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.

Phase equilibria in the In–Pd–Sn system were investigated by a combination of key experiments and thermodynamic modeling. Partial isothermal sections at 500 °C and 800 °C of the In–Pd–Sn system for Pd contents above 66 at.% have been plotted experimentally using scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDX) and X-ray diffraction (XRD). The solubility of the third component in binary compounds InPd3 and Pd3Sn was determined. The new ternary compound τ1 was found in Pd contents ranging from 20 to 25 at.% and at Sn contents varying from 5 to approximately 17 at.% Sn. This compound crystallizes in an Al3Ti-type tetragonal structure. Isostructural InPd2 and Pd2Sn phases from the In–Pd and Pd–Sn binary compositions form a continuous phase field in the ternary system at both temperatures. The temperatures of the solidus, liquidus, and phase transitions of the alloys along the Pd–In50Sn50 line were measured using DTA/DSC. Thermodynamic calculation of the In–Pd–Sn ternary system is performed using the CALPHAD method using the Thermo-Calc® software. The thermodynamic properties of the disordered fcc and liquid phases were described by the Redlich–Kister–Muggianu model. To describe intermetallic phases, namely, InPd3, Pd3Sn, τ1 and Pd2(InxSn1−x), a two-sublattice models was used. Thermodynamic description of the In–Pd–Sn system obtained in this study is in good agreement both with our results and the published experimental data

Isothermal sections of the Ag-Pd-Sn system at 500 and 800 degrees C were plotted based on the XRD and EDX results. The solubility of Sn in palladium and silver-based fcc solid solution has nearly zero minimum around the Ag corner. The Pd3Sn and gamma-Pd2-xSn phases show significant dissolution of Ag and extend towards the Ag corner. The other Pd-Sn and Ag-Sn binary phases dissolve under 5 at.% of the third component. A new tau 1 ternary phase was discovered in the Pd-rich region. Its XRD pattern corresponds formally to In structure type, but the actual arrangement of the atoms in the tau 1 phase most probably corresponds to tetragonal Al3Ti type structure.

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.

Binodal curves for aqueous two-phase systems (ATPS) polyethylene glycol 1500 (PEG1500)-sodium sulfate-water with additions of sodium chloride and hydrochloric or sulfuric acids were determined by turbidimetric titration and analysis of coexisting phases. The results are compared with published data for the ATPS PEG1500-sodium sulfate-water without additions, and the influence of additions on the width of the two-phase field, tie-lines length, and slopes was traced. The influence of initial concentration of palladium, time of phase contact, pH, concentration of sodium chloride and sodium sulfate on the extraction of palladium(II) was studied. The coefficients of distribution of palladium(II) between the phases of ATPS were measured as a function of the concentrations of sodium chloride (0.1, 1.0, and 2.0 mol.L-1) and pH values. At lower concentrations of Cl- ions Pd(II) is extracted as a mixture of ions [Pd(H2O)Cl-3](-) and [PdCl4](2-), whereas the growth of C(Cl-) leads to prevalence of the latter, which has poorer extraction properties. Maximal values of the distribution coefficient D-P(d) of about 9.5 +/- 0.75 were achieved in the ATPS PEG1500-Na2SO4-0.1 M HCl and PEG1500-Na2SO4-(0.05 M H2SO4 + 0.1 M NaCl).

Phase equilibria of the Au-Cu-In system are investigated by combination of key experiments and thermodynamic modeling. Partial isothermal section at 500 degrees C of the Au-Cu-In system for In content up to 40 at.% have been plotted experimentally using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX) and X-ray diffraction (XRD). The solubilities of the foreign elements in the phases of binary systems are measured. No ternary compounds were found. The temperatures of solidus and/or liquidus of alpha, gamma and eta' phases were measured by DTA/DSC. Thermodynamic assessment of the Au-Cu-In ternary system is performed by CALPHAD method using Thermo-Calc (R) software. Thermodynamic properties of disordered fcc, liquid and zeta phases were described by Redlich-Kister-Muggianu model, though the Toop extrapolation was also tested. The description of the Au-In binary was modified to account for the change in stability parameters of fcc In, and for unifying the models of the gamma phase in Au-In and Cu-In edges. For the gamma, alpha, and eta' phases sublattice models were used. Good agreement with our experimental data for both calculated phase equilibria and non-equilibrium solidification curves was achieved.

New CALPHAD assessment of experimental data on phase equilibria and thermodynamic properties of phases in the Ag–Pd binary is performed. The results provide good description of experimental data, excepting one thermodynamic dataset which had to be excluded from calculation due to incompatibility. Results of optimization provides good description of data of phase equilibria, enthalpy of formation and activities of components obtained from 1906 to 2020 in whole range of concentrations and at temperatures from 560 to 1700 K. Differing from the results of published assessment, no artifacts (spurious miscibility gaps) were detected. The value of excess entropy for the composition Ag69.7Pd30.3 obtained from the heat capacity measured from 5 to about 560 K was not included to optimization but was used as independent test of results; the agreement seems to be well within experimental errors.

The partial isothermal section of the Pd-Cu-In system at 500 degrees C with 0-50 at. % In was plotted experimentally using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD). The addition of the third components significantly stabilizes binary compounds beta PdCu and eta' Cu2In. The solubility of copper in the InPd phase is close to 10 at.%. The phases InPd2, In3Pd5, and In3Pd2 do not dissolve any significant amount of copper. The new ternary compound InPd2Cu is found at about 25 at. % In from 3 to approx. 29 at. % Cu. This compound crystallizes in tetragonal structure of the VRh2Sn type. Its crystal structure, parameters of unit cell, as well as the distribution of atoms over crystallographic positions have been established by Rietveld method. (C) 2020 Elsevier B.V. All rights reserved.

The relative performance of the Muggianu and Toop methods of preliminary prediction of thermodynamic properties of solution phases is tested using Ag–Au–In ternary as a model system, which was recently studied by the present authors. The temperatures of solids, monovariant reaction (where appropriate) and liquids, as well as the heat of melting of solid solutions, were measured by DTA/DSC for five ternary samples. Different extrapolation models generate very different descriptions of phase equilibria. However, accounting for ternary interactions brings all the results into moderately close agreement. In both methods, the values of ternary parameters for liquid phase are more negative than for solid phases (about twice in modulo in Muggianu one and up to ten times in Toop case). This implies the stabilization of liquid in central concentration region. Neither predictive model captures this without accounting for ternary interactions.

Partial isothermal sections of the Au-In-Pd system at 500 and 800 degrees C for indium content less than 50 at.% have been plotted using electron microscopy, XRD and EDX methods. The boundaries of FCC solid solution in the system at these temperatures and the solubility of the third components in the compounds of the In-Pd and Au-In boundary binary systems have been determined. Three new ternary compounds tau(1), tau(2) and tau(3) have been found at 500 degrees C. The tau(1) compound has cubic Cu3Au-type structure, the tau(2) compound has tetragonal AuCu-type structure, and the tau(3) compound has hexagonal CaHg2-type structure. The unit cell parameters of the tau(2) and tau(3) phases have been refined by Rietveld method, and the distribution of atoms over crystallographic positions in their structures has been studied. At 800 degrees C, the tau(1) compound has wider homogeneity range for gold than that at 500 degrees C. The tau(2) compound at 800 degrees C exists in a narrow range, and the tau(3) phase is not stable at this temperature. (C) 2018 Elsevier B.V. All rights reserved.

A new Cu3Au-type ternary phase (τ phase) is found in the AuPd-rich part of the Au-In-Pd system. It has a broad homogeneity range based on extensive (Pd,Au) and (In,Au) replacement, with the composition varying between Au17.7In25.3Pd57.0 and Au50.8In16.2Pd33.0. The occupancies of the crystallographic positions were studied by single-crystal X-ray diffraction for three samples of different composition. The sites with m-3m symmetry are occupied by atoms with a smaller scattering power than the atoms located on 4/mmm sites. Two extreme structure models were refined. Within the first, the occupation type changes from (Au,In,Pd)3(Pd,In) to (Au,Pd)3(In,Pd,Au) with an increase in the Au gross content. For the second model, the occupation type (Au,In,Pd)3(Pd,Au) remains essentially unchanged for all Au concentrations. Although the diffraction data do not allow the choice of one of these models, the latter model, where Au substitutes In on 4/mmm sites, seems to be preferable, since it agrees with the fact that the homogeneity range of the τ phase is inclined to the Au corner and provides the same occupation type for all the studied samples of different compositions.

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.

Phase equilibria in Ag–Au–In system at 500°C are investigated by means of electron microscopy, electron probe microanalysis, and X-ray powder diffraction. The part of the system’s isothermal cross section with an indium content of up to 50 at % is constructed.

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