UV–vis absorption shift of mixed valance state tungstate oxide: Ca0.72La0.28WO4

Abstract CaWO 4 and Ca 0.72 La 0.28 WO 4 samples were synthesized via mild hydrothermal method at 180 °C. Composition, phase purity, morphology and W element binding energy were characterized by induced couple plasma atomic emission spectrum (ICP-AES), powder x-ray diffraction (XRD), scanning electron microscopy (SEM), x-ray energy dispersive spectroscopy (EDS), and x-ray photoelectron spectroscopy (XPS). UV–vis absorption spectroscopy shows absorption peak shift due to La 3+ doping, which induced to the presence of mixed valence states of W 5+ and W 6+ in scheelite-type structure compound. Hence, blue shift of UV–vis absorption from 350 nm to 405 nm was observed in La 3+ -doped calcium tungstate.