Intermetallic phases in the Ca-Cu-Sn system

Twelve ternary alloys in the Ca-Cu-Sn system were synthesized as a test on the existing phases. They were prepared from the elements sealed under argon in Ta crucibles, melted in an induction furnace and annealed at 700 °C or 600 °C. Four ordered compounds were found: CaCuSn (YbAuSn type), Imm2, a = 4.597(1)A ° , b = 22.027(2)A ° , c = 7.939(1)A ° , Z = 12, wR2 = 0.080,1683 F2 values; Ca3Cu8Sn4 (Nd3Co8Sn4 type), P63mc, a =9.125(1)A ° , c= 7.728(1)A ° , Z= 2, wR2= 0.087, 704 F2 values; CaCu2Sn2 (new structure type), C2/m, a = 10.943(3)A ° , b = 4.222(1)A ° , c = 4.834(1)A ° , β= 107.94(1)°, Z = 2, wR2 = 0.051, 343 F2 values; CaCu9Sn4 (LaFe9Si4 type), I4/mcm, a= 8.630(1)A ° ,c = 12.402(1)A ° , Z = 4, wR2 = 0.047, 566 F2 values. In all phases the shortest Cu-Sn distances are in the range 2.59-2.66A ° , while the shortest Cu-Cu distances are practically the same, 2.53-2.54A ° , except CaCuSn where no Cu-Cu contacts occur.