Low Loss Tangent Research Articles

Integrated electro-optic modulator on a lead zirconate titanate-silicon nitride heterogeneous platform.

Integrated electro-optic (EO) modulators are the core components of the optoelectronic information technology, and lithium niobate is currently the most widely used crystalline thin film material; however, finite EO coefficients limit the modulation efficiency of the modulators. In this Letter, we present an integrated EO modulator using a microring resonator on the lead zirconate titanate (PZT) and silicon nitride (SiN) heterogeneous platform. The microwave attenuation is reduced by using low loss tangent and dielectric constant SiN as the electrode substrate, achieving an EO bandwidth of 33 GHz. Thanks to the high quality of the PZT film deposition and the substantial EO overlap of our structure, ultrahigh modulation efficiency with the half-wave voltage-length product of 0.7 V·cm is achieved. In addition, as a remarkable result, an 80-Gbps on-off keying signal is generated using the modulator.

Cyanate Ester/TiO2 Composites for High‐Temperature and Miniaturized Microwave Substrate Applications

High‐temperature‐withstanding TiO2‐reinforced cyanate ester composites are developed by mechanical stirring, followed by curing at elevated temperatures. The uniform dispersion of the filler is confirmed using scanning electron microscopy and electron dispersive spectroscopy. All composites, up to a filler fraction of 30 vol%, exhibit a density of more than 90% while it reduces significantly after that. A high relative permittivity of 7.6 and a low loss tangent of 0.0112 are observed for the optimally filled 30 vol%. The addition of the filler further improves the temperature‐withstanding capability of the cyanate ester matrix. Moreover, a high thermal conductivity of 0.543 W mK−1, improved hardness of 24.88 HV, ultimate tensile strength of 11.68 MPa, and a low coefficient of thermal expansion of 36.44 ppm °C−1 are also shown by the optimally filled sample. A moisture absorption of 0.072 vol% observed for the optimal filled sample comes within the limit for microwave substrate applications. Thus, the developed composites are suitable candidates for high‐temperature microwave electronic applications.

Enhanced superconducting qubit performance through ammonium fluoride etch

Abstract The performance of superconducting qubits is often limited by dissipation and two-level systems (TLS) losses. The dominant sources of these losses are believed to originate from amorphous materials and defects at interfaces and surfaces, likely as a result of fabrication processes or ambient exposure. Here, we explore a novel wet chemical surface treatment at the Josephson junction-substrate and the substrate-air interfaces by replacing a buffered oxide etch (BOE) cleaning process with one that uses hydrofluoric acid followed by aqueous ammonium fluoride. We show that the ammonium fluoride etch process results in a statistically significant improvement in median T1 by ~22% (p=0.002), and a reduction in the number of strongly-coupled TLS in the tunable frequency range. Microwave resonator measurements on samples treated with the ammonium fluoride etch after niobium deposition and etching also show ~33% lower TLS-induced loss tangent compared to the BOE treated samples. As the chemical treatment primarily modifies the Josephson junction-substrate interface and substrate-air interface, we perform targeted chemical and structural characterizations to examine materials differences at these interfaces and identify multiple microscopic changes that could contribute to decreased TLS.

Innovation and possibility of various coating materials with microwave hybrid heating

Cavitation wear is causing considerable financial losses for a range of industries, such as chemical, food processing and hydropower plants. Microwave cladding process involves the application of a coating of another material over the surface of a specific material, which offers properties beneficial for high electrical conductivity, low loss tangent and excellent thermal stability. This review article is intended to provide a basic understanding of the properties of various types of microwave cladding materials. This chapter also emphasises on the characterisation of the samples produced through the microwave cladding on various substrate materials. Furthermore, this chapter describes the potential applications of the microwave cladding process in numerous engineering and industrial sectors. Additionally, this chapter also reports the potential future technological advancements in the field of microwave cladding process.

Mechanisms of enhanced performance in Zr4+/Ta5+ codoped rutile-TiO2 ceramics via broadband dielectric spectroscopy.

Aliovalent dopant codoped rutile-TiO2 materials have garnered attention due to their excellent performance properties, characterized by low loss tangent (tanδ), high dielectric permittivity (ε'), and stable ε' over a broad temperature range. This performance is primarily due to the electron-pinned defect-dipoles (EPDDs) of the complex defects [Formula: see text]Ti3+-[Formula: see text]Ti3+BTi. Notably, the excellent dielectric properties in ZrxTa2.5%Ti0.975-xO2 (Zr-TTO) ceramics can be achieved using the traditional mixed oxide method without the EPDDs, due to the absence of A3+ (acceptor doping ions). Instead, the existence of localized free electrons and oxygen vacancies ([Formula: see text]) in Zr-TTO structures, due to doping ions and the sintering process, was confirmed by X-ray photoelectron and Raman spectroscopies. These ceramics exhibited ε'~ 2 × 104 and tanδ < 0.03 at 1kHz and 25°C in the 2.5-10%Zr-TTO samples. Moreover, all ceramics demonstrated a maximum ε' change (∆ε') of less than ±15% over the temperature range suitable for X7R and X8R type ceramic capacitors. Significantly, the change in ε' related to relative humility was calculated to be less than ±0.5% over the range of 50-95% RH, indicating the environmental stability of the dielectric properties, which is essential for capacitor applications. Investigations suggested that at least four mechanisms contributed to this system: the intrinsic effect of ionic polarization, Ti4+ · e- -[Formula: see text]- Ti4+ · e- and Ti4+ · e- - [Formula: see text] defects, interfacial polarization at insulating grain boundaries, and non-Ohmic contact between the surface sample and the metal electrode.

Estimation of relative permittivity for measuring soil texture-dependent water content by GNSS-IR

Techniques for measuring the soil moisture content (SMC) using global navigation satellite system-interferometric reflectometry (GNSS-IR) with a positioning antenna have been reported. However, conventional methods are limited to evaluating the relative change in volumetric water content in a dry range for certain soil textures. In this study, we proposed a method to measure relative permittivity using GNSS-IR and evaluated its applicability at two sites with different soil textures and moisture content. The true multipath penetration depth was obtained from the tangent dielectric suitable for the soil textures, and the apparent penetration depth affected by the relative permittivity of the soil was calculated from the signal-to-noise ratio measured by GNSS. The relative permittivity of the soil was obtained from the ratio of these values and compared with the relative permittivity of the SMC sensor. As a result, we could measure soil permittivity according to soil textures from dry to wet conditions from GNSS-IR, except when the true multipath wave penetration depth was less than 1.5 cm, at which only surface reflection occurred. Sandy soils with a low dielectric loss tangent and wet areas with small changes in the depth of penetration of electromagnetic waves are particularly suitable environments for this method.

Impact of preacidification on the functionality and insoluble calcium levels of Low-Moisture Part-Skim Mozzarella made from high-casein milk

The use of low-concentration factor ultrafiltered (LCF-UF) milk for cheesemaking has become popular in recent years. Research on using LCF-UF milk to make low-moisture part-skim (LMPS) Mozzarella manufacture is limited due to concerns about the negative impact of the higher casein content on functional properties, such as melt and stretch. Pre-acidification (PA) (reflects acid added to milk before the addition of the starter culture) has been used in low-fat and nonfat Mozzarella cheeses to lower calcium levels and improve their texture and melting properties. We explored the use of PA to reduce the insoluble calcium content of cheese (calcium that is a crosslinking material for the casein proteins) and its impact on the functionality of LMPS Mozzarella made from high casein (4.2%) milk. Seven vats of LMPS Mozzarella, with a control (no PA), 2 pH values for PA (6.40 and 6.00) and 3 different acidification methods (use of acetic, citric, or carbonic acid from carbon dioxide) were evaluated for their impact on solubilization of colloidal calcium phosphate during LMPS manufacture. Composition, proteolysis, microstructural and functional changes in the LMPS cheeses were monitored during 90 d of refrigerated storage. All cheeses had similar composition except for the cheese made with milk PA with carbonic acid, which had a lower fat-in-dry matter probably due to foaming observed in this sample during the gas sparging. The cheese made with milk PA with citric acid to pH 6.00 had the lowest amount of total and insoluble calcium compared with other cheeses at all steps during cheese manufacture and storage, likely due to the calcium chelating ability of citric acid. The cheese that was made with milk PA with citric acid to pH 6.40 had a trend of slightly lower (not significant) total and insoluble calcium during cheese manufacture compared with other cheeses that were made with milk PA to pH 6.40. The pH value in all the cheeses remained similar throughout 90 d of storage, whereas the cheese that was made with milk PA with citric acid to pH 6.00 had the lowest pH values during storage. Treatment significantly (P < 0.05) impacted instrumental hardness, the maximum loss tangent during heating, the melting temperature and the storage modulus values measured at 70°C. Proteolysis was not impacted by treatment suggesting that typical aging should occur. Cheese that was PA with citric acid to pH 6.00 initially had lower maximum loss tangent values and higher hardness, possibly due to the lower pH value of this cheese. The performance of cheeses on pizza was assessed using Sensory Spectrum® method and quantitative descriptive analysis. The PA of cheese milk with citric acid helped to reduce the insoluble Ca level and at 30 and 90 d of storage, these cheeses had lower first chew hardness, lower chewiness, and lower strand thickness values compared with other cheeses. The use of PA could help improve the functionality of LMPS Mozzarella made from milk high in casein with citric acid being the most efficient in dissolving the insoluble calcium from casein.

A multifunctional Mg2Si5Al4O18/Y2Si2O7 glass-ceramic coating for porous Si3N4 ceramic

In order to enhance the oxidation and moisture resistance of porous Si3N4 ceramics, here we design a novel Y2O3-MgO-Al2O3-SiO2 glass-ceramic coating through a straightforward scraping process followed by sintering method. The crystalline phase, water absorption, dielectric properties and high temperature resistance of the coating are evaluated systematically. The result shows that the coating obtained by sintering at 1200 °C for 30 min exhibits high density, with an approximate thickness of 88 ± 5 μm. The crystalline phases present in the coating are composed of Mg2Si5Al4O18 and Y2Si2O7. The water absorption rate of the coating is only 0.59 %, and its dielectric constant ranges from 3.3 to 3.4 in the frequency range of 2–20 GHz, with a low dielectric loss tangent below 4 × 10−3. After exposure to high-temperature (1000 °C for 30 min), no significant changes are observed in the microstructure or water absorption rate of the coating. Therefore, this study has successfully developed a multifunctional glass-ceramic coating that is moisture-proof, high-temperature resistant, and exhibits low dielectric loss.

Rheological Characterization of Genipin-Based Crosslinking Pigment and O-Carboxymethyl Chitosan-Oxidized Hyaluronic Acid In Situ Formulable Hydrogels.

The aim of this study was to develop a material capable of rapidly absorbing bodily fluids and forming a resilient, adhesive, viscoelastic hydrogel in situ to prevent post-surgical adhesions. This material was formulated using O-carboxymethyl chitosan (O-CMCS), oxidized hyaluronic acid (OHA), and a crosslinking pigment derived from genipin and glutamic acid (G/GluP). Both crosslinked (O-CMCS/OHA-G/GluP) and non-crosslinked hydrogels (O-CMCS/OHA) were evaluated using a HAAKE™ MARS™ rheometer for their potential as post-surgical barriers. A rheological analysis, including dynamic oscillatory measurements, revealed that the crosslinked hydrogels exhibited significantly higher elastic moduli (G'), indicating superior gel formation and mechanical stability compared to non-crosslinked hydrogels. The G/GluP crosslinker enhanced gel stability by increasing the separation between G' and G″ and achieving a lower loss tangent (tan δ < 1.0), indicating robustness under dynamic physiological conditions. The rapid hydration and gelation properties of the hydrogels underscore their effectiveness as physical barriers. Furthermore, the O-CMCS/OHA-G/GluP hydrogel demonstrated rapid self-healing and efficient application via spraying or spreading, with tissue adherence and viscoelasticity to facilitate movement between tissues and organs, effectively preventing adhesions. Additionally, the hydrogel proved to be both cost effective and scalable, highlighting its potential for clinical applications aimed at preventing post-surgical adhesions.

Dielectric response, non-Ohmic behaviors and humidity-sensing characteristics: Tin doping in sodium yttrium copper titanate ceramics

The impact of tin (Sn4+) doping on sodium yttrium copper titanate (Na0.5Y0.5Cu3Ti4O12) ceramics, prepared using a conventional mixed-oxide route, was thoroughly investigated in terms of microstructure, dielectric properties, electrical response, non-linear behaviors, and humidity-sensing characteristics. All sintered ceramics showed a dense micro-structure and a pure Na0.5Y0.5Cu3Ti4O12 phase without any secondary phases. The doped Na0.5Y0.5Cu3Ti4−xSnxO12 ceramics, with x = 0.05, demonstrated excellent dielectric properties, including a low dielectric loss tangent (∼0.032) and a giant dielectric permittivity (∼1.8 × 104) across a wide temperature range. Sn4+ doping improved the non-linear behaviors at 25 °C in Na0.5Y0.5Cu3Ti4O12, with a reduced dielectric loss tangent corresponding to an enhanced grain boundary (GB) response. The colossal dielectric response is attributed to the internal barrier layer capacitor model, which relates to the Schottky barrier height (ΦB) at the GBs. Notably, the ΦB values for the Na0.5Y0.5Cu3Ti4O12 ceramic increased with Sn4+ ion doping. Additionally, an in-depth study of the humidity-sensing properties of the Sn4+-doped Na0.5Y0.5Cu3Ti4O12 material revealed that the capacitance at 1 kHz increased with increasing relative humidity levels, from 30 % to 90 %, suggesting potential applications in humidity-sensing technologies.

Designing Heterogeneous Catalysts for Microwave Assisted Selective Oxygenation

AbstractMicrowave dielectric heating is an emerging technology in heterogeneous catalysis. However, catalyst design in this field is not as well developed as when conventional heating is used. In this study the selective oxidation of propene to acrolein has been used as a model reaction to understand the how the properties of bismuth mixed metal oxide catalysts can be tuned for use in microwave assisted catalysis. The role of the dielectric properties, that are crucial to enable the catalyst to be heated in the microwave electric field, were determined using cavity perturbation methods. Catalysts with a very high loss tangent reached high temperatures leading to combustion products, whereas materials with a low loss tangent could not be heated and were inactive. Bi2MoO6 and BiVO4 both showed promising performance during an initial screening and were investigated further. For Bi2MoO6, a partial substitution of molybdenum with vanadium resulted in the formation of Bi1−X/3V1−xMoxO4, with a decrease in particle size and dielectric loss tangent, and the highest rate of acrolein production was found when x=0.6 at 15 W microwave power. Higher microwave power resulted in thermal runaway which decreased the activity of the catalyst.

Synergistic effect of Ni(OH)2 and MXene nanosheets in 3D framework on the improvement of dielectric, energy storage, mechanical and thermal characteristics of polyvinylidene fluoride(PVDF) polymeric composites

This work introduces a novel method for incorporating meticulously designed nanohybrids to improve the dielectric characteristics of polymer composites. Conventional ceramic fillers have problems with dispersion even if they are good at increasing permittivity. Here, we overcome this constraint by creating nanohybrids made of MXene, polyvinylidene fluoride (PVDF), and single-layered and three-dimensional Ni(OH)2. An essential coupling agent, polyethyleneimine (PEI), fosters a robust electrostatic connection between Ni(OH)2 and superior adhesion with MXene. Using only 9.5 wt percent filler loading, we are able to achieve a low loss tangent (tan δ=0.4) at 1 kHz with a considerable permittivity improvement (ε=1000) thanks to this creative design. The nanohybrid structure's ability to promote longer interfacial contact is crucial to this enhancement. Moreover, the integrated Ni(OH)2 layer functions as a semiconductor, obstructing the passage of current through the MXene flakes and lowering conductivity overall. At a low Ni(OH)2/MXene loading of 1.5 wt%, our three-phase composites also show higher dielectric strength (248.68 MV/m). Specifically, the synergistic coupling of MXene with Ni(OH)2 provides notable increases in mechanical and thermal properties. The tensile strength and Young's modulus of these films are much higher than those of virgin PVDF and Ni(OH)2-modified composites.

High permeability and low loss easy-plane ferrites with multi-ions doped for miniaturized 5G antennas

Ferrites are the desirable candidates for antenna substrates due to their high permeability and low magnetic loss. However, such excellent magnetic properties cannot be maintained in the GHz band due to the Snoek limit. Here, we report a BaCo1.8Zn0.2Fe16O27 (CoZnW) ferrite prepared by doping multiple ions at the lattice (Zn ions) and grain boundaries (Bi/Ca/Si/V ions) of conventional BaCo2Fe16O27 (Co2W) ferrites, achieving a high permeability of 3.3, low magnetic loss tangent of 0.05, and a high figure of merit (FOM=μ′Qf = 66) at 1 GHz, which is much better compared to the previous reports. Moreover, the dimensions of the antenna deploying the multi-ions doped CoZnW are only 52 % of those deploying conventional commercial materials (Fr4) because of its high permeability and low loss. Such a high permeability is attributed to the enhanced saturation magnetization and the reduced anisotropic field achieved by Zn ions modulation. The low magnetic loss is attributed to the reduced damping of domain wall motion and the refined grain size achieved by Bi/Ca/Si/V ions modulation. Our work not only provides a promising candidate for 5G antennas but also uncovers a physical mechanism for the modulation of magnetic properties of ferrites.

Significantly enhanced dielectric properties of Ti3C2Tx MXene/MoS2/methylvinyl silicone rubber ternary composites by tuning the particle size of MoS2

AbstractTo realize the great potential of silicone rubber in advanced electronics, high dielectric constant and low loss tangent are currently pursued. Adding a third phase to conductive filler/silicone rubber composites may enhance the properties of the composites, but the appropriate particle size of the third phase is an open question. Here, MoS2 was used as the third phase to prepare the Ti3C2Tx MXene/MoS2/methylvinyl silicone rubber (VMQ) ternary composites, and the influence of different sizes of MoS2 (200 nm and 2 μm) on the dielectric performance of the composites was investigated. The dielectric constant of the Ti3C2Tx MXene/VMQ composites with 5 wt% MoS2 nanoparticles shows a 279% enhancement from 2.78 to 7.75 at 103 Hz, better than that of the Ti3C2Tx MXene‐MoS2 hybrid fillers/VMQ composites. Compared with micron MoS2, nano MoS2 can significantly enhance the dielectric performance of conductive filler/polymer composites because of shorter interparticle distances and enhanced interfacial polarization. Meanwhile, the composites exhibit low loss tangent (lower than 0.0015) and good thermal stability (up to 400°C) because of the low filling amounts of Ti3C2Tx MXene and MoS2 nanoparticles. Excellent flexibility with Young's modulus of 285 kPa and elongations break of 446% was also obtained. The design of these ternary composites greatly improves the dielectric and mechanical properties, which means that the dielectric material has a broad application prospect in modern electronics industry.Highlights High dielectric constant was gained in Ti3C2Tx MXene/5n‐MoS2/VMQ composites. The MXene/5n‐MoS2/VMQ composites exhibited excellent mechanical properties. Appropriate filler size can benefit the performance of polymer composites.

Outstanding dielectric permittivity and humidity sensitivity in (Y/Sb) co[sbnd]doped TiO2 ceramics with rapid response/recovery time

The synthesized (Y0.5Sb0.5)xTi1-xO2 (YSTO) ceramics (x=0.005 and 0.05) were investigated for their potential application in humidity sensors. The rutile phase of TiO2 for YSTO ceramics was confirmed. SEM images revealed dense microstructures, with relative densities and average grain sizes decreasing with doping concentrations. YSTO ceramics exhibited outstanding dielectric constants (ε′∼ 6.617.31×104) and low loss tangents (tanδ∼0.0190.067) at 25°C and 1 kHz. Capacitive humidity sensing properties demonstrated significant increases in capacitance with rising relative humidity (%RH) levels, with sensitivities of 165 and 386 pF/%RH. Hysteresis analysis showed narrow loops with low hysteresis error (γH∼1.4 and 2.0 %). Rapid response (∼9 s) and recovery (∼7 and 4 s) times, with stable repeatability, were observed. The presence of VO•• and SbTi• was confirmed, enhancing humidity sensing through chemical absorption reactions. This analysis underscores the potential of YSTO ceramics for humidity sensors, emphasizing the role of microstructural characteristics and induced defects in sensor performance, which is vital for the development of advanced sensing technology.

Investigation of physicochemical characteristics of Dy3+ modified ZnO nanoparticles

In this report, pristine and Dy3+ modified ZnO nanoparticles [Zn(1-x)DyxO NPs, where x = 0, 0.05, and 0.10] were synthesized using the sol–gel route, and their physicochemical characteristics were investigated. x-ray diffractograms of all the compositions possess P63mc space group depicting hexagonal crystallinity with wurtzite-type crystal structure with no signature of impurities as confirmed using the Rietveld refinement technique. The granular microstructure displayed grain growth with Dy3+ incorporation in the ZnO crystal framework and an increment in average grain size was found to be 22.83 nm for x = 0 to 36.34 nm. The optical energy band gap also increased from 3.35 eV to 3.88 eV with Dy3+ doping in the host ZnO. Dy3+ substitution inhibits the conduction in ZnO and improves the resistivity (36 Ωcm–79 Ωcm) as carrier concentration diminishes from 7.36 × 1016 cm−3 to 4.23 × 1016 cm−3. Similarly, the mean free path length for ZnO and Dy3+ doped ZnO NPs declines from 0.0301 nm to 0.0198 nm. Dielectric properties of all the compositions were investigated using an LCR impedance analyzer and it was observed that Dy3+ substitution enhances the value of the dielectric constant from 32 to 91 with a low tangent loss at 50 Hz.

Rietveld refined structural, optical and temperature dependent impedance spectroscopy of NiO–ZnO heterostructure composite: Synthesized through solid state method for high-frequency devices

Multifunctional NiO–ZnO heterostructure composite powder is economically synthesized through a solid-state route having a crystallite size of 23 (±2) nm. Chemical composition is identified through FTIR, the peak associated with Zn–O is detected at 1049 cm−1. However, the peaks detected at 870 cm−1 and 590 cm−1 show Ni–O stretching vibrations. UV-DRS technique is employed to estimate the energy band gap (Eg) around 3.18 eV. The impedance studies confirmed the presence of a non-Debye-type relaxation mechanism, electrical parameters confirm the contribution of electroactive regions i.e. grains and interfaces. An equivalent circuit model (R-CPE) is employed to measure various electrical parameters. Adiabatic small polaron hopping model is applied to estimate activation energies for Ni+2 (0.30 eV), Zn+2 (0.35 eV), and bulk (0.32 eV) respectively. The hopping length at the interface is estimated at around 0.8 Å by employing Mott's variable range hopping model. Jonscher's power law (JPL) is used to fit ac conductivity data, and conclude activation energy around 0.3 eV. The conduction mechanism through the whole frequency range (1–107 Hz) is governed by correlated barrier hopping. Various physical parameters i.e. binding energy (Wm), hopping length, and barrier height compared throughout the whole temperature range (313–393 K). The rate of increase in real permittivity at low frequency is related to the disorder of the cation at sublattices. These results deduced potential for NiO–ZnO heterostructure composite for high dielectric permittivity with low tangent loss for high energy storage applications.

Synthesis of flexible magneto‐electric polyvinyl alcohol composites using hybrid filler particles of carbon quantum dots and cobalt nano for electromagnetic interference shielding application

AbstractThe main objective of the study is to synthesis and characterization of flexible magneto‐electric Polyvinyl Alcohol (PVA) composites for Electromagnetic Interference (EMI) shielding applications, by incorporating carbon quantum dots extracted from lychee fruit husks and cobalt nanoparticles sourced from Plectranthus amboinicus. Comprehensive mechanical, dielectrical, magnetic, and shielding tests were conducted to assess the performance of these novel materials. The mechanical characteristics of the composites were assessed to gauge their flexibility and robustness. In this regard, PV4 displayed a substantial tensile strength of 68 MPa, while PV6 exhibited an enhanced shore‐D hardness rating of 47. PV6 demonstrates superior dielectric properties, including a higher dielectric constant and a lower loss tangent, which are crucial for optimizing EMI shielding efficiency. When it comes to magnetic characteristics such as magnetization, retentivity, and coercivity, the PV6 composite designation outperforms the other composites. Additionally, PV6 exhibits higher electromagnetic interference (EMI) shielding effectiveness, measuring at approximately 49.8 dB in the E band and 56.5 dB in the F band. Findings demonstrate that the integration of carbon quantum dots and cobalt nanoparticles into the matrix resulted in flexible composites with enhanced mechanical strength. The incorporation of cobalt contributed to notable magnetic properties, increasing the materials' magnetization and retentivity. The tests on electromagnetic interference (EMI) showed that the shielding effectiveness got improved. The composite materials were able to reduce interference from electromagnetic waves in the tested frequency ranges. These flexible magneto‐electric PVA composites, developed using sustainable sources such as lychee fruit husks and Plectranthus amboinicus, exhibit promising potential for EMI shielding applications in diverse industries, including telecommunications, aerospace, and electronics, where reliable interference control is essential for optimal performance and safety.Highlights Cobalt nanoparticles sourced from Plectranthus amboinicus. Carbon quantum dots are prepared from lychee fruit husks via controlled pyrolysis. High tensile strength PVA composites prepared. Highest dielectric constant of 8.2 achieved for composite PV6. Higher wave shielding up to 56.5 dB achieved in “E” band.

Effect of (Al3+/Ta5+) co-doped on dielectric properties of CdCu3Ti4O12 ceramics

In this work, dense CdCu3(Al[Formula: see text]Ta[Formula: see text]Ti[Formula: see text]O[Formula: see text] ceramics were prepared by a conventional solid phase method. The effect of Al[Formula: see text]/Ta[Formula: see text] dopants on the dielectric properties of CdCu3Ti4O[Formula: see text] ceramics was systematically investigated. Upon Al[Formula: see text]/Ta[Formula: see text] co-doping, the dielectric properties of CdCu3(Al[Formula: see text]Ta[Formula: see text]Ti[Formula: see text]O[Formula: see text] were significantly enhanced. Particularly, the CdCu3(Al[Formula: see text]Ta[Formula: see text]Ti[Formula: see text]O[Formula: see text] material displays a decent dielectric property, where dielectric constants ([Formula: see text]), loss tangent (tan [Formula: see text]) at a test frequency of 1[Formula: see text]kHz are able to satisfy the application temperature requirement of the Y6R capacitor. Surprisingly, the refined grains resulting from Al[Formula: see text]/Ta[Formula: see text] co-doping lead to heightened resistance at grain boundaries, which is closely associated with enhanced dielectric properties. Meanwhile, the giant dielectric property of the materials can be attributed to the effect of the internal barrier layer capacitance. The obtained results are expected to provide a new idea for obtaining high dielectric constant and low loss tangent in CdCTO-based materials and promote the practical application of such materials.

Stability of giant dielectric properties in co‐doped rutile TiO2 ceramics under temperature and humidity

AbstractThis research investigated the influence of temperature and humidity on the giant dielectric (GD) properties of 1% indium tin oxide and 1% Ta2O5 co‐doped TiO2 ceramics sintered at different temperatures. A single phase of rutile TiO2 was obtained in all sintered samples. The mean grain size increased with higher sintering temperatures, resulting in ceramics with a relative density exceeding 98%. A uniform dispersion of dopants and major elements was achieved. Remarkably, the dielectric constant increased significantly from 2 × 103 to 3.7 × 104 with a rising sintering temperature, primarily due to the enlarged grain size. Concurrently, the authors observed low loss tangents, ranging from tanδ≈0.016 to 0.024 at 1 kHz. Slight variations in the dielectric constant were observed with temperature from room temperature up to 210°C, while maintaining remarkably low tanδ. The GD properties were attributed to space charge polarisation at internal interfaces and defect dipoles. Further research explored the impact of environmental conditions on dielectric properties. Remarkably, the ceramics exhibited minimal capacitance variations of less than 10% within the relative humidity range of 30%–95% and temperatures from 15 to 85°C, indicating excellent dielectric stability.