Highly resistive SiC ceramics sintered with Al2O3-AlN-Y2O3 additions

A polycrystalline SiC ceramic prepared by pressureless sintering of α-SiC powders with 3 vol% Al2O3-AlN-Y2O3 additives in an argon atmosphere exhibited a high electrical resistivity of ~1013 Ω cm at room temperature. X-ray diffraction revealed that the SiC ceramics consisted mainly of 6H- and 4H-SiC polytypes. Scanning electron microscopy and high resolution transmission electron microscopy investigations showed that the SiC specimen contained micron-sized grains surrounded by an amorphous Al-Y-Si-O-C-N film with a thickness of ~4.85 nm. The thick boundary film between the grains contributed to the high resistivity of the SiC ceramic.