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In this work, the molecular mobility at the glass transition of poly(vinyl acetate) (PVAc) and poly(ethylene-co-vinyl acetate) (EVA) amorphous sample series was investigated. The temperature and pressure dependences of the intermolecular interactions were studied from time–temperature–pressure superpositions and from the relaxation time dispersion of the segmental relaxation. The difference in terms of intermolecular interactions due to the lateral group ratio of vinyl acetate (VAc) was then estimated from the activation volume and related to the cooperative behavior. The isobaric fragility and its two contributions (thermal and volumetric) were estimated through high pressure broadband dielectric spectroscopy measurements. The volumetric and thermal contributions show different behaviors as a function of the VAc ratio and as a function of the pressure. Thus, the study of the PVAc/EVA series has allowed us to emphasize that the intramolecular and intermolecular interactions induced by the dipolar pendant groups directly influence the thermal and volumetric contributions to the isobaric fragility. [ABSTRACT FROM AUTHOR]

We develop a surface for the electric dipole moment of three interacting helium atoms and use it with state-of-the-art potential and polarizability surfaces to compute the third dielectric virial coefficient, Cɛ, for both 4He and 3He isotopes. Our results agree with previously published data computed using an approximated form for the three-body polarizability and are extended to the low-temperature regime by including exchange effects. In addition, the uncertainty of Cɛ is rigorously determined for the first time by propagating the uncertainties of the potential and polarizability surfaces; this uncertainty is much larger than the contribution from the dipole-moment surface to Cɛ. Our results compare reasonably well with the limited experimental data. The first-principles values of Cϵ computed in this work will enhance the accuracy of primary temperature and pressure metrology based on measurements of the dielectric constant of helium. [ABSTRACT FROM AUTHOR]

We have conducted a detailed high-pressure (HP) investigation on Eu-doped BaTiO3 using angle-resolved x-ray diffraction, Raman spectroscopy, and dielectric permittivity measurements. The x-ray diffraction data analysis shows a pressure-induced structural phase transition from the ambient tetragonal to the mixed cubic and tetragonal phases above 1.4 GPa. The tetragonality of the sample due to the internal deformation of the TiO6 octahedra caused by the charge difference from Eu doping cannot be lifted by pressure. Softening, weakening, and disappearance of low-frequency Raman modes indicate ferroelectric tetragonal to the paraelectric cubic phase transition. However, the pressure-induced increase in the intensity of [E(LO), A1(LO)] and the octahedral breathing modes indicate that the local structural inhomogeneity remains in the crystal and is responsible for spontaneous polarization in the sample. The low-frequency electronic scattering response suggests pressure-induced carrier delocalization, leading to a semi-metallic state in the system. Our HP dielectric constant data can be explained by the presence of pressure-induced localized clusters of microscopic ferroelectric ordering. Our results suggest that the HP phase coexistence leads to a ferroelectric-like semi-metallic state in Eu-doped BaTiO3 under extreme quantum limits. [ABSTRACT FROM AUTHOR]

We have conducted a detailed high-pressure (HP) investigation on Eu-doped BaTiO3 using angle-resolved x-ray diffraction, Raman spectroscopy, and dielectric permittivity measurements. The x-ray diffraction data analysis shows a pressure-induced structural phase transition from the ambient tetragonal to the mixed cubic and tetragonal phases above 1.4 GPa. The tetragonality of the sample due to the internal deformation of the TiO6 octahedra caused by the charge difference from Eu doping cannot be lifted by pressure. Softening, weakening, and disappearance of low-frequency Raman modes indicate ferroelectric tetragonal to the paraelectric cubic phase transition. However, the pressure-induced increase in the intensity of [E(LO), A1(LO)] and the octahedral breathing modes indicate that the local structural inhomogeneity remains in the crystal and is responsible for spontaneous polarization in the sample. The low-frequency electronic scattering response suggests pressure-induced carrier delocalization, leading to a semi-metallic state in the system. Our HP dielectric constant data can be explained by the presence of pressure-induced localized clusters of microscopic ferroelectric ordering. Our results suggest that the HP phase coexistence leads to a ferroelectric-like semi-metallic state in Eu-doped BaTiO3 under extreme quantum limits. [ABSTRACT FROM AUTHOR]

There is no consensus among researchers regarding how phase transitions occur in antiferroelectric (AFE) epitaxial heterostructures, in particular, in heterostructures based on model AFE lead zirconate. The questions about the number of phase transitions in such films and by what mechanism they occur remain controversial. This paper presents a look at the phase transition scenario in two types of epitaxial heterostructures: PbZrO 3 /Ba[La–Sn]O 3 /MgO (001) thin films with thicknesses from 25 to 1000 nm and PbZrO 3 /SrRuO 3 /SrTiO 3 (001) thin film 100 nm thick using the diffuse x-ray scattering in the grazing incidence setup. We register the characteristic butterfly-shaped diffuse scattering (DS) intensity distribution in the H K pseudocubic planes, which corresponds to the anisotropic ferroelectric soft mode. No incommensurate soft mode was observed in the cuts of reciprocal space parallel to the film surface by diffuse scattering. We reproduce the shape of DS distribution at different temperatures by the model based on the dielectric stiffness and the electric polarization correlation tensor in the cubic approximation. Such modeling allows not only to characterize the DS parameters from the challengingly low signal-to-background data set, but also to extract experimentally the sensitivity of the materials with respect to inhomogeneous polarization. While the observed temperature evolution of DS is consistent with the dielectric measurements, the correlation between the DS and the phase transition sequence observed by superstructure reflections is yet to be understood better. [ABSTRACT FROM AUTHOR]

Lead-free piezoelectric ceramics of (1 − x)K0.5Na0.5NbO3-xCaTiO3 were fabricated, and their crystal structure, microstructure, and electrical properties were systematically studied. Rietveld refinement of the x-ray diffraction data and Raman spectroscopic analyses revealed a composition-dependent structural phase transition: three phase transitions, namely, from a pure orthorhombic phase for x ≤ 0.02 to a mixed phase of orthorhombic and tetragonal phases (0.03 ≤ x ≤ 0.08) and finally another mixed phase of tetragonal + cubic for x = 0.10 and 0.15 at room temperature (RT). The morphological study reveals a decrease in grain size along with a more uniform distribution of grains as the concentration of CaTiO3 (CT) increases; notably, a homogeneous distribution of grains is observed for x = 0.05. The temperature-dependent dielectric properties show two phase transitions, from orthorhombic to tetragonal (TO-T) and tetragonal to cubic (TC), for unmodified K0.5Na0.5NbO3 (KNN). However, both the phase transition temperatures (TO-T and TC) decrease, and the transition peaks broaden with an increase in CT substitution, and for x > 0.06, the TO-T shifted below RT. The broadening of the transition peak at TO-T may be due to the relaxation behavior. Among the prepared samples, the 5 mol. % CT-modified KNN shows the optimum electrical properties (d33 = 114 pC/N, ɛr = 412, and 2Pr = 15.25 μC/cm2) at RT. The enhanced electrical properties for x = 0.05 are due to the coexistence of orthorhombic and tetragonal phases, facilitating easy polarization rotation and flattening of the free energy profile. A phase diagram has been constructed based on the information gathered from the temperature-dependent dielectric measurements, RT x-ray diffraction, and Raman spectroscopy data and is discussed in detail. [ABSTRACT FROM AUTHOR]

We report the nonlinear dielectric properties of three triple-perovskite ruthenates: Ba 3 CoRu 2 O 9 , Ba 3 BiRu 2 O 9 , and Sr 3 CaRu 2 O 9. These compounds exhibit notable correlations among their spin, charge, lattice, and polar degrees of freedom. Ba 3 CoRu 2 O 9 displays a pronounced frequency-dependent relaxation in χ 2 , 3 just above the magnetoelastic transition, occurring around 100 K, followed by an abrupt loss of polarization within the ordered phase. In Ba 3 BiRu 2 O 9 , we encounter the possibility of multiple coexisting relaxation behaviors, indicating a complex phase strongly influenced by the spin-gap opening at 175 K. Lastly, Sr 3 CaRu 2 O 9 displays anomalies with strong dispersion effects close to its magnetic transitions, indicating a robust coupling between magnetic and dipolar orders in the system. These measurements highlight the significance of higher-order (hyper-)susceptibilities in providing profound insight into the dynamics of a system, offering information otherwise inaccessible through the linear polarization response alone. [ABSTRACT FROM AUTHOR]

The impact of successive replacement of K+ by Na+ on the megahertz–gigahertz polarization response of 0.25[fKSCN + (1 − f)NaSCN] + 0.75CH3CONH2 deep eutectic solvents (DESs) was explored via temperature-dependent (303 ≤ T/K ≤ 343) dielectric relaxation (DR) measurements and computer simulations. Both the DR measurements (0.2 ≤ ν/GHz ≤ 50) and the simulations revealed multi-Debye relaxations accompanied by a decrease in the solution static dielectric constant (ɛs) upon the replacement of K+ by Na+. Accurate measurements of the DR response of DESs below 100 MHz were limited by the well-known one-over-frequency divergence for conducting solutions. This problem was tackled in simulations by removing the zero frequency contributions arising from the ion current to the total simulated DR response. The temperature-dependent measurements revealed a much stronger viscosity decoupling of DR times for Na+-containing DES than for the corresponding K+ system. The differential scanning calorimetry measurements indicated a higher glass transition temperature for Na+-DES (∼220 K) than K+-DES (∼200 K), implying more fragility and cooperativity for the former (Na+-DES) than the latter. The computer simulations revealed a gradual decrease in the average number of H bonds (⟨nHB⟩) per acetamide molecule and increased frustrations in the average orientational order upon the replacement of K+ by Na+. Both the measured and simulated ɛs values were found to decrease linearly with ⟨nHB⟩. Decompositions of the simulated DR spectra revealed that the cation-dependent cross interaction (dipole-ion) term contributes negligibly to ɛs and appears in the terahertz regime. Finally, the simulated collective single-particle reorientational relaxations and the structural H-bond fluctuation dynamics revealed the microscopic origin of the cation identity dependence shown by the measured DR relaxation times. [ABSTRACT FROM AUTHOR]

The electric field dependence of the electrocaloric effect is investigated in BaTiO 3 and Ba(Zr 0.12 Ti 0.88 )O 3 by a direct method with sub-mK temperature resolution. The field dependence of the caloric temperature change Δ T (E) shows a pronounced change within a few Kelvin around the Curie temperature for the first-order phase transition in BaTiO 3. The transition from a linear field dependence in the ferroelectric phase over a butterfly-shaped to a quadratic field dependence in the paraelectric phase is compared to predictions of Landau–Devonshire theory. The simultaneous measurement of caloric and dielectric properties further allows for the investigation of the polarization dependence Δ T (P) of the electrocaloric effect. We find clear deviations from the predicted quadratic polarization dependence for temperatures close to the Curie temperature. Ba(Zr 0.12 Ti 0.88 )O 3 shows in contrast only a slow and gradual change of the field dependence over a broad temperature range as a consequence of its diffuse phase transition. [ABSTRACT FROM AUTHOR]

The slow Arrhenius process (SAP) is a dielectric mode connected to thermally activated equilibration mechanisms, allowing for a fast reduction in free energy in liquids and glasses. The SAP, however, is still poorly understood, and so far, this process has mainly been investigated at temperatures above the glass transition. By employing a combination of methods to analyze dielectric measurements under both isochronal and isothermal conditions, we were able to quantitatively reproduce the dielectric response of the SAP of different polymers and to expand the experimental regime over which this process can be observed down to lower temperatures, up to 70 K below the glass transition. Employing thin films of thicknesses varying between 10 and 800 nm, we further verified that the peak shape and activation energy of the SAP of poly(4-bromostyrene) are not sensitive to temperature, nor do they vary upon confinement at the nanoscale level. These observations confirm the preliminary trends reported for other polymers. We find that one single set of parameters—meaning the activation barrier and the pre-exponential factor, respectively, linked to the enthalpic and entropic components of the process—can describe the dynamics of the SAP in both the supercooled liquid and glassy states, in bulk and thin films. These results are discussed in terms of possible molecular origins of the slow Arrhenius process in polymers. [ABSTRACT FROM AUTHOR]

Glassy films of methyl-m-toluate have been vapor deposited onto a substrate equipped with interdigitated electrodes, facilitating in situ dielectric relaxation measurements during and after deposition. Samples of 200 nm thickness have been deposited at rates of 0.1 nm/s at a variety of deposition temperatures between 40 K and Tg = 170 K. With increasing depth below the surface, the dielectric loss changes gradually from a value reflecting a mobile surface layer to that of the kinetically stable glass. The thickness of this more mobile layer varies from below 1 to beyond 10 nm as the deposition temperature is increased, and its average fictive temperature is near Tg for all deposition temperatures. Judged by the dielectric loss, the liquid-like portion of the surface layer exceeds a thickness of 1 nm only for deposition temperatures above 0.8Tg, where near-equilibrium glassy states are obtained. After deposition, the dielectric loss of the material positioned about 5–30 nm below the surface decreases for thousands of seconds of annealing time, whereas the bulk of the film remains unchanged. [ABSTRACT FROM AUTHOR]

The novel Zn 0.4 Mn 0.4 Ni 0.2 Ce 0.2 Fe 1.8 O 4 (ZMNCF) nanoparticles were first produced using the sol-gel auto-combustion method and then dispersed onto the surface of multi-walled carbon nanotubes (MWCNTs) with the aid of ultra-sonication and a series of different concentration of (ZMNCF) 1-x /(MWCNTs) x ; x = 0–20 wt % nanocomposites were created. X-ray diffraction (XRD) analysis confirmed the Fd-3m space group and spinel structure of synthesized nanoparticles and revealed that the increasing concentration of MWCNTs has a great influence on the structural properties of the spinel ferrites. Transmission electron microscopy (TEM) was used to study the distribution, size and symmetry of nanoparticles and the accumulation of ZMNCF nanoparticles on the outer surfaces of MWCNTs. The estimation of different vibrational bands was examined using Fourier transform infrared (FTIR) spectroscopy. The dielectric and impedance measurements were studied in the frequency spectrum of 25 Hz to 2 MHz at room temperature. A detailed study of polarization mechanisms, Maxwell-Wagner model, and Koop's theory and the effect of increasing concentration of MWCNTs on grain and grain boundaries have been discussed. The AC conductivity measurements conducted on the synthesized nanoparticles demonstrated an enhancement in conductivity upon the addition of MWCNTs. The percolation threshold for the nanocomposite was found to be between 10 and 15 wt %, corresponding to a significant increase in conductivity due to the formation of a continuous conductive network. The valuable responses in dielectric properties showed that the synthesized nanocomposites could be used in future energy storage devices. [ABSTRACT FROM AUTHOR]

The crystalline NiO is prepared within the configuration Ni 1-x Ce x Al x O (x = 0.00, 0.05, and 0.1) using a hydrothermal process. XRD and SEM analyses were conducted to examine the crystal structure and morphology of samples which reveals highly crystalline nature and uniform morphology, respectively. UV-spectra confirms the optical band gap lies in the range of 1.63–3.41 eV. The pristine NiO has a band gap of 3.42 eV which lies in the insulating properties range, while the insertion of co-dopant concentration causes to reduction of the band gap up to 1.63 eV which lies in the semiconducting properties range that ensures the higher electronic conduction. The PL spectra show that the luminescence intensity is highly reduced with the insertion of co-dopant ions in the NiO lattice which is the confirmation of higher sensitivity. Raman spectra reveal the formation and purity of the samples due to the non-existence of secondary Raman modes related to the Ce and Al dopants and are well-matched with XRD results. The magnetic measurements reveal the enhancement in remanace magnetization and saturation magnetization with the reduction in coercivity and square ratio showing that the doping of Ce and Al into NiO is influencing its antiferromagnetic nature. NiO may be showing altered magnetic characteristics with the possible contribution from ferrimagnetic or ferromagnetic phases, as the dopant affects the magnetic interactions. Dielectric measurements reveal the increase in capacitance, conductance, energy dissipation, energy storage, and decrease in resistance with the increase in co-dopant concentrations. Based on the obtained results, NiO with 10 % (Ce, Al) co-doping is a suitable candidate for efficient use in magneto-optical and spintronics device applications. [ABSTRACT FROM AUTHOR]

The dielectric properties of active biological tissues within the 10Hz-100 MHz frequency range contain rich information about tissue morphology and function. Accurately understanding the dielectric properties of active human tissues holds significant value for disease diagnosis and electromagnetic protection. However, accurately measuring these properties has been challenging due to factors such as electrode polarization and distribution parameters. This study has developed a dual-purpose measuring cell that supports both four-electrode and two-electrode impedance measurements. Leveraging this development, we have established a system and methodology that is well-suited for the dielectric property measurement of active biological tissues within the frequency range of 10Hz to 100 MHz. Our measurements of dielectric properties in NaCl solutions of varying concentrations and pig liver tissues demonstrate the system's high accuracy and repeatability. For NaCl solutions, the maximum relative deviation is only 6.34%, with an average deviation of less than 1.5%. For pig liver tissues, the overall relative deviation is below 6%. Through the integration of the four-electrode and two-electrode measurement systems, we have successfully addressed the challenges of electrode polarization at low frequencies and the influence of distribution parameters at high frequencies, achieving a significant improvement in measurement accuracy across the spectrum. [ABSTRACT FROM AUTHOR]

This study aims to enhance the thermal stability and dielectric properties of an epoxy/phenolic resin-type novolac blend by incorporating carbon nanofibers (CNFs). The EP/novolac-CNF composite was created by dispersing a 10% weight fraction of CNFs into the EP/novolac blend. Various analyses were conducted to assess the improvements brought by the addition of CNFs. Differential Thermal Analysis (DTA) and Dielectric Measurements (DM) were employed to determine the Tg values. Thermogravimetric Analysis (TG) and Differential Thermogravimetric Analysis (DTG) were used to evaluate the thermal stability. Results indicated that the inclusion of carbon nanofibers enhanced the thermal stability of the composite, as evidenced by the increased char yield at temperatures exceeding 700℃, reaching 27.08% compared to 8.4% for the EP/novolac blend. Dielectric measurements were conducted across a frequency range of 10² - 107 Hz and a temperature range of 293-463 K. The results revealed a wide dielectric dispersion in all samples, indicating the presence of Debye relaxation and a broad distribution of relaxation times. Eyring's relaxation rate equation was applied to determine the thermodynamic parameters, such as the Gibbs free energy of activation (ΔG) and entropy (ΔS). The results indicated strong intermolecular interactions in all tested samples. The incorporation of carbon nanofibers into the EP/novolac blend led to improvements in thermal stability and dielectric properties. The analysis of various parameters suggests enhanced performance and potential applications of the EP/novolac-CNF composite in relevant fields. [ABSTRACT FROM AUTHOR]

The dielectric constant, or permittivity, is a fundamental property that characterizes a material's electromagnetic behavior, crucial for diverse applications in agriculture, healthcare, industry, and scientific research. In microwave engineering, accurate permittivity measurement is essential for advancements in fields such as biomedicine, aerospace, and microwave chemistry. However, conventional waveguide resonator methods face challenges when measuring high-loss materials, often leading to reduced accuracy and increased cost. This paper introduces a lightweight, compact system for dielectric constant measurement using a negative-resistance voltage-controlled oscillator (VCO) integrated within a frequency synthesizer. The proposed system employs phase response variations of a planar sensor embedded in the VCO's gate network to detect changes in oscillation frequency, enabling precise measurement of high-loss materials. The experimental validation demonstrates the system's capability to accurately measure dielectric constants of lossy organic liquids, with applications in distinguishing liquid mixtures. The contributions include the design of a resonant-network-attached oscillator, comprehensive sensor performance simulations, and successful characterization of organic liquid mixtures, showcasing the potential of this approach for practical dielectric property measurements. [ABSTRACT FROM AUTHOR]

The leaching process for copper extraction has garnered significant attention due to its critical role in meeting the rising demand for copper, driven by global trends towards decarbonization and electrification. The accurate measurement of variables is essential for process control, prompting the development of advanced sensor technologies. This paper reviews the applications of dielectric permittivity measurements in the mining industry, focusing on their potential to enhance the monitoring and optimization of copper leaching processes. It evaluates the suitability of permittivity-based sensors, analyzing their advantages and limitations, and discusses the implications for process control and economic optimization. The study highlights the integration of permittivity measurements into existing monitoring systems, aiming to improve efficiency, reduce environmental impact, and increase ore recovery rates. This comprehensive review provides insights into the current state of permittivity measurement technologies and their future prospects in the context of copper leaching. [ABSTRACT FROM AUTHOR]

The article in Nature Communications discusses the properties of guanidinium nitrate (GN) and challenges the claims made by Karothu et al. regarding the ferroelectricity and semiconductivity of GN crystals. The authors present evidence from previous studies on the giant deformation, crystal structures, and dielectric properties of GN to refute the new properties claimed by Karothu et al. They conclude that GN does not exhibit ferroelectric properties and is unsuitable for certain applications proposed by Karothu et al. The study was supported by the Adam Mickiewicz University in Poznań and the authors declare no competing interests. [Extracted from the article]

In this study, <001> c -oriented 0.93(Bi 0.5 Na 0.5)TiO 3 -0.06BaTiO 3 -0.01(K 0.5 Na 0.5)NbO 3 (BNT-6BT-1KNN) single crystals were successfully synthesized using the flux method, achieving crystal dimensions up to 5 × 5 × 3 mm3. At room temperature, these single crystals exhibit an impressive piezoelectric coefficient (d 33) of 264 pC/N, surpassing the performance of equivalent composition in randomly oriented and textured ceramics. Unlike typical (Bi 0.5 Na 0.5)TiO 3 -based non-ergodic relaxors, the initial strain loop reveals a unique negative minimum strain under a negative electric field, indicating distinct strain characteristics. The application of a poling electric field results in notable changes to both dielectric behaviors and domain structures, signifying a phase transition from polar nanoregions (PNRs) to long-range ferroelectric domains. Temperature-dependent dielectric measurements of the poled specimen reveal an anomaly near the freezing temperature (T f), indicating a transition between two polar states. Within the temperature range from T f to 200 °C, dielectric and piezoelectric responses suggest a coexistence of non-ergodic and ergodic relaxor states. Furthermore, a substantial electrostrain of 0.47 % was observed at 175 °C, corresponding to an inverse piezoelectric coefficient (d 33 ∗) of 940 pm/V, confirming the high electromechanical responsiveness. These findings underscore the potential of BNT-6BT-1KNN single crystals as high-performance lead-free piezoelectric materials for advanced actuator applications. [Display omitted] [ABSTRACT FROM AUTHOR]

A novel method to measure the dielectric constant (ε r) of a ceramic material at GHz range has been introduced in this work. The dielectric measurement technique using the Micro-Strip Line (MSL) coupled Dielectric Resonator Antenna (DRA) setup with simulation assisted results has been detailed. The resonance frequency corresponding to the HEM 11δ mode is extracted from the reflection coefficient (S 11 parameter) and utilized to measure ε r for DRA made from the material under investigation. Initially, ZrO 2 sample, with known ε r , is used to verify the proposed method. An ε r value of ∼17.5 has been experimentally obtained using the proposed method. Then, the measurement is done for a system with completely unknown ε r i.e., a composite of (1-x)BaTiO 3 -(x)NiO, x = 0, 0.05, 0.1, and 0.15. A detailed structural characterization study has been utilized for the BaTiO 3 -NiO samples to understand the material properties at the fundamental level. The experimental value of the ε r in the GHz range was obtained as 24.2, 32.3, and 29.5 for x = 0.05, 0.1, and 0.15, using the proposed technique. [ABSTRACT FROM AUTHOR]

Potential applications of microwave energy, a developed form of clean energy, are diverse and extensive. To expand the applications of microwave heating in the metallurgical field, it is essential to obtain the permittivity of ores throughout the heating process. This paper presents the design of a 2.45 GHz ridge waveguide apparatus based on the transmission/reflection method to measure permittivity, which constitutes a system capable of measuring the complex relative permittivity of the material under test with a wide temperature range from room temperature up to 1100 °C. The experimental results indicate that the system is capable of performing rapid measurements during the heating process. Furthermore, the system is capable of accurately measuring dielectric properties when the real part of the permittivity and the loss tangent vary widely. This measurement system is suitable for high-temperature dielectric property measurements and has potential applications in microwave-assisted metallurgy. [ABSTRACT FROM AUTHOR]

In this study, we delve into the complex dielectric behaviors of lanthanum (La)-doped PNN-PZT relaxor-ferroelectric ceramics under the influence of high AC fields. Our approach involves a meticulous design of dielectric measurements to scrutinize the decoupling phenomenon between local polarization oscillation and global polarization switching. Remarkably, the application of high AC fields (>0.5 kV/mm) causes a dramatic increase in the dielectric permittivity (2x), alongside pronounced frequency dispersion (>65 °C) and a permittivity hump below Tm in 7% La-doped relaxor compositions. For relaxor-ferroelectric ceramics doped with lower La (<=5%) that are featured with tweed-like submicron domains as imaged in in situ transmission electron microscopy, the significantly enhanced dielectric permittivity and dielectric loss (>1) are induced under high AC fields (<0.5 kV/mm). A comparative study with a polarization loop in the time domain under various AC fields and DC bias demonstrates that the dielectric anomaly in the frequency domain is associated with global polarization switching, co-existing with polarization oscillation mechanism in various domains. This frequency domain method reveals threshold AC fields (0.25–0.5 kV/mm) above which polarization switching occurs in relaxor-FE compositions at elevated temperatures, complements the dynamic behaviors of P–E hysteresis, and cautions the control of AC fields in dealing with relaxor-ferroelectric materials for advanced electronic applications. [ABSTRACT FROM AUTHOR]

In this study, high-performance InAlN/GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) are fabricated using HfAlOx-based charge-trapping layer dielectric stack combined with in situ O3 treatment. A positive threshold voltage shift (ΔVTH) of 8.9 V is achieved due to the charge-trapping effect. The device also shows a high Ion/Ioff ratio of ∼1010, a low gate leakage current of ∼10−7 mA/mm, and a relatively high BVDS of 400 V. The suppression of gate leakage current results in an ultra-high gate breakdown voltage of 22.5 V, owing to the superior current blocking capability of the O3-based Al2O3/HfO2 blocking layers and the interface improvement between dielectric and InAlN barrier achieved through in situ O3 treatment. The time-dependent dielectric breakdown measurements reveal the quality and reliability of the dielectric layer, predicting a maximum VGS of 9.66 and 9.31 V for a 10-year lifetime at failure rates of 63.2% and 0.10%, respectively. Additionally, x-ray photoelectron spectroscopy, atomic force microscopy, and multi-frequency C–V measurements further verify the effectiveness of the in situ O3 treatment in the optimization of the dielectric/GaN interface. These results demonstrate a practical approach to significantly improve the performance of InAlN/GaN MIS-HEMTs. [ABSTRACT FROM AUTHOR]

In this article, we investigate the in situ growth of Al2O3 on β -Ga2O3 using metal-organic chemical vapor deposition at a high temperature of 800 °C. The Al2O3 is grown within the same reactor as the β -Ga2O3, employing trimethylaluminum and O2 as precursors without breaking the vacuum. We characterize the shallow and deep-level traps through stressed capacitance–voltage (C–V) and photo-assisted C–V methods. The high-temperature deposited dielectric demonstrates an impressive catastrophic breakdown field of approximately 10 MV/cm. Furthermore, we evaluate the reliability and lifetime of the dielectrics using time-dependent dielectric breakdown measurements. By modifying the dielectric deposition process to include a high-temperature (800 °C) thin interfacial layer and a low-temperature (600 °C) bulk layer, we report a 10-year lifetime under a stress field of 3.5 MV/cm along a catastrophic breakdown field of 7.8 MV/cm. [ABSTRACT FROM AUTHOR]

In this article, we investigate the in situ growth of Al2O3 on β -Ga2O3 using metal-organic chemical vapor deposition at a high temperature of 800 °C. The Al2O3 is grown within the same reactor as the β -Ga2O3, employing trimethylaluminum and O2 as precursors without breaking the vacuum. We characterize the shallow and deep-level traps through stressed capacitance–voltage (C–V) and photo-assisted C–V methods. The high-temperature deposited dielectric demonstrates an impressive catastrophic breakdown field of approximately 10 MV/cm. Furthermore, we evaluate the reliability and lifetime of the dielectrics using time-dependent dielectric breakdown measurements. By modifying the dielectric deposition process to include a high-temperature (800 °C) thin interfacial layer and a low-temperature (600 °C) bulk layer, we report a 10-year lifetime under a stress field of 3.5 MV/cm along a catastrophic breakdown field of 7.8 MV/cm. [ABSTRACT FROM AUTHOR]

Varistors, due to their unique properties, are materials commonly used in surge protection devices. Their reliability, however, requires periodic inspection, which should specifically include assessment of their moisture content. So far, no method has been developed that would directly and non-invasively allow for the assessment of the moisture content of a varistor. In this work, an attempt was made to use dielectric spectroscopy for this purpose, i.e., measurements of dielectric parameters in the frequency domain. The tests were carried out on samples of materials based on silicon carbide. The result of the tests was the determination of the dependence of the dielectric response of the tested materials on moisture content, which after further tests may be the starting point for the development of a method for determining the moisture content of varistor surge arresters. [ABSTRACT FROM AUTHOR]

This study investigates the structural, electrical, leakage current, and magnetic characteristics of the double perovskite material Nd2NiTiO6 synthesized through the sol–gel citrate auto‐ignition method. The Rietveld refinement of the X‐ray diffraction patterns confirmed a monoclinic symmetry (space group P21/n) with an ordered arrangement of alternate NiO6 and TiO6 octahedra. Impedance spectroscopic analysis exhibited the material's non–Debye‐type relaxation mechanism and semi‐conductive nature. AC conduction analysis revealed that the conduction of charge carriers occurs via the nonoverlapping small polaron hopping mechanism, consistent with Mott's variable range hopping model. Temperature‐ and frequency‐dependent dielectric measurements were interpreted using the Maxwell–Wagner interfacial polarization model. The analysis of thermal‐ and field‐dependent leakage currents established that conduction is ohmic, which the Schottky barrier model explains. Studies on magnetization ruled out the presence of magnetic ordering connected to indirect interaction between Ni2+ ions via Ti4+ ions and the rare‐earth cation (Nd3+) moment. [ABSTRACT FROM AUTHOR]

0.39Bi(Ni0.5Ti0.5)O3–0.20PbZrO3–0.41PbTiO3:x(Bi2O3 + PbO) (BNPZT:xBiPb, x = 0, 1, and 2) piezoceramics were prepared via conventional solid-state route. The impact of excess Bi2O3 and PbO on the structural, dielectric, ferroelectric, bipolar strain, and piezoelectric properties of BNPZT ceramics was investigated. The Rietveld refinement results indicated that all sintered ceramics were well crystallized into a pure perovskite structure with major rhombohedral and minor tetragonal phases. The temperature and frequency dependence of dielectric measurements revealed relaxor behavior and a high Curie temperature (Tc ~ 290 °C) for BNPZT:1BiPb ceramics. High remnant polarization (Pr ~ 25.43 μC/cm2), low coercive field (Ec ~ 16.73 kV/cm), and bipolar strain (0.12%) were achieved in BNPZT:1BiPb ceramics. This study outlines a route for exploring new piezoelectric materials with enhanced electrical properties. [ABSTRACT FROM AUTHOR]

The temperature–composition structural phase diagram of the BTO‐based ferroelectric system Ba0.94Ca0.06Ti1−xHfxO3 (0.05 ≤ x ≤ 0.15) is investigated using high‐angular resolution synchrotron X‐ray powder diffraction and dielectric permittivity measurements. In contrast to the well‐known structural phase transition sequence of the parent compound BaTiO3 (rhombohedral → orthorhombic → tetragonal → cubic, upon heating), Hf4+ doping into Ba0.94Ca0.06Ti1−xHfxO3 results in the gradual disappearance of the intermediate orthorhombic and tetragonal phases at two different, but close, critical concentrations, 0.10 < xc1 < 0.12 and 0.12 < xc2 < 0.135, respectively, revealing the presence of two triple points in the phase diagram. [ABSTRACT FROM AUTHOR]

This study investigates the structural, electrical, leakage current, and magnetic characteristics of the double perovskite material Nd2NiTiO6 synthesized through the sol–gel citrate auto‐ignition method. The Rietveld refinement of the X‐ray diffraction patterns confirmed a monoclinic symmetry (space group P21/n) with an ordered arrangement of alternate NiO6 and TiO6 octahedra. Impedance spectroscopic analysis exhibited the material's non–Debye‐type relaxation mechanism and semi‐conductive nature. AC conduction analysis revealed that the conduction of charge carriers occurs via the nonoverlapping small polaron hopping mechanism, consistent with Mott's variable range hopping model. Temperature‐ and frequency‐dependent dielectric measurements were interpreted using the Maxwell–Wagner interfacial polarization model. The analysis of thermal‐ and field‐dependent leakage currents established that conduction is ohmic, which the Schottky barrier model explains. Studies on magnetization ruled out the presence of magnetic ordering connected to indirect interaction between Ni2+ ions via Ti4+ ions and the rare‐earth cation (Nd3+) moment. [ABSTRACT FROM AUTHOR]

In this electronic era, there is a demand to switch from conventional polymers to conducting biopolymers. We developed conducting biopolymer nanocomposites of cashew gum (CG) and polypyrrole (PPy) with zinc oxide (ZnO) nanofillers [CG/PPy/ZnO] via in‐situ oxidative polymerization using a sustainable solvent. These nanocomposites were characterized using Fourier‐transform infrared spectroscopy (FTIR), UV–visible spectroscopy, field emission scanning electron microscope (FE‐SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The FTIR signal at 855 cm−1 confirms the successful inclusion of ZnO nanofillers into the biopolymer. UV–vis absorption of the blend nanocomposite increases with the nanoparticle doses. Among the various blend nanocomposites, the least bandgap energy was observed for 7 wt% ZnO loading. FE‐SEM revealed homogeneous dispersion of ZnO nanofillers in the CG/PPy blend at 7 wt% ZnO. TGA and DSC demonstrated that the CG/PPy/ZnO nanocomposites have better thermal stability and glass transition temperature than the pure polymer blend, indicating enhanced thermal properties. The CG/PPy/7 wt% ZnO showed the highest conductivity, 4.62 times greater than the pristine blend at 100 Hz. Dielectric constant, activation energy, AC conductivity and dielectric loss measurements demonstrated that the nanocomposites outperformed the pure polymer blend. Complex impedance analysis revealed increased impedance with rising temperature. Overall, CG/PPy/ZnO nanocomposites exhibit superior optical, morphological, thermal, electrical, and dielectric properties, making them promising for energy storage and optoelectronic applications. Highlights: Ecofriendly synthesis of CG/PPy/ZnO nanocompositesEnhancement in optical, structural, and thermal properties of CG/PPy/ZnODielectric properties and temperature‐dependent AC conductivity are summarized.Blend nanocomposite shows higher AC conductivity and dielectric constantCG/PPy/ZnO nanocomposites are suitable for energy storage applications [ABSTRACT FROM AUTHOR]

Cu2+‐ion‐doped cobalt ferrites with the chemical formula Co1–xCuxFe2O4 (0 < x ≤ 0.20) are prepared using the citrate–nitrate autocombustion method. The structural properties of the synthesized samples are examined by X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The XRD studies reveal the formation of a single‐phase spinel cubic structure. A slight variation in the peak position is observed with the addition of Cu2+ ions. The proposed cation distribution is supported by X‐ray relative intensity calculations. FTIR and Raman spectroscopy studies also confirm the formation of a single‐phase cubic structure. Field‐emission scanning electron microscopy (FESEM) is used to measure the surface properties of the samples. The FESEM images reveal nearly uniform‐sized grains with the addition of Cu2+ ions. The DC electrical resistivity is determined using the conventional two‐probe technique and is typically found within the range of 106 Ω cm−1. Dielectric measurements are performed using an impedance analyzer with 100 Hz–10 MHz frequency range and the variations in the dielectric properties are discussed. The magnetic properties are measured using a vibrating sample magnetometer conducted the magnetic measurements. The uneven variations in the magnetic properties are explained based on Neel's two‐sublattice model. [ABSTRACT FROM AUTHOR]

Cr-substituted Ni 2 U hexaferrite series (Ba 4 Ni 2 Fe 36-x Cr x O 60 for x = 0.0 to x = 2.0 with a step size of 0.5) was prepared via sol-gel auto-combustion route and annealed at 1200 °C for 6 h. The samples were investigated using XRD, FTIR, SEM, XPS, and high frequency (1 MHz–6 GHz) dielectric and microwave absorption measurements (VNA). XRD studies revealed that Cr3+ ions successfully substituted in BaNi 2 U-type hexaferrite and have a single-phase structure. The average crystallite size decreased while the percentage of porosity increased with the substitution. FTIR spectra confirmed the formation of the hexaferrite phase in all compositions. SEM micrographs revealed that the prepared samples are hexagonal. XPS spectra show the presence of all constituent elements in the samples. The dielectric constant, dielectric loss, and A.C. conductivity of samples was analyzed. Cole-Cole plots with single semicircles of different radii show the grain and grain boundaries affecting the conduction process. Moreover, Cr-substitution enhanced the microwave absorption capability. The hexaferrite sample Ba 4 Ni 2 Fe 35 Cr 1.0 O 60 , with a pellet thickness of 1.81 mm, showed the highest M.W. absorption at 1.09 GHz frequency with a reflection loss (R.L.) value of −55 dB. The hexagonal-shaped morphology, high porosity, and enhanced reflection loss value suggest their use in high-frequency microwave applications. [ABSTRACT FROM AUTHOR]

Proton-conducting metal–organic frameworks (MOFs) have attracted tremendous attention for their promising application in proton-exchange membrane fuel cells. Water clusters play an extremely important role in the proton-conduction process and affect the proton conductivity of host materials. To date, the close-packing effect of water clusters within pores on proton conductivity due to the amorphous structure of commercial proton-exchange membranes is unclear. Herein, we prepared two crystalline MOFs containing different water clusters, namely, [Sm2(fum)3(H2O)4]·3H2O (Sm-fum-7H2O) and [Er2(fum)3(H2O)4]·8H2O (Er-fum-12H2O) (H2fum = fumaric acid), and regulated their proton conductivities by changing the water clusters. As expected, Sm-fum-7H2O showed a high proton conductivity of 6.89 × 10−4 S cm−1 at 333 K and ∼97% RH because of the close packing of the water clusters within the pores triggered by a lanthanide contraction effect, outperforming that of Er-fum-12H2O and some previously reported MOFs. Additionally, Sm-fum-7H2O and Er-fum-12H2O demonstrated high dielectric functions, reaching 2.22 × 103 and 1.42 × 105 at 102.5 Hz, respectively, making Er-fum-12H2O a highly dielectric material. More importantly, broadband dielectric spectroscopy measurements indicated that there was a dielectric relaxation process in Er-fum-12H2O with an activation energy of 0.59 eV. The present findings provide a better understanding of the crucial role of confined water clusters in proton conductivity and the novel phenomenon of the coexistence of proton conduction and dielectric relaxation in crystalline MOF materials. [ABSTRACT FROM AUTHOR]

Solution combustion synthesis (SCS) has proven to be one of the simplest and fastest methods, using inexpensive materials and resulting in homogeneous stoichiometry with nanometric particle sizes. The spark plasma sintering (SPS) method has been used to obtain high‐density ceramic materials with excellent control of microstructure. This work reports the successful combination of these two techniques for the fabrication of the high‐density lead‐free ferroelectric system (1‐x)Ba(Zr₀.₂Ti₀.₈)O₃‐x(Ba₀.₇Ca₀.₃)TiO₃. The X‐ray diffraction of the powder indicates the majority formation of the perovskite structure and other residual reaction products, indicating a reactive powder. The SPS method resulted in highly densified samples, reaching relative density values close to 99% with a single‐phase perovskite structure. Rietveld refinement revealed the presence of at least two perovskite phases, independent of calcium concentration. Dielectric measurements showed anomalies in both the real and imaginary parts of the dielectric permittivity, which are typical of phase transitions and a low dielectric loss for all compositions. This study shows that the combined use of SCS and SPS technique can be a powerful protocol to produce dense, fine‐grained lead‐free ferroelectric ceramics at relatively low temperatures and in short time periods. [ABSTRACT FROM AUTHOR]

This paper presents an approach to prevent the incorrect transfer of fuel to the wrong tank during refueling. An experimental setup was developed to perform ultrasonic and dielectric measurements on diesel, gasoline, ethanol, and water. The fuel types were determined using an ultrasonic sensor and time-of-flight values were measured at various temperatures. Additionally, the dielectric coefficients of these liquids were measured to determine the liquid types using a dielectric sensor. The results obtained from both the ultrasonic and dielectric methods are systematically compared, and the advantages and disadvantages of each approach are thoroughly discussed. It was observed that dielectric method does not always yield accurate results. The proposed system effectively prevents erroneous transfer of fuel to the tank during refueling. The developed system may be used in practice to distinguish fuel types. In addition, a new approach using machine learning techniques to determine fuel type is presented. Fuel types were classified using 33 machine learning algorithms such as support vector machines, artificial neural networks and K-Nearest neighbors. It seems that artificial neural network with first layer size 25 and quadratic discriminant classifiers have achieved remarkable results with a success rate of 94% in classification. The results highlight the important and effective role of ultrasonic sensors in accurately identifying fuel types, leading to more efficient and safer storage and transportation of fuel. It is also concluded that machine learning techniques can be used effectively in identifying and classifying fuel types. The approach involving ultrasonic and artificial intelligence techniques was particularly innovative in distinguishing fuel types. [ABSTRACT FROM AUTHOR]

In the last decade, it has been shown that in most cases atmospheric ice consists of a mixture of ices Ih and Ic; this is called ice with stacking disorder, or stacking disordered ice (Isd). In addition, the existence of another crystalline modification of ice, called ice 0, has became known. Ice 0 is a transitional form from deeply supercooled water to Ih and Ic ices, which form at temperatures below –23°C (at low pressures). For this reason, the question arose about the possibility of forming ice 0 in the structure of ice Isd. To clarify the issue, laboratory experiments were carried out to obtain layers of ice 0 on the surface of ice Ih, as well as dielectric measurements of the material of atmospheric ice from fallen hail. The results confirmed the possibility of forming ice 0 in the structure of stacking disordered ice Isd. One special property of such a structure is the appearance of contact layers with high conductivity, which significantly changes the electrophysical characteristics of ice particles. For example, in particles of small sizes, resonances of plasmon oscillations arise, which affect the transfer of electromagnetic radiation in cloud formations. The study of electromagnetic properties of small ice particles containing ice 0 and their features in various areas of the atmosphere will make it possible to solve a number of important tasks. These include refining the radiation balance of the Earth's surface, thunderstorm phenomena, radiation transfer in cloud formations, and physicochemical processes in aerosols and snow covers. [ABSTRACT FROM AUTHOR]

Poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVdF‐HFP)‐sodium thiocyanate (NaSCN) solid polymer electrolytes containing different weight ratios of ionic liquid (IL)—tributylmethylphosphonium iodide (TBMPI) were prepared using solution‐cast approach. Electrochemical impedance data indicates that increasing ionic liquid into polymer electrolyte matrix increases ionic conductivity and the maximum value of ionic conductivity was obtained at 150 wt% TBMPI, having conductivity value of 8.3 × 10−5 S cm−1. The dielectric measurement supports our conductivity data. Ionic transference number measurement affirms this system to be predominantly ionic in nature, while electrochemical stability window (ESW) was found to be 3.4 V. Polarized optical microscopy (POM) along with differential scanning calorimetry (DSC) suggest suitability of TBMPI as plasticizer, while infrared spectroscopy (FTIR) confirms ion interaction, complexation, and composite nature. The thermogravimetric analysis (TGA) shows thermal stability of these ionic liquid‐doped polymer electrolytes (ILDPEs). Using maximum conducting ILDPE, a sandwiched supercapacitor has been fabricated which shows stable performance as high as 228 Fg−1 using cyclic voltammetry (CV). [ABSTRACT FROM AUTHOR]

In this study, Ni/Ba co-doped NaNbO3 ceramics (NBNNOx) were synthesized using a solid-state method to explore the effects of Ni2+ and Ba2+ ion substitution on the structural, optical, and dielectric properties of NaNbO3. X-ray diffraction (XRD) confirmed that the ceramics retained an orthorhombic structure, with crystallinity improving as the doping content (x) increased. Significant lattice distortions induced by the Ni/Ba co-doping were observed, which were essential for preserving the perovskite structure. Raman spectroscopy revealed local structural distortions, influencing optical properties and promoting relaxor behavior. Diffuse reflectance measurements revealed a significant decrease in band gap energy from 3.34 eV for undoped NaNbO3 to 1.08 eV at x = 0.15, highlighting the impact of co-doping on band gap tunability. Dielectric measurements indicated relaxor-like behavior at room temperature for x = 0.15, characterized by frequency-dependent anomalies in permittivity and dielectric loss, likely due to ionic disorder and structural distortions. These findings demonstrate the potential of Ni/Ba co-doped NaNbO3 ceramics for lead-free perovskite solar cells and other functional devices, where tunable optical and dielectric properties are highly desirable. [ABSTRACT FROM AUTHOR]

The open-ended coaxial probe method is the most commonly used approach for retrieving the dielectric properties of human tissues. This method is also often used to identify cancer because of the difference between the dielectric properties of normal and malignant tissues. This technique not only ensures quick measurement but also has a good identification effect. Although it has the potential to be utilized in tumor surgeries, its clinical application is hindered by the lack of an established identifiable tumor size. In this study, we examine the minimum detectable size of liver tumors by simulation and Mann–Whitney U test. Then, a phantom experiment was conducted to verify the simulation results. For Probes 1, 2, 3, and 4, the smallest cancer tumor detectable size is 0.59, 1.05, 1.85, and 2.95 mm radius, respectively. Furthermore, an evaluation approach for investigating the minimum detectable size of tumors through different probes is proposed. The results showed that the identification sizes were affected by the frequency and size of the probe. Moreover, the minimum detectable size of liver cancer and the crucial factors were investigated in this work. [ABSTRACT FROM AUTHOR]

The effect of the grain size on the dielectric properties and electrical conductivity was studied for single-phase solid solution of the ZrO2–CeO2 system with 75% CeO2. The bi-ceramic composition of ZrO2–CeO2 as Ce0.75Zr0.25O2 was prepared through a solid-state reaction to synthesize single-phasic material followed by high-energy ball milling to make finer particle size. Structural properties were confirmed through advanced analytical techniques such as XRD and Raman spectroscopy. SEM confirmed large porosity with a grain size of 204 ± 3 nm, which is larger than the crystallite size of 22.64 ± 8.6 nm calculated from the XRD analysis for Ce0.75Zr0.25O2. The dielectric measurements were performed as a function of temperature by impedance spectroscopy. The relative dielectric constant decreases on increasing frequency for all temperatures, which validates the polar nature of nanocrystalline Ce0.75Zr0.25O2 ceramic. In addition, temperature-dependent enhancement in ε r is more pronounced in low-frequency regions due to low-frequency dielectric dispersion phenomena. The dielectric loss also increases with increasing temperature over the frequency region from 100 Hz to 2 MHz. The electrical conductivity of nanocrystalline Ce0.75Zr0.25O2 was found to be smaller than the micron-sized sample of Ce0.75Zr0.25O2. The present study revealed the crucial role of grain size in tuning the dielectric properties of Ce0.75Zr0.25O2 along with ac conductivity. [ABSTRACT FROM AUTHOR]

Understanding the nanoscale electrostatic interaction between a conductive atomic force microscopy (AFM) probe and a dielectric film is central to the operation of various nanoscale dielectric microscopies and determination of dielectric properties of the film. There is no simple analytical description of the electrostatic interaction generated in the confined probe-sample geometry for neither static nor dynamic AFM modes used in dielectric measurements. An accurate description of the involved physics is obtained only by means of a finite element analysis modeling of the system. However, the alternative to using the numerical analysis is not very popular due to being slower and requiring relatively high computation resources. In this work, we revised the contributions from different parts of the AFM probe to the probe-sample capacitance by both analytical and numerical methods. We tried to reconciliate the two approaches and observed the differences as a function of geometry and material parameters. Under various noise levels, the efficiency of an analytical model was tested against a finite element analysis that captures in detail the electrostatic interaction in AFM-based dielectric measurements. The investigation was performed in both spectroscopic force-distance curves and constant height scans with measurements for deflection and frequency of the AFM probe. The obtained measurement sensitivities are relevant in selecting the optimal scanning mode and its operational parameters for a given film thicknesses and dielectric constants but also show the critical role of the numerical analysis to the correct interpretation of the measurements. [ABSTRACT FROM AUTHOR]

The microwave (MW) dielectric permittivity of gallium oxide (β-Ga2O3) fundamentally determines its interaction with an electromagnetic wave in bulk power. Yet, there is a lack of experimental data due to limitations of high-temperature MW dielectric measurements and the large uncertainty under variable-temperature conditions. Herein, we develop a deep potential (DP) based on density functional theory (DFT) results and apply deep potential molecular dynamics (DPMD) for accurately predicting temperature-dependent MW dielectric permittivity of β-Ga2O3. The predicted energies and forces by DP demonstrate excellent agreement with DFT results, and DPMD successfully simulates systems up to 1280 atoms with quantum precision over nanosecond scales. Overall, the real part of the MW dielectric permittivity decreases with rising frequency, but the dielectric loss increases. The MW dielectric permittivity gradually increases as the temperature increases, which is closely related to the reduced dielectric relaxation time and increased static and high-frequency dielectric constants. Besides, the oxygen vacancy defects significantly reduce the relaxation time; however, augmenting the defect concentration will cause a slight rise in relaxation time. The electron localization function analysis reveals that more free electrons and low localization of electrons produced by high defect concentrations facilitate the increased relaxation time. This study provides an alternative route to investigate the temperature-dependent MW permittivity of β-Ga2O3, which attains prime importance for its potential applications in RF and power electronics. [ABSTRACT FROM AUTHOR]

With the increasing demand for high‐performance printed circuit boards (PCBs) in the 6G communication era, dielectric substrate materials must exhibit a low dielectric constant (Dk), low dielectric loss (Df), and high dimensional stability. In this study, a series of bismaleimide‐incorporated poly(phenylene ether) resins (PPE‐BMI) with varying bismaleimide (BMI) crosslinker contents is developed, exhibiting significantly enhanced dielectric properties and dimensional stability, owing to the restricted polymer chain mobility and increased crosslinking density. Dielectric property measurements reveal that the PPE‐BMI resins exhibit low Dk and Df values at frequencies above 100 GHz, while maintaining an excellent dielectric performance even after an 85 °C/85% relative humidity reliability test. A significant reduction in the coefficient of thermal expansion is observed with an increase in the BMI content. Molecular dynamics simulations are employed to clarify the role of BMI crosslinkers in reducing the free volume, enhancing the crosslinking in the PPE (poly(phenylene ether)) matrix, and influencing the thermophysical properties of PPE‐BMI. The infiltration of PPE‐BMI into glass fabrics and liquid crystal fabrics highlights their potential for practical use in advanced PCB applications operating at high frequencies. [ABSTRACT FROM AUTHOR]

In this study, LiGaCr4−xFexO8 (x = 0, 0.2, 0.4, 0.6) ceramics are synthesized using the solid‐phase reaction method. The effects of Fe doping on the lattice structure and dielectric properties are systematically examined using X‐ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and dielectric measurements. It is found from XRD analysis that the evolution of lattice constant decreases from 8.2552 Å at x = 0 to 8.2449 Å at x = 0.6, demonstrating a lattice contraction with doping. SEM shows a grain size reduction and irregular structures with higher Fe doping levels developed. The grain size decreases from 1.716 μm at x = 0 to 1.155 μm at x = 0.6. Due to Fe doping, the Raman spectroscopy obviously changes in high‐frequency phonon modes. The F2g1 and A1g modes shift to higher frequencies due to the reduction in lattice constant, while the F2g2, F2g3, and Eg modes shift to lower frequencies due to the increased ionic mass caused by the heavier Fe ions. Notably, Fe doping increases the dielectric constant and reduces the dielectric loss, especially at higher doping level. In these results, it is suggested that moderate Fe doping improves dielectric properties, offering potential applications in microwave and high‐frequency devices. [ABSTRACT FROM AUTHOR]

Single crystals of Thiourea Cadmium hydrogen borate (TCHB), a hybrid nonlinear optical (NLO) material, are grown from an aqueous solution by slow evaporation solution growth technique at ambient temperature. Characterization studies have been conducted to probe the nonlinear effects of the crystal. The crystalline nature of TCHB is explored using the single crystal X-ray diffraction technique. The chemical composition is resolved by the Fourier transform infrared (FTIR) spectroscopy and energy dispersive X-ray analysis. UV–Vis spectral studies analyze the transparency of the crystal. Optical studies illustrate the UV cut-off wavelength to be 285 nm with wide window of transparency in the infrared and visible regions. The optical and electrical conductivity studies indicate superior optical response essential for optical computing and photonic applications. The Kurtz powder test has confirmed the NLO capability. The thermal stability is analyzed through a thermogravimetric study. Dielectric and AC conductivity measurements carried out over a wide range of frequencies (100 Hz to 5 MHz) for various temperatures establish the semiconducting and photonic capacity of TCBH crystal to be used as photodiodes, optical fibres and laser lights. [ABSTRACT FROM AUTHOR]

Humanned exploration and extended stay on the Moon are the hottest challenges today. We report highly robust materials by microwave heating under high-vacuum conditions (10− 3 Pa) from a basaltic regolith simulant (FJS-1) to ensure the feasibility of lunar infrastructure construction. The violent degassing dynamics were revealed by monitoring vacuum pressure during heating and analyzing the compounds evolved from basaltic silicate compounds: thermal pyrolysis of silicate compounds became more pronounced above 1000 oC, leading to a catastrophic deformation accompanied by forming countless pores of several hundred µm sizes. The preferential formation of the magnetite phase in vacuum heating dominantly caused the radical change in microwave absorption capacity compared with conventional heating routes using an electrical furnace in atmospheric conditions. Besides, the in-situ measurement of dielectric properties during microwave vacuum heating clarified the increase in one order of magnitude from 100 to 1000 oC. Based on the presumed phenomena during microwave-vacuum heating for basaltic regolith, we propose a new thermal design concept to overcome the practical limitations of microwave technology. The multi-step temperature profile successfully fabricated a highly robust product that demonstrated world-class mechanical performance, equivalent to the compressive strength of 65 MPa without any vigorous hydrostatic cold press as a pre-treatment. [ABSTRACT FROM AUTHOR]

This comparative study investigates the difference between the transition metal (Ru) and rare earth element (Gd) as dopants in NiO nanoparticles, to unveil their suitability in various applications. Pure, Ru- and Gd-doped NiO nanoparticles have been synthesized by the chemical co-precipitation method, in the presence of polyvinylpyrrolidone, as a capping agent. The EDX pattern revealed the purity, the un-stoichiometric nature of the synthesized nanoparticles, and the influence of the Ru- and Gd-dopants in generating advantageous structural imperfections, including oxygen and nickel vacancies. The dielectric and conductivity measurements have provided valuable insights into the electrical behavior of Ru- and Gd-doped NiO nanoparticles. The influence of the Ru- and Gd-dopants on the Debye model, universal dielectric model, and relaxation mechanism was implemented. The dielectric constant was affected by the dopants, where the Ru-dopants reduced it by a factor of 0.24, however, the Gd-dopants boosted it by a factor of 4. Moreover, the opposing influence of the Ru- and Gd-dopants on the nickel vacancies has tuned the ac conductivity of the NiO lattice, where it was reduced by 75 % with Ru-dopants due to the suppressed nickel vacancies and enhanced by 70 % with the Gd-dopants due to the augmented nickel vacancies. The dc conductivity was examined at ranging temperatures to explore the conduction mechanism and the effect of the dopants. The multi-functional ability of the pure, Ru- and Gd-doped NiO nanoparticles was tested by studying the complex power and temperature coefficient of resistance (TCR), from which the dominating capacitive and resistive nature is identified for the samples. Besides, NiO nanoparticles have attained a maximum TCR value of −10.41 %, rendering it a superior material for bolometric devices, even better than the used conventional materials. The studied dielectric and conductive properties unveiled the potential applicability of the samples in microelectronics, storage capacitor applications, and bolometric devices. [Display omitted] [ABSTRACT FROM AUTHOR]