Effect of ZrO2 on phase transformation of Al2O3

This study investigates the effect of ZrO₂ on phase transformation of alumina. Alumina and alumina–zirconia composite powders were produced by the precipitation method from aluminum sulfate and zirconium sulfate precursors. Precipitates obtained at 15 °C were dried at 80 °C for 72 h, and then calcinated at four different temperatures; 1000 °C, 1100 °C, 1200 °C and 1300 °C for 1 h. Powders calcinated at 1300 °C were pressed uniaxially and sintered at 1600 °C for 1 h. XRD and DSC analyses showed that the presence of zirconia retarded the transformation to α-alumina. SEM studies on the powders calcinated at 1300 °C revealed that both alumina and alumina–zirconia particles were 100–300 nm in size and of near spherical shape. Zirconia additions inhibited abnormal grain growth of alumina and provided homogeneous, equaxied grain structure.