Thermoelectric properties of p-type silicon carbide

The effects of p-type additives on the thermoelectric properties of SiC ceramics were studied. Porous SiC ceramics with 60-65% relative density were fabricated by sintering the pressed a-SiC powder compacts with additives (B, amorphous-B, B₄C, Al₄C₃ ) at 2,000-2,200°C for 3h in Ar atmosphere. The sintered bodies were analyzed by means of XRD and SEM. In the case of B and/or a-B additions, the lattice parameter measurements revealed incorporation of a certain amount of added B and/or a-B into the SiC lattice and little phase transformation occurred during sintering. On the other hand, in the case of Al₄C₃ addition, the phase transformation of 6H-SiC to 4H-SiC occurred during sintering. The electrical conductivity and the Seebeck coefficient were measured at 350-800°C in Ar atmosphere. The electrical conductivity was a little dependent on temperature. The average grain size, the amount of addition and phase composition had significant effects on the thermoelectric properties. It could be seen that the electrical conductivity and Seebeck coefficient of Al₄C₃-doped SiC was higher than those of B- and/or B₄C-doped SiC