Development of new materials and their testing on in-situ electrical properties in neutron environment

The research and development of high performance ceramics related to nuclear energy have become important, especially for fusion reactors. The innovation and application of new nonmetallic inorganic materials are needed in nuclear energy field. There have been many works on Al2O3-base ceramics and their electrical properties. The dielectric property and electric conductivity of ceramics are important for the application to microwave sintering and the radio frequency heating of plasma in nuclear fusion. Silicon nitride is one of the materials for the electrical insulation in fusion reactors. In this paper, the development of Si3N4-base ceramics is summarized. It has been known that the high temperature strength, fracture mechanism, compression creep and oxidation resistance of hot pressed silicon nitride with magnesia are strongly affected by the intergranular phases composed of impurities and additives. The dielectric property and electrical conductivity of Si3N4-base ceramics without irradiation, the in situ test on the electrical conductivity under neutron irradiation, and the possibility of developing new materials by neutron irradiation are reported. (K.I.)