Structure of (ZrO2)x(SiO2)1-x xerogels (x=0.1, 0.2, 0.3 and 0.4) from FTIR, 29Si and 17O MAS NMR and EXAFS

Abstract

A combination of ²⁹Si and ¹⁷O MAS NMR, EXAFS and FTIR spectroscopy has been used to study the atomic structure of (ZrO₂)_x(SiO₂)_1-x (x=0.1, 0.2, 0.3 and 0.4) xerogels prepared by reacting partially hydrolysed tetraethyl orthosilicate with zirconium(IV) propoxide. Results from (ZrO₂)_0.1(SiO₂)_0.9 samples reveal the oxides to be atomically mixed with no evidence of phase separation. In these samples, the nearest neighbour environment of zirconium is similar to that found in cubic zirconia. In the (ZrO₂)_0.4(SiO₂)_0.6 samples, phase separation occurs with a significant proportion of the zirconium present as amorphous ZrO₂ with a local structure similar to that of monoclinic zirconia. ¹⁷O MAS NMR and EXAFS have proven valuable techniques for gauging the level of atomic mixing in these materials.