Understanding the interface-driven thermoelectric behaviour of Bi2Te3–Ga2Te3 alloys

Abstract

Thermoelectricity is one of the interesting solid-state energy conversion techniques for waste heat recovery. Bi₂Te₃ is a widely used thermoelectric material with a narrow bandgap and rhombohedral crystal structure. On the other hand, Ga₂Te₃ is another interesting phase with a wider bandgap and zinc-blend crystal structure that shows ultra-low thermal conductivity. In the present investigation, the multiphase alloys with varying fractions of these phases have been prepared to explore the possible energy filtering effect. Among the investigated alloys, an interesting high electrical conductivity and Seebeck coefficient was observed for the eutectic alloy, resulting in a thermoelectric Figure of merit (zT) of 0.54. On the other hand, a significant reduction of about 16 percent in total thermal conductivity at room temperature is observed due to the increased interfaces and Ga₂Te₃ phase. Moreover, the role of the interface in deciding the electronic transport is explained using the possible heterojunction between the Bi₂Te₃ and Ga₂Te₃ phases. This study examines the role of phase equilibria and interface engineering in designing new eutectics with improved thermoelectric performance.