Permittivity Research Articles

Preparation of porous lead zirconate titanate piezoelectric ceramics via vat photopolymerization combined with burnt polymer spheres technique

Porosity plays an important factor on the electric properties of piezoelectric ceramics. Here, we propose a promising method for the fabrication of Lead zirconate titanate (PZT) piezoelectric ceramics using vat photopolymerization, and effectively modulate porosity of printed PZT piezoceramics through adjusting the polystyrene (PS) content. After a post-process, the PZT piezoelectric ceramics showed single perovskite structure and porous microstructures formed by PS, with porosity ranging from 8.57 % to 27.02 %. With the increase of porosity, the piezoelectric strain constant (d33) and dielectric permittivity (ɛr) decreased gradually due to the reduction in the volume fraction of PZT phase per unit volume. When the PS content was 20 vol%, d33 and ɛr reached the maximum values. The sintered PZT piezoelectric ceramics exhibited excellent electrical properties (ɛr=2364, d33=399 pC/N, g33=1.91×10−2 Vm/N, d33g33=7.62×10−12 m2/N and Kt=43.94 %). This work not only provides technical support for manufacturing advanced ceramics with tunable porosity through the use of PS powders, but also lays the foundation for preparing functional ceramics with complicated designed structures through vat photopolymerization technology.

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.

Influence of the presence of ions on the dielectric properties of reverse micelle systems

AOT/isooctane/water reverse micelle solution was doped with ionic salts solutions: sodium chloride, potassium chloride, tetramethylammonium chloride, tetramethylammonium bromide, sodium butyrate and sodium benzoate. Each system was investigated for the influence of ionic additives on dielectric properties: electric permittivity, conductivity and nonlinear dielectric effect (NDE). Studies showed that addition of salts noticeably changes the dielectric parameters. Based on the salts used in this research, the most common effect is a decrease of electric permittivity, conductivity and NDE effect. However, addition of some ions can lead to their increase, which was proved in the case of sodium benzoate. The registered changes were explained based on the percolation effect and changes in rigidity of the micellar surfactant shell due to the incorporation of the dissolved ions into the micellar structure.

Influence of cold plasma treatment on the PS/TiO2 film’s optical properties of nanocomposite surfaces

Organic plastics have been used due to their impressive chemical and mechanical properties, though, there is still room for improvement to achieve higher dielectric permittivity. In the present work, the blank polystyrene (PS) was doped with nanoparticles of titanium dioxide (TiO2) at different ratios (1 %, 2 %, and 3 %) employing the casting method. The blank PS and nanocomposite films of PS/TiO2 have been exposed to the cold DBD plasma system. Subsequently, calculations including the absorption coefficient, refractive index, extinction factor, energy gap, and dielectric constant (real and imaginary) were conducted. Results show that the absorption coefficient and refractive index were increased, and the extinction factor was decreased due to the high absorption. Real dielectric constant increased after the doping process, while the imaginary dielectric constant had minimal values in loss of absorption indicating small losses in absorption. The XRD examination shows semi-crystalline and crystalline structures. Applying this method might have a broad application in various devices used in cutting-edge electronics.

Dielectric and Mechanical Studies of Cyclohexylammonium Hydrogen Maleate Hemihydrate Single Crystals

Abstract CYHMH crystal was grown using solution growth technique The crystal corresponds to monoclinic structural system with C12/C1 space group (centrosymmetric in nature) and The final cell constants values are a = 24.109 (2) Å, b = 5.5157(4) Å, c = 18.6739(14) Å, β = 110.807(2)°, volume = 2321.2(2) Å. Mechanical studies were measured using Vicker’s hardness tester and n was 1.40, therefore the CYHMH crystals comes under hard materials category. The elastic toughness (stiffness) decreased with increases in applied load. Dielectric permittivity of CYHMH and loss factor were calculated as a function of log frequency. While increasing the temperature the dielectric parameters (dielectric constant, loss, AC conductivity) also increased. The energy required to activate the conductivity were also calculated for higher frequency region.

Strong microwave absorption of Fe-deficient SrFe9.4Cu0.8Sn0.5O19-d with enhanced permittivity and ferromagnetic resonance by high annealing temperature

The oxygen environments of Fe+3-δ ions determine the magnetic anisotropy of M-type ferrites. The high annealing temperature increases the oxygen content and decreases the lattice strain in M-type SrFe9.4Cu0.8Sn0.5O19-d ferrites. The anisotropic field and the coercive field decrease with the increasing annealing temperature. Annealed at 1400 °C, a ferromagnetic resonance is observed at the frequency above 9.5 GHz, with the real part having a peak and the imaginary part of the permeability having a high plateau over a wide frequency range. It enables the microwave energy' dissipation by the magnetic loss. Furthermore, the extra oxygen ions ease up the dipole polarizations' rotation and significantly increase the dielectric permittivity. At thin thickness of 1.3 mm, the effective absorption bandwidth (RL≤−10 dB) of SrFe9.4Cu0.8Sn0.5O19-d annealed at 1400 °C is 7.1+ GHz from 10.9 to 18+ GHz. SrFe9.4Cu0.6Sn0.6O19-d annealed at 1400 °C has the microwave absorption bandwidth of 8.8 GHz from 9.2 to 18+ GHz at 1.6 mm. Both are very promising microwave absorbing materials.

Advancing Cholesterol Detection: A Simulation Study on SrTiO3-Based BioFET Biosensors

This study presents an analytical model of a strontium titanate (SrTiO3)-based biological field-effect transistor (BioFET) for cholesterol detection. Known for its high dielectric permittivity, surface charge regulation, and superior ionic and thermal conductivity, SrTiO3 enhances the functionality of biosensors. The BioFET employs a gate functionalized with a cholesterol-specific enzyme, which facilitates potentiometric measurements of cholesterol concentrations. The model establishes a quantitative relationship between cholesterol concentration and gate voltage in enzyme-immobilized SrTiO3, demonstrating the high selectivity of SrTiO3-based BioFETs for cholesterol detection. This indicates their potential in developing diagnostic tools for cholesterol-related conditions and monitoring food quality. Additionally, the analytical model effectively predicts the behavior of the detection mechanism in electrochemical BioFET biosensors, underscoring its innovative application in fields such as microelectronics, sensors, and catalysis.

Plasma‐Driven Tuning of Dielectric Permittivity in Graphene (Small 27/2024)

Plasma‐Driven Tuning of Dielectric Permittivity in Graphene (Small 27/2024)

A low-loss and medium dielectric permittivity SrTiO3/HIPS composite for rapid prototyping of next-generation microwave devices

Composite polymer/ceramic filaments for material extrusion-based fused filament fabrication (FFF) additive manufacturing, using strontium titanium oxide (SrTiO3) ceramic fillers and high impact polystyrene (HIPS) thermoplastics were produced and their dielectric and physical properties characterised for the first time. Relative permittivity (εr), quality factor (Q × f) and dielectric loss (tanδ) were measured as a function of ceramic solids loading (vol%) at 5 GHz. εr = 4.6, Q × f = 38,378 GHz and dielectric loss tanδ = 0.001 were obtained for a SrTiO3/HIPS ceramic polymer composite, with 15 vol% (46 wt%) solids loading. A Plackett–Burman design of experiments was used to optimize the printing process of the ST/HIPS composites. The results of this optimisation helped achieve 3D printed parts with near-full density (99 %) and εr = 5.3, tanδ = 0.001. The composite materials exhibit reduced dielectric losses compared with commercially available feedstocks for FFF that are currently used for functional prototyping in the radiofrequency and telecommunications industry.

Effects of finite counterion size and nonhomogeneous permittivity and viscosity of the solution on the electrokinetics of a concentrated salt-free colloid.

In the present work, a general model of the electrokinetics and dielectric response of a concentrated salt-free colloid is developed which includes consideration of the finite size of the counterions released by the particles to the solution, a nonhomogeneous permittivity of the solution, the existence of Born and dielectrophoretic forces acting on the counterions, and especially the fact that the solution viscosity and diffusion counterion coefficient are allowed to be functions of the local counterion concentration. These effects have recently been discussed by J. J. López-García etal. [Phys. Rev. Fluids 4, 103702 (2019)10.1103/PhysRevFluids.4.103702] in the case of dilute colloids in general electrolyte solutions. The objective of this work is to explore the new effects and their influence on the electrokinetic response of concentrated salt-free systems. Present results confirm previous findings regarding the important increases of the dc electrophoretic mobility and dc electrical conductivity, as well as huge increments of the dynamic electrophoretic mobilities at high frequencies when finite-ion-size effects were taken into account. In addition, consideration of the viscosity of the solution and of the counterion diffusion coefficient as functions of the local counterion concentration leads to a decrease of the magnitude of the previous electrokinetic results. The theory incorporates a more convenient hard-sphere hydrodynamic model to account for the nonhomogeneous viscosity of the solution than others proposed in previous works in the literature. A comparison is elaborated on between electrokinetic and dielectric responses with different levels of complexity of the theoretical model, starting from the case of pointlike counterions and following with the inclusion in sequence of additional aspects such as finite counterion size, nonhomogeneous electrical permittivity with associated Born and dielectrophoretic effects, and, finally, position-dependent viscosity and diffusion counterion coefficient, and clearly shows the influence of individual effects on the general electrokinetic response and especially the relevant role the nonhomogeneous viscosity on the dc and ac electrokientic behavior of salt-free colloids.

OBTAINING POROUS CARBON MATERIAL AND INVESTIGATION OF ITS PHYSICAL AND CHEMICAL PROPERTIES

The proposed method for producing porous carbon material involves the thermal decomposition of brown coal from Kazakhstan deposits, optimized by a treatment process where steam is used for coal activation, enhancing the safety of the process. The resulting product exhibits high characteristics, including high dielectric permittivity, specific surface area, and capacity, making it effective for use in supercapacitors as an electrode material and for hydrogen storage. The coal carbonization process includes an initial low-temperature (at 180°C, with a heating rate of 10°C/min) treatment of the raw material in the presence of air for 1 hour, followed by carbonization in an inert atmosphere at temperatures ranging from 180-900°C with a heating rate of 5°C/min, and steam activation at the maximum temperature for 1 hour of the coal ground to a 0.1 mm fraction. The material is then extruded into cylindrical shapes (diameter: 2-3 mm, length: 5-10 mm) using a binder material: starch - 5%, sodium hydroxide - 0.5%, water - 17%.

Insights into a Defective Potassium Sulfido Cobaltate: Giant Magnetic Exchange Bias, Ionic Conductivity, and Electrical Permittivity

AbstractThe novel potassium sulfido cobaltate, K2[Co3S4] is introduced, with 25% vacancies of the cobalt positions within a layered anionic sublattice. The impedance and dielectric investigations indicate a remarkable ionic conductivity of 21.4 mS cm−1 at room temperature, which is in the range of highest ever reported values for potassium‐ions, as well as a high electrical permittivity of 2650 at 1 kHz, respectively. Magnetometry results indicate an antiferromagnetic structure with giant intrinsic exchange bias fields of 0.432 and 0.161 T at 3 and 20 K respectively, potentially induced by a combination of the interfacial effect of combined magnetic anionic and nonmagnetic cationic sublattices, as well as partial spin canting. The stability of the exchange bias behavior is confirmed by a training effect of less than 18% upon 10 hysteresis cycles. The semiconductivity of the material is determined, both experimentally and theoretically, with a bandgap energy of 1.68 eV. The findings render this material as a promising candidate for both, active electrode material in potassium‐ion batteries, and for spintronic applications.

Measuring Dielectric Properties of MARDI 76 (MRQ76) Rice at the Frequency of 915 MHz and 2.45 GHz

The microwave heating system has been widely used in the food processing and postharvest handling of rice. However, to develop efficient heating energy for the heating and drying process, the knowledge of permittivity or dielectric properties of the MARDI 76 (MRQ76) rice is quite important. The penetration and power dissipation of microwave inside the MARDI 76 (MRQ76) rice is strongly dependent on its dielectric properties or permittivity. Furthermore, characterisation of changes in permittivity or dielectric properties of MARDI 76 rice at elevated temperatures is essential for designing the microwave heating device and system. The permittivity or dielectric properties of MARDI 76 rice (MRQ76) were measured using Agilent open-ended coaxial-line probe and Agilent E5071C Network Analyser. The temperature of the MRQ 76 rice sample was regulated using a WiswCircu Circulator Water bath between temperatures of 27ºC to 70ºC. MARDI MRQ 76 rice sample was placed into the temperature-controlled stainless steel sample holder with water jacket assembly which was designed for permittivity measurement at different temperatures. The effect of temperature on dielectric properties of MARDI 76 rice, power dissipation and penetration depth of microwave radiation at the Industrial, Scientific, and Medical (ISM) heating frequency of 915 MHz and 2.45 GHz was assessed. Results indicated that both dielectric constant and dielectric loss of MARDI 76 rice samples increased with increasing temperature. Power dissipation of microwave radiation inside MARDI 76 rice increases with an increase in temperature. On the other hand, the penetration depth of microwave radiation into the MARDI 76 rice decreased with the increase in temperature. The result of this study shows dielectric properties and heating temperature of MARDI MRQ 76 rice play an important role in designing the microwave heating system for MARDI MRQ 76 rice.

Measuring microwave dielectric properties of materials: Theory and applications

The knowledge of the microwave dielectric properties of materials has great significance for scientific and industrial applications. The measurement of the complex permittivity, ε*=ε′−iε″, in this frequency range, can be made using the small perturbation theory. In this method, the resonance frequency and the quality factor of a cavity, with and without a sample, can be used to calculate the complex dielectric permittivity of the material. The design of a cavity resonator implies solving the Maxwell equations inside that cavity, respecting the boundary conditions.This method was applied to characterize the dielectric properties of yttrium ferrites, that were prepared by solid state reaction, and exposed to different heat treatments. Structural and morphological characterizations were also performed. A correlation between these properties is presented. The best results, in terms of energy storage at microwave frequencies, are obtained for the sample heat treated at 1400 °C, with ε´=6.4, at 2.7 GHz, and with losses tangent lower than 10–4, at 300 K.

Facile design of a low-cost laser CUT-OFF filter with PMMA polymer nanocomposite doped with Mg0.5Ni0.5Fe2O4: structural, optical, and dielectric properties

This study employed the sol gel auto-combustion approach to synthesize Mg0.5Ni0.5Fe2O4 spinel ferrite nanoparticles. Additionally, the casting method was used to fabricate Mg0.5Ni0.5Fe2O4/PMMA nanocomposite polymer films. The structural properties were analyzed by the utilization of x-ray diffraction pattern (XRD), high resolution transmission electron microscope (HRTEM), and field emission scanning electron microscope (FESEM). The UV-visible spectrophotometer examination was used to evaluate the optical properties of the produced nanocomposite films, such as absorbance, transmittance, indirect energy band gap, Urbach energy, excitation coefficient, and refractive index. Two indirect optical energy gaps are calculated, whereas they decreased from 4.56 eV to 4.33 eV, and from 4.04 eV to 3.01 eV, while the Urbach energy increased from 0.304 eV to 0.524 eV as the nanofillers increased from 0 to 4 wt%. An investigation was conducted to examine the impact of nanoparticle doping on the dielectric constant, electric modulus, and ac conductivity. The Mg0.5Ni0.5Fe2O4/PMMA nanocomposite films demonstrate higher permittivity and ac conductivity and a lower dissipation factor and electric modulus compared to pure PMMA. The dielectric permittivity (ε′) increased from 2.76 to 3.43 at a constant frequency 100 Hz up to 2 wt.% of Mg0.5Ni0.5Fe2O4 then decreased to 2.41 while the dissipation factor tan(δ) decreased from 0.1 to 0.046 at the same frequency. The nanocomposite films are well-suited for utilization in CUT-OFF selective laser filters, solar cells, energy storage devices, and other applications in related industries.

Studying the structural, thermal, mechanical, and dielectric features of PVA/iron oxide@SiO2 polymer nanocomposites for electrical applications

Fe3O4@SiO2 (FS) nanocomposite was synthesized through the co-precipitation method and utilized as a filler material in the polyvinyl alcohol (PVA) matrix to obtain PVA/iron oxide@silica Fe3O4@SiO2 (PFS) films. This study presents the synthesis and characterization of flexible polymer nanocomposites comprising polyvinyl alcohol (PVA) matrices embedded with iron oxide @ silica. Through the analysis of the composite, we observed a significant enhancement in the thermal stability of the nanocomposites with increasing Fe3O4@SiO2 content. X-ray photoelectron spectroscopy (XPS) spectra have been used to provide more information about the chemical state and electronic structure of the polymer film. Dielectric spectroscopy revealed notable improvements in electrical properties, including increased real electric modulus and permittivity. Mechanical investigation showed an improvement in the tensile strength, meanwhile, Young's modulus has improved from 341.2 to 1789.8 MPa, indicating that (PVA) and FS successfully complexed and interacted strongly. These findings underscore the potential of these nanocomposites for high-performance applications in energy storage devices and other fields requiring robust dielectric materials.

Electrically induced and controlled piezoelectricity

The quasi-linear electromechanical effect, which resembles piezoelectricity, can be induced by strong electric field in any solid dielectric. This effect is defined as linearized electrostriction, which is observed in the biasing electric field and is proportional to the square of the dielectric permittivity. The present work analyses physical mechanisms of the occurrence of such an effect in the piezoelectrics, the paraelectrics and the relaxor ferroelectrics, taking into account the inertia of electromechanical response. Hysteresis-less electromechanical control of deformation is used in actuators and tuneable microwave devices. The efficiency of the induced piezoelectricity is maximal in dielectrics with high permittivity, while the efficiency is ensured by mechanisms of low-inertia quasi-elastic polarization. To assess the maximum performance of piezoelectric actuators made of different materials, the method of dielectric spectroscopy is used.

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.

Enhancing the dielectric and piezoelectric properties of Pb0.99Gd0.01Zr0.53Ti0.47O3 ferroelectric ceramics by Sr-doping

Recently, high-performance lead zirconate titanate (Pb([Formula: see text]Tix)O3, PZT) ferroelectric ceramics have attracted intensive attention due to their wider operating temperature range, better temperature stability, as well as larger piezoelectric properties and higher energy conversion efficiency. In this study, the perovskite-type ferroelectric ceramics with a chemical formula of [Formula: see text][Formula: see text]Srx[Formula: see text][Formula: see text]O3 ([Formula: see text] and 0.02, abbr. PGZT and PGSZT, respectively) were prepared by the traditional solid-state reaction route. The influences of Sr-doping on the phase structure, dielectric properties, ferroelectric properties and piezoelectric properties of the PGZT ceramics were comprehensively investigated. The field-dependent P–E hysteresis loops of PGSZT were measured in the frequency range of 0.05–10[Formula: see text]Hz and temperature range of 20–100∘C. The results show that Sr-doping not only enhances the dielectric permittivity and piezoelectric coefficient of PGZT, but also decreases its dielectric loss tangent, with the [Formula: see text] value of 473[Formula: see text]pC/N, [Formula: see text] value of 1586 and [Formula: see text] value of 0.016 found in PGSZT. Also, PGSZT shows a high Curie temperature ([Formula: see text]) of [Formula: see text]C. The underlying mechanisms of the property enhancement were identified as that the introduced [Formula: see text] replaces the volatile [Formula: see text] located at the A-site of the perovskite structure, thereby reducing the concentration of lead vacancies and promoting the grain growth of the ceramics, consequently enhancing the dielectric and piezoelectric properties of PGZT. On the other hand, the frequency change in the low-frequency range ([Formula: see text][Formula: see text]Hz) played a significant impact on the remanent polarization ([Formula: see text]) and internal biased electric field ([Formula: see text]) of PGSZT, but the frequency dependence of coercive field ([Formula: see text]) tends to diminish in the high-frequency range ([Formula: see text][Formula: see text]Hz).

Density dependence for the dielectric permittivity of simple gases and liquids

The present work is devoted to the analysis of polarization effects in atomic systems of the argon type. Special attention is given to the manifestation of the polarizabilities of two particles in the density dependence of the dielectric permittivity of a system and its effective molecular polarizability. It is shown that the effective polarizability of a molecule in the liquid state of a system is mainly caused by deviation of the molecular distribution in the first coordination layer from the spherical one. Due to this, the atomic polarizability inherent to rarefied gas increases practically twice near the triple point. The interconnection between the atomic polarizability and the proper volume of an atom is discussed in detail. It is established that the optimal size of an atom follows from the kinematic shear viscosity measurements.