IDENTIFICATION OF THE UV INDUCED DEFECTS IN SR3GD2SI6O18-PB, MN USING THERMOSTIMULATED LUMINESCENCE (TL) AND ELECTRON-SPIN-RESONANCE (ESR)

Thermostimulated luminescence (TL) has been used to detect UV-induced defects in the green emitting phosphor Sr3Gd2Si6O18: Pb, Mn (SGS: Pb, Mn). Two defects have been revealed in the temperature range of 20-degrees-C to 500-degrees-C following a 185 nm irradiation, with respective activation energies of 0.97 +/- 0.05 eV and 1.28 +/- 0.06 eV. Identification has been partially achieved thanks to their TL emission spectra and with the aid of ESR measurements. One of the defects may imply an oxygen vacancy in association with an interstitial oxygen (i.e. a self-trapped exciton). The second one would involve the dopant lead linked to an oxygen ion in an interstitial position. Thus the luminescence process of SGS: Pb, Mn would be affected because of the absorption levels of these defects which coincide with the emission levels of the ions Pb2+ and Gd3+ and with the 254 nm mercury emission line. This methodological approach in characterizing defects can be extended to other silicate phosphors.