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)(2)Te-3 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)(2)Te-3, gamma, delta, 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. (C) The Minerals, Metals & Materials Society and ASM International 2013