Effect of excess Bi2O3 on the ferroelectric properties of SrBi2Ta2O9 ceramics

In this study, the effect of bismuth content on phase-transition behavior, ferroelectric property, and crystal structure of strontium–bismuth–tantalate (SBT) ceramics was explored with the aid of εr(T), ferroelectric hysteresis loop, x-ray diffraction (XRD), and Raman spectroscopy. Both the phase-transition behavior and ferroelectric properties such as spontaneous polarization (Ps) showed a dependence on Bi content. The ferroelectric Curie temperature Tc, was found to decrease with increasing the Bi content and Ps was maximized when 2–3 mol % excess Bi2O3 was added. It was found that Raman spectroscopy and XRD can explain the Bi-content dependence of SBT ceramics. The frequency and the width of the mode below 60 cm−1 in Raman spectra revealed that a site exchange of Sr2+ and Bi3+ ions occurred. The formation of antisite defects was confirmed by the change in the intensity ratio of I(008)/I(105) in the XRD patterns. The calculation of structure factors showed it was also related to antisite defects (SrBi,BiSr).