Phase equilibria in the Tl2Te-SnTe-Bi2Te3 system

phase equilibria in the Tl2Te-SnTe-Bi2Te3 system were studied by differential thermal analysis (DTA), X-ray powder diffraction, and microhardness measurements. Some polythermal sections and isothermal (at 600 and 800 K) sections of the phase diagram and a projection of the liquidus surface were constructed. It was shown that the system is characterized by the formation of solid solutions with the Tl5Te3 structure (delta) and solid solutions based on SnTe (gamma(1)), Tl2Te (alpha), Bi2Te3 (beta), and two TlBiTe2 (gamma(2) and gamma'(2)) phases. Their homogeneity regions were determined. The liquidus surface consists of the primary crystallization fields of the beta-, gamma(1)-, gamma'(2)-, and delta phases and the compounds SnBi2Te4 and SnBi4Te7. The liquidus of the alpha phase is degenerate. The primary crystallization fields of phases were determined, and the types and coordinates of in- and monovariant equilibria were found.