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Electric field distortion caused by space charge accumulation is one of the challenges in the development of insulating liquid immersed converter transformers and battery energy storage. This paper studies the impact of temperature and moisture content on field distortion in synthetic ester through an improved computational model incorporating the time-development permittivity of insulating liquid, and the test results indicated highly accurate simulation results of electric field distribution can be produced compared with the previous model. Charge mobility and charge density in synthetic ester were extracted from frequency dielectric spectroscopy test results, which were then used to calculate field distortion by the developed computational model. Simulation results indicated that the field distortion in synthetic ester decreases with temperature due to the enhanced permittivity caused by space charge accumulation, while it increases with moisture content due to the increased charge density from the dissociation of water. [ABSTRACT FROM AUTHOR]

High permittivity materials are required for efficient organic photovoltaic devices, and the addition of the conjugated polymer composite poly(3,4-ethylenedioxythiophen) polystyrene sulfonate (PEDOT:PSS) to dielectric polymers has been shown to significantly heighten their permittivity. The permittivity of PEDOT:PSS at the optical and microwave frequencies has been investigated, but PEDOT:PSS layers are mainly used for low-frequency device applications, where accurate dielectric property measurements are hindered by their high electrical conductivity and the problems arising from the metal-polymer interfaces. Here, we determine the complex relative permittivity ( ε r * = ε r ′ − j ε r ″ ) of PEDOT:PSS layers perpendicular to the layer plane in the 10−2–106 Hz range by combining data from the reactive energy estimations and electrochemical impedance spectroscopy, and discover that: ε r ′ at <1 Hz is ultra-high (∼106) decreasing with frequency to ∼5 at 106 Hz; the experimental data fit the Cole-Cole dielectric relaxation model by considering multiple relaxation mechanisms; PEDOT:PSS polarizes nonlinearly and ε r ′ increases with the intensity of the applied external field; low frequency ε r ′ increases with both thickness and temperature of the layer, opposite trend of temperature-dependence prevails at >103 Hz; the dielectric properties of PEDOT:PSS are highly anisotropic and the in-plane ε r ′ at 1.0 kHz is three orders of magnitude higher than the vertical ε r ′ ; and that the ε r ′ ′ decreases proportional to the reciprocal of frequency (1/f). The latter finding provides an explanation for the ubiquitous pink noise accompanying signals transmitted through organic conductor links. The described methodology can be adopted for investigations on other conjugated polymers. [ABSTRACT FROM AUTHOR]

In this study, the structural phase transitions are investigated as a function of composition and temperature for polycrystalline x (Ba 0.7 Ca 0.3)TiO 3 -(1 − x)Ba(Zr 0.2 Ti 0.8)O 3 (x = 0.40, 0.45, 0.50, 0.55, and 0.60) through a combination of Raman spectroscopy, synchrotron X-ray diffraction, and dielectric spectroscopy. The aim is to gain insight into the complex phase boundary region responsible for the excellent electromechanical properties. The results demonstrate the correlation between local site substitutions based on the stoichiometric variations to the microstructure and dielectric properties. The dielectric response has been correlated with the BCT/BZT content displaying a maximum depending on the phase content. Additionally, in situ temperature-dependent Raman, permittivity, and pair distribution function (PDF) studies were performed from −60 °C to 130 °C to highlight the structure and phase evolution. In particular, the in situ temperature-dependent Raman measurements reveal sudden discontinuities in the vibrational modes that correspond to the structural changes in the perovskite structure. Therefore, the results of the permittivity response, based on the average of a large volume, are consistent with the local structural changes obtained by other techniques. Indeed, correlations of Raman, X-ray diffraction, and PDFs obtained from synchrotron X-ray total scattering data, along with permittivity measurements allowed the identification of the discrete ferro- to paraelectric phase transitions and a more robust characterization. The rotation and distortion of the octahedral caused by oxygen displacement are driving forces behind symmetry changes and phase transitions, explaining the mechanism of polymorphic phase transition based on A- and B-site substitution. Therefore, this work provides a comprehensive understanding of temperature and composition-dependent phase transitions in BCZT. [Display omitted] • The polymorphic phase transitions in BCZT ceramics are investigated as a function of composition and temperature. • The mechanism of polymorphic phase transition is explained based on A and B site substitution. • Variations in octahedra distortion due to the Ti/Zr substitution explain the symmetry change as a function of composition. • in situ T-dependent Raman data show sudden discontinuities in the vibrational modes that agree with the phase transitions. • Symmetry in BCZT can be estimated using three-phase transition equations based on barycenter of Raman stretching mode. [ABSTRACT FROM AUTHOR]

Dielectric properties are crucial in understanding the behavior of water within soil, particularly the soil water content (SWC), as they measure a material's ability to store an electric charge and are influenced by water and other minerals in the soil. However, a comprehensive review paper is needed that synthesizes the latest developments in this field, identifies the key challenges and limitations, and outlines future research directions. In addition, various factors, such as soil salinity, temperature, texture, probing space, installation gap, density, clay content, sampling volume, and environmental factors, influence the measurement of the dielectric permittivity of the soil. Therefore, this review aims to address the research gap by critically analyzing the current state-of-the-art dielectric properties-based methods for SWC measurements. The motivation for this review is the increasing importance of precise SWC data for various applications such as agriculture, environmental monitoring, and hydrological studies. We examine time domain reflectometry (TDR), frequency domain reflectometry (FDR), ground-penetrating radar (GPR), remote sensing (RS), and capacitance, which are accurate and cost-effective, enabling real-time water resource management and soil health understanding through measuring the travel time of electromagnetic waves in soil and the reflection coefficient of these waves. SWC can be estimated using various approaches, such as TDR, FDR, GPR, and microwave-based techniques. These methods are made possible by increasing the dielectric permittivity and loss factor with SWC. The available dielectric properties are further synthesized on the basis of mathematical models relating apparent permittivity to water content, providing an updated understanding of their development, applications, and monitoring. It also analyzes recent mathematical calibration models, applications, algorithms, challenges, and trends in dielectric permittivity methods for estimating SWC. By consolidating recent advances and highlighting the remaining challenges, this review article aims to guide researchers and practitioners toward more effective strategies for SWC measurements. [ABSTRACT FROM AUTHOR]

Dielectric characterization is extremely promising in medical contexts because it offers insights into the electromagnetic properties of biological tissues for the diagnosis of tumor diseases. This study introduces a promising approach to improve accuracy in the dielectric characterization of millimeter-sized biopsies based on the use of a customized electromagnetic characterization system by adopting a coated open-ended coaxial probe. Our approach aims to accelerate biopsy analysis without sample manipulation. Through comprehensive numerical simulations and experiments, we evaluated the effectiveness of a metal-coating system in comparison to a dielectric coating with the aim for replicating a real scenario: the use of a needle biopsy core with the tissue inside. The numerical analyses highlighted a substantial improvement in the reconstruction of the dielectric properties, particularly in managing the electric field distribution and mitigating fringing field effects. Experimental validation using bovine liver samples revealed highly accurate measurements, particularly in the real part of the permittivity, showing errors lower than 1% compared to the existing literature data. These results represent a significant advancement for the dielectric characterization of biopsy specimens in a rapid, precise, and non-invasive manner. This study underscores the robustness and reliability of our innovative approach, demonstrating the convergence of numerical analyses and empirical validation. [ABSTRACT FROM AUTHOR]

In this manuscript, we examine the electrical behavior of pulse laser deposition grown epitaxial (111) oriented CuO thin films using impedance spectroscopy to understand the microscopic origin of their relaxor-like characteristics. Temperature (T) dependent variation of the real part of dielectric permittivity (ε ′) shows a relaxor ferroelectric-like anomaly with Vogel–Fulcher relation fitting well with the observed dielectric behavior, and thus, pointing toward a relaxor ferroelectric nature of the CuO thin film. However, the loss tangent and frequency-dependent dielectric spectroscopy measurements suggest the need to further explore the different mechanisms to understand the origin of observed relaxor behavior. Deconvolution of the impedance spectra reveals that interfacial contributions dominate in the dielectric response. Moreover, deconvoluted capacitances are temperature-independent within the specified temperature range, thereby excluding the possibility of a ferroelectric transition suggested by ε ′ v s T data. The DC bias measurement of dielectric permittivity and I–V measurements reveal the MW (Maxwell–Wagner) nature of the observed dielectric anomaly. The measurements also suggest interface-limited Schottky conduction as the predominant conduction mechanism in the CuO thin films. This work demonstrates that the apparent relaxor behavior observed in the CuO thin film is related to extrinsic, i.e., interfacial polarization effect, instead of the intrinsic ferroelectric nature of the material. [ABSTRACT FROM AUTHOR]

Purpose: Radio frequency (RF) technology relies on the electromagnetic properties of the materials used, which includes their complex permittivities and loss tangents. To measure these properties, techniques for material characterization such as the transmission/reflection method are used in conjunction with conversion techniques to calculate these values from scattering parameters. Unfortunately, these techniques rely on relatively expensive rectangular waveguide adaptors and components, especially if testing over large frequency ranges. This paper aims to overcome this challenge by developing a more affordable test equipment solution based on additively manufactured waveguide sections. Design/methodology/approach: To evaluate the effectiveness of using additively manufactured waveguides to perform electromagnetic characterization with the transmission/reflection method, samples of PLA Tough with varying infill percentages and samples made from several Formlabs photopolymer resins are fabricated and analyzed. Findings: Results show that the method yielded permittivity and loss tangent values for the measured materials that generally agree with those found in the literature, supporting its credibility. Originality/value: The accessibility of this measurement technique will ideally allow for more electromagnetic material characterization to occur and expand the possible use of additive manufacturing in future RF designs. This work also provides characterization of several Formlabs photopolymer resins, which have not been widely analyzed in the current literature. [ABSTRACT FROM AUTHOR]

We proposed a newly devised method for measuring the complex permittivity of high-loss materials at the millimeter wave frequency range. In this paper, we employed a geometrical gap between samples, which allows us to evaluate the complex permittivity of high-loss materials. By introducing this gap, we obtain a characteristic shape of the transmittance, which enables us to fit the data and obtain a more precise complex permittivity value. The proposed method has been supported by experimental results with a very low error bar compared to the existing fundamental transmission line method. We measured diverse samples including alumina, Teflon, Vero family, and AlN-SiC, and confirmed that the proposed gap method achieves much higher precision than the existing method by 3 to over 10 times. Particularly for high-loss materials like the AlN-SiC sample, the average error of the relative permittivity evaluated by the existing transmission line method is 2.05% whereas the error by the proposed method is 0.05%. Moreover, the average error of the loss tangent measured by the existing method and the suggested method is 1.85% and 0.3%, respectively, which confirms the superiority of the proposed method. [ABSTRACT FROM AUTHOR]

A simple and effective method for the determination of complex permittivity of dielectric materials at microwave frequencies using a Broadside Coupled Split Ring Resonator (BCSRR) metamaterial structure is presented. A single BCSRR unit cell placed between the transmitting and receiving probes of a Vector Network Analyzer (VNA) is used as the test probe. Resonance frequencies and bandwidths of transmission curves, measured with and without the sample placed over the BCSRR test probe, are used to determine the real and imaginary parts of the complex permittivity by treating the BCSRR as an LC resonant circuit. Relevant equations connecting equivalent capacitance and resonance frequencies are derived from the basic equivalent circuit parameters of the BCSRR through a quasi-static analysis by considering the fringing fields in its vicinity, especially on the top and bottom. Accuracy of the theoretical formula derived for determining the complex permittivity using the BCSRR is verified through experiments and simulations. [ABSTRACT FROM AUTHOR]

The solution-based casting method fabricates the free-standing pure PVDF-TrFE, PVDF-TrFE-Nafion blended films and tests them for structural, morphological, and microwave studies. The X-ray diffraction pattern and FTIR spectrum confirmed the formation of the ferroelectric β-phase of PVDF-TrFE. The surface morphology of blended films is studied by scanning electron microscope (SEM), and noticeable changes in the morphological features are observed in the blended films resulting from the differences in the nucleation process in these films. Then using the open-ended coaxial probe method, the complex permittivity measurements were carried out over a large frequency range, from 0.5 GHz to 50 GHz. These results were verified with the Transmission-Reflection method using a rectangular waveguide in the X-band and Ku-band frequency range. The microwave absorption properties of the blends are also studied in the same frequency range. The stability of the dielectric properties and low microwave absorption indicates that the blending of PVDF-TrFE with Nafion results in a new potential material for high frequency flexible capacitor applications. [ABSTRACT FROM AUTHOR]

This paper reports the results of numerical modeling of wave reflection coefficient behavior of the metal-dielectric metasurface at microwaves that can be used for biomedical applications. The study includes optimization of the working parameters of the metasurface-based structure as a sensitive element of a microwave sensoring systems for determination of proteins concentration in different solutions. In the current research a unit with the geometry, which is similar to the geometry of one well of the standard 96-multiwell laboratory microplate, is used as a resonant metasurface unit cell and liquid-holding structure. Human serum albumin (HSA) is used as a protein specimen in our model study. The present numerical modeling is based on the results of our previous experimental measurements of complex permittivity values of HSA water solutions and its biochemical reaction mixtures using microwave dielectrometry method and the developed setup. The unit cell approach calculations are performed by COMSOL Multiphysics software. The optimization of working parameters of the metal-dielectric metasurface structure with tested solutions allow us to observe the resonance effects of the wave reflection coefficient in the microwave range. We can determine the HSA concentration changes in water solutions and enzymatic reaction mixtures by the resonance frequency shift of the wave reflection coefficient of the metal-dielectric metasurface. Developed metal-dielectric metasurface-based structure demonstrates prospects to be used as a sensitive element of microwave sensors for proteins concentration determination with biomedical purposes. [ABSTRACT FROM AUTHOR]

In this manuscript, a microwave resonance sensor (MRS) was presented composed of interdigital structure, meander structure, chandelier‐form, and T‐shaped structure. The combination of four structures results in a good electromagnetic field strength at the sensing location. It caused increased sensitivity. Due to the high use of methanol in industry, samples have been selected from this material. The samples used are methanol and water solution and place on location sensing. For measurement was used samples with 80% methanol with a permittivity of 59%–10% methanol with a permittivity of 77. Also, tissue samples including sheep, chicken and fish have been used to measure the proposed sensor. The resonance frequency of the samples changes in the range of 2.14‐1.46 GHz. The sensitivity of the presented MRS is 2.6% and the Q‐factor is 1252. [ABSTRACT FROM AUTHOR]

With the increasing use of traditional and new models of wireless communication systems, the study and determination of the electrical characteristics of materials used in civil construction is an important topic to establish an understanding of how the radio frequency signal behaves inside built environments. This study presents an extensive process of characterization of electrical parameters of plaster blocks used in the construction of walls. Different from the literature where a prior estimation of the data occurs to enable sampling parameters to be obtained, this work proposes an innovative way of obtaining them entirely based on the analysis of the material through frequency measurements, which results in a greater level of precision of the data results. Analyses are made in the frequency range from 0.7 to 5.2 GHz, which has been used for several wireless communication standards. To carry out the electrical characterization of dielectric materials, a non-invasive methodology is proposed based on an innovative combination of the Nicolson–Ross–Weir Method (NRW) and the Ray Tracing Method. Through the proposed methodology and an extensive campaign of measurements using frequency scanning equipment, calculated and experimental data of Shielding Effectiveness (SE), complex relative electrical permittivity, loss tangent, attenuation coefficient and conductivity were obtained for a wide range of frequency, considering different samples of plaster blocks. The obtained results are compared to those available in the related literature, confirming the accuracy of the proposed analysis. [ABSTRACT FROM AUTHOR]

Permittivity is an important aspect of the design of microwave devices. In order to design microwave devices that are more suitable for the excitation of air plasmas, this paper presents a method for the on-line measurement of the relative permittivity of an atmospheric pressure air plasma with 2.45 GHz microwaves. First, a ridged waveguide is designed and constructed to excite the air. Using the ridged waveguide, the plasma can be excited and measured simultaneously. An artificial neural network trained with simulated data is integrated into the system to invert the dielectric constant of the air plasma being measured. At a power of 786 W and an airflow rate of 1250 L/h, the real and imaginary parts of the permittivity are obtained to be −1244 and 60, respectively. The forecasted errors on the real part and the imaginary part of the relative permittivity are kept at around 5% and 3%. The Drude model is used to construct a relationship between the electronic and dielectric properties. This diagnostic method is simple to operate and has a high degree of generality. It should be useful in the design of microwave plasma devices and can greatly improve the efficiency of microwave plasma equipment. [ABSTRACT FROM AUTHOR]

Designing a low-cost, compact, yet sensitive planar microwave sensor for complex permittivity measurement is highly desired for numerous applications though quite challenging. Here, in this research, an ultrasensitive planar microwave sensor is proposed which is based on an electric LC structure. The core sensor was fabricated on an FR-4 substrate using a simple fabrication process, then integrated within a polymethylmethacrylate microfluidic channel for straightforward liquid delivery to the sensing region. The resonance frequency of the bare sensor was designed to occur at 4.14 GHz while empty and shifted to 0.88 GHz when deionized water flows into the channel. The sensor response has been characterized for different mixture ratios of methanol and ethanol with deionized water. Next, the complex permittivity of the resulted binary mixtures has been extracted by the Debye model through a least square fitting method. The calculated average sensitivity is 1.45% which stands above most of sensors reported in the literature. Besides, the sensor has a small footprint with dimensions of 3.6 × 3.8 mm 2 making it a suitable candidate for integration with point-of-care testing devices. [ABSTRACT FROM AUTHOR]

• Permittivity and permeability of lunar simulants important to NASA were measured at 2.45 GHz. • A temperature range of −185 °C to 250 °C was investigated. • The simulants JSC-1A, NU-LHT-4 M, NUW-LHT-5 M, CSM-LHT-1G were studied. • Pyroxenite and anorthosite from the Stillwater mine, Montana, and synthetic glass were measured. • For a single simulant a linear relationship between sample density and permittivity is suggested. Lunar simulants are used to approximate the behavior of the lunar regolith. This work focuses on materials responses relevant for microwave heating to inform in-situ resource utilization of lunar regolith for landing pads and building infrastructure. Microwave dielectric permittivity and magnetic permeability measurements have been made for the first time on several new highland lunar simulants (NU-LHT-4M, NUW-LHT-5M and CSM-LHT-1G). One mare lunar simulant (JSC-1A) is included in this work. We present these measurements in the low temperature range −185 °C to 250 °C and in the frequency range 50 MHz to 3 GHz. The dominant minerals in the simulants are the minerals bytownite, ortho- and clino-pyroxenes, olivine, and glass. Less complex rock feedstocks for highland simulants, anorthosite and pyroxenite, were also measured separately. The dielectric measurements were performed on samples having different densities. Differences in the dielectric responses were noted, however all simulants were weak microwave absorbers at the low temperatures. This data assists with planning for a hybrid approach to microwave sintering at the lunar south pole. [ABSTRACT FROM AUTHOR]

Ground-penetrating radar (GPR) has been widely used in estimating the permittivity of mediums. The radar echo amplitude method is an important method used by GPR in this estimation, the basic step of which is to deduce the magnitude of the permittivity according to the relationship between the reflection coefficient and the permittivity. Based on the basic principle of the radar echo amplitude method, this paper proposes a full-wave inversion real-time permittivity estimation method that can be used for stepped-frequency GPR (SFGPR), which offers high efficiency, accuracy, and generalization ability. The characteristics of this method are mainly reflected in the following four aspects: Using the SFGPR system and introducing a layered media detection model, we can complete waveform compensation optimization with high precision. The distance between the antenna and the surface of the reflective medium is extracted from the time domain waveform without manual measurement, avoiding human measurement errors. The inversion of the total reflection waveform at the required height works under the principle of an electromagnetic field, eliminating the need for repeated metal plate calibration experiments and improving work efficiency and waveform accuracy. In a continuous measurement line, the total reflection waveform inversion on each measurement point can be efficiently completed, and the change of permittivity on the measurement line can be obtained. To evaluate the feasibility of the proposed method, we performed experiments on a wall of known thickness, and the permittivity estimation was basically consistent with that of the dielectric probe, physical model calculation, and wall penetration. We also successfully applied this method to the dielectric property analysis of adobe samples. The results indicate that the proposed method can help grasp the condition of a measured medium, which can ensure the accuracy of detection and improve subsequent data processing efficiency. [ABSTRACT FROM AUTHOR]

The article presents a study into the measurement of dielectric parameters of materials. The study aims to examine promising high-precision methods for measuring the complex permittivity of low-loss materials within the decimeter wavelength range and a non-resonant method for measuring the dielectric parameters of materials characterized by increased dielectric losses. For measuring the complex permittivity of low-loss materials within the decimeter wavelength range, a resonance method of measurement in a coaxial resonator with an adjustable capacitive gap and a method of measurement in a dielectric-filled H011 cavity resonator were developed. In order to measure increased dielectric losses of 10−2–10−1, a transmission line technique was developed using a non-resonant measuring transducer on the basis of a shielded dielectric waveguide, the specimen to be analyzed. The developed methods are applied in GET 110-2023 State Primary Standard for the units of complex permittivity within the frequency range of 0.1–178.4 GHz. The frequency range of the standard is 0.1–178.4 GHz; the reproduction range of relative permittivity is 1.2–500; and the reproduction range of dielectric loss tangent is 10−8–10−1. GET 110-2023 can be used to provide metrological support for dielectric control in the production of radio frequency cables, telecommunication equipment, electronic components, etc. [ABSTRACT FROM AUTHOR]

Microwaves (MWs) are an emerging technology for intensified and electrified chemical manufacturing. MW heating is intimately linked to a material's dielectric permittivity. These properties are highly dependent on temperature and pressure, but such datasets are not readily available due to the limited accessibility of the current methodologies to process-oriented laboratories. We introduce a simple, benchtop approach for producing these datasets near the 2.45 GHz industrial, medical, and scientific (ISM) frequency for liquid samples. By building upon a previously-demonstrated bireentrant microwave measurement cavity, we introduce larger pressure- and temperature-capable vials to deduce temperature-dependent permittivity quickly and accurately for vapor pressures up to 7 bar. Our methodology is validated using literature data, demonstrating broad applicability for materials with dielectric constant ε' ranging from 1 to 100. We provide new permittivity data for water, organic solvents, and hydrochloric acid solutions. Finally, we provide simple fits to our data for easy use. [ABSTRACT FROM AUTHOR]

Electromagnetic wave refraction and reflection at the interface between vacuum and lossy metamaterial with zero real part of permittivity are analytically described by macroscopic classical electrodynamics. The analytical model is based on exact solutions of electromagnetic boundary problems. We have good reason to believe that in lossy metamaterial with zero real part of permittivity, the values of the magnetic field and energy flow are nonzero due to the crucial role of losses in epsilon-near-zero metamaterials. It is shown that the significant transmission of waves occurs for almost all incident angles. Moreover, the transmission coefficient increases with increasing loss for TE and TM wave polarizations. Numerical results are presented to show that the optical characteristics of waves at the interface of the metamaterial are highly sensitive to the losses and polarization of waves. The effect of the losses is most pronounced for transverse electric waves. The main contribution of this article is the characterization of the role of losses in the optical properties of epsilon-near-zero metamaterials that differs from some analogs known in the literature. [ABSTRACT FROM AUTHOR]

We propose new optical dispersion models to describe the imaginary part of the electrical permittivity of dielectric and semiconductor materials in the fundamental absorption region. We work out our procedure based on the well-known structure of the semi-empirical Tauc–Lorentz dispersion model and the band-fluctuations approach to derive a five-parameter formula that describes the Urbach, Tauc and high-absorption regions of direct and indirect semiconductors. Main features of the dispersion models are the self-consistent generation of the exponential Urbach tail below the bandgap and the incorporation of the Lorentz oscillator behavior due to electronic transitions above the fundamental region. We apply and test these models on optical data of direct (MAPbI3, gallium arsenide and indium phosphide), indirect (gallium phosphide and crystalline silicon), and amorphous hydrogenated silicon semiconductors, accurately describing the spectra of the imaginary part of the electrical permittivity. Lastly, we compare our results with other similarly inspired dispersion models to assess the optical bandgap, Urbach tail and oscillator central resonance energy. [ABSTRACT FROM AUTHOR]

DyScO3 (DSO) is an attractive substrate on which to grow epitaxial thin films with extraordinary materials physics. However, its highly anisotropic permittivity makes some measurements exceedingly difficult: For instance, its permittivity tensor has not yet been fully characterized at millimeter-wave frequencies. While there are methods to characterize anisotropic permittivity at millimeter-wave frequencies, there are very few methods those are suitable for the small lateral dimensions that DyScO3 can be grown in. To overcome this lack in the material characterization, we tested an on-wafer method based on coplanar waveguides to measure the full anisotropic permittivity tensor from 0.1 to 110 GHz. We characterized two orthogonal sets of coplanar waveguides fabricated on each of two substrates with (001) and (110) crystallographic orientations to resolve the full permittivity tensor. To validate our measurements, we compared our results to data from dc parallel plate capacitors and THz time-domain spectroscopy. Our measurements fill the need for measurements of the permittivity of DyScO3, while the methodology, more generally, enables quantitative characterization of anisotropic dielectrics. [ABSTRACT FROM AUTHOR]

Simple Summary: Meningiomas are the most common primary central nervous system tumors, and surgery is their primary treatment of choice. The surgical intervention aims for the maximum extent of tumor resection whilst preserving the brain's neurological functions. The effectiveness of such intervention thus depends on the capability to intraoperatively discriminate between the meningioma tissue and the surrounding brain white matter and gray matter. This study investigated dielectric contrast as a potential physical biomarker for meningioma discrimination. Dielectric contrast is based on the difference in complex permittivity, a physical property of tissues, measurable by dielectric spectroscopy. This study shows that the dielectric contrast is relevant as a potential physical biomarker to discriminate the meningioma tissue from the surrounding brain tissues. Such a biomarker has a meaningful potential to make a positive impact on the management of neurooncological patients in terms of intraoperative tumor discrimination, as well as future diagnostic or therapeutic applications. The effectiveness of surgical resection of meningioma, the most common primary CNS tumor, depends on the capability to intraoperatively discriminate between the meningioma tissue and the surrounding brain white and gray matter tissues. Aiming to find a potential biomarker based on tissue permittivity, dielectric spectroscopy of meningioma, white matter, and gray matter ex vivo tissues was performed using the open-ended coaxial probe method in the microwave frequency range from 0.5 to 18 GHz. The averages and the 95% confidence intervals of the measured permittivity for each tissue were compared. The results showed the absence of overlap between the 95% confidence intervals for meningioma tissue and for brain white and gray matter, indicating a significant difference in average permittivity (p ≤ 0.05) throughout almost the entire measured frequency range, with the most pronounced contrast found between 2 GHz and 5 GHz. The discovered contrast is relevant as a potential physical biomarker to discriminate meningioma tissue from the surrounding brain tissues by means of permittivity measurement, e.g., for intraoperative meningioma margin assessment. The permittivity models for each tissue, developed in this study as its byproducts, will allow more accurate electromagnetic modeling of brain tumor and healthy tissues, facilitating the development of new microwave-based medical devices and tools. [ABSTRACT FROM AUTHOR]

The AC electrical properties of EVA- and NBR-based composites filled with different conductive fillers were investigated. Result shows several magnitudes of increment in AC electrical conductivity and dielectric permittivity after the addition of these conductive fillers, indicating that these materials can be used as supercapacitors. The magnitude of increment was varied according to polymer and filler types. Herein, we also have tested the applicability of different sigmoidal models to find out the percolation threshold value of permittivity for these binary polymer composite systems. It is observed that except sigmoidal–Boltzmann and sigmoidal–dose–response models, other sigmoidal models exhibit different values of percolation threshold when considered for any particular polymer composite system. The paper discusses the variation in results of percolation threshold with an emphasis on the advantages, disadvantages and limitations of these models. We also have applied the classical percolation theory to predict the percolation threshold of permittivity and compared with all the reported sigmoidal models. To judge the unanimous acceptability of these models, they tested vis-à-vis the permittivity results of various polymer composites reported in published literature. To comprehend, all the models except the sigmoidal–logistic-1 model were successfully applicable for predicting the percolation threshold of permittivity for polymer composites. [ABSTRACT FROM AUTHOR]

Both in houses and offices, so many RF devices such as microwave ovens and wireless communication equipment are occupying the environment, and most of them are working in S-band. It is being discussed in the literature that, emitted electromagnetic waves from these devices have negative effects especially both on the elderly and children in the long term. That's why human RF exposure analysis of the radiation caused by the devices and investigation of electromagnetic field suppression techniques using natural materials become inevitable. The dielectric properties of the construction materials such as marbles can be ideal for exploration in the field of biomedical engineering and the construction industry. Specific absorption rate (SAR) is a vital parameter for exposure analysis. This paper investigates the potential usage of marbles to suppress electromagnetic fields in terms of human exposure in S-Band. All in S-band; the first step is to determine and prepare a pre-selection chart for widely used 14 different types of marble and then making an estimation on the specific absorption rate by simulation in human muscle with equivalent tissue properties. [ABSTRACT FROM AUTHOR]

Understanding the mechanisms contributing to dielectric properties of glasses is critical for designing new compositions for microwave frequency applications. In this work, dielectric permittivity was measured using a cavity perturbation technique at 10 GHz for a series of niobiosilicate glasses with the compositions (100‐2x)SiO2‐ xNb2O5‐ xLi2O where x = 32.5, 30, 25, and 15 mol%. Permittivity measurements and glass compositions were used to calculate the polarizability of each cation‐anion unit in the glass network using the Clausius‐Mossotti equation. The SiO2 polarizability in niobiosilicates was calculated to be 6.16 Å3, which is much higher than the SiO2 polarizability in fused silica glass (5.25 Å3), alkali modified silicates (5.37 Å3), and aluminosilicates (5.89 Å3). The increasing trend in SiO2 polarizability is attributed to the disruption in the connectivity of the SiO4 tetrahedral network as it accommodates different network formers. The high SiO2 polarizability of 6.16 Å3 accurately predicts measured dielectric permittivity when Nb2O5 = 25, 30, and 32.5 mol%, but overpredicts measured permittivity when Nb2O5 ≤ 15 mol%, which is attributed to a decrease in SiO2 polarizability as the percentage of corner sharing SiO4 tetrahedra with NbO6 octahedra goes down. This work demonstrates that SiO2 polarizability depends on chemistry and connectivity of the glass, which has important implications in designing glass compositions for microwave frequency applications. [ABSTRACT FROM AUTHOR]

Summary: The RLCG parameters model and one‐port measurement model of the closed‐double ring electrodes have been established to obtain the dielectric properties of two‐layer medium in radio frequency. The accuracy of these models was verified by electromagnetic simulation experiments and the permittivity measurement experiments under 160 MHz. Results showed that (1) When the medium dielectric constant εr∈6.03,78.8, the calculation values based on the models and the real values, have a determination coefficient Rspc2=0.98 using the quadratic regression function fitting; (2) the effective sensing depth of the ring electrodes was about the structural wavelength of the ring electrodes; (3) the measuring permittivity of the intact mature corn ear were in good agreement with the results in the literatures. This study demonstrates a practical technique to extract the permittivity of two‐layer medium with the ring electrodes, and will provide a new way to in situ monitoring the physiological changes of two‐layer medium and environmental parameters. [ABSTRACT FROM AUTHOR]

The arrangement and shape of coils for permittivity measurement of a dielectric sandwiched between carbon fiber reinforced plastics (CFRPs) using electromagnetic induction testing (EIT) is investigated here. First, the influence of the electromagnetic shielding effectiveness of the CFRPs on the permittivity measurement using EIT was examined by finite element analysis (FEA). The effectiveness was lower than that of general metals, indicating that EIT can be used for permittivity measurement. Next, the coil arrangement and shape suitable for permittivity measurement were investigated by FEA. The use of two rectangular spiral coils, one as a driver coil and the other as a pickup coil, was adopted. Finally, the permittivity was measured experimentally using the coil arrangement, geometry, and test conditions determined based on the FEA results. The experimental results showed that the output voltage increased as the permittivity increased, demonstrating the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Electron paramagnetic resonance (EPR) spectroscopy is used to address the remarkable persistence of the native Arrhenius dependence of the 2-aminopropanol substrate radical rearrangement reaction in B12-dependent ethanolamine ammonia-lyase (EAL) from Salmonella typhimurium from physiological to cryogenic (220 K) temperatures. Two-component TEMPOL spin probe mobility in the presence of 10 mM (0.08% v/v) 2-aminopropanol over 200–265 K demonstrates characteristic concentric aqueous-cosolvent mesodomain and protein-associated domain (PAD, hydration layer) solvent phases around EAL in the frozen solution. The mesodomain formed by the relatively small amount of 2-aminopropanol is highly confined, as shown by an elevated temperature for the order–disorder transition (ODT) in the PAD (230–235 K) and large activation energy for TEMPOL rotation. Addition of 2% v/v dimethylsulfoxide expands the mesodomain, partially relieves PAD confinement, and leads to an ODT at 205–210 K. The ODT is also manifested as a deviation of the temperature-dependence of the EPR amplitude of cob(II)alamin and the substrate radical, bound in the enzyme active site, from Curie law behavior. This is attributed to an increase in sample dielectric permittivity above the ODT at the microwave frequency of 9.5 GHz. The relatively high frequency dielectric response indicates an origin in coupled protein surface group–water fluctuations of the Johari–Goldstein β type that span spatial scales of ∼0.1–10 Å on temporal scales of 10−10–10−7 s. The orthogonal EPR spin probe rotational mobility and solvent dielectric measurements characterize features of EAL protein–solvent dynamical coupling and reveal that excess substrate acts as a fluidizing cryosolvent to enable native enzyme reactivity at cryogenic temperatures. [ABSTRACT FROM AUTHOR]

We present a novel electric permittivity sensor based on Bleustein–Gulyaev (BG) waves. Toward that end, we formulate the nonlinear electromechanical partial differential equations governing a BG wave resonator. We find that the permittivity of the material-under-test changes the sensor natural frequencies, thereby enabling the implementation of a frequency-shift permittivity sensor. We also find that the sensor sensitivity is enhanced by increasing bias voltage to drive the sensor into the nonlinear regime. Bias was found to be limited by electrical breakdown. The sensor was fabricated by depositing aluminum electrodes on a shear-poled lead zirconate titanate piezoelectric substrate. Experimental measurements of the displacement on the sensor surface were in good agreement with the developed model. [ABSTRACT FROM AUTHOR]

The combination of organics and metals in a composite film holds promise for combining plasmonic interaction with gain and for the realization of epsilon-near-zero (ENZ) metamaterials. In particular, fluorescent organic dyes can be used to compensate the plasmonic losses of a homogenized metal-organic material. Here, we fabricate such films through thermal co-evaporation of silver and an organic host:guest system and investigate experimentally the resulting linear optical properties for varying metal concentrations. We extract the effective permittivity of the resulting films with ellipsometry measurements and demonstrate the formation of silver nanoparticles, resulting in strongly localized surface plasmon resonances until a percolation threshold is reached. Through enhanced light-matter interaction, we observe a maximum of the photoluminescence for a concentration of 15% in volume of metal in the composite material. These results showcase a variety of growth parameters and will be useful for the future design of gain-compensated plasmonics and ENZ metamaterials. [ABSTRACT FROM AUTHOR]

Microwaves are used for diverse applications such as mobile phones, ovens, and therapy devices. However, there are few reports on the effects of microwaves on diseases other than cancer, and on physiological processes. Here, we focused on CaCO3 mineralization as a model of biomineralization and attempted to elucidate the effect of microwaves on CaCO3 mineralization using peptides. We conducted AFM, ζ potential, HPLC, ICP-AES, and relative permittivity measurements. Our findings show that microwaves alter the nanomorphology of the CaCO3 precipitate, from sphere-like particles to string-like structures. Furthermore, microwaves have little effect on the mineralization when the mineralization ability of a peptide is high, but a large effect when the precipitation ability is low. Our findings may be applicable to not only the treatment of teeth and bones but also the development of organic–inorganic nanobiomaterials. This methodology can be expanded to other molecular/atomic reactions under various microwave conditions to alter reaction activity parameters. [ABSTRACT FROM AUTHOR]

We report here a simple hydrothermal synthesis of 100–200 nm flakes of tochilinite (Fe1−xS)·n(Mg,Fe)(OH)2 constructed by interchanging atomic sulfide and hydroxide sheets as a representative of a new platform of multifunctional two-dimensional materials. The reliable formation of tochilinites was ensured by an excess of sodium sulfide, with the assembly of the metal sulfide and hydroxide sheets driven by their opposite electric charges. X-ray photoelectron spectroscopy found that the hydroxide layers involved Fe3+ cations from 10 to 40% of total iron tuned by addition of Al and Li entering the layers; the Fe1−xS sheets comprised comparable amounts of high-spin Fe3+ and Fe2+ centers, and minor S–S bonding. The room-temperature Mössbauer spectra fitted with several doublets (chemical shift of 0.35–0.4 mm s−1 and varying quadrupole splitting) transformed to three six-line patterns (hyperfine fields of ∼290, 350 and 480 kOe) due to magnetic ordering at 4.2 K, albeit the paramagnetic behavior observed in SQUID experiments. A series of UV-vis absorption maxima were explained in terms of both the high-index all-dielectric Mie resonance, in line with the permittivity measurement data, and the ligand-metal charge transfer resembling that in Fe–S clusters in proteins. Prospective properties and applications of the materials are discussed. [ABSTRACT FROM AUTHOR]

Biodiesel is widely used pure or mixed with diesel fossil fuel in diesel engines. Standards for determining biodiesel quality establish limits for the values of several physicochemical properties. However, the procedures to determine many properties are time‐consuming and demand specialized personnel and expensive equipment. Other methods to characterize biodiesel, such as electrical methods, are particularly interesting. Measurements of electrical properties (permittivity and conductivity) give valuable information about biodiesel, its feedstocks, and its blends with fossil fuel diesel, and solve the usual cost and time drawbacks. This work aims to present a thorough and systematic review of the literature on applications of electrical properties measurements of biodiesel, its feedstocks, and mixtures with other fuels. An overview of the experimental data, typical ranges of values, prediction models, and applications is presented and analyzed in detail, emphasizing blends of biodiesel with fossil fuel diesel. Correlations with important properties (kinematic viscosity, methanol content) are reviewed. Applications include transesterification monitoring, biodiesel aging, the detection of contaminants and electromagnetic heating. This research aimed to determine whether electrical properties are a valuable tool for the biodiesel industry, and what applications may be realized in light of current scientific development. It was determined that, in the current state of research, permittivity measurements could be used to accurately determine the amount of diesel and biodiesel in mixtures. © 2023 Society of Industrial Chemistry and John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

Accurate measurement of the permittivity and loss tangent of low-loss materials is essential due to their special applications in the field of ultra large scale integrated circuits and microwave devices. In this study, we developed a novel strategy that can accurately detect the permittivity and loss tangent of low-loss materials based on a cylindrical resonant cavity supporting the TE111 mode in X band (8–12 GHz). Based on an electromagnetic field simulation calculation of the cylindrical resonator, permittivity is precisely retrieved by exploring and analyzing the perturbation of the coupling hole and sample size on the cutoff wavenumber. A more precise approach to measuring the loss tangent of samples with various thicknesses has been proposed. The test results of the standard samples verify that this method can accurately measure the dielectric properties of samples that have smaller sizes than the high Q cylindrical cavity method. [ABSTRACT FROM AUTHOR]

We present a novel broadband permittivity characterization method for liquids measured in a semi-open vertically oriented test cell with an uncalibrated vector network analyzer. For this goal, we utilize three scattering matrices measured at different levels of liquid in the cell. With mathematical operations, we remove the effects of systematic measurement errors caused by both the vector network analyzer and a meniscus shaping the top of the liquid samples in such a type of test cell. To the best authors' knowledge, this is the first of such a calibration-independent method dealing with meniscus. We verify its validity by comparing our results with the data available in the literature and with the outcomes of our previously published calibration-dependent meniscus removal method (MR) for propan-2-ol (IPA), a 50% aqueous solution of IPA and distilled water. The new method yields results comparable with the MR method, at least for IPA and the IPA solution, revealing, however some problems when testing high-loss water samples. Nevertheless, it allows one to cut down on expenditures in the system calibration engaging skilled labor and expensive standards. [ABSTRACT FROM AUTHOR]

Controlling the dielectric properties is desirable for monitoring the efficiency of materials, which are newly applicable in electronic devices. In this work, the simple and well-known Rother-Lichtenecker equation has been modified to predict the real part of the dielectric permittivity of polymer nanocomposites. In the proposed model, the real part of dielectric permittivity is a function of interphase properties (thickness, volume fraction, and dielectric permittivity) and nanoparticle characteristics (shape, size, and volume fraction). The model results agree well with the experimental data for polymer nanocomposites containing different spherical, cylindrical, and plate-like nanoparticles. In addition, the predicted interphase properties cope very well with the experimental observations of interfacial interactions from valid literature. The high interphase properties and the small size of the nanoparticles are desired requirements of a nanocomposite with high dielectric permittivity. However, the dielectric permittivity of the nanoparticles barely affects that of the nanocomposite. The proposed model can accurately estimate the interphase properties of any available polymer nanocomposite considering the dielectric permittivity measurements. [ABSTRACT FROM AUTHOR]

To ensure the desired mechanical properties of adhesively bonded components, maintaining the prescribed mixing quality, i.e. mixing ratio and evenness, of two-component (2K) adhesives is essential. Although different studies proved that mixing errors may exert a negative impact on the bonding result, there are currently no methods available that would allow for continuous monitoring thereof during inline dosing processes. A way out of associated issues is offered by the Electrical Capacitance Tomography (ECT), which enables practitioners to map spatial material distributions and mixing ratios by measuring the capacitances of different media, including adhesives. Therefore, the aim of the study was to investigate the ECT's potential to be used for 2K mixture quality control. Due to the complexity of the matter, the presentation is split into two papers. In this 1st part, all preliminary experimental and analytical work aiming to determine polymer characteristics, above all permittivity, ε, needed to evaluate whether a respective 2K adhesive may be ECT-monitored is presented. For that, a permittivity measurement device (PMD) was developed, which allows for a fast and efficient determination of adhesive permittivities. Subsequently, the PMD was validated with reference dielectrics and then used to determine the permittivities of the components of 16 commercially available 2K adhesives (epoxies and polyurethanes). Finally, the relationship between permittivity and mixing ratio was investigated for a sub-set of four representative ECT-suitable adhesives. It was found that a wide variety of 2K polymers may principally be controlled by ECT and that the relationship between mixing ratio and mixture permittivity can be described by general analytical theories from the literature. As a result, preliminary experimental effort aiming to assess the adhesive suitability for inline ECT-monitoring could be significantly reduced. The latter experiments will be the topic of the 2nd part of the study. [ABSTRACT FROM AUTHOR]

Based on the system of electrohydrodynamic equations, we investigate the role of trigger-type electromagnetic factors in the generation of tornadoes and jet downbursts: perturbations of the atmospheric electric field under thunderclouds and the effect of giant dielectric permittivity of the cloud as a suspension of water microdroplets with a thin surface double electric layer. The work considers the combined influence of the tripole cloud-charge structure and the effect of the giant dielectric permittivity on the formation of tornado funnels and the occurrence of a number of related specific phenomena: a "collar" at the base of the funnel, "devil's horns" and the growth of a cascade in the form of a column of droplets and foam towards the descending tornado funnel. Other factors (unidirectional or multidirectional swirl of the center and periphery of a thundercloud, difference in the magnetic properties of atmospheric oxygen and nitrogen, etc.) usually play an auxiliary role in the formation of tornado-like vortices. [ABSTRACT FROM AUTHOR]

Simultaneous influence of marination and storage on dielectric properties of chicken meat was investigated through dielectric measurements at microwave frequencies. For this purpose, an open-ended coaxial probe and a vector network analyzer were used for measurement of the dielectric properties between 200 MHz and 20 GHz and at a room temperature of 22 °C. For all chicken samples, the same general trend was observed for the variations of dielectric properties with frequency. The dielectric constant decreased with frequency with significant slope change at about 5 GHz. The dielectric loss factor decreased sharply up to 2 GHz and then increased with frequency showing a broad relaxation above 8 GHz. Values of the dielectric constant and dielectric loss factor measured for marinated chicken meat samples were greater than those of non-marinated samples and this was more significant for the dielectric loss factor at lower frequencies. In addition, each level of marination was distinctly observed over the same frequency range. Investigation of the influence of storage revealed that the dielectric loss factor of marinated samples decreased over the storage period while those of non-marinated sample slightly increased with storage time. For both marinated and non-marinated samples, water loss increased with storage time. [ABSTRACT FROM AUTHOR]

For a large variety of food products, the moisture content can be indirectly determined by measuring their dielectric properties. In the case of coffee, the permittivity knowledge can be applied to determine the moisture content indirectly or for online moisture meters in automatic control of coffee dryers. However, there is little data on the dielectric properties of roasted ground coffee near the 2.45 GHz ISM band. In this contribution, the permittivity was measured versus temperature, bulk density, and moisture content. A resonant technique based on a coaxial microwave cavity was employed to obtain the complex permittivity as a function of those magnitudes near the 2.45 GHz ISM band. In addition, the permittivity of the coffee particle kernel has been estimated from a complex refractive index mixture equation, thus calculating the permittivity of the coffee particle kernel from the permittivity values of the mixture air-coffee (ground coffee) at different bulk densities. The results showed that both dielectric constant and loss factor increase for increasing temperature, bulk density, and moisture content values. Furthermore, expressions fitting the experimental data were provided, thereby facilitating the estimation of the values throughout the studied temperature, bulk density, and moisture content ranges. [ABSTRACT FROM AUTHOR]

The permittivity of a material is an important parameter to characterize the degree of polarization of a material and identify components and impurities. This paper presents a non-invasive measurement technique to characterize materials in terms of their permittivity based on a modified metamaterial unit-cell sensor. The sensor consists of a complementary split-ring resonator (C-SRR), but its fringe electric field is contained with a conductive shield to intensify the normal component of the electric field. It is shown that by tightly electromagnetically coupling opposite sides of the unit-cell sensor to the input/output microstrip feedlines, two distinct resonant modes are excited. Perturbation of the fundamental mode is exploited here for determining the permittivity of materials. The sensitivity of the modified metamaterial unit-cell sensor is enhanced four-fold by using it to construct a tri-composite split-ring resonator (TC-SRR). The measured results confirm that the proposed technique provides an accurate and inexpensive solution to determine the permittivity of materials. [ABSTRACT FROM AUTHOR]

Electrical property tomography (EPT) is a noninvasive method that uses magnetic resonance imaging (MRI) to estimate the conductivity and permittivity of tissues, and hence, can be used as a biomarker. One branch of EPT is based on the correlation of water and relaxation time T1 with the conductivity and permittivity of tissues. This correlation was applied to a curve-fitting function to estimate electrical properties, it was found to have a high correlation between permittivity and T1 however the computation of conductivity based on T1 requires to estimate the water content. In this study, we developed multiple phantoms with several ingredients that modify the conductivity and permittivity and explored the use of machine learning algorithms to have a direct estimation of conductivity and permittivity based on MR images and the relaxation time T1. To train the algorithms, each phantom was measured using a dielectric measurement device to acquire the true conductivity and permittivity. MR images were taken for each phantom, and the T1 values were measured. Then, the acquired data were tested using curve fitting, regression learning, and neural fit models to estimate the conductivity and permittivity values based on the T1 values. In particular, the regression learning algorithm based on Gaussian process regression showed high accuracy with a coefficient of determination R2 of 0.96 and 0.99 for permittivity and conductivity, respectively. The estimation of permittivity using regression learning demonstrated a lower mean error of 0.66% compared to the curve fitting method, which resulted in a mean error of 3.6%. The estimation of conductivity also showed that the regression learning approach had a lower mean error of 0.49%, whereas the curve fitting method resulted in a mean error of 6%. The findings suggest that utilizing regression learning models, specifically Gaussian process regression, can result in more accurate estimations for both permittivity and conductivity compared to other methods. [ABSTRACT FROM AUTHOR]

Relaxor ferroelectrics play an important role for technological applications, mainly for using in the fabrication of actuators, transducers and sensors. Therefore, there has been an increasing interest of the scientific community in the investigation of the physical properties of such system in order to better elucidate the observed intriguing and unsolved phenomena. In this work, relaxor Pb(Mg1/3Nb2/3)O3 (PMN) ceramic system was prepared and the dielectric properties have been studied in details as a function of frequency, temperature and magnitude of the DC-bias electric field. Results reveal that the temperature dependence of the dielectric permittivity can be successfully described in the whole analyzed temperature range (100–400 K) by using a macroscopic statistical model, which describe the dielectric response in relaxor systems with diffuse phase transition (DPT). By using this phenomenological model, the temperature and DC-bias electric field dependences of the dielectric permittivity have been also revisited, from the analysis of the DPT behavior, promoting a careful discussion on the nature of the phase transition in relaxors materials. The calculated sizes of the polar nanoregions (PNRs) suggest the development of a structural disorder in the studied system, which promote the high diffuse ferroelectric transition as the amplitude of the DC-bias electric field increases. [ABSTRACT FROM AUTHOR]

This paper presents a material relative permittivity extraction technique based on three measurements of two identical coaxial lines, terminated by a short-circuit configuration. The test cells have the same geometric dimensions but various lengths. The most extended fixture is partially filled with the sample under test to be measured in the scanned frequency [6–20] GHz. The measurement methodology is based on the use of the fixture form factor. The accuracy of the relative permittivity parameter is better than 5% throughout the frequency range. All tested samples have been compared with the two transmission-line technique results. [ABSTRACT FROM AUTHOR]

The dielectric property relations of a series of BaTiO3–polymer composites with a uniquely high-volume fraction of ceramic [(1 − x)BaTiO3–x polytetrafluoroethylene (PTFE), with volume fractions x = 0.025, 0.05, 0.1, and 0.2] are studied. Such high-volume fraction of the BaTiO3 phase is achieved by using the cold sintering process, as it enables a single-step densification of oxides at an extremely low temperature; typically, the volume fractions from other processing methods are limited to ceramic filler volume fractions of ∼0.6. Microstructural and resistivity analyses suggest that the optimal range of the polymer content to effectively enhance the functions is x = 0.05, as higher volume fractions of the polymer hinder the densification of the ceramic. The composite exhibits improved properties such as lower loss tangent, higher resistivity, and high permittivity that vary systematically with x following an empirical mixing law. Here, we consider the composite mixing law trends and the changes to properties, which indicate that size effects are also being induced in the dielectric response, including shift of Tc, broadening of transition, and reduction of permittivity with respect to volume fraction of the PTFE. Our findings provide a new and simple strategy for the fabrication of ceramic–polymer composites with extremely high relative permittivities and resistivities, and these observations all point to a route that can allow us to engineer new types of advanced dielectric materials. [ABSTRACT FROM AUTHOR]

We report studies on the unusual frequency dispersion of the dielectric permittivity maxima of methylammonium lead iodide pellets at temperatures around the tetragonal–cubic phase transition. The origin of this observed permittivity response was studied in terms of grains and grain boundaries' contributions in impedance, electric modulus, dielectric permittivity, and electrical conductivity. From theoretical fits of impedance and electric modulus measurements at different temperatures over a frequency range of 103–10 Hz, the reconstructed contributions of the grain boundary and grain permittivities show peaks around 339 K and 384 K, respectively. The origin of the grain boundary permittivity peak is discussed in terms of heterogenic ionic conduction associated with I− and MA+ ions in MAPbI3, while the peak in grain permittivity at high temperature is in terms of ionization of intrinsic carriers. The high value of the grain dielectric permittivity (ε g = 1193) , compared to the reconstructed grain boundary permittivity (ε g b = 53) , suggests a possible relaxor ferroelectric behavior with a diffuse phase transition for methylammonium lead iodide. The difficulties in confirming the ferroelectric nature of this halide perovskite based on impedance and electrical module data are also discussed. [ABSTRACT FROM AUTHOR]

Atmospheric water adsorbed by porous materials may significantly change its electrodynamic response in a wide frequency range. Mechanical and chemical stabilities of silicon dioxide along with a proven manufacturing method of porous SiO2 samples made it convenient for studying the effects of moisture adsorption on various parameters of the porous media. We report the dielectric properties of SiO2-based nanoporous glass in the frequency range of 20 Hz–400 THz at ambient atmospheric conditions and at a low residual pressure of ≤1 mbar. We observed a significant low-frequency dispersion of the complex dielectric permittivity and enhancement of dielectric loss for the porous sample exposed to the ambient moisture. In the terahertz range, the change in dielectric response is smaller and correlates with the moisture saturation of the sample. [ABSTRACT FROM AUTHOR]

This paper describes a new approach, based on the Mie theory, to measure the dielectric properties of lossless materials at temperatures greater than 1500 °C. For the reliable operation of microwave transmitting materials in harsh environments, it is crucial to correctly characterize the permittivity under various temperature conditions. Heating and measurement systems using a propane torch and a single horn antenna were designed to estimate such dielectric properties. The reflection spectrum of Al2O3 ceramics at room temperature was determined using the Mie theory to derive the permittivity and validate the approach. High-temperature dielectric constants are derived from simulated values, which are reliable and have only a slight slope as a function of temperature. These results indicate that the permittivity measurement technique can provide powerful information for the optimal design and accurate evaluation of the dielectric properties of various lossless materials at high temperatures. [ABSTRACT FROM AUTHOR]