Ferroelectric Properties Of Composites Research Articles

CNT loaded PVDF-KNN nanocomposite films with enhanced piezoelectric properties

The emerging smart PVDF-based composites can compensate for the intrinsic property deficiencies in either of their components. The properties of the composite are determined by the properties of the constituents and its fabrication method. In this research, a lead-free piezoelectric ceramic, potassium sodium niobate (KNN), was used as the primary reinforcement, and MWCNTs were added to improve the electrical properties. Solution casting was used to prepare PVDF-KNN-CNT composite films. After phase and structure identification of composites using SEM, XRD, FTIR, and TGA methods, the dielectric, piezoelectric and ferroelectric properties of the products were investigated. The obtained results indicated a strong dependency of dielectric, piezoelectric, and ferroelectric properties of composites on KNN content. Samples with the highest KNN content rendered εr, d33 and g33 values of 156, 28 pC/N, and 20.32 mV m/N, respectively. Introducing a small amount of conductive CNT to primary PVDF-KNN composites can drastically affect the electrical properties by severely interfering in the charge distribution within the sample. While the dielectric constant was enhanced by increasing CNT content, both piezoelectric and ferroelectric properties showed their best behavior at a critical CNT loading. Beyond this limit, a percolation path formed, which is responsible for power consumption. At the optimum CNT amount, d33 and g33 reached 50 pC/N and 31.93 mV m/N, respectively. The presence of conducting CNTs gave rise to the formation of more round polarization curves with higher remnant polarization. The present findings give a prospective understanding of smart piezoelectric polymer-based composites that can be used as sensors and energy harvesters.

The effect of Ag@SiO2 core‐shell nanoparticles on the dielectric properties of PVDF based nanocomposites

AbstractHigh dielectric properties material has a profound influence on the development of electronic power system, polymer based composites obtained a great number of achievements on it. A new strategy, which covered a layer of insulation on the surface of the inorganic particles to form a core‐shell structure, then used it for composites is a good choice. In this article, a series of PVDF based nanocomposite with different contents were prepared by using PVDF flexible polymer as substrate and core‐shell structure Ag@SiO2 nanoparticles as fillers. The effects of Ag@SiO2 core‐shell nanoparticles on the structure and properties of composites were investigated. Results showed that Ag@SiO2 has a typical core‐shell structure and the diameter size of Ag@SiO2 nanoparticles is 100 nm in average with about 20 nm thickness of SiO2 shell. XRD analysis showed that the addition of Ag@SiO2 nanoparticles induce a transition on crystal structure of PVDF from multiphase to mainly β phase, which result in an improvement on ferroelectric properties of composites. Broadband dielectric spectroscopy results indicate that the dielectric constant and dielectric loss of nanocomposites are positively correlated with the filler's contents. The tested dielectric constant of composites increase from 8.42 (5 wt% fillers content) to 10.1 (20 wt% fillers' content), coupled with an increase on electrical breakdown strength from 21.22 to 31.46 kV/mm. The calculated energy density also increases from 0.016777 to 0.044234 J/cm3.

A systematic study of structural, magnetic and electric properties of perovskite-spinel composites prepared by sol-gel technique

Multiferroics composite of perovskite BiFeO3 and spinel ferrites NiFe2O4/ZnFe2O4/CoFe2O4 with different composition were prepared by sol-gel method. Detailed investigations were made on the structural, magnetic and ferroelectric properties of these composites. The X-Ray Diffraction pattern confirms the formation of distorted perovskite and spinel phases of BiFeO3 and NiFe2O4, ZnFe2O4, CoFe2O4 respectively. Transmission Electron Microscopy (TEM) images reveals the particle size and the elemental idea of phase formation. The particle sizes calculated using TEM of NiFe2O4, ZnFe2O4, CoFe2O4 are 10–20 nm, 20–30 nm, 15–25 nm respectively and these are compatible with XRD results. The results of Scanning Electron Microscopy (SEM) images reveal that all the samples exhibit a very uniform distribution of perovskite and spinel phases in composites. The modified microstructure of composites is effective in reducing the leakage of electric charges which occurs due to a chain formation of the spinel-ferrite phase particle, so the electrical, magnetic and ferroelectric properties of composites may improve with spinel ferrites content.

Ferroelectric properties of composites containing BaTiO3 nanoparticles of various sizes

Size effects, including the occurrence of superparaelectric phases associated with small scale, are a significant research topic for ferroelectrics. Relevant phenomena have been explored in detail, e.g. for homogeneous, thin ferroelectric films, but the related effects associated with nanoparticles are usually only inferred from their structural properties. In contrast, this paper describes all the steps and concepts necessary for the direct characterization and quantitative assessment of the ferroelectric properties of as-synthesized and as-received nanoparticles. The method adopted uses electrical polarization measurements on polymer matrix composites containing ferroelectric nanoparticles. It is applied to ten different BaTiO3 particle types covering a size range from 10 nm to 0.8 μm. The influence of variations of particle characteristics such as tetragonality and dielectric constant is considered based on measurements of these properties. For composites containing different particle types a clearly differing polarization behaviour is found. For decreasing particle size, increasing electric field is required to achieve a given level of polarization. The size dependence of a measure related to the coercive field revealed by this work is qualitatively in line with the state of the knowledge for ferroelectrics having small dimensions. For the first time, such results and size effects are described based on data from experiments on collections of actual nanoparticles.

Dielectric Properties of Ferroelectric Composites with TGS Inclusions

Dielectric properties of composites consisting of nanoporous aluminium oxide Al2O3 or glass SiO2 with inclusions of the ferroelectric triglycine sulphate (TGS) are investigated in the present work. Our investigations enable us to assume the presence of ferroelectric state in these materials.

Domain switching and non-linear coupling of ferroelectric composites

One of the most notable characteristics of ferroelectric materials is that they could undergo spontaneous polarization and spontaneous strain changes by applied fields. Reorientation of the spontaneous polarization and spontaneous polarization strain of ferroelectric inclusions in ferroelectric composites can change microstructures and affect effective electroelastic properties of ferroelectric composites. Based on orientation distribution function and its evolution as well as switching criterion, non-linear electromechanical coupling behaviour of ferroelectric composites is studied by application of micromechanics. A constitutive model of ferroelectric composites is developed. Comparison between analytical and experimental results shows that the model presented can describe many non-linear electromechanical coupling problems of ferroelectric composites such as polarization or depolarization, etc.

The preparation and properties of ferroelectric-composites possessing glass-like matrix

Abstract The investigation results of the electric properties of non-organic composite materials are given in the present paper. These materials containing both crystal and amorphous phases are obtained by the ceramic technology methods. Crystal phase formed from ferroelectric BaTiO3 or from the solid solution Pb(Zr,Ti)O3 in dispersed state are given here. The amorphous phase is formed from the glass of BaO(SrO,PbO)-B2O3(GeO2)-Al2O3-system with oxides additives of the transition elements. Properties of three different types of materials having piezoelectric, electret and semiconductor effects are made and studied here.