Correlated ESR, PL and TL studies on Sr5(PO4)3Cl:Eu thermoluminescence dosimetry phosphor

Electron spin resonance (ESR), thermoluminescence and photoluminescence studies in Eu2+ activated Sr5(PO4)3Cl phosphor are reported in this paper. The Sr5(PO4)3Cl:Eu2+ phosphor is twice as sensitive as the conventional CaSO4:Dy phosphor used in thermoluminescence dosimetry of ionizing radiations. It has a linear response, simple glow curve, emission peaking at 456 nm. The defect centers formed in the Sr5(PO4)3Cl:Eu2+phosphor are studied by using the technique of ESR. A dominant TL glow peak at 430 K with a smaller shoulder at 410 K is observed in the phosphor. ESR studies indicate the presence at three centers at room temperature. Step annealing measurements show a connection between one of the centers and the dominant glow peak at 430 K. The 430 K TL peak is well correlated with center I, which is tentatively identified as (PO4)2− radical.