Microwave photodielectric and photoconductivity studies of commercial titanium dioxide pigments: the influence of transition metal dopants

The effect of transition metal ion doping on the charge carrier dynamics in commercial TiO2 pigments has been investigated. The response to extended p olychromatic irradiation was monitored by real-time measurements of microwa ve photoconductivity and photodielectric effects. In addition to intrinsic differences between the rutile and anatase polymorphs, shifts in the resona nce frequency and quality factor of a tuned microwave cavity as a function of annealing, and foreign-ion incorporation provided a gauge of the influen ce of extrinsic trapping centres on photoactivity. Parallel luminescence st udies revealed an extension in the lifetime of the emission band on doping, the energy associated with recombination being independent of the dopant i on. (C) 1998 Kluwer Academic Publishers.