Effect of phase change, particle size and annealing in reducing and oxidizing atmospheres on UV-dosimetry characteristics of SrAl2O4:Eu using mechanoluminescence technique

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 ^oC) 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 Fm$\bar{3}$$\bar{3}$m) phases on annealing above 800 ^oC 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 ^oC 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.