Electrical resistivity of α-SiC ceramics sintered with Al2O3 or AlN additives

Highly resistive SiC ceramics were prepared by hot pressing α-SiC powders with Al2O3-Y2O3 additives with a 4:1 molar ratio. X-ray diffraction patterns, Raman spectra, electron probe microanalysis (EMPA), and scanning electron microscopy (SEM) images revealed that the bulk SiC ceramics consisted mostly of micron-sized 6H-SiC grains along with Y2O3 and Si clusters. As the additive content increased from 1 to 10 vol%, the electrical resistivity of the ceramics increased from 3.0 × 106 to 1.3 × 108 Ω cm at room temperature. Such high resistivity is ascribed to Al2O3 in which Al impurities substituting Si site act as deep acceptors for trapping carriers. More resistive α-SiC ceramics were produced by adding AlN instead of Al2O3. The highest resistivity (1.3 × 1010 Ω cm) was achieved by employing 3 vol% AlN-Y3Al5O12 (yttrium aluminum garnet, YAG) as an additive.