817 3.852

Pr 3.81 3.81 (a)
Nd 3.803 3.794 (b)
Sm 3.796 3.696
Eu (3.771) (4.028)
Gd 3.793 3.635 3.792 3.640 (b)
Tb 3.784 3.591 (b)
DY 3.782 3.560 (b)
Ho 3.780 3.537 (b)
Er 3.778 3.508 (b)
Tm 3.776 3.477
Yb 3.775 3.552 3.775 3.560 (b)
Lu 3.762 3.453 3.763 3.447 (c)
Y 3.788 3.551 3.78 3.55 (d)-

(a) Reference 5

(b) Reference 13

(c) Reference 14

(d) Reference 7

24

 

 

 

 

Figure II. LnBZC2 lattice parameter variation
41 5” l ' I T* ' I ' I l I
D\\
4o- (EO‘\.‘ —
Lq
é§38- —
05 a
#3 Ce
2% Ag/ (ngmrfiA‘ikaflréfia
(B
85 )
37- «1
u}
9. Sm C.
1:
jabr— Gd '—
Tb ‘7 Yb
m0 Dfl\ D
(K) HJQID
35” Er \ ‘
'fin
Lu
34 L J 1 1 1 l 1 1 1 1 1 I 1
LK) 105 loo 095 090 085
METAL (+3) RADIUS (A)

Lanthanide ionic radii: (8)

La(+3)=aol.061¢(a)
Ce(+3)---1.03-=(a)
Pr(+3)~~-1.013~(a)
Nd(+3)~=-0.995-(a)
Sm(+3)-=~0.964-(a)
Sm(+2)---1.11~-(b)

(a) Reference 29
(b) Reference 31
(c) Reference 30

Eu(+3)~~~0.95-~(a)
Eu(+2)-~~1.10=~(b)
Gd(+3)=-a0.938o(a)
Tb(+3)a~~0.923o(a)
Dy(+3)==~0.908-(a)
Ho(+3)o=~0.894-(a)

Er(+3)---0.881-(a)
Tm(+3)---0.869-(a)
Yb(+3)-~-0.858-(a)
Yb(+2)---0.93--(b)
Lu(+3)--~0.848-(a)
Y (+3)---0.88--(C)

25

2. Hydrolysis

Most of the samples were unstable in air at room
temperature. Partial decomposition took place in periods
ranging from a few hours to a few days. Powdered samples
vigorously reacted with 50% HCl solution evolving
acetylene and frequently another gas with an obnoxious
odor. No further characterization of these gases was
undertaken.

P. K. Smith13

reported that the lanthanide diboride-
dicarbides were stable in air and stable to hydrochloric
acid. The explanation for this apparent difference is
that the observed hydrolysis is not a reaction of the
diboridedicarbide but rather a reaction of a carbon rich
impurity. LnBZC2 was observed in the X-ray diffraction
patterns of samples which had been exposed to air for

several months. The source of the obnoxious odor is not

readily explained.

3. Vaporization

The high temperature vaporization behavior of one
sample of SmBZC2 was observed in the Bendix time-of-flight
mass Spectrometer model 12-107. The sample was confined
in a tungsten crucible which was heated by electron bom-
bardment. As the temperature was increased above 15000,
Sm(g) was identified in the mass spectrum. This was the
only species observed up to 17000 at which temperature

the experiment was terminated.

26
The X-ray powder diffraction pattern of the residue
contained only three diffuse lines, one of which had a

Q value of approximately 13.18.

4. Annealing

Samples of SmB2C2 were annealed by heating in a
graphite container. The diffraction lines were sharper
for those samples which had been heated for about an
hour at 10000 under an atmOSphere of helium. No change
in lattice parameters was observed for annealed gs.
non-annealed samples.

The density of SmB2C2 based upon one formula unit
per unit cell and lattice parameters of a0 = 3.796 and
co = 3.6968 is 6.11 g cm’3. This value is in agreement
with the pycnometric density of GdBZC2 in nitrobenzene

of 6.1 g cm.3 as determined by Smith13.

‘IV. DISCUSSION

A. Lattice parameter variations

1. Correct unit cell
The structure of the lanthanide diboridedicarbides

as determined by P. K. Smith13’15

consists of planar
light atom sheets at z = %, with sheets of metal atoms
sandwiched between them at z = 0. The non-metal sheets
contain fused, regular, equilateral eight- and four-mem-
bered light atom rings with each atom bonded to three
others in the sheet. The metal atoms are situated above
and below the centers of the eight-membered rings. The
length of the a-axis of the unit cell is thus dependent
upon the dimension of the boron-carbon rings. The size
of the metal atoms determines the interlayer spacing
which is equal to the length of the c-axis.

Since the X-ray data did not permit a distinction
between the boron and carbon atoms in the structure, the
resulting space group is £4/EEE (No. 123)26 with one
LnBZC2 unit per cell. P. K. Smith assumed that the most
probable light atom ordering scheme consisted of alter-
nating boron and carbon atoms distributed according to
space group gé/mbm (No. 127) and a cell twice as large,
a' = 1.414a. This structure maintains the four-fold axis
required for tetragonal symmetry. The two possible unit

cells are indicated in Figure 111.

27

 

.

Figllre III.

Ln

T

\

K...—

 

28

Q

 

LnB2C2 structure

 

 

 

JG!

 

L2 \
CG).
\ o

 

Q9"
0
J
0

K74

Jo
©/©

 

 

(9
C
©
{9
K

\

Ln

 

 

Ln

Projection of four unit cells along the z-axis.

6!)

x'/
v

Ln

The

metal atoms are at z = O and the light atoms are at
z = k. The dashed lines show the outline of the
larger unit cell. ' .

® ® O O O

 

0©0©OO

OOOOOO

 

b)

layers.

(X13000

OOOOOO

@ O Q o O
O Q O O 0

Projection showing alternating metal and light atom
Some light atoms are omitted for clarity.

‘r‘llllll‘lrllliilll [I'll (I \
(I'll‘lllllllla‘lilllllll‘u‘l

29

A neutron diffraction investigation would allow the
boron positions to be distinguished and the ordering

scheme established firmly.

2. Chemical bonding

The bonding scheme invoked by P. K. Smith13 requires
the lanthanides to be trivalent. If both lanthanide atoms
in the larger unit cell each contribute three valence
electrons to each eight-membered ring of light atoms, a
total of 34 electrons are available for light atom bonding.
This scheme permits each atom in the ring to satisfy the
octet rule and the overall ring to have aromatic resonance
stabilization (4n + 2 electrons where n is an integer).

The nearly linear relationship between the ionic
radius and the interlayer spacing-c is shown in Figure 11.
Ytterbium shows the greatest deviation from this relation-
ship and perhaps is more properly situated at point A

(Figure 11) which represents the Yb+2

radius. An ytterbium
valence between two and three provides the best fit.
The exact valence of the metal is questionable for

several lanthanide compounds. Westrum27

has studied the
metal valence in the lanthanide hexaborides. Low temper-
ature heat capacity measurements indicate a Schottkey
anomaly that cannot be explained on the basis of exci-

tation of the metal in the +3 state. Investigations of

the fine structure of the main L absorption edges of the

30

hexaborides and oxides show a shift indicative of the
divalent state for Sm, Eu and Yb. Magnetic susceptibility
measurements for 0e36 are consistent with the behavior
expected for Ce+2. For most of the metals the proportion
of Ln+2 increases as the temperature is decreased. In
view of this information, it is necessary to consider

the possibility that the metals are not +3 in the dibor-
idedicarbides.

If the two metal atoms in the larger unit cell of
LnB2C2 are divalent, the total number of electrons avail-
able for light atom bonding would be 32 (two from each
of two metals, three from each of four borons and four
from each of four carbons). On this basis, 24 electrons
would participate in sigma bonding in the eight-membered
ring and only eight in pi bonding. Eight electrons are
not sufficient to provide aromatic stabilization for the
ring. However, if the rings are not aromatic, their
planarity is not easily explained.

An alternative to the planar structure would be a
puckered light atom ring. A regular octagon has interior
angles of 135°. This bond angle would produce large
angular strain in the light atom structure for either
sp2 or sp3 hybridization. The carbon analog of the eight-
membered B-C rings with alternating single and double
bonds is cyclooctatetraene which has been shown to be in

28

a "tub" conformation . Resonance energy gained in the

planar structure is not sufficient to overcome the unfav-

31

orable angular strain. The energy of interconversion
between conformers is estimated to be 10 kcal mole"1 at
room temperature. The aromatic anion of cyclooctatetraene
(Cal-18)"2 has 10 pi electrons and appears to exist in a
planar configuration.

Another factor which casts doubt on P. K. Smith's
structure is the large metal-carbon distance. In H08202
the Ho-C distance is 2.708 which is about 0.28 larger
than the Ho-C distance in Ho3C, Hozc3 or H002. The
metal-boron and boron-carbon bond lengths in HoB202 are
similar to those observed in other compounds.

For a puckered ring structure the metal atoms need
not be centered between the light atom layers. This sit-
uation would permit Ln-C and Ln-B distances to be in
better agreement with the bond lengths observed in related
compounds. There are many possible orientations of the
light atoms (e.g. AAAA, ABAB, etc.) with respect to super-
position along the c-axis. Until the light atom positions
can be determined better one cannot distinguish between
the orientations.

If the rings are planar, and thereby most probably
aromatic, the substitution of two carbon atoms for two
boron atoms per larger unit cell would permit a +2 metal
valence. For those compounds with +3 metal ions, the
samples would be expected to show metallic conduction with
about one conduction electron per metal atom. The for-

mula for this system is then LnZBxCB-x' It should be

. wfilflltuliliii‘ I-vnvi.

F {burn ..

i I. I’ll! Illl
ll i‘l‘il‘l‘lf“ I '(l I

 

32

noted that P. K. Smiths elemental analysis for GdB2C2 was
Gdl.00i0.2032.03i0.01C2.66‘ The above discussion indicates
there may be a composition range for various boron-carbon
ratios for which the structure is stable. The loss of the
four-fold symmetry by the substitution of a boron for a
carbon.mmst be so small that it would be unobservable by

X-ray diffraction.
B. The problem of europium diboridedicarbide

The preparation of borides (other than EuBé) and
carbides of europium has continued to be a problem.
Similarly, it appears that the conditions necessary to
prepare EuBZC2 are elusive.

The agreement between the ionic sizes of the heavier
lanthanides and the length of the c-axis of LnBZC2 is
excellent with the exception of ytterbium as noted. For
the lighter lanthanides, the c parameter exceeds the ionic
size and the rate of increase is greater with increasing
size.

The tetragonal phase observed in the europium system
(Table III) may be the analogous diboridedicarbide but
the X-ray data are not conclusive. Point B (Figure 11)

2

correlates the observed parameters with the Eu+ radius.

It is possible that the Eu+2

ion is at the upper size
limit for the diboridedicarbide structure. It has already
been shown that there is a small size limit since Sc3202

is not a member of the isostructural series.

33

C. Suggestions for future research

Perhaps more than anything else, conductivity meas-
urements would establish the valency of the metals.
Magnetic susceptibility measurements would be difficult
for the samarium and europium compounds since the excited
states are so low-lying that they are populated at
room temperature.

If the ytterbium anomaly does indicate that less
than three electrons per metal are necessary to stabilize
the structure, the failure to observe the analogous
alkaline-earth diboridedicarbides may be due to a problem
of structure. The non-existence of the calcium compound
may be explained by the lack of d and f type orbitals and
therefore may not possess the proper electron radial dis-
tribution to bond to the eight-membered rings. The need
for f type orbitals may be discounted by the existence
of the yttrium compound. The failure to observe the
diboridedicarbide for strontium and barium may indicate
that more than two electrons per metal are necessary.

The large size of strontium and barium.may'also be a
restricting factor.

It should be possible to prepare a diboridedicarbide
from an alkaline-earth-thorium mixture. By varying the
ratio of the metals, the number of electrons necessary to
stabilize the structure may be determined. Further,

diboridedicarbides may exist for some of the metals of

34

group VIII.

Definite composition limits as well.as possible solid
solution ranges need to be established for the diboride-
dicarbide. A preparative technique other than arc-melting
will have to be developed; the arc-melter cannot possibly

produce equilibrium conditions.

10.

11.

12.

13.

14.

15.

BIBLIOGRAPHY

A. D. Butherus, Michigan State University, personal
communication, 1966.

P. K. Smith and P. W. Gilles, J Inor Nucl Chem.,
29, 375 (1967).

P. Schwarzkopf and R. Kieffer, "Refractory Hard
Metals," The Macmillan Co., New York, N. Y., 1953.

L. Brewer and H. Haraldsen, J, Electrochem, Soc.,
102, 399 (1955).

B. Post, D. Moskowitz and F. W. Glaser, J, Am, Chem,
Soc., 78, 1800 (1956).

R. W. Johnson and A. H. Daane, J, Phys, Chem., 65,
909 (1961).

I. Binder, Powder Met. Bull., 7, 74 (1956).
I. Binder, J, Am, Ceram, Soc., 43, 287 (1960).

H. A. Eick in "Rare Earth Research," E. V. Kleber, Ed.,
The Macmillan Co., New York, N. Y., 1961, Part 5,
pp. 297-305.

L. Ya. Markovskii, N. V. Vekshina and G. F. Pronl,
zn rikl Khim., 35, 2090 (1962); J A 1 Chem USSR,
1"3 , Ez'o‘j’os 179—657.

L. Ya. Markovskii, N. V. Vekshina and G. F. Pron',
Zh Prikl Khim., 38, 245 (1965); J, Appl, Chem, USSR,

W, 248 96 ‘5.

E. W. Hoyt and J. Chorne', "Preparation of Self Bonded
Borides," GEAP-3332, Vallecitos Atomic Laboratory,
General Electric Co., Pleasanton, California, (1960).

P. K. Smith, Ph. D. Thesis, University of Kansas,
Lawrence, Kansas, 1964.

P. C. Nordine, G. S. Smith and Q. Johnson, UCRL-12205,
Lawrence Radiation Laboratory, Livermore, California (1964).

P. K. Smith, S. Westman and P. W. Gilles, "Crystal

Structure of Rare Earth Diboride Dicarbides,"
personal communication, I967.‘ .

35

16.

17.

18.

19.

20.

21.

22.

23.

24.

25.

26.

27.

28.

29.

30.

31.

36

G. S. Smith, Q. Johnson and P. C. Nordine, Acta,
ngst., 19, 668 (1965).

E. Rudy in "Thermodynamics of Nuclear Materials,
Proceedings," May 1962, International Atomic Energy
Agency, Vienna, 1962, Ch. 4, pp. 243-269.

B. J. Curtis, Carbon (Oxford), 4, 483 (1966).

N. E. Topp, "Chemistry of the Rare-Earth Elements,"
Elsevier Publishing Co., New York, N. Y., 1961.

A. D. Butherus, Ph. D. Thesis, Michigan State Univ-
ersity, East Lansing, Michigan, 1967.

G. L. Galloway, Ph. D. Thesis, Michigan State Univ-
ersity, East Lansing, Michigan, 1967.

K. A. Gschneider, Jr., "Rare Earth Alloys," D. Van
Nostrand Co., Princeton, N. J. 1961.

H. P. Klug and L. E. Alexander, "X-ray Diffraction
Procedures," John Wiley and Sons, Inc., New York,
N. Y., 1954.

P. M. de Wolff, Acta, Cryst., 1, 207 (1948).

L. v. Azaroff and M. J. Buerger, "The Powder Method,"
McGraw Hill Book Co., New York, N. Y., 1958.

"International Tables for X-ray Crystallography,"
International Union of Crystallography, Kynoch Press,
Birmingham, England, 1952.

E. F. Westrum, Jr. and W. G. Lyon, "Thermodynamics of
Semi-metallic Compounds," presented at the Symposium

on Thermodynamics of Nuclear Materials with Emphasis

on Solution Systems, Vienna, 1967.

R. A. Raphael in "Non-Benzenoid Aromatic Compounds,"
D. Ginsburg, ed., Interscience Inc., New York, N. Y.,
1959’ Ch. 8’ pp. 465-476.

D. H. Templeton and C. H. Dauben, J, Am, Chem, Soc.,
76, 5237 (1954).

W. H. Zachariasen in "The Actinide Elements,“ G.T.
Seaborg and J. J. Katz, eds., McGraw Hill Book Co.,
New York, N. Y. 1954.

F. A. Cotton and G. Wilkenson, "Advanced Inorganic
Chemistry," 2nd ed., Interscience Inc., New York,
N. Y., 1966.

APPENDIX I

Sources and purities of materials employed

Source

Michigan Chemical Corp.
St. Louis, Michigan

Lunex Co.
Davenport, Iowa

American Potash Corp.
West Chicago, Illinois

Matheson Coleman & Bell
East Rutherford, N. J.

J. T. Baker Chemical Co.
Phillipsburg, N. J.

Research Chemicals
Phoenix 19, Arizona

Norton Chemical
Worcester, Mass 01606

Fisher Scientific Co.
Fairlawn, N. J.

Fairmount Chemical Co.
Newark 5, N. J.

United Carbon Products
Bay City, Michigan

Fansteel Metallurgical
North Chicago, Illinois

37

Material

Eu
Sm203
Gd203
Tm203
Yb203
Lu203
Y203

Sm

CeOZ

Eu203
CaCO
B203

3

Sr(0H)2

BaCO3

La203

340

Th02

Graphite

Graphite
rod

Ta tube

Purity

99 %
99.9
99.9
99.9
99.9
99
99.9

99.9+

unknown

unknown

unknown
99

99.49
99.2

99.9

unknown

unknown

Acheson
grade #38

99
Spectro-
scopic

unknown

APPENDIX 11

Index to X-ray records

Debye~Scherrer

Film number Notebook reference Phases identified
A 1940 NAF 203-1 Sm203
A 1941 NAF 202~ZA SmB6
A 1943 reactant B4C
A 1944 NAF 203-3A SmB6
A 1945 NAF 203-4A SmB6
A 1946 NAF 204-ZA SmB6 + 7
A 1946R NAF 204-2A SmB6 + 7
A 1947 NAF 204-1A 7
A 1950 NAF 205a1A. SmBZCZ, SmB6
A 1951 NAF 205-6A SmB6
A 1952 NAF 205-3A SmB6
A 1953 NAF 205-4A 7
A 1965 NAF 207~ZA SmB2C2
A 1967 NAF 206-1AB SmB2C2
A 1970 NAF 207~1A SmB2C2,C,7
A 1971 NAF 206~1ABC SmBZC2
A 1972 NAF 206~1D SmB2C2
A 1973 NAF 206-1E 7
A 1973R NAF 206~1E 7
A 1974 NAF 205-6B SmB6
A 1975 camera background
A 1977 camera background
A 1978 reactant Gd203
A 1983 reactant B
A 1985 NAF 211-1A GdBZCZ’ 7
A 1985R NAF 211-1A GdB2C2,7
A 1986 reactant Gd203
A 1991 NAF 213~7 7
A 2010 NAF 213-1A SmB2C2

38

39

APPENDIX 11 - Continued

Fi lm number

>1>3>>3>>>>>>>>>>>>>>>>>>>>>>>>>>>

>>

2011
2072
2086
2090
2091
2094
2095
2096
2097
2103
2138
2139
2140
2142
2143
2153
2154
2157
2158
2159
2160
2167
2168
2169
2171
2174
2186

2186R

2190
2191
2192

2195
2198

Notebook reference

NAF 213-6A
NAF 217-6
NAF 222-1
NAF 224-1
camera background
NAF 224-2
reactants
NAF 224-4
NAF 224-4
NAF 226-1A
NAF 227-1
NAF 227-3
NAF 227-4
NAF 228-2
NAF 228-6
NAF 228-3
NAF 228-4
NAF 228-5
NAF 228-5A
NAF 228-1
NAF 228-5
NAF 231-1
NAF 231-1A
NAF 231-1
NAF 231-2
NAF 236-1
NAF 237-1
NAF 237-1
camera background
NAF 239-1
NAF 240-1

NAF 242-1
NAF 243-1

Phases identified
SmCz, C

SmB6, SmB4

BaBG, C

SrB
B.
SrB
SrB
7
EuCz, C,+7
GdB2C2,+7
mm6,c,+7
EuB6, + 7

7

EuB6

EuBé, +7

7

7

EuB6, +7
EuB6, x
EuB6, Tan
EuB6,
EuQSQH
EuO-OH
EuB6, +7
EuB +7

, C

O‘Ch 00‘

6’

7
TmBZCZ, TmBz,
1‘mb T111312
SmBZCZ

SmBZCZ, +7

APPENDIX 11 - Continued

Film number
2199
2202
2203
2205
2207
2208
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2231
2233
2234
2237
2249
2250
2260

> 3> >’D> >'3> >'3> >'3> > 3> >*3> >’3> > D> >'3> >’3> > 3> >

Guinier
G 0080
G 0109
G 0100
G 0126
G 0134

Notebook reference
243-1A

NAF
NAF
NAF

NAF

40

243-2
243-4
244-1
244-2
244-3
247-1
247-4
247-5
244-5
248-1
247-3
248-2
248-3
249-1
249-3
248-3
249-1
250-1
250-1
250-2

reactant

reactant

NAF
NAF

NAF
NAF
NAF
NAF
NAF

250—2
247-3

250-2
228-6
228-6
248-1
247-1

Phases identified
SmBZCZ’ +7
SmB202

7

SmB6

CaB6

blank
YBZCZ’ +7
CeBZCZ, 0e36, C
LuBZCZ, +7
Ca0,+7
LaBZCZ’ +7
YbBZCZ’ +7
LuBZCZ, +7
CeBZCZ, +7
SmBZC2

7

CeBZCZ, +7
7

EuC2,+7
EuCz,+7

W

W

EuCZ, +7
YbBZCZ’ +7

EuCz, +7
EuB6, +7
EuB6, +7
LaB2C2, +7
YBZCZ’ +7

41

APPENDIX 11 - Continued

Diffractometer

Record number

U

UUUUUUUUUUUUUUUU

0001
0002
0003
0004
0005
0006
0007
0008
0009
0010
0011
0012
0013
0014
0015
0016
0017

Notebook reference

NAF 217-2
standard

NAF 216-4
NAF 217-3
NAF 217-6
NAF 216-3
NAF 217-4
NAF 224-4
reactant

NAF 217-5
NAF 216-2
standard

NAF 248-1
NAF 217-1
NAF 216-1
NAF 248-3
NAF 227-4

Phases identified

SmB
Pt
SmCz, +7
SmBZCZ, SmB
SmCZ, C
SmBZC2
SmBZCZ, SmB6
SrB6,
Sm203
SmB6, SmB2C2
SmBZCZ, +7
Au

LaBZCZ, +7
SmBZC2

SmB
CeBZCZ, CeBG, +7
SmBZCZ’ +7

6

6

 

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HICHIGRN STRTE UNIV. LIBRQRIES

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