Search

A ternary solid solution (1 − x)(0.88 Bi0.5 Na0.5 TiO3-0.12 BaTiO3)- x Bi( Zn0.5 Ti0.5) O3 ( BNBZT, BNBZT x) was designed and fabricated using the traditional solid-state reaction method. The temperature and composition dependence of dielectric, ferroelectric, piezoelectric, and fatigue properties were systematically investigated and a schematic phase diagram was proposed. The substitution with Bi( Zn0.5 Ti0.5) O3 was found to shift the phase transition (ferroelectric tetragonal to relaxor pseudocubic phase) to lower temperatures. At a critical composition x of 0.05, large electric-field-induced strain response with normalized strain Smax /Emax as high as 526 pm/V was obtained under a moderate field of 4 kV/mm around room temperature. The strain exhibited good temperature stability within the temperature range of 25°C-120°C. In addition, excellent fatigue-resistant behavior was observed in the proposed BNBZT solid solution after 106 bipolar cycles. These give the BNBZT system great potential as environmental friendly solid-state actuator. [ABSTRACT FROM AUTHOR]

Ferroelectric material possesses a high dielectric constant during ferroelectric to paraelectric phase transition. But, the high dielectric constant exhibits only within a very small temperature window because the phase transition region is narrow. Functionally graded material is suggested to enlarge the phase transition region. Here, both functionally graded ferroelectric ceramics lead titanate zirconate(PZT) and PZT with single composition are prepared. Dielectric property in two systems is measured and compared each other. Functionally graded ceramics PZT possesses a relatively high dielectric constant within a large temperature range. It is due to the FGM PZT has a wide phase transformation temperature region. [ABSTRACT FROM AUTHOR]

We report that aging in ferroelectric state results in an increase of reverse transition temperature Tf in both BaTiO3 single crystal and Pb0.84La0.16Ti0.96O3 polycrystal. This indicates that the ferroelectric phase is gradually stabilized during aging below Curie temperature. The evolution of the stabilization with aging time in these two different systems obeys the same kinetic function, but with different relaxation time. This indicates that the stabilization effect of the two systems stems from a common origin. We suggest that the stabilization is due to a short-range ordering of point defects, driven by a symmetry-conforming tendency of point defects. [ABSTRACT FROM AUTHOR]

0.67Pb(Mg1/3Nb2/3)O3 (PMN)–0.33PbTiO3 (PT) ferroelectric ceramics has been selected as base component. Different content of B-site substitute (0.1, 0.5 and 1 mol%) were used to modify the base component. The specimens were synthesized by the columbite precursor method, and pure perovskite phase were obtained for all the specimens. The dielectric behavior was examined to investigate the relaxor behavior of each component. It is found that the specimen undoped and modified with 0.1 mol% WO3 nearly behave as normal ferroelectric ceramics, while with the content of WO3 increasing, the degree of relaxor behavior for the composition increases. Thus, B-site substitute WO3 has a strong effect of inducing relaxor behavior of PMN–PT ferroelectric ceramics near morphotropic phase boundary (MPB). [Copyright &y& Elsevier]

Abstract: The dielectric, ferroelectric, and electrical insulating properties of Pb(Mg1/3Nb2/3)0.62Ti0.38O3 thin film and Pb(Mg1/3Nb2/3)0.62Ti0.38O3–PbZr0.53Ti0.47O3 (PMNT–PZT) multilayer thin films including PMNT/PZT, PZT/PMNT and PZT/PMNT/PZT prepared on LaNiO3/SiO2/Si substrates were investigated. It is found that the PMNT based multilayer films show larger dielectric constant and lower dielectric loss compared with the monolayer PMNT film. Moreover, the multilayer thin films exhibit little temperature dependence of dielectric properties over a broad temperature range from 30 to 270°C. In addition, well saturated polarization-versus-electric field hysteresis loops with large spontaneous polarization of 22.2–23.9μC/cm2 for the multilayer films are obtained due to their good electrical insulating properties. The leakage current densities in the multilayer films are about three orders of magnitude lower than those in the monolayer PMNT thin film under electric field E >70kV/cm. We argue that the reduction of the leakage current densities is mainly attributed to the formation of a depletion zone/layer between layers by incorporating layers of PZT in multilayer structures acting as a potential barrier for free carriers to transport as well as carrier scattering at interfaces supported by the measurements on dielectric and electrical insulating properties. The results demonstrate that the multilayered thin films exhibit enhanced dielectric, ferroelectric and electrical insulating properties for ferroelectric memory devices. [Copyright &y& Elsevier]

Abstract: 0.62Pb(Mg1/3Nb2/3)O3–0.38PbTiO3 (0.62PMN–0.38PT) thin films were deposited on La0.6Sr0.4CoO3 (LSCO) buffered Si substrates by radio-frequency magnetron sputtering. It has been found that the 0.62PMN–0.38PT films show a (100) preferred oriented perovskite phase on (100) preferred oriented LSCO layer while they show a (110) preferred perovskite phase on (110) preferred oriented LSCO layer. The formations of such preferred orientations are attributed to co-contribution of the surface energy and lattice-match interface energy. The (110) preferred oriented 0.62PMN–0.38PT film exhibits a relatively low remnant polarization of 12.1μC/cm2 while a low coercive field of 27kV/cm compared with (100) preferred oriented one (13.9μC/cm2, 56kV/cm). Moreover, the (110) preferred oriented film shows a larger dielectric constant of ∼2260 and a lower dielectric loss of 0.09 at 1kHz than those of (100) preferred oriented one (1050 and 0.19). The results demonstrate that the enhanced ferroelectric and dielectric properties are achieved for (110) preferred oriented film, which is correlated with large anisotropy in the texture films induced by LSCO buffer layers. [Copyright &y& Elsevier]