PARTICLE-SIZE EFFECTS ON BENDING STRENGTH AND THERMOELECTRIC PROPERTIES OF P-TYPE BI-TE MATERIALS PREPARED BY HOT PRESS METHOD

The purpose of this paper is to present the relationship between mecha nical properties and thermoelectric properties of p-type Bi-Te polycry stalline materials. Semiconducting ceramics of p-type bismuth tellurid e were prepared by a hot press method. Their bending strength was over 40 MPa and decreased with increasing particle size. The Seebeck coeff icient and resistivity were dependent upon the particle size, those th ermoelectric properties decreased with increasing particle size. The r esults suggest that the carrier density varies with concentration of o xygen which adsorbed at the surface of the powders. Thermoelectric pro perties were nonisotropic. Especially, the resistivity was different f or the hot press directions. The ratio of the resistivity increased wi th increasing the particle diameter. The bending strength, Seebeck coe fficient and resistivity decreased nith increasing a hot press tempera ture. A sample with a bending strength of more than 50 MPa and a power factor of 10 x 10(-3) W/cm.K-2 was obtained by controlling the partic le size and the hot press temperature.