No CrossRef data available.
Published online by Cambridge University Press: 01 February 2011
Defect engineering is shown to be an effective to design for remanent polarization (Pr) and coercive field (Ec) in SrBi2Ta2O9 (SBT). Cation vacancies and oxygen vacancies are shown to play an essential role in the polarization properties. The ceramic samples were prepared by a solid-state reaction, and high-density ceramics (over 95% of the theoretical density) were used for the measurements of polarization and dielectric properties. High-resolution neutron powder diffraction revealed that trivalent-cation (Bi, rare-earth elements [RE=La, Ce, Pr, Nd, Sm]) substitution induces Sr vacancies in the perovskite blocks for the requirement of charge neutrality. The substitution of La with Sr vacancies (La0.33Sr0.5Bi2Ta2O9) increased 2Pr from 13 μC/cm2 (SBT) to 16 μC/cm2, and the 2Ec value (41 kV/cm) was much smaller than that of SBT (57 kV/cm). Nd-substituted SBT showed the same Pr of La-SBT, while 2Ec (140 kV/cm) of Nd-SBT (x=0.5) was much higher than that of La-SBT. The higher Ec found for Nd-SBT is attributed to partial Nd substitution at the Ta site with the creation of oxygen vacancies. The control of Ec for RE-SBT is discussed in terms of Sr vacancies and oxygen vacancies.