Stabilization of Tetragonal ZrO ₂ in ZrO ₂ –SiO ₂ Binary Oxides

Abstract

Gel‐glasses of various compositions in the x ZrO 2 . (10 – x )SiO 2 system were fabricated by the sol–gel process. Precipitation due to the different reactivities between tetraethyl orthosilicate (TEOS) and zirconium(IV) n ‐propoxide has been eliminated through the use of 2‐methoxyethanol as a chelating agent. Thermal treatment of these gels produced crystalline ZrO 2 particles. While monoclinic is the stable crystalline phase of zirconia at low temperatures, the metastable tetragonal phase is usually the first crystalline phase formed on heat treatment. However, stability of the tetragonal phase is low, and it transforms to the monoclinic phase on further heat treatment. In this study, it has been found that the transformation temperature increases as the SiO 2 content in the ZrO 2 –SiO 2 binary oxide increases. The most significant results were from samples containing only 2 mol% SiO 2 , where the metastable tetragonal phase formed at low temperatures and remained stable over a broad temperature range. X‐ray diffraction, transmission electron microscopy, and Fourier transform infrared spectroscopy were used to elucidate the structure of these binary oxides as a function of temperature.