SYNTHESIS OF HEXAGONAL POTASSIUM TUNGSTEN BRONZE FROM POLYOXOTUNGSTATES PRECURSOR BY A LARGE-SCALE GAS ROUTE

Zhao Hongtao (P. R. China) and Zhang Lifang (P. R. China)

Received January 18, 2008

Abstract

Hexagonal tungsten bronze was prepared by high temperature gaseous permeation method from polyoxometalates precursor This work demonstrates the feasibility of gas permeation synthesis in large scale. The batch size was 10L, and the holding time was two hours. XRD, TG-DTA, XPS and AC impedance spectra were used to characterize the resulting material. The crystal structure parameters of were obtained by the analysis of XRD, which are crystal system: Hexagonal, lattice parameter: The XPS results confirmed the presence of the mixed valence state of tungsten. The high temperature electrical properties were studied by AC impedance spectra. Although the sample exhibits the semiconductive behavior, curves are not linear and it obeys the small polaron hopping mechanism.

Keywords and phrases: tungsten bronzes, high temperature, gaseous permeation, polyoxometalates.