Dipole ordering or disordering in selected perovskite ferroelectric systems

The field induced relaxor to ferroelectric phase transition behavior was examined in a (111) oriented 24% PT PMN-PT single crystal. Upon field cooling, ferroelectric order is established by the application of an electrical field. Through dielectric measurements performed while heating and cooling with various applied DC fields, the temperature-electric field phase diagram was determined and compared to that developed for a (111) oriented PMN single crystal. The threshold field required to induce the ferroelectric phase in these PMN-PT crystals is much smaller than in pure PMN crystals, if not absent. Since the PMN-PT is nearer the morphotropic phase boundary, at ∼35% PT, the energy difference between the induced ferroelectric and relaxor phases is assumed to be smaller leading to the decreased threshold voltage.; The dielectric behavior of PLZST ceramics of several compositions, over a wide temperature range, with and without applied DC field was also explored. The application of an electrical field during field cooling or during P-E measurements can break the antiferroelectric order in favor of ferroelectric order. The dielectric properties of the anti ferroelectric phase and an induced ferroelectric phase were explored. The P-E behavior was also measured to examine the antiferroelectric behavior. Through the use of single pulse P-E measurements and, more importantly, selected area electron diffraction, PLZST compositions thought to be ferroelectric were shown to have an antiferroelectric ground state. An induced ferroelectric phase is easily produced in these ceramics leading to the mistaken classification.; The microstructural and electrical properties of several compositions of BSZT bulk ceramics were studied. The ceramics were found to be single phase cubic perovskites at room temperature. The substitution of zirconium for titanium in Ba0.7Sr0.3TiO3 in bulk ceramic form increases the disorder in the system gradually changing the electrical behavior from a normal ferroelectric to a strongly relaxor system. These transitions were examined using Curie-Weiss and Vogel-Fulcher fitting.