Internal friction and Young's modulus of SrBi2Ta2O9 ceramics

The internal friction (IF) and the Young's modulus of SrBi2Ta2O9 (SBT) cera mics were measured by using the reed vibration method in the temperature ra nge from 100 to 600 K with kilo-hertz frequencies. A high IF peak associate d with a modulus defect appeared around 500 K, which was assumed to be due to the migration of oxygen vacancies with the activation energy U of about 0.95 eV. The mechanism of the IF peak was discussed in detail. At 570 K, an IF peak due to the viscous motion of domain walls near the Curie temperatu re was found. Below room temperature, a low IF peak with a modulus defect w as found with peak temperature of 200-250 K, which varied for tens of degre es in different samples. This peak was due to the depinning process of 90 d egrees domain walls from oxygen vacancies. These results can be helpful in explaining the excellent fatigue resistance property of SBT thin films at r oom temperature. (C) 2000 American Institute of Physics. [S0021-8979(00)034 03-4].