Study of anomalous emission and irradiation effect on the thermoluminescence properties of barium aluminate

The photoluminescence (PL) and thermoluminescence (TL) properties of BaAl2O4:Eu2+ phosphor synthesized by the combustion method is studied. Electron beam and gamma rays are used for irradiating the phosphor while performing TL measurements. The structural and morphological analysis of the resulting phosphor was carried out by X-ray diffraction study and scanning electron microscopy, whereas their optical properties were examined by PL spectroscopy and TL glow curve measurements. The intense bluish green broad band emission near 494 nm that originates from 5d to 4f transition in Eu2+ ions was observed in the BaAl2O4:Eu2+ phosphor. The broad band emission was further examined, showing that emission consist of two broad peaks originating due to occupation of two different lattice sites by Eu in BaAl2O4 host. The occurrence of two broad bands with large stokes shift and hence anomalous emission is explained by proposing energy level model. Calculations based on Dorenbos formulations were carried out which support the presence of anomalous emission in BaAl2O4:Eu2+ phosphor. The TL response of BaAl2O4:Eu2+ phosphor for two different radiations was compared and studied in detail. Detailed process and possible mechanisms for PL and TL are studied and discussed with the help of energy level models. -- Highlights: •This study reports the anomalous emission in BaAl2O4:Eu2+ phosphor. •The Eu3+ reduces to Eu2+, when prepared in open atmosphere by the combustion method. •We found that anomalous emission is related to the position of the 5d excited level of Eu2+ relative to the conduction band levels of the host material. •Comparative study of TL was carried out for two different radiations. •The energy level model presented here is helpful in understanding the anomalous emission