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The main objective of this study is to compare high-temperature relaxor ferroelectrics based on ternary solid solutions with the complex lead perovskite relaxor ferroelectric compounds and solid solutions is conducted. It is found that these parameters, energy and freezing temperature have a systematic scaling within the pervoskite relaxor systems that could lead to a generalized pattern and further investigation can give insights into the nature of the relaxor dynamic behavior.

The complex solid solution (1-x)Bi(Mg(sub 3/4)W(1/4)O(sub 3)-xPbTiO(sub 3) [(1-x)BMW-xPT] was investigated by building the ferroelectric family based on the Bi[Mg(super +3)O(sub 3)-PbTiO3 solid solutions. The phases and basic dielectric properties in a (1-x)Bi(Me'Me')O(sub 3)-xPbTiO(sub 3) system and preliminary structural phenomena are reported.

(1-x)Bi(Mg[sub 1/2]Ti[sub 1/2])O[sub 3]–xPbTiO[sub 3] polycrystalline ceramics were investigated for potential as high-temperature piezoelectric materials. A morphotropic phase boundary (MPB) between tetragonal (T) and rhombohedral (R) ferroelectric (FE) phases, which exhibited enhanced piezoelectric activity and a ferroelectric–paraelectric phase transition at 478 °C was observed at x≈0.37. Electron diffraction patterns (x<=0.37) contained discrete superlattice reflections at 1/2{hkl} positions arising from antiphase rotations of the O octahedra, consistent with R3c space group symmetry. These reflections were diffuse at the MPB (x=0.38) and absent in the T phase (x=0.5). In the unpoled state, FE R (x=0.35) ceramics revealed a polar microdomain structure whereas the T phase (x=0.5) contained classic {110} twin domain boundaries. However, poled R samples underwent a field-induced transformation to an aligned domain structure with {110} twin boundaries similar to those in the T phase. Correlations are made between structure and properties for these piezoelectric materials. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Barium titanate (BT) and montmorillonite (MMT) nanoparticle are covalently-bonded by organically modifying the particle surfaces and by chemically reacting them in solution. The thermodynamic properties of the glass transition process, the macroscopic mechanical properties of the nanocomposites and the dynamics of the polymer segments at the inorganic interfaces have shown that the filler configuration has increased the polymer-ceramic interfaces.

Epoxy resin composites based on organically modified montmorillonite (oMMT) or barium titanate (BT) (BaTi[O.sub.3]) nanoparticles are examined in order to delineate the effects of the high aspect ratio of the MMT and the high permittivity of the BT particles. The effect of the decreased glass transition, interfacial area, polymer-phase at the organic-inorganic interface and of the dielectric breakdown on the electrical energy storage capabilities of these composites is examined.

Highly accelerated lifetime tests (HALTs), thermally stimulated depolarization current (TSDC), and impedance spectroscopy (IS) measurements are performed on 0.7 Pb([Mg.sub.1/3][Nb.sub.2/3])[O.sub.3]-0.3 PbTi[O.sub.3] (PMN-PT) single crystal in order to examine time dependent dc resistance degradation under a dc bias. The activation energy about 0.6 eV is attributed to the migration of oxygen vacancies in this lead-based single crystal.

A study is conducted to examine the temperature dependence of the electrical leakage current density of chemical solution deposited BaTi[O.sub.3] films on high purity Ni foils as a function of the underlying Ni microstructure. The results showed that the reverse biased Schottky barrier at the cathode which dominates the conductivity enhances the resistance across the interface and hence higher voltages could be applied before the losses become significant.

The effect of spatial distribution of the fillers on the electrical properties of polymer ceramic composites is studied with special emphasis on the high-field behavior and the recoverable energy storage. The results have shown that engineered anisotropy is used to control dielectric breakdown strengths and nonlinear conduction at high fields in heterogeneous systems.

Polymer/ceramic composites with controlled spatial distribution of fillers are prepared and the corresponding changes in their properties are analyzed. The increased values of permittivities in structured composites have provided a platform for obtaining high energy density materials and the anisotropy in permittivity and conductivity is used for designing composites with desired properties.

A measurement and analysis technique is developed to quantify the complex contributions to the nonlinear dielectric and converse piezoelectric response in ferroelectric ceramics. The results have indicated that the same loss mechanism dominates the nonlinear portion of both the dielectric and piezoelectric responses in piezoelectric ceramics.

The ferroelectric transition temperature (T(sub c)) behavior of perovskite solid solutions based on PbTiO3-Bi(Me'Me')O3 (Me'=Fe(super 3+), Zn(super 2+), Sc(super 3+), In(super 3+), Mg(super 2+), Ni(super 2+), and Me'=Ti(super4+), Nb(super 5+), W(super 6+) is considered. It is proposed that the observations are consistent with random-field effects created by local strain-field fluctuations within the perovskite lattice.

The microchemical and microstructural origins of insulation-resistance degradation in BaTiO3-based capacitors are studied by complementary impedance spectroscopy and analytical transmission electron microscopy. The degradation under dc-field bias involves electro migration and accumulation of oxygen vacancies at interfaces.

Impedance spectroscopy, transmission electron microscopy, and electron energy-loss spectroscopy are used to correlate local electrical properties with the microstructure and microchemistry of BaTiO3 in Ni-electrode multilayer ceramic capacitors. High densities of linear defects and some grains with structural modifications are observed in BaTiO3 grains in the as-confirmed capacitors.

The perovskite system exhibits a large piezoelectric coefficient and a high Curie temperature in the vicinity of the morphotropic phase boundary. The present contribution reports on revisions to the BiScO3-PbTiO3 phase diagram.

The structure-property relations in a high temperature piezoelectric system, (1-x) Bi (Mg (sub 1/2) Ti sub 1/2) O (sub 3) -xPbTiO (sub 3) (BMT-PT) have been interpreted and a comparison has been made with other piezoelectric, perovskite solid-solution systems. The FE R phase exhibited superlattice reflections, which was consistent with R3c symmetry at room temperature, which existed upto the MPB.

Transmission electron microscopy and electron energy loss spectroscopy are used to investigate structural defects during the degradation of high performance multilayer Ni-BaTiO3 X7R ceramic capacitors. Intentionally electrically degraded devices show a coexistence of regular, modulated and long-range ordered structures.

A perovskite solid-solution ((1-x)BiScO3-(x)PbTiO3) with superior electromechanical properties than PbZrO3-PbTiO3 (PZT) ceramics is discovered. Transmission electron microscopy is used to study changes in domain structure and symmetry as a function of x. From the results, the low temperature phase diagram for BiScO3-PbTiO3 has been modified.