Synchrotron-based studies of transition metal incorporation into silica-based sol-gel materials

Previous structural studies on titania- and zirconia-silica xerogels have shown the occurrence of homogeneous mixing at low metal content, and phase separation at high metal content. The use of additional, complementary, synchrotron-based methods can contribute to a fuller structural description of these materials. We present new X-ray absorption near edge structure (XANES) and SAXS results for (ZrO2)(x)(SiO2)(1-x) xerogels and compare them with previous results for (TiO2)(x)(SiO2)(1-x) xerogels. Significant differences between (TiO2)(x)(SiO2)(1-x) and (ZrO2)(x)(SiO2)(1-x) xerogels are observed in the affects of heat treatment on the coordination of homogeneously mixed metal atoms, and in the development of phase separated metal oxide regions.