COOPERATIVE INTERACTION OF OXYGEN OCTAHEDRA FOR DIELECTRIC-PROPERTIESIN THE FERRO-PARAELECTRIC COMPOSITES

In the PbZn1/3Nb2/3O3 relaxer system, A-site modified ferroelectric pe rovskite Pb0.7Ba0.3 Zn1/3Nb2/3O3 phase which was substituted with 0.3 mol of Ba to Pb site and paraelectric pyrochlore Pb1.83Zn0.29Nb1.71O6. 39 phase were prepared and the composites with the perovskite and pyro chlore phase were synthesized. The dielectric properties with respect to the volume percent of the phase were examined. The percolation limi t where ferroelectric perovskite phase is isolated by paraelectric pyr ochlore phase was 29.6 vol%. However, a dielectric anomaly was observe d below the percolation limit, which is believed to be caused by a fac tor that can propagate any ferroelectric lattice vibration mode from t he isolated ferroelectric perovskite phase to paraelectric pyrochlore matrix. 3-dimensional connection of oxygen octahedron by its corner sh aring seems to play an important role for the cooperative dielectric i nteraction that contributes to the dielectric anomaly. Furthermore, hi ghly polarizable Pb2+ ions in the composite help the propagation effic iency.