Phase diagrams of Bi–Sb–Se–Te system

Abstract

Bi–Sb–Se–Te is one of the most important material systems for thermoelectric applications. Phase diagrams of its constituent binary and ternary systems are reviewed and assessed. The Bi–Sb–Se–Te isothermal section tetrahedron at 400 °C and liquidus projection tetrahedron were proposed. Ternary compounds are only found in the Bi–Sb–Se system. There are eight three-phase regions at 400 °C and seven primary solidification phases in the Bi–Sb–Se system, including (Bi,Sb), (Bi2)m(Bi2Se3)n, Bi2Se3, Se, Sb2Se3, Bi3Sb5Se2, Bi3Sb12Se15. In the Bi–Sb–Te system, there are four three-phase regions at 400 °C. The (Bi,Sb)2Te3 and (Bi,Sb) are continuous solid solutions. There are six primary solidification phases, including (Bi,Sb)2Te3, (Te), γ, δ, (Bi,Sb), and (Bi2)m(Bi2Te3)n. In the Bi–Se–Te system, there is one three-phase region. (Bi2)m(Bi2Se3)n and (Bi2)m(Bi2Te3)n form a continuous solid solution phase at 400 °C. There are four primary solidification phases, including Bi, (Bi2)m(Bi2(Se,Te)3)n, Bi2(Se,Te)3 and (Se,Te). In the Sb–Se–Te system, there are five three-phase regions and six primary solidification phases, including (Sb), δ-(Sb2Te), γ-(SbTe), Sb2Te3, and (Se,Te). A wide range of (Bi,Sb)2(Se,Te)3 single-phase region was observed in the Bi–Sb–Se–Te quaternary system.