Search results for "electric field"
showing 10 items of 545 documents
Superconducting size effect in thin films under electric field: Mean-field self-consistent model
2019
We consider effects of an externally applied electrostatic field on superconductivity, self-consistently within a BCS mean field model, for a clean 3D metal thin film. The electrostatic change in superconducting condensation energy scales as $\mu^{-1}$ close to subband edges as a function of the Fermi energy $\mu$, and follows 3D scaling $\mu^{-2}$ away from them. We discuss nonlinearities beyond gate effect, and contrast results to recent experiments.
Dielectric response of BaTiO3 electronic states under AC fields via microsecond time-resolved X-ray absorption spectroscopy
2021
Abstract For the first time, the dielectric response of a BaTiO 3 thin film under an AC electric field is investigated using microsecond time-resolved X-ray absorption spectroscopy at the Ti K-edge in order to clarify correlated contributions of each constituent atom on the electronic states. Intensities of the pre-edge e g peak and shoulder structure just below the main edge increase with an increase in the amplitude of the applied electric field, whereas that of the main peak decreases in an opposite manner. Based on the multiple scattering theory, the increase and decrease of the e g and main peaks are simulated for different Ti off-center displacements. Our results indicate that these s…
Simultaneous Synthesis and Consolidation of Nanostructured MoSi2
2002
A new process combining electric field activation and the imposition of pressure from mechanically activated powder mixtures is demonstrated as a means to simultaneously synthesize and densify nano-MoSi2 in one step. Nanophase reactants (Mo + 2Si) produced by mechanical activation are reacted by field activation with the simultaneous application of a uniaxial pressure. Mo + 2Si powders were comilled in a specially designed planetary mill to obtain nanometric reactants but to avoid formation of any product phases. These were then subjected to high alternating currents (1600 A) and pressures of 106 MPa. Under these conditions, a reaction is initiated and completed within a short period of tim…
Space charge behavior of different insulating materials employed in AC and DC cable systems
2017
In this work, the space charge accumulation in three different XLPE based material has been carried out by using the PEA (Pulsed Electro-Acoustic) method. The specimens provided by a cables industry have been subjected to the same DC stress during polarization time at environment temperature. Afterwards, the high voltage generator has been turned off and the amount residual charge has been evaluated. The space charge profiles during polarization and depolarization have been carried out and compared. Finally, the distribution of electric field within the samples has been reported. In particular, the maximum distortion of electric field has been calculated by taking into account the distribut…
Object size effect on the contact potential difference measured by scanning Kelvin probe method
2010
International audience; Contact potential difference (CPD) was measured by macroscopic Kelvin probe instrument and scanning Kelvin probe microscope on Al, Ni and Pt on ITO substrates at ambient conditions. CPD values measured by scanning Kelvin probe microscope and macroscopic Kelvin probe are close within the error of about 10-30% for large studied objects, whereas scanning Kelvin probe microscope signal decreases, when the object size becomes smaller than 1.4 m. CPD and electric field signals measured using many-pass technique allowed us to estimate the influence of electrostatic field disturbance, especially, in the case of small objects.
Space charge accumulation in undersea HVDC cables as function of heat exchange conditions at the boundaries – water-air interface
2020
Transmission lines with undersea HVDC cables are an interesting technological solution for the supply of electrical energy to islands. The accumulation of space charge inside the dielectric layer of a HVDC cable is one of the most important element to consider in its design and during operation. The formation of space charge is due to various factors including the high dependence on the temperature of the electrical conductivity of the insulation and the establishment of a thermal gradient under load conditions. This research is focused on the space charge accumulation phenomenon around a section of a HVDC cable half dipped in water and half in air. Due to the high difference in thermal con…
Direct and indirect determination of electrocaloric effect in Na0.5Bi0.5TiO3
2017
This work has been supported by the National Research Program in the framework of the project “Multifunctional Materials and composites, photonics and nanotechnology (IMIS2).”
Deformation of bubbles in silicon gel insulation under an alternating electric field
2019
The behavior of silicone gel under electrical stress plays a significant role in the reliability and durability of high voltage electronic power devices due to its widespread use for the insulation of IGBT modules and other components. The charges accumulation at the bubble boundaries leads to significant displacements due to the establishment of Coulombic forces and the high deformability of colloidal system. The main purpose of this work is to validate a numerical approach useful to investigate, for a given silicone gel, the non-linear relation between the applied HVDC stress and the electric field over an air bubble within the insulation bulk. The analysis has been carried out by means o…
Investigation of ZrO[sub 2]–Gd[sub 2]O[sub 3] Based High-k Materials as Capacitor Dielectrics
2010
Atomic layer deposition (ALD) of ZrO 2 ―Gd 2 O 3 nanolaminates and mixtures was investigated for the preparation of a high permittivity dielectric material. Variation in the relative number of ALD cycles for constituent oxides allowed one to obtain films with controlled composition. Pure ZrO 2 films possessed monoclinic and higher permittivity cubic or tetragonal phases, whereas the inclusion of Gd 2 O 3 resulted in the disappearance of the monoclinic phase. Changes in phase composition were accompanied with increased permittivity of mixtures and laminates with low Gd content. Further increase in the lower permittivity Gd 2 O 3 content above 3.4 cat. % resulted in the decreased permittivity…
Electromechanical properties of Na 0.5 Bi 0.5 TiO 3 -SrTiO 3 -PbTiO 3 solid solutions
2018
Abstract Thorough studies of electric field-induced strain are presented in 0.4Na1/2Bi1/2TiO3-(0.6-x)SrTiO3-xPbTiO3 (NBT-ST-PT) ternary solid solutions. The increase of concentration of lead x induces crossover from relaxor to ferroelectric. Strain in a relaxor state can be described by electrostrictive behavior. The electrostrictive coefficients correspond to other well-known relaxor ferroelectrics. The concentration region with a stable ferroelectric phase revealed that the polarization dependence of strain does not exhibit nonlinearity, although they are inherent to the electric field dependence of strain. In this case, electric field dependence of strain is described in terms of the Ray…