Control of Electrical Resistivity in Silicon Carbide Ceramics Sintered with Aluminum Nitride and Yttria

The electrical properties of beta-SiC ceramics were found to be adjustable through appropriate AlN-Y2O3 codoping. Polycrystalline beta-SiC specimens were obtained by hot pressing silicon carbide (SiC) powder mixtures containing AlN and Y2O3 as sintering additives in a nitrogen atmosphere. The electrical resistivity of the SiC specimens, which exhibited n-type character, increased with AlN doping and decreased with Y2O3 doping. The increase in resistivity is attributed to Al-derived acceptors trapping carriers excited from the N-derived donors. The results suggest that the electrical resistivity of the beta-SiC ceramics may be varied in the 10(4)-10(-3) Omega.cm range by manipulating the compensation of the two impurity states. The photoluminescence (PL) spectrum of the specimens was found to evolve with the addition of dopants. The presence of N-donor and Al-acceptor states within the band gap of 3C-SiC could be identified by analyzing the PL data.