Thermoluminescent analysis of CaSO₄:Tb,Eu crystal powder for dosimetric purposes

The motivation of this work was to produce crystals of CaSO₄ doped with an unusual combination of RE elements such as terbium (Tb) and europium (Eu) in different concentrations, and analyze its thermoluminescent (TL) properties. The crystals were produced by the slow evaporation route using calcium carbonate (CaCO₃) as precursor, and incorporating the dopants (Tb₂O₃ and Eu₂O₃) in a solution of sulfuric acid, that is evaporated and collected again, leaving just CaSO₄:Tb,Eu crystal powder. The terbium and europium ions were incorporated in concentration ratios of 1:1, 2:1 and 5:1 (weight proportions). X-ray diffraction analyses showed that samples of doped CaSO₄ exhibit only a single phase corresponding to the crystal structure of anhydrite. The radioluminescence confirmed the presence of Tb³⁺ and Eu²⁺ in the crystal matrix. The CaSO₄:Tb,Eu crystal powders showed TL emission glow curves with three peaks centered around 170 °C, 270 °C and 340 °C, after irradiation with a ⁹⁰Sr/⁹⁰Y source. Thermoluminescent (TL) characteristics such as linearity, reproducibility and fading were evaluated. Samples produced with concentration ratio of 2:1 of Tb and Eu showed the highest TL intensity. The produced CaSO₄:Tb,Eu samples present TL properties useful for dosimetric purposes. - Highlights: • Thermoluminescent properties of CaSO₄ doped with Tb and Eu were evaluated. • Crystals were grown using a new production route based in the Yamashita method. • The CaSO₄:Tb,Eu samples presented a 170 °C suitable for TL dosimetry. • The TL response of the CaSO₄:Tb,Eu material was linear and reproducible. • TL signal fading of samples was around 30% after one month of irradiation.