Vertical section of Au 2Y–Ag 2Y in Au–Ag–Y system

Abstract

A vertical section at 33.3 at.% Y in the Au–Ag–Y ternary system was studied using X-ray diffraction analysis, differential thermal analysis, and optical microscopy. An allotropic phase transformation of the Au 2Y phase in the Au–Y binary system is found. The Au 2Y phase transforms from a room temperature phase α to a high-temperature modification β at about 778 °C. The α-Au 2Y has a tetragonal MoSi 2-type structure with the lattice parameters a = 0.3692 nm, c = 0.8981 nm; the β-Au 2Y has an orthorhombic CeCu 2-type structure with the lattice parameters a = 0.4658 nm, b = 0.7340 nm, and c = 0.8200 nm. No allotropic phase transformation of the Ag 2Y phase in the Ag–Y binary system is found. The vertical section of the Au 2Y–Ag 2Y in the Au–Ag–Y ternary phase diagram established on the basis of these studies consists of seven phase regions: L (liquid phase region), α (MoSi 2-type structure), β (CeCu 2-type structure), α + β, α + L, β + L, and α + β + L.