Oxygen-vacancy-induced 90°-domain clamping in ferroelectric Bi4Ti3O12 single crystals

We have investigated domain clamping in ferroelectric single crystals of Bi4Ti3O12 (BiT) and (Bi3.6La0.4)Ti3O12 (BLT) using polarization measurements along the a (b) axis and piezoresponse force microscopy (PFM). PFM observations reveal that 90 degrees domains are clamped during polarization switching. The crystals of BiT with less oxygen vacancies and BLT exhibited a low volume fraction of the clamped 90 degrees domains. Polarization measurements demonstrate that the clamping of 90 degrees domains decreases the remanent polarization in BiT crystals. These experimental results and ab initio calculations show that an attractive interaction between 90 degrees-domain walls and oxygen vacancies is the main origin of the clamping of 90 degrees domains.