Preparation, sintering, and ferroelectric properties of layer-structured strontium bismuth titanium oxide ceramics

The preparation and ferroelectric properties of layer-structured SrBi4Ti4O15 ceramics were investigated in this study. During the solid-state reaction, the formation of SrBi4Ti4O15 started at 700 °C, and the pure layered structure was completely formed at 900 °C. The obtained SrBi4Ti4O15 powder was found to be hardly sintered at low temperatures. Raising the sintering temperature higher than 1100 °C led to an increase in the density of SrBi4Ti4O15 ceramics; however, a secondary phase having a pyrochlore structure was also produced on the surface of the ceramics due to the thermal decomposition reaction. This thermal decomposition was caused by the vaporization of bismuth species outward from the SrBi4Ti4O15 ceramics at elevated temperatures. In order to suppress the decomposition reaction, a process of covering SrBi4Ti4O15 compacts on the sintered ceramics was developed. This process successfully resulted in highly densified SrBi4Ti4O15 ceramics having the pure layer-structured phase. These well-sintered SrBi4Ti4O15 ceramics exhibited good ferroelectric properties with high remnant polarization (2Pr=13.52 μC/cm2) and low coercive field (2Ec=52.31 kV/cm).