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

• 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.

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.