Structural Studies on NLS (SnSi)2s and Ni76 (SnBi)e6 Alloys
Ternary alloys on the quasi-binary system Ni,Si-Ni,Sn are found to contain two phases, viz., Ni,Sn(r) and Ni,Si(r) in equilibrium condition. It has been observed that these phases undergo transformations a t high temperatures but upto 500 "C room temperature modifications are stable. The two phases do not have any appreciable solid solubility in either of them. The phase Ni,Si(r) crystallizes in to Cu,Au (Ll,) structure where as Ni,Sn(r) is based on c.p.h. structure with a = 5.305 A", c = 4.254 A". No new ternary phase has been detected in Ni,Sn-Ni3Si section. The investigated alloys of the Ni-Sn-Bi system contain 75 at.% Ni. All the ternary alloys show simultaneous occurrence of three phases, namely Ni,Sn(r), NiBi and Ni(Sn) in equilibrium state. The phase NiBi has Ni As(B8) type of structure. Due to non-existence of isostructural phases in the two binary systems (Ni-Sn and Ni-Bi), single solid solution phases are not formed. Widely differing atomic sizes of nickel and bismuth atoms restrict the formation of solid solution of bismuth in nickel in contrast t o Ni(Sn) where atomic size factor is favourable.