Influence of the synthesis conditions on the properties of hydrous zirconia and the stability of low-temperature t-ZrO2

The influence of processing parameters (pH value, type of anion, and reaction temperature) on the properties of hydrous zirconia, prepared by hydrolytic condensation of zirconium n-propoxide, has been investigated. The obtained amorphous samples and their crystallization products were characterized using BET analysis, TG analysis, DSC, XRD, FT-IR and laser Raman spectroscopy. Specific surface area of the samples increased with an increase in the reaction temperature and processing pH value up to 7.5. Further increase in the pH value caused a small decrease in the specific surface area of the samples. Most of the crystallization products, obtained on calcination of the samples at 400 degrees C, contained tetragonal (t-)ZrO2 as the dominant phase. The stability of t-ZrO2 to the influence of pressure (500, 1000 and 1350 MPa) showed to be pH dependent. On the other hand, the stability of t-ZrO2 to the influence of temperature (600 and 800 degrees C) could not be attributed to the influence of the pH value alone. Lattice strains in the t-ZrO2 products increased almost linearly with an increase in the pH value, while the crystallite size showed to be independent of the pH value. Mechanical treatment of the hydrous zirconia samples caused an increase in both the crystallite size and t-ZrO2 content in the corresponding crystallization products, but the stability of t-ZrO2 remained approximately the same. It was concluded that the observed differences in the t-ZrO2 stability resulted from the combining influences of more than one experimental factor. (C) 2000 Elsevier Science S.A. All rights reserved.