Thermal behavior of ZrO2 precursors obtained by sol-gel processing

Three different zirconia precursors were synthesized from zirconium(IV)-pro poxide by sol-gel processing at pH 1.5, 5.5 and 10.5. The first crystalliza tion products, obtained after the calcination of ZrO2 precursors at 400 deg rees C, contained metastable t-ZrO2 as a dominant phase. The sensitivities of metastable t-ZrO2 products to the influence of temperature (600 degrees C and 800 degrees C) or pressure (500, 1000 and 1350 MPa) were monitored by laser Raman and FT-LR spectroscopies. X-ray powder diffraction was used as a complementary technique. It was found that the pH, used during the sol-g el processing of the ZrO2 precursor strongly influenced the sensitivity of the metastable t-ZrO2 products to the influence of temperature or pressure. The most stable t-ZrO2 product was obtained from the ZrO2 precursor precip itated at pH 1.5 and the most susceptible from the precursor precipitated a t pH 5.5. (C) 1999 Elsevier Science B.V. All rights reserved.