AS DEPOSITED
P. ROGL TABLE 8
concentration for series of M]` xM~Si2 alloys, after Evers et al. (1978)
Composition, x Phase (*) a-axis c-axis
Lu I _x~rx~12
0.00 N P 4.303(3) 13.65(1 )
0.10 NP 4.314(6) 13.68(2)
0.25 N P 4.336(6) 13.69(2)
0.50 N P 4.365(10) 13.76(3)
0.75 NP 4.402(6) 13.80(2)
0.90 HP 4.419(6) 13.81(2)
1.00 HP 4.438(3) 13.83(1)
Ca I _:,Eu~Si 2
0.00 HP 4.283(3) 13.52(1)
0.10 HP 4.285(3) 13.54(1)
0.25 NP 4.288(3) 13.58(1)
0.50 NP 4.295(3) 13.59(1)
0.75 N P 4.299(3) 13.63(1 )
0.90 N P 4.301 (3) 13.64(1 )
1.00 N P 4.303(3) 13.65(1)
(*~ HP = high pressure, NP = normal pressure.
Eu Ca Si
N o t e r n a r y p h a s e d i a g r a m exists f o r t h e E u - C a - S i s y s t e m ; t h e s t a b i l i t y r a n g e o f t h e c~-ThSi2-type s t r u c t u r e w a s i n v e s t i g a t e d a l o n g t h e c o n c e n t r a t i o n s e c t i o n C a l _ ~ E u x S i 2 in t h e p r e s s u r e r a n g e u p to 40 k b a r ( q u e n c h e d f r o m 1 0 0 0 - 1 5 0 0 ° C ) . F o r s a m p l e p r e p a r a t i o n , see E u - S r - S i .
A l i m i t e d solid s o l u t i o n C a 1 x E u x S i 2 , 0.2 ~<x ~< 1, w a s o b s e r v e d at n o r m a l p r e s s u r e s , w h e r e a s a c o m p l e t e h o m o g e n e o u s r a n g e exists at 40 k b a r , w i t h a l i n e a r v a r i a t i o n o f the u n i t cell d i m e n s i o n s v e r s u s c o n c e n t r a t i o n (see T a b l e 8). A s t a t i s t i c a l d i s t r i b u t i o n o f C a , E u a t o m s w a s a s s u m e d ( X - r a y p o w d e r d a t a ) .
Reference
Evers, J., O. Oehlinger and A. Weiss, 1978, 3. Less-Common Metals 60, 249.
E u - C o Si
T h r e e t e r n a r y c o m p o u n d s h a v e b e e n c h a r a c t e r i z e d in t h e E u C o Si s y s t e m . E u C o 9 S i 2 is t e t r a g o n a l w i t h t h e B a C d l l - t y p e o f s t r u c t u r e [ I 4 1 / a m d , a = 9.798(5) a n d c = 6.330(10)]. A t o m i c o r d e r i n g w a s r e p o r t e d b y B o d a k a n d G l a d y s h e v s k i j (1969) to b e s i m i l a r to C e N i s 6Si2. 4 ( X - r a y p o w d e r a n a l y s i s o f a r c - m e l t e d alloys).
A c c o r d i n g to X - r a y p o w d e r d a t a b y M a y e r a n d F e l n e r (1973) EuCo0.sSil. 5 w a s o b s e r v e d to c r y s t a l l i z e w i t h t h e A1B2-type o f s t r u c t u r e ( P 6 / m m m , a = 4.046, c - 4.500). S a m p l e s w e r e p r e p a r e d b y m e l t i n g in A 1 2 0 3 c r u c i b l e s in a n i n d u c t i o n f u r n a c e u n d e r a r g o n .
PHASE EQUILIBRIA 77 M a y e r a n d F e l n e r (1977) p r e p a r e d EuCo2Si 2 w i t h the ThCr2Si 2-type of s t r u c t u r e ( I 4 / m m m , a = 3.921(5), c = 9.850(5); X - r a y p o w d e r analysis). F o r s a m p l e p r e p a r a - tion, see E u C u 2 S i 2. S t a r t i n g m a t e r i a l s were 99.9% pure. F r o m M 6 s s b a u e r effect m e a s u r e m e n t s Eu was said to a p p e a r in two v a l e n c e states. T h e t h e r m o e l e c t r o m o t i v e force ( 8 0 - 1 0 5 0 K) was i n v e s t i g a t e d b y Levin (1981).
References
Bodak, O.I. and E.I. Gladyshevskij, 1969, Dopov. Akad. Nauk Ukr. RSR, Ser. A 5, 452.
Levin; E.M., 1981, Ukr. Fiz. Zh. 26(3), 407.
Mayer, I. and I. Felner, 1973, J. Solid State Chem. 8, 355.
Mayer, I. and I. Felner, 1977, J. Phys. Chem. Solids 38, 1031.
Eu Cu-Si
M a y e r a n d F e l n e r (1973) studied the valency o f Eu in an EuCu0.sSil.5 a l l o y with the A1B2-type of s t r u c t u r e ( P 6 / m m m , a = 4 . 0 8 0 , c = 4 . 4 6 6 ) b y m e a n s of 151Eu M/Sssbauer effect a n d X - r a y p o w d e r d i f f r a c t i o n m e a s u r e m e n t s . Eu was f o u n d to be divalent. S a m p l e s were p r e p a r e d b y m e l t i n g in an A1203 c r u c i b l e u n d e r argon. The m i n i m u m p u r i t y o f the starting e l e m e n t s was 99.9%.
E u C u 2 S i 2 crystallizes with the T h C r 2 S i z - t y p e of s t r u c t u r e ( M a y e r a n d Felner, 1977; X - r a y p o w d e r d a t a ) . L a t t i c e p a r a m e t e r s were r e p o r t e d for an E u C u S i 3 alloy [a = 4.118(5), c = 9.990(5)] c o n t a i n i n g a s e c o n d p h a s e EuCu0.sSil. s with the AIB 2- type. U n p u b l i s h e d r e s e a r c h by F e l n e r as q u o t e d b y B a u m i n g e r et al. (1973) s h o w e d t h a t the C u a n d Si a t o m s in E u C u 2 S i 2 are d i s t r i b u t e d a m o n g the 4d a n d 4e sites of I 4 / m m m with the C u a t o m s p r e f e r i n g the 4d sites. M 6 s s b a u e r d a t a reveal Eu in the d i v a l e n t a n d t r i v a l e n t state. S a m p l e s were p r e p a r e d b y m e l t i n g in A1203 c r u c i b l e s in an i n d u c t i o n f u r n a c e at - 1600 o C u n d e r A r a n d s u b s e q u e n t h e a t i n g for - 30 m i n at s o m e w h a t lower t e m p e r a t u r e . Starting m a t e r i a l s were 99.9% pure. F r o m X - r a y a b s o r p t i o n s p e c t r o s c o p y m e a s u r e m e n t s at 77 a n d 300 K on an a r c - m e l t e d E u C u 2 S i 2 sample, two a b s o r p t i o n p e a k s were o b s e r v e d , c o r r e s p o n d i n g to two different v a l e n c e states of Eu. T h e p o p u l a t i o n of Eu z+ d e c r e a s e s at l o w e r t e m p e r a t u r e s ( H a t w a r et al., 1980) a n d was also m o n i t o r e d b y the q u a d r u p o l a r i n t e r a c t i o n o f Cu as a f u n c t i o n of t e m p e r a t u r e ( S a m p a t h k u m a r a n et al., 1980). See also B a u m i n g e r et al. (1973), B u s c h o w et al. (1977) a n d Scherzberg et al. (1984). F o r a c o m p r e h e n s i v e l i t e r a t u r e review on the p h y s i c a l p r o p e r t i e s of E u C u 2 S i 2, see G u p t a et al. (1981) and Sales a n d V i s w a n a t h a n (1976). T h e t h e r m o e l e c t r o m o t i v e force was m e a s u r e d b y Levin (1981).
F o r X - r a y a b s o r p t i o n s p e c t r o s c o p y ( L 3 - a b s o r p t i o n edge), see P a d a l i a et al. (1983).
B o d a k et al. (1971) m e n t i o n e d the existence of a c o m p o u n d EuCu~ 6Sil. 4 w i t h the C e N i S i 2-type.
References
Bauminger, E.R., D. Froindlieh, 1. Nowik, S. Ofer, I. Felner and I. Mayer, 1973, Phys. Rev. Len. 30(21), 1053.
Bodak, O.l., E.1. Gladyshevskij and Ya.M. Kalvijak, 1971, Tesizy Dokl. Vses. Konf. Kristallokhim.
Intermet. Soedin, Lvov, p. 40.
Buschow, K.H.J., M. Campagna and G.K. Wertheim, 1977, Solid State Commun. 24, 253.
78 P. ROGL
Gupta, L.C., E.V. Sampathkumaran, ~. Vijayaraghavan, P.D. Prabhawalkar and B.D. Padalia, 1981, Phys. Rev. B23(18), 4283; and 1981, in: Valence Fluctuations in Solids, eds. L.M. Falicov, W. Hanke and M.B. Maple (North-Holland, Amsterdam) pp. 241,439.
Hatwar, T.K., R.M. Nayak, B.D. Padalia and M.N. Ghatikar, 1980, Solid State Commun. 34, 617.
Levin, E.M., 1981, Ukr. Fiz. Zh. 26(3), 407.
Mayer, I. and I. Felner, 1973, J. Solid State Chem. 8, 355.
Mayer, I. and I. Felner, 1977, J. Phys. Chem. Sol. 38, 1031.
Padalia, B.D., T.R. Hatwar, and M.N. Ghatikar, 1983, J. Phys. C16, 1537, Sales, B.C. and R. Viswanathan, 1976, J. Low Temp. Phys. 23(3,4), 449.
Sampathkumaran, E.V, L.C. Gupta and R. Vijayaraghavan, 1980, J. Magn. Magn. Mater. 15-18, 977; see also 1979, Phys. Rev. Lett. 43(16), 1189; 1979, J. Phys. C12, 4323.
Scherzberg, A., Ch. Sauer, U. K6bler, W. Zinn and J. R6hler, 1984, Solid State Commun. 49(11), 1027.
E u - F e - S i
EuFe2Si 2 crystallizes with the T h C r 2 S i a - t y p e of structure: I 4 / m n a m , a - 3.970(5) a n d c = 10.120(5) ( M a y e r a n d Felner, 1977; X - r a y p o w d e r analysis). Samples were p r e p a r e d b y m e l t i n g i n a n i n d u c t i o n f u r n a c e at - 1 6 0 0 ° C i n a n A1203 crucible u n d e r argon. F o r a n n e a l i n g the samples were k e p t at a s o m e w h a t lower t e m p e r a t u r e t h a n the h e a t i n g t e m p e r a t u r e for 30 min. M 6 s s b a u e r d a t a were i n t e r p r e t e d b y the existence of " t w o well-defined valencies of Eu". T h e electrical resistivity was 9.5 m$2 cm at 300 K ( F e l n e r a n d Mayer, 1973). T h e t h e r m o e l e c t r o m o t i v e force i n the r a n g e b e t w e e n 9 0 - 1 0 0 0 K was investigated b y L e v i n (1981).
T h e A1B2-type structure was n o t observed i n the c o n c e n t r a t i o n section EuFe~Si 2 x ( M a y e r a n d Felner, 1973).
References
Felner, I. and 1. Mayer, 1973, Mater. Res. Bull. 8, 1317.
Levin, E.M., 1981, Ukr. Fiz. Zh. 26(3), 407.
Mayer, I. and 1. Felner, 1973, J. Solid State Chem. 8, 355.
Mayer, I. and I. Felner, 1977, J. Phys. Chem. SoL 38, 1031.
Eu Gd Si
M a y e r a n d F e l n e r (1971) studied the c o n c e n t r a t i o n section Gd5 x E u x S i 3 at various c o m p o s i t i o n s x = 0.25, 0.5, 0.75 a n d 1.0, b y m e a n s b y X - r a y p o w d e r analysis, a n d in the case of 155Gd5Si3 a n d G d 4 E u S i 3 b y m e a n s of M 6 s s b a u e r m e a s u r e m e n t s . Mixtures of a total weight of 5 0 0 - 7 0 0 mg were p r e p a r e d i n a d r y - b o x a n d i n d u c t i o n - h e a t e d at - 1600 ° C u n d e r argon.
All c o m p o u n d s were claimed to b e h o m o g e n e o u s a n d to crystallize with the M n s S i 3 - t y p e of structure, P 6 3 / m c m . Lattice p a r a m e t e r s were as follow: G d s S i 3 : a = 8.52, c = 6.39; Gd4.75Eu0.25Si3: a = 8.50, c = 6.39; Gd4.sEu0.sSi3: a = 8.49, c = 6.38; Gd4.zsEu0.75Si3: a = 8 . 4 9 , c = 6 . 3 9 ; Gd4.0Eul.0Si3: a = 8 . 4 9 , c = 6 . 3 7 ; the c o m p o s i t i o n was accurate to _+0.5 a / o . Samples with a Eu c o n c e n t r a t i o n higher t h a n 20 a / o were said to be m u l t i p h a s e with c o m p l e x X - r a y p o w d e r p a t t e r n s . F r o m the decreasing lattice p a r a m e t e r values as well as a smaller G d i s o m e r shift in G d 4 E u S i 3 , M a y e r a n d F e l n e r (1971) c o n c l u d e d the f o r m a t i o n of G d vacancies, the E u a t o m s b e i n g located interstitially (?) or i n o c t a h e d r a l holes ( T i s G e 4 - t y p e ?).
PHASE EQUILIBRIA 79 Reference
Mayer, I. and 1. Felner, 1971, J. Less-Common Metals 24, 243.
E u - Ge- Si
M a y e r a n d T e n d y (1970) m e n t i o n e d u n p u b l i s h e d results o b t a i n e d b y M a y e r a n d Felner, c o n c e r n i n g the c o n c e n t r a t i o n section Eu 5 Gex Si 3 - ~ ( M n 5 Si 3-type, P 6 3 / m c m ).
Reference
Mayer, I. and S. Tendy, 1970, israel J. Chem. 8, 955.
Eu=Ni Si
N o t e r n a r y phase d i a g r a m of the system E u - N i - S i is available yet. A t least eight t e r n a r y c o m p o u n d s were identified (see table 9).
Bodak et al. (1966) were first to report the existence of a c o m p o u n d E u N i S i 3 with the BaA14-type of structure ( I 4 / m m m ) . M a y e r a n d F e t n e r (1977) c o n f i r m e d the existence of EuNiSi3, a n d i n a d d i t i o n p r o v i d e d s t r u c t u r a l d a t a for a c o m p o s i t i o n E u N i 2 S i 2. R e f i n e m e n t of X-ray p o w d e r d i f f r a c t i o n d a t a of E u N i 2 S i 2 yielded the lowest R - v a l u e ( R = 0.218) for the ThCr2Si2-type of a r r a n g e m e n t with Eu a t o m s i n 2a), N i i n 4d) a n d Si i n 4e) with z = 0.375(1). I n the case of E u N i S i 3 a statistical o c c u p a t i o n of 2Si + 2Ni in 4e) was o b t a i n e d [Eu i n 2a), Si i n 4d)]. This type of a t o m i c o r d e r with s y m m e t r y I 4 / m m m is c o n s i s t e n t with the P r N i G a 3 - t y p e of structure (BaA14-type derivative). MOssbauer d a t a at 300 K a n d 4.2 K i n d i c a t e d d i v a l e n t E u in EuNiSi3, b u t two valencies for E u i n E u N i 2 S i 2. T h e thermoelectro°
motive force i n E u N i z S i 2 ( 8 0 - 1 0 5 0 K ) has b e e n m e a s u r e d by Levin (1981) a n d electrophysical p r o p e r t i e s ( t e m p e r a t u r e d e p e n d e n c e of electrical resistance, t h e r m o - electrical coefficient a n d m a g n e t i c susceptibility) of E u N i z S i 2 were r e p o r t e d b y Levin et al. (1977).
References
Bodak, O.I. and E.I. Gladyshevskij, 1969a, Dopov. Akad. Nauk Ukr. RSR, Ser. A 5, 452.
Bodak, O.I. and E.I. Gladyshevskij, 1969b, Dopov. Akad. Nauk Ukr. RSR, Ser A 12, 1125.
Bodak, O.I. and E.I. Gladyshevskij, 1969c, Kristallografiya 14(6), 990.
Bodak, O.I., E.I. Gladyshevskij and P.I. Kripyakevieh, 1966, Ivz. Akad. Nauk SSSR, Neorg. Mater. 2(12), 2151.
Gladyshevskij, E.I., P.I. Kripyakevich and OA. Bodak, 1966, Acta Crystallogr. A21, 80; and Z. Anorg.
Allg. Chem. 344, 95.
Levin, E.M., 1981, Ukr. Fiz. Zh. 26(3), 407.
Levin, E.M., R.V. Lutsiv, E.I. Gladyshevskij and O.I. Bodak, 1977, Fiz. Elektron. Resp. Mezhved.
Nauch-tekhn. Sbor. 15, 59.
Mayer, I. and I. Felner, 1973, J. Solid State Chem. 8, 355.
Mayer, I. and I. Felner, 1977, J. Phys. Chem. Sol. 38, 1031.
E u - P d - S i
A c c o r d i n g to X - r a y powder d i f f r a c t i o n d a t a b y Ballestracci (1976), E u P d 2 S i 2 is b o d y - c e n t e r e d t e t r a g o n a l with the o r d e r e d T h C r z S i z - t y p e , I 4 / m m m , a = 4.190 a n d
80 P. R O G L , TABL~ 9
Formation and structural data of ternary compounds Eu Ni Si.
Compound Structure type Lattice Preparation, Refs. Purity
Space group parameters Characterization Density
Eu3Ni6Si 2 Ce3Ni6Si 2 a = 8.913(2) arc, Qu(Ni) Eu 98.4
ord. Ca3Ag s 800 o C, 2 weeks G1KB, 66 Ni 99.99
lm3m PXD Si 99.99
EuNis.6Si 2.4 Ce2NilTSi5 a = 9.801(5) are(Ar), Qu BoG, 69a Ni 99.91
(BaCdlt) c = 6.216(10) 800 ° C, 250 h, PXD Si 99.99
I 4 1 / a m d atom order as for
CeNi s.~Si 2.4
EuNis.6Si4. 4 Ce2NitvSi 9 a =11.04(1) ~*) arc(Ar), Qu BoG, 69b Eu 99.2 30 a / o Si ~*~ (NaZn13-deriv.) c = 11.48(1) 800 ° C, 100 h, PXD Ni 99.99
14/mcm Si 99.99
Eu(Ni,Si)l 3 NaZn13 a = 11.18 arc(Ar), Qu BoG, 69b Eu 99.2
37-45 a / o Si Fm3c 800 o C, 100 h, PXD Ni 99.99
Si 99.99 Eu 98.4 Ni 99.8 Si 99.99
"EuNiSi3" (**) PrNiGa 3 a = 4.143(10) arc(Ar) BoGK, 66
1 4 / m m m c = 9.625(10) PXD
a = 4.150(5) induction heating
c = 9.636(5) at 1600 o C (Ar) in AI203 MaF, 77 30 min, PXD refinement
99.9
EuNizSi 2 (**) ThCr2Si 2 a = 4.008(5) induction heating
1 4 / m m m c = 9.636(5) at 1600 ° C (Ar) in A1203 MaF, 77 99.9 30 min, PXD refinement
EuNiSi z CeNiSi 2 a = 4.137(2) arc(Ar) BoG, 69c Eu 98.4
Cmcm b =16.562(10) PXD Ni 99.8
c = 4.002(2) Si 99.99
EuNi0.sSil. 5 AIB 2 a = 4.034 induction melting MaF, 73 99.9
P 6 / m m m c = 4.496 in A1203 (Ar), 30 min, 1600 o C, PXD (*) For a correct setting of the bct unit cell a = 7.808 (a =
ao/~/2).
(**) Physical properties as well as atom ordering are discussed in the text.
c = 9 . 9 8 ; f o r s a m p l e p r e p a r a t i o n , s e e C e P d 2 S i 2. T h e t e m p e r a t u r e v a r i a t i o n o f t h e l a t t i c e p a r a m e t e r s , t h e m a g n e t i c s u s c e p t i b i l i t y a n d 151Eu M i S s s b a u e r m e a s u r e m e n t s i n d i c a t e a m i x e d v a l e n c y s y s t e m w i t h a c o n t i n u o u s v a l e n c e t r a n s i t i o n n e a r 1 4 0 K ; s e e , e.g., S a m p a t h k u m a r a n et al, ( 1 9 8 1 ) (fig. 2 3 ) , C r o f t et al. ( 1 9 8 2 ) , N a g a r a j a n e t al.
( 1 9 8 1 ) ( X A S - d a t a ) . F r o m t h e s e i n v e s t i g a t i o n s t h e a v e r a g e v a l e n c e o f E u i o n s i n E u P d 2 S i 2 w a s d e r i v e d t o b e - 2 . 3 a t 3 0 0 K a n d - 2 . 7 a t 1 2 0 K . A c o n t i n u o u s v a l e n c e t r a n s i t i o n w i t h a n i n c r e a s e o f t h e a v e r a g e v a l e n c y o f E u u p t o p r e s s u r e s o f 48 k b a r h a s a l s o b e e n f o u n d f r o m m e a s u r e m e n t s o f e l e c t r i c a l r e s i s t i v i t y a n d t h e r m o e l e c - t r i c p o w e r ; t h e E u v a l e n c y r e m a i n e d c o n s t a n t i n t h e p r e s s u r e r a n g e o f 48 t o 7 0 k b a r ;
PHASE EQUILIBRIA 81
9.875 t I 9.865~- o< 9.855}-
c r LtJ LI/
7r
4.22 cr ~n 4.20
LId (._) I-- I--
<
4.18_J
i r [ i i i
O
o o
EuPd2Si 2 (ThCr2Si 2-type) Sampathkumeran
et a l . ,
1 3 _ _ _ _ _ _ . 1 I I I