A highly thermally stable anatase phase prepared by doping with zirconia and silica coupled to a mesoporous type synthesis technique

Abstract

A zirconia and silica co-doped titania material was prepared from a sol–gel method which had been modified to include an organic templating agent. The product was only poorly mesoscopically ordered. However, the materials produced exhibited a very high temperature for the anatase to rutile phase transition (ART) such that even calcination at 1100 °C for extended periods did not completely remove the anatase phase. This was a much higher ART temperature than pure TiO₂ and a similarly doped sample made in the absence of a templating agent. Data are compared to prepared mesoporous non-doped titanias. These exhibited low ART temperatures compared to non-mesoscopically prepared titania and the acceleration of the phase transformation can be explained in terms of strain induced by the mesoporous structure. For the highly stable doped anatase phase made using the template it was concluded that addition of the dopants stabilised the system to mass transport and reduced mesoporous related strain thereby retarding the phase transition. The ART was also retarded by the high surface area of the mesoscopically templated doped material.