Mechanical and dielectric investigation on point defects and phase transition in ferroelectric ceramics

Mechanical and dielectric measurements were used to investigate the behavior of point defects and phase transition in ferroelectric ceramics. Some interesting results were obtained: (1) the dielectric loss peak in La-doped Bi4Ti3O12 was explained by the hopping of oxygen vacancies, the optimum doping content of La = 0.75 (Bi3.25La0.75Ti3O12) was discussed in terms of the competition between the density of oxygen vacancies and activation energies; (2) by use of internal friction measurements, the interaction between oxygen vacancies and ferroelectric domain walls was detected, the relationship between domain wall morphology and fatigue behavior was then well explained; (3) some internal friction peaks were also detected in SrBi2Ta2O9 and Pr(Zr0.52Ti0.48)O3 ceramics. The results mentioned above indicate that both mechanical and dielectric techniques are useful to clarify the mechanisms of ferroelectric behavior.