Solid State Chemistry of Energy Conversion and Storage

16 Storage of Hydrogen Isotopes in Intermetallic Compounds

Downloaded by UNIV OF QUEENSLAND on June 5, 2016 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/ba-1977-0163.ch016

S. A. STEWARD, J. F. LAKNER, and F. URIBE Lawrence Livermore Laboratory, University of California, Livermore, Calif. 94550

Reaction of LaCo under high pressure has produced a hydride with the LaCo H composition, which is the expected maximum stoichiometry. A comparison of hydrogen solubility in ErCo with solubilities of previous studies in PrCo5, PrCo3, and ErCo3 show that hydride stability decreases with lanthanide atomic number and with increasing atom ratio of transition metal to lanthanide metal. Empirical methods for estimating ternary hydride enthalpies and free energies are evaluated and are found inadequate for calculating approximate hydrogen plateau pressures. 5

5

9

5

T h e

o i l e m b a r g o i m p o s e d i n 1973 b y t h e O r g a n i z a t i o n of P e t r o l e u m

Exporting Countries ( O P E C ) quickly impressed upon the industri a l i z e d countries t h e i r d e p e n d e n c y o n c h e a p , a b u n d a n t sources of e n e r g y , p r i n c i p a l l y fossil fuels, p a r t i c u l a r l y o i l . A l t h o u g h a p r e - e m b a r g o i n d i f f e r ence has settled u p o n t h e w o r l d a g a i n , a large segment of t h e t e c h n i c a l c o m m u n i t y r e m a i n s a c u t e l y a w a r e of o u r inefficiencies a n d l a c k of b i l i t y i n t h e amounts a n d types of fuels c o n s u m e d .

flexi

Consequently, the

options a v a i l a b l e over t h e next s e v e r a l decades h a v e b e e n

examined.

I m p o r t a n t areas f o r c o n s i d e r a t i o n h a v e b e e n c o n s e r v a t i o n , greater effi c i e n c y i n p r o d u c t i o n a n d u t i l i z a t i o n of e x i s t i n g fuels, a l t e r n a t i v e fuels, a n d t h e n e w technologies

needed

for their development.

This book

focuses o n a d v a n c e d e n e r g y research s u c h as s o l i d state batteries, c a t a l y sis, a n d t h e subject of this p r e s e n t a t i o n , h y d r o g e n . W h i l e h y d r o g e n is often c o n s i d e r e d a n a l t e r n a t i v e f u e l , i t is a

sec

o n d a r y source. I t is a b u n d a n t , c l e a n , a n d p r o d u c e s w a t e r as a c o m b u s t i o n product.

T h e h y d r o g e n isotopes

w i l l also b e u s e d as f u e l f o r f u s i o n

reactors, w h i c h are e x p e c t e d to b e i n o p e r a t i o n b y t h e e n d of this c e n t u r y . 284

Goodenough and Whittingham; Solid State Chemistry of Energy Conversion and Storage Advances in Chemistry; American Chemical Society: Washington, DC, 1977.

16.

S T E W A R D

E T

Hydrogen

A L .

in Intermetallic

285

Compounds

A l t h o u g h h y d r o g e n a n d d e u t e r i u m are u s u a l l y p r o d u c e d b y trolysis, t h e r m o c h e m i c a l cycles are also b e i n g c o n s i d e r e d .

elec

F o r nuclear

a p p l i c a t i o n s t r i t i u m is g e n e r a t e d b y n e u t r o n i r r a d i a t i o n of L i . 6

The gen

e r a t i o n of l a r g e q u a n t i t i e s of the gases creates a storage p r o b l e m , a n d u n t i l r e c e n t l y , h i g h pressure or c r y o g e n i c m e t h o d s of storage w e r e t h e o n l y solutions. B o t h m e t h o d s are costly; c r y o g e n i c storage uses c o n s i d e r a b l e energy for l i q u i f i c a t i o n , w i t h s u b s t a n t i a l e v a p o r a t i v e losses. T h e use of m e t a l h y d r i d e s as storage m a t e r i a l s has b e e n of i n c r e a s i n g interest. M a n y h a v e greater h y d r o g e n densities ( m o l H / c m 2


rial)

3

mate

t h a n l i q u i d h y d r o g e n ( I ). T o b e a g o o d storage m e d i u m , a h y d r i d e

s h o u l d : ( a ) h a v e i n its a b s o r p t i o n c u r v e a reasonable t w o - p h a s e p l a t e a u pressure ( 1 - 1 0 a t m ) d e s o r b gas, ( c )

at r o o m t e m p e r a t u r e , ( b )

r e v e r s i b l y absorb

have a h i g h hydrogen density, a n d ( d )

and

be relatively

i n s e n s i t i v e to gaseous i m p u r i t i e s s u c h as c a r b o n , n i t r o g e n , a n d o x y g e n . T h e hydride should be economical.

T h e most i n t e r e s t i n g regions of t h e

a b s o r p t i o n curves are the p l a t e a u s , w h e r e the h y d r i d e s a b s o r b or release q u a n t i t i e s of

gas over a c o n s i d e r a b l e

composition

r a n g e at

constant

pressure. P r i o r to 1968 most of the h y d r i d e s a v a i l a b l e w e r e those of

the

m e t a l l i c elements. T h e saline h y d r i d e s are q u i t e stable a n d i n some cases v e r y difficult or i m p o s s i b l e to p r e p a r e b y d i r e c t c o m b i n a t i o n of the ele ments.

T r a n s i t i o n metals of G r o u p s I I I a n d I V also f o r m q u i t e stable

hydrides (2).

G r o u p V metals ( v a n a d i u m , n i o b i u m , a n d t a n t a l u m ) d i s

solve l a r g e q u a n t i t i e s of h y d r o g e n .

T h e i r two-phase

(mono- and d i -

h y d r i d e ) p l a t e a u regions are i n the 1-10 a t m ranges n e a r r o o m t e m p e r a ture.

I m p u r i t i e s , e s p e c i a l l y o x y g e n , c a n increase the p l a t e a u pressure

c o n s i d e r a b l y a n d i n h i b i t h y d r i d e f o r m a t i o n at l o w pressures a n d c o m p o sitions. E x c e p t for

p a l l a d i u m , reactions of

other t r a n s i t i o n metals

with

h y d r o g e n are e n d o t h e r m i c , w i t h little or n o gas d i s s o l v e d at l o w t e m p e r a tures.

T h e l i g h t e r rare e a r t h elements h a v e v e r y stable i s o s t r u c t u r a l

d i h y d r i d e s a n d t r i h y d r i d e s . H o w e v e r , w i t h the e x c e p t i o n of e u r o p i u m a n d y t t e r b i u m , t h e d i h y d r i d e s of s a m a r i u m t h r o u g h l u t e t i u m c h a n g e s t r u c t u r e as the M H

3

c o m p o s i t i o n is a p p r o a c h e d .

I n e v e r y case t h e

e q u i l i b r i u m h y d r o g e n pressures are b e l o w one a t m at temperatures n e a r 500°C.

T h e v a n a d i u m , n i o b i u m , a n d t a n t a l u m h y d r i d e s are the o n l y

b i n a r y m e t a l h y d r i d e s w i t h s u i t a b l e a b s o r p t i o n pressures at t e m p e r a t u r e s of interest. T h e i r cost a n d s e n s i t i v i t y to i m p u r i t i e s , h o w e v e r , i n h i b i t t h e i r use as storage m a t e r i a l s . Intermetallic

Compounds

Studies of h y d r o g e n a b s o r p t i o n b y

intermetallic compounds

alloys w e r e r e p o r t e d o n l y i n t e r m i t t e n t l y u n t i l the e a r l y 1960s.

and

M o s t of


286

S O L I D

S T A T E

C H E M I S T R Y

the e a r l y w o r k d e a l t w i t h alloys of p a l l a d i u m w i t h p l a t i n u m , n i c k e l , c o p p e r , a n d e s p e c i a l l y s i l v e r . A n a l l o y of p a l l a d i u m a n d 3 0 %

s i l v e r is

u s e d as a d i f f u s i o n m e m b r a n e i n h y d r o g e n purifiers. T h i s a l l o y is m o r e resistant to d e f o r m a t i o n t h a n p u r e p a l l a d i u m w h e n e x p o s e d to h y d r o g e n (3).

A s t h e s i l v e r c o n c e n t r a t i o n increases, the h y d r o g e n s o l u b i l i t y d e

creases, b u t the d i f f u s i o n constant of the P d / 3 0 % A g a l l o y is s t i l l a b o u t h a l f t h e v a l u e of p u r e p a l l a d i u m ( 3 ) . I n 1 9 6 1 - 6 2 the D e n v e r R e s e a r c h I n s t i t u t e p u b l i s h e d h y d r o g e n s o r p t i o n measurements for over 300 i n t e i m e t a l l i c c o m p o u n d s

ab Al

(4).


t h o u g h m a n y of these measurements h a v e since b e e n r e f u t e d a n d a d d i tional compounds

having high hydrogen

solubility have been

found,

these studies w e r e the first large-scale i n v e s t i g a t i o n of h y d r o g e n i n t e r action w i t h intermetallic compounds. A

l i t e r a t u r e r e v i e w of

metallic ternary and quaternary

hydrides

p u b l i s h e d b y N e w k i r k ( 5 ) covers a w i d e r a n g e of alloys a n d i n t e r m e t a U i c c o m p o u n d s that h a v e b e e n e x a m i n e d r e c e n t l y . S e v e r a l investigators h a v e r e p o r t e d the f o r m a t i o n of a l k a l i a n d a l k a l i n e e a r t h t e r n a r y h y d r i d e s . T h e s e are l i s t e d i n T a b l e I w i t h references a n d are g e n e r a l l y stable i n a i r . S i n c e 1968, research i n this area has c o n c e n t r a t e d o n the f a m i l y of compounds w i t h A B

s t o i c h i o m e t r y , w h e r e A is a l a n t h a n i d e a n d Β is a

5

t r a n s i t i o n m e t a l , u s u a l l y n i c k e l , cobalt, or i r o n . hydrogen absorption by such compounds serendipity (JO). their magnetic

T h e d i s c o y e r y of h i g h

is a classic t a l e of scientific

S o m e of these c o m p o u n d s

h a d been investigated for

p r o p e r t i e s , e s p e c i a l l y as p e r m a n e n t

magnets.

At

the

Philips Laboratories i n T h e Netherlands, acid etching was used i n polish i n g crystals to decrease the surface effects o n c o e r c i v i t y . T h e i n v e s t i g a tors p o s t u l a t e d t h a t h y d r o g e n p r o d u c e d b y the e t c h i n g process m i g h t influence the magnetic properties.

T h e c o e r c i v i t y of S m C o

5

was there

f o r e m e a s u r e d w h i l e the s a m p l e w a s exposed to h y d r o g e n . S u r p r i s i n g l y , the S m C o

5

a b s o r b e d l a r g e q u a n t i t i e s of t h e gas.

This

s e v e r a l studies of h y d r o g e n a b s o r p t i o n b y s i m i l a r A B

5

finding

initiated

compounds

12,13). Table I.

A l k a l i and Alkaline E a r t h Ternary Hydrides

Ternary

Hydride

LiSrH LiEuH Ca IrH Sr IrH Ca RhH Sr RhH Ca RuH Sr RuH Eu RuH 3

3

2

2

5

5

2

2

5

5

2

2

e

6

2

e

Ref. 6 7 8 8 8 8 8 8 9


(JI,

16.

S T E W A R D

E T

Hydrogen

A L .

in Intermetallic

287

Compounds

I n a d d i t i o n to t e r n a r y h y d r i d e s to b e d i s c u s s e d later, recent has s h o w n h y d r o g e n

absorption

pounds: T b F e , D y F e , H o F e , E r F e , T b C o 3

3

3

3

2

7

and L a M g i

(14),

2

I n t e r m e t a l l i c c o m p o u n d s of

Structural Relationships.

work

i n several related intermetallic c o m (15).

7

lanthanide

a n d t r a n s i t i o n metals f o r m a v e r y i n t e r e s t i n g class of structures. T h e A B 5 series crystallizes i n the h e x a g o n a l C a C u (11)

5

(P6/mmm)

t y p e of structure

s h o w n i n F i g u r e 1. G e n e r a l l y , r a d i u s ratios ( r / r ) A

1.30 f o r m the C a C u

5

B

greater t h a n

t y p e c o n f i g u r a t i o n , whereas c o m p o u n d s w i t h r / r A

less t h a n 1.30 p r e f e r the c u b i c U N i

B

s t r u c t u r e . A s c o m p o u n d s are f o r m e d

5


b y r a r e earths to the right of l a n t h a n u m i n the p e r i o d i c chart, t h e s o - c a l l e d l a n t h a n i d e c o n t r a c t i o n results i n a decrease i n A B c a u s e d chiefly b y a c o n t r a c t i o n i n t h e b a s a l p l a n e . g e n e r a l l y stable o v e r the c o m p o s i t i o n range

unit cell

5

The A B

5

volume, p h a s e is

(AB4.8-5.5).

Figure 1. The CaCu (AB ) structure. The large circles represent the Ca (or A) atoms. The small circles represent the Cu (or B) atoms. 5

S

T h e s e m e t a l groups, i n c l u d i n g s o m e of the actinides that consist of structures of s e q u e n t i a l b l o c k s of C a C u f o r m other phases ( 16).

5

a n d Laves phase-type

layers,

A t o m i c s u b s t i t u t i o n c a n l e a d to other structures.

R e p r e s e n t a t i v e structures a n d t h e i r relationships to the L a v e s a n d C a C u arrangements

5

include:

ThMn

i 2

H a l f of t h e c a l c i u m atoms are r e p l a c e d b y

man

ganese p a i r s . Th Zni 2

7

O n e t h i r d of t h e c a l c i u m atoms are r e p l a c e d b y z i n c pairs. T h F e i 2

Th Nii

7

Er Co

7

2

7

and T h C o i 2

7

h a v e this s t r u c t u r e .

S i m i l a r to Th-ΐΖηιτ, b u t t h e l o c a t i o n of t h e r e p l a c e d c a l c i u m atoms is different.

2

T w o d o u b l e layers of C a C u layer

Laves

5

sequence form

packing and a fouran

eight-layer


unit

288

S O L I D

S T A T E

C H E M I S T R Y

s t a c k e d i n t h e c u b i c A B C m a n n e r . M a n y rare earths f o r m this s t r u c t u r e . Ce Ni 2

S a m e as E r C o , b u t t h e e i g h t - l a y e r u n i t s h a v e t h e

7

2

7

A B h e x a g o n a l format. NbBe (AB ) 3

A g r o u p of C a C u

3

layers a n d one of a L a v e s t y p e

5

f o r m a s i x - l a y e r u n i t i n a n A C B sequence. CeNi The

hexagonal

S a m e as N b B e , b u t the u n i t s t a c k i n g is B C .

3

3

AB

5

compounds

form

orthorhombic

hydrides.

The

c h a n g e s i n s t r u c t u r e are u n d o u b t e d l y a r e s u l t of e x p a n s i o n of t h e b a s a l Downloaded by UNIV OF QUEENSLAND on June 5, 2016 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/ba-1977-0163.ch016

p l a n e c a u s e d b y h y d r o g e n a t o m o c c u p a t i o n of t h e i n t e r s t i t i a l sites t h a t He i n the m e t a l layers (17).

These

a s y m m e t r i c sites are t e t r a h e d r a

f o r m e d b y t w o l a n t h a n i d e a n d t w o c o b a l t atoms, a n d o c t a h e d r a

formed

b y t w o l a n t h a n i d e s a n d f o u r c o b a l t atoms. T h e r e are n i n e sites p e r A B formula w i t h two formulas per unit cell.

5

Kuijpers and Loopstra found

b y n e u t r o n d i f f r a c t i o n that the d e u t e r i u m atoms i n P r C o D 5

4

were ordered

o n c e r t a i n a v a i l a b l e o c t a h e d r a l a n d t e t r a h e d r a l sites. T h e p o s s i b l e i n t e r s t i t i a l positions i n the C a C u

5

t y p e s t r u c t u r e are s h o w n i n F i g u r e 2.

Figure 2. The CaCu* structure including asymmetric tetrahedral (Φ) and octahedral sites Estimation of H y d r i d e Stability.

the (Π)

A n empirical method by w h i c h

t h e enthalpies of f o r m a t i o n of alloys m a y b e e s t i m a t e d q u a n t i t a t i v e l y has b e e n f o r m u l a t e d (18,

19, 20).

T h e a p p r o a c h assumes t h a t t h e d r i v i n g

f o r c e f o r reactions b e t w e e n metals is a f u n c t i o n of t w o factors: a n e g a t i v e one a r i s i n g f r o m t h e difference i n c h e m i c a l p o t e n t i a l , Δ φ * , of

electrons

associated w i t h e a c h m e t a l a t o m , a n d a p o s i t i v e one t h a t is t h e difference i n t h e e l e c t r o n d e n s i t y , Δη™, at the b o u n d a r i e s of W i g n e r - S e i t z t y p e cells s u r r o u n d i n g e a c h a t o m . V a l u e s of φ* f o r t h e metals are a p p r o x i m a t e d b y the electronic w o r k functions; n

w s

is e s t i m a t e d f r o m c o m p r e s s i b i l i t y d a t a .


16.

S T E W A R D

Hydrogen

E T A L .

in Intermetallic

Compounds

289

T h e a t o m i c concentrations i n t h e a l l o y m u s t b e i n c l u d e d i n t h e c a l c u l a t i o n . T h e most recent f o r m u l a s f o r p e r f o r m i n g these c a l c u l a t i o n s ( 2 0 ) are: AH = N f(C »,C *)g(C ,C )[-Ρβ(Δφ*) A

B

A

B

/ ( C A ' A ' )

g(CA,C

B

) =

2

=

(c v ™ A

0

C *C °[1 + A

B

+

A

2

c v B

3


CB

S

=

A

A

C VB

2 / 3

/ (C V

A

2 a

(v

)/

+

A

A

B

8(C °C 2/3

B

pressure data coin cide with those in Ref. 25. s

S T A T E

x

ll

2

4 6 8 H/LaCo-

10

i n c r e a s i n g p l a t e a u pressures o r h y d r i d e i n s t a b i l i t y . E r b i u m is to the f a r right of t h e l a n t h a n i d e series a n d forms E r C o w i t h t h e C a C u s t r u c t u r e . O n e a u t h o r r e p o r t e d t h e p r e p a r a t i o n of E r C o (Ero.8eC05.14) i n s t e a d of E r C o ( 2 6 ) . T h i s m a y b e i n error, since o t h e r investigators ( 2 7 ) h a d p r e v i o u s l y f o u n d E r C o . Α Β p h a s e g e n e r a l l y has a w i d e c o m p o s i t i o n r a n g e a n d the x - r a y d a t a for o u r s a m p l e c o r r e s p o n d e d to b o t h patterns ( E r C o a n d E r C o ) i n p o w d e r files, i n d i c a t i n g t h e y are one i n t h e same c o m p o u n d . T h e existence of E r C o is also d o u b t f u l since A B is n o t r e p o r t e d i n other l a n t h a n i d e - t r a n s i t i o n m e t a l systems a n d there is n o s i n g l e c r y s t a l d a t a a v a i l a b l e to s u p p o r t a n a s s u m p t i o n of o r d e r e d v s . r a n d o m s u b s t i t u t i o n of c o b a l t for e r b i u m . S u r p r i s i n g l y , to t h e best of o u r k n o w l e d g e , the r e a c t i o n of E r C o w i t h h y d r o g e n has n o t b e e n r e p o r t e d . H y d r o g e n a b s o r p t i o n i n s e v e r a l p r a e s o d y m i u m - c o b a l t phases ( 2 8 ) a n d i n E r C o ( 2 9 ) has b e e n r e p o r t e d r e c e n t l y . T h e e x p e r i m e n t a l c o m p l e t i o n of the s i m p l e P r C o , P r C o , E r C o , a n d E r C o m a t r i x w o u l d a l l o w a n e x p e r i m e n t a l d e t e r m i n a t i o n of the 5

5

e

5

5

5

δ

e

e

e

5

3

5

3

3

100

P

#

Figure 4. isotherm

Hydrogen for ErCo 5

at

absorption 25°C

atm

H/ErCo

E


5

16.

STEWARD E T AL.

Hydrogen

in Intermetallic

295

Compounds

effect of l a n t h a n i d e c o n t r a c t i o n a n d phase c h a n g e o n t h e h y d r o g e n p l a t e a u pressures. T h e p r e v i o u s d a t a w e r e e x t r a p o l a t e d to 2 5 ° C b y the use of E q u a t i o n 7 a n d c o m p a r e d w i t h t h e present results. T h e Ε τ Ο ο r o o m - t e m p e r a t u r e i s o t h e r m is p r e s e n t e d i n F i g u r e 4. T h e c r i t i c a l t e m >erature seems to b e s o m e w h a t b e l o w 25 ° C , i n d i c a t i n g t h a t E r C o H a , is ess s t a b l e t h a n t h e E r C o ^ ^ . T h e r o o m - t e m p e r a t u r e p l a t e a u pressures a r e s h o w n i n T a b l e V . T h e s e v a l u e s i n d i c a t e t h a t t h e s t a b i l i t y of t h e h y d r i d e s i n these c o m p o u n d s decreases w i t h a n i n c r e a s e i n l a n t h a n i d e a t o m i c n u m b e r a n d also w i t h the c o b a l t - t o - l a n t h a n i d e r a t i o . T h e s t a b i l i t y c h a n g e w i t h p h a s e is seen i n C l i n t o n ' s e x p e r i m e n t s o n Ρ Γ Ο Ο ^ . ( 2 8 ) , except t h a t P r C o a n d P r C o s t a b i l i t i e s are r e v e r s e d . T h e y are v e r y s i m i l a r , h o w e v e r . δ

1

5

2


3

Table V .

Comparison of E q u i l i b r i u m Pressures at Room Temperature Ternary

Equilibrium Pressure (atm)

Hydride

PrCo H 5 PrCoaH ErCo H ErCo H 5

0.9 10" ~ 4 0.09

0

4

e

5

3

3

There is no plateau, indicating that the critical temperature is below room tem perature. The composition and pressure are inferred from the inflection point. β

B o t h observations seem r e a s o n a b l e . A s t h e l a n t h a n i d e r a d i u s d e creases, t h e i n t e r s t i t i a l sites w i l l b e c o m e s m a l l e r , a n d t h u s less v o i d s p a c e is a v a i l a b l e f o r the h y d r o g e n atoms. A s t h e t r a n s i t i o n m e t a l - t o - l a n t h a n i d e a t o m i c r a t i o increases, there is less a t o m - a t o m contact b e t w e e n h y d r o g e n a n d t h e l a n t h a n i d e , w h i c h f o r m s the m o r e stable b i n a r y h y d r i d e . Conclusions T h e use of p r e v i o u s l y p u b l i s h e d e m p i r i c a l theories does n o t p r o v i d e r e l i a b l e estimates of e q u i l i b r i u m pressures of t e r n a r y h y d r i d e s . E i t h e r a s u b s t a n t i a l m o d i f i c a t i o n of these theories or a n o t h e r a p p r o a c h is r e q u i r e d . H i g h pressure e x p e r i m e n t s h a v e s h o w n t h e existence of

LaCo H . 5

9

T h i s h y d r o g e n c o m p o s i t i o n is t w i c e the v a l u e p r e v i o u s l y m e a s u r e d a n d greater t h a n a n y c o m p o u n d w i t h t h e C a C u

5

s t r u c t u r e , i.e., L a N i H . 7 . 5

e

C o m p a r i s o n s of c u r r e n t E r C o e H * d a t a w i t h p r e v i o u s l y p u b l i s h e d results f o r P r C o , P r C o , a n d E r C o 5

3

8

s h o w t h a t h y d r i d e s t a b i l i t y decreases

w i t h l a n t h a n i d e a t o m i c n u m b e r a n d w i t h i n c r e a s i n g a t o m r a t i o of t r a n sition metal-to-lanthanide metal. Acknowledgments T h e a u t h o r s w i s h to t h a n k H e r m a n L e i d e r , w h o p e r f o r m e d m a n y of t h e c a l c u l a t i o n s a n d p a r t i c i p a t e d i n i m p o r t a n t discussions of subjects i n this p a p e r .


296

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Literature Cited 1. Libowitz, G. G., J. Nucl. Mater. (1960) 2, 1. 2. Mueller, W. M., Blackledge, J. P., Libowitz, G. G., Eds., "Metal Hydrides," Academic, New York, 1968. 3. Lewis, F. Α., "The Palladium Hydrogen System," Academic, New York, 1967. 4. "Investigation of Hydriding Characteristics of Intermetallic Compounds," Denver Research Institute, University of Denver: Report LAR-55, Nov. 15, 1961; DRI-2059, Oct. 15, 1962. 5. Newkirk, H. W., "A Literature Study of Metallic Ternary and Quaternary Hydrides," UCRL-52110, Aug. 2, 1976, Lawrence Livermore Labora tory, Livermore, CA. 6. Messer, C. E., Eastman, J. C., Hers, R. G., Maeland, A. J., Inorg. Chem. (1964) 3, 776. 7. Messer, C. E., Hardcastle, K., Inorg. Chem. (1964) 3, 1327. 8. Moyer, R. O., Jr., Stanitski, C., Tanaka, J., Kay, M., Kleinberg, R., J. Solid State Chem. (1971) 3, 541. 9. Thompson, J. S., Moyer, R. O., Jr., Lindsay, R., Inorg. Chem. (1975) 14, 1866. 10. Zijlstra, H., Chem. Technol. (1972) 2, 280. 11. van Vucht, J. H . N., Kuijpers, F. Α., Bruning, H . C. A. M., Philips Res. Rep. (1970) 25, 133. 12. Kuijpers, F. Α., van Mal, H. H., J. Less-Common Met. (1971) 23, 395. 13. van Mal, Η. H., Buschow, K. H . J., Kujpers, F. Α., J. Less-Common Met. (1973) 32, 289. 14. Wallace, W. E., Rao, V. U. S., "Thermal, Structural and Magnetic Studies of Metals and Intermetallic Compounds," Annual Report to ERDA, Contract Ε (11-1)-3429, June 1, 1975. 15. Toma, H., "Rare-Earth Info. Ctr. News," X, No. 1, Mar. 1, 1975, Iowa State Univ., Ames, Iowa. 16. Pearson, W. B., "The Crystal Chemistry and Physics of Metals and Alloys," Wiley-Interscience, New York, 1972. 17. Kuijpers, F. Α., Loopstra, Β. O., J. Phys. Chem. Solids (1974) 35, 301. 18. Miedema, A. R., de Boer, F. R., de Chatel, P. F., J. Phys. F. (1973) 3, 1558. 19. Miedema, A. R., J. Less-Common Met. (1973) 32, 117. 20. Miedema, A. R., Boom, R., de Boer, F. R., J. Less-Common Met. (1975) 41, 283. 21. van Mal, H. H., Buschow, K. H . J., Miedema, A. R., J. Less-Common Met. (1974) 35, 65. 22. Flanagan, T. B., Oates, W. Α., Ber. Bunsenges. Phys. Chem. (1972) 76, 706. 23. Buschow, K. H. J., van Mal, Η. H., Miedema, A. R., J. Less-Common Met. (1975) 42, 163. 24. Lakner, J. F., Steward, S. Α., Uribe, F., "High Pressure Hydrogen Appa ratus for PCT Studies to 700 MPa at 200°C. Preliminary Results on LaCo Hydride at 21°C," UCRL-52039, Feb. 27, 1976, Lawrence Liver more Laboratory, Livermore, CA. 25. Kuijpers, F. Α., Philips Res. Rep. Suppl., 1973, No. 2. 26. Buschow, K. H. J., Z. Metallkd. (1966) 57, 728. 27. Wernick, J. H., Geller, S., Acta Crystallogr. (1959) 12, 662. 28. Clinton, J., Bittner, H., Oesterreicher, H., J. Less-Common Met. (1975) 41, 187. 29. Takeshita, T., Wallace, W. E., Craig, R. S., Inorg. Chem. (1974) 13, 2282. 5


16. STEWARD ET AL. Hydrogen in Intermetallic Compounds 297 RECEIVED August 16, 1976. This work was performed under the auspices of the U.S. Energy Research & Development Administration under contract No. W-7405-Eng-48.


This report was prepared as an account of work sponsored by the United States Government. Neither the United States nor the United States Energy Research & Development Administration, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accu racy, completeness or usefulness of any information, apparatus, product or process disclosed, or represents that its use would not infringe privately-owned rights.


Solid State Chemistry of Energy Conversion and Storage

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