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Approach to Inversion Design of Dielectric Material Based on the First-Principle
摘要： The ?rst-principle is an e?ective method for the material property calculation. One inversion design idea of dielectric material based on the ?rst-principle was put forward. In this kind of material design thought, the speci?c demanded dielectric property of material is the starting point of the whole design course. The atomic structure characteristic of the material is solved using the inversion model based on the ?rst-principle. And the key issues needing researching were discussed, these problems were quantized structure of electromagnetic and optic ?eld, the quantized polarization theory of dielectric material, the uniform calculation method of dielectric property and the dielectric material inversion model.
关键词： Dielectric material,First-principle,Dielectric property,Inversion design
更新于2025-09-23 15:23:52
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Dielectric property of modified barium titanate/polyamide 11 nanocomposites with different surfactants
摘要： Barium titanate/polyamide 11 (BT/PA11) nanocomposites were prepared by modifying BT nanoparticles with dry surface modification process, which had well dispersion, high dielectric constant, and low dielectric loss. Various methods were reported to improve dispersion and compatibility with complex process and high cost. Herein, three surfactants [γ-aminopropyl triethoxy silane (KH550), sorbitan monostearate (SP60), and octadecyl phosphate ester (OPE)] were chosen to modify BT nanoparticles. Then modified-BT nanoparticles were blended with PA11. The structure was characterized by Fourier transform infrared, scanning electron microscope, and wide angle X-ray diffraction. Dielectric property was studied by broadband dielectric spectroscopy. The frequency dependence and temperature dependence of dielectric constant, dielectric loss, and dielectric modulus were analyzed. In general, dielectric property has strong frequency and temperature dependence. Furthermore, dielectric spectra shows that modified BT/PA11 nanocomposites have higher dielectric constant, lower dielectric loss, fewer interface polarization, and more dipole polarization. In contrast to three surfactants, OPE-BT nanoparticles have better effects, whose dielectric constant increases from 19 to 28 at 1 Hz, and dielectric loss decreases from 0.36 to 0.23. Meanwhile, mechanical property was characterized by universal testing machine. In all, the work improves dispersion of BT nanoparticles and dielectric property with easy process and low cost. ? 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47447.
关键词： BT/PA11 nanocomposites,dielectric property,modification,surfactants
更新于2025-09-23 15:23:52
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An Eco-friendly Flexible Piezoelectric Energy Harvester That Delivers High Output Performance is Based on Lead-Free MASnI3 Films and MASnI3-PVDF Composite Films
摘要： An environmentally-friendly lead-free methylammonium tin iodide (MASnI3) perovskite is successfully synthesized using a facile approach of an antisolvent-assisted collision technique under room ambient conditions, which results stability within 24 h under ambient room conditions. The phase transition of MASnI3 from tetragonal to cubic is first observed at ~ 30 °C. Polycrystalline MASnI3 films reveal a high dielectric constant of ~ 65 at 100 kHz, a low-leakage current density of 7 × 10-7 A cm-2 at 50 kV cm-1, well-developed P-E hysteresis loops, and a high piezoelectric coefficient (d33) of 20.8 pm V-1. The MASnI3 piezoelectric energy nanogenerator (PENG) shows an output voltage of ~ 3.8 V and an output current density of 0.35 μA cm-2. To enhance the piezoelectric output performance, the MASnI3 films are composited with an environmentally friendly PVDF polymer that had a porous structure. The PVDF-MASnI3 composite based-PENG reveals a maximum output voltage of ~ 12.0 V and current density of ~ 4.0 μA cm-2. A green light-emitting diode (LED) using the PVDF-MASnI3 PENGs is instantly lighted without need of a storage device, and long-term stability of the composite PENGs is validated for 90 days. This simple and cost-effective solution process is feasible for the fabrication of large-scale, high-performance, and environmental-friendly PENGs based on lead-free organic-inorganic perovskites to extensively implicate in medical and biomechanical applications.
关键词： Dielectric property,Lead-free MASnI3,PVDF-MASnI3 composite PENGs,Piezoelectric energy,Antisolvent-assisted collision technique
更新于2025-09-23 15:23:52
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Effect of potassium and magnesium codoping on the dielectric properties of BST powders
摘要： K and Mg codoped BST powders were prepared by a sol-gel method, and the effect of doped concentration on the dielectric performances was studied. For comparison, pure, Mg doped and K doped BST powders were studied. XRD shows all powders reveal complete diffraction peaks and ABO3 cubic perovskite polycrystalline structures. Compared to the pure BST powder, Mg doped BST powder shows a little weaker crystallization, 5%～15% K doped BST powders exhibit stronger crystallization, and the crystallization is getting stronger with increasing K doped concentrations from 2% to 15%. BST powder shows lattice parameter of 3.963 ?A, Mg doping corresponds to 3.963 ?A, 2%～20% K doping correspond to 3.963 ?A～3.967 ?A, and Mg and K codoping make lattice parameters increase from 3.967 ?A to 3.974 ?A. Mg2+ ion and K+ ion show acceptor doped mechanisms, Mg doping makes grains refine, and K doping makes grains grow. Pure BST powder and Mg doped BST powder show uniform grains with unclear grain boundaries, K doped BST powders can obtain uniform and dispersive grains with clear grain boundaries, but Mg and K codoping makes the uniformity and dispersity of the powders getting worse. Compared to pure BST powder, Mg doped BST powder shows smaller but more stable dielectric constant and dielectric loss, K doped powders tend to reveal larger and less stable dielectric constants and dielectric losses. Mg and K codoped BST powders show less than 35 dielectric constants, and lower than 0.02 dielectric losses. Dielectric properties are strongly dependent on the crystallization, doped mechanism and morphology. Mg doped and 2% Mg 2% K and 2% Mg 5% K codoped BST powders show low and stable dielectric constants and dielectric losses, thus can meet the requirements for tunable microwave applications and other applications.
关键词： dielectric property,codoping,Mg,K,BST powder
更新于2025-09-23 15:23:52
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Microwave dielectric properties of B and N co-doped SiC nanopowders prepared by combustion synthesis
摘要： B and N co-doped SiC nanopowders were prepared by combustion synthesis under a nitrogen atmosphere from the Si/C system, using α-Si3N4 powder and B powder as solid nitriding agent and dopant, respectively. The prepared particles had spherical morphology and narrow size distribution. XPS analysis demonstrated that B and N atoms successfully incorporated into SiC crystal and formed Si1-xBxC1-yNy solid solution. Results of dielectric properties showed that the real part ε′ and imaginary part ε″ of the complex permittivities of the samples decreased first, and then increased with increasing N content. The sample with 5% B and 15% N revealed the greatest values in ε′ and ε″ and better microwave absorption performance. The corresponding mechanism of the dielectric properties of SiC improved by co-doping was discussed in detail.
关键词： co-doping,SiC,dielectric property,microwave loss
更新于2025-09-23 15:21:21
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Enhanced dielectric property and energy density in poly(vinylidene fluoride-chlorotrifluoroethylene) nanocomposite incorporated with graphene functionalized with hyperbranched polyethylene- <i>graft</i> -poly(trifluoroethyl methacrylate) copolymer
摘要： Polymer film capacitors are attractive as promising candidates for potential applications in compact and efficient electric power systems. The development of a method for producing a polymer nanocomposite with enhanced dielectric property and a high energy density is a fundamental solution for electric storage in a film capacitor. In this work, a hyperbranched polyethylene-graft-poly(trifluoroethyl methacrylate) (HBPE-g-PTFEMA) copolymer was synthesized to exfoliate and functionalize graphene from natural graphite in chloroform on the basis of the CH–π non-covalent stacking between the HBPE-g-PTFEMA stabilizer and graphene. Examination of the morphologies by transmission electron microscopy (TEM) and atomic force microscopy (AFM) confirmed that the resulting graphene had a lateral size of 0.2–0.6 μm and a thickness of around 4 layers. The presence of peaks due to F in the X-ray photoelectron spectroscopy (XPS) spectra of graphene indicates that the fluorinated copolymer was attached to the surface of nanosheets. Few-layer graphene was introduced into a poly(vinylidene fluoride-chlorotrifluoroethylene) (P(VDF-CTFE)) matrix via simple solution casting. The relative content of the electroactive phase in the nanocomposite film increased because the phase transition from the α- to the β-phase was induced by the addition of graphene. The dielectric constant increased to 24.8 with a low dielectric loss of 0.06 at 100 Hz for a 0.8 vol% nanocomposite, and a released energy density of 4.6 J cm?3 with a charge–discharge efficiency of 62% at 250 MV m?1 was achieved with a 0.1 vol% nanocomposite, which was attributed to the combination of the large content of the electroactive phase and interfacial polarization. This strategy based on a nanocomposite with graphene exfoliated by a fluoropolymer sheds light on the mechanism of interfacial polarization and exhibits commendable prospects for applications in flexible film capacitors.
关键词： graphene,poly(vinylidene fluoride-chlorotrifluoroethylene),hyperbranched copolymer,nanocomposite,energy density,dielectric property
更新于2025-09-19 17:15:36