Structure, ferroelectric and dielectric properties of Bi₂WO₆ with different bismuth content

This paper reports that the Bi₂WO₆ ferroelectric ceramics with excess Bi₂O₃ of 0.0, 2.0, 3.5 and 5.0wt.% of the stoichiometric composition are prepared by the conventional solid-state reaction method. Their microstructure, ferroelectric properties, the concentration and mobility of the defects have been analysed systematically. With increasing Bi content, the remnant polarization decreases, and the broken-down voltage increases. The optimum Bi excess, 3.5, lowers the oxygen vacancy concentration, while further Bi-addition brings about more defects. The activation energies fitted from cole-cole plots are 0.97eV, 1.07eV, 1.18eV, and 1.33eV, respectively. This suggests that the mobility of the defects is weakened by Bi-addition, which may be due to the increase of the ratio of the number of Bi₂O₂ layers to that of the perovskite blocks.