Thermoelectric properties of aluminum compound-doped α-SiC ceramics

The effects of aluminum compound additive on the thermoelectric properties of alpha-SiC ceramics were studied. Porous SiC ceramics with 50-60% relative density were fabricated by sintering the pressed alpha-SiC powder compacts with AlN and/or Al4C3 at 2150 degrees C for 3 h in Ar atmosphere. The sintered bodies were analyzed by means of XRD, SEM, and TEM. The lattice parameter measurements revealed incorporation of a certain amount of added Al and/or N into the SiC lattice. 6H to 4H reverse phase transformation occurred during sintering. The Seebeck coefficient, electrical conductivity and thermal conductivity were measured at 550-950 degrees C in Ar and/or vacuum atmosphere. The kind of additives and the amount of addition had significant effects on the thermoelectric properties. The thermoelectric figure of merit of aluminum compound-doped SiC increased with increasing temperature and was lower than that of n-type SiC. On the whole, AlN-doped SiC had higher figure of merit than Al4C3-doped SiC. (C) 2014 The Ceramic Society of Japan. All rights reserved.