Dielectric Constant Research Articles

Structures and Performance of a Polybenzoxazine with High Heat Resistance and High-Frequency Low-Dielectric Properties

Benzoxazine is a newly developed thermoset resin that has attracted significant academic and industrial interest due to its excellent properties. However, improving its dielectric performance while maintaining high heat resistant is crucial for expanding its application in 5G electronics. In this study, we designed and synthesized a novel benzoxazine monomer, DFDA-PTB, using p-tert-butylphenol (PTB) as the phenol source and furfuryl diamine (DFDA), derived from furfuryl amine, as the amine source. Two additional benzoxazines with similar structures were also synthesized for comparison. The cured product, poly(DFDA-PTB), was then analyzed to explore the relationship between its structure and properties. The results indicate that the introduction of a furan ring structure enhances thermal stability and reduces the dielectric constant. Additionally, the inclusion of tert-butyl groups further lowers the dielectric constant and dielectric loss. Simulation methods were employed to study the mechanisms behind these improvements. Poly(DFDA-PTB) demonstrated superior dielectric properties, with a dielectric constant of 2.51 and a dielectric loss of 0.0018 at 10 GHz. It also exhibited excellent heat resistance, with a char yield of 45.4% at 800 °C. These properties make poly(DFDA-PTB) a promising candidate for electronic packaging and communication applications.

Natural sucrose-assisted controllable porous PVDF-HFP films for self-powered tactile sensors with higher sensitivity

Incorporating porous structures into flexible piezoelectric materials has proven to be an effective strategy to enhance the output performance, but the fabrication processes are often intricate or environmentally harmful. In this study, natural sucrose with substantial hydroxyl groups was firstly introduced into polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) as a phase formation inducer, and subsequently removed by the dissolution of water as a pore formation agent, yielding a regular porous structure. Furthermore, porosity of the PVDF-HFP film could be simply modulated by adjusting the mass ratio of sucrose to PVDF-HFP. At low porosity levels, the dielectric constant of PVDF-HFP decreased with the increase of porosity, reaching the minimum at the critical threshold porosity of 38.8%. Owing to the increased β-phase content and the decreased dielectric constant, the sensitivity of the porous PVDF-HFP film based piezoelectric sensor was tripled to 117 mV/N, which held promise for detecting tactile and slip signals in mechanical arms.

Temperature-dependent optical and dielectric properties of polyvinyl chloride and polystyrene blends in terahertz regime

Terahertz time-domain spectroscopy (THz-TDS) has been used to study the temperature-dependent refractive index, absorption coefficient and dielectric constant of polyvinyl chloride/polystyrene (PVC/PS) blends in frequency range of 0.2–1.8 THz. Moreover, the Sellmeier and thermo optic coefficients of PVC/PS blends with different weight ratios have been explored in the temperature range of 25–80 °C. These parameters are used to evaluate the dispersion properties of these blends in the observed frequency range. A clear indication of temperature dependence on the values of refractive index and the real dielectric constant of these blends have been observed. Their values decrease linearly with increasing temperature up to 80 °C. Whereas, no noticeable change has been observed in the imaginary dielectric constant and the absorption coefficient. These results provide a database of temperature-dependent optical and dielectric parameters of PVC/PS polymer blends for their efficient utilization for device fabrication in THz technology.

High energy density and efficiency of laminated polymeric blend-based composites via introducing ultra-low content micrometer sheets

Polymeric blend-based composites are promising for dielectric capacitor due to the excellent dielectric and energy storage properties. However, the electric displacement difference (Dmax-Dr) and dielectric constant (εr) of the polymeric blend-based composites are incompatible, which further limits the improvement of the available energy densities (Ue). In this study, we propose the solution-processable laminated polymeric blend-based composites to address this challenge. The concurrent enhancement in Dmax-Dr, εr, Ue and charge-discharge efficiency (η) of designed composites is attributed to the synergistic interaction between macroscopic layered interfaces and microscopic interfaces. The laminated polymeric blend-based composites were fabricated by utilizing a blend of 50 wt% poly(vinylidene difluoride)-hexafluoropropylene (P(VDF-HFP)) and linear poly(methyl methacrylate) (PMMA) as the outer layer and P(VDF-HFP)/PMMA incorporated with an ultralow content alumina-modified strontium titanate plates (SrTiO3@Al2O3) the inner layer. As a result, laminated polymeric blend-based composite with the optimized content (0.5 vol%) delivers a maximum Ue of 14.36 J/cm3 due to highest Dmax-Dr of 7.96 μC/cm2, εr of 6.12 (1 kHz), Eb of 400 MV/m, and η of 76.6 %, outperforms those of representative polymer blend-based composites. Specially, laminated polymeric blend-based composite also exhibits the excellent energy storage reliability of different areas. Therefore, this contribution provides a viable approach to promote polymeric blend-based composites for capacitive energy storage.

Coordination, hydration, and diffusion of vanadyl cations in negatively charged polymer membranes

Charged polymer membranes that selectively transport ions are crucial for advancing electrochemical technologies for water purification, resource recovery, and energy generation/storage. Recent studies suggest that the ion selectivity trends of such membranes are due to ion dehydration at the membrane/solution interface, where ions that require less energy to shed their hydration can partition more favorably into the membrane. However, direct evidence of ion dehydration in polymer membranes at relevant conditions is scarce, with claims based primarily on correlations between ion hydration energies and membrane transport properties. The objective of this study was to investigate the electronic environment, local coordination, and hydration of vanadyl counter-ion in negatively charged membranes with broadly varying water content via x-ray absorption spectroscopy. The results highlight that vanadyl counter-ions maintain similar oxidation state, electronic state, and coordination number in the membranes as in aqueous solutions of vanadyl sulfate and that vanadyl dehydration is unlikely in these membranes. However, as the membrane water content decreases, the vanadyl diffusion coefficient decreases and the activation energy of diffusion increases. We attribute these significant changes in membrane transport properties to increased Coulombic interactions between vanadyl and the fixed charge groups, resulting from a decreased dielectric constant of the membrane, rather than to ion dehydration at the membrane/solution interface. This study represents significant progress in understanding the mechanisms that govern ion transport in charged polymer membranes over a broad range of water content, highlighting the critical role of Coulombic interactions between the fixed charges and mobile ions.

Chain-arranged Ni1-xCox micro/nano particles prepared via a magnetic field-assisted reduction for enhanced electromagnetic wave absorption

Transition metal magnetic alloys have garnered extensive interests in electromagnetic wave absorption due to the remarkable magnetic loss capacity and unique magnetism-frequency characteristics. Herein, we report a novel magnetic absorbent of Ni1-xCox micro chains that synthesized through a magnetic field-assisted reduction method. The precipitated Ni1-xCox particles could be connected and aligned during the magnetic reduction process. Due to the modified electronic structure of the Co active site by Ni, the particle size in the Ni1-xCox micro chains noticeably increases with increased x. Meanwhile, the complex dielectric constants exhibit a decreasing trend, which contributes to the improved impedance matching and higher resonance frequencies. The connected Ni1-xCox micro/nano particles not only benefit to the conductive loss, but also strengthened the polarization loss on the contacted interfaces among the particles. As a result, significantly enhanced electromagnetic wave absorption performance was obtained with the minimum reflection loss of −21.0 dB and the effective absorption bandwidth of 3.92 GHz at a thickness of only 1.35 mm. Overall, this work has demonstrated the strategy of designing aligned bimetallic absorbent, possessing great potentials in improving their microwave absorption properties.

Towards sustainable electronics: High-performance biodegradable polymer-based dielectric composite utilizing hydroxyapatite from cattle bone waste

Polymer-based film capacitors find widespread use in electronics and electrical systems, but the utilization of non-biodegradable dielectric materials contributes to excessive electronic waste. To address this issue, a biodegradable composite of hydroxyapatite (HAp) and poly (butylene adipate-co-terephthalate) (PBAT) was prepared and extensively characterized. HAp, as a filler, was synthesized via biomass-derived bone waste pyrolysis. The analyses confirmed successful HAp synthesis with high crystallinity and well-defined grain boundaries, which promote interfacial polarization and charge storage capability. The composite exhibited remarkable dielectric properties, with high dielectric constant, low dielectric loss, and good breakdown strength at low filler content. The PBAT/HAp-3 % composite showed significant energy storage density improvement (3.56 J/cm3), 43.55 % higher than pure PBAT (2.48 J/cm3), alongside enhanced mechanical properties and thermal stability. This study presents a cost-effective, eco-friendly route for next-generation high-performance disposable electronics.

Improving the distribution system capability by incorporating ZnO nanoparticles into high-density polyethylene cable materials

This paper introduces a novel insulated cable designed to enhance the distribution system’s capabilities. Accordingly, high-density polyethylene loaded with varying concentrations of zinc oxide (ZnO) nanoparticles (NPs) ranging from 0.0 to 5 wt% was prepared using the melt-blending technique. Zinc oxide (NPs) is synthesized by using sol–gel technique and their microstructure was examined by X-ray diffraction. The new insulated cable, HDPE nanocomposite loaded with 1 wt% of ZnO, demonstrates a 43% reduction in the relative dielectric constant and a 16.5% improvement in breakdown strength compared to pure HDPE. The observed changes in both the dielectric constant and breakdown strength offer several advantages in electrical applications. These benefits include a decrease in feeder current at the same loading level, mitigation of inrush transients during load switching, and a reduction in earth fault current values, particularly in unearthed distribution networks with ungrounded cables. A comparative study is conducted between the conventional insulating cable based on the original material (HDPE) and the new insulated cable incorporating ZnO nanomaterial at a ratio of 1.0 wt% of the total cable mass per unit length. This comparison utilizes data from two actual medium-voltage distribution feeders. Both actual feeders are simulated using the EMTP/ATP package. The obtained results prove the efficacy of the developed material cable (polymer doped with ZnO NPs) compared to the base material. The peak and duration of inrush current can be cut to 77.3% and 67% of their original values, respectively. The earth fault current can be reduced to 56.5% in ungrounded networks, while substation current under the normal operation can be cut to 84.3% with the same load currents.

Super High-k Unit-Cell-Thick α-CaCr2O4 Crystals.

High-dielectric-constant (high-k) insulators are indispensable components to integrate semiconductors into metal-oxide-semiconductor field-effect transistors with sub-10 nm channel length, where the equivalent oxide thickness (EOT) of high-k insulator needs to be decreased to subnanometer scale. The traditional insulators, including Al2O3, SiO2, and HfO2, fit well with the existing silicon industry but suffer from serious degeneration of insulating properties, such as large leakage currents caused by high-density borders and interface traps, when their thicknesses are reduced to a few nanometers. Here, we synthesize a high-quality nonlayered ultrathin α-CaCr2O4 crystal down to unit-cell thickness (∼1.2 nm) by an elements slow-supply chemical vapor deposition (CVD) method. The unit-cell-thick α-CaCr2O4 crystals show a super high dielectric constant of 87.34, which is over 20 times higher than that of well-known layered insulator h-BN and corresponds to an EOT below 1 nm. Furthermore, it has a high breaking strength (39 GPa) and excellent stability. This strategy can also be used to fabricate other ultrathin ternary oxides, such as high-k ultrathin FeNb2O6 crystals, demonstrating the universality of the CVD method.

Micromechanics modeling on the prediction of dielectric constant of polymer‐matrix composites considering inhomogeneity interaction

AbstractPredicting the dielectric constant of composites based on their component characteristics can accelerate the development of high‐energy storage dielectrics. In this work, to take into account the shape and interaction of randomly oriented inhomogeneities on the dielectric properties of composites, the orientation interaction model (OIM) initially used for composite stiffness prediction is adopted to predict the dielectric constant of composites. OIM applies to multi‐phase composites, and the inhomogeneities are approximated using ellipsoids in OIM. To verify the proposed model, some test data are adopted, and the model predictions match well with the test data. It is found that the inhomogeneity shape has a large influence on the dielectric constant of composites, and the influence increases with increase of the dielectric property difference between inhomogeneities and the matrix. The model captures that at the same inhomogeneity volume fraction, composites containing high aspect ratio inhomogeneities exhibit a high dielectric constant, and it shows penny‐shaped inhomogeneities perform better than cylindrical inhomogenities on increasing the dielectric constant of composites.Highlights The interaction among randomly oriented inhomogeneities is considered. Every parameter can be determined based on the microstructure of composites. The proposed model applies to multi‐phase composites.

Phase Evolution, Mechanical, and Electrical Properties of Lightweight Ceramic Prepared Using Scoria at Low Temperature

This study aimed to produce lightweight, eco-friendly ceramic materials with superior properties using natural raw materials and low processing temperatures. Five ceramic samples were fabricated using red clay and varying contents of volcanic scoria (10%, 20%, 30%, 40%, and 50%) through sintering at 950 °C for 4 h. The crystalline phases, electrical properties, porosity, and mechanical strength of all the ceramic specimens were comprehensively evaluated. It was determined that the chemical composition of the raw materials and the resulting phases significantly influenced these various attributes. The XRD analysis revealed that the ceramic samples primarily consisted of the crystalline phases gehlenite, low quartz, and anorthite, along with the minor wollastonite and hematite phases. As the scoria content was increased, the MgO and Fe2O3 concentrations also increased, leading to a reduction in dielectric constant, dielectric loss, and electric conductivity. Moreover, the porosity of samples decreases from S10 to S50 due to the increase in the percentage of scoria and this reduction in porosity led to increased bending strength. The findings of this study suggest that volcanic scoria can serve as a viable eco-friendly raw material to produce lightweight ceramics with excellent electrical and mechanical properties, presenting cost-effective and energy-efficient solutions for various applications.

Effect and mechanism of phenyl content on the electrical insulation properties of silicone rubber

AbstractSilicone rubber is widely used in reinforced insulation of cable accessories due to its good electrical insulation and weather resistance. With the continuous improvement of high voltage transmission grade, higher requirements are put forward for the electrical insulation performance. The effect and mechanism of phenyl content on the electrical insulation properties of silicone rubber are investigated by the method of combination of experiments and molecular simulations. The experimental results show that the properties of silicone rubber are improved with the increase of phenyl content. Among them, the silicone rubber composite with phenyl content of 20 wt% has the best comprehensive performance. Compared with vinyl silicone rubber, the dielectric constant at 50 Hz decreases from 3.50 to 2.95, and the breakdown strength increases by 38.03%, from 56.59 to 78.11 kV/mm. In addition, the tensile strength and elongation at break are 5.44 MPa and 456%, respectively. The molecular simulation results show that with the increase of phenyl content, the glass transition temperature increases, the mean square displacement decreases, and the free volume decreases, which macroscopically leads to the change of electrical properties of the silicone rubber material. This work has a certain guiding significance for improving the electrical properties of silicone rubber for cable accessories.

Hollow glass microsphere/polybutadiene composites with low dielectric constant and ultralow dielectric loss in high‐frequency

AbstractHigh‐frequency dielectric materials have been widely and rapidly applied in areas such as automotive radar, Internet of Things, artificial intelligence, and quantum computing. Currently, the challenge in high‐frequency dielectric materials lies in reducing the dielectric constant (Dk) and dielectric loss (Df) without sacrificing its mechanical properties. This study addresses this challenge by introducing air, as the most common “low dielectric factor,” into the polymer matrix in the form of hollow glass microspheres. Meanwhile, the reactive vinyl groups were also introduced onto the surface of the hollow glass microspheres, enabling an interfacial chemical reaction between the side vinyl groups of polybutadiene and its surface so that the organic–inorganic interface compatibility and interface peel strength are simultaneously improved. Consequently, the minimum Dk of 1.29 and Df of 0.0012 in 3–18 GHz are achieved, and the interface peel strength also reaches 0.65 N/mm. Molecular dynamics simulations, analysis of dielectric properties, and interface peel strength reveal the influence of hollow glass microspheres' morphology and chemical structure on their high‐frequency dielectric performance and adhesive strength. This paper provides effective strategies for the structural design and preparation of high‐frequency, low‐dielectric composites, contributing to the further development of next‐generation microwave communication devices towards higher frequencies and faster information transmission.

Ultrahigh Energy Storage of Twisted Structures in Supramolecular Polymers.

Polymer dielectrics possess outstanding advantages for high-power energy storage applications such as high breakdown strength (Eb) and efficiency (η), while both of them decrease rapidly at elevated temperatures. Although several strategies have been evaluated to enhance Eb and heat resistance, the discharged energy density (Ud) is still limited by the planar conjugated structure. In this study, a novel approach to manipulate polymer morphology is introduced, thereby influencing dielectric properties. A range of polyurea (PU)-based polymers are predicted from different structural unit combinations by machine learning and synthesized two representative polymers with high dielectric constants (K) and thermal stability. These polymers are combined with PI to form a twisted polymer via hydrogen bonding interactions (HNP). Both experimental results and computational simulations demonstrate the twisted structure disrupts the conjugated structure to widen the bandgap and increase dipole moment through the twisting of polar groups, leading to simultaneous improvements in both K and Eb. Consequently, HNP-20% achieves an ultrahigh Ud of 6.42 Jcm-3 with an efficiency exceeding 90% at 200 °C. This work opens a new avenue to scalable high Ud all-polymer dielectric for high-temperature applications.

Contribution of Protonation to the Dielectric Relaxation Arising from Bacteriopheophytin Reductions in the Photosynthetic Reaction Centers of Rhodobacter sphaeroides

The pH dependence of the free energy level of the flash-induced primary charge pair P+IA− was determined by a combination of the results from the indirect charge recombination of P+QA− and from the delayed fluorescence of the excited dimer (P*) in the reaction center of the photosynthetic bacterium Rhodobacter sphaeroides, where the native ubiquinone at the primary quinone binding site QA was replaced by low-potential anthraquinone (AQ) derivatives. The following observations were made: (1) The free energy state of P+IA− was pH independent below pH 10 (–370 ± 10 meV relative to that of the excited dimer P*) and showed a remarkable decrease (about 20 meV/pH unit) above pH 10. A part of the dielectric relaxation of the P+IA− charge pair that is not insignificant (about 120 meV) should come from protonation-related changes. (2) The single exponential decay character of the kinetics proves that the protonated/unprotonated P+IA− and P+QA− states are in equilibria and the rate constants of protonation konH +koffH are much larger than those of the charge back reaction kback ~103 s−1. (3) Highly similar pH profiles were measured to determine the free energy states of P+QA− and P+IA−, indicating that the same acidic cluster at around QB should respond to both anionic species. This was supported by model calculations based on anticooperative proton distribution in the cluster with key residues of GluL212, AspL213, AspM17, and GluH173, and the effect of the polarization of the aqueous phase on electrostatic interactions. The larger distance of IA− from the cluster (25.2 Å) compared to that of QA− (14.5 Å) is compensated by a smaller effective dielectric constant (6.5 ± 0.5 and 10.0 ± 0.5, respectively). (4) The P* → P+QA− and IA−QA → IAQA− electron transfers are enthalpy-driven reactions with the exemption of very large (>60%) or negligible entropic contributions in cases of substitution by 2,3-dimethyl-AQ or 1-chloro-AQ, respectively. The possible structural consequences are discussed.

Dielectric relaxation study of pyridine-n-propyl alcohol mixture using time domain reflectometry technique

ABSTRACT The Time Domain Reflectometry (TDR) technique was used to analyse the complex permittivity spectra of the Pyridine-n-propyl alcohol mixture across the concentration and temperature range of 10–25°C. The Cole-Davidson model was used to match the Pyridine- n-propyl alcohol complex permittivity spectra. The nonlinear least squares fit approach has been used to obtain the Static dielectric constant (ε0), Relaxation time (τ), Effective Kirkwood correlation factor (geff) Excess permittivity ε 0 E , Thermodynamic parameters (activation enthalpy and activation entropy), and Bruggeman factor (fB). Furthermore, the analysis of excess characteristics and the Bruggeman factor points towards the presence of hydrogen bonding between the pyridine and n-propyl alcohol molecules.

Solvent Descriptors Guided Wide‐Temperature Electrolyte Design for High‐Voltage Lithium‐Ion Batteries

AbstractLithium‐ion batteries are increasingly required to operate under harsh conditions, particularly at high temperatures above 55 °C. However, existing electrolytes suffer from inadequate thermal stability and significant interphasial side reactions. Moreover, there is a lack of clear guidelines for developing electrolytes that can withstand high temperatures. Here a solvent screening descriptor is introduced based on dual local softness and dielectric constant. The findings indicate that solvents with moderate dielectric constants and low reactivity are ideal candidates for high‐temperature electrolytes. Among the solvents evaluated, tetraethyl orthosilicate (TEOS) is identified as a suitable option and is utilized to formulate a localized high‐concentration electrolyte (TEOS‐based LHCE). Remarkably, the 1‐Ah LiNi0.8Co0.1Mn0.1||graphite pouch cell utilizing this TEOS‐based LHCE demonstrates 95.8% capacity retention after 300 cycles at 60 °C. Interphasial analysis reveals that the TEOS‐based LHCE promotes the formation of thin, uniform LiF‐rich interphases, effectively suppressing interfacial side reactions at elevated temperatures. This screening strategy not only enhances the understanding of electrolyte performance but also paves the way for high‐throughput screening of electrolytes suitable for wide‐temperature lithium‐ion batteries.

Preparation and Properties of High‐Temperature‐Resistant and Low‐Dielectric Constant Silicon‐Containing Arylacetylene Resin/SiO2 Syntactic Foams

A silicon‐containing arylacetylene resin (PSA)/SiO2 syntactic foam was prepared through a chemical foaming approach, with PSA serving as the matrix, quartz sand (QS) and nanosilica (nSiO2) acting as fillers, and their structures and properties were characterized. The results show that the incorporation of appropriate amounts of QS and nSiO2 can reduce the cell size and apparent density of the syntactic foam, and improve its heat resistance, dielectric properties and wave transmission properties. The addition of QS can increase the compressive strength of the syntactic foam, while the addition of nSiO2 decreases the compressive strength. The apparent densities of the PSA/9QS and PSA/9nSiO2 syntactic foams with 9% filler addition are 0.242 g cm−3 and 0.157 g cm−3, respectively, and the temperatures at 5% weight loss (Td5) under a nitrogen atmosphere were 692 °C and 658 °C, respectively. The dielectric constants were 1.59 and 1.25, respectively. The wave transmittance within the frequency range of 8.2–12.4 GHz was 98.5% and 96.8%, respectively. PSA/SiO2 syntactic foam can be used as a lightweight and high‐temperature‐resistant wave‐transmission material in aerospace and other fields.

Enhancing optical properties of Ba-Ni ferrite through nonmagnetic ion doping for sustainable green technologies and renewable energy applications

Barium ferrite powder was produced using a standard ceramic procedure, and its structure and optical properties were investigated. X-ray diffraction analysis (XRD) showed that the powder had a w-type hexagonal structure. The crystallite size was at approximately 35–36 nm, with bulk density and lattice constants increasing as zinc concentration rose. Conversely, X-ray density and porosity decreased with the increasing zinc concentration. This material has useful optical properties, as well as the standard ferrimagnetic properties of barium ferrite, which make it suitable for use in recording media. Ferrimagnetic behavior, which is useful for recording media, occurs because the powder's crystallites have their unit cell axes aligned. Up to the near-infrared part of the spectrum, the powder was found to have a very low absorption coefficient. Both of these properties—an arrangement that gives rise to ferrimagnetism and a corresponding low optical density—make barium ferrite very attractive for high-density recording and microwave applications. Fourier transform infrared spectra of the samples were recorded in the wavenumber range of 400–4000 cm−1 and supported the X-ray diffraction findings by confirming the idea of the formation of W-type hexagonal ferrite by the presence of two prominent peaks at 454 and 591 cm−1 in the FTIR spectra. Zinc addition was also found to enhance the optical properties of the material. The UV–VIS analysis confirms that the band gap energy of Ba-Ni ferrite was indeed reduced by zinc doping. Values decrease from 3.34 eV to 3.20 eV for direct transitions and from 2.96 eV to 2.79 eV for indirect transitions, using Tauc equation. That means that zinc doping enhances the optical properties of Ba ferrite without affecting the hexagonal structure of Ba-Ni ferrite. Moreover, key parameters of optical performance such as the dielectric constant, the extinction coefficient, the penetration depth, and the refractive index show a dramatic increase with a rise in zinc concentration. These attributes make zinc-doped Ba-Ni ferrite a promising optoelectronic material. The material also showed high absorbance in the wavelengths ranging from 334 to 338 nm, which makes it good for the solar cell applications. Overall, zinc-doped Ba-Ni ferrite is a good candidate for sustainable and renewable energy applications. Our study of the optical properties of barium ferrite up to the near-infrared part of the spectrum demonstrated that the powdered material has a very low absorption coefficient. Indeed, the combination of ferrimagnetism and low optical density makes barium ferrite particularly appealing for use in high-density recording and microwave technology applications.

Effect of binary ion substitution on the crystal structure and microwave dielectric properties of MgTa2O6 ceramics

AbstractMg1/3A11/3A21/3Ta2O6 ceramics (where A1 and A2 represent Co, Ni, or Zn) were prepared using the solid‐phase reaction route. The results of X‐ray diffraction and Raman tests showed that (Co1/2Ni1/2)2+, (Co1/ 2Zn1/2)2+, and (Ni1/2Zn1/2)2+ ions replaced Mg2+ ions in the lattice of MgTa2O6, resulting in the formation of a pure tri‐rutile structure. All three complex ions could significantly reduce the sintering temperature of the ceramics (by 150°C–200°C) and could broaden the sintering window. The large deviation (48.8%–69.2%) between the porosity corrected relative permittivity εr‐corr. and the theoretical relative permittivity εr‐theo. might be due to the overestimation of the ionic polarizability of Ta5+ by Shannon. (Co1/2Ni1/2)2+ has the most significant effect of increasing the bond energy of ceramic A–O bonds, reducing the τf value from 51 to 36 ppm/°C. In addition, the mechanisms affecting their dielectric properties are discussed based on bond ionicity (fi), full width at half maximum (FWHM) of Raman peak, and bond energy (E). Mg1/3Co1/3Ni1/3Ta2O6 ceramic sintered at 1350°C have the most excellent microwave dielectric properties: εr = 26.8, Q × f = 86,000 GHz, and τf = 36 ppm/°C.