Defect states in Lu3Al5O12 : Ce crystals

Wavelength-resolved TSL measurements after x-ray irradiation at room temperature were performed on undoped, Ce- and (Ce, Zr)-doped Lu3Al5O12 crystals. Several glow peaks were observed in the 20-450 degreesC temperature region, whose intensities and emission spectra are influenced by doping. Namely, the TSL spectra are governed by defect and trace impurity-related emissions in the undoped crystal, while only the Ce3+ emission is detected in the doped crystals. Moreover, EPR measurements performed at 12 K revealed typical spectra of Ce3+ (4f(1) , S =1/2) occupying Lu3+ substitutional positions. In situ light irradiation (250-330 nm) of the crystals results in a step-like decrease of the Ce3+ EPR intensity. Such a behaviour can reflect a creation of Ce4+ ions under UV irradiation or an increase of the Ce3+ population in the excited (5d) state.