Abstract
The photocatalytic activity of Bismuth-codoped Sr4 Al14 O25 : Eu2+ , Dy3+ persistent phosphors is studied by monitoring the degradation of the blue methylene dye UV light irradiation. Powder phosphors are obtained by a combustion synthesis method and a postannealing process in reductive atmosphere. The XRD patterns show a single orthorhombic phase Sr4 Al14 O25 : Eu2+ , Dy3+ , Bi3+ phosphors even at high Bismuth dopant concentrations of 12mol%, suggesting that Bi ions are well incorporated into the host lattice. SEM micrographs show irregular micrograins with sizes in the range of 0.5-20μm. The samples present an intense greenish-blue fluorescence and persistent emissions at 495nm, attributed to the 5d-4f allowed transitions of Eu2+ . The fluorescence decreases as Bi concentration increases; that suggest bismuth-induced traps formation that in turn quench the luminescence. The photocatalytic evaluation of the powders was studied under both 365nm UV and solar irradiations. Sample with 12mol% of Bi presented the best MB degradation activity; 310min of solar irradiation allow 100% MB degradation, whereas only 62.49% MB degradation is achieved under UV irradiation. Our results suggest that codoping the persistent phosphors with Bi3+ can be an alternative to enhance their photocatalytic activity.
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