Influence of pH on the stability of low temperature t-ZrO2

Article abstract of DOI:10.1016/S0022-3697(98)00028-6

The influence of the conditions of the chemical synthesis on stability of metastable t-ZrO₂ was studied. Zirconia samples were crystallized from zirconium hydroxide precipitated at pH 13, 7 and 2.5. In all the samples, t-ZrO₂ was the dominant phase but the m-ZrO₂ phase was also present as a minor component. The samples obtained were subjected to the influence of temperature (500 and 700 °C), pressure (500, 1000 and 1350 MPa) and γ-irradiation (10 MGy). The results of phase analysis showed that the change in the pH of zirconium hydroxide precipitation significantly changed the sensitivity of the metastable t-ZrO₂ to temperature and pressure. The metastable t-ZrO₂ was the most stable in the sample obtained from zirconium hydroxide precipitated at pH 2.5 (a decrease of 2% of the starting t-ZrO₂ phase after heating at 700 °C and a decrease of 35% after the application of a pressure of 1350 MPa) and the most unstable in the sample obtained from zirconium hydroxide precipitated at pH 7 (a decrease of 97% of the starting t-ZrO₂ phase after heating at 700 °C, and a decrease of 65% after application of a pressure of 1350 MPa). The effects of the factors mentioned were monitored by X-ray powder diffraction and laser Raman spectroscopy. The results of laser Raman spectroscopy indicated that, without regard to the precipitation pH, γ-irradiation had very little influence on the metastable t-ZrO₂.