Preparation and physical properties of Cu _xWO _3

摘要

We report on the study of WO _3 doped with Cu using solgel (Cu _xWO _3 ~d) and impregnation (Cu _xWO _3 ~i) methods. All materials are well crystallized and exhibit single phases whose crystallite size ranges from 17 to 100 nm depending on Cu amount and the preparation technique. The conductivity dependence on temperature demonstrates semiconductor behavior and follows the Arrhenius model, with activation energies, E _σ, commonly in the range 0.40.6 eV. Moreover, the thermopower study shows that Cu _xWO _3 ~d is mainly of p-type conductivity, whereas Cu _xWO _3 ~i is n-type. The mechanism of conduction is attributed to a small polaron hopping. The doping process is found to decrease the interband transition down to 520 nm depending on the preparation conditions. The photoelectrochemical characterization confirms the conductivity type and demonstrates that the photocurrent J _(ph) increases with Cu-doping. Taking into consideration the activation energy, the flat band potential and the band gap energy, the band positions of each material are proposed according to the preparation method and Cu amount.