The preparation and surface characterization of zirconia polymorphs

Zirconium hydroxides were obtained by precipitation of zirconium chloride with aqueous ammonia at constant pH followed by hydrothermal treatment The effect of thermal activation of the zirconium hydroxide on physical properties, and the effect of crystalline phase on the surface properties of zirconia were studied. The pressure during the hydrothermal treatment of zirconium hydroxide affected the surface area, particle growth, and phase transformation of the zirconia product. Hydrothermally treated zirconia under atmospheric pressure (LP) shows higher surface area than that under high pressure (HP) and untreated (UT). HP zirconia shows a mixture of tetragonal and monoclinic phase after hydrothermal treatment due to the higher solubility and reprecipitation rate, whereas LP sample shows a tetragonal crystal structure from 600 to 1,050 ℴC. Monoclinic phase zirconia shows greater CO₂ and NH₃ surface adsorption than amorphous and tetragonal phase zirconia. This suggests that the crystal structure of zirconia strongly affects the amount and strength of the surface adsorption site.