Dielectric loss

About: Dielectric loss is a research topic. Over the lifetime, 20296 publications have been published within this topic receiving 349254 citations.

Enhanced electromechanical properties in all-polymer percolative composites

Abstract: In this letter, we discuss the enhanced electrostriction and dielectric constant in an all-polymer percolative composite consisting of poly(vinylidene fluoride-trifluoroethylenechlorotrifluoroethylene) [P(VDF–TrFE–CTFE)] terpolymer matrix and polyaniline (PANI) conductive particles. Using a self-consistent approach, we calculate the dielectric constant and dielectric loss tangent of the composite in excellent agreement with experiments, and demonstrate that the electrostriction enhancement is due to the electric field fluctuation in P(VDF–TrFE–CTFE) matrix, which becomes dominant when the dielectric constant of the second phase is much larger than that of the matrix. The inhomogeneous field distribution in the matrix has also been used to estimate the breakdown field of the composite, which agrees well with experimental measurement. The study could be used to design and optimize electrostrictive composites with optimal electromechanical properties.

Facile preparation of uniform barium titanate (BaTiO3) multipods with high permittivity: impedance and temperature dependent dielectric behavior

Abstract: Perovskite barium titanate (BaTiO3) multipods were prepared via high temperature solid state reaction. The crystal structure and morphology of BaTiO3 particles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), and scanning probe microscopy (SPM). The XRD analysis of the crystal structure revealed that a single-phase compound was formed having tetragonal crystal structure. Calorimetric study (DSC) over room to high temperature was used to find the energy involved in different steps of synthesis especially during the initiation and the termination process for the formation of BaTiO3. These multipods have high average aspect ratio (∼10, where average diameter ∼300 nm and average length ∼3 μm) as seen from FESEM. UV-Vis spectroscopy reveals that the prepared material is UV active. The bulk and surface chemical composition of these BaTiO3 particles as investigated by Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) spectra reveals that in the prepared BaTiO3, the titanium ions exist in two different oxidation states, namely Ti3+ and Ti4+. The BaTiO3 multipod exhibits high permittivity with relatively low dielectric loss. From impedance analysis of the material, the dual resistivity characteristics, one for grain and the other for grain-boundary can be distinguished. An equivalent circuit has been proposed through analysis of the complex impedance plot (Nyquist plot) for BaTiO3 multipods. This material has perfect capacitative nature as seen from the Bode plot, and can be used for charge storage devices and other electronic applications. From temperature dependent dielectric analysis, the Curie temperature of BaTiO3 multipods is found to be ∼85 °C.

Nanostructured Metal Oxide Thin Films for Humidity Sensors

Abstract: Capacitive humidity sensors were fabricated using countersunk interdigitated electrodes coated with amorphous nanostructured TiO2, SiO2, and Al2O3 thin films grown by glancing angle deposition. The capacitive response and response times for each sensor were measured. The sensor utilizing TiO2 exhibited the largest change in capacitance, increasing exponentially from ~ 1 nF to ~ 1muF for an increase in relative humidity from 2% to 92%. Adsorption and desorption response times were measured using flow rates of 2.5 l/min and were between 90 ms and 300 ms for the sensors studied here. A simple model of the capacitive response of the devices has been developed and used to calculate the dielectric constant of the combined system of our films and adsorbed water. The obtained dielectric constants are found to be much higher than bulk or literature values for similar systems.

Compositional dependence of phase structure and electrical properties in (K0.42Na0.58)NbO3-LiSbO3 lead-free ceramics

Abstract: (1−x)(K0.42Na0.58)NbO3-xLiSbO3 [(1−x)KNN-xLS] lead-free piezoelectric ceramics were prepared by the conventional mixed oxide method. The compositional dependence of the phase structure and the electrical properties of the ceramics were studied. A morphotropic phase boundary (MPB) between the orthorhombic and tetragonal phases was identified in the composition range of 0.04