Anomalous properties of A m−1Bi2B m O3m+3 layered ferroelectrics

Statistical analysis is presented of the literature data on the properties of A m−1Bi2B m O3m+3 layered ferroelectrics consisting of alternating perovskite-like slabs and bismuth-oxygen layers. The results reveal new and confirm some of the known tendencies. The Bi-O layers are shown to tighten the structure of these compounds, and the effect becomes stronger with decreasing slab thickness. As the distortion of the pseudoperovskite cells in the perovskite-like slabs increases, the Curie temperature T C passes through a maximum. Its position depends on the slab thickness (m). Thus, at strong lattice distortions, T C decreases with increasing distortion, in conflict with the Abrahams-Kurtz-Jamieson relation. The observed anomalies are tentatively attributed to changes in the nature of ion displacements.