Abstract
High grade Amakusa pottery clays mixed with 10, 20 and 30wt% zirconia were fired at 1250°, 1300° and 1350°C. Zircon, quartz, mullite, monoclinic- and tetragonal-zirconia were identified in the porcelain bodies with 20 and 30wt% zirconia fired at 1350°C. The content of the tetragonal phase in the fired bodies increased with increasing zirconia and with increasing firing temperature. The bending strength and fracture toughness of porcelain bodies containing zirconia increased with increasing firing temperature and with increasing amount of tetragonal zirconia, and those with 30wt% zirconia fired at 1350°C were 1.5 times higher than those without zirconia.
