Search results for "ELECTRICITY"

Nonlocal model for a magneto-electro-elastic nanoplate

2013

A mathematical model based on nonlocal third-order shear deformation plate theory has been developed to evaluate the mechanical and electromagnetic behavior of magneto-electro-elastic nanoplates. Two types of magneto-electro-elastic composites have been considered, all of them combination of Barium Titanate sheets, that represents the piezoelectric phase, and Cobalt Ferrite, that is the piezomagnetic component. Setting magneto-electric boundary conditions on each laminate, it has been possible to extrapolate and to analyze free vibrations frequencies for all considered plates, allowing to do objective assessments on what factors influence laminate modes and, especially, how these vary in th…

Piezoelectric coefficients by molecular dynamics simulations in the constant stress ensemble: A case study of quartz

2006

Piezoelectric (strain) coefficients dij of quartz are calculated in terms of molecular dynamics as a function of pressure and temperature. We review the necessary formulas for the computation of electromechanical materials coefficients obtained at constant stress and temperature, and discuss how to overcome complications of the definition of polarization variations due to fluctuating box geometries. A method is employed suppressing significantly stochastic fluctuations of the estimators for piezoelectric coefficients. A recently suggested force field for the simulation of SiO2 reproduces available experimental data quite accurately. Predictions are made for the pressure dependence of dij of…

Comparative Acoustic and Contact Studies of Elasticity of Ferroelectric LixNa1 - xTa0.1Nb0.9O3Solid Solutions at Nanometer Spatial Resolution

2009

Comparative acoustic and contact studies of elastic properties of the Li x Na 1−x Ta 0.1 Nb 0.9 O 3 (x = 0.015–0.135) ferroelectric solid solution ceramics are reported. A good agreement is obtained between the values of elastic modules determined by acoustic and contact methods at nano-scale spatial resolution.

Tunable Bistability in a Three-Dimensional Spin-Crossover Sensory- and Memory-Functional Material

2005

Room-temperature electrical addressing of a bistable spin-crossover molecular system.

2011

Relaxor ferroelectric ceramics of LiTaO3-type

1992

Abstract A ferroelectric relaxation has been identified in Li1-xCax (Ta1-xZrx)O3(x = 0.15 and 0.20) ceramics with LiTaO3-type structure. The relaxation frequency fr is minimum and the dispersion step (ϵ′S - ϵ′∞) is maximum at TC. When x increases, a higher conductivity associated with a lower activation energy and a decrease of the magnitude of fr at Tc are observed, while the unit cell volume becomes larger, TC lower and the transition more diffuse.

The depolarization field effect on the thin ferroelectric films properties

2002

Abstract The calculation of the spontaneous polarization (Ps), dielectric susceptibility (χ) and pyroelectric coefficient (Π) of the ferroelectric films has been performed in the phenomenological theory framework. Euler–Lagrange equation was solved analytically under the boundary conditions with different extrapolation lengths at two surfaces, respectively. The depolarization field contribution was taken into account in the model of short-circuited mono domain ferroelectric film, treated as perfect insulator. The detailed analysis of the aforementioned quantities’ space distribution and their average values in two cases with and without depolarization field was carried out. It was shown tha…

Ferroelectric Behavior in Epitaxial Films of Relaxor PbMg1/3Nb2/3O3

2004

The nonlinear dielectric response of epitaxial thin films of relaxor ferroelectric PbMg1/3Nb2/3O3 was experimentally studied using digital Fourier analysis. Change from glass-like to ferroelectric behavior was detected in a broad temperature range, at relatively low ac and/or dc electric fields, and at a time scale of seconds. The presence of interfaces and peculiar microstructure of thin films are suggested to determine such a specific behavior.

Giant piezoelectricity in B/N doped 4,12,2-graphyne

2020

Abstract The effects of boron (B) and nitrogen (N) substitutions in 4,12,2-graphyne on its geometric structure and mechanical as well as electronic properties have been systematically investigated with the aid of density functional theory (DFT). The trend in the elastic properties of the substituted systems is determined by the doping positions and the type of the dopants. The Bader charge analysis reveals that the N dopant at the sp-site destroys the acetylenic linkage in 4,12,2-graphyne, but instead tends to form a polar bond, or even possibly a charge-shift bond. In particular, an obvious in-plane piezoelectricity is induced by foreign atom substitutions owing to the deformation of the p…

Epitaxial Films of Relaxor Ferroelectric PbMg1/3Nb2/3O3in Strong Electric Fields

2005

Epitaxial thin films of perovskite relaxor ferroelectric PbMg 1/3 Nb 2/3 O 3 were grown on MgO (001) substrates by pulsed laser deposition using La 0.5 Sr 0.5 CoO 3 bottom electrode layers. Dielectric response of the films was experimentally studied as a function of temperature and frequency in a broad range of amplitudes of ac electric field (to 10 MV/m) and magnitudes of dc electric field (to 50 MV/m). At small fields, a glass-like behavior was observed. With increasing magnitude of the dc field, an onset of a polar state was detected. The orientation of the polar clusters along the direction of the field and fluctuations of the direction of their dipole moments were suggested to determin…