Investigation of structural and optical characteristics of CaWO4 and BaWO4 nanoparticles

Structural and optical studies of calcium tungstate and barium tungstate nanoparticles prepared by precipitation method are presented. Lattice parameters and atomic position coordinates in tungstate samples were determined by Rietveld refinement of angle dispersive x-ray diffraction (ADXRD) data using FullProf software. The average crystallite size and lattice strain were calculated by Williamson-Hall (W-H) method. Raman spectra show sharp W-O vibration modes, characteristics of tetragonal tungstate samples. The effect of larger ionic radius of Ba2+ than Ca2+ was seen in the larger lattice parameters and crystallite size, and hence sharper Raman modes of BaWO4 sample than CaWO4. Photo-luminescence (PL) spectroscopy shows bluish and greenish light emission in both the samples, which corresponds to the transitions in WO42− and oxygen vacant WO3 complexes respectively.