| 摘要 |
PROBLEM TO BE SOLVED: To obtain a dense ceramic sintered compact having no limitation in shapes and a few pores by making a constitution comprising a main phase substantially composed of a fluoride and a subsidiary phase substantially composed of a fluoride having a melting point lower than that of the fluoride of the main phase in which the subsidiary phase exists in the grain boundary of the main phase. SOLUTION: CaF2 and/or MgF2 is preferable as a fluoride constituting a main phase. LiF is preferable as a fluoride constituting a subsidiary phase. The ratio of the subsidiary phase is preferably 0.5-5 mol.% based on the whole sintered compact. A fluoride raw material to provide the subsidiary phase is added to a fluoride raw material to provide the main phase, molded and sintered under normal pressure to give the objective ceramic sintered compact. After the sintering under normal pressure, preferably the sintered compact is further sintered by hot isostatic pressure method to give a sintered compact having >=99% relative density. The sintering under normal pressure is preferably carried out at 500-800 deg.C. The sintering by the hot isostatic pressure method is preferably performed in an N2 or Ar atmosphere under >=1,000 kg/cm2 at 550-750 deg.C. |
