Thermoelectric performance enhancement in n-type Bi2(TeSe)3 alloys owing to nanoscale inhomogeneity combined with a spark plasma-textured microstructure

Abstract

Bi2Te3 is a good thermoelectric compound that can be adjusted to p- or n-type with corresponding substitutions; however, less progress has been achieved for the property enhancement of n-type Bi2(TeSe)3 compared with p-type (BiSb)2Te3. Textured n-type Bi2(TeSe)3 with an enhanced thermoelectric performance has been developed in this study by combining texturing with in situ nanostructuring effects. The spark plasma-textured structure boosts the electrical transport properties and the power factors as benefits of the layered microstructure. It also leads to a simultaneous rise in the thermal conductivity along the a-axis. We developed a method to suppress increases in the thermal conductivity by inducing nanostructures, such as highly distorted regions and nanoscopic defect clusters, as well as dislocation loops that can form when texturing occurs at an optimized temperature. In this work, textured n-type Bi2(TeSe)3 materials having enhanced thermoelectric performances within a low temperature range are developed with a maximum dimensionless figure of merit (ZTmax) exceeding 1.1 at 473 K. The present method, which synergetically utilizes the texturing and nanostructuring effects, could also be applied to other thermoelectric compounds having layered structures.