Grain growth inhibition and mechanical property enhancement by adding ZrO2 to Al2O3 matrix

The critical amount and critical size of ZrO₂ for effective dragging of grain boundary migration occurred at 8 vol% addition for Al₂O₃ ceramic composite, pressureless-sintered at 1600°C for 2h. The fracture toughness was increased from 4·1 to 5·4 MPa m^1/2, and the flexural strength from 290 to 410 MPa at optimal conditions. The enhancement of mechanical properties is attributed to the stress-induced phase transformation toughening when ZrO₂ particles were located intergranularly. Al₂O₃ grain growth is inhibited by ZrO₂ particles pinning at the grain boundaries.