Effect of calcination on nanoscale zirconia produced by high temperature hydrolysis

Acidic and ammoniacal zirconium chloride solutions were subjected to high temperature hydrolysis (HTH) at temperatures between 110 and 150°C. The precipitates obtained from ammoniacal solutions were identified as monoclinic zirconia of Baddeleyite type as dried at room temperature (RT). Their lattice parameters varied between 5.004 and 5.493 Angstrom (Å), and crystallite size between 0.99 and 1.58 nm. The BET specific surface area of the dry powder was measured between 144 and 183 m²/g, corresponding to the equivalent particle diameter of 6.94 and 5.37 nm, respectively. Analysis carried out using field emission scanning electron microscope (FESEM) indicated that the size of zirconia particles ranged between 20 and 220 nm. Calcination of zirconia precipitates at 800°C for 2 hours (h) in air increased the crystallinity and crystal size of the precipitate, and affected the monoclinic crystal structure. It was also observed that the monoclinic crystal structure partially transformed into cubic and tetragonal zirconia.