Synthesis and characterization of Al2O3-ZrO2 nanocomposite powder by sucrose process

Nanocrystalline alumina-zirconia powders were prepared by a modified chemical route using sucrose, polyvinyl alcohol (PVA) and metal nitrates followed by a post calcination process. The process involved dehydration of Al3+-Zr4+ ions-sucrose-PVA solution to a highly viscous liquid which on decomposition process produced a black precursor material. The obtained precursor were then calcined at various temperatures: 1,050, 1,100, 1,150, 1,200 and 1,250 A degrees C for different soaking times (1, 2, 4 h) in air. The formation of a nanocomposite composed of alpha-alumina (similar to 20 nm) and tetragonal (t) zirconia (similar to 19 nm) crystallites were confirmed for the sample calcined at 1,200 A degrees C for 2 h, based on our XRD and TEM results. However, for the samples calcined below 1,150 A degrees C the composite formed were composed of metastable alumina (gamma, delta, theta) as well as t-zirconia phases. Interestingly, the zirconia phase retained its tetragonal structure for all the samples calcined above 1,050 A degrees C. This is possibly related to the size effect and reduction of surface enthalpy of the zirconia crystallites surrounded by Al3+ cations.