| 摘要 |
PURPOSE: To make ceramics excellent in light transmission and uniform in grain diameter and to improve the strength, hardness, durability and workability by using plural kinds of oxides and specifying the standard formation Gibbs' energy (ΔGf0 ) of them. CONSTITUTION: A ceramic compact is a composite in which the standard formation Gibbs' energy (ΔGf0 ) of plural kinds of oxides is negative, the absolute value is >1,581.9kJ/mol and one or more kinds of oxide particles other than Al2 O3 particles exist between Al2 O3 particlts. Each of the largest particles of Al2 O3 has <=30μm major axis size and <=20μm minor axis size and each of the existing oxide particles has <=20μm major axis size and <=5μm minor axis size. The ceramic compact consisting of high purity alumina powder and oxide particles added in the form of salts or oxides by 0.01-18wt.% to the alumina powder is primarily sintered by holding at 1,350-1,800 deg.C for >=0.5hr in vacuum, in the air or in an atmosphere of N2 Ar or H2 and the resultant sintered compact is subjected to hot isostatic pressing at a high temp. under a high pressure of gas to obtain the objective polycrystalline ceramics not contg. bubbles at all. |
