Radio-photoluminescence properties of Eu-doped SrAl 2 O 4 ceramics and thermally assisted charge transfer process

Radio-photoluminescence (RPL) properties of Eu-doped SrAl 2 O 4 are studied focusing on the generation of a luminescent center by ionizing radiation of X-ray and its extinction by a thermally assisted charge transfer. The single phases of SrAl 2 O 4 doped with Eu at concentrations of 0.05–1.0% are synthesized via solid-state reactions, as confirmed by X-ray diffractions analyses. They show photoluminescence (PL) due to both Eu 3+ and Eu 2+ , and the PL intensity due to Eu 3+ decreases after X-ray irradiation while the one due to Eu 2+ notably increases. This indicates that Eu 2+ as a luminescence center is generated as RPL through reduction from Eu 3+ to Eu 2+ by ionizing radiation of X-ray. Particularly, the 0.1% Eu-doped sample shows the highest sensitivity to X-ray dose, and the lowest detection limit is estimated to be 0.3 Gy with the present reader system. The RPL signal is reasonably stable, and it depends on the concentration of Eu. In the case of 1.0% Eu-doped sample, signal fading is not observed even after 20 times of PL measurement. Despite the stable signal, the RPL can be intentionally reversed by heat. Particularly, the 0.1% Eu-doped sample shows a 90% decrease by heating at 500 °C for 10 min. The erasure of signal was explained as a thermally assisted charge transfer, which is supported by the thermally stimulated luminescence studies.