Thermostimulated luminescence, photoluminescence and X-ray-induced luminescence in CaSO4:Ce;: CaSO4:Ce, Na;: CaSO4:Ce, Mn and CaSO4:Ce, Mn, Na phosphors

Thermostimulated luminescence (TSL) and photoluminescence (PL) studies were carried out on CaSO4:Ce; CaSO4 : Ce, Na; CaSO4 : Ce, Mn and CaSO4 : Ce, Mn, Na phosphors with the aim of studying their PL and TSL processes as well as the energy transfer and the effect of charge compensation. Following gamma-irradiation, a drastic reduction in Ce3+ fluorescence was observed in all these samples. To explain the peculiar nature of the TSL glow curve of CaSO4 : Ce, the gamma-ray-induced oxidation of Ce3+ ions (i.e., Ce3+ --> Ce4+ + e(-)) is proposed as a viable mechanism of hole trap production. Post-irradiation thermal annealing and optical bleaching data shows a coincidence between one of the recovery steps of Ce3+ fluorescence and the 400 degrees C TSL peak readout. However, dramatically opposing trends were witnessed in the PL and TSL efficiencies of CaSO4 : Ce3+ with the co-doping of Na+ charge compensator. The presence of Ce3+ emission in the Mn2+ induced 92 degrees C peak as well as the differences in the emission spectra of Mn2+ in the TSL glow peaks and in the PL spectra of Mn2+ excited via Ce3+ in CaSO4 : Ce, Mn indicate the absence of energy transfer from one activator ion to another during TSL. The glow peak temperature-dependent spectral emission of CaSO4 : Ce, Mn as well as the X-ray-induced luminescence spectral data are however consistent with the energy transfer model proposed by Morgan and Stoebe. Unlike the results reported in literature, the TSL sensitivity of 400 degrees C peak in CaSO4 :Ce, Mn is found to be less than that in CaSO4 : Ce. (C) 2000 Elsevier Science B.V. All rights reserved.