1977 年 26 巻 288 号 p. 853-857
Recent developments in ceramic fabrication processes enable one to produce transparent and translucent polycrystalline ceramics. These ceramics are fully densified and have near zero porosity in order to eliminate the dispersion of light and internal reflection due to heterogeneities of their texture. This is achieved by sintering a well prepared raw material under carefully controlled atmosphere, temperature and time schedule.
In the present study, transparent alumina was prepared by a sol-gel method. The fabrication process comprises the four stages of precipitation of aluminum monohydroxide, formation of the sol, formation of the gel, and firing to alumina.
The thin plate of gel was formed by very slow dehydration of an aqueous sol at ambient pressure and temperature, and then it was heated in air to obtaine a transparent alumina. The resultant alumina was transparent up to 1000°C, above which it was opalized gradually with temperature accompanying the formation of α-alumina phase. The following sequence of transition was identified by the X-ray powder diffraction;