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-tantalat e (SBT) ceramics was explored with the aid of epsilon(r)(T), ferroelectric hysteresis loop, x-ray diffraction (XRD), and Raman spectroscopy. Both the phase-transition behavior and ferroelectric properties such as spontaneous polarization (P-s) showed a dependence on Bi content. The ferroelectric Cur ie temperature T-c, was found to decrease with increasing the Bi content an d P-s was maximized when 2-3 mol % excess Bi2O3 was added. It was found tha t Raman spectroscopy and XRD can explain the Bi-content dependence of SBT c eramics. The frequency and the width of the mode below 60 cm(-1) in Raman s pectra revealed that a site exchange of Sr2+ and Bi3+ ions occurred. The fo rmation of antisite defects was confirmed by the change in the intensity ra tio of I(008)/I(105) in the XRD patterns. The calculation of structure fact ors showed it was also related to antisite defects (Sr-Bi,Bi-Sr). (C) 2000 American Institute of Physics. [S0021-8979(00)03813-5].