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

CaWO4 and Ca0.72La0.28WO4 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 La3+ doping, which induced to the presence of mixed valence states of W5+ and W6+ in scheelite-type structure compound. Hence, blue shift of UV–vis absorption from 350nm to 405nm was observed in La3+-doped calcium tungstate. •Large size cation of La3+ doped CaWO4 was prepared with sodium borohydride rolling the play of reducing agent.•The W in Ca0.7La0.3WO4 showed mixed valence of W5+ and W6+.•The round sphere shape of the samples was in agreement to nanoparticles.•Ca0.7La0.3WO4 showed a blue shift in the UV–vis absorption spectroscopy data compared to the CaWO4 matrix.