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The local piezoelectric properties of ferroelectric composites consisting of P(VDF-TrFE) copolymer matrix with barium lead zirconate titanate ceramic inclusions were addressed both experimentally using piezoresponse force microscopy technique and theoretically applying the Landau-Ginzburg-Devonshire formalism. A transient region with a width of approximately 40 nm has been found at the interface between the two constituents. It is shown that the piezoresponse in the vicinity of the interface is strongly affected by inhomogeneous stresses originating from an incompatibility of thermal expansion coefficients of PVDF and lead zirconate titanate. [ABSTRACT FROM AUTHOR]

BaTiO3 nanowires were grown in an amorphous aluminum oxide membrane from a sol-gel via electrophoresis. These had a ferroelectric coercive field of 5 kV/mm after undergoing a thermal treatment. This value is 12-16 times larger than the bulk value. Such enhancements are in agreement with local PFM measurements by others. An enhanced polarization of ≈80 μC/cm2 was also measured, where the bulk is around 26 μC/cm2. In addition, low leakage currents were also observed. [ABSTRACT FROM AUTHOR]

The evolution of the domain structure in lead zirconate titanate ceramics in the course of polarization fatigue is investigated by piezoresponse force microscopy. It is found that fatigue results in a strong modification of the domain structure. The domain patterns initially consisting of mainly 180° domains split into fine ferroelastic domains to relieve the mechanical stresses arising due to the continuous polarization switching. The observed distorted domain walls (or “wavy” domain patterns) are attributed to clamping by defect agglomerates. The biggest concentration of clamped domains is found in grains close to the electrode interface signifying that these are most damaged by fatigue. Furthermore, a preferred polarization orientation is observed near the electrodes. Postannealing of fatigued samples promotes the partial recovery of the initial domain structure. The results indicate the importance of nearby electrode grains in the polarization switching in polycrystalline materials. [ABSTRACT FROM AUTHOR]

The motion of a single planar 180° domain wall was studied in single-crystalline gadolinium molybdate, Gd2(MoO4)3. The switching current and the instantaneous wall positions were recorded using polarized light in an optical microscope and subsequent image processing. A pronounced deaging (wake-up) effect is observed represented by an increase of domain-wall shift during cyclic switching at constant voltage amplitude. The experimental data are compared to computer simulations taking into account the kinetic imprint effect under ac cycling. The latter is the change of the spatial distribution of the internal bias field during cycling. It is shown that deaging (wake-up) arises for aged (screened) initial states. After long enough cycling, the spatial distribution of the internal bias field becomes steady state and the wall motion becomes reproducible in all its details. The final distribution of the internal bias field does not depend on the initial state of the sample. The activation energies for deaging and aging are equal within the experimental uncertainty and thus very likely stem from the same micromechanism. [ABSTRACT FROM AUTHOR]

Recently, the progress of integrated electronics has led to a strong demand for materials and devices with multiple functions. In this study, we achieved Pb0.985Sm0.01 (Zr0.64Sn0.28Ti0.08)O3 ( PSZST) multifunctional ceramics which showed simultaneously large electric-field-induced strain (0.63%) and high recoverable energy density (1.743 J/cm3) at room temperature. Moreover, the strain and recoverable energy density exhibited a slight frequency fluctuation in the frequency range of 1-10 Hz. Their variations were less than 8% and 1.3% and the values were all higher than 0.58% and 1.722 J/cm3, respectively. The large strain, high-energy density, and their good frequency stability in a wide range indicate that the PSZST ceramic is quite promising for application in multifunctional devices. [ABSTRACT FROM AUTHOR]

Enhanced electrical resistivity about over two orders of magnitude for Na0.5Bi2.5Nb2O9 (NBNO) high-temperature piezoceramics potentially used in piezoelectric sensors is achieved by the introduction of highly insulating Al2O3 addition. Possible pyrochlore secondary phases of two types of grains: irregular polyhedral and platelike, forming at the grain boundaries, have significant blocking effect on the electric current paths and thus lead to improved electrical resistivity. Al2O3-modified NBNO ceramics show higher d33 values up to 16.5 pC/N than that of pure NBNO ceramics (12.4 pC/N) because higher electric field is applied during poling process owing to enhanced electrical resistivity, whereas the Tc values keep almost constant. A compromise between high Tc, good polarizability and enhanced electrical resistivity has been achieved by suitable addition of Al2O3, which would shed light on how to obtain novel Aurivillius phase ferroelectrics for practical applications at high temperature. [ABSTRACT FROM AUTHOR]

Microreactor systems are now used more and more for the continuous production of metal nanoparticles and metal oxide nanoparticles owing to the controllability of the particle size, an important property in many applications. Here, for the first time, we used microreactors to prepare metal oxide nanoparticles with controlled and varying metal stoichiometry. We prepared and characterised Zn-substituted Fe3O4 nanoparticles with linear increase of Zn content (ZnxFe3−xO4 with 0 ≤x≤ 0.48), which causes linear increases in properties such as the saturation magnetization, relative to pure Fe3O4. The methodology is simple and low cost and has great potential to be adapted to the targeted doping of a vast array of other inorganic materials, allowing greater control on the chemical stoichiometry for nanoparticles prepared in microreactors. [ABSTRACT FROM AUTHOR]

Ceramics of composition (1− x)BaTiO3- xBi(Zn1/2Ti1/2)O3 ( BT- BZT) were prepared by solid-state synthesis; they have been shown to exhibit excellent properties suited for high-temperature dielectric applications. The X-ray diffraction data showed a single-phase perovskite structure for all the compositions prepared ( x ≤ 0.1 BZT). The compositions with less than 0.075 BZT exhibited tetragonal symmetry at room temperature and pseudo-cubic symmetry above it. Most notably, a significant improvement in insulation properties was measured with the addition of BZT. Both low-field AC impedance and high-field direct DC measurements indicated an increase in resistivity of at least two orders of magnitude at 400°C with the addition of just 0.03 BZT (~107 Ω-cm) into the solid solution as compared to pure BT (~105 Ω-cm). This effect was also evident in dielectric loss data, which remained low at higher temperatures as the BZT content increased. In conjunction with band gap measurements, it was also concluded that the conduction mechanism transitioned from extrinsic for pure BT to intrinsic for 0.075 BZT suggesting a change in the fundamental defect equilibrium conditions. It was also shown that this improvement in insulation properties was not limited to BT- BZT, but could also be observed in the paraelectric SrTiO3-BZT system. [ABSTRACT FROM AUTHOR]

Piezoelectric ceramics with large energy density coefficient d33· g33 value have been found suitable for piezoelectric energy harvesting applications. In this study, the phase structures and piezoelectric properties of x Pb( Zr0.5 Ti0.5)O3− y Pb( Zn1/3 Nb2/3)O3−(1− x− y) Pb( Ni1/3 Nb2/3) O3 ( x PZT− y PZN−(1− x− y) PNN) ceramic were investigated with systematically varying PZN and PNN components. The ternary phase diagram of PZT− PZN− PNN system was illustrated and the composition region of morphotropic phase boundary (MPB) was determined. Piezoelectric and dielectric measurements verify that the materials in MPB region all present large d33 and d33· g33 values. In particular, very high d33· g33 coefficients of 20162.2 × 10−15 m2/N and 21026.3 × 10−15 m2/N are observed from samples 0.75 PZT−0.15 PZN−0.1 PNN and 0.8 PZT−0.05 PZN−0.15 PNN with compositions located on the rhombohedral phase side near MPB because the dielectric coefficient ε33T/ε0 decreases faster than the d33 coefficient at this side. [ABSTRACT FROM AUTHOR]