Characterization and metastability of alkoxy-derived tetragonal zirconia powder

The zirconia powders were synthesized through the hydrolysis of zirconiumn-butoxides with air moisture as well as with aqueous solutions of different pH values to investigate the metastability of tetragonal (t)-ZrO₂. The SEM and TEM observations reveal that powders prepared with air moisture hydrolysis consist of spherical particles of 0.5–3.5 m diameter, while gel-like powders composed of finer particles were obtained with aqueous solution hydrolysis. The samples obtained show different crystallization and tetragonal/monoclinic transformation temperatures on differential thermal analysis. The metastability of t-ZrO₂, investigated in terms of relative content with X-ray diffraction, was not explicable through the crystallite size effect. Instead, the existence of unpaired electrons, detected using electron paramagnetic resonance, and the strain within the powders, were found to be probably influential in affecting the metastability of t-ZrO₂.