Structure of (ZrO_2)_x(SiO_2)_(1-x) xerogels (x = 0.1, 0.2, 0.3 and 0.4) from FTIR, ~(29)Si and ~(17)O MS NMR and EXAFS

摘要

A combination of ~(29)Si and ~(17)O MAS NMR, EXAFS and FTIR spectroscopy has been used to study the atomic structure of (ZrO_2)_x(SiO_2)_(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 (ZrO_2)_(0.1)(SiO_2)_(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 (ZrO_2)_(0.4)(SiO_2)_(0.6) samples, phase separation occurs with a significant proportion of the zirconium present as amorphous ZrO_2 with a local structure similar to that of monoclinic zirconia. ~(17)O MAS NMR and EXAFS have proven valuable techniques for gauging the level of atomic mixing in these materials.