XRD AND LASER RAMAN-SPECTROSCOPY INVESTIGATION OF THE STABILITY OF LOW-TEMPERATURE T-ZRO2

The influence of precipitation pH and the presence of Na+ impurities o n the stability of metastable t-ZrO2 were investigated. Zirconia sampl es with a high t-ZrO2 phase content were crystallized from zirconium h ydroxide precipitated at pH 13, 7 and 2.5. The obtained samples were s ubjected to the influence of temperature, pressure and gamma-irradiati on. The influence of these treatments on the metastable t-ZrO2 were in vestigated using XRD and laser Raman spectroscopy. The results of phas e analysis showed that the change in the pH of zirconium hydroxide pre cipitation significantly changed the sensitivity of the metastable t-Z rO2 to temperature and pressure. The metastable t-ZrO2 was most stable in the sample obtained from zirconium hydroxide precipitated at pH 2. 5 and most unstable in the sample obtained from zirconium hydroxide pr ecipitated at pH 7. The presence of Na+ impurities decreased the stabi lity of metastable t-ZrO2. All the samples were shown to be stable und er high gamma-irradiation. The capability of laser Raman spectroscopy for the quantitative analysis was examined by comparing the values of the m-ZrO2 volume fraction (nu(m)) obtained by this technique with the corresponding values obtained by XRD. It was concluded that the relat ion proposed by Clarke and Adar, J. Am. Ceram. Sec. 65 (1982) 284., wa s correct but the reliability of the nu(m) values estimated by the las er Raman spectroscopy was not high, especially in the region of 0.15 < nu(m) < 0.70. The reason for the low reliability in this region is di scussed.