Isothermal phase relations in the Au-Sb-Te system at 350 C

Abstract

Isothermal phase relations in the Au-Sb-Te system have been investigated at 350°C by the reactions of pure elements of Au, Sb and Te in evacuated sealed glass tubes. Microprobe techniques were employed to determine the composition of each phase of the products. Most efforts were concentrated on the pseudo-binary join between AuSb2, aurostibite and AuTe2, calaverite and the phase relations between these phases and phases in the Sb and Te binary system. Two ternary phases whose compositions are Au1.9(Te2.645b0.46)3.1 and AuSbTe(phase A) were found to exist stably at 350 °C. The XRD pattern of the former phase is almost similar to that of montbrayite reported by BACHECHI (1972), but the composition of the former phase does not agree well with that, and the latter phase does not seem to have been reported as a distinct phase. Montbrayite shows some little solid solution field and has non-stoichiometric compositions. The composition of montbrayite in the present study is not located on the (Au,Sb)2Te3 stoichiometric line, but near the Au2(Te,Sb)3 line. Calaverite, AuTe2 dissolved AuSb2 components up to 11.8 mole per cent and aurostibite, AuSb2 dissolve less than 1 mole per cent AuTe2 component. The phase relations in the system were characterized by the tie line of tellerantimony, Sb2Te3 and gold, Au in the central portion of the diagram, by which independent two ternary systems were introduced, that is, the Au-Sb-Sb2Te3 and the Au-Sb2Te3-Te systems. As a result, right side phases in Figure 3, aurostibite(AuSb2), antimony(Sb) and δ phase ((Sb,Te) solid solutions,ss) in the former system do not coexist with left side phases, calaverite(AuTe2 ss), montbrayite, and tellurium(Te) in the latter system.