Bi2WO6 Lead-free Ferroelectrics: Microstructure Design, Polar behavior and Photovoltaic Performance

Bi2WO6 (BWO) is a promising ferroelectric material because of its high Curie temperatures and environmentally benign nature. However, the mica-like grains growth habit and large leakage current make it difficult to obtain excellent polar properties when preparing BWO bulk materials by conventional route. Here, through the precursor morphology control, combined with spark plasma sintering (SPS), we prepared for the first time BWO ceramics with different microstructure: randomly oriented polyhedron grains (R-BWO) and highly aligned plate-like grains (T-BWO). Excellent polar properties are successfully obtained in both kinds of BWO ceramics. In particular, T-BWO ceramic exhibits a large remnant polarization (Pr) of ~23.6 μC/cm2 and a piezoelectric coefficient (d33) of ~18.2 pC/N, almost twice that of the R-BWO ceramics. Moreover, bulk photovoltaic effect investigations indicate that the photovoltaic properties can be modulated through microstructure design, specifically, the T-BWO has a short circuit photocurrent of ~-1.50 nA, which is almost four times of that of the R-BWO. The underlying mechanisms are further demonstrated by crystal structure and microstructure analysis. This study provides a simple and feasible microstructure engineering approach to manipulate not only the ferroelectricity but also photovoltaic properties of layer-structured materials.