Collective domain-wall pinning of oxygen vacancies in bismuth titanate ceramics

摘要

Pure Bi_4Ti_3O_(12) ceramics were prepared using the conventional solid-state reaction method. In order to find the relationship between the ferroelectric properties and oxygen vacancies, we changed the concentration of oxygen vacancies inside the ceramics through different processes of oxygen treatment. Ferroelectric measurement reveals that both remnant polarization and fatigue resistance increase with the decreasing oxygen vacancies concentration. On the plot of dielectric loss as a function of temperature, a peak with the relaxation-type characteristic was observed at about 370 K with 100-Hz measuring frequency. This peak was associated with the migration of oxygen vacancies inside the ceramics and was well fitted using the Cole-Cole relation. The obtained broaden factor was found to be less than 1.0, which indicates that there was a strong correlation among those relaxation units. Therefore, in the domain-wall pinning fatigue mechanism, the migration of oxygen vacancies would demonstrate a collective behavior instead of an individual one. These results were further confirmed in Nd-modified Bi_4Ti_3O_(12) ceramics.