TEMPERATURE,K
P. ROGL TABLE 26a
and individual thermal parameters B for the ScRe2Si 3 structure, after Pecharskij et al.
(1979).
Atoms, site x y z B
Sc 80 0.1706(12) (*~ 0.1312(8) 0.4880(29) 0.90(10)
Sc 80 0.3241(14) 0.1425(8) 0.9970(27) 0.90(10)
Re 8f) 0.3877(3) 0.2049(1) 0.4858(12) 0.17(4)
Re 8f) 0.1221(4) 0.2008(1) 0.9922(14) 0.85(6)
Re 4d) 0 0.0848(1) 0.2534(13) 0.34(2)
Re 4e) 1 / 2 0.1044(2) 0.7444(12) 0.48(3)
Re 4c) 0.2653(2) 0 0.2110(12) - 0.27(9)
Re 4c) 0.2165(3) 0 0.7175(13) 0.39(4)
Si 8f) 0.3733(12) 0.0752(10) 0.5003(31) 1.10(12)
Si 8f) 0.1568(12) 0.0874(11) -0.0036(37) 1.02(8)
Si 8f) 0.2688(17) 0.2570(11) 0.2365(36) 1.20(14)
Si 4d) 0 0.3544(9) 0.2169(34) 1.01(12)
Si 4e) 1 / 2 0.1309(12) 0.2901(33) 1.00(11)
Si 4d) 0 0.2057(12) 0.3649(29) 1.90(19)
Si 4e) 1 / 2 0.2791(11) 0.3342(32) 1.21(12)
Si 4c) 0.1116(13) 0 0.3386(33) 1,19(13)
Si 4c) 0.3896(16) 0 0.9115(31) 1.14(11)
S c 3 R e 2 S i 3 c r y s t a l l i z e s w i t h t h e S c 3 R e 2 S i 3 - t y p e o f s t r u c t u r e w i t h t h e s p a c e g r o u p B 2 a n d l a t t i c e p a r a m e t e r s : a = 1 9 . 6 0 4 ( 6 ) , b = 1 3 . 7 4 1 ( 5 ) , c = 5 . 3 3 9 ( 1 ) a n d 7 = 1 2 5 . 9 2 ( 2 ) ° . T h e c r y s t a l s t r u c t u r e h a s b e e n r e f i n e d b y m e a n s o f X - r a y s i n g l e c r y s t a l
Atomic coordinates and individual thermal
TABLE 26b
parameters B for the Sc 3 Re 2Si3 structure, after Pecharskij et al. (1979).
Atoms, site x y z B
Sc 4c) 0.1219(9) (*) 0.2092(14) 0.2333(31) 0.88(9)
Sc 4c) 0.3812(8) 0.3113(12) 0.4794(28) 0.94(7)
Sc 4c) 0.3413(9) 0.398(13) - 0.0395(32) 0.80(6)
Sc 4c) 0.0807(7) 0.3987(11) - 0.0020(27) 0.76(9)
Sc 4c) 0.1705(8) 0.1255(12) 0.7158(31) 0.72(8)
Sc 4c) 0.4215(8) 0.0916(13) 0.7369(30) 0.66(7)
Re 4c) 0.0238(1) 0.1654(2) 0.7284(12) 0.22(2)
Re 4c) 0.0257(1) 0.6752(3) 0.4954(14) 0.28(4)
Re 4c) 0.2634(2) 0.0320(2) 0.5023(11) 0.21(3)
Re 4c) 0.2631(1) 0.5322(2) 0.6854(14) 0.02(4)
Si 4c) 0.1190(14) 0.3737(17) 0.4922(41) 1.06(12)
Si 4c) 0.2676(16) 0.3473(18) 0.4612(39) 1.21(9)
Si 4c) 0.3963(11) 0.1352(14) 0.2370(36) 0.97(14)
Si 4c) 0.2248(10) 0.1307(12) 0.2128(42) 1.18(7)
Si 2a) 0 0 - 0.0361(48) 1.16(12)
Si 2a) 0 0 0.5036(49) 1.28(10)
Si 2b) 0 1 / 2 0.2452(43) 1.56(14)
Si 2a) 0 1 / 2 0.7439(46) 1.29(16)
(*) The figures in brackets are the standard deviations.
PHASE EQUILIBRIA 183 counter data to a reliability value of R = 0.092 (Pecharskij et al., 1979). Single crystals were obtained from an arc-melted specimen with composition (in a / o ) 8c37.5 Re25Si 37.5. This c o m p o u n d was claimed to exist at 800°C. The atom parameters are listed in table 26a.
ScRezSi 3 crystallizes with the ScRezSi3-type of structure: Amm2, a = 14.486(3), b = 5.2397(13). Pecharskij et al. (1979) refined the crystal structure by means of single crystal counter data; the obtained reliability value was R = 0.102. Single crystals were obtained from an arc-melted alloy with composition (in a / o ) Sc16.6Re33.3Si50 . This c o m p o u n d was claimed to exist at 800°C. The atomic parame- ters are listed in table 26b.
The structure types of "ScReSi2" and "ScsRe3Si9" have not been evaluated yet.
References
Pecharskij, V.K., 1979, Autoreferat Dis. Kand. Khim. (abstract of thesis, Russian) (Nauk, Lvov) 23 p.
Pecharskij, V.K., O.I. Bodak and E.I. Gladyshevskij, 1978, Dopov. Akad. Nauk Ukr. RSR, Ser. A, 755.
Pecharskij, V.K., O.I. Bodak and E.I. Gladyshevskij, 1979, Kristallografiya 24, 757.
Sc-Rh-Si
A partial isothermal section (40-100 a / o Si, fig. 45) of the S c - R h - S i phase diagram at 1000°C has been derived by Braun et al. (1979) by means of X-ray and metallographic analysis of arc-melted samples, which subsequently were wrapped in Ta foil and heat treated for 7 d and up to 8 weeks at 1000°C in evacuated silica tubes (backfilled with a partial pressure of U H P Ar) and finally quenched in water.
Starting materials were Sc 99.9%, Rh 99.9% and Si 99.99999%. Ten of the annealed
Si
L . _ V \ / v ,
Sc
I000oC I Sc4Rh Sis 2 Sc3Rh2Si9 3 Sc~Rh2Sk
4 Sc6Rh4Si9 5 Sc~Rh4Silo
~ 9 ~ 0 6 Sc3 Rh3Sis 7 Sc Rh Si 2 8 Sc2 Rh3Si4 9 Sc Rh3Si 7
~----~"~ Rh2 Si 3
"~R h 4 Si 5
~
hSiRh
Fig. 45. S c - R h - S i , partial isothermal section at 1000°C (50-100 a / o Si). The compound ScRh3Si. 7 (no.
9), obtained at (in a / o ) Sc9.2Rh28.0Si62.9, was earlier called "ScRh3Si6".
184 P. ROGL
alloys were investigated by electron m i c r o p r o b e analysis (10 kV; Sc-, S i K a , R h - L a ) using the composition "Sc3Rh2Si4" ( u n k n o w n structure type) as an internal stan- dard. Some of the annealed samples were said to be in the non-equilibrium condition containing about 5 vol% of a fourth phase.
T h e existence of Sc3Si 5 (defect A1B2-type ) a n d ScSi (CrB-type), of RhSi (MnP- type) and Rh4Si 5 (RhnSis-type) has been c o n f i r m e d as well as the crystal structure of Rh3Si4, which was observed close to the c o m p o s i t i o n of Rh2Si 3. N i n e ternary phases have been established for Si contents higher than 40 a / o Si.
A n additional c o m p o u n d was furthermore observed by Hovestreydt et al. (1982) f r o m arc-melted alloys (see below). T h e crystal structures of Sc 3 R h 2Si9 [po×p = 4.3(1) k g / d m 3 ] , S c 3 R h 2 S i 4 [Pexp = 5.19(6)], " S c 6 R h 4 S i 9 " [Pexp = 4.96(6)], Sc3Rh3Si 5 [Pexp
= 5.50(9)] a n d SczRh3Si 4 [Pe×p = 6.2(1)] have n o t yet been characterized. T h e actual c o m p o s i t i o n of " S c 6 Rh4Si9" as derived by m i c r o p r o b e was Sc 3~.5 Rh 20.6Si 47.9 and thus with equal likelihood might be represented by a formula such as " S c 3 R h 2 S i s " . T h e X - r a y p o w d e r diagrams of " S c 3 R h z S i 4 " and "Sc6Rh4Si9" were claimed to reveal striking similarities in d values and intensities. M i c r o p r o b e m e a s u r e m e n t s indicate a small h o m o g e n e o u s range (14.0-15.5 a / o Rh) for "Sc3Rh2Si9".
I n a later paper by Braun and Segre (1980) the crystal structure of " S c 4 R h S i s "
was suspected to be isotypic with the crystal structure of ScCo0.25Sil.75 with the ZrSi2-type. F u r t h e r m o r e " S c a R h S i s " is s u p e r c o n d u c t i n g below T~ = 1.8 K.
Braun et al. (1980) characterized the crystal structure of ScsRh4Sil0 f r o m X-ray p o w d e r diffractometer data: ScsCo4Sil0-type of structure, P 4 / m b m , a = 12.325(6), c = 4.032(3), Px = 4.97(2),
Pexp
= 4.90(6). S%Rh4Sil0 is superconducting at T~ = 8.5 K (Braun and Segre, 1980). The investigation of phase equilibria involving ScsRh4Sil0 at 1150°C (samples annealed for 2 - 7 d) a n d at 800°C (samples annealed for 7 d), revealed that ScsRh4Sil0 is a h i g h - t e m p e r a t u r e c o m p o u n d absent at 800°C but stable at temperatures higher than 800°C. T h u s " S c 4 R h S i s " and ScRhSi 2 were observed to f o r m a two-phase equilibrium at 800°C, whereas phase equilibria at 1150°C are consistent with those at 1000°C.ScRhSi z is a derivative structure of Re3B and crystallizes with the ordered Y Z n 3 - t y p e of structure [Pnma, a = 6.292(4), b = 4.025(4), c = 9.517(5), Px = 5.62(1), Pexp = 5.36(7) kg/dm3]. T h e crystal structure has been refined by C h a b o t et al.
(1981a) f r o m single crystal counter d a t a with a reliability value as low as R = 0.052.
A c c o r d i n g l y the a t o m parameters were: Sc in 4c) 0.2385(4), 1 / 4 , 0.3181(3); R h in 4c) 0.5832(2), 1 / 4 , 0.9008(1); Si in 4c) 0.9573(6), 1 / 4 , 0.8413(4); Si in 4c) 0.2318(7), 1 / 4 , 0.0282(4). N o superconductivity was observed for temperatures a b o v e T n = 1 K.
C h a b o t et al. (1981b) refined the crystal structure of ScRh3Si 7 with the ScRh3Si7-type by means of single crystal counter data; the space group is R 3 c with hexagonal cell units a N = 7.5056(6) a n d c H = 19.691(4), Px = 5.706, Poxp = 5.81(7).
T h e reliability value obtained was R = 0.037. I n the earlier p a p e r by B r a u n et al.
(1979) this c o m p o u n d was denoted as " S c R h 3 S i 6 " . N o superconductivity was reported.
H o v e s t r e y d t et al. (1982) characterized the crystal structure of ScRhSi f r o m single crystal c o u n t e r data: TiNiSi-type of structure, Pnma, a = 6.4736(7), b = 4.0500(3)
P H A S E E Q U I L I B R I A 185 a n d c = 7.2483(9). A t o m p a r a m e t e r s according to R = 0.052 were as follows: Sc in 4c) 0.0094(6), 1 / 4 , 0.6893(5); R h in 4c) 0.1568(2), 1 / 4 , 0.0620(2) a n d Si i n 4c) 0.2857(8), 1 / 4 , 0.3851(7). Samples were o b t a i n e d b y arc m e l t i n g u n d e r argon.
References
Braun, H.F. and C.U. Segre, 1980, Solid State C o m m u n . 35, 735.
Braun, H.F., G. Burri and L. Rinderer, 1979, J. Less-Common Metals 68, P1.
Braun, H.F., K. Yvon and R.M. Braun, 1980, Acta Crystallogr. B36, 2397.
Chabot, B., H.F. Braun, K. Yvon and E. Parth6, 1981a, Acta Crystallogr. B37, 668.
Chabot, B., N. Engel and E. Parth6, 1981b, Acta Crystallogr, B37, 671.
Hovestreydt, E., N. Engel, K. Klepp, B. Chabot and E. Parth6, 1982, J. Less-Common Metals 86, 247.
S c - R u - S i
B r a u n a n d Segre (1980) reported the existence of a c o m p o u n d Sc3Ru2Si 6. F o r sample p r e p a r a t i o n , see Sc3Os2Si 6. X - r a y p o w d e r d i f f r a c t i o n p a t t e r n s were t e n t a - tively i n d e x e d on the basis of a n o r t h o r h o m b i c u n i t cell [a = 8.939(8), b = 9.061(8), c = 4.175(7), 0x = 4.96(2)] with a close r e s e m b l a n c e to the u n i t cell of ScsIr4Sil0:
a ~ b(Sc3Ru2Si6) ~ ( ! / 2 / 2 ) a ( S c s I r 4 S i l 0 ) a n d c(Sc3Ru2Si6) ~ c(ScsIr4Sil0); T n = 1.2 K.
A c c o r d i n g to X - r a y p o w d e r diffraction data of H o v e s t r e y d t et al. (1982) ScRuSi has the Z r N i A l - t y p e of structure (ordered Fez P-type ) with space group P 6 2 m a n d lattice p a r a m e t e r s a = 6.851(3), c = 3.423(2). Alloys were p r e p a r e d by arc m e l t i n g u n d e r a r g o n a n d s u b s e q u e n t a n n e a l i n g at 1000°C for 1 2 weeks. Starting m a t e r i a l s were Sc 99.9%, R u 99.99%, Si 99.999%.
References
Braun, H.F. and C.U. Segre, 1980, Solid State Commun. 35, 735.
Hovestreydt, E., N. Engel, K. Klepp, B. Chabot and E. Parth6, 1982, J. Less-Common Metals 86, 247.
S c - S m - S i
A c c o r d i n g to X - r a y p o w d e r data b y M o k r a a n d B o d a k (1979) SmScSi is tetrago- n a l with the CeScSi-type of structure (ordered C a 2 A s - t y p e , I 4 / m m m ) a n d lattice p a r a m e t e r s a = 4.255(5) a n d c = 15.56(2). F o r s a m p l e p r e p a r a t i o n , see CeScSi.
Reference
Mokra, I.P. and O.1. Bodak, 1979, Dopov. Akad. N a u k Ukr. RSR, Ser.
A,
312.S m - A g - S i
A c c o r d i n g to a n X - r a y p o w d e r analysis by M a y e r et al. (1972) the c o m p o u n d SmAg2Si 2 crystallizes with the ordered ThCr2Si2-type of structure [ I 4 / m m m , a = 4.169(5) a n d c = 10.69(5)]. F o r s a m p l e p r e p a r a t i o n , see LaAg2Si 2. Alloys were m u l t i p h a s e also c o n t a i n i n g some excess Ag as well as small a m o u n t s of SmSi 2 phases (tetragonat a n d / o r o r t h o r h o m b i c modification?).
186 P. ROGL Reference
Mayer, I., J. Cohen and I. Felner, 1972, J. Less-Common Metals 29, 221 and 1973, J. Less-Common Metals 30, 181.
Srn - A 1- Si
N o t e r n a r y d i a g r a m is a v a i l a b l e for the s y s t e m S m - A 1 - S i ; the f o r m a t i o n of a c o m p o u n d S m A l a S i 2 , however, was r e p o r t e d b y M u r a v y o v a et al. (1972). F r o m p o w d e r X - r a y d i f f r a c t i o n studies SmA12Si 2 was f o u n d to a d o p t the L a 2 0 2 S - t y p e of s t r u c t u r e w i t h the s p a c e g r o u p P 3 m l a n d z = 1. T h e a t o m i c o r d e r a n d p a r a m e t e r s as d e r i v e d for the i s o s t r u c t u r a l c o m p o u n d CaA12Si 2 were f o u n d to b e a p p r o p r i a t e for the p o w d e r i n t e n s i t y c a l c u l a t i o n ; 1 R ( S m ) in l a ) 0,0,0; 2 A1 in 2d) 1 / 2 , 2 / 3 , z = 0.63 a n d 2 Si in 2d) z = 0.27. T h e l a t t i c e p a r a m e t e r s were a = 4.19 a n d c = 6.62 A.
S a m p l e s were p r e p a r e d b y arc m e l t i n g the p o w d e r c o m p a c t s u n d e r argon, f o l l o w e d b y a h e a t t r e a t m e n t in e v a c u a t e d silica t u b e s for 1 5 0 - 7 5 0 h at 500°C. S t a r t i n g m a t e r i a l s were Sm 98.5%, A1 99.98% a n d Si 99.99%°
Reference
Muravyova, A.A., O.S. Zarechnyuk and E.I. Gladyshevskij, 1972, Visn. L'vivsk. Univ. Ser. Khim. 13, 14.
S m - A u - S i
T h e c r y s t a l s t r u c t u r e o f S m A u 2 S i 2 has b e e n r e f i n e d b y M a y e r et al. (1973) f r o m X - r a y p o w d e r d i f f r a c t i o n data. S m A u 2 S i 2 a d o p t s the o r d e r e d T h C r 2 S i 2 - t y p e of s t r u c t u r e w i t h space g r o u p I 4 / m m m a n d l a t t i c e p a r a m e t e r s : a = 4.260(5) a n d c = 10.17(5). R a n d o m d i s t r i b u t i o n o f A u a n d Si a t o m s was e x c l u d e d a n d a t o m p a r a m e t e r s with r e s p e c t to the o b t a i n e d r e l i a b i l i t y value R = 0.044 were given as follows: A u in 4d) a n d Si in 4e) z = 0.390. F o r s a m p l e p r e p a r a t i o n , see L a A u 2 S i 2.
F r o m s u s c e p t i b i l i t y m e a s u r e m e n t s in the r a n g e of 4.2 K to 300 K F e l n e r (1975) Jl para o b s e r v e d a n t i f e r r o m a g n e t i c o r d e r i n g at T N = 15.9 K. P a r a m a g n e t i c d a t a w e r e ~eff
= 0.63/x B a n d 0p = 2.5 K.
References
Felner, I., 1975, J. Phys. Chem. Sol. 36, 1063.
Mayer, I., J. Cohen and 1. Felner, 1973, J. Less-Common Metals 30, 181.
S m - C o Si
A t least six t e r n a r y p h a s e s h a v e b e e n c h a r a c t e r i z e d in the S m - C o - S i system.
M a y e r a n d T a s s a (1969) i n v e s t i g a t e d the p h a s e e q u i l i b r i a at 7 0 0 - 8 0 0 ° C in the S m C o x S i 2 _ x system. F o r x < 0.4 the T h S i 2 - t y p e of s t r u c t u r e was o b s e r v e d , a n d for x > 0.4 the X - r a y p o w d e r p a t t e r n s were s a i d to b e c o m p l e x . A t a c o m p o s i t i o n SmCo0.4Sil. 6 the h e x a g o n a l A1B2-type o f s t r u c t u r e was f o u n d to b e s t a b l e ( a = 4.017, c = 4.180). In s i m i l a r i t y to the X - r a y d i f f r a c t i o n d a t a of NdFe0.4Sil. 6 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 o a n d Si a t o m s in the sites o f P 6 / m m m was a s s u m e d . F o r s a m p l e p r e p a r a t i o n , see GdCo0.4Sil. 6.
PHASE EQUILIBRIA 187 S m C o S i is i s o s t r u c t u r a l with the P b F C l - t y p e of s t r u c t u r e : P 4 / n m m , a = 4.010(3), c = 6.776(5) ( B o d a k et al., 1970; X - r a y p o w d e r analysis). F o r a t o m p a r a m e t e r s a n d s a m p l e p r e p a r a t i o n , see CeFeSi.
SmCo2Si 2 c r y s t a l l i z e s with the o r d e r e d T h C r 2 S i 2 - t y p e of structure: I 4 / m m m , a = 3.934, c = 9.845, p× = 7.07 k g / d m 3 (Rossi et al., 1978); 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 t i o n a n d etching c o n d i t i o n s , see Y C o z S i 2.
B o d a k a n d G l a d y s h e v s k i j (1969) r e p o r t e d SmCo9Si 2 to crystallize w i t h the B a C d l l - t y p e o f s t r u c t u r e : I 4 a / a m d , a = 9.775(5), c = 6.306(10) ( X - r a y p o w d e r a n a l y - sis of a r c - m e l t e d alloys). A t o m i c o r d e r i n g is q u i t e s i m i l a r to CeNis.6Si2. 4.
Pelizzone et al. (1982) i n v e s t i g a t e d the s t r u c t u r a l a n d m a g n e t o c h e m i c a l b e h a v i o r o f S m C o S i 2 with the C e N i S i 2 - t y p e [Cmcm, a = 4 . 0 9 7 ( 2 ) , b = 16.358(7) a n d c = 4.010(2)]. S a m p l e s were p r e p a r e d b y arc m e l t i n g a n d s u b s e q u e n t a n n e a l i n g in sealed q u a r t z c a p s u l e s at 1 0 0 0 ° C for one week. T h e m a g n e t i c s u s c e p t i b i l i t i e s are char- a c t e r i z e d b y a t y p i c a l V a n Vleck p a r a m a g n e t i s m o f closely s p a c e d m u l t i p l e t s ; m a g n e t i c o r d e r i n g o c c u r s at 4.0 K.
W i t h o u t a n y f u r t h e r details, G l a d y s h e v s k i j a n d B o d a k (1973) r e p o r t e d the ex- istence of a c o m p o u n d S m C o S i 3 p r o b a b l y i s o t y p i c w i t h C e C o S i 3 ( a = 4.085, c = 9.536, BaA14-derivative; as cited b y G l a d y s h e v s k i j a n d B o d a k , 1982).
References
Bodak, O.I. and E.I. Gladyshevskij, 1969, Dopov. Akad. Nauk Ukr. RSR, Ser. A 5, 452.
Bodak, O.I., E.I. Gladyshevskij and P.I. Kripyakevich, 1970, Zh. Strukt. Khim. 11(2), 305.
Gladyshevskij, E.I. and O.I. Bodak, 1973, in: Khim. Met. Splavov, N.M. Zhavoronkov ed. (Nauka, Moscow, USSR) p. 46.
Gladyshevskij, E.I. and O.I. Bodak, 1982, Kristallokhim. Intermet. Soedin, Redkozemel, Metallov, Lvov, Vysha Schola.
Mayer I. and M. Tassa, 1969, J. Less-Common Metals 19, 173.
Pelizzone, M., H.F. Braun and J. Miiller, 1982, J. Magn. Magn. Mater. 30, 33.
Rossi, D., R. Marazza and R. Ferro, 1978, J. Less-Common Metals 58, 203.
S m - Cu-Si
R i e g e r a n d P a r t h 6 (1969a) i n v e s t i g a t e d the o c c u r r e n c e o f the A1B2-type s t r u c t u r e in a r c - m e l t e d alloys w i t h c o m p o s i t i o n SmCu0.67Sil.33 ( a = 4.044, c = 4.117) a n d S m C u S i ( a = 4.082, c = 4.075). I n a c c o r d a n c e w i t h the X - r a y p o w d e r i n t e n s i t i e s Si a n d Cu a t o m s were r e p o r t e d to s t a t i s t i c a l l y o c c u p y the 2d site of s p a c e g r o u p P 6 / m m m . F r o m a r c - m e l t e d alloys a n n e a l e d at 750°C, I a n d e l l i (1983) r e c o r d e d the f o r m a t i o n o f S m C u S i w i t h the o r d e r e d N i z I n - t y p e [ s u p e r s t r u c t u r e of the A1B2-type, P 6 3 / m m c , a = 4.185(1), c = 7.669(4)]. T h e s u p e r s t r u c t u r e r e f l e c t i o n s were s a i d to be faint. I a n d e l l i (1983) o b t a i n e d d i f f e r e n t results t h a n R i e g e r a n d Parth6 (1969a), in t h a t the n e w p h a s e was suspected to be the l o w - t e m p e r a t u r e m o d i f i c a t i o n a n d a c c o r d i n g l y a t h e r m a l analysis up to 1400°C r e v e a l e d a t h e r m a l arrest at 1210°C.
F o r details in s a m p l e p r e p a r a t i o n a n d p u r i t i e s of the s t a r t i n g m a t e r i a l s , see Y b C u S i . T h e c o m p o u n d S m C u z S i 2 crystallizes with the T h C r 2 S i 2 - t y p e of structure. X - r a y p o w d e r d a t a given b y R i e g e r a n d Parth6 (1969b) were as follows: a = 4.025(6), e = 9.928(10) a n d I 4 / m m m . F o r s a m p l e p r e p a r a t i o n , see Y C u 2 S i 2. N o t e m p e r a t u r e
188 P. R O G L
d e p e n d e n c e was o b s e r v e d for the m a g n e t i c s u s c e p t i b i l i t y of S m C u 2 S i 2 (77 300 K, K i d o et al., 1983). N M R d a t a h a v e b e e n p r e s e n t e d b y S a m p a t h k u m a r a n et al.
(1979). F o r X - r a y a b s o r p t i o n m e a s u r e m e n t s , see P a d a l i a et al. (1983). W i t h o u t d e t a i l s B o d a k et al. (1971) m e n t i o n e d the e x i s t e n c e o f a c o m p o u n d S m C u l . 6 S i l . 4 with the C e N i S i z - t y p e .
References
Bodak, O.I., E.I. Gladyshevskij and Ya.M. Kalvijak, 1971, Tesizy. Dokl. Vses. Konf. Kristallokhim.
Intermet. Soedin, Lvov, p. 40.
Iandelli, A., 1983, J. L e s s - C o m m o n Metals 90, 121.
Kido, H., T. Hoshikawa, M. Shimada and M. Koizumi, 1983. Phys. Stat. Sol. (a) 77, K121.
Padalia, B.D., T.K. Hatwar and M.N. Ghatikar, 1983, J. Phys. Cl6, 1537.
Rieger, W. and E, Parth6, 1969a, Monatsh. Chem. 100, 439.
Rieger, W. and E, Parth6, 1969b, Monatsh. Chem. 100, 444.
S a m p a t h k u m a r a n , E.V., L.C. G u p t a and R. Vijayaraghavan, 1979, J. Phys. C12, 4323.
Srn- F e - Si
A t least f o u r t e r n a r y c o m p o u n d s exist in the S m - F e - S i system.
M a y e r a n d T a s s a (1969) i n v e s t i g a t e d the p h a s e e q u i l i b r i a w i t h i n the section S m F e x S i 2 _ x at 7 0 0 - 8 0 0 ° C . F o r x < 0.4 the T h S i 2 - t y p e s t r u c t u r e was said to b e stable. SmFe0.4Sil. 6 crystallizes with the A1B2-type o f s t r u c t u r e ( a = 4.020, c = 4.165).
I n a n a l o g y to the X - r a y p o w d e r i n t e n s i t y d a t a of NdFe0.4Sil. 6 a s t a t i s t i c a l d i s t r i b u - tion o f Fe, Si a t o m s in the 2d site o f P 6 / m m m was assumed. Both s u b l a t t i c e s in SmFe0.4Sil. 6 are p a r a m a g n e t i c a b o v e 4.2 K ( h i g h - s p i n state); the high value for its m o l a r C u r i e c o n s t a n t o f 4.10 emu was c l a i m e d to b e due to i r o n i m p u r i t i e s . F o r s a m p l e p r e p a r a t i o n , see GdCoo.4Sil. 6, F e l n e r a n d Schieber (1973).
T h e t h e r m a l e x p a n s i o n coefficients h a v e b e e n d e t e r m i n e d b y M a y e r a n d F e l n e r (1972), by m e a n s of h i g h - t e m p e r a t u r e X - r a y d i f f r a c t o m e t r y : a a = 8.9 × 10 - 6 d e g 1, a = 1 8 . 6 × 1 0 6 d e g - t , ~ = 1 2 . 1 × 1 0 6 d e g 1, , / = 3 4 . 5 × 1 0 - 6 deg i ( v o l u m e e x p a n s i o n coefficient). L a t t i c e p a r a m e t e r s c h a n g e as follows: at 25°C, a = 4.076(1), c = 4.263(1); at 430°C, a = 4 . 0 8 9 ( 1 ) , c = 4 . 2 8 3 ( 1 ) ; at 600°C, a = 4 . 0 9 6 ( 1 ) , c = 4.310(1); at 800°C, a = 4.104(1), c = 4.323(1); at 940°C, a = 4.112(1), c = 4.347(1).
S m F e o . 4 N i l . 6 w a s said to d e c o m p o s e at l l 0 0 ° C .
S m F e 2 S i 2 was r e p o r t e d b y F e l n e r et al. (1975) to crystallize with the o r d e r e d T h C r 2 S i z - t y p e of structure: I 4 / m m m , a = 3.952(5), c = 9.985(5) ( X - r a y p o w d e r a n a l y s i s of alloys m e l t e d in a h i g h - f r e q u e n c y furnace). W e a k f e r r o m a g n e t i c o r d e r i n g o c c u r s at T m = 723(5) K. F r o m m a g n e t i z a t i o n a n d M/Sssbauer effect studies m o s t o f the i r o n was c o n c l u d e d to be d i a m a g n e t i c ( - 94%).
S m F e S i crystallizes w i t h the P b F C l - t y p e o f structure: P 4 / n m m , a = 4.031(3), c = 6.829(5) ( B o d a k et al., 1970; X - r a y p o w d e r d i f f r a c t i o n ) . F o r s a m p l e p r e p a r a t i o n , see C e F e S i .
S m 2 F e 3 S i 5 is i s o t y p i c with the s t r u c t u r e t y p e of S%Fe3Sis: P 4 / m n c , a = 10.47(1), c -- 5.55(1) ( X - r a y p o w d e r d i f f r a c t i o n d a t a b y Braun, 1980). F o r s a m p l e p r e p a r a t i o n , see D y z F e 3 S i 5. M/Sssbauer d a t a i n d i c a t e the a b s e n c e o f a m a g n e t i c m o m e n t at the i r o n site ( B r a u n et al., 1981). N o s u p e r c o n d u c t i v i t y was o b s e r v e d a b o v e T n = 1 K.
PHASE EQUILIBRIA 189 L o w t e m p e r a t u r e h e a t c a p a c i t y d a t a r e v e a l m u l t i p l e a n t i f e r r o m a g n e t i c t r a n s i t i o n s at T m = 8.96, 7.35, 6.19 a n d 5.05 K ( V i n i n g a n d S h e l t o n , 1983).
References
Bodak, O.I., E.I. Gladyshevskij and P.I. Kripyakevich, 1970, Zh. Strukt. Khim. 11(2), 305.
Braun, H.F., 1980, Phys. Lett. 75A(5), 386.
Braun, H.F., C.U. Segre, F. Acker, M. Rosenberg, S. Dey and P. Deppe, 1981, J. Magn. Magn. Mater, 25, 117.
Mayer, 1. and I. Felner, 1972, J. Less-Common Metals 29, 25.
Mayer, I. and M. Tassa, 1969, J. Less-Common Metals 19, 173.
Felner, I. and M. Schieber, 1973, Solid State Commun. 13, 457.
Felner, I., I. Mayer, A. Grill and M. Schieber, 1975, Solid State Commun. 16, 1005.
Vining, C.B. and R.N. Shelton, 1983, Phys. Rev. B28(5), 2732.
Sm Ge-Si
M a y e r a n d E s h d a t (1968) i n v e s t i g a t e d t h e c o n c e n t r a t i o n s e c t i o n s S t a G % xSi~
a n d S m G e l . 6 xSix b y m e a n s o f X - r a y p o w d e r d i f f r a c t i o n m e t h o d s . F o r s a m p l e p r e p a r a t i o n , see N d G e 2 xSix. G e - r i c h a l l o y s o f t h e series S m G e z xSix w e r e s a i d to a d o p t t h e T h S i 2 - t y p e o f s t r u c t u r e ( I 4 1 / a m d ) . A l l o y s r i c h e r in Si c r y s t a l l i z e d w i t h t h e o r t h o r h o m b i c G d S i z - t y p e ( I m m a ) . T h e v a r i a t i o n o f l a t t i c e p a r a m e t e r s v e r s u s x is s h o w n in fig. 46a; t h e u n i t cell v o l u m e c h a n g e s l i n e a r l y w i t h x as p r e s e n t e d in fig. 11.
A l l t h e a l l o y s o f t h e S t a G e r . 6 xSix series h a d t h e t e t r a g o n a l T h S i 2 - t y p e o f s t r u c t u r e , w h i c h w a s t e n t a t i v e l y r e l a t e d to a u n i f o r m d i s t r i b u t i o n o f G e a n d Si a t o m s a n d r a n d o m v a c a n c y f o r m a t i o n o n t h e n o n - m e t a l sites (fig. 46b). S e e also N d G e 2 ~Si~.
Reference
Mayer, I. and Y. Eshdat, 1968, Inorg. Chem. 9, 1904.
c , ( A ) ~ _ _
o
1 3 , 8 0 ~ SmSixGez.x
13.72-- ~ o
(A)
1 3 . 5 6 ~ 4 , 1 4
13.481 1 ~ • i ~'~",,~11~ 4.0 6 0 0.4 0.8 1.2 1.6 2.0 X
C:,A
o14.00
SmSi x Gel.e_ x t3.94 ~ c
13.86 - X
0 0.4 0.8 i.2
o(~,) 4.14
t4.00 1.6 X
Fig. 46. Sm Ge-Si, (a) section SmG% xSix and (b) section SmGel.6_:~Si X, lattice parameter variation versus concentration, after Mayer and Eshdat (1968).
190 P. ROGL S m - M n - S i
S m M n 2 S i z crystallizes with the ThCr2Si2-type of structure: I 4 / m m m , a = 3.975, c = 10.520, p× = 6.32 k g / d m 3 (Rossi et al., 1978; X - r a y p o w d e r diffraction). F o r s a m p l e p r e p a r a t i o n , see L a M n 2 S i 2. K n i g e n k o et al. (1977) m e a s u r e d a = 3.964 a n d c = 10.500 (X-ray p o w d e r data). F o r s a m p l e p r e p a r a t i o n , see Y - M n - S i . Szytula a n d Szott (1981) characterized the m a g n e t i c b e h a v i o r b y a n t i f e r r o m a g n e t i c o r d e r i n g at
T N = 398 K a n d ,,para t ~ e f f = 3.3 ~B m o l e - 1 -
S m M n S i is t e t r a g o n a l with the P b F C l - t y p e of structure: P 4 / n m m , a = 4.060, c = 7.215 ( K n i g e n k o et al., 1977; X - r a y p o w d e r data). F o r s a m p l e p r e p a r a t i o n , see Y M n - S i .
R e f e r e n c e s
Knigenko, L.D., I.R. Mokra and O.I. Bodak, 1977, Vestn. Lvov Univ., Ser. Khim. 19, 68.
Rossi, D., R. Marazza, D. Mazzone and R. Ferro, 1978, J. Less-Common Metals 59, 79.
Szytula, A. and I. Szott, 1981, Solid State Commun. 40, 199.
S m N i - S i
N o p h a s e d i a g r a m has b e e n published. A t least eight t e r n a r y c o m p o u n d s exist (see table 27).
M a y e r a n d Tassa (1969) investigated the p h a s e e q u i l i b r i a w i t h i n the c o n c e n t r a t i o n section S m N i x S i 2 x b y m e a n s of X - r a y p o w d e r analysis. F o r x < 0.4 the T h S i 2 - t y p e of s t r u c t u r e was f o u n d to be stable. SmNi0.4Sil. 6 crystallizes with the A1B2-type of s t r u c t u r e (see table 27). I n a n a l o g y to the X - r a y p o w d e r d a t a of NdNi0.4Sil. 6 a statistical d i s t r i b u t i o n of N i / S i a t o m s i n the 2d site of P 6 / m m m was assumed.
N i / S i a t o m ordering, however, seems to b e likely (see also M 6 s s b a u e r d a t a of isotypic LaFe0.4Sil.6).
Levin et al. (1977) reported electrophysical properties of SmNi2S~ 2 ( t e m p e r a t u r e d e p e n d e n c e of electrical resistance, thermoelectric coefficient, m a g n e t i c susceptibility as well as the p r e p a r a t i o n of stoichiometric t h i n films).
R e f e r e n c e s
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, 1959c; Kristallografiya 14 (6), 990.
Bodak, O.I., E.I. Gladyshevskij and P.I. Kripyakevich, 1966, Izv. Akad. Nauk SSSR, Neorg. Mater. 2(12), 2151.
Gladyshevskij, E.I. and O.I. Bodak, 1965, Dopov. Akad. Nauk Ukr. RSR, Ser. A 5, 601.
Gladyshevskij, E.I., P.I. Kripyakevich and O.I. Bodak, 1966, Acta Crystallogr. A21, 80; Z. Anorg. Allg.
Chem. 344, 95.
Klepp, K. and E. Parth~, 1982, J. Less-Common Metals 83, L33.
Levin, E.M., R.V. Lutsiv, E.I. Gladyshevskij and O.I. Bodak, 1977, Fiz. Elektron. Resp. Liezhved.
Nauch-tekn. Sbor. 15, 59.
Mayer, I. and M. Tassa, 1969, J. Less-Common Metals 19, 173.
P H A S E E Q U I L I B R I A TABLE 27
F o r m a t i o n and structural data of ternary c o m p o u n d s S m - N i - S i .
191
C o m p o u n d Structure type Lattice Preparation, Refs. Purity
Space group parameters Characterization
Density
Sm3Ni6Si 2 Ce3Ni6Si 2 a = 8.850(2) arc, Qu(Ni) Sm 97.7
ord. Ca 3 A g s 800 o C, 2 weeks G1KB, 66 Ni 99.99
Im3m PXD Si 99.99
SmNis.6Siz. 4 CezNi17Si 5 a = 9.779(5) arc(At), Qu BoG, 69a Ni 99.91
( B a C d l l ) c = 6.206(10) 800 o C, 250 h, PXD Si 99.99
I 4 1 / a m d atom order as for
CeNis.6Si 2.4
SmNis.6Si4. 4 ~*) Ce2Ni17Si 9 a = 11.02(1) ~*) arc(Ar), Qu BoG, 69b Sm 99.2
- 30 a / o Si (NaZn13-deriv.) c = 11.40(1) 800 o C, 100 h, PXD Bi99.99
I 4 / m c m Si 99.99
Sm(Ni,Si)13 NaZn13 a =11.12(1) arc(Ar), Qu BoG, 69b Sm 99.2
- 37-45 a / o Si Fm3c 800 o C, 100 h, PXD Ni 99.99
Sm3NiSi 2 ~**) G d 3 N i S i 2 a = 11.505(3) arc(Ar), Qu(Ta)
filled Hf3P 2 b = 4.189(3) 800 ° C , 4 weeks KIP, 82
Pnma c = 11.388(3) single crystal study
SmNi2Si 2 ThCrzSi 2 a = 3.997(10) arc(Ar) BoGK, 66
I 4 / m m m c = 9.577(10) PXD
SmNiSi2 CeNiSi 2 a = 4.073(2) arc(Ar)
Cmcm b = 16.423(10) P X D
c = 4.002(2)
SmNi0.4Sil. 6 AIB 2 a = 3.997
P 6 / m m m c = 4.175
Si 99.99 Sm 99.9 Ni 99.99 Si 5N Sm 97.7 Ni 99.8 Si 99.99 Sm 97,7 Ni 99.8 Si 99.99 Sm 99.9 Ni 99.95 Si 99.99 HT in A1203 or
MgO2
i n d u c t i o n heating 1500 ° C , Ar, Qu 700-800 ° C, 2 4 - 9 6 h, P X D
BoG, 69c
MaT, 69
a = 4.002(2) arc(Ar) G1B, 65 Ni99.8
c = 4.160(5) PXD Si 99.99
~*) For a correct setting of the bct unit cell a - 7.793 ( a = ao/~12 ).
~**) The crystal structure of Sm3NiSi 2 (filled-up Hf3Pz-type ) has been refined from X-ray single crystal counter d a t a (Klepp et al., 1982): R = 0.023. A t o m parameters were (all atoms in site 4c of Pnma):
Sm, 0.05775(6), 1 / 4 , 0.37559(6); Sm, 0.21373(7), 1 / 4 , 0.69768(6); Sm, 0.38207(7), 1 / 4 , 0.44029(6);
Ni, 0.1286(2), 1 / 4 , 0.1332(1); Si, 0.3013(3), 1 / 4 , 0.0061(3); Si, 0.4726(4), 1 / 4 , 0.6866(3).
S m - O s - S i
S m O s z S i z i s t e t r a g o n a l w i t h t h e s p a c e g r o u p I 4 / m m m a n d w i t h t h e T h C r z S i z - t y p e o f s t r u c t u r e ( H i e b l e t a l . , 1 9 8 3 ; X - r a y p o w d e r a n a l y s i s ) . T h e l a t t i c e p a r a m e t e r s w e r e
192 P. ROGL
a = 4.1490(5) a n d c = 9.8122(50). F o r s a m p l e p r e p a r a t i o n , see Y O s z S i 2- F o r t e m p e r - a t u r e s a b o v e 25 K, the m a g n e t i c s u s c e p t i b i l i t y c o r r e s p o n d s to a Van Vleck b e h a v i o r of closely s p a c e d m u l t i p l e t s with t*eff" para= 0.47 /X B a n d 0p = 12 K. A n t i f e r r o m a g n e t i c o r d e r was o b s e r v e d at 5 K.
Reference
Hiebl, K., C. Horvath, P. Rogl and M.J. Sienko, 1983, Solid State Common. 48, 211.
S m - P d Si
S m P d 2 S i is o r t h o r h o m b i c with the o r d e r e d F e 3 C - t y p e : P n m a , a = 7.445(3), b = 6.905(2) a n d c = 5.584(2) ( X - r a y p o w d e r d a t a b y M o r e a u et al., 1982). F o r s a m p l e p r e p a r a t i o n , see Y P d 2Si.
A c c o r d i n g to an X - r a y p o w d e r d i f f r a c t i o n i n v e s t i g a t i o n b y Ballestracci (1976) S m P d z S i 2 was o b s e r v e d to crystallize with the o r d e r e d T h C r 2 S i z - t y p e o f structure:
I 4 / m m m , a = 4.160, c = 9.96. F o r s a m p l e p r e p a r a t i o n , see C e P d z S i 2.
References
Ballestraey~ R., 1976, C.R. Acad. Sei. Paris, Ser. B 282, 291.
Moreau, J.~J. Le~oy and D. Paecard, 1982, Acta Crystallogr. B38, 2446.
S m - P t - S i
S m P t S i crystallizes w i t h the L a P t S i - t y p e of structure: I41md , a = 4 . 1 3 0 0 ( 9 ) , c = 14.376(4) ( K t e p p a n d Parth6, 1982; 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 LaPtSi. C o n g r u e n t m e l t i n g b e h a v i o r is i n d i c a t e d .
S m P t 2 S i 2 was r e p o r t e d b y Ballestracci a n d A s t i e r (1978) to c r y s t a l l i z e in a p r i m i t i v e t e t r a g o n a l s y m m e t r y , a = 4.205, c = 9.78 ( X - r a y d i f f r a c t i o n of a l l o y s m e l t e d in a n i n d u c t i o n f u r n a c e u n d e r argon). T h e p r i m i t i v e t e t r a g o n a l c r y s t a l s y m m e t r y w i t h an a t o m i c a r r a n g e m e n t s i m i l a r to the CaBe2Ge2-type was r e c e n t l y c o n f i r m e d f r o m X - r a y p o w d e r d a t a of a r c - m e l t e d a l l o y s (Rogl, 1984): a = 4 . 2 0 4 0 ( 7 ) , c = 9.7751(57), C e P t 2 S i 2 - t y p e .
References
Ballestracci, R. and G. Astier, 1978, C.R. Acad. Sci. Paris, Set. B 286, 109.
Klepp, K. and E. Parth6, 1982, Acta Crystallogr. B38, 1105.
Rogl, P., 1984, Inorg. Chem., to be published.
S m - R e - S i
T h e p h a s e e q u i l i b r i a in the t e r n a r y s y s t e m S m - R e - S i have b e e n i n v e s t i g a t e d b y Pecharskij (1979), b y m e a n s of X - r a y a n a l y s i s of 36 t e r n a r y alloys w h i c h were arc m e l t e d a n d s u b s e q u e n t l y a n n e a l e d in e v a c u a t e d q u a r t z capsules for 400 + 600 h at 8 0 0 ° C a n d finally q u e n c h e d in water. S t a r t i n g m a t e r i a l s were Sm 97.7%, R e 99.99%
a n d Si 99.99%.
S m R e z crystallizes with the M g Z n z-type; the p h a s e relations in the b i n a r y s y s t e m s
PHASE EQUILIBRIA 193
Si
800 °C
Re StoRe2 Sm
Fig. 47. S m - R e - S i , partial isothermal section at 800°C (0 33 a / o Sm). 1: SmRe4Si a, 2: Sm2Re3Sis, 3:
"Sm4ReSis".
S m - S i a n d R e - S i a r e discussed in c o n t e x t with the t e r n a r y systems C e - S m Si a n d Y - R e - S i , respectively. T h e m u t u a l solid solubilities of Sm a n d R e silicides as well as o f S m R e 2 at 800°C were f o u n d to b e small a n d w i t h i n 1 2 a / o of the third c o n s t i t u e n t .
T h e t e r n a r y p h a s e e q u i l i b r i a (fig. 47, p a r t i a l i s o t h e r m a l s e c t i o n for 0 - 3 3 a / o Sm at 800°C) a r e c h a r a c t e r i z e d b y the existence of t h r e e t e r n a r y c o m p o u n d s : SmRe4Si2, Sm2Re3Si 5 a n d " S m 4 R e S i s " ; the crystal s t r u c t u r e o f the l a t t e r is uncertain.
Sm 2 Re3Si5 is i s o t y p i c with the Sc 2 F e 3 S i s - t y p e o f structure, P 4 / m n c , a = 10.95(1), c = 5.599(5) ( B o d a k et al., 1978; X - r a y p o w d e r d i f f r a c t i o n of arc m e l t e d alloys; no d e t a i l e d c o n d i t i o n s for h e a t t r e a t m e n t were p r e s e n t e d ) . Segre (1981) c o n f i r m e d the s t r u c t u r e type, b u t o b s e r v e d slightly d i f f e r e n t l a t t i c e p a r a m e t e r s : a = 10.97(1) a n d c = 5.604(8). S a m p l e s w e r e arc m e l t e d ; T n = 1.2 K.
SmRe4Si 2 crystallizes w i t h the Z r F e 4 S i 2 - t y p e o f s t r u c t u r e : P 4 2 / m n m , a = 7.332(5) a n d c = 4.112(1) ( B o d a k et al., 1978; X - r a y p o w d e r d i f f r a c t i o n o f a r c - m e l t e d alloys).
References"
Bodak, O.1., V.K. Pecharskij and E.I. Gladyshevskij, 1978, lzv. Akad. Nauk SSSR, Neorg. Mater. 14(2), 250.
Pecharskij, V.K., 1979, Autoreferat Dis. Kand. Khim. (abstract of thesis, Russian) (Nauk, Lvov) 23 p.
Segre, C.U., 1981, Thes!s, Univ. of Calif., San Diego, USA.
S m - R h Si
F o u r t e r n a r y silicides have been r e p o r t e d for the S m - R h - S i system.
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 Ballestracci (1976), the c o m p o u n d S m R h 2 S i 2
194 P. ROGL
crystallizes with the ordered ThCr2Si2-type of structure: I 4 / m m m , a = 4.053 a n d c = 10.03. F o r sample p r e p a r a t i o n , see Y R h z S i 2. I n good a g r e e m e n t with this, F e l n e r a n d N o w i k (1983) reported a = 4.054(2) a n d c = 10.03(1) (X-ray p o w d e r analysis of i n d u c t i o n melted alloys); S m R h 2 S i 2 is a n t i f e r r o m a g n e t i c below T N = 46 K. T h e existence of a second peak in the susceptibility curve versus t e m p e r a t u r e at T m = 8(2) K was i n t e r p r e t e d as i t i n e r a n t electron o r d e r i n g of the R h sublattice.
S m R h 3 S i 2 is isotypic with the crystal s t r u c t u r e of CeCo3B2: P 6 / m m m , a = 5.510(6), c = 3.552(4) (Chevalier et al., 1981; X - r a y powder analysis). F o r s a m p l e p r e p a r a t i o n , see L a R h 3 S i 2. SmRh3Si 2 orders ferromagnetically at T m = 34 K. A t ,,para = 1.63/a B m o l e 1. T h e coercive 300 K the effective p a r a m a g n e t i c m o m e n t was ~eff
force at 4.2 K is H c = 14 kOe a n d the s a t u r a t i o n m a g n e t i z a t i o n is 0.15 /~B.
Chevalier et al. (1982) reported structure a n d m a g n e t o c h e m i c a l properties of the c o m p o u n d S m 2 R h 3 S i s crystallizing with the SczCo 3Si 5-type of structure. T h e space g r o u p is I b a m a n d lattice p a r a m e t e r s were given as a = 9.83(1), b = 11.75(1) a n d c = 5.772(5). M a g n e t i c susceptibilities i n the t e m p e r a t u r e range from 4.2 K to 300 K were characterized b y a V a n Vleck p a r a m a g n e t i s m of closely spaced multiplets. N o s u p e r c o n d u c t i v i t y has b e e n f o u n d above 2 K.
T h e existence of S m z R h S i 3 with a n A1Bz-derivative type of structure has b e e n reported b y Chevalier et al. (1982).
References
Ballestracci, R., 1976, C.R. Acad. Sci. Paris, Ser. B 282, 291.
Chevalier, B., A. Cole, P. Lejay and J. Etourneau, 1981, Mater. Res. Bull. 16, 1067.
Chevalier, B., P. Lejay, J. Etourneau, M. Vlasse and P. Hagenmuller, 1982, Paper presented at the 7th Intern. Conf. on Solid Compounds of Transition Elements, Grenoble, France, Collected Abstracts, I1 B 16, and 1982, Mater. Res. Bull. 17, 1211.
Felner, I. and I. Nowik, 1983, Solid State Commun. 47, 831.
Sm-Ru Si
T h e existence of a c o m p o u n d S m R u 3 S i 2 with the L a R u 3 S i 2 - t y p e of s t r u c t u r e was r e p o r t e d b y Barz (1980) from X-ray p o w d e r analysis. N o lattice p a r a m e t e r d a t a were given. F o r s a m p l e p r e p a r a t i o n a n d m e l t i n g b e h a v i o r (phase equilibria), see L a R u 3 Si 2.
M a g n e t i c o r d e r i n g was reported at 7~ > 25 K.
F r o m X-ray powder d a t a Ballestracci a n d Astier (1978) reported the c o m p o u n d S m R u 2 S i 2 to crystallize with the T h C r 2 S i 2 - t y p e of structure: I 4 / m m m , a = 4.178 a n d c = 9.71. Samples were p r e p a r e d b y i n d u c t i o n m e l t i n g u n d e r argon. H i e b l et al.
(1983) c o n f i r m e d the structure type, b u t from X - r a y p o w d e r d a t a reported slightly different u n i t cell d i m e n s i o n s : a = 4.1710(5) a n d c = 9.6601(59). F o r s a m p l e p r e p a r a - tion, see YOs2Si 2. T h e m a g n e t i c b e h a v i o r of S m R u 2 S i 2 - - i n v e s t i g a t e d i n the tem- p e r a t u r e r a n g e of 1.5 K to 1100 K - - i s characterized b y ~eff"Para = 0.54 /~B, 0p -- 14.4 K a n d a n t i f e r r o r n a g n e t i c o r d e r i n g at 7 K ( H i e b l et al., 1983).
References
Ballestracci, R. and G. Astier, 1978, C.R. Acad. Sci. Paris, Ser. B 286, 109.
Barz, H., 1980, Mater. Res. Bull. 15, 1489~
Hiebl, K., C. Horvath, P. Rogl and M.J. Sienko, 1983, J. Magn. Magn. Mater. 37, 287.
P H A S E E Q U I L I B R I A 195
T b - A ~ Si
N o ternary phase diagram exists for the system T b - A 1 Si. M u r a v y o v a et al.
(1972) and Y a n s o n (1975), however, reported the f o r m a t i o n of two ternary com- pounds.
TbA12Si2 adopts the structure type L a 2 0 2 S [space group P 3 m l ; M u r a v y o v a et al.
(1972), f r o m X - r a y p o w d e r diffraction analysis]. F o r sample preparation and a t o m parameters, see S m - A 1 Si. The lattice parameters m e a s u r e d were a = 4.18 and c = 6.60 A.
Y a n s o n (1975) f r o m p o w d e r X-ray diffraction analysis, characterized the com- p o u n d TbA12.sSi0. 2 as isostructural with the N i 3 S n - t y p e ( P 6 3 / m m c , a = 6 . 2 4 2 , c = 4.593). F o r a t o m parameters, see Y - A I - S i .
References
Muravyova, A.A., O.S. Zarechnyuk and E.I. Gladyshevskij, 1972, Visn. L'vivsk. Univ. Ser. KJfim. 13, 14.
Yanson, T.I., 1975, Autoreferat Dis. Kand. Khim. (abstract of thesis, Russian) (Nauk, Lvov) 22 p.
Tb A u - S i
Felner (1975) reported the existence of T b A u 2 S i 2 with the ordered ThCr2Si 2-type of structure; the crystal data as derived f r o m an X - r a y p o w d e r analysis were:
I 4 / m m m , a = 4.230 a n d c = 10.16; sample p r e p a r a t i o n as for L a A u 2 S i 2. T b A u 2 S i 2 orders anti-ferromagnetically below T N = 14.8 K; the p a r a m a g n e t i c data w e r e ~£ePfaf ra
= 8.0/~B a n d 0p = - 14.8 K.
Reference
Felner, I., 19"75, J. Phys. Chem. Sol. 36, 1063.
T b - C o - Si
N o ternary phase d i a g r a m is available for the T b - C o Si system; so far five ternary c o m p o u n d s have been characterized.
By means of X - r a y p o w d e r analysis of arc-melted alloys B o d a k and Gladyshevskij (1969) alloys characterized the c o m p o u n d TbCo9Si 2 with the B a C d 11-type structure:
1 4 J a m d , a = 9.702(5), c = 6.268(10); a t o m ordering was similar to CeNi8.6Si 2.4- The crystal structure of TbCos.sSi2. 5 has been m o r e recently refined f r o m X - r a y p o w d e r data to be isostructural with the CeNis.6Siz4-type ( o c c u p a t i o n variant o f the B a C d l l - t y p e , I 4 1 / a m d , a = 9.689 a n d c = 6.293; Yarovets, 1978. N o reliability factor was reported b u t the atomic parameters as refined are listed below: T b in 4a) 0, 3 / 4 ; 1 / 8 ; C o in 32i) 0.1261(10), 0.0492(9), 0.1779(8); Si in 8d) 0, 0, 1 / 2 a n d a statistical o c c u p a t i o n of 2.4 Co + 1.6 Si in 4b) 0, 1 / 4 , 3 / 8 . Samples were p r e p a r e d b y arc melting u n d e r a r g o n and subsequent annealing in evacuated silica tubes at 800°C for 720 h.
T b C o S i was observed to adopt the TiNiSi-type structure: Pnma, a = 6.812, b = 4.178 a n d c = 7.216 (X-ray p o w d e r data by Yarovets, 1978). F o r sample prepara- tion and a t o m parameters, see YNiSi.