ИСТИНА

Alloys of Pd doped with coinage metals (CM — Cu, Ag and Au) and non-transitional low-melting metals (LMM — In, Sn a.o.) are used in divergent fields, including development of catalysts, jewelry and dentistry. Phase relations in the Pd and CM enriched areas of Pd-Cu-In, Pd-Au-In, Pd-Cu-Sn and Pd-Au-Sn systems were studied by the present authors [1-4]. The system Pd-Ag-Sn is presented to this Conference [5]. In all the systems the solubility of LMM in fcc Pd-CM solution is largely controlled by equilibria with the Pd3LMM compounds. Cu, Ag and Au are usually considered as analogs. Nevertheless, their influence on the structure and stability fields of the Pd3LMM compounds is quite different. The solubility of copper in both Pd3In and Pd3Sn is low (~1 to 2 at.%). Further addition of Cu causes formation of ternary phases Pd2CuIn (VRh2Sn type, ordered derivative of high-temperature modification of Pd3In) and Pd2CuSn (prototype structure). Gold exhibits large solubilities in both Pd3In and Pd3Sn; the homogeneity ranges are directed towards pure Au. The solution of Au in Pd3In has partially disordered CuAu type structure, and the solution of Au in Pd3Sn retains CmAu structure. Silver forms solid solutions in the two modifications of Pd3In phase with In content of about 25 at.%, but the pattern of its solubility in Pd3Sn phase is closer to the gold system. All the three tin-bearing systems form ternary т phases which have the fct structure of In type or, more probably, its ordered derivative. These phases can be considered as result of stabilization by CM of metastable phase known for Pd-Sn binary. [1] E. Ptashkina, E.Kabanova, K. Kalmykov, V.Kuznetsov, G. Zhmurko, J. Alloys Compd. 845, 156166 (2020). [2] E. Ptashkina, E. Kabanova, A. Yatsenko, V. Kuznetsov, G. Zhmurko, J. Alloys Compd. 776, 620 (2019). [3] M.A. Kareva, E.G. Kabanova, K.B. Kalmykov, G.P. Zhmurko, V.N. Kuznetsov, J. Phase EquilibriaDiffus. 35, 413 (2014). [4] M. Kareva, E. Kabanova, V. Kuznetsov, G. Zhmurko, S. Filippova, Moscow Univ. Chem. Bull., 66, 361 (2011). [5] A.Pavlenko, E.Ptashkina, E.Kabanova, and V.Kuznetsov, presented to SCTE-2021.