Dielectric Conductivity Research Articles

Dielectric, electrical and thermal properties of Sodium Molybdate-hexagonal Boron Nitride composites enabled by cold sintering

Advances in 5G and 6G communication technologies and their applications are in part limited by the capabilities of current electronic packaging materials, as expanded bandwidth is a pressing need for novel dielectric substrates capable of co-firing into packages and devices, characterized by low dielectric loss and enhanced thermal conductivity. This investigation provides further characterization in the dielectric, electrical and thermal conductivity properties over previously reported cold sintered composite of Sodium Molybdate Na2Mo2O7 (NMO) with hexagonal Boron Nitride (hBN), such as relative permittivity (εr) and dielectric loss (tan δ) values at high frequencies of 75–110 GHz, electrical resistivity (ρ) fitting to percolation theory, Weibull statistical analysis of electrical breakdown strength (Eb) and its anisotropic thermal conductivity (κ) influenced by the filler's crystal structure. The cold sintered composites were systematically characterized with respect to filler volume fraction, temperature, and frequency. The findings in this analysis position engineered composites as a promising alternative for microwave substrate materials, with using a densification method that limits interactions and maximizes densification, hence the demonstration with cold sintering.

Effect of calcination temperature on structural, morphological elastic and electrical properties of MgO nanoparticles synthesized by combustion method

This study explores the influence of calcination temperature on the properties of MgO nanoparticles (MgO NPs) synthesized via the solution combustion method. Through X-ray diffraction (XRD) and scanning electron microscopy (SEM), structural and morphological changes were investigated. Elastic and dielectric properties were analyzed using computational tools and impedance spectroscopy. Results show that the prepared nanomaterial is belongs to a cubic system and a space group of F m −3 m. Increasing in the calcination temperature (550 °C and 750 °C) enhances crystallinity, reduces defects, and improves structural uniformity. Elastic properties exhibit notable improvements, with Young's modulus increasing from 356.43 GPa for pristine MgO to 364.6 GPa for MgO calcined at 750 °C. Dielectric studies were conducted in the frequency range from 50 to 5 MHz at room temperature. Dielectric analysis reveals enhanced properties, including increased dielectric constant and AC conductivity with rising temperature. The study emphasizes the pivotal role of calcination temperature in tailoring MgO NPs for diverse applications.

Tailoring the Optical Properties of Polyvinyl Alcohol/Carboxymethyl Cellulose/Polyvinyl Pyrrolidone Blend Films Using Laser Irradiation for Their Application in Optoelectronic Devices

In our research described in this article we used a solution casting technique to prepare a blend film containing polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC) and polyvinyl pyrrolidone (PVP). Samples from the prepared PVA/CMC/PVP film were irradiated with infrared energy fluences ranging from 5 to 55 Joule/cm2 using an infrared pulsed laser. We used UV-vis spectroscopy and the International Commission on Illumination (CIE) color changes technique to investigate the resulting effects of the laser irradiation on the optical bandgap energy and color properties of the prepared films. As the laser fluence increased up to 55 Joule/cm2, the maximum fluence used, both the direct and indirect bandgaps decreased. We attribute this to the dominance of chain crosslinks that destroyed the ordered structure and thus increased the amorphous regions. The effect of laser irradiation on the absorbance, refractive index, real and imaginary dielectric parameters and optical conductivity of the blend samples were studied. Furthermore, the optical color changes between the pristine and the irradiated films were evaluated. The pristine blend film was uncolored. It showed significant color changes when irradiated with the laser at increasing fluences up to 55 Joule/cm2. The improvement in the optical properties of PVA/CMC/PVP blend film suggested its usage as a promising candidate for future optoelectronics manufacturing.

Investigation of Morphology, Optical and Electronic Ac Conduction of the Olivine Manganite Compound: NaMnPO4

AbstractThe evolution of multifunctional materials is an outstanding research area, which aims to improve the versatility of materials according to their broad domains of usage. Focus interest was paid here to the orthophosphate compound, in particular, the olivine NaMnPO4 material. This compound was synthesized by a solid‐state method and investigated using numerous techniques. Primary room‐temperature structural analysis evidences the sample synthesized in the orthorhombic structure and its phase purity. The sample‘s average grain size was calculated to be around 420 nm. Further, the band gap for our material was found to be (Eg=4.4 eV) by optical analysis of UV‐visible spectroscopy, revealing that our compound is a potential candidate for optoelectronic applications. The electrical behavior study‘s main results confirm the ferroelectric character of the sample and support the aim of deepening the knowledge of the material according to its thermally stimulated conduction processes through impedance spectroscopy. Electrical studies revealed the dominant transport processes across various temperature and frequency ranges, leading to the NSPT model. The frequency dependency relates to frequency‐dispersive dielectric spectra, conduction mechanisms, and relaxation phenomena. The obtained results show perspective and suggest that the material under study has a wide range of potential electronic applications.

First principles study on the structural, electronic, mechanical and optical properties of Pb-free double perovskites M2FeMnO6 (M = Rb, Cs)

The researchers are looking for efficient smart materials to cope with the energy crisis. In this regard, double perovskites are extensively studied for various technological advantages. In the present work, we investigated the structural, electronic, optical, and elastic properties of double perovskites M2FeMnO6 (M = Rb, Cs) using the WIEN2k package within density functional theory (DFT). The structural properties reveal that both compounds are stable and can be fabricated experimentally. The electronic study indicates that both compounds possess a metallic nature in spin up configuration while in the spin down configuration these materials are insulators overall they possess half metallic nature. The elastic parameters indicates that these compounds are mechanical stable. Furthermore, the ductile and anisotropic nature is conformed from the computed elastic constant obtained through IR-Elast package. Optical parameters such as dielectric constants, optical absorption, optical conductivity, and optical reflectivity are studied in the range of 0 to 40 eV energy range. From the study of these compounds, we recognize that these materials can be potential applicants for spintronic and optoelectronic devices.

Synergistic Enhancement of Electromagnetic Wave Absorption and Corrosion Resistance Properties of High Entropy Alloy Through Lattice Distortion Engineering

AbstractHigh entropy alloys (HEAs) are promising electromagnetic wave absorption (EMA) materials due to its designable crystal structure, variable electromagnetic properties, and excellent corrosion resistance. However, the impedance mismatch owing to the high electric and dielectric conductivity severely hinders the application of HEAs in the field of EMA. Herein, the lattice distortion of FeCoNiCu HEA is manipulated accurately by doping and annealing strategies to tailor the EMA properties. Significant lattice distortion is observed in the FeCoNiCuC0.37, which leads to a decrease in the electrical conductivity and the creation of abundant dipoles. Owing to the optimal impedance matching and boosted polarization loss, the FeCoNiCuC0.37 delivers a minimal reflection loss of −65.4 dB accompanied by an effective absorption bandwidth (EAB) of 6.81 GHz. After annealing at 200 °C, the EAB of the FeCoNiCuC0.37 is further increased to 7.99 GHz at 1.95 mm, which is better than that of most HEA‐based EMA absorbers reported so far. Moreover, it demonstrates excellent corrosion resistance owing to the more tortuous diffusion path of corrosive medium origin from lattice distortion. Thus, the study provides a new insight into designing high performance HEA‐based EMA materials with superior anti‐corrosion property by lattice distortion engineering.

Synthesis of multiple layers of alternating ZnO and TiO2 using atomic layer deposition and their optical characterization

We report the optical characterization of bi-layer and quadri-layers of TiO2/ZnO transparent oxide films having a net thickness of 100 nm. The atomic layer deposition (ALD) was used to grow these multiple-layered films. We examined their optical properties to understand the impact of the number of layers. The grazing incidence X-ray diffraction (GIXRD) was used to assess the microstructure of the films, which showed that the ZnO layers were polycrystalline, while the TiO2 layers were (X-ray) amorphous. The optical transmission and reflection spectra of the investigated films were recorded in the range of 150–2500 nm at room temperature. The refractive index (n), extinction coefficient (k), real and imaginary parts of the dielectric constant, optical conductivity, and loss factor agree well with those of other amorphous oxides. It was established that the indirect allowed optical transitions are favorable and the optical gap (Eg) increases from 3.03 eV to 3.14 eV as the number of layers increases. The contribution of polarizability (ξ) and electrical susceptibility (χe) to the dielectric constant was also discussed. The relation between the relative density (D) and the porosity (Pro) with the crystalline quality, layer thickness, and the number of layers was also estimated. The results obtained from the study of TiO2/ZnO multilayer films indicate that multilayer thin films improve the quality of film crystallinity and optical properties with the increase of the layers numbers, and could guide the development of potential applications.

Investigation of structural, electrical, magnetic, and optical properties of Cu (111) and the impact of Ag adatoms adsorption: A density functional theory study

Our study conducts a comprehensive investigation on the structural, electrical, magnetic and optical properties of pure Cu with a (111) crystallographic orientation, as well as the impact of the adsorption of Ag adatoms on a Cu (111) surface. To perform this analysis, we utilized the full potential linearized augmented plane-wave (FP-LAPW) approach in conjunction with Generalized Gradient Approximations (GGA + U) and the Wien2k simulation software. Specifically, we calculated electrical and optical properties including the band structure, density of states (DOS) for the Cu (111) surface with and without the presence of adsorbed Ag atoms. Based on the observed results, the overlapping of the electronic bands for simple Cu (111) is comparatively less than that of adsorbed Ag/Cu (111) slab, indicating higher conductivity. Moreover, the evolutions are also observed which are mainly due to d orbitals of Cu and Ag for Cu (111) and Cu/Ag (111) respectively. The calculated magnetic optimization and weak diamagnetic magnetic moments shows weak diamagnetism in these materials. The optical properties like Dielectric Function(ε), Refractive index(n), Extinction co-efficient(k), Reflectivity(R), Energy Loss (L), Absorption (α) and Optical conduction (σ) are calculated. Our research examines the importance of band structure calculation in relation to optical properties. We discuss how plasmon-energy plays a crucial role in producing peaks in the energy loss function, with a crystallographic axis of 13.7 eV and 13.6 eV for both Cu (111) and Ag/Cu (111) slab. In addition, we calculated the static dielectric function, absorption coefficient, and refraction values for these materials. Reflectivity spectra for both Cu (111) and Ag/Cu (111) exhibits Infra-red region, indicating good coating materials to reduce heating, for the application of electrical appliances and for optical application like anti-reflecting coating, optical fibers and solar cells.

Physico-electrical properties of starch-based bioplastic enhanced with acid-treated cellulose and graphene oxide fillers

Biopolymer composites represent an emerging alternative to petroleum-derived polymers for applications in electronic devices. Cellulose from Luffa cylindrical was treated with acid, and graphene oxide was produced from waste battery rod graphite. The two products were characterized using FTIR, SEM, TGA and XRD. After that, starch-based bioplastic films with varying amounts of acid-treated cellulose (ALC-cellulose) and graphene oxide (GO) as fillers were prepared, and the physical and electrical properties were determined. XRD data revealed a crystallinity of 62% for the ALC-cellulose and 52% for the cellulose precursor. GO had a d-spacing of 0.76 nm compared to 0.29 nm for battery-sourced graphite. TEM micrograph analyses revealed an average fibre diameter of 44.7 nm for acid-treated cellulose and 99.7 nm for cellulose. The density, thickness, opacity, and tensile strength of the bioplastic films increased from 1.31 to 1.44 g/cm3, 0.21–0.48 mm, 14.78–38.64, and 0.98–1.42 MPa, respectively, while the moisture content, swelling ability, and porosity reduced, with an increase in percentage composition of the filler materials. The dielectric constant and conductivity increased from 50.3 to 6965.2 and 0.0036–0.0147 S/m with an increase in percentage composition of the filler materials except for Filmcr4, which showed a drop in dielectric constant (3033.73) and conductivity (0.0074 S/m). Overall, this study has demonstrated that bioplastic filler materials can be sourced from waste materials and that these fillers improved the starch-based bioplastic film's physical and electrical properties.

Temperature dependent dielectric relaxation and current conduction mechanism in Ba and Ti co-doped bismuth ferrite ceramic

Temperature dependent dielectric relaxation and current conduction mechanism in Ba and Ti co-doped bismuth ferrite ceramic

Low-temperature synthesis and properties of high-purity boron nitride microspheres

Boron nitride (BN) has excellent high temperature resistance, thermal conductivity, strong insulation, and wave-transparent properties. Spherical BN is an essential filler in polymer matrix composites due to good particle mobility and high filler content. In this paper, we present a large-scale preparation for BN microspheres with uniform particle size distribution in the range of 1.0–2.8 μm via solvothermal method at low cost and high yield (∼90%), which is two orders of magnitude lower than the diameter of the spherical BN prepared by other methods. BN microspheres can achieve good crystallinity (>70%) and high purity (>99.9%) at 800 °C. The temperature resistance study showed that the BN microspheres could maintain the dense particle morphology at 1200 °C. In addition, the prepared BN microspheres have good dielectric and thermal conductivity properties (dielectric constant ∼3.4, dielectric loss ∼2.0 × 10−3, and thermal conductivity of 9.8 W m−1 K−1), which show great potential in the field of wave-transparent and thermal conductive composites. The synthesis process of BN microspheres proposed in this study provides a new idea for the preparation of ceramic micro or nano materials by polymer-derived ceramics.

Comparative first principles investigation on the structural, optoelectronic and vibrational properties of strain-engineered graphene-like AlC3, BC3 and C3N monolayers

Three cardinal two-dimensional semiconductors viz., AlC3, BC3 and C3N, closely resembling the graphene structure, are intriguing contenders for emerging optoelectronic and thermomechanical applications. Starting from a critical stability analysis, this density functional theory study delves into a quantitative assessment of structural, mechanical, electronic, optical, vibrational and thermodynamical properties of these monolayers as a function of biaxial strain (ε) in a sublinear regime (−2%⩽ε⩽4%) of elastic deformation. The structures with cohesive energies slightly smaller than graphene, manifest exceptional mechanical stiffness, flexibility and breaking stress. The mechanical parameters have been deployed to further cultivate acoustic attributes and thermal conductivity. The hexagonal structures with mixed ionic-covalent molecular bonds have indirect electronic band-gap and work-function acutely sensitive to ε . Dispersions of optical dielectric function, energy loss, refractive index, extinction coefficient, reflectivity, absorption coefficient and conductivity are deciphered in the UV–Vis–NIR regime against strain, where particular frequency bands featuring high polarization, dissipation, absorbance or reflectance are identified. Phonon band-structure and density of states testify dynamic stability in the ground state for all systems except the compressed ones. A comprehensive group theoretical analysis is performed to cultivate rotational; infrared and Raman-active modes, and the nature of molecular vibrations is delineated. The red-shifting of phonon bands and E2g/A1g Raman peaks with increasing ε , associates estimation of Grüneisen parameter. Finally, strain-induced alterations of thermodynamic quantities such as entropy, enthalpy, free energy, heat capacity and Debye temperature are studied, followed by a molecular dynamics-based stability assessment under canonical ensemble.

Investigation of microstructure evolution and electromagnetic shielding mechanism of absorbed MWCNTs-FeCo composites by one-step in situ deposition using high-speed laser cladding

Electromagnetic shielding materials can inhibit or reduce the harm of electromagnetic radiation and have become an important means to protect against electromagnetic pollution. In order to overcome the inconveniences of in situ or conformal manufacturing on the specific equipment, and the resulting assembly errors lead to the reduction of electromagnetic interference shielding effectiveness (EMI SE). As a new technology, high-speed laser cladding can directly design multi-walled carbon nanotubes (MWCNTs)-FeCo alloy composites as absorbents, and it is the first time to realize the rapid manufacturing of electromagnetic shielding materials by one-step in-situ deposition without adding auxiliary materials. According to the temperature field and stress field, it is found that the through-crack defects of electromagnetic shielding coating mainly resulted from the residual stress concentration of microcracks near the bottom fusion line. When the cladding strategy is 1600 W power deposition after preheating at 400 °C, a high-quality cladding layer can be obtained. When the addition of MWCNTs is 1.5 wt%, the material exhibits good electromagnetic shielding performance under the synergistic effect of dielectric loss, conductivity loss, and magnetic loss. And the average EMI SE is 23 dB in the range of 2-18GH. The research shows that high-speed laser cladding can simultaneously meet the requirements of flexible material design and efficient preparation, which realizes the integration of electromagnetic shielding material design and manufacturing.

Boron nitride microribbons strengthened and toughened alumina composite ceramics with excellent mechanical, dielectric, and thermal conductivity properties

Boron nitride microribbons strengthened and toughened alumina composite ceramics with excellent mechanical, dielectric, and thermal conductivity properties

Synthesis, Characterization, Dielectric, and Electrical Conductivity Studies of Zinc Oxide Nanoparticles

A co-precipitation technique is used to synthesize of ZnO nanoparticles. The synthesized ZnO nanoparticles were characterized by UV-visible spectroscopy, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), photoluminescence, Fourier-Transform Infrared Spectroscopy (FTIR), and X-ray diffraction (XRD). The size of the nanoparticles was wide-ranging from 1 nm to 100 nm, corresponding to the HR-TEM analysis. The photoluminescence study of ZnO nanoparticle shows emission in the UV region. The particle dimension of ZnO nanoparticle has also been studied through XRD. Dielectric spectroscopy of synthesized ZnO NPs pellet has been studied at a wide frequency range 10−1 to 105 Hz. The capacitance and dielectric permittivity of ZnO nanoparticles drop continuously with frequency as dipoles have less time to align in the field. Dielectric permittivity of ZnO pellets increase up to 5 mm thickness and subsequently drop, perhaps due to raise in resistivity. The dielectric loss of ZnO pellet has been examined as a function of frequency. The electrical conductivity of ZnO nanoparticles rise exponentially with frequency. Based on the dielectric studies, the dielectric permittivity and electrical conductivity of ZnO are highly depending on thickness and frequency range. The percolation threshold of ZnO pellets has been found between 4-5 mm thicknesses.

Structural and temperature dependent dielectric behaviour of BxFe(3−x)O4 nanoferrite particles

AbstractThe auto‐combustion technique was employed to synthesize nano particles of BxFe(3−x)O4 (x = 0.0, 0.7, 1.18, 1.36 and 1.54). The resulting structural and dielectric properties of the boron doped Fe3O4 were evaluated. XRD analysis confirmed the presence of a single spinel structure with crystallite dimensions ranging from 21.18 to 26.43 nm and lattice parameters of 8.211 to 8.487 Ǻ. The morphological images revealed homogenous and spherical grain sizes, while EDX confirmed the presence of constituent elements used. The X‐ray density increased whereas the bulk density and the porosity decreased with boron substitution. The study of dielectric properties and AC conductivity (σAC) was demonstrated and the AC conductivity decreased with increasing boron concentration, indicating a hopping mechanism. Moreover, noticeable variations in dielectric loss, AC conductivity, and dielectric permittivity with temperature and frequency were observed. These observations were attributed to the Maxwell–Wagner interfacial polarization and the hopping of charges between Fe3+ and Fe2+ ions.

Characteristics of Surface Charge Accumulation on Spacers and Its Influencing Factors

Charge accumulation usually happens on the surface of spacers under DC operation, which is susceptible to inducing surface flashover. In order to explore the surface charge accumulation mechanisms and the influences of dielectric conductivity, gas ion mobility, and temperature field on the surface charges, a time-varying charge density model at the gas–solid interface of spacers was established. The results of the simulation show that the discontinuity of the current density between the spacer bulk side and the gas ion flow is the fundamental reason for the charge accumulation on the spacer surface. Additionally, the value of current density fluxes at the interface continues to decrease with the change of the electric field, and the progress of charge transfer gradually stabilizes. Moreover, the dielectric conductivity directly affects the charge accumulation process, and there is a critical conductivity in which the effect of charge conduction in dielectrics counteracts that of gas-phase charge deposition, theoretically. When the conductivity is higher than the critical conductivity, the solid-side charge conduction is the main source of the surface charge accumulation, while the gas-phase charge deposition on the gas side plays a dominant role when the conductivity is lower than the critical conductivity. The charge accumulation is not significantly affected by gas ion mobility when the temperature is evenly distributed. However, under the temperature field with gradient distribution, the current density fluxes at the interface change, causing the polarity reverse of the accumulated charge. In the high-temperature region, the volume current density surges simultaneously with the conductivity, leading to a higher density of surface charge accumulation. Lastly, the design of spacers needs to keep the current densities on both sides of the interface as similar as possible in order to avoid excessive charge gathering in localized areas.

Temperature-Dependent electrical and dielectric characteristics of lead germanate Pb5Ge1.5Sn1.5O11

A solid-state reaction was used to synthesize the tin modified lead germanate: Pb5Ge1.5Sn1.5O11 (PGSO). The composition was modified to enhance its dielectric and electrical properties. The PGSO sample was characterized by various analytical techniques, such as XRD for structural analysis and FTIR for additional structural information. The surface morphology and features of PGSO were examined by SEM, while its band gap was determined by UV–Visible-Diffuse Reflectance Spectroscopy absorbance spectra. The impedance, dielectric behaviour, AC conductivity, activation energy, and modulus of PGSO were also studied. The temperature dependence of the dielectric constant and AC conductivity showed an increase with increasing temperature. The electrical resistivity (R) decreased as the temperature increased from 100 °C to 300 °C, exhibiting a NTCR behaviour for PGSO sample, which could be applied as a high temperature thermistor and sensor, and could be used to fabricate a high sensitivity, low-cost thermistor. The circuit parameters such as bulk resistance (Rb), frequency factor (n), and bulk capacitance (Cb) were determined by fitting the Nyquist plot using an equivalent circuit (CQR)(CR).

Playing with Low Amounts of Expanded Graphite for Melt-Processed Polyamide and Copolyester Nanocomposites to Achieve Control of Mechanical, Tribological, Thermal and Dielectric Properties.

Polyamide 11 (PA11) and copolyester (TPC-E) were compounded through melt extrusion with low levels (below 10%) of expanded graphite (EG), aiming at the manufacturing of a thermally and electrically conductive composite resistant to friction and with acceptable mechanical properties. Thermal characterisation showed that the EG presence had no influence on the onset degradation temperature or melting temperature. While the specific density of the produced composite materials increased linearly with increasing levels of EG, the tensile modulus and flexural modulus showed a significant increase already at the introduction of 1 wt% EG. However, the elongation at break decreased significantly for higher loadings, which is typical for composite materials. We observed the increase in the dielectric and thermal conductivity, and the dissipated power displayed a much larger increase where high frequencies (e.g., 10 GHz) were taken into account. The tribological results showed significant changes at 4 wt% for the PA11 composite and 6 wt% for the TPC-E composite. Morphological analysis of the wear surfaces indicated that the main wear mechanism changed from abrasive wear to adhesive wear, which contributes to the enhanced wear resistance of the developed materials. Overall, we manufactured new composite materials with enhanced dielectric properties and superior wear resistance while maintaining good processability, specifically upon using 4-6 wt% of EG.

Effect of crystal-water on the optical and dielectric characteristics of calcium sulfate in the THz band

The effect of crystal-water contents on the optical properties and dielectric characteristics of calcium sulfate in the THz band is investigated. The complex dielectric constant and conductivity are analyzed using the Drude-Smith model. The refractive index and absorption coefficient are linearly increased with the content of crystal-water, and the corresponding linear fitting lines of R2 over 0.97 are obtained. The dielectric properties of calcium sulfate are significantly affected by the crystal-water content. These results indicate that a new method to quantitative measurement of the crystal-water content in hydrous minerals is provided.