Phase equilibria in the Tl–TlI–Te system and thermodynamic properties of the Tl5Te3−xIx solid solution

• The Tl–TlTe–I system is investigated.
• The fields of primary crystallization are determined.
• Homogeneity range for Tl5Te3−xIx solid solution is established.
• The partial molar thermodynamic functions of Tl in Tl5Te3−xIx are calculated.
• Standard integral thermodynamic functions of Tl5Te3−xIx are calculated.

The Tl–TlI–Te ternary system was investigated by using the DTA and XRD analyses, microhardness and EMF measurements, leading to the construction of important polythermal and isothermal sections as well as the projection of the liquidus surface. Determined were the fields of primary crystallization and the types and coordinates of non- and monovariant equilibria. The system features the formation of continuous solid solutions (δ-phase) between the Tl5Te3 and Tl5Te2I compounds. The homogeneity area of the δ-phase completely covers the Tl5Te2I–Tl5Te3–Tl2Te subsystem. The partial molar thermodynamic functions (ΔG‾,ΔH‾,ΔS‾) of thallium as well as the standard integral thermodynamic functions of the Tl5Te3−xIx solid solution (for various x) were calculated based on the results of the EMF measurements.