Grain Size Effect on Mechanical Strength of MgO-ZrO₂ Composite Ceramics

Abstract

Cubic- and tetragonal-ZrO₂-MgO composite ceramics were prepared by the pressureless sintering at 1650°C for 4h and 1350°C for 24h respectively, and the effect of grain size and ZrO₂ phase on bending strength (at room temperature and 1200°C) was investigated. The bending strength at room temperature of ZrO₂-MgO composite ceramics increased with increasing ZrO₂ content, because the grain size of MgO decreased with ZrO₂ addition. But the effect of ZrO₂ phase on the bending strength at room temperature was not recognized. In the case of bending test at 1200°C, when grain size of MgO was below 6μm, specimens deformed plastically before breakage, and the yield stress at 1200°C of c-ZrO₂-MgO was larger than that of t-ZrO₂-MgO, and fracture stress increased with decreasing the grain size of MgO.