By using the millimeter-wave or a kind of microwaves with short wave length, fabrication of ceramics with uniform morphology and examples of low temperature rapid sintering have been reported. Since the sintering progresses from the interior even with the rapid temperature increasing, it has been found that pores do not easily remain in the interior even if pressure sintering is performed afterwards, and the thermal conductivity of the heat radiation substrate is improved. We also reported diffusion promotion of cations which seems to contribute to the short-time sintering. We found zirconia ceramics having a composition which is easy to process using its plastic deformation during millimeter-wave heating and has creep resistance at elevated temperature with conventional heating. We have found improvement of oxide ion conductivity under irradiation with millimeter-waves in various added zirconia, ceria and LaGaO₃ based ceramics and improvement of power generation properties of solid oxide fuel cells using these materials as an electrolyte. Improvement of mass transfer including diffusion was more pronounced in ion species with large millimetre-wave absorption, but it could not be explained by this alone, and comprehensively explained by non-thermal effect.