Thermally stable and photocatalytically active titania for ceramic surfaces

The most photocatalytically active titania modification anatase must be stabilised to achieve high photocatalytic activity in ceramic processes at temperatures above 1000 °C. Thermally stable TiO₂ powders were prepared by the addition of silica and boehmite nanoparticles and deposited on corundum substrates and lead-free glazes. The powders and coatings were fired at increasing temperatures, and stabilisation of the anatase phase was achieved up to 1200 °C. In general, thermal stability was found to be lower when coated on substrates compared to the powder alone, and the extent of reduction depended on the chemical composition of the substrate. Only a slight modification of the titania electronic structure was found, indicating only weak interactions between silica and titania. Based on these results it is possible to assume an amorphous silica and alumina shell encases the titania particles which prevents grain growth and the anatase to rutile phase transformation.