Relaxor Ferroelectric Pmnt Ceramics Dynamic Scaling Of The Loop

The relaxor ferroelectric (1-x)Pb(Mg1/3Nb2/3)03-xPbTi03 (PMNT(1-x/x)) have excellent piezoelectric, electro-optic and pyroelectric properties, and have been widely investigated for their potential application of piezoelectric actuator, ultrasonic transducer, electro-optical devices and pyroelectric detector. Perovskite-type PMNT powders and ceramics were fabricated by using a modified sol-gel process. The effect of synthesis method, excess Pb and sintering process on the microstructures and properties of PMNT was investigated. The scaling behaviors of PMNT ceramics were further studied.Proper excess Pb favors the formation of perovskite phase in PMNT powders (5 mol%) and enhances the electrical properties of PMNT ceramics (2 mol%). Too much excess Pb (over 10 mol%) results in an increase of pyroelectric phase in PMNT powders, non-uniform microstructures and decayed electrical properties of PMNT ceramics. The microstructures and electrical properties of the PMNT ceramics were improved remarkably by using oxygen atmosphere annealing. The intrinsic hysteresis loops of the PMNT ceramics were measured by using an improved PUND method with five pulses.The scaling behaviors of the PMNT(67/33) ceramics show that the character time re of the domain reversal in PMNT(67/33) ceramics decreased with increasing electric field amplitude E0 at low E0, while it is a constant of 0.0056 s at high E0. Compared with other ferroelectric systems, the domain reversal in PMNT(67/33) ceramics is much more sensitive to E0 at low E0, and responses faster to the electric filed frequency f at high E0. The dependence of the domain reversal on the E0 and f enhanced with increasing temperature in the PMNT(67/33) ceramics. With increasing PbTiO3 (x<0.35), the dependence of domain reversal on the f decreased, while the dependence on the E0 and re increased.Besides, the microstructures of epitaxial perovksite-type films were investigated by using transmission electron microscopy. In the La0.7Ca0.3MnO3/YBa2Cu3O7 (YBCO/LCMO) bi-layers, the LCMO layer shows columnar grain growth with mixed domains of [100]c, [010]c and [001]c oriented. The YBCO layer is nearly c-axis oriented but the lattices tilt by-2.5°to +2.5°. In case of LCMO/YBCO bi-layers, the initial 12-nm thickness of the YBCO layer consists of c-axis oriented domains and the upper part of YBCO layer grew along a-axis. The LCMO layer was predominantly [001]c oriented. Three types of dissociated misfit dislocations (MDs) in Ba0.3Sr0.7TiO3 thin films were observed, and each of the dissociated MDs consists of two or three partials dislocations accompanied with (1/2)<110> stacking faults.