Nanocrystalline Growth Activation Energy of Zirconia Polymorphs Synthesized by Mechanochemical Technique

The synthesis of ZrO2 by mechanochemical reaction using ZrCl4 and CaO as raw materials and subsequent annealing of the products were investigated. The effect of thermal treatment on the structural evolution and morphological characteristics of the nanopowders was studied by X-ray diffractometry, Raman spectroscopy, transmission electron microscopy, scanning electron microscopy, differential thermal analysis and Rietveld refinement. The results showed that the average crystallite size of ZrO2 was less than 100 nm up to around 1100 °C. The activation energy for ZrO2 nanocrystallite growth during calcination was calculated to be about 13,715 and 27,333 J/mol for tetragonal (t-ZrO2) and monoclinic (m-ZrO2) polymorphs, respectively. Mechanism of the nanocrystallite growth of the ZrO2 polymorphs during annealing is primarily investigated.