Papers by Keyword: Ferroelectric Materials

Abstract: Harnessing ambient kinetic energy from water droplets is a promising route for sustainable power. However, efficient wireless delivery of this energy remains challenging. This study demonstrates a droplet-based electricity generator (DEG) using a composite interfacial structure of ferroelectric polyvinylidene fluoride (PVDF) and triboelectric fluorinated ethylene propylene (FEP). The device achieves an open-circuit voltage up to 254 V and an energy output of 17.17 μJ per droplet. An impedance-matched electronic switch (E-Switch) enables efficient excitation of a magnetically coupled LC resonator, facilitating wireless energy transfer over 50 cm using compact 2-cm coils. System evaluations confirm stable transmission under varying distances and misalignments. This work provides a self-powered, cable-free energy platform well-suited for environmental monitoring and distributed electronics.

Abstract: In this paper, the effect of a non-linear dielectric gate stack on the short-circuit performance of a 1.2 kV SiC MOSFET was analyzed through TCAD simulations. Starting from the TCAD model of a commercial 1.2 kV, its standard gate oxide was replaced with a stack formed by oxide and a non‑linear dielectric, characterized by a temperature dependent permittivity. This variation on temperature can be exploited to reduce the current conducted during short-circuit events, lowering the temperature reached through the device by about 30%, without affecting its static and dynamic performance.

Abstract: Lead lanthanum zirconate titanate (PLZT) transparent ceramics present an attractive electrically controlled light scattering performance with high transmittance and large contrast ratio. PLZT ceramics of 8 mole% lanthanum with different Zr/Ti ratios (Zr/Ti=68/32, 70/30, 72/28) were prepared by the hot pressing method to figure out the influence of Zr/Ti ratios to the light scattering performance. X-ray diffraction patterns confirm that all the samples are perovskite structure with no secondary impurity phase detected. All the three compositions show double tending slim hysteresis loops which due to antiferroelectric phase coexisted. Besides, within the range of near-infrared to ultraviolet wavelength, all the PLZT samples show high transmittance. While the Zr/Ti ratio increasing from 68/32 to 72/28, the transmittance reduced value R_T of the sample decreases gradually (λ: 632.8 nm). PLZT (8/68/32) sample shows a maximum R_T, it promises a good application in optical modulators, goggles and so on.

Abstract: The concept of energy harvesting works towards developing self-powered devices that do not require replaceable power supplies. Energy scavenging devices are designed to capture the ambient energy surrounding the electronics and convert it into usable electrical energy. A number of sources of harvestable ambient energy exist, including waste heat, vibration, electromagnetic waves, wind, flowing water, and solar energy. While each of these sources of energy can be effectively used to power remote sensors, the structural and biological communities have placed an emphasis on scavenging vibrational energy with ferroelectric materials. Ferroelectric materials have a crystalline structure that provide a unique ability to convert an applied electrical potential into a mechanical strain or vice versa. Based on the properties of the material, this paper investigates the technique of power harvesting and storage.

Abstract: he solid solution between the normal ferroelectric Pb(Zr1/2Ti1/2)O3 (PZT) and relaxor ferroelectric Pb(Co1/3Nb2/3)O3 (PCoN) was synthesized by the solid state reaction method. Sintered PZT-PCoN ceramics were annealed at temperatures ranging from 850 to 1,100°C for 4 h. X-ray diffraction patterns revealed changes of crystalline structure after annealing, which could be correlated to the accompanied changes in dielectric properties. Furthermore, significant improvements in the dielectric responses were observed in this system. After annealing, a huge increase of up to 200% occurred in the dielectric constants, especially near the temperature of maximum dielectric constant.

Abstract: Relaxor ferroelectric Pb(Mg1/3Nb2/3)O3 (PMN) crystals were grown at low temperature by a single-step hydrothermal process, using the mixture of PbO, MgO and Nb2O5 as precursors. The precursors were just heated to 150 oC for 24 h. The effect of the KOH concentration on the morphology and microstructure of PMN crystals was systematically investigated. The optimum KOH concentration was found to be 11M, which led to the stabilization of the perovskite crystals against the pyrochlore phase, and to the growth of high-quality PMN crystals suitable for subsequent characterization. According to morphological evolution during the reaction, two possible growth mechanisms are proposed. When the KOH concentration is 11M, at the early stage of the reaction, the starting materials dissolve, and then promote the formation of spherical intermediate pyrochlore phase followed by the formation of primary cubic PMN crystals. At the same time, a platelet-shaped intermediate pyrochlore phase also forms and then grows into larger platelet-shaped PMN crystals.

Abstract: Relaxor-based lead-lanthanum-zirconate-titanate (PLZT) thick films were prepared on Ti substrates by a simplified hydrothermal method, in which the precursors were heated to 150 oC with durations from 8 to 32h. The mixture of oxides was used as the staring materials. The smooth PLZT films with a single perovskite structure were obtained through the synthesis route. Structural and morphological studies were carried out on hydrothermally synthesized films. The influences of the mineralizer concentration on the structural, morphological, and physical characteristics of the particles are studied. Phase characterization and crystal orientation of the PLZT thick films were investigated by x-ray diffraction analysis (XRD). The dielectric constant and dielectric loss of the PLZT thick films were measured. In the frequency range from 1000 to 100 MHz, the dielectric constant and the dielectric loss were very steady.

Abstract: New experiment systems that can offer electromechanical and electromagnetic coupling loads were established. Measurement skills and technologies under coupling loads have been developed. The experimental difficulties and technical problems, such as insulation, discharge, compressive testing of brittle ferroelectrics and so on, were well resolved. The constitutive experiments of piezo/ferroelectrics or ferromagnetic materials were carried out. Moiré Interferometry was applied to the measurement of transformation of the crack tip in ferroelectric ceramics under coupling loads. The deformation concentration near the internal electrode tip caused by non-uniform electric field was investigated by means of Digital Speckle Correlation Method (DSCM). With an aim to accomplish both measurements of constitutive response of the magnetostrictive materials and the fracture experiments of general soft ferromagnetic materials, a magnetomechanical-coupling testing setup was established, which is controlled by an industrial PC. The software was programmed to monitor the testing process and to deal with the acquired data. The characteristic curves of ferromagnetic materials, such as TbxDy1-xFe2 alloys, were measured, including the hysteresis loops, the magnetostriction curve and stress-strain curve.

Abstract: We investigated the structural and electrical properties of the 0.5% Ce-doped Ba(ZrxTi1-x)O3 (BZT) thin films with a mole fraction of x=0.2 and a thickness of 150 nm for the MLCC (Multilayer Ceramic Capacitor) application. Ce-doped BZT films were prepared on Pt/Ti/SiO2/Si substrates by a RF magnetron sputtering system as a function of Ar/O2 ratio and substrate temperature. X-ray diffraction patterns were recorded for the samples deposited with three different substrate temperatures. The thickness and the surface roughness of the films deposited with different Ar/O2 ratios were measured. The oxygen gas, which was introduced during the film deposition, had an influence on the growth rate and the roughness of the film. The surface roughness and dielectric constant of the Ce-doped BZT film varied with Ar to O2 ratios (5:1, 2:1, and 1:1) from 1.21 nm to 2.33 nm and 84 to 149, respectively. The Ce-doped BZT film deposited at lower temperature has small leakage current and higher breakdown voltage.

Abstract: A giant enhancement of the static dielectric permittivity and a giant dielectric relaxation in a heterogeneous medium consisting of regularly arranged spheroids distributed in the matrix and described by the Maxwell-Garnett formula were studied. The influence of the inclusions aspect ratio and their concentration is analyzed. The possibility to apply the obtained results to the theoretical consideration of different heterogeneous ferroactive materials is proved. It is shown that observation of the collective dielectric resonance in such media is impossible, and only relaxation processes are the way of obtaining unusual properties of considered materials. Some valuable formulae are derived and discussed.