Defect engineering for properties control in SrBi₂Ta₂O₉ ferroelectrics

Abstract

Defect engineering to design for remanent polarization (Pr) and coercive field (Ec) in SrBi₂Ta₂O₉ (SBT) is proposed. Cation vacancies coupled with substituents or oxide vacancies are shown to play an essential role in the polarization properties. High-resolution neutron powder diffraction revealed that trivalent-cation (Bi, La, and Nd) substitution induces Sr vacancies for the requirement of charge neutrality. La substitution with Sr vacancies increased Pr slightly, but the 2Ec value (41 kV/cm) of La-SBT was much smaller than that in SBT (57 kV/cm). Nd-SBT showed almost the same Pr of La-SBT, while the very high 2Ec (125 kV/cm) was attained for Nd-SBT.