High Dielectric Permittivity Research Articles

Simultaneously Enhancing Thermal Stable Dielectric Property and Piezoelectric Response in Lead-Free LiNbO3-Modified (K0.5Na0.5)NbO3- (BaNi0.5Nb0.5O3) System

Perovskite ferroelectic oxides with simultaneous highly thermal stable dielectric property and piezoelectric response are promising candidate for advanced energy, dielectric, and smart devices. The (1-x)[0.98[(K0.5Na0.5)NbO3]-0.02(BaNi0.5Nb0.5O3)]-xLiNbO3 (abbreviated as (1-x)KNBNNO-xLiNbO3; x = 0.00, 0.02, 0.04, 0.06, 0.08) lead-free multifunction ferroelectric ceramic is synthesized by solid-state reaction method. XRD analysis reveals that the samples exhibit perovskite structure with 0≤x≤0.06, and the second phase K3Li2Nb5O15 appears at x=0.08. The scanning electron microscopy image show that the grain size of ceramics increases from 0.65 μm to 3.58 μm with LiNbO3 content increasing. Meanwhile, the Curie temperature (TC) shifts to a higher temperature (~ 427 °C for x=0.06). A high dielectric thermal stability of ∆e/e40°C ≤ ±10%, with a high dielectric permittivity (~1400), is achieved at x = 0.06 over a wide temperature range of ~40–348 °C with d33 of ~160 pC·N−1, and a remnant polarization (Pr) of 20.5 μC·cm−2. This work shows that this multifunction material could be applied in sensor to efficiently covert both solar and kinetic energies into electricity over a wide temperature range.

Micro-Structure Modelling and Electrical Properties Analysis of PZT Matrix Ferroelectric Composites

PZT matrix ferroelectric composite is an important research topic in material science because of its many practical, industrial, and scientific applications. Materials with high dielectric permittivity are used to manufacture electronic devices, particularly capacitors and dynamic random access memory (DRAM). Therefore, the development of reliable and efficient micro models to be utilized in analyzing electrical properties can be of great value in accelerating research in this field. In this paper, a 3D microstructure model for PZT matrix ferroelectric composites has been developed and adopted the finite element method (FEM) to calculate the dielectric constant. The microscopy parameters of developed microstructure model are acquired based on the real composites from X-ray (micro-) diffraction and stereological method. The dielectric constant of different volume ratios of PZT matrix ferroelectric composites can be calculated by accurately controlling the volume of Ferrite particles. At the point of validation, the proposed approach makes visual and numeric comparisons between the morphology of the real microstructure and the model generated by the proposed technique. The simulation results by our method was essentially in agreement with experimental results in other literature. Simulation Experimental results also demonstrate that the dielectric constant of PZT matrix ferroelectric composites is significantly changed while the volume ratio of high dielectric phase particles was below 20%. PZT matrix ferroelectric composites Consequently, this method can be easily extended to composites preparation.

Comprehensive and systematic design of metal/high-k gate stack for high-performance and highly reliable SiC power MOSFET

Aluminum-based high-permittivity (high-k) gate dielectrics and suitable metal electrodes were systematically designed for advanced SiC power metal-oxide-semiconductor field-effect transistors (MOSFETs). Although electron injection into alumina (Al2O3) was significantly suppressed by nitrogen incorporation (aluminum oxynitride: AlON), gate leakage current under negative gate bias and hole trapping into the dielectrics were observed. Adding hafnium into the AlON (HfAlON) was investigated to overcome these drawbacks, and an atomic layer deposition-based method for HfAlON was developed in terms of permittivity, energy bandgap, and hole conduction under negative stressing conditions. Consequently, the reliability of metal/high-k gate stacks under both positive and negative bias temperature stresses was improved by using an optimized HfAlON gate dielectric in combination with a high work-function TiN gate electrode. Thanks to the higher permittivity of HfAlON, peak transconductance was successfully enhanced up to 3.4 times with an acceptable reliability margin in the state-of-the-art trench SiC MOSFETs by implementing a TiN/HfAlON gate stack.

Development and Characterization of Titanium Dioxide Ceramic Substrates with High Dielectric Permittivities.

Titanium dioxide substrates have been synthesized by means of solid-state reactions with sintering temperatures varying from 1150 °C up to 1350 °C. X-ray diffraction and scanning electron microscopy (SEM) where employed to investigate the crystal structure, grain size and porosity of the resulting samples. The obtained ceramics are tetragonal (rutile phase) with average grain sizes varying from 2.94 µm up to 5.81 µm. The average grain size of samples increases with increasing temperature, while the porosity decreases. The effect of microstructure on the dielectric properties has been also studied. The reduction of porosity of samples significantly improves the dielectric parameters (relative dielectric permittivity and loss tangent) in comparison to those of commercial substrates, indicating that the obtained ceramic substrates could be useful in the miniaturization of telecommunication devices.

Effects of TiO2 Addition on the Radio-Frequency Properties of the Sr2CoNbO6 Matrix

In this work, the investigation of Sr2CoNbO6–TiO2 composite, which shows interesting dielectric characteristics (low loss and high dielectric permittivity), was carried out. The Sr2CoNbO6(SCNO) system is widely applied in electro-electronic devices due to their dielectric characteristics. SCNO was synthesised via solid state reaction, and x-ray diffraction was used for structural characterisation. Impedance spectroscopy was used to characterise the material in the radiofrequency range where the real impedance of the SCNO showed high values, and the imaginary impedance showed a relaxation time. The thermo active process was studied by the Arrhenius equation in the SCNO–TiO2 composite series, which showed a considerable increase in activation energy. Nyquist diagrams showed the presence of a semicircle that was fitted using a model of the equivalent R-CPE circuit, showing a similar profile in all studied samples.

Incorporation of liquid fillers into silicone foams to enhance the electro-mechanical properties

ABSTRACT Silicone foams with and without liquid fillers (silicone oils of various types and glycerol, respectively) are synthesized and analyzed to be used as dielectric layers in capacitive sensors. A simple fabrication technique involving only four components i.e. Sylgard 184, glycerol, sodium hydroxide and ethanol is used to make these silicone foams after which they are filled with silicone oil or glycerol by soaking the foam in respective liquid. Mechanical and dielectric properties of the foams are examined. The oil reinforces the foam’s dielectric properties, softens the foam and improves its capacitive response, making it a very good dielectric material for fabricating capacitive pressure sensors. Compared to dry silicone foams, foams filled with – and swollen by – chloropropyl-functional silicone oil, show a low Young’s modulus (31 kPa), a high and stable relative dielectric permittivity of around 5, and a high capacitive response of 132% for an applied pressure of 12 kPa. The presence of oil stabilizes the soft foam and ensures that it does not buckle under high pressure.

Квантовые точки "ядро--оболочка" Ge/Si в матрице оксида алюминия: влияние температуры отжига на оптические свойства

Structures with Ge/Si nanoparticles (quantum dots) in an alumina matrix are interesting for researchers due to the combination of two main semiconductors, as well as the use of a matrix with high dielectric permittivity and strong oxygen oxygen–metal bonding. Nanoperiodic multilayer structures in the sequence substrate/Al2O3/Ge/Si/Al2O3 . . .Al2O3 (period — Al2O3/Ge/Si, the number of periods was up to 20) annealed at different temperatures were prepared in this work. It was shown that nanocrystalline particles of both Ge and Si were observed in the structures after annealing. Nanocrystal sizes and quantity were determined by the thicknesses of deposited layers and the annealing temperatures. The results obtained by various optical techniques indicate a quantum-size effect in the structures, which is confirmed by high-resolution microscopy.

Thermally stable indium based metal–organic frameworks with high dielectric permittivity

Two thermally stable In-based MOFs exhibit high dielectric behavior with wide bandgaps.

Mapping the mechanical and electrical properties of commercial silicone elastomer formulations for stretchable transducers

Elastomers for fabricating soft and stretchable transducers require high elongation at break, high dielectric permittivity, high breakdown strength and low leakage current. We map blends of commercial silicones to find optimum compositions.

Effect of High-k Passivation Layer on High Voltage Properties of GaN Metal-Insulator-Semiconductor Devices

In this paper, the GaN-based MIS-HEMTs with Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> single-layer passivation, Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /SiN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> bilayer passivation, and ZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /SiN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> bilayer passivation are demonstrated. High-k dielectrics are adopted as the passivation layer on MIS-HEMTs to suppress the shallow traps on the GaN surface. Besides, high permittivity dielectrics passivated MIS-HEMTs also show an improved breakdown voltage characteristic, and that is explained by 2-D simulation analysis. The fabricated devices with high-k dielectrics/SiN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> bilayer passivation exhibit higher power properties than the devices with plasma enhanced chemical vapor deposition-SiNx single layer passivation, including smaller current collapse and higher breakdown voltage. The Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /SiN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> passivated MIS-HEMTs exhibit a breakdown voltage of 1092 V, and the dynamic R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> is only 1.14 times the static R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> after off-state VDS stress of 150 V. On the other hand, the ZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /SiN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> passivated MIS-HEMTs exhibit a higher breakdown voltage of 1207 V, and the dynamic Ron is 1.25 times the static R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> after off-state VDS stress of 150 V.

Enhanced energy storage capability of P(VDF-HFP) nanodielectrics by HfO2 passivation layer: Preparation, performance and simulation

Flexible dielectric nanocomposites have shown great potential for electrostatic capacitors due to their excellent energy storage properties. In an effort to eliminate the disadvantages induced by the interfacial polarization of two different components in the nanocomposite, in this work, HfO2@BaTiO3 nanoparticles (HfO2@BT NPs) with core-shell structure were synthesized and used to fabricate poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP))/HfO2@BT nanocomposite films via solution casting method. The passivation HfO2 layer with high resistivity and moderate dielectric permittivity could act as a buffering barrier and alleviate the dielectric mismatch between the BT nanoparticles (BT NPs) and P(VDF-HFP) matrix. The breakdown strength (Eb) and discharged energy density (Ue) of P(VDF-HFP)/HfO2@BT nanocomposites have been substantially enhanced. The nanocomposite filled with 1 wt% HfO2@BT presents a maximum Ue of 10.7 J/cm3 at 450 MV/m, which is 36% and 59% higher than that of the pristine P(VDF-HFP) and nanocomposite filled with the same BT NPs, respectively. Meanwhile, P(VDF-HFP)/HfO2@BT nanocomposites show a charge-discharge efficiency of 72%, which is superior to most of the reported values. The possible mechanism of HfO2 layer on above performance enhancements is proposed based on both experimental analysis and finite element simulation. This work demonstrates that utilizing dielectric fillers with passivation layer might be an effective way to improve the energy storage performance of the flexible dielectric nanodielectrics.

Error Tolerant Method of Dielectric Permittivity Determination Using a TE01 Mode in a Circular Waveguide at the ${W}$ -Band

We propose a new method for the precise measurement of dielectric permittivity of ceramics and polymers at millimeter-wave frequencies that employs the TE01 mode of a circular waveguide. At higher frequencies, accurately measuring the dielectric permittivity of materials becomes extremely challenging by using the fundamental TE10 mode of a rectangular waveguide. As the frequency increases, the dimensions of the dielectric sample that has to be fit into the waveguide become very small. Therefore, small fabrication imperfections that produce air gaps between the sample and the wall of the waveguide result in significant errors during measurements. In contrast, the TE01 mode of the circular waveguide that does not have an electric field at the surface of the waveguide is insensitive to small imperfections during fabrication. We measured the dielectric permittivity in small samples of alumina (Al2O3), magnesium calcium titanate (MCT) ceramics, and Teflon placed in a circular waveguide. The results showed that the method was very robust with respect to manufacturing imperfections: when dimensions of the alumina and Teflon samples varied by as much as 10% and 20%, the differences in the computed dielectric permittivity of the alumina were only 1.26% and 3.06%, respectively, and those of Teflon were 1.98% and 2.12%. In addition, when the high-dielectric permittivity material MCT samples were deformed by 5% and 10%, the differences were just 0.04% and 0.14% each, respectively. We believe that this new proposed method is also applicable to even higher frequencies in the THz regime and at a very high relative dielectric permittivity of larger than 10.

Tuning the permittivity of tellurium dioxide by Ti substitution

Structure with the asymmetric environment of cation has a large effect on the polarization mechanism and dielectric response. In this study d0 cation, Ti4+ is introduced into asymmetric α-TeO2 to prepare TixTe(1-x)O2 (x = 0 to 0.25) by conventional solid-state method. In all the samples, it is found that the dielectric response increases relative to the parent α-TeO2. Sample with x = 0.25 forms cubic TiTe3O8 phase and shows maximum dielectric permittivity of 77. The remaining samples show biphasic nature comprising cubic (TiTe3O8) and tetragonal (α-TeO2) phase and their dielectric behaviour follows the Lichtenecker logarithmic mixing rule of composites. Structural analysis reveals that the cubic TiTe3O8 phase consists of TeO4 and TeO6 framework structure with locally strained TeO4 units compared to α-TeO2 and the Raman study complements this observation. The local strain enhances the dipolar polarizability of TeO4 unit; additionally, ionic polarizability of TiO6 unit also contributes to high dielectric permittivity in TiTe3O8.

Autonomous Self-Healing of Electrical Degradation in Dielectric Polymers Using In Situ Electroluminescence

Summary Dielectric polymers are ubiquitous as electrical insulation in electrical power systems and electronic devices. Electrical treeing is typically regarded as an irreversible degradation process of dielectric polymers subjected to high electric stresses, which significantly limits their lifespan and endangers the reliability of electronics and electrical power systems. Here, we report self-healing polymers consisting of microcapsules that are capable of completely restoring the dielectric properties as a direct response to electrical tree degradation. We design the microcapsules with a relatively higher dielectric constant than polymer matrix to guide the propagation of electrical trees. The electroluminescence generated in situ during electrical treeing of polymers triggers crosslinking of the healing agents released from the capsules to repair the electrically damaged areas under ambient conditions. Notably, the breakdown strength of the mended region is largely enhanced upon healing, which was initiated at different locations. The integration of autonomous healing capability into dielectric materials opens new avenues to smart polymers for electronics and energy applications.

High dielectric permittivity of BiFeO3–SrTiO3–CaTiO3 ternary solid solution ceramics

xCaTiO3-(0.8-x)SrTiO3-0.2BiFeO3 (x = 0, 0.3, 0.5, 0.7) ternary solid solution ceramics were prepared by a conventional high temperature sintering method. The structural and electrical properties of these ceramics were studied comprehensively. 0.3CaTiO3-0.5SrTiO3-0.2BiFeO3 ceramics show large dielectric permittivity and small variation over a broad temperature range, making it a potential candidate for high-temperature electronic applications. The origin of the large dielectric permittivity is discussed based on the contributions of both A-site and B-site cations on the polarizability of the system. The multiple cations induced local structural heterogeneity and/or random field is proposed as the reason for the thermal stability of dielectric permittivity.

Dielectric and electromagnetic interference shielding properties of high entropy (Zn,Fe,Ni,Mg,Cd)Fe2O4 ferrite

The new (Zn,Mg,Ni,Fe,Cd)Fe2O4 high entropy ferrite with average crystallite size 11.8 nm was synthesized in two stages by annealing of co-precipitated amorphous precursor. The dielectric spectroscopy confirms, that the electrical conductivity and polarization processes are associated with the mobility of electrons in the structure of ferrite. It was concluded, that the both, high frequency complex dielectric permittivity as well as complex magnetic permeability are strongly temperature and frequency dependent. The AC electrical conductivity is associated with quantum mechanical tunneling of electrons and related to the transfer of charge carriers between Fe2+ and Fe3+ ions. Moreover, the microwave absorption properties were determined. The best microwave absorption properties have been confirmed in the frequency range 1.9 to 2.1 GHz for a layer which is 0.8–1 cm thick. For this range, reflection loss (RL) is lower than −25 dB and shielding effectiveness (SE) lower than −50 dB.

Fabrication of High Permittivity Resin Composite for Vat Photopolymerization 3D Printing: Morphology, Thermal, Dynamic Mechanical and Dielectric Properties.

The formulation of a high dielectric permittivity ceramic/polymer composite feedstock for daylight vat photopolymerization 3D printing (3DP) is demonstrated, targeting 3DP of devices for microwave and THz applications. The precursor is composed of a commercial visible light photo-reactive polymer (VIS-curable photopolymer) and dispersed titanium dioxide (TiO2, TO) ceramic nano-powder or calcium copper titanate (CCT) micro-powder. To provide consistent 3DP processing from the formulated feedstocks, the carefully chosen dispersant performed the double function of adjusting the overall viscosity of the photopolymer and provided good matrix-to-filler bonding. Depending on the ceramic powder content, the optimal viscosities for reproducible 3DP with resolution better than 100 µm were η(TO) = 1.20 ± 0.02 Pa.s and η(CCT) = 0.72 ± 0.05 Pa.s for 20% w/v TO/resin and 20% w/v CCT/resin composites at 0.1 s−1 respectively, thus showing a significant dependence of the “printability” on the dispersed particle sizes. The complex dielectric properties of the as-3D printed samples from pure commercial photopolymer and the bespoke ceramic/photopolymer mixes are investigated at 2.5 GHz, 5 GHz, and in the 12–18 GHz frequency range. The results show that the addition of 20% w/v of TO and CCT ceramic powder to the initial photopolymer increased the real part of the permittivity of the 3DP composites from ε’ = 2.7 ± 0.02 to ε’(TO) = 3.88 ± 0.02 and ε’(CCT) = 3.5 ± 0.02 respectively. The present work can be used as a guideline for high-resolution 3DP of structures possessing high-ε.

CaCu3Ti4O12/In0.05Nb0.05Ti0.90O12 composite ceramics: An effectively improved method to reduce the dielectric loss tangent and retain high dielectric permittivity

CaCu3Ti4O12/In0.05Nb0.05Ti0.90O12 (CCTO/INTO) composite ceramics with volume fraction ratios of 0.9/0.1 (10 % INTO) and 0.8/0.2 (20 % INTO) were prepared via a solid-state reaction method. XRD results indicated the mixed CaCu3Ti4O12 and TiO2 phases in the CCTO/INTO composite ceramics. The lattice parameter of the CCTO phase increased as the INTO composition increased, indicating the entry of some Nb5+ and/or In3+ ions into the CCTO lattice structure. The mean grain size of the CCTO/INTO composite ceramics was smaller than that of the CCTO ceramic, demonstrating that the grain boundary mobility of the CCTO phase was decreased by the INTO particles. Improved dielectric properties were achieved with a low dielectric loss tangent (0.029-0.046) in the CCTO/INTO composite ceramics, while high dielectric permittivities (5.0 × 103-8.6 × 103) were achieved. Nonlinear J-E behavior was demonstrated in the all-ceramic samples. The dielectric and nonlinear properties of the CCTO and CCTO/INTO composite ceramics originated from an internal barrier layer capacitor effect.

Enhancing the dielectric properties of polymethyl methacrylate by using low loading graphene encapsulated styrene-butyl acrylate copolymer microspheres

With the rapid development of the electronics industry and electronic products, polymer nanocomposites with high dielectric constant and low dielectric loss will have great potential in various applications. In this work, a novel structure was obtained by absorbing reduced graphene oxide on the surfaces of styrene butyl-acrylate copolymer (rGO@SBA) microsphres through soap-free emulsion polymerization technique. Fourier-transform infrared spectrum characterization revealed the successful fabrication of rGO@SBA microspheres. SEM and TEM results indicated that rGO nanosheets were successfully loaded on the surface of SBA microspheres and the average diameter of rGO@SBA was increased to 650 nm. High dielectric permittivity rGO@SBA composites were obtained when the rGO loading was approximated to 2 wt%. The dielectric permittivity of rGO@SBA composites with 2 wt% rGO was 339 times higher than that of neat SBA. Furthermore, the electrical conductivity was also obviously enhanced. However, the dielectric loss of rGO@SBA composites was also inevitably increased. The rGO@SBA microspheres were further melt blended with polymethyl methacrylate (PMMA) matrix to obtain rGO@SBA/PMMA composites. The glass transition temperature of PMMA was increased with the content of rGO. The dielectric permittivity of rGO@SBA/PMMA composite with only 0.14 wt% rGO was increased to 15.5 at 1 kHz. On the other hand, the dielectric loss was controlled in a low level. SEM observation implied a segregated dispersion of rGO@SBA was realized in PMMA matrix. Our strategy provides a facile method to prepare high dielectric constant and low dielectric loss of rGO filled polymer composites through the fabrication of rGO encapsulated polymer microspheres.

Large energy storage density performance of epitaxial BCT/BZT heterostructures via interface engineering

We grew lead-free BaZr0.2Ti0.8O3 (BZT)/Ba0.7Ca0.3TiO3 (BCT) epitaxial heterostructures and studied their structural, dielectric, ferroelectric and energy density characteristics. The BZT/BCT epitaxial heterostructures were grown on SrRuO3 (SRO) buffered SrTiO3 (STO) single crystal substrate by optimized pulsed laser deposition (PLD) technique. These high-quality nanostructures exhibit high dielectric permittivity (∼1300), slim electric field-dependent polarization (P-E) curve with high saturation polarization (∼100 µC/cm2) and low remnant polarization (∼20 µC/cm2) through interface engineering to develop new lead-free ferroelectric system for energy storage devices. We observe an ultrahigh discharge and charge energy densities of 42.10 and 97.13 J/cm3, respectively, with high efficiency, which might be highly promising for both high power and energy storage electrical devices.