Effect of annealing temperature on persistent luminescence of Y3Al2Ga3O12:Cr3+ co-doped with Ce3+ and Pr3+

Y3(Al,Ga)5O12 (YAGG) materials doped with Ce3+, Cr3+ and Pr3+ were synthesized by using a modified Pechini method and subsequently annealed in air at selected temperatures between 900 and 1500 °C. According to X-ray powder diffraction (XRPD) and transmission electron microscopy (TEM) analyses, the particles and size distributions become large and broad, respectively, due to sintering and agglomeration at high annealing temperatures. Based on infrared (FTIR) spectra and calculation of multi-phonon de-excitation probabilities, the high energy O–H vibrations are not causing significant multi-phonon de-excitation of the emitting 5d level of Ce3+ if the annealing temperature is above 900 °C. The analysis of the photoluminescence excitation (PLE), photoluminescence (PL) and persistent luminescence (PersL) spectra as well as the luminescence decay curves revealed that both the energy transfer efficiency and luminescence intensity increase with increasing annealing temperatures. The charge carrier trapping-detrapping model was applied to explain the PersL mechanism of the YAGG materials studied.