CHARACTERISTICS AND COMPARISON OF METASTABILITY OF ALKOXY-DERIVED TETRAGONAL ZRO2 POWDERS, GELS AND FILMS

The metastability of t-ZrO2 in the form of ZrO2 powders, gels and films prepared by hydrolysis of zirconium n-butoxides using different techniques, including the sol-gel process, was investigated. The morphologies of the powders, gels and films were observed by scanning electron microscopy. Differential thermal analysis and differential thermal gravimetric curves were used to determine the crystallization temperatures and thermal behavior of the materials. The experimental results indicated that the metastability of t-ZrO2, investigated in terms of relative content and crystallite size by X-ray diffraction, could not be explained simply by the effect of crystallite size, the existence of impurities or unpaired electrons. In this work it is proposed that the strain energy existing among the crystallites is an important factor in determining the metastability of t-ZrO2.