Thermoluminescence and optically stimulated luminescence of CaSO4:Mn,Tb with different dopant concentrations

Abstract

This study systematically evaluates the thermoluminescence (TL) and optically stimulated luminescence (OSL) properties of CaSO₄ crystals doped with manganese (Mn) and terbium (Tb), focusing on dopant concentrations within the ranges of Mn (0.1 mol % – 2 mol %) and Tb (0.05 mol % – 1 mol %). Synthesized via the slow evaporation route, this investigation is part of an ongoing experimental series initiated by Silva et al. (2022), exploring CaSO₄:Mn,Tb crystals at a concentration of 0.1 mol %, validating their properties for dosimetric purposes. A structural phase identification was conducted using X-ray diffraction and energy-dispersive spectroscopy (EDS) spectra confirming the presence of Tb³⁺ and Mn²⁺ ions in the crystalline matrices. Dosimetric characterization utilized pellets prepared by incorporating Teflon into the phosphors. In-depth investigations involved analyzing TL glow curves and Continuous Wave Optically Stimulated Luminescence (CW-OSL) curves. Observations revealed that TL intensity increased as the co-doped concentration of Tb decreased while maintaining the concentration of Mn constant, in both visible and UV regions. Conversely, at a constant terbium concentration, increasing Mn²⁺ concentration enhanced the sensitivity of low-temperature TL traps in the visible region. However, at higher Mn concentrations, such as 1 % and 2 %, TL intensity in deeper traps decreased. In the UV region, TL signals remained stable as the concentration of Mn²⁺ increased from 0.1 % to 0.5 %, with only a slight shift in peak temperatures. Concentrations above 1 % led to a decrease in TL intensity. All samples produced suitable OSL curves. Fixing Mn²⁺ at 1 mol % and decreasing Tb³⁺ concentration also resulted in increased OSL signals. The optimal Mn²⁺ concentration, with Tb³⁺ fixed at 0.1 mol %, was found to be at 0.1 mol %, where OSL sensitivity was maximized. This research underscores the importance of optimizing dopant concentrations to enhance the potential of these phosphors for precise and reliable dosimetry, thereby advancing both the understanding of these materials and their potential for further development in the field of radiation dosimetry.