Thermoluminescence and infrared stimulated luminescence in long persistent monoclinic SrAl2O4:Eu2+,Dy3+ and SrAl2O4:Eu2+,Nd3+ phosphors

Abstract

We report on the photoluminescence, long persistence luminescence, and thermally and optically stimulated luminescence properties of SrAl2O4:Eu2+,Dy3+ and SrAl2O4:Eu2+,Nd3+ phosphors synthetized by the combustion method and annealed under a carbon atmosphere at 1150 °C for 6 h. XRD indicated the presence of a single monoclinic crystalline phase for both phosphors. After exposure to beta radiation, the phosphors exhibited an intense persistent luminescence lasting more than 220 h. After excitation with 375 nm light the emission spectra depict a broad band peaked at 515 nm, which is the characteristic for Eu2+ emission in SrAl2O4 phosphors, and two weak bands at about 405 and 425 nm. After beta irradiation, the Dy co-doped phosphor exhibits an intense thermoluminescence (TL) with a maximum around 60 °C and a weaker peak at 140 °C. The low temperature TL of the Nd co-doped phosphor consist of three peaks; two well-separated peaks with maxima at about 80 and 160 °C and the third one with the maximum near 50 °C, which becomes evident at doses higher than 10 Gy. Stimulation with IR light of 830 nm releases trapped charges caused by irradiation exposure, generating an intense IR stimulated luminescence (IRSL), which exhibits a typical time decay behavior for continuous wave optically stimulated luminescence. The persistence luminescence and IRSL were related to the release of electrons from the traps responsible for the 60 and 140 °C TL peaks in SrAl2O4:Eu2+,Dy3+ and the 80 and 160 °C TL peaks in SrAl2O4:Eu2+,Nd3+ phosphors, respectively.