Abstract
Crystal structures and ferroelectric properties of a series of Bi-layered compounds, and were investigated. The structures of and are orthorhombic, while that of is pseudotetragonal on the macroscopic scale but consists of microdomains with orthorhombic distortion. The ferroelectric Curie temperature of was over 600 °C, and that of was over 300 °C. in contrast, showed relaxor-type ferroelectric behavior; that is, in the plot of temperature dependence of dielectric constant, a broad peak appeared around 60 °C. As the size of the A-site cation decreases from to the lattice mismatch between and planes in the perovskite-type unit of increases and the structural distortion becomes more pronounced. This distortion leads to the higher Curie temperature and the larger spontaneous ferroelectric polarization.
- Received 28 July 1999
DOI:https://doi.org/10.1103/PhysRevB.61.6559
©2000 American Physical Society