Sintering Behavior of Sol–Gel-Derived Alumina and Alumina–Zirconia Minispheres

Abstract

Alumina and alumina–zirconia minispheres were prepared by sol–gel process. The starting materials used for the preparation of alumina and zirconia sol were aluminium-tri-isopropoxide and zirconium oxychloride, respectively. Alumina sol and zirconia sol were mixed in definite proportions, so that the final composition contained 5, 10, 15, and 20 wt.% ZrO2. The sintering behavior of alumina and alumina–zirconia minispheres were studied by sintering at 1400, 1500, and 1600°C. X-ray diffraction analysis showed the presence of α -Al2O3 in alumina minispheres and α -Al2O3 and t-ZrO2 in minispheres containing 5 wt.% ZrO2 sintered at 1400°C. Monoclinic ZrO2 was also present in the minispheres containing higher amounts of ZrO2 and sintered at higher temperatures. Scanning electron microscopic observation revealed progressive densification with increasing sintering temperature and zirconia content. The density of the sintered spheres was found to be the highest for spheres containing 20 wt.% ZrO2 sintered at 1600°C.