Preparation, characterization and emission of Na3-3xLnxFe2(PO4)3 (Ln = Eu, Tb; 0 < x < 0.1 mol %) and photocatalytic activity of Na3Fe2(PO4)3

Rare earth doped compositions Na(3-3x)Ln(x)Fe(2)(PO4)(3) (x = 0, 0.025, 0.05, 0.075 and 0.1) were prepared by ion-exchange method using Na3Fe2(PO4)(3) and LnCl(3) (Ln = Eu and Tb). Pristine Na3Fe2(PO4)(3) was obtained by ethylene glycol assisted gel burning procedure. The phase characterization was performed by powder X-ray diffraction (XRD). All the compositions were well crystalized in monoclinic lattice. The FE-SEM images and elemental mapping were obtained. The infrared and Raman profiles of all-compounds were dominated by the bands owing to the (PO4) units. Investigation on photoluminescence emission and excitation spectra of Ln(3+) (Ln = Eu, Tb) were carried out. The excitation spectra of Na(3-3x)Ln(x)Fe(2)(PO4)(3) (Ln = Eu and Tb) gave intensive band at 256 (370) nm for Eu (Tb) doped phosphors. The photoluminescence emission spectra of Ln(3+) (Ln = Eu, Tb) were carried out. The emission spectra of these composition were characterized by f -f transitions corresponding to 613 (D-5(0)-> F-7(2)) for Eu and 543 (D-5(4)-> F-7(5)) for Tb doped compositions. The maximum emission intensity for Eu (Tb) doped phosphors was found at x = 0.075 (0.05). The analysis of CIE and CCT values of all prepared phosphors were also carried out. Decay curves were analyzed in detail. The visible-light photo-catalytic activity of parent Na3Fe2(PO4)(3) was examined against decomposition of methylene blue and methyl orange dyes. Parent Na3Fe2(PO4)(3) exhibits good efficiency against MB (approximate to 94.5 %) and moderate efficiency against MO (approximate to 64 %) in 180 min of visible light irradiation. Scavengers' experiments were carried to identify the active species during photodegradation.