Phase diagram of Bi–In–Se ternary system

Abstract

Bi–In–Se ternary system is of thermoelectric application interests and its phase diagrams are fundamentally important. Experimental measurements and Calphad-type thermodynamic modeling are carried out to determine the phase diagrams of the Bi–In–Se ternary system. Bi–In–Se ternary alloys are prepared. The equilibrium phases at 250 °C and their primary solidification phases are determined. No ternary compound is observed. The primary solidification phases are Bi2Se3, Se, In2Se3, In6Se7, InSe, In4Se3, In, ε, BiIn2, Bi3In5, BiIn, Bi, and (Bi2)m(Bi2Se3)n. In the Bi–In–Se isothermal section at 250 °C, there are seven tie-triangles which are Liquid+(Bi)+InSe, Liquid + In4Se3+InSe, (Bi)+Bi6Se7+InSe, (Bi)+In6Se7+In2Se3, (Bi)+(Bi2)m(Bi2Se3)n + In2Se3, Bi2Se3+(Bi2)m(Bi2Se3)n + In2Se3 and Liquid + In2Se3 +Bi2Se3. The temperatures of invariant reactions are determined by thermal analysis, and the reaction scheme is determined. Calphad-type thermodynamic modeling of the Bi–In–Se ternary system is carried out based on the thermodynamic models of the three binary constituent systems, and experimental results of isothermal sections and liquidus projection. The calculated and experimentally determined Bi–In–Se phase diagrams are in good agreement.