LOW-FREQUENCY INTERNAL-FRICTION STUDY FOR SRBI2TA2O9 FERROELECTRIC CERAMICS

Low-frequency internal friction (IF) of SrBi2Ta2O9(SBT) ceramics has b een measured at temperatures ranging from 293 to 623 K. Two IF peaks, with their locations around 393 K (P1) and 569 K (P2) (f approximate t o 1.58 Hz), respectively, are observed. P1 is found to be associated w ith a relaxation process with activation energy of 0.97 eV and pre-exp onential factor of 3.58 x 10(-14) s. Peak shape analyses reveal that P 1 can be well described by a broadened Debye peak with the width param eter beta from 2.70 to 2.92. The mechanism responsible for P1 is propo sed to be relaxation of oxygen vacancies near domain walls(DWs). P2 is considered to arise from viscous motion of DWs since it shows charact eristics of static hysteresis type. Comparisons for the IF behavior be tween SBT and Pb(Zr, Ti)O-3(PZT) suggest that in SBT oxygen vacancies are much less localized near DWs than that in PZT. This result provide s a possible explanation for the weak DW pinning due to oxygen vacanci es in SBT.