Thermally stimulated recombination processes in the YPO4:Bi system

Abstract

The 10-trap model for describing thermally stimulated recombination processes in the YPO₄:Bi system was developed. In addition to the six Bi-related centers, the model includes two shallow unidentified traps and two deep unidentified traps. The model was parameterized (FOM = 5.5 %) using previous experimental data on spectrally selective thermoluminescence (TL) recorded monitoring emission at 3.6 and 5.1 eV. For each trap, the best-fit parameters were obtained: activation energy, frequency factor, trapping and recombination factors; signs of delocalizing charge carriers. The origin of the observed TL glow peaks and the main channels of recombination processes leading to luminescence at 3.6 and 5.1 eV were revealed. The parameterized model was applied to the analysis of the origin of long-lasting afterglow in the YPO₄:Bi system. It was found that at room temperature the first relatively fast component of the afterglow decay kinetics is caused by detrapping charge carriers from shallow traps, manifesting itself as a TL glow peak closest to room temperature: trapped electron center with TL glow peak maximum at about 340 K, which is caused predominantly by electron recombination luminescence; the temperature dependence of the fast component of the afterglow decay kinetics was studied and the origin of the apparent wide TL glow peaks III, revealed earlier by processing the experimental data on YPO₄:Bi, was established. The origin of the second slow component of the afterglow decay kinetics is attributed to processes beyond the scope of this model; only the final stages of the recombination processes that cause the slow afterglow component are discussed.