Electrical Resistivity Control of Non-oxide Ceramics by Grain Boundary Phases

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Although AlN ceramics is intrinsically an insulator, the electrically conductive AlN ceramics has been expected as machine parts in semiconductor manufacturing equipments. Our research group has reported it is possible to render AlN ceramics electrically conductive without losing their intrinsic high thermal conductivity by precipitating a rare-earth oxycarbide grain boundary phase of below 2 vol.%. However, the fracture strength of conductive AlN remarkably decreased because of grain growth of AlN by high temperature heat treatment for production of rare-earth oxycarbide grain boundary phase. In order to inhibit considerable grain growth by decreasing sintering temperature, the compositions of sintering additives were discussed. The improvement of fracture strength of electrically conductive AlN was attained by addition of Y_2O_3-CeO_2 composite additive, which is possible to inhibit grain growth of AlN by densification at lower sintering temperature. Additionally, the control of electrical conductivity of SiC as well as AlN was studied by formation of insulating grain boundary phase. The resistivity of SiC was successfully enhanced to 10^<12> from 10^3 Ωcm by precipitating insulating grain boundary phase at two facial boundaries