Abstract
Dielectric materials with high electric energy density and low dielectric loss are critical for electric applications in modern electronic and electrical power systems. To obtain desirable dielectric properties and energy storage, nanocomposites using Ba0.5Sr0.5TiO3 (BST) as the filler and poly(vinylidene fluoride-chlorotrifluoroethylene) as the matrix material are prepared with a uniform microstructure by using a newly developed process that combines the bridge-linked action of a coupling agent, solution casting, and a hot-pressing method. When a proper amount of coupling agent is used to modify the surface of the nanoparticles, the composite exhibits a higher dielectric constant and a more uniform microstructure. A dielectric constant of 95, dielectric loss of 0.25, and energy density of 2.7 J/cm3 is obtained in the nanocomposite with 30 vol.% of BST and 15 wt.% of coupling agent. The results suggest that the energy storage ability of the composites could be improved by the surface modification of the fillers and from the interface compatibility between the fillers and the polymer matrix.
Highlights
INTRODUCTIONTo obtain high-performance dielectric composites, it is very critical to disperse ceramic nanoparticles into the polymer matrix homogeneously and to achieve high quality dielectric composites with a uniform microstructure.[6] Recently, more and more studies indicated that simple mixing and solution casting of a filler in a polymer matrix generally resulted in poor film quality and inhomogeneity.[26,27,28,29,30,31,32,33] The reason for this is that introducing high surface energy ceramic particles into a low surface energy polymer causes highly inhomogeneous electric fields at the interfaces, which may conduct charges due to improper and non-uniform dispersion and will reduce the dielectric breakdown strength of the composites.[34] The suitable organic modification of the surface of the particles can reduce the agglomeration of the nanoparticles and enhance free dispersions
For the next-generation high energy density capacitors, it is essential to develop dielectric materials with a high dielectric constant, low loss, high breakdown field, and a low cost for advanced electronic devices and electric power systems.[1,2,3,4] The value of energy storage density in a dielectric material is strongly dependent on the dielectric constant and breakdown strength (Eb).[5,6] it is very difficult to optimize them synchronously since the enhancement of dielectric constant2158-3226/2017/7(7)/075210/8075210-2 Wu et al.AIP Advances 7, 075210 (2017)is usually accompanied by a high loss, which may result in a low breakdown strength
The results indicate that the amount of introduced coupling agent is critical to obtain a higher dielectric constant and energy density
Summary
To obtain high-performance dielectric composites, it is very critical to disperse ceramic nanoparticles into the polymer matrix homogeneously and to achieve high quality dielectric composites with a uniform microstructure.[6] Recently, more and more studies indicated that simple mixing and solution casting of a filler in a polymer matrix generally resulted in poor film quality and inhomogeneity.[26,27,28,29,30,31,32,33] The reason for this is that introducing high surface energy ceramic particles into a low surface energy polymer causes highly inhomogeneous electric fields at the interfaces, which may conduct charges due to improper and non-uniform dispersion and will reduce the dielectric breakdown strength of the composites.[34] The suitable organic modification of the surface of the particles can reduce the agglomeration of the nanoparticles and enhance free dispersions Surfactants such as phosphate sulfonate, silane, and carboxylate based surface modifiers or coupling agents may be added to the polymer nanocomposites for improved quality of the dispersion and to increase the dielectric breakdown resistance.[35] It is believed that the bridge-linked action of the coupling agent can improve the composite uniformity and optimize the dielectric response of the composite. The results indicate that the amount of introduced coupling agent is critical to obtain a higher dielectric constant and energy density
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