Effect of sintering atmosphere on the electrical properties of aluminum and boron-added porous silicon carbide ceramics

The effect of nitrogen sintering atmosphere on the electrical resistivity of porous silicon carbide (SiC) ceramics with aluminum or boron additives comparing with argon atmosphere was thoroughly discussed and a mechanism was proposed. With using alpha-SiC starting powder and choosing trace amount of additives, the porosity, microstructure and polytype composition of the porous SiC ceramics sintered under different atmosphere were not found drastically different. Therefore, the effect on electrical properties were able to be discussed straightforwardly in relation to the sintering atmosphere and the two additives. Large difference of electrical resistivity of porous SiC ceramics is found in between the two different sintering atmospheres, in which those with 0.34 mol % of aluminum addition is 106 higher when sintered under argon atmosphere than those under nitrogen atmosphere. The mechanism of nitrogen atmosphere that reduce the electrical resistivity is considered to result from the phenomenon of Auger recombination based on the result of Hall measurements and photoluminescence spectrums.