Change In Dielectric Constant Research Articles

First-principles study on lanthanide dopants in BaTiO3

Using first-principles calculation based on density-functional theory and density-functional perturbation theory, the microscopic structure and dielectric properties of Lanthanide (Ln) doped BaTiO3 are investigated. The doped Ln atoms exhibit significant displacement from Ba sites for charge compensation, forming off-centered configurations. This displacement is more pronounced for elements with smaller ionic radii. The change in ionic dielectric constant is strongly correlated with Ln displacement and Ln ion radius. As Ln displacement (ionic radius) increases (decreases), Ln-doped BaTiO3 has a higher ionic dielectric constant. However, regardless of the Ln species, the added Ln reduces the ionic dielectric constant compared to pristine BaTiO3.

Polyimide aerogel-based capacitive pressure sensor with enhanced sensitivity and temperature resistance

The development of intelligent electronic power systems necessitates advanced flexible pressure sensors. Despite improved compressibility through surface micro-structures or bulk pores, conventional capacitive pressure sensors face limitations due to their low dielectric constant and poor temperature tolerance of most elastomers. Herein, we constructed oriented polyimide-based aerogels with mechanical robustness and notable changes in dielectric constant under compression. The enhancement is attributed to the doping of surface-modified dielectric nanoparticles and graphene oxide sheets, which interact with polymer molecular chains. The resulting aerogels, with their excellent temperature resistance, were used to assemble high-performance capacitive pressure sensors. The sensor exhibits a maximum sensitivity of 1.41 kPa−1 over a wide working range of 0-200 kPa. Meanwhile, the sensor can operate in environments up to 150°C during 2000 compression/release cycles. Furthermore, the aerogel-based sensor demonstrates proximity sensing capabilities, showing great potential for applications in non-contact sensing and extreme environment detection.

Dielectric properties of water: a molecular dynamics study on the effects of molecule count and cutoff radius.

Currently, the study of systems confined within various materials, such as graphene and graphene oxide, for diverse applications such as water desalination, metal separation from water, battery cells, and high-efficiency capacitors, is very common. Among these systems, water is a prominent subject of investigation. Understanding the impact of the number of molecules and the optimal cutoff radius is essential in order to determine the parameters. This study investigates the dielectric properties of H O in relation to both the number of molecules and the cutoff radius within the simulation cell. We employ the flexible FBA/ water model, known for its improved accuracy in reproducing water's properties across various thermodynamic states. We range from 60 to 1372 molecules and use cutoff radius from 6 to 1.2 nm, encompassing a wide range of calculations to assess their impact on the simulation results, including critical properties like the dielectric constant, density, and phase change enthalpy. Computational theoretical calculations were performed by solving the equations of motion through molecular dynamics (MD) simulations in the liquid phase. These simulations were conducted using the isothermal-isobaric (NPT) ensemble. The primary software used to solve these equations is GROMACS, and own programs for creating the initial cell and performing the analysis.

Fabrication of a Capacitive 3D Spacer Fabric Pressure Sensor with a Dielectric Constant Change for High Sensitivity.

Smart wearable sensors are increasingly integrated into everyday life, interfacing with the human body to enable real-time monitoring of biological signals. This study focuses on creating high-sensitivity capacitive-type sensors by impregnating polyester-based 3D spacer fabric with a Carbon Nanotube (CNT) dispersion. The unique properties of conductive particles lead to nonlinear variations in the dielectric constant when pressure is applied, consequently affecting the gauge factor. The results reveal that while the fabric without CNT particles had a gauge factor of 1.967, the inclusion of 0.04 wt% CNT increased it significantly to 5.210. As sensor sensitivity requirements vary according to the application, identifying the necessary CNT wt% is crucial. Artificial intelligence, particularly the Multilayer Perception (MLP) model, enables nonlinear regression analysis for this purpose. The MLP model created and validated in this research showed a high correlation coefficient of 0.99564 between the model predictions and actual target values, indicating its effectiveness and reliability.

Diffusion behavior of rhodamine 6G in single octadecylsilyl-functionalized silica particle revealed by fluorescence correlation spectroscopy.

We investigated the diffusion behavior of rhodamine 6G (Rh6G) within single octadecylsilyl-functionalized (ODS) silica particle in an acetonitrile (ACN)/water system using fluorescence correlation spectroscopy (FCS). FCS measurements were conducted at the center of the particle to exclusively determine the intraparticle diffusion coefficient (D). The obtained D values were analyzed based on a pore and surface diffusion model, the results of which indicate that surface diffusion primarily governs the intraparticle diffusion of Rh6G. Furthermore, an increase in the concentration of ACN (CACN) resulted in a corresponding increase in the surface diffusion coefficient (Ds), whereas the addition of NaCl did not significantly affect the Ds values. We attributed this dependence of Ds to the dielectric constant change in the interfacial liquid phase formed on the ODS layer. Specially, Ds values of (4.0 ± 0.5) × 10-7, (7.7 ± 1.1) × 10-7, (1.0 ± 0.3) × 10-6, and (1.1 ± 0.2) × 10-6cm2s-1 were obtained for CACN = 20, 30, 40, and 50vol%, respectively. We anticipate that this approach will contribute to advancing research on intraparticle mass transfer mechanisms.

Properties degradation of 3D printed insulators in maritime and indoor environments

AbstractWith the advances in additive manufacturing, there is the idea of using 3D printers to produce spare parts in isolated systems such as ships, oceangoing vessels, warships, spacecraft, isolated stations, and so on. However, it raises the question of the reliability of such spare parts. One area that has not been explored much is the aging of electrical and dielectric properties, which could reveal weaknesses of 3D‐printed spare parts for use in electrical and automation systems. Therefore, the paper aims to investigate the change in resistance and dielectric constant. The results show that these changes could increase the probability of discharge and have serious consequences for electrical and automation systems.

Dielectric anisotropy changes in MBBA liquid crystal doped with barium titanate by a new method

In response to the burgeoning interest in enhancing the properties of liquid crystal composites, this research systematically explores the intricate interplay between MBBA nematic liquid crystals and ferroelectric barium titanate nanoparticles. The focus is modulating dielectric properties under temperature, frequency, and an applied electric field. Nuanced insights into temperature-dependent behavior, parallel and perpendicular component alterations, and a nonlinear correlation between nanoparticle concentration and dielectric constant are revealed. The study delves into dielectric anisotropy, indicating a reduction with increasing temperature. Structural analyses validate size reduction and crystal phase maintenance of barium titanate nanoparticles (NPs), emphasizing their impact on dielectric characteristics. Frequency-dependent investigations underscore a consistent decline in permittivity with rising frequency across nanoparticle concentrations. Application of an electric field in filling process of liquid crystal cells reveals irregular changes in dielectric constant, holding promise for tailored applications in display technologies. These comprehensive findings offer valuable insights into manipulating dielectric anisotropy properties of MBBA liquid crystal by a simple method for potential advancements in optoelectronic devices and display technologies.

Supercriticality, Glassy Dynamics, and the New Insight into Melting/Freezing Discontinuous Transition in Linseed Oil

The long-range supercritical changes of dielectric constant, resembling ones observed in the isotropic liquid phase of liquid crystalline compounds, are evidenced for linseed oil—although in the given case, the phenomenon is associated with the liquid–solid melting/freezing discontinuous phase transitions. This ‘supercriticality’ can be an additional factor supporting the unique pro-health properties of linseed oil. Broadband dielectric spectroscopy studies also revealed the ‘glassy’ changes of relaxation times, well portrayed by the ‘activated and critical’ equation recently introduced. In the solid phase, the premelting effect characteristic for the canonic melting/freezing discontinuous transition, i.e., without any pretransitional effect in the liquid phase, has been detected. It is interpreted within the grain model, and its parameterization is possible using the Lipovsky model and the ‘reversed’ Mossotti catastrophe concept. For the premelting effect in the solid state, the singular ‘critical’ temperature correlates with the bulk discontinuous melting and freezing temperatures. Consequently, the report shows that linseed oil, despite its ‘natural and complex’ origins, can be considered a unique model system for two fundamental problems: (i) pretransitional (supercritical) effects in the liquid state associated with a weakly discontinuous phase transition, and (ii) the premelting behavior in the solid side of the discontinuous melting/freezing discontinuous transition.

Exploring dielectric and AC conduction characteristics in elemental selenium glass modified with silver halides.

In this research work, we have examined the influence of silver halide doping on the dielectric dispersion and AC conduction of elemental selenium. The in-depth investigation shows that when the dopant silver halides are incorporated, there are noticeable changes in the parent selenium's dielectric constant (ε'), dielectric loss (ε''), and AC conductivity (σ ac). When we frame the discussion of the obtained results with the relevant transport models, we found that in pure selenium and Se95(AgI)5, conduction is primarily due to polaron hopping and follows the correlated barrier hopping (CBH) model. In contrast, Se95(AgBr)5 predominantly exhibits non-overlapping small polaron tunneling (NSPT). Interestingly, Se95(AgCl)5 demonstrates both NSPT and CBH conduction mechanisms, depending on the temperature range: NSPT is dominant between 303 K and 313 K, while CBH prevails from 318 K to 338 K. Additionally, our findings revealed the presence of both the Meyer-Neldel rule (MNR) and its reverse in the prepared silver halide chalcogenide alloys. The best optimization of dielectric constant and loss is observed for silver iodide as compared to silver chloride and silver bromide. Comparison with other silver-containing chalcogenide glasses indicates the better dielectric performance of the present silver halides containing selenium.

Optical Approach for Mapping the Intercalation Capacity of Porous Electrodes.

The intercalation capacity of a porous electrode in real batteries is not uniform spatially due to the inevitable structural and compositional inhomogeneity and site-dependent ion and electron transport features. Reliable methods to quantify the capacity distribution are highly desirable but absent so far in battery research. In this paper, a novel optical technique, oblique incident reflection difference (OIRD), was employed to monitor in situ the electrochemical ion (de)intercalation behavior of Prussian blue analogue (PBA) porous films. The OIRD signal responded synchronously to the ion (de)intercalation, and the change in the OIRD signal (ΔI) was positively correlated with the local electrochemical capacity, thereby enabling mapping of the spatially resolved ion storage capacity of the films. Optical analysis further showed that the OIRD response originated from the ion (de)intercalation-induced dielectric constant change of PBA films. This work therefore offers an intriguing in situ and spatially resolved tool for the study of rechargeable batteries.

High DC-Bias Stability and Reliability in BaTiO3-Based Multilayer Ceramic Capacitors: The Role of the Core-Shell Structure and the Electrode.

With the miniaturization of multilayer ceramic capacitors (MLCCs) and the increase of the electric field on a single dielectric layer, dielectric constant DC-bias stability and reliability have gradually aroused attention in the advanced electronics industry. In this study, MLCCs with outstanding DC-bias stability and reliability were prepared by using dielectric ceramic optimization and electrode optimization strategies. The effect of the Dy-Y doping concentration on the microstructure, dielectric properties, and reliability of BaTiO3-based ceramics was investigated. The shell ratio and effective shell doping concentration of the core-shell structure in ceramic grains play important roles in defects and electrical performances. The ceramic with appropriate doping contents shows a dielectric constant of 1800 and a dielectric constant change rate of -17% under a DC field of 4 kV/mm, which was fabricated into prototype MLCCs with different Ni electrodes. MLCCs exhibit outstanding DC-bias stability with a -28% degradation in the dielectric constant under a DC field of 4 kV/mm while possessing a dielectric constant of 2300 and satisfying the EIA X7S specification. Additionally, it was discovered that MLCCs prepared by using fine-size Ni particle electrodes have low electrode roughness and high interfacial Schottky barriers, resulting in better reliability. This study provides promising candidate materials and theoretical references for high-end and high DC-bias stability MLCCs.

Investigation of dysprosium oxide substitution on physical, electrical and dielectric properties in sodium borosilicate glass system

Dysprosium oxide doped sodium borosilicate glasses were prepared in this study using a usual melt-quenching process. Further XRD, FTIR, density measurements, electrical conductivity, and dielectric properties were utilized to explore the prepared glassy samples. We found that all produced samples exhibit amorphous nature through X-ray diffraction. Increase in density and molar volume were found when dysprosium oxide concentration increased, which was ascribed to dysprosium oxide's greater molecular weight. Density data was used to calculate and explain several physical characteristics, including rare earth ion concentration (N), polaron radius (rp), internuclear distance (ri), and field strength (F).

A numerical study supplemented with theoretical analysis on streaming potential in a soft nanochannel influenced by ion partitioning and mobile surface charge-dependent wall slip

We consider the pressure-driven flow of an electrolyte in a soft channel with a hydrophobic charged surface coated with a diffuse polyelectrolyte layer (PEL) with constant volumetric charge density. The objectives are to enhance the streaming potential and electrochemical energy conversion efficiency in the modulated soft channel as well as to examine the influence of surface charge mobility-dependent slip velocity on the electrokinetics. The laterally mobile adsorbed surface charge modifies the slip velocity condition, which is coupled with the induced streaming potential. The ion partitioning effect arises due to the step change in dielectric constant between the PEL and the electrolyte that modifies the distribution of ions, which is incorporated through the Born energy difference of ions. The nonlinear coupled set of equations governing the electrokinetics in a soft channel is solved numerically through a control volume approach. A simplified model based on the Debye–Hückel approximation under certain limiting conditions is also derived, which compares well with the present numerical model for a lower range of charge density and non-overlapping Debye layers. We find that a modulation of a nanochannel by coating a PEL of lower dielectric constant on hydrophobic charged walls can significantly enhance the streaming current and energy conversion efficiency. In contrast with existing studies, we find that the mobile surface charge can have a positive impact on the electrochemical energy conversion efficiency in a soft nanochannel. The mobility of the surface charge attenuates the streaming current in a PEL-free channel and can enhance the streaming current for a suitable choice of PEL volumetric charge density.

Multiband terahertz metamaterial perfect absorber for microorganisms detection

We report a multi-resonant terahertz (THz) metamaterial perfect absorber (MPA)-based biosensor in the working frequency range of 0 - 3.8 THz for sensing of microorganisms (such as fungi, yeast) and wheat pesticides. Nearly 100% absorption is realized at f_1= 1.7THz, f_2= 2.8THz, f_3=3.2THz, and f_4=3.5THz. We designed our THz MPA sensor making resonators’ gap area compatible with the microorganisms’ size. To obtain optimum performance of the MPA, a mapping of amplitudes and shifts in the absorption resonance peaks with different structural parameters of the resonators is carried out. A very high-frequency shift is obtained for microorganisms such as Penicillium chrysogenum (fungi), yeast, and pesticides (Imidacloprid, N, N-Diethyldithiocarbamate sodium salt trihydrate, Daminozide, N, N-Diethyldithiocarbamate sodium salt hydrate, and Dicofol). An equivalent circuit model using Advance Design System (ADS) software is developed. The calculated results through the model show similar trends as obtained in the simulations using CST. Investigations of the effect of incidence angle of THz wave on the absorption spectra of the MPA are also carried out. It is found that incidence angle does not impact the stability of the lower resonance absorption peak (1.79THz). Due to the wide working frequency range, the proposed sensor is extremely suitable for the detection of all range of pesticides because their specific absorption fingerprint lies in the frequency range of 0–3.8THz. We believe that our sensor could be a potential detection tool for detecting pesticide residues in agriculture and food products. The THz MPA-based biosensor is capable of detecting a very small change in the effective dielectric constant of the MPA environment. Therefore, it can also offer huge opportunities in label-free biosensing for future biomedical applications.

Tuning optical, dielectric, and electrical properties of Carboxymethyl cellulose (CMC) doped with Cobalt ferrite (CoFe2O4) nanoparticles via laser ablation for flexible electronic devices

Studying a series of Carboxymethyl cellulose (CMC)/Cobalt ferrite (CoFe2O4) films with different content of Cobalt ferrite (CoFe2O4). By using a pulsed laser ablation approach, the CoFe2O4 was implanted into the CMC polymeric material. The synthesized nano-films have been examined via XRD, FESEM, and FTIR besides thermal, electrical, and optical examinations. FESEM illustrations clearly show that size reduction is accelerated by increasing the laser irradiation period to 20 min. The CMC/CoFe2O4 polymeric film with a laser irradiation time of 5 min demonstrates an average grain size ∼1.75 µm, while with t = 20 min it was ∼ 0.25 µm. Thermal behavior demonstrates introducing higher thermal stability with raising cobalt ferrite ratio. Moreover, the activation energy was 151.93 kJ mol−1 for t = 0.0 min, while becomes 167.66 kJ mol−1 at t = 10.0 min, Then it dropped into 160.12 kJ mol−1 at t = 20.0 min. The notable raising in E * firstly is owing to complexation tendency, while the density of the H-bond leads to activation energy dropping at t = 20 min. Optical behavior shows a decline in absorption edge from 5.4 e.V at t = 0.0 min to 4.8 e.V at t = 10, 20 min. The change in dielectric constant (ε′) by increasing frequencies upon cobalt ferrite content variation provokes a great development for the electrical behavior of the studied compositions.

Enhanced physical and electrical properties of HfO2 deposited by atomic layer deposition using a novel precursor with improved thermal stability

With the increased application range of Hf-based oxides in memory devices, such as high-k capacitors, gate dielectrics, and ferroelectric devices, improvement in the properties of HfO2 thin films have been received considerable attention. To achieve improved properties HfO2 thin films deposited by atomic layer deposition (ALD), one strategic way is to develop a process incorporating a new precursor with improved thermal stability. In this paper, HfO2 thin films were deposited by ALD process using a novel precursor modified with a cyclopentadienyl-based ligand to improve thermal stability, and the improved properties were investigated. The ALD process window has been extended to higher temperatures. In addition, with increases in deposition temperature, the impurity concentration, surface roughness, density, and crystallinity of HfO2 were improved. Finally, the HfO2 thin film deposited at a high temperature significantly reduced the leakage current (from 5.2 × 10−7 A/cm2 to 3.1 × 10−9 A/cm2 measured at 0.7 V) without a significant change in dielectric constant, and the remanent polarization characters were also observed. Therefore, we suggest that HfO2 deposited using the proposed hafnium precursor can be applied as a key high-k component in next-generation memory devices and ferroelectric-based semiconductor devices.

On 3D printing of thermoplastic polyurethane over woven fabric for wearable sensors

ABSTRACT In the past two decades several studies have been reported on thermoplastic-based 3D printed sensors. However, little has been reported on wearable sensors prepared by thermoplastic printing on woven fabric, especially for four-dimensional (4D) properties. This study reports the 3D printing of thermoplastic polyurethane (TPU) on woven fabric by using a fused filament fabrication (FFF) setup for the fabrication of wearable sensors. Further, rheological, mechanical, voltage resistance (V-R), radio frequency (RF), and 4D capabilities of the 3D printed substrate have been established. The 3D printing of TPU on woven fabric was performed at 225°C nozzle temperature with a printing speed of 21 mm/s, and infill density was kept at 80% and 100%. The RF characteristics were calculated using a vector network analyser (VNA) which suggests that there is no shift in resonating frequency (2.60 GHz at −81 dB) for ring resonator printed with 100% infill density (with an increase in strain value), whereas for 80% infill density sensor there was a notable shift in resonating frequency (from 2.82 GHz at −75 dB to 2.71 GHz at −76 dB) when the sensor was strained under load which further lead to a change in dielectric constant () and loss tangent ().

Light‐Induced Dielectric Enhancement in a 2D Dion–Jacobson Type Perovskite Phase Transition Material

AbstractStimuli‐responsive materials, showing bistable behaviors between two distinct states under external stimuli, can be potentially applied as basic components of modern electrical and electronic devices. 2D hybrid perovskites hold a promise to switch and tune dielectric bistability based on their solid‐state phase transitions. Here, strong dielectric enhancements are successfully actualized by virtue of light illumination in a Dion–Jacobson (DJ) type 2D hybrid perovskite, (HDA)(MA)2Pb3Br10 (1, where HDA is 1,6‐hexanediammonium and MA is methylammonium). Upon heating, 1 exhibits an ordered–disordered phase transition ≈ 324 K (Tc), accompanying a transition from its low to high dielectric state. Strikingly, its light‐induced dielectric constant changes are greatly enhanced with a magnitude up to 250% near the Tc, superior to most traditional inorganic phase transition materials. This process closely relates to the photoexcited dielectric effect that is caused by the interband photo‐excitation. Benefitting from the stability of DJ‐type perovskite structure, the switching cycles of dielectric enhancement display operational stability with superior anti‐fatigue characteristics. As per the knowledge, the findings of this strong dielectric enhancement are unprecedented in the family of 2D DJ‐type hybrid perovskites, which will facilitate broad interest in exploiting new stimuli‐responsive materials to assemble high‐performance smart electronic devices.

An Interdigital Microwave Sensor Based on Differential Structure for Dielectric Constant Characteristics Measurement.

In this work, a microwave resonator sensor with a unique configuration consisting of three resonators and two feedlines is proposed. This novel design aims to improve the performance and functionality of microwave resonator sensors for various applications. The frequency response of the sensor to materials with different dielectric constants is simulated. The results show that the most sensitive region of the sensor is located on the first interdigital structure, and placing the materials in other regions would enhance the linear correlation of its frequency response. The sensor also exhibits the ability to distinguish whether the same material has defects and the ability to qualitatively detect subtle changes in dielectric constant. Finally, the proposed sensor is fabricated and measured under the condition consistent with the simulation environment. The measured results are basically consistent with the simulation results, which confirms the potential of this sensor in detecting dielectric constants and resolving materials with defects, and the response of the sensor to the materials under test demonstrates its potential in measuring different thicknesses and loss tangents.

Studies of structural, dielectric, and optical properties of CuCoFeO4 spinel for high frequency, microwave, and optoelectronic applications

In this study, we synthesized by the sol-gel method the CuCoFeO4 spinel and studied its structural, dielectric, and optical properties. The sample exhibits a regular cubic spinel structure (Fd3¯m space group). Semiconductor behavior with the CBH model was observed from the variation in electrical conductivity as a function of frequency and temperature. Summerfield scaling merges conductivity isotherms into a single master curve. Non-Debye relaxation is shown in the electric modulus of the prepared composition. The impedance spectra indicate the effects of both grain and grain boundary contributions on electrical properties. The impedance analysis is presented with electrical processes modeling in the sample. This is done using an equivalent circuit model comprising a parallel RC circuit for grains and grain boundaries. The obtained simulated results agree with the measured results. Maxwell-interfacial Wagner's polarization theory was used to explain dielectric constant change. The synthesized material exhibits low dielectric constants and dielectric losses at higher frequencies, as well as high electrical resistivity. These properties make CuCoFeO4 spinel a suitable candidate for high-frequency applications and microwave absorption devices. Moreover, CuCoFeO4 spinel presents low band gap energy, making it a suitable material for visible-light absorption.