Pressureless sintering of sol-gel derived alumina–zirconia composites

Alumina–zirconia (pure zirconia, 12 mol % ceria stabilized zirconia and 3 mol% yttria stabilized zirconia) composites containing 5, 10, 15, 20 and 25 vol.% zirconia were prepared by sol-gel technique. The procedure involved the following steps: preparation of stable (hydrous) alumina and zirconia sols, mixing of sols in proper ratio, to obtain the final precursor with the desired composition and finally stabilizing the mixed sols. Thermal analysis was carried out for the dried precursor. The sol-gel derived precursors were calcined at different temperatures and their crystallization behavior was studied using X-ray diffraction (XRD) technique. Samples calcined at 950°C sintered well than those calcined at other temperatures. All the samples were sintered at 1530°C for 3 h by pressureless sintering, which yield upto 99.8% of the theoretical density of the composite.