Low Loss Factor Research Articles

Impedance modulated dielectric and magnetic properties of BCT-NF multiferroic composite

Dual nature of multiferroic composites embellishes it as a promising candidate for the application in electronic industry. In this paper, we report the structural, dielectric, electrical and magnetic properties of 1-x (Ba0.96Ca0.04TiO3)-x (NiFe2O4) (BCT-NF) multiferroic composite material synthesized using the solid-state reaction method. X-ray diffraction showed the simultaneous existence of ferroelectric and ferromagnetic phase with tetragonal and spinel structure respectively. Whereby, Raman spectroscopy confirmed the existence of both phases by indicating the intense peak ranges from 566 cm−1 to 545 cm−1. Transmission electron microscopy micrograph presented the crystalline nature of all the prepared samples. Electrical analysis shows high value of ε’ with low loss factor confirming the compatibility nature of both the phases with low conductivity and minimal creation of oxygen vacancies. However, the composition x = 0.2 shows optimum dielectric and impedance properties due to the size dependency. Curie temperature was found to shift towards higher range with an increase in NF concentration. Magnetic study revealed the increasing nature of Ms and TB with increasing ferromagnetic concentration. The optimum value for TB and Ms was found to be 102 K and 36 emu/g, respectively.

A lead-free perovskite Bi1/2(Na1/4Li1/4)TiO3: investigation on structural, electrical properties, and device application

In the present era, global challenges are focused to meet the security of energy due to excessive energy demands. The coal and petroleum-based fossil fuels are soon fading out due to current energy-generating units; hence, the energy from renewable energy sources becomes an alternative medium and new scientific investment. Research is carried out to boost the efficiency of these devices. The multifunctional materials having superior properties are the need of the hour to provide insight towards producing low-cost energy devices. A perovskite having the chemical formula Bi1/2(Na1/4Li1/4)TiO3 (BNLTO) is synthesized using a solid-state reaction. The standard techniques were used to investigate the structural and electrical characterizations at various experimental conditions. The X-ray diffraction (XRD) spectra elucidated the presence of an orthorhombic symmetry in the synthesized sample. The high dielectric constant and low loss factor is evolved at various frequencies and temperatures. The Nyquist plot depicts the association of the combined effect of grain and grain boundary. The activation energies evaluated from the loss and modulus spectrum are noted as ~ 1.26 eV and 0.81 eV, respectively. The charge carriers contribute to the conduction mechanism at high temperature. Finally, a poled piezoelectric energy harvester is fabricated to check its capabilities for the conversion of small impact from hand palm into electrical energy.

Molecular Weight Enables Fine-Tuning the Thermal and Dielectric Properties of Polymethacrylates Bearing Sulfonyl and Nitrile Groups as Dipolar Entities.

In this work, polymethacrylates containing sulfonyl and nitrile functional groups were successfully prepared by conventional radical polymerization and reversible addition-fragmentation chain-transfer polymerization (RAFT). The thermal and dielectric properties were evaluated, for the first time, considering differences in their molecular weights and dispersity values. Variations of the aforementioned properties do not seem to substantially affect the polarized state of these materials, defined in terms of the parameters ε’r, ε”r and tan (δ). However, the earlier appearance of dissipative phenomena on the temperature scale for materials with lower molecular weights or broader molecular weight distributions, narrows the range of working temperatures in which they exhibit high dielectric constants along with low loss factors. Notwithstanding the above, as all polymers showed, at room temperature, ε’r values above 9 and loss factors below 0.02, presenting higher dielectric performance when compared to conventional polymer materials, they could be considered as good candidates for energy storage applications.

Low-temperature synthesis of bismuth titanate by modified citrate amorphous method

Bismuth titanate is a lead-free piezoelectric ceramic with outstanding properties that strictly depend on the composition and microstructure. However, bismuth-based materials are difficult to synthesize due to bismuth volatilisation that causes secondary phases and stoichiometry deviations. In this work, we propose a low-temperature chemical route, i.e. a modified amorphous citrate method, that allows a reduction of thermal treatment temperature, when compared with solid-state or other chemical routes, to obtain single-phase bismuth titanate samples. Single-phase powders with particle size under 300 nm are produced by calcination at 700 °C, and prepared into homogeneous dense pellets (density above 95%), with only isolated pores. The pellets show two distinctive features in the electrical behaviours directly associated with their mica-like microstructure: planar oriented boundaries are responsible for oxygen conduction, while the bulk is dominated by electronic conductivity. The samples show a high dielectric constant, around 200 at room temperature, while maintaining a low loss factor. The pellets also achieved a maximum polarisation of 5.85 μC/cm2 and an inverse piezoelectric coefficient of 7.4 pm/V. The dielectric and piezoelectric properties obtained are comparable or superior to the state-of-the-art.

One-micron-thick organic indoor light harvesters with low photocurrent loss and fill factors over 67%

A diluting strategy with insulating polystyrene is adopted in indoor light harvesters, and achieves high-performance 1-micron-thick photovoltaic device with low trap state density and a record fill factor over 67% under light-emitting diode lights.

Investigation of 2D Nano-Structured Winding Insulation for High Torque Density Medium-Voltage Motor

Since the introduction of mica paper and synthetic resin-based taping insulation for rotating-machines in 1950s, only evolutional improvements in their properties and processing have been made. Due to its challenging nature, much of recent insulation research has been focused on the aspect of reliability rather than performance enhancement. This paper presents the development and performance evaluation of a revolutionary nanostructured insulation in the manufacturing of large propulsion motors with game-changing torque density and payload efficiency for marine Next Generation Integrated Power System. It is demonstrated that nanostructured insulation based on 2D-platelet fillers could offer significant improvement over conventional insulation system in electrical, dielectric, thermal and mechanical properties. Optimal nanostructured insulation formation identified through a Design of Experiment study exhibits high thermal conductivity of >0.8 W/(m·K), high breakdown strength of >40 kV/mm, low dielectric constant of less than 5.5 and low dielectric loss factor of less than 2.5% at 155°C. Voltage endurance tests on coupons with optimal formulation, in accordance with IEC 60343 standard, demonstrate satisfactory endurance life. Furthermore, a multi-physics finite-element-analysis model of the winding in a medium-voltage electric motor is established to perform electromagnetic and thermal analyses in ANSYS under various temperature boundary conditions. The study indicates a remarkable increase of 14% in torque handling capacity of a motor wound with proposed nanostructured insulation material when compared to an identical motor wound with conventional micaceous insulation.

Using a Dielectric Capacitance Cell to Determine the Dielectric Properties of Pure Sand Artificially Contaminated with Pb, Cd, Fe, and Zn

This paper presents a new method of dielectric capacitance cell as a proposed device for measuring the impedance of pure sand artificially contaminated with four heavy metals. Dielectric constant and loss factor of clean and contaminated sand at various levels were calculated from the measured sand impedances. The advantages and benefits of using the proposed dielectric capacitance cell were its low cost, simple calculation, calibration procedures, portable and lightweight, and easy to modify the electrodes to suit testing in the field. Pure sand was saturated with water artificially polluted in the lab with Pb, Cd, Fe, and Zn at heavy metal contents 0, 7.5, 15, 22.5, and 30 mg/kg of sand. The dielectric properties of polluted sand were evaluated at a frequency range from 100 kHz to 1000 kHz. The polluted sand exhibit different dielectric constants and loss factors from the unpolluted sand. The results also indicate that the dielectric constant decreases with increasing pollution level for all heavy metals. This may attribute to the polarization mechanism change with existing heavy metal. The loss factor of sand increases with the increasing pollution level. This may be explained by the increase of ionic conductivity of pore water with heavy metal in the sand. Sand polluted with heavy metal with higher resistivity and density possess a higher dielectric constant and lower loss factor than other polluted metals. Evaluation of the dielectric characteristics of polluted sand could have the potential to monitor heavy metal pollution. Even with promising results obtained with the proposed dielectric device, it is necessary to explore several other factors affecting the measurements such as sand water content, soil texture, and type of soil. Also, testing polluted soil near industrial pollution is needed.

Structural, Morphological and Dielectric Studies of Sol Gel Derived Gd Doped SrTiO3-δ

Gadolinium doped SrTiO3-δ i.e. Sr1-xGdxTiO3-δ for various values of ‘x’ have been successfully synthesized using sol gel technique in the reported work. XRD patterns of the obtained ceramics are found to be sharp and well defined having no impurity phases for all the compositions. Lattice parameter ‘a’ decreases with increase in the amount of Gadolinium. XRD, FESEM and EDX studies confirm the formation of Sr1-xGdxTiO3-δ ceramics with required cubic structure. FESEM/EDX analysis reveals that ceramics possess high density with marginal inter-granular porosity. The dielectric studies show that the synthesized samples possess high dielectric constants, high ac conductivity and low loss factors which further improve with gadolinium doping

Acousto-optic tunable flat top filter based on one-dimensional coupled-cavity photonic crystals

In this paper, an acousto-optic tunable flat top filter is proposed by using one-dimensional coupled-cavity photonic crystal, and two kinds of materials, i.e. magnesium fluoride and tellurium dioxide, are selected. Based on the theory of acousto-optic effect, the thickness and refractive index of one-dimensional coupled cavity photonic crystal acousto-optic medium are changed by varying the ultrasonic frequency. After the parameters of acousto-optic medium are changed, the central wavelength of flat top filter of transmission spectrum shifts toward the short wave direction, thus realizing tunable filtering function. Based on the transfer matrix method and the theory of acousto-optic effect, the theoretical model of the flat top filter is established. The rectangularity, passband bandwidth, insertion loss and tunability of flat top filter are simulated by COMSOL software. The results show that the tuning effect can be achieved by applying a certain frequency of ultrasound in the case of different ultrasonic amplitudes. The decreasing trends of transmittance are basically identical in the process of changing ultrasonic frequency in the case of different amplitudes. When the central wavelength of the flat top filter increases from 1510 nm to 1514 nm, the transmissivity corresponding to the central wavelength increases sharply from 37% to 90%; when the central wavelength of the flat top filter continuously increases to 1562 nm, the transmittance corresponding to the central wavelength increasing gently from 90% to 97% in the case of different amplitudes. Considering the transmissivity required to exceed 90% in the passband of flat top filter and the cost of ultrasonic generator, the ultrasonic wave with an amplitude of 0.4 nm is selected as the research object. The flat top filter with 5–6 nm central wavelength and 1514–1562 nm tunable flat top filter can be realized by applying ultrasonic wave with the frequency in a range of 6–11 MHz. In the tunable range, the highest insertion loss is only 2.23 dB, the lowest is only 0.78 dB, and the lowest rectangularity is 1.4. In a practical flat top filter with machining error within 5 cm, the deviation of center wavelength, rectangularity, insertion loss and passband bandwidth of flat top filter are all very small. The flat top filter has the characteristics of easy design and integration, flat passband, wide tunable range, stable passband bandwidth, low insertion loss and high quality factor. It has important applications in optical communication fields such as optical switch, tunable fiber laser and fiber sensing.

Electric and dielectric behavior of carbonate intercalated CoAl-Layered Double Hydroxide (LDH) investigated by impedance spectroscopy

Cobalt-based layered double hydroxides (LDH) have invoked a great deal of interest in the field of energy storage due to their unique properties and low cost. Herein, carbonate intercalated CoAl-LDH was prepared in order to investigate the electrical and dielectric properties of this material. This polycrystalline sample was synthesized by the conventional co-precipitation method, characterized by PXRD, FT-IR and TGA, and analyzed by ICP. Ac impedance was measured by the complex impedance spectroscopy (CIS) method using pressed pellet sample over a frequency range of (1Hz-1MHz) and room temperature, to separate contribution of grains and grain boundaries to capacitance, resistance and conductivity of the sample. The adjustment of conductivity parameters by the double power law allowed the determination of σ dc. The relaxation mechanism is dominated by long range movement of charge carriers: carbonate ions and H+ protons of water molecules in the interlayer space. This material exhibits high dielectric constant values and a low loss factor at high frequencies which makes the valorization of this material may be interesting in the area of dielectrics.

Polymer Based ZnO–SiO2 Nanocomposite Flexible Sheets as High Dielectric Materials

Flexible dielectric polymer nanocomposites (NCs) with high dielectric permittivity and low loss factor have numerous applications in light emitting and storage devices. In this research work, polymer based NCs in the form of flexible sheets containing 5% ZnO and 15, 20% SiO2 nano-fillers, are synthesized by using co-precipitation method. X-ray diffraction analysis reveals the development of various diffraction planes related to ZnO and SiO2 phases confirms the synthesis of polycrystalline PB–ZnO–SiO2 NCs flexible sheets corresponding to various compositions. Morphology and compositional analysis show the uniform distribution of nanoparticles in polymer matrix with estimated elemental contents in each composition. Dielectric measurements demonstrate a sharp increase in dielectric permittivity with relatively low dissipation factor in synthesized compositions having ZnO and SiO2 nano-fillers. The static value of dielectric constant at 100 Hz is found to be 10.79 for sample having 20% SiO2 nano-fillers that is 3.4 times greater than pure PVA and it shows relatively low value of dissipation factor. The observed AC conductivity of synthesized NCs flexible sheets having 5% ZnO, 20% SiO2 nano-fillers is 2.15 × 10–5 S/m that is 3.3 times greater than pure PVA at 1 × 106 Hz. Complex impedance spectroscopy further confirms, these materials as promising candidates for better capacitive performance.

Study on High Frequency Vibrations using Statistical Energy Analysis for Different Composite Materials

Statistical Energy Analysis developed in early 1960s is used to determine the vibration response and energy levels in the structures subjected to high frequency vibrations by using statistical approach. In this work, Statistical Energy Analysis parameters like coupling loss factor and velocity response for composite plate like structures are analytically determined. Velocity response and coupling loss factor for L-shaped composite plate like structure subjected to point load have been computed for three different composite materials. Velocity response and coupling loss factors were determined and compared for the materials considered. The results show that composite materials having high specific modulus had low velocities and high coupling loss factor.

Studies on Real and Imaginary Part of Permeability for Sm–Dy Substituted Mg Ferrite

AbstractThe ferrite samples having composition Mg[(Sm)0.5(Dy)0.5]xFe2‐xO4, in which x varies from 0.05 to 0.3 in steps of 0.05 have been prepared by using combustion method. X‐ray diffraction analysis confirmed the formation of cubic spinel structure in addition of ortho‐ferrite phase due to substitution of rare earth ions. The initial permeability and complex permeability of toroid samples are calculated by measuring the values of inductance and Q‐factor. It is seen that initial permeability and real part of initial permeability increases with increase in Samarium(Sm)–Dysprosium (Dy) rare earth element in magnetium (Mg) up to x = 0.15 and thereafter it decreases. The composition Mg[(Sm)0.5(Dy)0.5]0.15Fe1.85O4 show low loss factor and initial permeability becomes higher as compared to other prepared rare earth content samples.

High flow polypropylene composites reinforced by glass filaments: Manufacturing process and property evaluations

High flow (hf)-modified polypropylene (PP) fibers and glass filaments (GFs) were made into webs, which were then laminated orthogonally and needle punched to make GF/PP-hf preforms. These preforms were then hot pressed to produce GF/PP-hf composites. Similarly, GFs and nonmodified PP were made into GF/PP composites with the aforementioned process to serve as the control group. The structure, morphology, and mechanical performances (i.e. tensile, bending, and impact strength) of GF/PP and GF/PP-hf composites were characterized and tested using differential scanning calorimeter and dynamic mechanical analysis. The test results showed that the GF/PP-hf composites are composed of reinforcing filaments at a weight ratio of 43.40% and an average length of 22.9 mm. Consequently, they had advantages of high fiber content, long fiber length, and adjustable fiber orientation. Compared to GF/PP composites, GF/PP-hf composites exhibited good dispersion of GFs in the matrices, good bonding between filaments and the matrix, and a relatively lower porosity factor of 2.92%. Moreover, the glass transition temperature and crystallinity were improved by 15.2°C and 10.42%, respectively. When the temperature was lower than 160°C, GF/PP-hf composites preserved a higher energy storage modulus and a lower loss factor. Furthermore, GF/PP-hf composites exhibited good static mechanical properties, including the tensile strength of 118 MPa, the tensile modulus of 5830 MPa, the bending strength of 180 MPa, the bending modulus of 780 MPa, and the impact strength of 33 KJ m−2, which are 30, 29.6, 78.2, 68.3, and 32%, respectively, higher than those of the control group.

Pareto‐optimal design of UHF antenna using modified non‐dominated sorting genetic algorithm II

In this study, the ultra-high-frequency (UHF) antenna for partial discharge (PD) detection is optimised to simultaneously satisfy the requirements of low return loss and high fidelity factor (FF) in the frequency band of interest by using the modified non-dominated sorting genetic algorithm II (MNSGA-II). Based on the labour division strategy, the MNSGA-II adopts an adaptive crossover and mutation possibilities instead of the fixed ones, resulting in the significant improvement of convergence rate and exploration ability. One of the Pareto-optimal solutions is presented as the authors’ proposed UHF antenna, whose performance is compared with those of both the antenna optimised by genetic algorithm and the existing wideband antennas. The experimental results show that the proposed antenna with a compact size of 0.201 λ L × 0.198 λ L realises the reflection coefficient less than −10 dB from 490 MHz to 1.52 GHz, and its FFs in the face-to-face and side-by-side scenarios are 0.897 and 0.845, respectively. Furthermore, the simulation results reveal that the high FF of antenna greatly increases the accuracy of PD source localisation. It indicates that the MNSGA-II provides an excellent solution to the multiobjective optimisation problems in antenna design.

Single photon generation and non-locality of perfect W-state

We study the generation of a single photon perfect W-state. An important aspect of this perfect W-state is that it can be used for perfect teleportation and superdense coding, which are not achievable with maximally entangled W-state. Our scheme for generation involves entanglement between various path degrees of freedom of a single photon in a compact and weakly coupled integrated waveguide system, which can be fabricated precisely with a femtosecond laser direct writing technique. These platforms are interferometrically stable, scalable, less sensitive to decoherence and ensure a very low loss factor of 0.1dBcm−1 during photon propagation, and hence are ideal for generation of a perfect W-state. In addition to generation of the single photon perfect W-state, we study its non-local properties using the theory of local elements of reality.

Physical properties and sinterability of pure and iron-doped bismuth sodium titanate ceramics

Pure (BNT) and iron-doped bismuth sodium titanate (Fe-BNT) ceramics were produced according to the formula Bi0.5Na0.5Ti1−xFexO3−0.5x, where x = 0 to 0.1. The addition of Fe2O3 enables decreasing the sintering temperature to 900 °C in comparison with 1075 °C for pure BNT, whilst also achieving lower porosities and greater densities. This is attributed to oxygen vacancy generation arising from substitution of Fe3+ onto the Ti4+ site of the BNT perovskite structure, and the resulting increase in mass transport that this enables during sintering. X-ray diffraction (XRD) analysis of Fe-BNT samples shows single-phase BNT with no secondary phases for all studied Fe contents, confirming complete solid solution of Fe. Rietveld refinement of XRD data revealed a pseudocubic perovskite symmetry (Pm-3m), and unit cell lengths increased with increasing Fe content. Scanning electron microscopy (SEM) showed that average grain size increases with increasing Fe content from an average grain size of ~ 0.5 μm in (x = 0) pure BNT to ~ 5 μm in (x = 0.1) Fe-doped BNT. Increasing Fe content also led to decreasing porosity, with relative density increasing to a maximum > 97% of its theoretical value at x = 0.07 to 0.1. The addition of Fe to BNT ceramics significantly affects electrical properties, reducing the remnant polarization, coercive field, strain and desirable ferroelectric properties compared with those of pure densified BNT. At room temperature, a high relative permittivity (ɛ′) of 1050 (x = 0.07) at an applied frequency of 1 kHz and a lower loss factor (tanδ) of 0.006 (x = 0.1) at an applied frequency of 300 kHz were observed by comparison with pure BNT ceramics.

Epoxy nanocomposites with high thermal conductivity and low loss factor: Realize 3D thermal conductivity network at low content through core-shell structure and micro-nano technology

Dielectric polymers with high thermal conductivity are very promising in the fields of aerospace and electronic device packaging. However, composites with excellent dielectric properties usually have low thermal conductivity. It is usually to fill the polymer with thermal conductivity particles to improve the thermal conductivity, but the high content of filler often reduces the mechanical properties of the polymer. In this paper, the traditional insulating polymer epoxy resin was used as the matrix, by covering the surface of silicon carbide with graphene to form a core-shell structure and co-filled with nano diamonds to achieve the preparation of high-performance epoxy resin at low content. The results showed that at the filling content of 30 wt%, the thermal conductivity of epoxy nanocomposites showed a dramatic thermal conductivity enhancement of 1263%, the energy storage modulus increased by 1.1 GPa, and the dielectric loss remained unchanged at 50 Hz. The advantages of the composite are the structural design and surface modification of the filler, which not only take advantage of its inherent advantages, but also improve the interface area with the epoxy matrix. The composite materials with excellent properties are expected to provide theoretical guidance for the application of high thermal conductivity dielectric materials.

Dielectric Spectroscopy of Hydrogen-Treated Hexagonal Boron Nitride Ceramics

Hexagonal boron nitride (h-BN) is a critical material for 2D electronic devices and has attracted considerable attention owing to its structural similarity to graphene. However, it is a dielectric and modifying its electrical properties is a challenge. Hydrogenation has been calculated as a potential method, although is rarely experimentally measured. Here, dielectric spectroscopy of hot-pressed h-BN after various hydrogen treatments has been investigated. Untreated h-BN showed a frequency independent dielectric constant (4.2±0.2) and an immeasurably low dielectric loss factor, demonstrating the ideal dielectric nature of h-BN across the 103 to 1010 Hz range. However, hydrogen plasma (H+) treatment in a microwave chemical vapour deposition (CVD) reactor amplified the complex permittivity dramatically, introducing Havriliak-Negami (HN) type dispersion (es ≈ 20 ± 2, e∞ ≈ 4.2 ± 0.2) and a percolating long range conductivity (∼ 0.32 mS/m). Annealing in molecular hydrogen (H2) at similar CVD temperatures showed minimal impact, implying that H2 diffusion is not the cause. Oxygen plasma treatment, however, removes the percolating conductivity but the Debye mechanism remains. This leads to the conclusion that the electrical conductivity of h-BN ceramics can be modified through hydrogenation, using atomic hydrogen. The potential as a tunable wide-band gap semiconductor is highlighted however for insulating dielectric substrate applications, microwave CVD may destroy these desirable properties.

Electromagnetically Induced Transparency in All-Dielectric Metamaterial of Bi-layer Asymmetric Bars

The authors demonstrate the all-dielectric-metamaterials-based electromagnetically induced transparency with low loss and high quality (Q) factor. The all-dielectric metamaterial is made up of bi-layer silicon bars. A transparency window is observed by the coupled the bright and dark modes when the asymmetry is introduced. Compared with metallic metamaterials, it avoids of the loss of ohmic damping, so that the Q factor and the window transmittance can reach 1864 and 96%, respectively.