XRD, WAXS, FTIR, and XANES studies of silica-zirconia systems

The structural characteristics of polymorphic raw material combinations of silica-zircogia powder systems were investigated through X-ray diffraction (XRD), Wide-angle X-ray scattering (WAXS), Fourier transform infrared (FTIR), and X-ray absorption near edge structure (XANES). Stoichiometric mixtures (1:1 mol% ratio) of silica (SiO2: amorphous and cristobalite) and zirconia (ZrO2: amorphous and tetragonal zirconia) were prepared with the addition of polyvinyl alcohol (PVA) and a ball-mill mechanical activation of 5 h, followed by calcination at 1000 and 1200 degrees C. The identified phases of the calcined powders were a combination of zircon, zirconia, and cristobalite. Quantitative phase analyses of the XRD and WAXS data based on the Rietveld method revealed that the amorphous-amorphous (AA) mixture contained a higher zircon composition than the others, ca 93 mol%, at a calcination temperature as low as 1000 degrees C. Rietveld analysis of the WAXS data was in good agreement with that of the XRD data. The PVA and ball-mill mechanical activation simultaneously enhanced the solid-state reaction. The peaks of IR absorption associated with zircon were observed at wavenumbers around 435, 615, and 900 cm(-1). The IR absorption peak observed at around 1000 cm(-1) indicated silica-rich content in the AT1000 and CA1000 samples. A Si K-edge XANES analysis indicated a structural distortion around Si in the zircon containing samples as compared to the silica, resulting in an extra lower-energy peak. The ratio between the absorption intensities of the extra and the highest peaks, in general, confirmed the phase composition of zircon in the samples.