Phase equilibria in the palladium-rich part of the Pd–Au–Cu–Sn quaternary system

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.     

New mixed palladium—lead and palladium—tin tellurides of the NiAs type

New ternary mixed nickel arsenide-type palladium and platinum—Group 14 metal tellurides were searched for by the high-temperature ampoule synthesis combined with the X-ray powder diffraction analysis. As a result, new phases of the ternary Pd—Pb—Te and Pd—Sn—Te systems belonging to the NiAs structure type were synthesized. The crystal structure of the compound PdPb_0.304(5)Te_0.695(5) was determined by the Rietveld method (P6₃/mmc, a = 4.151(1) Å, c = 5.680(1) Å, Z = 2, R ₁ = 0.032, R _p = 0.075, wR _all = 0.025). It was shown that no ordering exists in the occupancy of the main-group atom site by lead and tellurium. In the Pd—Sn—Te system, a phase isostructural with the above-mentioned compound was found. In the latter phase, there is also no ordering in the occupancy of the main-group atom site. According to the electron diffraction data, a superstructure derived from the NiAs type exists in a narrow range of the compositions PdSn_0.3Te_0.7—PdSn_0.4Te_0.6.     

Phases of the NiAs family in Cu-Pd-Sn and Au-Pd-Sn systems

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 %.     

Eine σ-Phase im System Chrom—Molybdän—Silicium

A ternary σ-phase (Cr_0.39–0.57Mo_0.47–0.29Si_0.14) has been detected in the chromium—molybdenum—silicon system at 1500 °C. The novel σ-phase, which displays only a small degree of ordering, undergoes eutectoid decomposition at ca. 1200 °C, into (Cr, Mo)+(Cr,Mo)₃Si. The relative stability bility of the ternary σ-phase and the non-existing binary σ-phases (Cr?Si, Mo?Si) were estimated from the observed equilibria. With respect to the coexistent phases there is an amount of 2500 cal/g atom metal necessary for stabilizing of the ternary σ-phases at 1500 °C. The slight deviation from completely random distribution reflects on the entropy change and there is fair agreement with the entropy change calculated from the temperature dependency of ΔG _{z, σ}.     

Phase transition temperatures of Sn–Zn–Al system and their comparison with calculated phase diagrams

The Sn?CZn?CAl system was studied in connection with the possible substitution of lead-based solders for temperatures up to 350?°C. Ternary alloys with up to 3?wt% of aluminium were prepared. The investigated alloys lie close to the monovariant line (eutectic valley) of the Sn?CZn?CAl system. The temperatures of phase transitions of six binary Sn?CZn reference alloys and fourteen ternary Sn?CZn?CAl alloys using DTA method were investigated in this paper. DTA experiments were performed at the heating/cooling rate of?4?°C?min^?1 using Setaram SETSYS 18_TM experimental equipment. The temperatures of phase transitions in the ternary Sn?CZn?CAl system were obtained, namely, the temperature of ternary eutectic reaction T _E1 (197.7?±?0.7?°C), temperature of ternary transition reaction T _U1 (278.6?±?0.7?°C), temperatures of liquidus and other transition temperatures for studied alloys. Temperatures obtained during DTA heating runs were used as authoritative. DTA curves obtained during cooling enabled realising better differentiation of the obtained overlapped heat effects (peaks) during heating. Theoretical isopleths of the Sn?CZn?CAl phase diagram were calculated using the Thermocalc software and MP0602 thermodynamic database. Experimental data were compared with the calculated temperatures, and a good agreement was obtained.     

Experimental Study and 3D Modeling of the Phase Diagram of the Ag–Sn–Se System

In connection with the contradictoriness of literature data, phase equilibria in the Ag–Sn–Se system were restudied by differential thermal analysis and X-ray powder diffraction analysis. A number of polythermal sections and the isothermal section at room temperature of the phase diagram were constructed, and a projection of the liquidus surface was built. The primary crystallization fields of phases and the types and coordinates of in- and monovariant equilibria were determined. It was demonstrated that, in the system, two ternary compounds, Ag₈SnSe₆ and Ag_xSn_{2 – x}Se₂ (0.84 < x < 1.06), form. The former melts congruently at 1015 K and undergoes a polymorphic transformation at 355 K, and the latter melts with decomposition by a peritectic reaction at 860 K. The formation of the compound Ag₂SnSe₃, which was previously reported in the literature, was not confirmed. Based on the phase diagrams of boundary binary systems and the results of the differential thermal analysis of a limited number of samples of the ternary system, equations were obtained for calculation and 3D modeling of the liquidus and phase-separation surfaces.     

Phase Diagram of the System Tl<Subscript>2</Subscript>Te–Tl<Subscript>5</Subscript>Te<Subscript>3</Subscript>–Tl<Subscript>9</Subscript>GdTe<Subscript>6</Subscript>

The ternary system Tl–Gd–Te within the composition range Tl₂Te–T_l5Te₃–T_l9GdTe₆ was studied by a set of physicochemical analysis methods. Some internal polythermal sections and the isothermal section at 300 K of the phase diagram were built, projections of the liquidus and solidus surfaces were constructed, and the graphs of the concentration dependences of the parameters and microhardness were plotted. It was shown that much (more than 90%) of the area of the concentration triangle is occupied by the homogeneity region of solid solutions with the Tl₅Te₃ structure (δ-phase). Solid solutions based on Tl₂Te (α-phase) form within a narrow region. The regions of the α- and δ-phases are separated by two-phase region α + δ.     

Lattice parameters and melting behavior of the B2-phase in the ternary gold-cadmium-zinc system

Lattice parameter and DTA-measurements were performed in the range of the ternary B 2-phase in the gold-cadmium-zinc system. It could be shown that a continuous range of homogeneity exists between β′-AuCd and β′-AuZn. Lattice parameter values are reported for a number of compositions. The ternary liquidus projection is given between about 40 and 60 at % Au. The congruent melting point of the binary β′-AuZn phase was found to be at 51.5±0.5 at % Au and 758±3°C.     

The excess enthalpies of liquid GaGeTe and GaSnTe alloys

The excess enthalpies of the liquid alloys GaGeTe and GaSnTe were measured in a heat-flow calorimeter at 1203 K. The enthalpy surface in the ternary space in both systems is characterized by a valley stretching from the exothermic minimum in the GaTe system to the minima of the GeTe and SnTe systems. The minima in the ternary systems were found in this valley, i.e. on the sections Ga₂Te₃-GeTe and Ga₂Te₃-SnTe. A comparison of the experimental data with those calculated from the excess enthalpies of the constituent binaries with the aid of the Bonnier model, reveals only small deviations. A preliminary investigation was made into the ternary phase diagram of GaSnTe. This system contains the two quasibinary sections Ga₂Te₃-SnTe, GaTe-SnTe and the ternary compound Ga₆SnTe₁₀. The previously reported compounds Ga₂SnTe₃ and GaSnTe₂ do not exist.     

Tree of phases of the Li,Na,Ba‖F,Br quaternary reciprocal system and study of the LiF-NaBr-BaFBr stable triangle

The Li,Ba‖F,Br ternary reciprocal system was investigated by differential thermal analysis. The T-x diagrams of the polythermal sections studied and the liquidus of the system were constructed. It was deter-mined that the system is of the adiagonal section type with a subordinate diagonal (according to Bergman’s classification). The characteristics and enthalpies of melting of the alloys corresponding to invariant equilibrium points were found. The Li,Na,Ba‖F,Br quaternary reciprocal system was partitioned, and the tree of phases was constructed. The LiF-NaBr-D₁(BaFBr) stable triangle was experimentally studied, the liquidus was constructed, and the characteristics of the alloy corresponding to a ternary eutectic were determined.     

Cu-Zn-Sn体系富Sn区液相限的研究

近些年来,无铅低熔点填料日渐引起人们的兴趣,且将得到广泛的应用。Cu-Zn-Sn合金正是无铅低熔点填料的一种基本合金。该体系相图虽有一些报道,但他们的研究只涉及富铜区(>50Wt％)的液相限和等温截面(500℃)。我们颇感兴趣的富Sn区的液相限,尚未见文献报道,因此测定该体系富Sn区的液相限是必要的。关于Cu-Zn-Sn体系的三个相关二元体系,已有文献报道,也较成熟。对于Cu-Zn体系,富Zn区600℃以下存在两个转熔反应,其转熔点分别为Q(～88Wt％Zn,598℃),W(97.5-98.5Wt％Zn,424℃);Cu-Sn体系富Sn区有一个转熔反应,其转熔点     

Study and 3D modeling of the phase diagram of the Ag–Ge–Se system

In view of the contradictoriness of the literature data, phase equilibria in the Ag–Ge–Se system were restudied by differential thermal analysis and X-ray powder diffraction analysis. A number of polythermal sections and an isothermal section at room temperature of the phase diagram were constructed, and so was the projection of the liquidus surface. The primary crystallization fields of phases and the types and coordinates of in- and monovariant equilibria were determined. It was shown that, in the system, a single ternary compound, Ag₈GeSe₆, forms, which undergoes congruent melting at 1175 K and a polymorphic transformation at 321 K. The formation of the compounds Ag₂GeSe₃ and Ag₈GeSe₅, which was previously reported in the literature, was not confirmed. Based on the phase diagrams of boundary binary systems and the results of the differential thermal analysis of a number of samples of the ternary system, equations were obtained for calculation and 3D modeling of the liquidus and phase-separation surfaces.     

Influence of the thermal treatment conditions and composition of bimetallic catalysts Fe—Pd/SiO2 on the catalytic properties in phenylacetylene hydrogenation

The supported bimetallic Fe—Pd/SiO₂ catalysts with the different Fe (0.025—8 mass.%) and Pd (0.05—3.2 mass.%) loadings were synthesized by the incipient wetness impregnation of support. The samples were heat-treated under different conditions (calcination in air at 240—350 °C or reduction in an H₂ flow at 400 °C). The X-ray phase analysis revealed the formation of Pd⁰, α-Fe₂O₃ and Fe₃O₄ phases after calcination of the samples at 240—260 °C. The reduction of the calcined Fe—Pd samples in an H₂ flow at 400 °C enables the formation of Fe⁰ nanoparticles of size 17—20 nm. The synthesized catalytic systems were studied in the selective hydrogenation of phenylacetylene at room temperature and atmospheric pressure in a solvent (ethanol, propanol). The catalytic properties of the Fe—Pd catalysts depend on the nature of solvent, catalyst composition, and thermal treatment conditions. The application of the Fe—Pd bimetallic catalysts with a low Pd loading of 0.05—0.1 mass.% made it possible to reach the high activity and selectivity to styrene (91%) at the complete conversion of phenylacetylene.     

Discovery and Optimization of Heterogeneous Catalysts by Using Combinatorial Chemistry

A novel ceramic array microreactor system has been designed and, in conjunction with resonance-enhanced multiphoton ionization (REMPI), used for the discovery of an optimum ternary catalyst composition for the dehydrogenation of cyclohexane to benzene. The catalyst library consisted of 66 ternary combinations of Pt, Pd, and In loaded on γ-Al₂O₃ pellets. The optimum catalyst for the production of benzene had the composition 0.8 % Pt, 0.1 % Pd, and 0.1 % In (see diagram). The preparation and screening of the library of 66 catalysts took about 2.5 days to complete—with conventional methods this would have taken several months!     

Kinetics of α-olefin metathesis on binary and ternary catalytic systems based on MoCl<Subscript>5</Subscript>/SiO<Subscript>2</Subscript>: Determination of the number of active centers and the mechanisms of their formation,deactivation, and reactivation

The kinetics of α-olefin metathesis in the presence of binary (MoCl₅/SiO₂-Me₄Sn) and ternary catalytic systems (MoCl₅/SiO₂-Me₄Sn-ECl₄, E = Si or Ge) was studied. It was found that reactivation in the course of metathesis occurred on the addition of a third component (silicon tetrachloride or germanium tetrachloride in combination with tetramethyltin) to a partially deactivated catalyst. The number of active centers was determined (5–6% of the amount of Mo), and the mechanisms of formation, deactivation, and reactivation were proposed for the binary and ternary catalytic systems. The roles of the individual components of the catalytic systems were revealed.     

Lattice parameters,magnetic properties,and melting behavior of the ternary NiAs-phase in the Ni-Sb-Te system

Lattice parameter, magnetic, and DTA-measurements were performed in the range of the ternary NiAs-phase in the nickel-antimony-tellurium system which exhibits a continuous range of homogeneity. Lattice parameter and susceptibility values are reported for three sections with constant ratios ofx _Sb/x _Te=4.00, 1.00, and 0.25. The ternary liquidus projection is given between about 35 and 60 at % Ni.Dedicated to Prof.K. L. Komarek on the occasion of his 60th birthday.     

Thermodynamic assessment of the Ag-Au-Bi and Ag-Au-Sb systems

The aim of the action of COST 531 taking into account the eleven elements Ag,Au,Bi,Cu,In,Pb,Sb,Sn,Zr (solder), Ni and Pd (substrate) is the database assessment for candidates of lead free soldering process. We studied four of them forming the ternary systems Ag-Au-Bi and Ag-Au-Sb. First we determined experimentally their phase diagrams, then the integral enthalpy of mixing of the liquid phase along different sections at different temperatures by using a SETARAM device heat flow calorimeter of Tian-Calvet type. All these data were used to optimize the thermodynamic parameters of the different phases of both ternary systems.     

Tm2.22Co6Sn20 and TmLi2Co6Sn20 stannides as disordered derivatives of the Cr23C6 structure type

A new ternary dithulium hexacobalt icosastannide, Tm_2.22Co₆Sn₂₀, and a new quaternary thulium dilithium hexacobalt icosastannide, TmLi₂Co₆Sn₂₀, crystallize as disordered variants of the binary cubic Cr₂₃C₆ structure type (cF116). 48 Sn atoms occupy sites of m.m2 symmetry, 32 Sn atoms sites of .3m symmetry, 24 Co atoms sites of 4m.m symmetry, eight Li (or Tm in the case of the ternary phase) atoms sites of symmetry and four Tm atoms sites of symmetry. The environment of one Tm atom is an 18‐vertex polyhedron and that of the second Tm (or Li) atom is a 16‐vertex polyhedron. Tetragonal antiprismatic coordination is observed for the Co atoms. Two Sn atoms are enclosed in a heavily deformed bicapped hexagonal prism and a monocapped hexagonal prism, respectively, and the environment of the third Sn atom is a 12‐vertex polyhedron. The electronic structures of both title compounds were calculated using the tight‐binding linear muffin‐tin orbital method in the atomic spheres approximation (TB–LMTO–ASA). Metallic bonding is dominant in these compounds, but the presence of Sn—Sn covalent dumbbells is also observed.     

A DFT investigation of the interactions of Pd,Ag, Sn,and Cs with silicon carbide

With a view to understand the diffusion of radionuclides through the silicon carbide layers in tristructural isotropic coated fuel particles, density functional theory calculations are applied to assess the interaction of palladium, silver, tin, and caesium with silicon carbide. The silicon carbide molecule (Si₂C₂), crystalline cubic silicon carbide (β‐SiC), and the (120) ∑5 grain boundary of β‐SiC are investigated to elucidate the differences in the interactions of silicon carbide with these elements. The main stabilizing forces in the PdSi₂C₂ complex were found to be donor‐acceptor charge transfer (covalent) interactions, the Ag and Sn complexes involve significant contributions from both electrostatic and covalent interactions, while the Cs atom is bonded dominantly by electrostatic forces. For the unconstrained M? Si₂C₂ model, the following energetic ordering was obtained: Pd > Sn > Cs > Ag. The steric constraints in the bulk SiC and on the grain boundary change the order of binding energies to Pd > Ag > Sn > Cs in the interstitials and Pd > Sn > Ag > Cs in vacancies and at the grain boundary. By comparing the incorporation energies in the solid phases, it is possible to group these elements by similarities in the patterns of incorporation energies. Silver and palladium form a group with carbon, tin is grouped with silicon, and caesium is on its own. © 2014 European Commission. International Journal of Quantum Chemistry published by Wiley Periodicals, Inc.