Liquidus projection of the ternary Bi-Sb-Te thermoelectric material system

The ternary Bi-Sb-Te system is important for thermoelectric applications. Its liquidus projection is determined, except for the Bi-rich corner with various unconfirmed binary Bi-Te compounds. Fifty Bi-Sb-Te ternary alloys are prepared. Primary solidification phases are identified using metallographic observations and X-ray diffraction techniques. Phase transformation temperatures are determined using differential thermal analysis. No ternary compound is found. (Bi,Sb)₂Te₃ and (Bi,Sb) are continuous solid solutions. The Bi₂Te₃ and Sb₂Te₃ phases form a pseudo-binary section. Alloys of the primary solidification phases of Te, (Bi,Sb)₂Te₃, γ, δ, and (Bi,Sb) are determined and the boundaries of various primary solidification phases are delineated. The Bi-Sb-Te liquidus projection is also calculated with the CALPHAD method using preliminary thermodynamic models, and the calculated results are qualitatively in agreement with the experimental determinations.