Influence of structure ordering, defects and external conditions on properties of ferroelectric perovskites

Results of comprehensive studies of the (A'A")(B'B")O-3-ferroelectric perovskites are reported. Examined compositions include Pb1-xLax(Zr0.65Ti0.35)(1-x/4)O-3 (PLZT), PbSc0.5Nb0.5O3 (PSN), PbSc0.5Ta0.5O3 (PST), and PMNT, PSNT and PLuNT pseudo-binary systems exhibiting pronounced dielectric, electrooptical, and electromechanical properties. Degree of ordering in the materials has been varied by chemical composition (modification, isomorphic ion substitution), by variation of technology (hot-pressing, specific thermal treatment, thin films), and by irradiation of different kind and intensity (gamma -rays, electrons, neutrons). Broadening of the phase transition, dielectric dispersion and magnitude of field induced effects in PST and PSN ceramics are found to be affected by long-range order parameter and deficiency of PbO. The impacts of radiation induced defects on optical and dielectric properties have been studied in PLZT compositions. A defect stimulated phase transformation being observed in neutron irradiated PLZT 6.5-8.5/65/35 ceramics. The crystallographic features at the morphotropic phase boundary are discussed with respect to electromechanical properties of the original binary PLuNT system ceramics. In ferroelectric thin films (PLZT, PMNT, PSNT, PLuNT) relaxer properties and broadening of PT are found to be more pronounced compared to ceramics their physical characteristics (including field induced deformation) being strongly dependent on the microstructure and interfaces of the films.