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 reacti on temperature) on the properties of hydrous zirconia, prepared by hydrolyt ic condensation of zirconium n-propoxide, has been investigated. The obtain ed amorphous samples and their crystallization products were characterized using BET analysis, TG analysis, DSC, XRD, FT-IR and laser Raman spectrosco py. 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 s amples. Most of the crystallization products, obtained on calcination of th e samples at 400 degrees C, contained tetragonal (t-)ZrO2 as the dominant p hase. The stability of t-ZrO2 to the influence of pressure (500, 1000 and 1 350 MPa) showed to be pH dependent. On the other hand, the stability of t-Z rO2 to the influence of temperature (600 and 800 degrees C) could not be at tributed to the influence of the pH value alone. Lattice strains in the t-Z rO2 products increased almost linearly with an increase in the pH value, wh ile the crystallite size showed to be independent of the pH value. Mechanic al treatment of the hydrous zirconia samples caused an increase in both the crystallite size and t-ZrO2 content in the corresponding crystallization p roducts, but the stability of t-ZrO2 remained approximately the same. It wa s concluded that the observed differences in the t-ZrO2 stability resulted from the combining influences of more than one experimental factor. (C) 200 0 Elsevier Science S.A. All rights reserved.