Electron paramagnetic resonance study of transition-metal-ion impregnated brookite titanium dioxide powders

Abstract

Samples of polycrystalline brookite titanium dioxide (TiO₂) powders have been impregnated with the transition-metal ions Fe³⁺, Cr³⁺ and Mn²⁺, and subjected to calcination at various temperatures up to 950 °C. The EPR spectra of samples heated to 650 °C indicated that the dopant ions had migrated from the surface into the bulk of the brookite. For samples heated above 650 °C, significant changes in the EPR spectra were observed. These were attributed to the structural transformation of the brookite crystal host first to the anatase and subsequently the rutile forms of TiO₂.