Formation of Drop-Shaped Inclusions Based on Pt, Pd, Au, Ag, Bi, Sb, Te, and As under Crystallization of an Intermediate Solid Solution in the Cu–Fe–Ni–S System

Abstract

The phase and chemical composition of drop-shaped inclusions in a directionally crystallized solid solution was studied. The initial melt contained (mol %): Fe, 31.79; Cu, 15.94; Ni, 1.70; S, 50.20; Sn, 0.05; and As, 0.04, along with Pt, Pd, Rh, Ru, Ag, Au, Se, Te, Bi, and Sb each of 0.03. The results of experiments testify to the simultaneous separation of two types of liquids under cooling of the initial sulfide melt within the (Pd, Au, Ag)–(Bi, Sb, Te) and Cu–(S, Bi, Sb, Te) subsystems, respectively. The solidification of these liquids resulted in the appearance of inclusions subdivided by the authors into four classes. Class I was characterized by a eutectoid structure with the matrix of the Pd(Bi, Sb)_хTe_1 – х solid solution and Au crystallites with admixed Ag, Cu, and Pd. Class II was constituted of sulfosalts with Bi and Au inclusions. The inclusions of sperrylite Pt(As, S)₂ were ascribed to class III. Class IV was formed by composite inclusions consisting of fragments of classes I–III. The experiment described showed the more complicated behavior of noble metals and metalloid impurities under crystallization of compound sulfide–metalloid melts against the data of isothermal experiments described earlier.