Photoluminescence and afterglow of Dy3+ doped CaAl2O4 derived via sol–gel combustion

Abstract

With doping concentration varying from 0.1 to 5.0 mol%, a series of Dy³⁺ doped calcium aluminate (CaAl₂O₄:Dy³⁺) phosphors were synthesized via a sol–gel combustion technique. The phase, morphology, photoluminescence (PL), afterglow, and thermoluminescence (TL) glow curves of CaAl₂O₄:Dy³⁺ were investigated by means of X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, PL spectroscopy, afterglow spectroscopy, and TL dosimetry, respectively. It is found that: (i) oxygen vacancies and Dy³⁺ work as two independent sets of luminescence centers of PL for CaAl₂O₄:Dy³⁺; (ii) Dy³⁺ works as the luminescence center of afterglow for CaAl₂O₄:Dy³⁺; (iii) the afterglow of CaAl₂O₄:Dy³⁺ lasts for about 115 min at the optimal doping concentration of around 0.8 mol%; and (iv) multiple traps, which are sensitive to doping concentration, are present in CaAl₂O₄:Dy³⁺. The PL and afterglow mechanisms of CaAl₂O₄:Dy³⁺ are discussed to reveal the processes of charged carrier excitation, migration, trapping, detrapping, and radiative recombination in CaAl₂O₄:Dy³⁺.