Phase composition and optical properties of sol-gel derived TiO2 – CeO2 films

Abstract

This paper examines the possibility to produce TiО2 – CeO2 films (2 to 15 mol % СеО2) by sol-gel method using sols without stabilisers. It was established that butanol, tetrabutoxytitanium and cerium(III) nitrate sols become capable to form films on day 3 after their preparation due to hydrolysis, electrostatic interaction of hydrolysed salts with the solvent molecules, and polycondensation. When added, cerium(III) nitrate changes the viscosity of sols and the thickness of resultant films. Results of thermal, X-ray phase analyses and of electron probe microanalysis showed that the thermal destruction of sols at 600 oC within the entire range of СеО2 addition studied leads to the formation of oxide system TiО2 – CeO2, which is a mixture of two phases: a crystalline phase of titanium dioxide with an anatase structure (max. crystal grain size ~7 nm) and an X-ray amorphous phase of cerium dioxide. The TiО2 – CeO2 films obtained on glass substrates have the thickness of 49–62 nm, the refraction index of 1.79–1.89 and the visible-region transmittance of 80–95%. An increase in the amount of cerium dioxide from 2 to 15 mol % leads to a decrease of the forbidden band width from 2.35 to 2.05 eV. The TiО2 – CeO2 films examined in this paper have a greater visible-region transmittance and a smaller forbidden band width compared with popular films of similar composition produced from sols with toxic surfactants.Support for this research was provided under the Development Programme of the Tomsk State University Priority 2030.