Dielectric and thermal behavior of 0.75BiFeO3-0.25BaTiO3 filled ethylene vinyl acetate composites (original) (raw)
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Dielectric characterisation of epoxy nanocomposite with barium titanate fillers
IET Nanodielectrics, 2020
High permittivity materials are currently in use for mitigation of electrical stress in high-voltage apparatus and energy storage systems. In this work, epoxy-based high permittivity nanocomposites with Barium titanate (BaTiO 3) nanofillers are considered, for the purpose of stress mitigation. Uniform dispersion of the fillers in the polymer up to 10% by volume is achieved. Apart from the use of as-received fillers, the effect of using surface-functionalised nanoparticles (with 3glycidoxypropyltrimethoxy-silane) before use is also investigated. The nanocomposite is characterised in terms of its complex permittivity, DC conductivity, short-term AC breakdown strength and space charge accumulation, to gauge its suitability for use in high-voltage insulation. Complex permittivity is measured using broadband dielectric spectroscopy over a broad frequency range of 1 mHz to 1 MHz. DC conductivity is studied from polarisation-depolarisation current measurements. Short-term AC breakdown strength tests are performed at power frequency (50 Hz). Space charge density along the sample thickness is obtained using pulsed electro-acoustic technique. A computational case-study is presented to show the feasibility of using the high permittivity nanocomposite for electric stress control in high-voltage equipment (viz., at mounting flanges of 69 kV bushings).
Journal of Rare Earths, 2015
0.5BiDy x Fe 1-x O 3-0.5PbTiO 3 (0.5BD x F 1-x-0.5PT) (x=0.00, 0.05, 0.10, 0.15, 0.20) multiferroic composites were prepared by conventional solid state reaction method. Structural characterization was performed by X-ray diffraction and the materials showed tetragonal structure at room temperature. Surface morphology of the composites was studied by a scanning electron microscope (SEM). Frequency and temperature dependence of dielectric constant (ε r) and dielectric loss (tanδ) of 0.5BD x F 1-x-0.5PT were measured in a wide range of frequency (100 Hz to 1 MHz) and temperature (25 to 400 ºC). The analysis of the study showed that the ε r and tanδ decreased with increasing frequency in the given range for all the samples which could be explained through the occurrence of dipole relaxation process. The effect of substitution of rare earth element dysprosium (Dy) showed increase in ε r in all the samples prepared for different concentrations from 0.00 to 0.20. An explanation for high value of ε r for Dy modified 0.5BiFeO 3-0.5PbTiO 3 (0.5BF-0.5PT) compared to Gd modified 0.5BF-0.5PT was provided. The variation of AC conductivity with inverse temperature found to obey the Arrhenius equation and the composites showed negative temperature coefficient of resistance (NTCR) behavior. The activation energy was found to be in the range from 0.25 to 0.40 eV for all the studied samples.
Journal of Polymer Research, 2012
ABSTRACT Poly(vinylidene fluoride)/Pb(Zr0.53Ti0.47)O3([PVDF]1 − x/[PZT]x ) composites of volume fractions x and (0–3) type connectivity were prepared in the form of thin films. The films were prepared by solvent casting with PZT powder of 0.84, 1.86, and 2.35 μm average size with filler contents up to 40 % volume. The crystalline phase of the polymer matrix was the nonpolar α-phase and the polar β-phase. Dielectric measurements were performed in order to evaluate the influence of the filler size and content as well as the effect of the polymer matrix in the overall response of the material. No nucleation effect of any of the phases was observed for the used fillers. The spherulitic structure of the pure α-PVDF and the characteristic porosity of the β-phase material are destroyed for high PZT volume fractions. The inclusion of ceramic particles in the PVDF polymer matrix increases the complex dielectric constant of the composites independently of the PVDF polymer matrix. The dielectric properties of the composites are mainly affected by the amount of the ceramic particles. With respect to the relaxation processes of the polymer, the activation energy of the αa-relaxation increases and the glass transition temperature decreases with increasing particle size and content. The high-temperature conductivity decreases with increasing filler content and there is an important contribution of the Maxwell-Wagner-Sillars effect to the overall dielectric response.
Applied Physics Letters, 2007
Composites of micronanosize BaTiO3 (BT) particles embedded into a polyvinylidene fluoride matrix were prepared. They were studied with respect to the effect of nanosize particles on microstructure and dielectric properties. The results show that the dielectric permittivity of composites with nanosize BT is close to the predicted values calculated at high concentration of fillers, if the interactions among BT fillers and between BT fillers and polymer are included. The enhanced dielectric permittivity mainly originates from a noticeably increasing phase interfaces in the composites, which brings out the strong interfacial polarization effect at low frequencies.
2007
A unique method has been introduced to measure the dielectric constant of polymer/ceramic composites using an effective medium instead of using the general methods of preparing bulk sintered pellets or films. In this work, a new and a simple method has been applied to measure the dielectric constant of polyvinyl cyanoethylate/barium titanate composites. The results are obtained by dispersing the ceramic powders in the polymer of a relatively low dielectric constant value. The dielectric constant of the composites is measured with varying ceramic volume percentages. The obtained results are compared with the many available theoretical models that are generally in practice to predict the dielectric constant of the composites. Then these results are extrapolated to comprehend the dielectric constant values of ceramic particles as these values form the base for the design of the composite. The precision and simplicity of the method can be exploited for predictions of the properties of nanostructure ferroelectric polymer/ceramic composites Ó
Dielectric Properties of Epoxy / BaTiO 3 Composites
2010
Dielectric properties such as relative permittivity (dielectric constant) (ε′) and dielectric loss (ε") of (epoxy resin-barium titanate) composites behaviour as a function of barium titanate volume fractions (5, 10, 15, 20, 25, 30, 35, 40) vol.%, temperature in the range (30-110) • C and frequency in the range (120Hz-2MHz), were investigated and given a qualitative explanation. The permittivity was found to increase with the increase of BaTiO 3 filler content, and was high in the low frequency range, but diminishes as the frequency increases. The permittivity was found to increase with the increase of temperature up to the transition temperature (Tg). Ac. conductivity and impedance of the composites behaviours as function of frequency and temperature have also been investigated. [
Temperature influence on dielectric energy storage of nanocomposites
Ceramics International, 2015
The demand for high energy density dielectric capacitor devices is increasing due to their significant role in stationary power systems, mobile devices and pulse power applications. The polymer film based dielectric capacitor is still one of the most widely used energy storage devices owing primarily to its high energy density and low cost. To further enhance the energy density, high dielectric constant ceramic inclusions have been embedded into the polymer matrix; however, the relationship between temperature and energy density has not yet been fully investigated. Therefore, in this paper, a commonly used composites with barium titanate (BaTiO 3) nanoparticles embedded in polyvinylidene fluoride (PVDF) matrix were fabricated using a solution casting method in order to explore their energy densities within a temperature range from 20 1C to 120 1C. Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) were used for material morphology and crystal structure characterization. Capacitance and breakdown strength were measured throughout the temperature range in order to determine the energy density of the samples with 10%, 20%, 30% and 40% volume fractions. It is found that nanocomposites with 30% volume fraction displayed the highest energy density of 5.79 J/cm 3 at 50 1C.
SN Applied Sciences, 2019
The dielectric behaviour of a polymer/ceramic composite (PCC) based on ferroelectric polymer [polyvinylidene fluoride (PVDF)] and nano-barium titanate (n-BaTiO 3), prepared under the novel cold pressing method, was investigated. Large enhancement of effective dielectric constant (ɛ eff ~ 450) with lower loss tangent (tan δ ~ 0.9) at 50 Hz was observed for the PCC with 0.60 as the volume fraction of n-BaTiO 3 into the PVDF matrix. The enhancement of ɛ eff is attributed to the large interfacial polarisation arising due to the charge storage at the interfaces of the spherulites of PVDF and at the polymer/filler interfaces of PCC. The dielectric results have been explained on the basis of sum effect with the help of the standard Yamada model at 1 kHz, while the low-frequency dielectric behaviour has been explained qualitatively as a combination of both interfacial polarisation at the interfaces of the spherulites and the sum effect of the Yamada model. The achieved lower tan δ for the PCC as compared to the polymer/metal composites (PMC) is attributed to the highly insulating nature of PVDF and semiconducting n-BaTiO 3. The thermal stability of the composites is also maintained due to the higher melting temperature (170 °C) of PVDF. The cold-pressed PCC based on PVDF will act as better polymer dielectric for electrical energy storage applications as compared to the reported cold-pressed PMC and the cold pressing may be an effective method of preparation (since the unnecessary introduction of thermal disorder is avoided in this method) in developing polymer dielectrics.
Thermogravimetric and Dielectric Study of ER/BaTiO 3 /ZnO Composites
Macromolecular Symposia, 2013
Hybrid composites consisted of an epoxy resin and BaTiO 3 as well as ZnO particles were prepared and studied. Polymer composites with ferro-and/or piezoelectric particles are expected to exhibit functional behaviour due to the varying polarization of the fillers. The BaTiO 3 content was kept constant in all studied composites, while ZnO content varied from 0 to 50 particles per hundred resin per weight. Thermal properties of the systems were examined by means of Thermogravimetric/Differential Thermal Analysis technique. Decomposition temperature for all systems was found to lie in the range 385-395 C, while residual weight for hybrids was significantly higher compared to epoxy resin. Dielectric response of the tested systems was determined via Dielectric Relaxation Spectroscopy.