Dielectric Loss Values Research Articles

Significantly Improved dielectric performance and Vickers-Hardness in High-Entropy TiO2-based Ceramics

Remarkable dielectric properties and enhanced hardness were achieved in high-entropy TiO2-based ceramics in this work by incorporating multiple pairs of donor-acceptor (D-A) cations (D = Nb5+, A = In3+, Al3+, Fe3+, Ga3+, La3+). The introduction of high-entropy engineering may facilitate the creation of favorable and stable microstructural features as lattice distorted and localized defect cluster, thereby enhancing the dielectric performance, thermal stability and mechanic properties. The composition of [Nb0.5(In0.2Al0.2Fe0.2Ga0.2La0.2)0.5]0.01Ti0.99O2 exhibits remarkably colossal permittivity (εr) value of approximately 18488 and low dielectric loss (tanδ) value of around 0.014 at 1 kHz. Furthermore, the thermal stability of the dielectric permittivity for [Nb0.5(In0.2Al0.2Fe0.2Ga0.2La0.2)0.5]0.01Ti0.99O2 ceramic meets the X9D standard, and the dielectric loss stays below ∼ 0.05 in the temperature range from -55 to 150 °C. Besides, the Vickers-hardness of [Nb0.5(In0.2Al0.2Fe0.2Ga0.2La0.2)0.5]0.01Ti0.99O2 gets increased by over 37% as compared to that of (Nb5+, In3+) co-doped ceramic (INTO). We presented in this work the influence of high-entropy on the dielectric and mechanic properties of TiO2-based ceramics, offering valuable insight into future development of colossal dielectric ceramics.

Thermal and Dielectric Properties of EuF3: Gd @ Tryptophan

Abstract EuF3: Gd @ tryptophan was synthesized via aqueous solution route at room temperature. The XRD studies shows hexagonal phase of synthesized nanoparticles with lattice parameters a = b = 6.966 (A°), c = 7.322 (A°). The lattice parameter values are in good agreement with (JCPDS card no 32-0373). The particle size of nanoparticles was calculated using Debye-Scherer formula and it is found to be 73.54 nm. Nanoparticles has flake like morphology having size of the order of 56 nm – 71 nm with nanoparticles has average size of 13 nm. The TEM image shows globular aggregates with assorted size were also seen with diameter 56 nm – 71 nm from which the flower like star structures originates. The TGA/DTA analyses of synthesized sample were studied up to 1500°C at heating rate of 0.01°C – 100°C/min. The variation in dielectric constant ε′, dielectric loss ε″ and tangent loss (tan δ) with frequency (100 Hz – 5 MHz) was studied at room temperature. The dielectric constant and dielectric loss are found to decrease exponentially with frequency. The low value of dielectric loss at higher frequencies indicates its use in electronic industry.

Electrochemical properties of plasticized PVA-based electrolyte inserted with alumina nanoparticles for EDLC application with enhanced dielectric constant

In the current study, the role of alumina nanoparticles was examined in the electrochemical and device performance of PVA-based electrolytes. The NaSCN was used as a cation provider for the host electrolyte, and the glycerol plasticizers were used to enhance conductivity and flexibility. The ratio of salt and plasticizer was fixed, while nanoparticles were varied. The results of impedance AC conductivity confirm that 3 wt% of alumina insertion results in high DC conductivity, which is sufficient for electrochemical device application. Electrode polarization region and plateau area are clearly distinguished in AC spectra. The study of the Dielectric constant reveals that charge storage is maximum at 3 wt% of alumina. The dielectric constant values are about twice the dielectric loss value, which is the topic of immense scientific discussion. The contribution of ion fraction was found to be 0.94, which is excellent compared to the negligible contribution of electrons, which is about 0.05. Electrochemical stability is an additional crucial factor and was found to be 2.47 V. To identify any Redox or non-Redox phenomena occurring in the electrical double-layer capacitor (EDLC) cyclic voltammetry (CV) as the simplest analysis method has been carried out on the sample having the highest DC value. A leaf-like form of the CV plot was noticed at high scan rates, while a rectangular shape was identified at low scan rates. The charge-discharge shape is almost close to the ideal triangular pattern. The discharge part was used to calculate critical EDLC device parameters such as ESR, efficiency, specific capacitance power density, and energy density over 2000 cycles. Low ESR (below 60 Ω) and stable efficiency (almost 100 %) of the device results in high capacitance (≈87 F/g), power density (2978 Wh/kg), and energy density (12.86 W kg−1). The results established that nan-fillers alongside plasticizer is crucial to deliver EDLC devices with improved performances.

Diphenylphosphine oxide derivative with a symmetrical structure as an efficient flame retardant for application in epoxy resin

AbstractA fresh phosphorus‐containing fireproofing agent (oxybis(4,1‐phenylene))bis((2,5‐dihydroxyphenyl)(phenyl)phosphine oxide) (ODDPO‐HQ) was synthesized by a simple two‐step reaction. The effect of ODDPO‐HQ on the glass transition temperature (Tg), crosslinking density, thermal stability, fire resistance, dielectric performances, hydrophobicity, and water absorption of epoxy resin (EP) was studied. EP/ODDPO‐HQ containing 1.2 wt% phosphorus not only achieved the vertical burning V‐0 grade with a limited oxygen index of 28.9% but also maintained good thermal stability. Compared to unmodified EP, its Tg value has only decreased by 7.2°C. Detailed studies revealed that the excellent flame resistance of ODDPO‐HQ for epoxies was ascribed to the flame suppression both in the gaseous phase and condensed phase, especially the obvious barrier effect. Although the water uptake of the modified epoxies slightly rose with the content of ODDPO‐HQ caused by the reduction of the crosslinking density within the matrix, it did not adversely affect the properties of the polymer. The modified epoxies showed reduced dielectric constant and dielectric loss values, and the contact angle of EP/ODDPO‐HQ samples increased as the flame retardant content rose, which might be due to the symmetrical structure of ODDPO‐HQ reducing the polarity. Our study presents an easy approach for producing high‐performance epoxies.

Enhancement of the thermal, electrical properties and mechanical properties of graphene doped novel copolymers bearing coumarin side groups

In this study, a new monomer 3-acetyl coumarin-7-ylacrylate (Ac-Kum) was synthesized. A series of copolymer were prepared by using (Ac-Kum) and methyl methacrylate (MMA) in different ratios. The structure characterization of the compounds was carried out by FT-IR, 1H NMR and 13C NMR spectroscopic techniques. Graphene doped polymer composites were prepared at different rates (1 %, 2 % and 5 %). The thermal behavior of the polymer composites were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) methods. Thermal stability of 1 %, 2 % and 5 % graphene composites of homopolymer was determined as 324 °C, 345 °C and 350 °C, respectively. The dielectric properties of the polymer composites were investigated as a function of frequency. Dielectric constant, dielectric loss and ac conductivity values of homopolymer were determined as 6.13, 0.11, 1.02 × 10−09 S/cm and 5 % graphene composite were determined 49.30, 7259, 9.26 × 10−07, respectively. Microhardness tests were carried out under a load of 100 g and in 10 s. The microhardness values were calculated by taking the average of the microhardness values taken from the surface of the samples from five different points. The highest microhardness value is the 5 % graphene added P(Ac-Kum) sample. Wear tests were carried out with a pin-on-disc wear tester under single load (10N) and in dry conditions with a total sliding distance of 10 m and a sliding speed of 5 mm/sec. Disc samples with a diameter of 13 mm were placed in the sample holder part of the test device. The highest wear resistance sample is the P(Ac-Kum) 5 % graphene composite.

Low Sintering Temperature Effect on Crystal Structure and Dielectric Properties of Lead-Free Piezoelectric Bi0.5Na0.5TiO3-NaFeTiO4

Bi0.5Na0.5TiO3 (BNT) emerges as a promising ferroelectric and piezoelectric lead-free candidate to substitute the contaminant Pb[TixZr1−x]O3 (PZT). However, to obtain optimal ferroelectric and piezoelectric properties, BNT must be sintered at high temperatures. In this work, the reduction of sintering temperature by using iron added to BNT is demonstrated, without significant detriment to the dielectric properties. BNT-xFe with iron from x = 0 to 0.1 mol (∆x = 0.025) were synthesized using high-energy ball milling followed by sintering at 900 °C. XRD analysis confirmed the presence of rhombohedral BNT together with a new phase of NaFeTiO4 (NFT), which was also corroborated using optical and electronic microscopy. The relative permittivity, in the range of 400 to 500 across all the frequencies, demonstrated the stabilization effect of the iron in BNT. Additionally, the presence of iron elevates the transition from ferroelectric to paraelectric structure, increasing it from 330 °C in the iron-free sample to 370 °C in the sample with the maximum iron concentration (0.1 mol). The dielectric losses maintain constant values lower than 0.1. In this case, low dielectric loss values are ideal for ferroelectric and piezoelectric materials, as they ensure minimal energy dissipation. Likewise, the electrical conductivity maintains a semiconductor behavior across a range of 50 Hz to 1 × 106 Hz, indicating the potential of these materials for applications at different frequencies. Additionally, the piezoelectric constant (d33) values decrease slightly when low concentrations of iron are added, maintaining values between 30 and 48 pC/N for BNT-0.025Fe and BNT-0.05Fe, respectively.

Structural, optical absorption and electrical characteristics of sol-gel synthesized chromium-doped bismuth ferrites

Multiferroic materials have remarkable and several technical uses such as random-access multi-state memories, solar cell devices, data storage recording technologies, etc. An attempt has been made here to synthesize chromium-doped Bi(Fe1-xCrx)O3 (x = 0–0.10) oxides via citrate based sol-gel route and characterized with regards to structural, optical absorption and electrical properties. It depicts a rhombohedral structure with space group R3c for BiFeO3 and Bi(Fe0.98Cr0.02)O3 compositions. The lattice parameters for BiFeO3 on rhombohedral axes are aR ∼5.796 Å, α ∼59.34° which decreases linearly with chromium (x). Similarly, the parameters on hexagonal axes also decrease as aH ∼5.739–5.730 Å, and cH ∼14.269–14.262 Å. However, chromium doping causes a drop in crystallite size and rise in dislocation density. The absorption spectra show a broad peak at λ = 392 nm (for x = 0) and a broader as well as high intense peak for x = 0.02 (λ∼ 393 nm) which is attributed to charge transfer transitions from O2− (2p) valence band to Fe -3d (eg and t2g split levels) conduction band. Band at λ ∼310 nm is associated to the band gap (Eg) of material. Composition Bi(Fe0.98Cr0.02)O3 (x = 0.02) exhibits the highest values of the dielectric constant (εr ∼ 1102), loss (tan δ ∼ 1.1), and least value of impedance. The Cole-Cole plot depicts a depressed semi-circle and indicates presence of loss due to grains only. The room temperature P–E hysteresis loop with remanent polarization (Pr = 0.11439 μC/cm2) and leakage current density (J = 1.1 μA/cm2) are found maximum for Bi(Fe0.98Cr0.02)O3 (x = 0.02). The I-E loop and frequency-dependent P-E loops depict ferroelectric nature of all compositions. The analysis of leakage current density and slope values infer the presence of space charge limited conduction (SCLC) mechanism. These findings suggest materials applications in recent technologies.

Enhanced Dielectric, Thermal, Energy Storage, Quality Factor, Impedance, and Conductivity Properties of Novel PVDF/PAN/ZrO2 Polymer Nanocomposites for Flexible Electronics Applications

ABSTRACTIn this study, novel polymer nanocomposite films based on polyvinylidene fluoride/polyacrylonitrile/zirconium dioxide (PVDF/PAN/ZrO2) were prepared using a solution casting technique. The structural modifications and morphological properties were analyzed by x‐ray diffraction (XRD) and high resolution scanning electron microscopy (HRSEM). The obtained results verified the filler‐polymer interactions and uniform dispersion of the ZrO2 filler in the host polymers (PVDF and PAN). Thermal stability of up to 46% leftover residue for 30% ZrO2 nano‐filler loading in the blend polymer nanocomposite was analyzed by thermogravimetric analysis (TGA). The dielectric properties such as dielectric constant and dielectric loss values and impedance, Q‐factor, and AC conductivity were analyzed using an impedance analyzer. The decrement in impedance with increasing nano‐filler content with improved dielectric, thermal, Q‐factor, energy density and conductivity properties signifies the prepared novel PVDF/PAN/ZrO2 polymer nanocomposite as an effective material for flexible electronics applications.

Microstructural, dielectric, electrical, electromagnetic, and magnetic property enhancements in GdIG /TrIG/ Mn0.2Co0.3Zn0.5Fe2O4 ferrites composites for electronic devices application

Gadolinium garnet ferrite (GdIG) and terbium garnet ferrite (TrIG), known for their favourable magnetic and dielectric characteristics, were combined with doped zinc spinel ferrite (GdIG)x-(TrIG)y/Mn0.2Co0.3Zn0.5Fe2O4(1-x-y) (at x=1 y=0, x=0 y=1, x=y=0.5, x=y=0.25, x=y=0) to achieve improved permittivity, permeability and magnetic properties with reduced magneto-dielectric losses. Our study details the synthesis process and the resulting enhancements in structural, magnetic, and dielectric properties of the prepared samples. Analysis of the X-ray diffraction (XRD) patterns confirmed the presence of a crystalline structure characterized by both cubic spinel and cubic garnet phases in the composites. The microstructures of the composites were analysed with field emission scanning electron microscopy (FESEM), revealing the variation in a grain size from 0.11 μm to 0.96 μm at x =y=0.5. A thorough link between the crystal structure and XRD spectra, transmission electron microscope (TEM), and selected area electron diffraction (SAED) patterns have all been investigated in order to enhance the characterisation of the samples. At 1KHz, the composites exhibit highest electrical resistivity values of 5.9×106 Ωm and 2.6×106 Ωm. With the incorporation of spinel ferrites in garnet ferrite composite (x=y=0.25) the highest value of dielectric constant (885.2) and low value of dielectric loss (0.07) at 100 KHz has been obtained. Permeability values, derived from permittivity data, showed an increase in real permeability values of from 1.4×1012 to 9.2×1017 for x=y=0.5 to x=y=0.25 composite. Vibrating sample magnetometer (VSM) further confirm that the composite x=y=0.25 has highest magnetic saturation (148.8 emu/g), coercivity (502 Oe) and microwave operating frequency (33.6 GHz). The observed high dielectric constant, low loss values, switching field distribution and good magnetic properties suggest the potential suitability of these samples for various electronic devices like: high frequency devices, antennas, switching devices and magnetic recording devices.

Effects of (Cd1/3Sb2/3)4+ co-substitution on the crystal structure, chemical bond characteristics, and microwave dielectric properties of CeO2-ZrO2-MoO3 ceramics

In this paper, Ce2[Zr1−x(Cd1/3Sb2/3)x]3(MoO4)9 (CZ1−x(CS)xM, x = 0.01–0.1) were prepared via the conventional solid-state method. XRD and Rietveld refinement analyses confirmed the formation of a single-phase CZ1−x(CS)xM solid solution with a space group of R-3c(167). The sintering behavior of the samples were investigated using SEM and relative density, which showed that optimal densification for CZ0.98(CS)0.02M ceramics were achieved at 675 °C with an average grain size of 1.70 μm. The P-V-L theory revealed the significant influence of the Zr(Cd/Sb)-O bond on the dielectric properties of CZ1−x(CS)xM ceramics. Furthermore, far-IR reflectance spectra indicated that the measured dielectric loss value (1.04 × 10−4) is in line with the calculated value (1.60 × 10−4), suggesting a substantial impact of phonon oscillation absorption on the dielectric properties. Notably, CZ0.98(CS)0.02M ceramics demonstrated superior performance at 675 °C, with εr = 10.44, Q × f = 93,152 GHz (at 12.96 GHz), and τf = −17.73 ppm/°C.

Comprehensive study on dielectric properties and proton conductivity of graphene oxide (GO) embedded PVdF/PVP membrane electrolytes

This article investigates how the presence of polyvinylpyrrolidone (PVP) affects the dielectric properties and proton conductivity of phosphoric acid (PA) doped PVdF/PVP-based composite polymer electrolytes supported by graphene oxide (GO). In the study, insights into the structural, morphological, and thermal characteristics of the proposed composite electrolytes are obtained using characterization techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). Proton conductivity and dielectric measurements are carried out across a frequency and temperature range (20 Hz-1 MHz, 300–420 K). We conduct in-depth discussions on the dielectric properties, including AC conductivity (σac), dielectric permittivity (ε′), imaginary permittivity (ε″), and loss tangent (tanδ) of the polymer electrolytes. While GO enhances the thermomechanical properties, the highest proton conductivity values are observed for (PVdF70/PVP30)-GO and (PVdF50/PVP50)-GO electrolytes, reaching 4.4 × 10−5 and 6.1 × 10−4 S/cm respectively. The dielectric measurements revealed a significant increase in the dielectric constant (ε′) and dielectric loss (ε″) values for the composite membranes, especially at lower frequencies and higher temperatures. For instance, the (PVdF50/PVP50)-GO composite exhibited ε′ values of 8.8 × 106, 1.99 × 105, and 77.38 at frequencies of 20 Hz, 1 kHz, and 1 MHz, respectively, at 300 K, and 7.38 × 106, 2.76 × 104, and 430.5 at 420 K. The ε″ values at 300 K for the same composite were 16.18 × 106, 7.25 × 105, and 1.09 × 103, respectively, at the same frequencies. (PVdF50-PVP50)-GO exhibits the lowest relaxation time (τ) and the highest proton conductivity at ambient temperature. These findings underscore the intricate interplay between PVP content, dielectric properties, and proton conductivity, providing valuable insights for the advancement of polymer electrolyte materials. This study contributes to our understanding of PA-doped (PVdFx/PVPy)-GO electrolytes, with implications for electronic and energy storage devices.

The synthesis and characterization of alkaline niobate-based ceramic composites containing L-lysine Hydrochloride

Some lead-free piezoelectric ceramics are known to have high dielectric and piezoelectric properties but are limited by their brittle nature. A few amino acids have recently been reported to exhibit rather low dielectric and piezoelectric properties but have the advantage of being biocompatible and flexible. It would therefore be interesting to form a composite that will combine the inherent advantage of high dielectric properties from the ceramics and flexibility from the biomolecule. In this research, the properties of lead-free (K0.45Na0.51Li0.04)(Nb0.85Ta0.1Sb0.05)O3 (KNNLST) ceramics and L-lysine hydrochloride (L-LHCl) have been combined to produce dielectric composites. The samples were produced by mixing the constituents from 0 wt.% to 100 wt.%, pelletising and heat-treating them. Bulk density, X-ray diffraction, scanning electron microscopy, and dielectric characterisation were techniques used to determine the density, phases, morphology, and dielectric properties of the produced composites. The results show an increasing bulk density value from 1.2 g/cm3 for L-LHCl to 4.67 g/cm3 for the KNNLST ceramics. The morphology of the composite shows very tiny grains when small amounts of the ceramics were introduced. The L-LHCl transforms from an amorphous phase to a crystalline phase having the orthorhombic-tetragonal structure with the introduction of the KNNLST ceramics. The dielectric constant values increased with increasing KNNLST ceramics content from 10 @1 kHz to 200 for the composite with 80 wt%. KNNLST content. The dielectric loss values decreased for L-LHCl from 0.9 @1 kHz to 0.2 @1kHz. The electrical conductivity values increased with increasing KNNLST ceramics content. The results show that the composites produced from these constituents may be suitable for dielectric applications.

Examining the varied localization of oxygen groups on graphene nanosheets and their entangled influence on electromagnetic waves’ absorption within polymeric coatings

In this study, two distinct graphene nanosheets, featuring varying localization of oxygen groups, were synthesized to investigate their influence on the electromagnetic waves’ absorption properties of polymeric coatings. Natural graphite flakes and expanded graphite served as carbon precursors for synthesizing Edge-Functionalized Graphene Oxide (E-GO) and Basal-Functionalized Graphene Oxide (B-GO) nanosheets, respectively. Subsequently, polymer nanocomposite coatings were fabricated by dispersing E-GO and B-GO into a waterborne epoxy matrix. The dielectric properties of these coatings were measured post-in-situ thermal reduction at 225 °C. Results revealed that coatings containing B-GO nanosheets exhibited higher dielectric values compared to those with E-GO nanosheets. Furthermore, the electromagnetic properties of the coatings were examined to correlate the network formation findings obtained from dielectric studies and reflection loss values. It was demonstrated that an improved dispersion state of graphene nanosheets resulted in enhanced interphase formation between epoxy and graphene nanosheets, thereby improving interfacial polarization and dielectric permittivity values. Additionally, residual oxygen groups situated on the graphene basal plane induced dipolar polarization, consequently enhancing the reflection loss values of electromagnetic waves. Ultimately, the enhancements in electrical conductivity and dielectric permittivity contributed to reflection loss values reaching −52.67 dB in coatings with a thickness of 320 μm and a graphene loading level of 1.5 wt%, representing significant advancements compared to existing literature.

Composite Paints with High Content of Metallic Microparticles for Electromagnetic Shielding Purposes

This paper describes the technological process used to manufacture composite paints with a high content of metallic microparticles (Al and Fe) for automotive electromagnetic compatibility applications. The thickness of the deposited paint layer was larger for paints with a greater metal content, regardless of the plastic support used for paint deposition. The roughness of paint layers with a greater content of metal particles was about 30%–35% higher than that of layers with a lower metal particle content, regardless of the metal type. The surface roughness of paint layers containing Al was at least 2.5-times higher than that of paint layers containing Fe, an aspect that could be explained by the better formulation of the paint containing Fe. The dielectric loss and conductivity values crucially depend on the plastic substrate used, meaning that the dipolar polarization of the substrate enhances the effect of conductive paints. Based on the dielectric properties measured at 10 kHz, the optimal recipe for efficient electromagnetic compatibility was found to be 20 wt.% Fe powder, deposited on a sandblasted polycarbonate (PC) substrate. It is expected that formulations of paints with a high percentage of metallic particles will effectively compete with traditional plastic metallization technologies.

Dielectric study and electrochemical detection of ascorbic acid using modified electrode treated with europium-doped tricalcium aluminate nanoparticles

The current study involved the dielectric, and sensor properties of trivalent europium (Eu3+) doped tricalcium aluminate (Ca3Al2O6) Nanoparticles. These samples were synthesized through the solution combustion method with urea (NH2CO·NH2) as the fuel. Structural analysis confirms that the samples exhibited a sustainable cubic phase with the Pm-3m space group. The irregular spherical morphology and agglomeration of synthesized particles were observed using a scanning electron microscope. The energy bandgap values were calculated using the Kubelka and Munk relation, which ranged from 5.14 to 5.27 eV. To examine the dielectric behavior at different frequencies, electrical impedance spectroscopy was performed which provided insights into the changes in electrical permittivity and revealed the contributions of both grains and grain boundaries in the samples. The synthesized material exhibited higher values of dielectric constant and loss at lower frequencies, which decreased significantly as the frequency increased. This suggests that the samples are suitable for applications in microwave devices. Also, the electrochemical studies demonstrate the sensor's rapid amperometric response to ascorbic acid oxidation. The current constructed sensor has a sensitivity of 0.0065 A for ascorbic acid and the electrode treated with Ca3-xAl2O6:xEu3+ (x = 0.05) is better able to detect the electrochemical behavior of substances like ascorbic acid.

Analysis of Thermal and Dielectric Loss Features of Lunar Regolith Considering Real‐Time Effect Solar Irradiance

AbstractSolar irradiance received at the lunar surface is crucial for interpreting brightness temperatures detected by orbiters and for understanding the thermal, physical, and dielectric properties of the lunar regolith. We developed a real‐time effect solar irradiance (ESI) model that accounts for the influence of surface relief and terrain shading. This model was integrated with a standard thermal model to examine ESI fluctuations and their impacts on the diurnal physical temperature variations. To assess the effects of spatial resolution, we selected four locations with significant ESI disparities for simulation, then compared lunar surface temperatures at various spatial scales, ranging from 20 m to 25 km. Utilizing brightness temperature data obtained from the Chang'E‐2 (CE‐2) microwave radiometer (MRM), we integrated the shallow physical temperature profiles with the radiative transfer equation to simulate brightness temperatures and determine dielectric loss at different frequencies. In the Von Kármán crater, the received ESI exhibits a cyclical pattern of approximately 18 years and areas with rugged topography may exhibit larger ESI variations (∼7%). We found that the spatial resolution of ESI has a minimal effect on the physical and brightness temperatures at resolutions of 10 km or coarser. At the shallow layer, the average dielectric loss values are 0.0128–0.0170, 0.0083–0.0110, 0.0055–0.0073, and 0.0061–0.0081 for the CE‐2 frequencies of 3, 7.8, 19.35, and 37 GHz, respectively. The integration of real‐time ESI modeling, thermal dynamics, radiative transfer equations, and observational data enhances our comprehension of the physical temperature profile and thermal characteristics of shallow regolith.

Study of the effect of synthesis temperature and thermal aging on structural, dielectric properties and phase composition in NiO/NiAl2O4 composite ceramics

In modern materials science, a considerable amount of research is focused on obtaining new ceramic materials to create efficient functional elements. Acquiring highly efficient and stable ceramic catalysts for alternative energy is an important task that demands an urgent solution. Solving this problem as fast as possible is essential, as it will facilitate the development of new technologies that can prevent future energy crises. Nickel oxide (NiO) and spinel with the composition NiAl2O4 are excellent candidates as high temperature catalysts used in alternative energy applications. This paper studies the synthesis of NiO/NiAl2O4 composite ceramics and the effect of high-temperature aging on their phase composition, crystalline properties, and dielectric characteristics. The study found that the phase composition and microstructure of the ceramics remain unchanged after several thermal aging cycles at 700 °C. However, the crystalline parameters and low-frequency dielectric characteristics may fluctuate significantly depending on the duration of aging. The observed variations were predominantly influenced by the microstructural features of the composite ceramics. As the average grain size increased and the phase transformations were completed, the crystalline parameters and low-frequency dielectric characteristics reached a stable state without further alteration. For NiO/NiAl2O4 ceramics with a sintering temperature of 1500 °C, the highest shrinkage, low dielectric loss values and acceptable hardness were observed, indicating that the fabricated ceramics are suitable for mechanical processing. In general, the obtained composite ceramics show high temperature stability and are well-suited for use as functional elements in hydrogen energy applications.

Decoding high-frequency dielectric loss of Poly(ester imide)s: Molecular simulation and experiment validation

Polyimides (PIs) are essential materials for electronic and high-frequency communication applications, often face challenges with high dielectric loss. Drawing inspiration from low-dielectric-loss liquid crystal polyesters, ester groups have been introduced into PI backbones to develop poly (ester imide)s (PEsIs). This study delved into various PEsIs, aiming to reduce dielectric loss at high frequencies and to understand the molecular mechanisms behind this improvement. Selection and design of PEsIs were based on four key factors: the number of ester groups, substitution positions, side substituents and intermolecular interactions. The results indicated that the high-frequency dielectric loss of PEsIs, specifically at a frequency of 10 GHz, decreases with an increased number of ester groups. For isomeric PEsIs systems, introducing ester groups into the dianhydride part notably reduced the dielectric loss. The modes of bonding between the phenyl ring and the ester group in PI structures also impacted the dielectric loss. The configuration with an O-linked isomer showed a lower value of dielectric loss. On the other hand, introducing hydrogen bonding into PEsIs were observed to contribute a negative impact on the reduction of dielectric loss. Based on these theoretical findings, two PEsIs structures, which were identified as low-dielectric-loss PEsIs candidates, were successfully synthesized. Their dielectric loss factors at 10 GHz were measured experimentally as 0.00153 and 0.00134, thereby confirming the reliability of the theoretical results.

Dielectric behaviour, impedance and conductivity studies of YBaYbSiO oxy-apatite compounds

This paper reports the dielectric behaviour and electrical conduction properties of Y6-xBa4Ybx(SiO4)6O2 (YBaSiO: xYb) compounds. The Scanning Electron Microscopy (SEM) was utilized to obtain the surface microstructure of the compound. The micrographs showed both the circular and elongated shape of grains and their random distribution. The Fourier Transform Infrared Spectroscopy (FTIR) was used to confirm the presence of bond formations in the compounds. From the spectra, it was observed that the peaks at 690 cm−1 and a band from 850 cm−1 to 998 cm−1 are due to the stretching frequency of Y-O molecules and Si-O molecules, respectively. The peak centred at 1464 cm−1 is of vibration modes of Ba2+ions. These peaks confirmed the formation of oxy-apatite compounds. Both the dielectric permittivity and dielectric loss, decreases with increasing values of frequency due to reduction in the polarization effects on the higher side of frequency. This is because the dipole orientation lags with the rapidly reversing alternating current (ac) field. The value of dielectric loss was found to range between, 0 – 3.5 in frequency ∼ 100 Hz and 0 – 0.5 in frequency ∼ 100,000 Hz, up to temperature 500 °C. The impedance value decreases and hence a. c. conductivity increases, at higher frequencies. The increment in ac values followed the universal power law. The Nyquist plot showed that the area under the curves reduces and hence indicates negative temperature coefficient of resistance i.e., NTCR behaviour of compounds. The obtained results suggest the utilization of compound in electrical devices as power loss component, solid oxide fuel cells, and capacitors etc.

Crystal Structure and Spectroscopic Characterization of a New Hybrid Compound, (C12H17N2)2[CdBr4], for Energy Storage Applications.

Organic-inorganic hybrid materials have recently found a vast variety of applications in the fields of energy storage and microelectronics due to their outstanding electric and dielectric characteristics, including high dielectric constant, low conductivity, and low dielectric loss. However, despite the promising properties of these materials, there remains a need to explore novel compounds with improved performance for practical applications. In this research paper, the focus is on addressing this scientific challenge by synthesizing and characterizing the new-centrosymmetric (C12H17N2)2[CdBr4] crystal. This compound offers potential advancements in energy storage technologies and microelectronics due to its unique structural and electronic properties. The chemical mentioned above crystallizes in the monoclinic system, and its protonated amine (C12H17N2)+ and isolated anion [CdBr4]2- are bound by C-H···π and N-H···Br hydrogen bonds to form its zero-dimensional structure. Through optical absorption analysis, the semiconductor nature of the material is verified, showcasing a band gap of around 2.9 eV. Furthermore, an in-depth examination of Nyquist plots reveals the material's electrical characteristics' sensitivity to frequency and temperature variations. By applying Jonscher's power law to analyze ac conductivity plots, it is observed that the variation in the exponent "s" accurately characterizes the conduction mechanism, aligning with CBH models. The compound exhibits low dielectric loss values and a high permittivity value (ε ∼ 105), making it a promising candidate for energy storage applications. By managing the scientific challenge of improving material performance for energy storage and microelectronics, this research contributes to advancing the field and opens avenues for further exploration and application of organic-inorganic hybrid materials.