| 摘要 |
PURPOSE:To obtain a silicon nitride sintered compact improved in oxidation resistance at medium temperatures, excellent in durability, while retaining excellent high-temperature characteristics, by oxidation treatment with an inorganic acid of a silicon nitride sintered compact containing each specified range of a group IIIa element and excess oxygen. CONSTITUTION:A silicon nitride sintered compact comprising (A) 70-98mol% of silicon nitride, (B) 1.0-10mol%, on an oxide basis, of a group IIIa element and (C) <=25mol%, on a silica(SiO2) basis, of excess oxygen, with the molar ratio C/B of 0.7 to 3, is put to oxidation treatment with an inorganic acid, especifically, immersed for several minutes to several hours in a liquid such as hydrochloric, sulfuric, nitric or hydrofluoric acid, or coated with an acid solution. |
