Thermodynamic study of the Ag-Tl-Se system using the EMF method with AG4RbI5 as a solid electrolyte

Journal of Solid State Electrochemistry - The Ag-Tl-Se ternary system in the composition region Ag2Se-Tl2Se-Se was studied in the temperature range 300–450 K by measuring the electromotive...     

Thermodynamic Study of the Ag–Sb–Se System by the EMF Method with Ag4RbI5 Solid Electrolyte

Russian Journal of Electrochemistry - The results of studying the Ag–Sb–Se system by measuring the electromotive force (EMF) of concentration cells with the Ag4RbI5 solid electrolyte...     

Phase equilibria in the Cu–Cu<Subscript>2</Subscript>Se–As system

Phase equilibria in the Cu–Cu₂Se–As were investigated by differential thermal analysis and X-ray powder diffraction analysis. Informative plots describing this system were constructed, viz., the polythermal sections Cu_0.667Se_0.333–As, Cu_0.667Se_0.333–Cu_0.735As_0.265, and Cu_0.8Se_0.2–As, the isothermal section of the phase diagram at 300 K, and the projection of the liquidus surface. The obtained results differ from the published data in length of fields of primary crystallization of phases and in coordinates of a number of invariant equilibrium points.     

Thermodynamic study of Ag<Subscript>8</Subscript>GeSe<Subscript>6</Subscript> by EMF with an Ag<Subscript>4</Subscript>RbI<Subscript>5</Subscript> solid electrolyte

The Ag–Ge–Se system was studied in the range of compositions Ag₂Se–GeSe₂–Se by measuring the EMF of the concentration (relative to the silver electrode) circuits with a solid electrolyte Ag₄RbI₅ in the temperature range 290–430 K. The polymorphic transition temperature of Ag₈GeSe₆ (320 K) was determined and the partial molar functions of silver were calculated for both crystal modifications of this compound based on the EMF measurements. The thermodynamic functions of formation and entropy of both modifications of Ag₈GeSe₆ and the thermodynamic functions of its polymorphic transition were calculated.     

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 equilibria and thermodynamic properties of the system Tl-TlBr-Se

The system Tl-Se-Br was studied in the region Tl-TlBr-Se by DTA, X-ray powder diffraction, emf measurements, and microhardness measurements. Several vertical sections, the isothermal section at 400 K, and the liquidus-surface projection were constructed. The quasi-binary sections TlBr-Tl₂Se, TlBr-TlSe, Tl₅Se₂Br-Tl, and Tl₅Se₂Br-TlSe allow the system Tl-TlBr-Se to be triangulated into five subordinate triangles. Wide immiscibility regions were discovered in the system, including a three-phase region in subsystem Tl₂Br-Tl₂Se-Se. Homogeneity and primary separation regions were determined, as well as the types and coordinates of invariant and monovariant equilibria on the T-x-y-diagram. From the results of emf measurements, the standard thermodynamic functions of formation were calculated for the compound Tl₅Se₂Br.     

Phase equilibria in the Cu-Cu2S-As system

Phase equilibria in the Cu-Cu₂S-Assystem have been studied by DTA and X-ray powder diffraction. Cu_0.667S_0.333-As, Cu_0.667S_0.333-Cu_0.735As_0.265, and Cu_0.8S_0.2-As polythermal sections, an isothermal section at 300 K, and the liquidus projection have been constructed. Our data differ from reported data in the extents of primary crystallization phase fields and the coordinates of some invariant equilibrium points.     

Thermodynamic Study of the 2PbTe–AgSbTe<Subscript>2</Subscript> System Using EMF Technique with the Ag<Subscript>4</Subscript>RbI<Subscript>5</Subscript> Solid Electrolyte

The work presents the results of studies of the 2PbTe–AgSbTe₂ system using the EMF technique with the Ag₄RbI₅ solid electrolyte in the temperature range of 300–430 K. Formation of a wide (0–80 mol % AgSbTe₂) region of PbTe-based solid solutions in the system is shown. Partial thermodynamic functions \(\left( {\overline {\Delta G} ,\overline {\Delta H} ,\overline {\Delta S} } \right)\) of alloyed silver are calculated on the basis of the equations of the temperature dependences of EMF. Potential-forming reactions are determined on the basis of the data on solid-phase equilibriums in the Ag₂Te–PbTe–Sb₂Te₃–Te system that are used to calculate standard thermodynamic functions of formation and standard entropies of (2PbTe) _x (AgSbTe₂)_1–x (x = 0.2; 0.4; 0.6; 08; 0.9) solid solutions.     

Thermodynamic study of glasses in Ag-As-Se system using EMF method with Ag<Subscript>4</Subscript>RbI<Subscript>5</Subscript> solid electrolyte

The EMF method with Ag₄RbI₅ solid electrolyte was used to study silver solubility in Ag-As-Se glasses on the basis of the cross-sections of (I) Ag-As_0.25Se_0.75, (II) Ag-As_0.33Se_0.67, (III) Ag-As_0.4Se_0.6, and (IV) Ag-As_0.5Se_0.5. It is found that silver solubility reaches 30 and 40 at % in sections (I), (IV) and (II), (III), accordingly. The data of EMF measurements were used as a basis for calculation of partial polar functions of Ag in glasses. The Gibbs-Duhem equations were integrated to calculate thermodynamic functions of silver dissolution in vitreous As _x Se_{1 − x} (x = 0.25; 0.33; 0.4; 0.5), from which the corresponding data for the latter were used to obtain the standard integral thermodynamic functions of the mixing of glasses. The obtained results were compared with the thermodynamic data for crystalline silver selenoarsenites.