On the thermoluminescence properties and mechanism of LuPO4:Eu sintered materials

Abstract

Thermoluminescence (TL) of X-rayed LuPO₄:Eu sintered materials was investigated as a function of the processing parameters and Eu concentration. Sinterability of the powders precipitated from a water solution was found to be much better than that previously reported for hydrothermally made precursors. The mechanism of the TL process was tracked by means of TL and EPR techniques. It was shown that TL efficacy was greatly dependent upon the processing temperature becoming most potent for pellets sintered at 1700 °C. The most potent TL was obtained for materials containing 2% Eu and sintered in vacuum. The high-temperature treatment appeared to be needed to generate defect states able to participate in energy storage by immobilization of excited carriers. With increasing concentration of the activator ions from 0.1% to 5%, the mechanism of TL in LuPO₄:Eu had a continuously more localized character. EPR spectroscopy revealed that Eu³⁺ attracts excited electrons to the conduction band and gets converted to Eu²⁺, while a hole is postulated to be trapped on oxygen ions surrounding a vacant Lu site.