Enhanced thermoelectric performance in Bi0.5Sb1.5Te3/SiC composites prepared by low-temperature liquid phase sintering

Abstract

Amongst thermoelectrics, Bi₂Te₃ is special owing to its peak performance near room temperature, which enables it to be used for both energy harvesting and cooling. Despite extensive studies on this compound, Bi₂Te₃-based bulk materials are usually prepared by field-assisted sintering and hot pressing. This necessitates sophisticated equipment and tedious compositional control, both of which are undesirable for large scale applications. In this work, a low-temperature liquid phase sintering (LPS) method was employed to prepare p-type Bi_0.5Sb_1.5Te₃/SiC composites with enhanced thermoelectric properties. In addition, a nearly two-fold increase in the power factor was observed post heat treatment at 350 °C. This can be ascribed to carrier concentration modulation due to porosity induced by heat treatment. Further addition of 0.6 vol% SiC results in a low lattice thermal conductivity of 0.33 W m⁻¹ K⁻¹, which can be ascribed to phonon scattering due to various defects induced by the SiC inclusion. Ultimately, a figure of merit ZT of 1.05 at 340 K was achieved for Bi_0.5Sb_1.5Te₃/0.6 vol% SiC, 20% higher than that of the pristine sample. Moreover, an average ZT of 0.87 at 300–500 K was attained, comparable to state-of-the-art values via high-temperature processing. This work showcases the promising application of the low-temperature LPS technique for energy-efficient processing of thermoelectrics.