Change in Mechanical Properties of Oxide Ceramics by Heat Treatment under Vacuum Condition

摘要

Alumina and Y_2O_3-partially stabilized zirconia (PSZ) which were typical oxide ceramics were heat-treated in vacuum in holding time of 3h and the temperatures between 1300 deg C and 1600 deg C. All test pieces showed mass loss by the heat-treatment. The amount of mass loss of the alumina was more abounding than that of the Y_2O_3-PSZ. Though the mass loss seemed to he due to vaporization from the sample surface, vapor species did not be identified. Bending strength of alumina and Y_2O_3-PSZ did not show the remarkable change by heat-treatment up to 1500 deg C, hut decreased suddenly at 1600 deg C. It is considered that one of the factors of strength degradation is the grain growth by heat-treatment. In case of the alumina, Vickers hardness showed the decrease of about 10 percent up to 1500 deg C and the decrease of about 30 percent at 1600 deg C. In case of the Y_2O_3-PSZ, Vickers hardness showed the decrease of about 10 percent in all tested temperature range. The degree of degradation of measured physical property of the Y_2O_3-PSZ was smaller than that of the alumina. The Y_2O_3-PSZ was more stable than the alumina for heat treatment.