Abstract
SrAl2O4:Eu is a known ML phosphor. The material was successfully synthesized using combustion method, downsized to different particle-size ranges (from microcrystalline to nanocrystalline sizes) through ball milling. It was further annealed at different high temperatures (200–800 °C) and characterized by XRD and FESEM. Reorganization of the material from SrAl2O4 (monoclinic, space group P21/c) to Sr2Al6O11 (orthorhombic, space group Pnnm) plus SrO (cubic, space group Fm3̅m) phases on annealing above 800 °C was observed. ML studies show that the electron traps lost during mechanical/thermal stimulation could be regenerated by UV-irradiation. This property of the material was explored here to estimate the doses of UV radiations (UV-A, B and C). Also, dose responses of the materials having different particle size ranges from microcrystalline to nanocrystalline sizes were studied and found that the dose ranges get widened with the particle size decreasing with little sacrifice of the sensitivity. Thus, very high doses of the UV-radiation could also be estimated using ML nanophosphors. Fading at room temperature was little high but remaining ML is good enough for the dosimetry purpose. To the best of our knowledge such kind of detailed study on dosimetry of UV-radiations using ML technique is not found in the literature. It was also found that this material did not yield any ML after annealing the material above 800 °C and even after UV-irradiation. It was further explored by annealing the material in reducing and oxidizing atmospheres that whether it is due to the phase transitions or redox reactions.
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•Different phases, i.e., Sr2Al6O11 (Orthorhombic) and SrO (Cubic) and SrAl2O4 (Monoclinic) identified on annealing above 800 °C for 1.0 h in air.•The variation of the ML intensity with particle size, i.e., decrease in ML intensity with particle size decreasing is important for applications.•Regeneration of traps/luminescence recombination centers (LRCs)/ML by UV light is important for UV dosimetry using ML technique•The material (SAOE) is reusable on annealing at 800 °C in a reducing (10% H2 in Ar) atmosphere, i.e., the lost traps/LRCs/ML could be regenerated.•A model based on defects and redox reactions explaining regeneration, sensitization and quenching has been proposed.