Optical Properties of Anatase and Rutile TiO2:Cr 3+ Powders

Abstract

Anatase TiO2powders doped with 0.5, 1.0, 4.0 and 10 mol% Cr3+have been prepared by hydrothermal method. The Cr3+concentration and annealing effects on crystalline structure, absorption and photoluminescent spectra of the synthesized samples have been investigated. The band gap energy of anatase and rutile TiO2:Cr3+powders with different dopant contents has been determined. Urbach energies (Eu) characterized for the structural disorder in the anatase and rutile TiO2host lattice doped with Cr3+ions also have been calculated with different impurity concentrations. At low annealing temperature (≤600 oC), the samples exhibited anatase phase and the photoluminescent spectra consisted of sharp peaks related to the 2E(2G) →4A2(4F)transitions of ions Cr3+in strong octahedral field. At high annealing temperature (1100 oC), the samples exhibited rutile phase and the photoluminescent spectra had a broad emission band, which was assigned to the 4T1(4F) →4A2(4F) transitions within the Cr3+ions in weak octahedral field