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

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.