Sol-gel synthesis and photoluminescence analysis of Sm3+:NaGd(WO4)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 563 nm (4G5/2→6H5/2), 600 nm (4G5/2→6H7/2), 645 nm (4G5/2→6H9/2) and 700 nm (4G5/2→6H11/2) under the excitation wavelength of 406 nm. The maximum emission intensity was observed for 3 mol% of Sm3+ ions concentration in NaGd(WO4)2 phosphors. The temperature dependent luminescence and luminescence decay were measured. The CIE color co-ordinates of 3 mol% Sm3+:NaGd(WO4)2 phosphors were calculated as (0.558, 0.416).