Structure dependence of ferroelectric properties in single crystals of bismuth layer-structured ferroelectrics

Ferroelectric properties along the a- or b-axis in single crystals of various bismuth layer-structured ferroelectrics (BLSFs) were investigated. By measuring P-E hysteresis curves of BLSFs, values of the saturated remanent polarization and the coercive electric field were found to be related with the Curie temperature and the number of BO6 octahedra (m) between bismuth layers, respectively. The saturated remanent polarization was larger in the BLSF with a high Curie temperature. This is attributed to a large atomic displacement accompanied by a high Curie temperature. Tn contrast, the saturated coercive electric field was smaller in the BLSF with a large number of m. This phenomenon is assumed to be caused by the decrease in the strain energy of the octahedra from the bismuth layer, which leads to easy movement of the octahedral cations in the direction of an applied external electric field.