Radiation induced defects in Sr2B5O9Br:Ce3+ storage phosphor

Abstract

Radiation induced defects in polycrystalline pure andCe3+ dopedSr2B5O9Br storagephosphors have been investigated using EPR and optical absorption methods. The EPR of irradiatedpure Sr2B5O9Br represents two overlapping spectra in the 335–340 mT range from paramagnetic electron andhole trapping centres, which are stable at room temperature. These centres are attributed toF(Br−) and OBr− centres, i.e. an electron trapped in a bromine vacancy and a hole trapped on an oxygen ionat a bromine site. The transitions of F(Br−) centres cause the optical absorption band at 560 nm. Another observedabsorption band at 365 nm was attributed to the transitions ofO− centres. Thus electron and hole trapping in pureSr2B5O9Br occursin VBr and OBr2− aggregates, which are created during the synthesis.EPR and optical absorption measurements onCe3+ doped Sr2B5O9Br reveal similar defects as in pure material. It is very likely that the same defects take part inthe processes of thermally and photo-stimulated luminescence.