Phase equilibria in the Tl-TlCl-Te system and thermodynamic properties of the compound Tl5Te2Cl |
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Authors: | D. M. Babanly Z. S. Aliev F. Ya. Dhafarli M. B. Babanly |
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Affiliation: | 1.Baku State University,Baku,Azerbaijan |
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Abstract: | The Tl-Te-Cl system was studied in the Tl-TlCl-Te composition region by differential thermal analysis, X-ray powder diffraction, and emf and microhardness measurements. A series of polythermal sections, an isothermal section at 400 K, and a projection of the liquidus surface of the phase diagram were constructed. The ternary compound Tl5Te2Cl characterized by a wide homogeneity region and incongruent melting by a syntectic reaction at 708 K was shown to exist. This compound was found to crystallize in tetragonal lattice (space group I4/mcm) with the parameters a = 8.921 Å, c = 12.692 Å, Z = 4. Wide phase separation regions were also found in the system, including a three-phase separation region in the Tl-TlCl-Tl2Te subsystem. Regions of primary crystallization of phases, and the types and coordinates of in- and monovariant equilibria in the T-x-y diagram were determined. From emf measurement data, the standard thermodynamic functions of formation and the standard entropy were calculated for the compound Tl5Te2Cl, as follows: ?ΔG 298 0 = 355.9 ± 1.1 kJ/mol, ?ΔH 298 0 = 377.1 ± 5.0 kJ/mol, and S 298 0 = 474.1 ± 6.8 J/(mol K). |
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