THE ELECTRICAL RESISTIVITIES OF SOLUTIONS OF Li22Si5 AND OF Li22Ge5 IN LIQUID LITHIUM

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THE ELECTRICAL RESISTIVITIES OF SOLUTIONS OF Li22Si5 AND OF Li22Ge5 IN LIQUID LITHIUM

P. Hubberstey, A. Dadd

To cite this version:

P. Hubberstey, A. Dadd. THE ELECTRICAL RESISTIVITIES OF SOLUTIONS OF Li22Si5 AND OF Li22Ge5 IN LIQUID LITHIUM. Journal de Physique Colloques, 1980, 41 (C8), pp.C8-531-C8-534.

�10.1051/jphyscol:19808134�. �jpa-00220232�

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JOURNAL DE PHYSIQUE CoZZoque C8, suppl&ment au n08, Tome 41, aoCt 1980, page C8-531

THE ELECTRICAL R E S I S T I V I T I E S OF SOLUTIONS O F L i Z 2 S i 5 AND OF L i 2 2 G e 5 IN LIQUID LITHIUM

P . Hubberstey and A.T. Dadd

Inorganic Chemistry Department, ~ n i v e r s i t y o f Nottingham, Nottingham, NG7 2110, U.K.

INTRODUCTION

S o l u t i o n s of t h e r m a l l y s t a b l e , s t r o n g l y bonded i n t e r m e t a l l i c compounds in l i q u i d a l k a l i metals a r e of both t e c h n o l o g i c a l importance and academic i n t e r e s t . Liquid l i t h i u m , l i t h i u m a l l o y s and l i t h i u m compounds a r e p r e s e n t l y b e i n g c o n s i d e r ed a s c a n d i d a t e s f o r t h e b r e e d i n g medium of f u t u r e D

-

T f u e l l e d thermonuclear r e a c t o r s ; l y 2 t h e poss- i b l e use of l i q u i d l i t h i u m a s t h e primary c o o l a n t i n t h e s e r e a c t o r s i s a l s o b e i n g c o n s i d e r e d . l y 2

Academic i n t e r e s t i n t h e s e s o l u t i o n s i s f o s - t e r e d by t h e i n c r e a s i n g evidence which s u g g e s t s t h a t t h e s o l u t i o n s p a r t i a l l y r e t a i n t h e s t r u c t u r a l and e l e c t r o n i c p r o p e r t i e s of t h e s o l i d s t a t e i n t e r - m e t a l l i c compounds. Thus, r e c e n t l y determined thermodynamic p r o p e r t i e s of L i

-

1 n Y 3 L i

-

T I , 3 L i

-

p b Y 4 L i

-

E i i Y 3 Na

-

^L+aY5Na

-

T1 and Na 6

-

^Sn⁷

s o l u t i o n s a r e c o n s i s t e n t w i t h t h e e x i s t e n c e of a s s - o c i a t e s i n t h e s o l u t i o n s . Furthermore, 7 ~ i and

Knight s h i f t and e l e c t r i c a l r e s i s t i v i t y s t u d i e s of L i

-

^{I n}s o l u t i o n s 8 i n d i c a t e t h e forma- t i o n of a l o o s e l y bound L i In compound i n t h e

3 l i q u i & phase.

As p a r t of our c o n t i n u i n g s t u d y of t h e physics and chemistry of s o l u t i o n s formed by Group IV elements i n l i q u i d a l k a l i

metal^,^-'^

we r e p o r t i n t h i s paper e l e c t r i c a l r e s i s t i v i t y d z t a f o r s o l u t i o n s of L i M ( M = S i o r Ge ) i n l i q u i d

22 5

l i t h i u m ( 0.00 $ x _SL

.

⁶0.0165; 0.00 ,<xGe< 0.0872 )

.

The r e s i s t i v i t y d a t a a r e n o t only of i n t e r e s t , per

se, b u t a r e used t o e l u c i d a t e t h e chemistry of t h e s e s o l u t i o n s . Thus, s o l u b i l i t y d a t a f o r Li22M5 i n l i q u i d l i t h i u m a r e r e p o r t e d , t o g e t h e r w i t h t h e r e a c t i o n s of t h e s e s o l u t i o n s w i t h L i N.

3

EXPERIMXNTAL

The a p p a r a t u s and procedure f o r t h e measure- ment of t h e r e s i s t a n c e of l i q u i d metal s o l u t i o n s h a s been d e s c r i b e d previously.10 The s o l u t i o n s were prepared, i n s i t u , e i t h e r ( f o r L i

-

^Li22M5~ 0 1 ~ -

t i o n s ) by weighing i n t h e a p p r o p r i a t e Group I V element ( S i , Koch L i g h t , 99.999$, 0.10g; Ge, Koch L i g h t 99.999,$, 0.25g ) under argon, o r ( f o r L i

-

^{L i}^N s o l u t i o n s ) by exposing a known volume of

3

4 3 n i t r o g e n gas ( Air P r o d u c t s , 99.98$, 1 0 mm a t S.T.P. ) t o t h e l i q u i d l i t h i u m ( Koch L i g h t , b9.9@

j o g )

.

^Argon⁽Air P r o d u c t s , 99.9% ) was used t o p r o t e c t t h e l i q u i d m e t a l a t a l l times. Lithium, n i t r o g e n and argon, were p u r i f i e d a s d e s c r i b e d

p r e v i o u s l y ; 1 3 s i l i c o n and germanium were used with- o u t f u r t h e r p u r i f i c a t i o n .

The r e s i s t a n c e of t h e s o l u t i o n s was monitored c o n t i n u o u s l y u s i n g a v e r s i o n of t h e c a p i l l a r y method. R e s i s t i v i t i e s were c a l c u l a t e d from c a l i b r a - t i o n and sample r e s i s t a n c e d a t a and t h e dimensions of t h e c a p i l l a r y . 'Ghereas t h e r e s i s t i v i t i e ? , of t h e L i

-

^{L i} ^M s o l u t i o n s were determined a s a f u n c t i o n

22 5

of temperature under c o n s t a n t c o n c e n t r a t i o n condi- t i o n s , t h o s e of L i

-

^{L i M}

-

^{L i}^Ns o l u t i o n s were

22 5 3

determined a s a f u n c t i o n of c o n c e n t r a t i o n .

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19808134

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C8-532 JOURNAL DE PHYSIQUE

Figure 2 :- a e s i s t i v i t y

-

composition isotherms f o r more concentrated ( x _Ge~ 0 . 0 8 7 2 ) L i

-

^{L i Ge} s o l u t i o n s . Temperatures

22 5

( K ) given a g a i n s t t h e curves.

Figure 1 :- R e s i s t i v i t y

-

composition i s o t h e m s f o r d i l u t e ( x M 4 0.0165 ) L i

-

^{L i}₂₂^M₅

( M = S i o r Ge ) s o l u t i o n s . Tempera- t u r e s ( K ) given a g a i n s t t h e curves.

RESULTS AM) DISCUSSION

R e s i s t i v i t i e s of L i

-

^{L i} @ S o l u t i o n s 22 5

R e s i s t i v i t y d a t a were obtained a s a f u n c t i o n of temperature f o r 1 4 Li

-

L i S i ₂₂ ₅( 0.00 (xSi

<

0.0165 ) and 26 L i

-

^{L i Ge}₂₂ ₅⁽^O.OO<x_Ge

<

^0.0872 ⁾

s o l u t i o n s . R e s i s t i v i t y

-

composition isotherms were c o n s t r u c t e d f o r d i l u t e s o l u t i o n s ( 0.00 (x _M

5

0.0165 ) of both s o l u t e s i n t h e temperature range 575 (T/K (775; s e l e c t e d isotherms a r e presented i n Figure 1. Over t h e s e l i m i t e d c o n c e n t r a t i o n ranges, t h e two s o l u t e s cause a n e f f e c t i v e l y l i n e a r i n - crease i n t h e r e s i s t i v i t y of l i t h i u m with i n c r e a s - ing concentration. Consequently, p r e c i s e r e s i s t i v -

i t y values (

%,am

) a r e given a s a f u n c t i o n of com- p o s i t i o n ( x. ) by equation ( 1 ) ; v a l u e s of t h e r e s -

1 t

q = 9. + k.xtj

111 ( 1)

i s t i v . i t y of pure l i t h i u m ( go

,am

) , t h e c o n s t a n t , A , s t a n d a r d d e v i a t i o n s ( o,Rm ) and t h e r e l e v a n t composition ranges a r e c o l l e c t e d i n Table 1.

R e s i s t i v i t y

-

composition isotherms were a l s o c o n s t r u c t e d f o r more concentrated L i

-

^{L i Ge} ^sol-

22 5 u t i o n s ( 0.00 (xGe ( 0.0872 ) i n t h e temperature range 725 (T/K ( 8 3 5 ; s e l e c t e d isotherms a r e presented i n Figure 2. Although l i n e a r a t very d i l u t e c o n c e n t r a t i o n , t h e s e isotherms e x h i b i t a n i n c r e a s - i n g g r a d i e n t with i n c r e a s i n g s o l u t e concentration.

These curves can be represented adequately by equa- t i o n (2) ; values of g,, 6, and t h e r e l e v a n t compos-

t

= ?. + 1.b 10-5xGe + L 10-kx 3 (2) i t i o n ranges a r e c o l l e c t e d i n Table 2.

Consideration of t h e d a t a shows t h a t L i Ge 22 5

i s marginally more e f f e c t i v e i n i n c r e a s i n g t h e

(4)

max. x Ge

Table 1 :- c o e f f i c i e n t s i n t h e

t -

x e q u a t i o n (1) Table 3 :- Values of t h e u n i t r e s i s t i v i t y i n c r e a s e

-

^M

P r e c i p i t a t i n g phases w i t h l i t h i u m a s s o l v e n t LiH Li20 L i N L i S i L i Ge

3 22 5 22 5

-

^{L i} ^Pb

-22 5

4.9 2.1* 7.0 10.4 11.2

-

^9.0

P r e c i p i t a t i n g phases with sodium a s s o l v e n t

NaH Na20

- -

^NaGe ^Na₁₅^Sn₄ ^Na₁₅^Pb₄

4.6 2.0*

- -

^8.6 ^11.8 ^11.2

*

e x t r a p o l a t e d d a t a value.

The c l a s s i c a l Faber

-

^Ziman⁽n e a r l y f r e e e l e c t r o n ) t r e a t m e n t of t h e e l e c t r i c a l r e s i s t i v i t y

( 1 0 8 p/nm ) f o r s o l u t e s i n l i q u i d a l k a l i m e t a l s a t 673 K.

L i

-

Li S i s o l u t i o n s 22 5

Table 2 :- C o e f f i c i e n t s i n t h e 9

-

^x e q u a t i o n (2) of b i n a r y a l l o y s mono- and p o l y v a l e n t m e t a l s g i v e s Ge

( 7 2 5 750 775 800 825 835 a p

-

xM i s o t h e r m which f o l l o w s t h e p a t t e r n shown T/K

log./'rn 8 1 0 " ~

l o

8 u/nm max. xSi

575 625 675 725 775

27.38 28.78 30.06 31.23 32.29

10.25 10.30 10.35 10.40 10.50

0.042 0.048 0.047 0.053 0.062

0.0020 0.0050 0.0112 0.0165 0.0165

r e s i s t i v i t y of l i q u i d l i t h i u m . Comparison of t h e from t h e r e s u l t s of t h e thermodynamic and e l e c t r i c - L i

-

^{L i Ge} s o l u t i o n s

22 5

l 0 ' % k m

lo8a/hm

max xGe

u n i t r e s i s t i v i t y i n c r e a s e s ( i.e., t h e i n c r e a s e i n a l r e s i s t i v i t y s t u d i e s d i s c u s s e d i n t h e i n t r o d u c - r e s i s t i v i t y , a t x M = 0.01 ), w i t h d a t a f o r o t h e r s o l - t i o n . I n t e r m e t a l l i c compounds between a l k a l i m e t a l s

u i d s t a t e ; t h i s model h a s been developed r e c e n t l y 3 1 ° 2 3 31*78 32*29 32*79 33'21 33.40

0.11 0.13 0.19 0.22 0.22 0.25

0.026 0.037 0.051 0.066 0.085 0.087

u t e s i n l i t h i u m i s e f f e c t e d i n Table 3. Of t h e sol- and t h e Group elements ( e.g., L i M ) a r e very 22 5

i n F i g u r e 2. The a l t e r n a t i v e , somewhat more q u a l i t - a t i v e model assumes compound f o r m a t i o n i n t h e l i q -

u t e s examined, L i M have t h e g r e a t e s t e f f e c t .

22 5 s t a b l e . T h i s s t a b i l i t y i s i n d i c a t i v e of s t r o n g bond These h i g h v a l u e s a r e c h a r a c t e r i s t i c o f a l k a l i i n g , p o s s i b l y c o v a l e n t but more probably i o n i c , metal s o l u t i o n s c o n t a i n i n g Group I V elements, s i m i l - w i t h i n t h e s e s p e c i e s ; both t y p e s of bonding

TU.

a r v a l u e s b e i n g observed f o r s o l u t i o n s of Li22Pb5 g i v e e l e c t r o n l o c a l i s a t i o n . If t h e e l e c t r o n i c p r o p i n l i t h i u m and NaGe, Na Sn and Na i n sodium e r t i e s of t h e i n t e r m e t a l l i c compounds a r e r i t a i n e d

15 4 15 4

( Table 3 )

.

i n t h e l i q u i d , i t i s f e a s i b l e t h a t e l e c t r o n l o c a l - The r e s u l t s must be considered w i t h i n t h e i s a t i o n w i l l occur r e s u l t i n g i n abnormally h i g h c o n t e x t of t h e e n t i r e L i

-

^M⁽^M⁼S i , Ge ) system* r e s i s t i v i t i e s a t t h e s o l u t i o n composition r e l a t i n g Two models, one based on t h e n e a r l y f r e e e l e c t r o n t o t h e s e compounds (

%i

⁼^0.815 ). The q

-

^xM

t h e o r y , t h e o t h e r assuming compound formation i n i s o t h e r m would t h u s b e expected t o be s i m i l a r t o t h e l i q u i d , can be proposed t o ac'count f o r t h e r e - t h a t shown i n F i g u r e 2.

s u l t s . Although based on q u i t e d i v e r s e assumptions, S o l u b i l i t i e s of L i M i n L i q u i d L i t h i m

22-5

-

t h e y g e n e r a t e s i m i l a r 9

-

xM isotherms. Such an i s o - D i s c o n t i n u i t i e s i n t h e

p -

T d a t a occur a t t h e m i s shown schematically i n F i g u r e 2 ( I n s e t ) t h e boundary s e p a r a t i n g t h e single-phase ( l i q u i d ) t h e r e s i s t i v i t y r i s e s s t e e p l y from t h e l i t h i u m r e g i o n from t h e two-phase ( l i q u i d + Li22M5 ) v a l u e t o a l a r g e maximum a t

3.

= 0.8 ( thereby region. The v a r i a t i o n of t h e temperature ( T/K ) g i v i n g t h e very h i g h u n i t r e s i s t i v i t y i n c r e a s e s ) of t h e d i s c o n t i n u i t y w i t h s o l u t i o n composition followed by a g r a d u a l d e c r e a s e t o t h e germanium ( xM ) i s a measure of t h e s o l u b i l i t y of L i M i n

22 5

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JOURNAL DE PHYSIQUE

7.2 x lo-%m(mol$ N)-I b u t i n a decrease, g r a d i e n t --

xlo-e ⁰⁰ ⁰⁰⁰⁵ ^OQlO ⁰⁰¹⁵ ¹⁰⁰ ^{O W} ⁰⁰¹⁰ ^bole ~ o m x lo-=

20

10

-

A' 00185 0

I I I I Î Î Î

00 OOOJ 0010 bo15(W 0005 OO(0

W'5 X~ W20

Figure 3 :- R e s i s t i v i t y d a t a f o r Li

-

^{Li M}_{22 5}

_-

_Li3N

s o l u t i o n s a t 725 K.

lithium. The d a t a can be represented by e q u a t i o n s ( 3 ) and (4). The remarkable s i m i l a r i t y i n t h e

I n x S i = 5 . 5 4 8 - 6 7 7 5 / T 5 0 0 ( ~ / ~ ( 7 0 0 (3) In X ~ e = 5.459

-

^6630/T 530(T/K(715 (4) L i M s o l u b i l i t i e s may be a t t r i b u t e d t o . t h e sim-

22 5

i l a r s t a b i l i t i e s of t h e i n t e r m e t a l l i c compounds.

R e s i s t i v i t i e s of L i

-

^{L i} ^M

-

L i N S o l u t i o n s 22 5 -3

The i n t e r a c t i o n s between L i M and L i N i n

22 5 3

l i t h i u m a t 725 K have been e l u c i d a t e d using elec- t r i c a l r e s i s t i v i t y techniques; t h e r e s u l t s a r e de- p i c t e d i n Figure 3. S o l u t i o n of L i Ge i n l i t h i u m

22 5

gave a l i n e a r r e s i s t i v i t y i n c r e a s e , g r a d i e n t = l l . 2 5 x 10-8nm(mol$ ~ e ) - l ; subsequent a d d i t i o n of L i N gave a f u r t h e r l i n e a r i n c r e a s e , g r a d i e n t =

3 -8 -1

7.2 x 1 0 flm(mol% N)

.

Since t h e s e g r a d i e n t s a r e those a n t i c i p a t e d f o r t h e s o l u t i o n of LiZ2Ge5 and L i N s e p a r a t e l y i n l i t h i u m , it i s concluded t h a t

3

no i n t e r a c t i o n occurs.

S o l u t i o n of L i S i i n . l i t h i u m gave t h e ex- 22 5

pected r e s i s t i v i t y i n c r e a s e with g r a d i e n t 10.40 x

-8 -1

1 0 R m(mol$ ~ i )

.

Subsequent a d d i t i o n of Li3N, however, r e s u l t e d n o t i n an i n c r e a s e , g r a d i e n t

= -3.3 x 1 0 ~ m ( m o l $ N)". -8 Tnis decrease i s a t t r i b - uted t o t h e l o s s of L i S i from s o l u t i o n by reac-

22 5

t i o n with t h e added L i N t o form a LixSi N t e r n a r y

3 Y

=

compound. I f i t i s assumed t h a t the product i s in- s o l u b l e i n l i t h i u m , t h e r e s i s t i v i t y decrease i n d i c - a t e s t h a t i t s Si:N r a t i o i s ca. 1:4. Preliminary X-ray powder d i f f r a c t i o n s t u d i e s of t h e s o l i d prod- u c t i s o l a t e d from t h e r e a c t i o n system by d i s t i l l - a t i o n of excess l i t h i u m a t 875K confirms t h i s r a t i o i n d i c a t i n g t h a t t h e product may be Li8SiN This

4' system i s t h u s analogous t o t h e Li

-

^Li2C2

-

^{L i}₃^N

system, from which t h e complex s a l t , Li NCN, can be 2

i s o l a t e d ; t h u s f a r , no o t h e r s i m i l a r complex s a l t s have been shown t o be s t a b l e t o l i q u i d lithium.u'

The a u t h o r s would l i k e t o thank t h e S.R.C. f o r t h e award of a maintenance g r a n t ( t o A.T.D. )

BEFJBENCES

1. J.H.DeVan, J.Nuclear Mater. ,85&86(1979)249.

2. R.E.Gold,D.~.Smith, Proc.2nd.Int.Conf.Liquid Metals i n Energy Prodn., i n t h e p r e s s . 3. B. Predel, G. Oehme , ~ . ~ e t a l l k u n d e , 7 0 ( 1 9 7 9 ) 618, 4. B.Frede1. G.Oehme, Z.Metallkunde,70(1979)450.

5. S.Tamaki, N.E.Cusack, J.Phys.F. ,9(1979)403.

6. E.Mairova, A.G.Morashevskii, Russ.J.Pnys.Chem., 51 ( 1977) u+16.

7. M.Rivier, A.Pelton, J.Electrochem.Soo.,l25 (1973) 1377.

8. C.van d e r Marel,E.Brandenburg,W.van d e r Lugt, J . P ~ Y S . F . ,8(1978)~273.

9. P.Hubberstey, R.Pulham, J.C.S.Faraday I , 7 0 (1974) 1631.

10. P.Hubberstey, R.FuIham, J . C .S.Dalton, (1972) 819.

11. P.Hubberstey, R.Pulham, J.C.S.Dalton, (1974)1541 12. P.Hubberstey, A.Castleman, J.Electrochem.Soc.,

119(1972) 963,967

13. P.Adams ,M.Down ,P.Hubbers t e y ,R. Pulham, J.C. S.

Faraday I , 73 (1977) 230.

14. M.Down,M.Haley,P.Hubberstey,R.Pulham,A.Thunder, J.C.S.Dalton,(1978)lJ+07.