Ferroelectric properties of Sr1-xBi2+xTa2O9 dense ceramics

Ferroelectric properties of dense ceramics of Sr-deficient and Bi-excess strontium bismuth tantalate, Sr_1-xBi_2+xTa₂O₉, were investigated, and their crystal structures were analyzed through the powder X-ray diffraction Rietveld method. A successful pattern fitting was obtained under the assumption that Bi was substituted at the Sr site for samples with x⩽0.16, and the lattice length in the a-b plane was reduced linearly with an increase in x. Dielectric measurements revealed that the Curie temperature (T_C) rose with x and that the sample with x=0.27 had a T_C of 430°C which was much higher than that of the stoichiometric sample (x=0:T_C=300 °C). These results strongly support the Bi substitution at the Sr site. The polarization hysteresis measurements revealed that a small amount of Bi substitution of 5% results in a marked increase in remanent polarization, however that further Bi substitution is not effective for improving the ferroelectric properties