Photoluminescence, thermo- and optically stimulated luminescence properties of Eu³⁺ doped Sr₂P₂O₇ synthesized by the solvent evaporation method

In this research, undoped and Eu³⁺ (0.5, 1, 3, 5, 8 and 10 mol%) doped strontium pyrophosphate (Sr₂P₂O₇) powders were synthesized by the solvent evaporation method and their luminescence properties were studied by photoluminescence (PL), thermoluminescence (TL) and, for the first time, optically stimulated luminescence in continuous wave modality (CW-OSL). The Sr₂P₂O₇:Eu³⁺ material was structural and morphological characterized using X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The PL excitation and emission spectra exhibited transitions related to Eu³⁺ ions into the Sr₂P₂O₇ host lattice. In the excitation spectrum an intense broad charge transfer band around 267 nm was observed in all doped samples. A chemical reduction process of the Eu³⁺ ions incorporated in the Sr₂P₂O₇ host is carried out when the samples are exposed to ⁹⁰Sr beta particles and it is a crucial factor in the TL and CW-OSL responses. The TL response of the Eu³⁺ doped Sr₂P₂O₇ samples, displays light emissions associated with the presence of Eu³⁺ and Eu²⁺ ions. The undoped Sr₂P₂O₇ showed TL maxima at 95, 150 and 230 °C and CW-OSL fast decay when the samples are stimulated with infrared light. All Sr₂P₂O₇ and Sr₂P₂O₇:Eu³⁺ (0.5 and 1 mol%) samples showed TL and CW-OSL linear response in the range of 0.5–25 Gy and acceptable repeatability with a variation coefficient lower than 5%. Using CW-OSL and TL dose-response the minimum detectable dose was estimated as 2 mGy (TL-0.5 mol%), 3 mGy (TL-1 mol%), 14 mGy (TL-undoped) and 2 mGy (CW-OSL-undoped).