Experimental investigation and thermodynamic modeling of the Se–Sn–Te system

Highlights: • Vertical section at SnSe–Te joint was investigated by DTA, XRD and SEM–EDS. • The saddle point at 703 K in the monovariant liq → αSnSe + hex(Te) was confirmed. • The Se–Sn–Te system was optimized using the CALPHAD technique. - Abstract: Vertical section at the SnSe–Te joint in the Se–Sn–Te system was investigated using X-ray powder diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectrometer (EDS) and differential thermal analysis (DTA). Combined with the present experimental results and experimental information of vertical sections, isothermal sections and liquidus projection in literature, the phase diagram and the thermodynamic property of the Se–Sn–Te system were modeled using the CALPHAD (CALculation of PHAse Diagrams) technique. The liquid was described as (Se, Sn, Te, SnSe, SnTe) through an associate model. The terminal solid solution phases of Se and Te were treated as hex (Se, Te), and Sn as bct (Sn). The intermetallic compounds, α/βSnSe and SnSe₂, were treated as (Sn, Te)_0.5(Se, Te)_0.5 and (Sn, Te)_0.3333(Se, Te)_0.6667, respectively, on the basis of the thermodynamic model in the Se–Sn binary system in literature and experimental solid solubility of Te in these compounds in Se–Sn–Te system. The compound SnTe was modeled as (Sn, Se)_0.5(Se, Te)_0.5 according to thermodynamic model in the binary Se–Te system and experimental solid solubility of Se in the Se–Sn–Te system. A set of self-consistent thermodynamic parameters of individual phases was obtained