Abstract

A combination of ²⁹Si and ¹⁷O MAS NMR, EXAFS and FT-IR spectroscopy has been used to study the atomic structure of (Ta₂O₅)_x(SiO₂)_{1 − x} (x = 0.05, 0.11, 0.18 and 0.25) xerogels prepared by reacting partially-hydrolysed tetraethyl orthosilicate with tantalum(V) ethoxide. Amorphous tantala, a-Ta₂O₅, xerogels have also been prepared and their structures studied in detail for the first time. Results have shown that in all these materials, Ta adopts predominantly 5-fold coordination with respect to oxygen. For the mixed oxide xerogels, partial phase separation of the two component oxides occurs for x > 0.11.