Thermoluminescence Kinetic Parameters and Radioluminescence of RE³⁺ (RE = Pr, Sm, Tb, Ho, Er)-Doped Barium Tantalate Phosphors

The thermoluminescence (TL) kinetic parameters and radioluminescence results (RL) of RE³⁺ (RE = Pr, Sm, Tb, Ho, Er)-doped barium tantalate phosphors have been studied for different concentrations. The concentration quenching occurring at the RL intensity of Pr³⁺ after 1.5 mol% was associated with a cross-relaxation between ³P₀ → ³H₄ and ¹D₂ → ³H₄, while the RL emissions of Tb³⁺ were observed corresponding to transitions of⁵D₄ → ⁷F_J. The asymmetry ratio of RL is relatively high compared to the PL asymmetry ratio for Sm³⁺, which may be attributed to the RL mechanism leading to some decrease in the local symmetry of Sm³⁺ ions. The Ho³⁺ and Er³⁺ show the characteristic green and red emissions corresponding to radiative transitions. Also, the spectral properties of the phosphors have been discussed by comparing the RL results, the reported PL results of Pr³⁺, Sm³⁺, Ho³⁺, Er³⁺ , and the PL results of Tb³⁺ , which were examined in the study. After being irradiated by x-ray and short-wave UV light (254 nm), TL glow curves for Pr³⁺, Tb³⁺, and Er³⁺ doped phosphors were compared in the range of 50 °C and 400 °C at a heating rate of 2 °C s⁻¹. TL glow peaks for Pr³⁺, Tb³⁺, and Er³⁺ formed at temperatures of 77 °C and 208 °C, 87 °C and 263 °C, and 158 °C and 267 C, respectively. The kinetic data were estimated by applying computerized glow curve deconvolution (CGCD) where TL glow curves of BaTa₂O₆:RE³⁺ (RE = Pr, Tb, Er) consist of 5, 6, and 7 estimated glow peaks with figure-of-merit values of 1.06, 1.60, and 1.09, respectively.