Particle-size effects on bending strength and thermoelectric properties of p-type Bi-Te materials prepared by hot press method

Abstract

The purpose of this paper is to present the relationship between mechanical properties and thermoelectric properties of p-type Bi-Te polycrystalline materials. Semiconducting ceramics of p-type bismuth telluride were prepared by a hot press method. Their bending strength was over 40 MPa and decreased with increasing particle size. The Seebeck coefficient and resistivity were dependent upon the particle size, those thermoelectric properties decreased with increasing particle size. The results suggest that the carrier density varies with concentration of oxygen which adsorbed at the surface of the powders. Thermoelectric properties were nonisotropic. Especially, the resistivity was different for the hot press directions. The ratio of the resistivity increased with increasing the particle diameter. The bending strength, Seebeck coefficient and resistivity decreased with increasing a hot press temperature. A sample with a bending strength of more than 50 MPa and a power factor of 40 x 10-3 W/cm·K2 was obtained by controlling the particle size and the hot press temperature.