Photoinduced effects in EPR spectra of copper doped potassium tantalate

The UV illumination effects in KTaO3 single crystals with Cu2+ impurity ions have been studied by electron paramagnetic resonance method. Single crystals both "as-grown" and thermally treated in oxygen atmosphere were investigated. It was found that the EPR signal of the Cu2+ centers decreases in the "as-grown" crystals during UV-irradiation at 365 nm, in the whole investigated temperature range (3.7-300 K). On the contrary, for the oxidized specimens a sizeable increase of the EPR signal of Cu2+ centers (except the signal from exchange coupled pair centers) is observed under UV illumination in some