Change in Mechanical Properties of Oxide Ceramics Due to Heat Treatment under Vacuum

摘要

Alumina and Y_2O_3-partially stabilized zirconia (PSZ), typical oxide ceramics, were heat-treated under vacuum at various temperatures between 1300 deg C and 1600 deg C for three hours. All the specimens showed mass loss as a result of the heat-treatment. The amount of mass loss of the alumina was greater than that of the Y_2O_3-PSZ. Although the mass loss seemed to be due to vaporization from the specimen-surface, vapor species were not identified. The bending strength of the alumina and the Y_2O_3-PSZ did not show remarkable change due to heat-treatment up to 1500 deg C, but degraded significantly at 1600 deg C. It is considered that one of the factors contributing to strength degradation is grain growth due to heat treatment. The Vickers hardness of the alumina decreased about 10 percent up to 1500 deg C and about 30 percent at 1600 deg C. In the case of the Y_2O_3 - PSZ, the Vickers hardness decreased about 10 percent over whole temperature range investigated. The degree of degradation of the measured physical properties of Y_2O_3-PSZ was less than that of alumina. The Y_2O_3-PSZ was more stable than the alumina under the heat treatment.