Photoluminescence and Thermoluminescence of MgSO₄, CaSO₄, SrSO₄ and BaSO₄ Powder Phosphors Activated with Tb³⁺

Abstract

The photoluminescence (PL) spectra and optical excitation spectra of phosphors were obtained at temperatures of 10, 80, 300 and 370 K. Many narrow bands were observed in both the spectra, and were attributed to the transitions within the 4 f 8 electron configuration in Tb 3+ . The quenching of the 5 D 3 emission series assigned to the transitions 5 D 3 → 7 F J ( J =6,5,4,3,2,1 and 0) is characteristic of the PL emission spectra. The thermoluminescence (TL) glow curves, TL emission spectra and TL fading properties of the same samples were also observed. The quenching of the 5 D 3 emission series is not observed in the TL emission spectra. The large differences between the features of the TL emission spectrum and the PL emission spectrum are contradictory to the conventional model of the TL emission process. The addition of Na + to the phosphors as a charge compensator is effective in enhancing the PL efficiency, but causes TL fading because of the shallow electron traps due to Na + .