Sol–gel synthesis and photoluminescence analysis of Sm 3+ :NaGd(WO 4 ) 2 phosphors

Sm3+:NaGd(WO4)2 sub-micron phosphors were synthesized by a sol–gel method. The tetragonal crystalline structure was observed from X-ray diffraction analysis and the crystallite size was calculated by Williamson–Hall approximation. Raman results elucidate the presence of phonon vibrations corresponding to tungstate tetrahedra and free metallic ions. The morphology and average grain size were obtained using scanning electron microscopy. Luminescence spectra reveal the emission peaks at 563nm (4G5/2→6H5/2), 600nm (4G5/2→6H7/2), 645nm (4G5/2→6H9/2) and 700nm (4G5/2→6H11/2) under the excitation wavelength of 406nm. The maximum emission intensity was observed for 3mol% of Sm3+ ions concentration in NaGd(WO4)2 phosphors. The temperature dependent luminescence and luminescence decay were measured. The CIE color co-ordinates of 3mol% Sm3+:NaGd(WO4)2 phosphors were calculated as (0.558, 0.416).