Effect of terbium and silver co-doping on the enhancement of photoluminescence in CaSO4 phosphors
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In this work, the photoluminescence properties of CaSO4 crystals co-doped with terbium and silver from silver oxide or silver nanoparticles (NPs) in different concentrations are investigated. Phosphors are obtained by means of a slow evaporation route and calcined at 600 °C for 1 h. X-ray diffraction analysis shows the formation of a single-phase anhydrite structure with orthorhombic symmetry. The photoluminescence properties are investigated using vacuum ultraviolet, ultraviolet and X-ray excitation. All luminescent measurements reveal the characteristic emissions of Tb3+. The analyses using excitation with ultraviolet light show that the Ag NPs are able to generate structural defects more satisfactorily compared to CaSO4:Tb with silver oxide. We also observe that higher concentrations of Ag increase the Tb3+ emission intensity, while higher concentrations of Ag NPs decrease it. The good stability of CaSO4 results in an efficient energy transfer from the host lattice to the activator under X-ray excitation, with the NPs contributing to the increase in luminescent intensity. Investigation of the terbium valence in the CaSO4 host shows a complete reduction of the Tb4+ present in Tb4O7 to Tb3+, as indicated by the X-ray absorption near edge structure. The vacuum ultraviolet excitation spectra reveal three broad bands, attributed to the charge-transfer excitations within SO42− complexes and to the 4f8 → 4f75d1 transitions on Tb3+. Our results also reveal that silver particles are responsible for generating deeper capture centers.
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SILVA, ANDERSON M.B.; SILVEIRA, WELLISSON S.; MATOS, TAWANY S.; JUNOT, DANILO O.; REZENDE, MARCOS V.S.; SOUZA, DIVANIZIA N. Effect of terbium and silver co-doping on the enhancement of photoluminescence in CaSO4 phosphors. Optical Materials, v. 111, p. 1-8, 2021. DOI: 10.1016/j.optmat.2020.110717. Disponível em: http://repositorio.ipen.br/handle/123456789/31969. Acesso em: 30 Dec 2025.
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