Abstract
The stabilities of thermal expansion coefficient (13.5×10-6℃) and transparency of porcelain, which are main properties, have been investigated concerning in the formations of leucite and the change of leucite to sanidine by the heat-treatment (at 850℃) of the glass powder (SiO2 64.1, Al2O3 15.0, K2O 10.3, Na2O 8.5, MgO 0.3, CaO 1.2, B2O3 0.6 wt%). Detailed study show that: 1. After an induction period of about 10 hours under a metastable phase, the leucite in porcelain was changed to sanidine in a stable phase. 2. The thermal expansion coefficient and transparency of porcelain drastically decreased with an increase in the amount of sanidine changed from the leucite. 3. Porcelain prepared in the mixing method of 1wt% synthetic leucite crystal powder showed no change in the thermal expansion coefficient and transparency up to 4 hours at 850℃. This makes its stability improved 4 times as much as major commercial porcelains (in which sanidine is produced in 1 hour at 800 to 950℃).
