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.

CALPHAD modelling of the Ag–Pd–Sn ternary system has been performed. The disordered phases, the melt and the fcc phase were described using the substitutional solution model. Sublattice models were used to describe intermetallic compounds and the ternary phase. The two-sublattice model (Ag,Pd) 4 (Ag, Sn) used for the ternary phase made it possible to reproduce the inclination of its homogeneity range. The results of the thermodynamic calculation of the Ag–Pd–Sn system are in good agreement with the experimental data on phase equilibria and enthalpies of formation of the liquid. The agreement with the data on the partial Gibbs energy of tin in the liquid is somewhat worse.

Phase equilibria in Ag–In–Pd ternary system were studied using Scanning electron microscopy, Energy-dispersive X-ray spectroscopy (EDX) and X-Ray diffraction method (XRD). The solubilities of the third components in Ag–In and In–Pd binary phases were established, as well as composition ranges (from 4 to 17.5 at % Ag at 25 at % In) and crystal structure of τ ternary compound (Al 3 Ti). New thermodynamic assessment of Ag–In–Pd ternary system was performed, basing on the published experimental data and those obtained in the present work. Good agreement was achieved between the calculation results and the experimental data on phase equilibria and thermodynamic properties of the phases. The results of the calculation reproduce well experimental DTA/DSC data of three samples (the data were not included into the optimization). This additionally supports the correctness of the obtained thermodynamic description.

Solidus and liquidus temperatures of solid solutions with the face centered cubic lattice (α-phase) in Pd—Au—Sn and Pd—Cu—Sn ternary systems were determined. The liquidus surface projections for the α-phase were constructed, and position of the binary eutectic reaction L → α + Pd3Sn in the studied ternary systems was predicted.

The solubility of tin in the phases of Pd–Au–Sn and Pd–Cu–Sn ternary systems and a Pd–Au–Cu–Sn quaternary system with a fixed Pd: Au: Cu ratio of 11.1: 1: 4.6 is studied via microstructural, X-ray diffraction, and energy dispersive analysis. It is found that a quaternary alloy in equilibrium with a solid solution based on Pd, Au, and Sn contains a τ1 compound with structure which is derivative of the In type. It contains ~15 at % Sn and is a solid solution of the same compounds identified earlier in Pd–Au–Sn and Pd–Cu–Sn ternary systems. In addition, a quaternary alloy with a content of 20 at % Sn also contains a τ2 compound with the Pd2CuSn own type and can barely dissolve gold. The obtained data are used to construct a three-dimensional model of the Pd-rich part of the isothermal tetrahedron of the Pd–Au–Cu–Sn system and diagrams of the tin solubility isolines in palladium-rich alloys of the quaternary system at 500°С.

Phases with with a NiAs-based structure have been studied in Au-Pd-Sn and Cu-Pd-Sn systems at 500°C using powder X-ray diffraction, X-ray structure analysis, and energy-dispersive X-ray microanalysis. In the Cu-Pd-Sn system, binary phases γ-Pd2Sn and Cu6Sn5 both having the Ni2In structure form a phase region (Pd,Cu)2 − x Sn, which preserves the Ni2In structure and is confined at 500°C by an L + (Pd,Cu)2 − x Sn + ɛ-Cu3Sn three-phase region. In the Au-Pd-Sn system, the δ-AuSn phase with the NiAs structure and γ-Pd2Sn with the Ni2In structure form a single phase region (Pd,Au)2 − x Sn, which is bounded at 500°C by an L + (Pd,Au)2 − x Sn two-phase region; the structure of the ternary phase changes from Ni2In with incompletely filled trigonal-prismatic interstices to NiAs. The Pd20Sn13 phase, which crystallizes in the GaGe2Ni4 type structure, penetrates into both ternary systems up to ∼5 at % of the third component. The solubilities of copper and gold in PdSn and Pd2Sn phases, which have structures based on orthorhombically distorted NiAs and Ni2In lattices, respectively, do not exceed 2 at %.

Alloys of a Au-Pd-Sn system containing up to 35 at % Sn were investigated using a complex of physico-chemical methods of analysis. Partial isothermal sections were drawn at 500 and 800°C. The ternary phase having a tetragonal structure has been established. The solid solubility of gold in Pd-Sn phases goes up with the temperature increase. In all these phases gold seems to replace not only palladium, but also tin.