Thermoelectric Properties of Textured Materials Based on Bismuth Telluride with Nanograined and Micrograined Structures Prepared by Spark Plasma Sintering

Abstract

Textured samples of the Bi19Gd0.1Te3, which is a thermoelectric material characterized by the formation of a lamellar grain structure, were prepared using spark plasma sintering. Lamellar layers consist of grains elongated in the plane parallel to the direction of the application of pressure during sintering. The properties of the samples measured in the direction perpendicular to the application of pressure correspond to microgranular structures, and those in the perpendicular direction to nanograined structures, which gradually transfer into microgranular structures with increasing sintering temperature. With a decrease in the grain size, the electrical resistance gradually increases, and the total thermal conductivity decreases, and these tendencies are most clearly manifested in the transition from micrograined to nanograined structures. The observed size effects are due to the scattering of electrons and phonons at grain boundaries.