Crystal Structure of Intermetallics in Systems Pd–(Cu, Ag, Au)–(In, Sn)

Abstract

The crystal structure of the ternary intermetallic compounds τ₁ in the Pd–(Cu, Ag, Au)–Sn systems has been determined. It has been found that in the silver and gold systems, these compounds crystallize in a body-centered tetragonal cell with atomic ordering corresponding to the Al₃Ti structural type, whereas in the copper system, the τ₁ phase adopts the VRh₂Sn structure, which is an additionally ordered derivative of the Al₃Ti type. The available literature data and the authors’ findings on the structures of binary and ternary compounds, which are ordered derivatives of the Cu-type structure, in Pd systems with Group 11 elements and non-transition metals In and Sn have been summarized and analyzed. It is shown that these compounds form at specific values of the electron concentration (e/a): compounds with AuCu or Al₃Zr structural types at e/a = 0.75, with Al₃Ti or VRh₂Sn structural types at e/a = 0.8–1, and with the AuCu₃ structural type at e/a = 1. The size factor influences the direction and extent of the phase homogeneity regions.