Abstract
Zirconia was synthesized by sol-gel and post-hydrothermal treatment under autogenous pressure in order to study the effect of synthesis methods on its structural and textural properties. On the basis of thermal analysis, in situ X-ray diffraction and Raman spectroscopy techniques, the synthesis processes exhibit similar thermal behavior and zirconia phase transformation. The effect of in situ calcination temperature on the crystallization behavior, crystal phase transition, and crystallite size analysis was studied. The results obtained revealed that amorphous zirconia transformed into tetragonal phase above 400 A degrees C and thermally stabilized up to 700 A degrees C. A biphasic mixture of tetragonal and monoclinic zirconia was formed at 750 A degrees C. Activation energy of sintering due to grain growth mechanism predicted that the zirconia phase transformation is due to the increase in the crystallite size of tetragonal phase above its critical size. The post-hydrothermal treatment resulted in the formation of high surface area mesoporous zirconia (213 m(2) g(-1)). Upon increasing the calcination temperature, a pronounced decrease in the specific surface area of zirconia samples due to sintering process and phase transformation.