Influence of Tm³⁺ Concentration on Long Afterglow and Photostimulated Luminescence Properties of Eu²⁺-Doped Sr₁Al₂Si₂O₈ Blue Phosphors

Blue aluminum silicate phosphors of Sr₁Al₂Si₂O₈, Sr_0.98Al₂Si₂O₈:0.02Eu²⁺ and Sr_0.98–xAl₂Si₂O₈:0.02Eu²⁺, xTm³⁺ (x = 0.005, 0.01, 0.02, 0.04, 0.08) compositions are prepared by high temperature solid phase method. Their XRD, fluorescence emission and excitation luminescence properties, afterglow attenuation, afterglow luminescence, thermoluminescence and photostimulated luminescence properties are investigated. The results show that a high purity crystallized phosphor can be successfully prepared at 1350°C for 4 h. It is proven that Eu²⁺ as the luminescent center is replaced by Sr²⁺ with a coordination number of 12; Eu²⁺ and Tm³⁺ are substituted for Sr²⁺, which is the reason for a decrease in the unit cell parameter values. The sample excitation and emission spectra have peak wavelengths of 330 nm and 405 nm. Sr_0.97Al₂Si₂O₈:0.02Eu²⁺, 0.01Tm³⁺ has a minimum afterglow decay rate of 0.61389, which is suitable for use as a long-lasting luminescent blue phosphor. The pyroluminescence indicates that doping with Tm³⁺ significantly deepens the trap level. The photostimulated luminescence proves that the co-doped Tm³⁺ greatly improves the initial intensity and the optical storage performance of the photostimulated luminescence, especially the Sr_0.96Al₂Si₂O₈:0.02Eu²⁺; the 0.02Tm³⁺ sample trap level is 0.8999 eV. The initial photostimulated luminescence intensity of the co-doped sample is shown to be 1000 times that of the single doped Eu²⁺, and the optical storage – 1.8 times that of the single doping case.