Existence of the uranyl ion at regular Sr site in U doped SrBPO5

Actinide doped alkaline earth borophosphates of the general formula MBPO5 (M = Ca2+, Sr2+, Ba2+) are of special interest due to array of defect centers that can be generated in these compounds by internal (α and γ) irradiation effects. Further, the crystalline alkaline earth borophosphates are also reported to be isostructural with stillwellite-LnBSiO5, which are built up by BO4 and SiO4 tetrahedra. This structure suggests that the host MBPO5 should be a good matrix for luminescence investigations for suitable activator ions. The important advantages of MBPO5 type systems are their high luminescence, moderate preparation temperature and low thermal degradation. XRD pattern of the prepared phosphor confirmed the formation of SrBPO5 in a single phase. The presence of uranium in SrBPO5 sample was ascertained from Energy Dispersive X-ray Fluorescence (EDXRF) measurements performed on a Jordan Valley instrument. The U content in the sample was found to be about 0.85%. An Inductively Coupled Plasma Atomic Emission Spectrometric (ICP-AES), Jobin Yvon, France was used for analysis of the sample, which showed all other metallic impurities except U to be present at concentrations below <10 μg/g. In order to understand the luminescence properties of SrBPO5:U, PL, TSL and ESR studies were conducted on the solid state route samples. PL and TSL techniques were used with a view to understand the species responsible for the luminescence and its site symmetry