4Preparation of BC-B System Composites adding PSS and their Thermoelectric Properties

Abstract

Boron carbide is very hard, refractory solids (m.p.>2400 °C) and its thermoelectric properties are unconventional in high temperature range above 700 °C; that is, low electric resistivity, high Seebeck coefficient, and low thermal conductivity. So it is useful material as a p-type semiconductor applied for thermoelectric power conversion at high temperature. Nuclear properties such as high cross-section and resistance to irradiation are also grateful for neutron absorption (10B). These are attractive especially for radioisotope fueled thermoelectric generator in space. Nonetheless, boron carbide does solemnly not utilize as thermoelectric devices except for thermocouple of B4C/C. Boron carbide is easily oxidized in air above 500° C, and react with rare metal such as Pt and Pd, which is used as an electrode. B4C-B quasi-binary composites were prepared at 1950 °, 2100 ° and 2250 °C by pressureless sintering in argon atmosphere using commercially manufactured B4C and amorphous B powders adding 0.5 wt.% polysilastyrene (PSS). As B9Cpossesses higher thermoelectric property as p-type semiconductors applied at high temperature, in this study we focused upon the lattice constant, density, electric resistivity, thermal conductivity, and Seebeck coefficient. These values as a function of carbon concentration added on preparation over range 7∼20 at.% at room temperature are addressed. Also figure of merit (Z) of specimens are calculated.