Dependent Dielectric Constant Research Articles

Preparation and electrical properties of Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramics by the doping of Mn ions

A series of Ba0.85Ca0.15Zr0.1(Ti1-xMnx)0.9O3 (x = 0%, 2%, 4% and 8%; Ba0.85Ca0.15Zr0.1Ti0.9O3 abbreviated as BCZT) ceramics were prepared via the sol-gel method. No secondary phase was detected in XRD patterns, indicating that Mn entered into the unit cell to form a solid solution. The microstructures for Mn-doped BCZT ceramics show Mn can inhibit the growth of BCZT grain size. The dependence of dielectric constant on temperature shows that the Curie temperature decreases and the degree of dispersed phase increases with the increase of the doping amount. When the doping amount is x = 2% and x = 4%, the hysteresis loop shows a significant shrinkage, the remanent polarization is significantly reduced, and the shrinkage is more severe under high electric field. The double hysteresis loops appeared, indicating that the hysteresis loop of BCZT ceramic can be adjusted by doping a certain amount of Mn ions. The sample of x = 4% shows an energy density of 0.18 J/cm3 and an energy efficiency of 58.5%.

Mathematical Model and Practical Implementation of Transformer Oil Humidity Sensor

The mathematical dependence of the integral dielectric constant of transformer oil on its humidity is obtained. It is shown that the increase in humidity in the range from 0% to 0.5%, which corresponds to its allowable change, is accompanied by a monotonic increase in the integral dielectric constant along the nonlinear dependence. The design of a high-frequency humidity sensor in the form of a band asymmetric waveguide is proposed, which transforms the latter into a phase shift of the information wave. The mathematical model is developed and the transformation equation is obtained. It has been experimentally established that the total relative error, which consists of the error of this model, the instrumental error of the hard-ware and the subjective error of removing the measured information does not exceed 2%. The article is devoted to solving the problem of reliability of technological equipment and is part of an interdisciplinary study on the development of a set of energy efficient equipment for feed preparation, which is performed on the basis of laboratories of Vinnytsia National Agrarian University.

Effect of molar concentration on the structural, linear and nonlinear optical properties of CuS (covellite) thin films

CuS thin films with various molar concentrations at 70 °C temperature were deposited by Chemical Bath Deposition. The effect of molar concentration on the structural, linear optic, nonlinear optic and morphological properties of CuS films were deeply investigated. X-ray diffraction (XRD) analysis exhibited that CuS films were formed in polycrystal structure and hexagonal phase. The fundamental optical parameters of films such as energy band gap, reflection and extinction coefficient were determined with the results of optical transmission and optical absorption by UV–vis spectrophotometer. The energy band gap values were reduced with increasing films thickness. Moreover, the dependence of the optical dielectric constants, loss tangent, optical conductivity, surface and volume energy loss function values on the molar concentrations were studied. Furthermore, the third order nonlinear optical susceptibility and nonlinear refractive index, which is considered to be the base of the first order optical susceptibility with nonlinear optical properties were discussed in detail.

Structural and electrical characteristics of double perovskite: Sr2FeMoO6

Sr2FeMoO6 ceramic material has been prepared by a mixed oxide reaction route. Analysis of structural, microstructural and electrical characteristics of the material has been analyzed in the limit of frequency (1 kHz–1 MHz) and temperature (25–400 °C). From the preliminary X-ray structural analysis, the structure of the material is found to be tetragonal. The frequency dependence of dielectric constant has been explained by Maxwell-Wagner effect. There is no anomaly observed in the temperature dependent dielectric analysis. The analysis of the Nyquist plot suggests the existence of only grain effect and the sample shows both characteristics of negative and positive temperature coefficient of resistance (NTCR and PTCR). The frequency and temperature dependence of ac conductivity obeys Jonschor’s power law. The analysis of temperature dependence of frequency exponent suggest that the conduction mechanism is follow the overlapping large polaron tunneling (OLPT) and correlated barrier hopping (CBH) conduction phenomena and the activation energy has also been calculated by using Arrhenius equation. The occurrence conduction phenomenon belongs to space charge limited conduction process. The observed low-leakage current density from J-E characteristics curve may be applicable for high temperature applications.

Synthesis, structural evolution, and dielectric properties of a new perovskite solid solution (Pb0.5Sr0.5)(Zr0.5Ti0.5)O3–PbTiO3

AbstractTo explore lead‐reduced dielectric materials in the SrTiO3–PbTiO3–PbZrO3 ternary system, a novel solid solution between relaxor ferroelectric (Pb0.5Sr0.5)(Zr0.5Ti0.5)O3 and ferroelectric PbTiO3, namely (1 − x)(Pb0.5Sr0.5) (Zr0.5Ti0.5)O3–xPbTiO3 (lead–strontium–zirconate–titanate [PSZT]–PT), has been synthesized in the perovskite structure by high‐temperature solid‐state reaction method in the form of ceramics. The crystal structure and phase symmetry of the materials synthesized were analyzed and resolved based on X‐ray powder diffraction (XRD) data through both the Pawley and Rietveld refinements. The results of the structural refinements indicate that at low PT‐concentration end of the solid solution system, for example, x = 0.05, the PSZT–PT solid solution exhibits a cubic structural symmetry (with the space group Pm‐3m). As the PT concentration (x) increases, the structure of (1 − x)PSZT–xPT gradually transforms from the cubic to a tetragonal (P4mm) phase. In the composition range of x = 0.10–0.25, a mixture of the cubic and tetragonal phases was identified. As the concentration of PT increases, the proportion of the tetragonal phase increases at the expense of the cubic phase. For a composition of x > 0.25, a pure tetragonal phase is observed. The dielectric properties of the materials were studied by measuring the permittivity as a function of temperature at various frequencies. For the composition of x = 0.05, the temperature dependence of dielectric constant shows typical relaxor behavior. For x = 0.35, the dielectric peaks indicate a normal ferroelectric phase transition. Overall, a structural transformation from a central‐symmetric, nonpolar cubic phase to a non‐centrosymmetric, polar tetragonal phase is induced by the substitution of PT for PSZT in the pseudo‐binary solid solution of (1 − x)PSZT–xPT, which also reveals an interesting relaxor to ferroelectric crossover phenomenon.

Thermally Stable Piezoelectric Performance of MnO2 Inserted Pseudo-tetragonal Phase Existent CaBi2Nb2O9-based Ceramics

ABSTRACT Pseudo-tetragonal phase boundary existent Ca0.60(Li0.5Bi0.5)0.40Bi2Nb2O9:xwt%MnO2 (CBNL:xMn) ceramic series is fabricated to investigate the ferroelectric and piezoelectric properties. Pure CBNL and CBNL:xMn ceramics have maintained their pseudo-tetragonal phase boundary even after the insertion of Mn ions. The addition of MnO2 in CBNL has improved the multifunctional properties of material at x = 0.20. CBNL:0.20Mn has shown the relative density of 98%, saturated polarisation (PS ) of ~ 13.5 µC/cm2, high piezoelectric coefficient (d33 ) of ~ 25 pC/N, and high impedance of ~ 8.9 × 108 Ω at room temperature, which are the much improved values as compared to pure CBN or CBNL ceramics. The dielectric constant (ɛr ) dependence on temperature is presenting the sharp peak of CBNL:0.20Mn ceramic at Curie temperature (TC ) ~ 918°C confirming the strong ferroelectric nature of the ceramic. Importantly, poled CBNL:0.20Mn ceramic has shown the thermally stable depoling performance, which remains 92% (23 pC/N) of its initial room temperature value even after annealing the sample at 800°C. Results indicate the clear significance that the introduction of multivalence Mn ions in the pseudo-tetragonal existent region of CBNL has improved the multifunctional properties of the material, making it a strong candidate to be utilised in actuators and high-temperature piezoelectric devices.

Electrical conduction mechanism and dielectric relaxation of bulk disodium phthalocyanine

AC conductivity and dielectric characteristics of disodium phthalocyanine (Na2Pc) in a pellet form were investigated in a frequency range from 45 Hz to 3.12 MHz and a temperature range from 303 to 423 K. The charge carrier transport mechanism was determined according to the correlated barrier hopping model (CBH). Also, the electrical parameters were estimated in light of this model. The thermal activation energy of AC conductivity decreases with increasing frequency. The behavior dependence of dielectric loss and dielectric constant on temperature and frequency was discussed. The behavior of dielectric loss was explained based on the Giuntini model. The maximum value of barrier height, was obtained to equal The results showed that the type of relaxation mechanism is a non-Debye one. The activation energy is calculated for dielectric relaxation to be

Dielectric anomalies and structure evolution of annealed (1-x)Pb(Sc1/2Ta1/2)O3-xPb(In1/2Nb1/2)O3 ceramics

The (1-x)Pb(Sc1/2Ta1/2)O3-xPb(In1/2Nb1/2)O3 [(1-x)PST-xPIN] (x = 0.2, 0.4, 0.6, and 0.8) solid-solution ceramics were synthesized by conventional solid-state reaction method. The phase structure, microstructure, and dielectric properties were analysed. In order to obtain various ordering degrees, annealing treatment at 700 °C for 10 h, 20 h, 40 h, and 120 h was conducted on (1-x)PST-xPIN ceramics. The degree of ordering increased significantly with the extension of annealing time in 0.8PST-0.2PIN composition. However, for other compositions, no any superlattice peak was observed at all times of annealing process, which was related to the presence of more pyrochlore phase. In addition to the low-temperature relaxation peaks associated with the disordered arrangement of B-site ions, two new dielectric anomalies were found in the temperature dependence of dielectric constant of annealed (1-x)PST-xPIN solid solution. For annealed 0.8PST-0.2PIN composition, the middle-temperature and high-temperature dielectric anomalies were attributed to the ordered PST region and the incommensurate structure induced by the competition between ordered PST and disordered PST, respectively. The high-temperature dielectric anomalies in 0.6PST-0.4PIN and 0.4PST-0.6PIN compositions originated from the contribution of the ordered PIN region in solid solution. Furthermore, the relatively weak superlattice diffraction spots of (111) were found in selected-area electron diffraction patterns of annealed 0.8PST-0.2PIN ceramic, indicating that the existence of alternately ordering arrangement of B-site ions. Combined with the analysis of element mapping, it was concluded that the annealed (1-x)PST-xPIN solid solution was composed of the ordered PST region, the ordered PIN region, and the disordered region constituted by PST and/or PIN.

Molecular dynamics study of thermal properties of polyamide nanocomposites reinforced with natural biofillers

Bio-based fillers have been used for reinforcements in thermoplastic polymer, predominantly in the past decade, to improve its mechanical and thermal performance. This study has made use of Molecular Dynamics (MD) simulations using Large-scale Atomic/Molecular Massively Parallel Simulator package to investigate the thermal behavior of polyamide 6 nanocomposites when they are reinforced with natural biofillers such as starch, cellulose, and coconut shell nanoparticles. A comparative study is conducted to examine the degree of improvement or deterioration of thermal properties under the effect of respective nanofillers. Density, glass transition temperature (Tg), heat capacity, thermal diffusivity, and thermal conductivity were inspected with simulations run in a temperature range of 200–600 K. Glass transition temperature has been calculated from three parameters, by the dependence of density, dielectric constant, and electrostatic energy on temperature. Non-equilibrium MD simulations using Fourier's law method were followed to calculate thermal conductivity. This study has concentrated on thermal evaluations of bio-based polyamide nanocomposites helpful in determining the flame retardancy of the materials.

Study on the structural and electrical transport properties of YMn0.9Cr0.1O3

In this work, the structural, micro-structural, dielectric, AC conductivity of rare earth manganite YMn0.9Cr0.1O3 have been reported. The compound is synthesized by sol–gel auto-combustion route. The X-ray diffraction study confirms the formation of hexagonal structure along with the onset of few orthorhombic peaks. The morphological study using scanning electron micrographs shows homogeneous distribution of particles with average particle size of 185 nm. Raman spectroscopy shows the A1Raman scattering line at ∼ 676 cm−1to be much stronger than the other Raman modes. The nature of frequency dependence of dielectric constant has been described by Maxwell-Wagner model. The frequency dependence of the conductivity at different temperatures as described by Jonscher’s plot suggests that the conduction phenomenon in the material obeys the correlated barrier hopping (CBH) model. The activation energy of the intrinsic charge carriers has been calculated by using the Arrhenius equation at different frequencies.

Giant dielectric response and relaxation behavior in (Tm + Ta) co-doped TiO2 ceramics.

Dielectric materials with huge dielectric constants are attracting attention due to the growing demand for microelectronics and high energy-storage devices. In this work, Tm + Ta co-doped TiO2 ceramics were prepared by a solid-state reaction (SSR) method, and the microstructure and dielectric behavior were investigated. A ultrahigh permittivity (εr ∼ 2.26 × 104) and very low loss (tan δ ∼ 0.011) are achieved at 1 kHz for (Tm0.5Ta0.5)0.01Ti0.99O2 ceramics. XPS analysis confirms that the high dielectric constant and low dielectric loss are attributed to the electron pinned defect dipole (EPDD) response formed by the coupling of Ti3+ and oxygen vacancies. In addition, impedance analysis and frequency dependent dielectric constant under a DC bias indicate that the presence of the internal barrier layer capacitance (IBLC) response and electrode response at low to medium frequencies (<106 Hz) also contribute significantly to the dielectric constant. The findings reported in this work provide valuable insights into the simultaneous realization of a low dielectric loss and high permittivity in Tm + Ta co-doped TiO2 ceramics and other related dielectric ceramics.

Enhanced dielectric and optical properties in Al-substituted KBiFe2O5

We report a significant effect of Aluminum (Al3+) substitution on the structural, optical and dielectric properties in brownmillerite KBiFe2O5 (KBFO) multiferroic. Polycrystalline samples of KBiFe2-xAlxO5 (x = 0, 0.2) are synthesized by citrate combustion method. From the Rietveld refinement of X-ray diffraction analysis, both the samples are found to crystalize in a monoclinic structure possessing P2/c space group. The calculated crystallite size from the Scherer’s formula is found to decrease with Al doping. The surface morphology reveals that, multiple grains of different sizes are present in all the samples and the average grain size is reduced with substitution. The optical band gap decreases from 1.739 eV to 1.715 eV with x = 0.2 of Aluminum. Furthermore, the temperature dependent Dielectric constant (ε) and dielectric loss (tan δ) of KBiFe2-xAlxO5 are investigated in a temperature range (300–773 K) at 100 Hz and 1 KHz frequency shows a substantial variation followed by a transition at around 550 K for all the samples. A comparative analysis for both the systems reveals that, for x = 0.2 of Al, an order of increase of dielectric constant appears as compared to the parent system. Additionally, the dielectric loss is also found to decrease with doping as compared to pure KBFO.

Enhanced ferroelectric and piezoelectric response by MnO2 added Bi0.5(K0.2Na0.8)0.5TiO3 ceramics

Morphotropic phased boundary (MPB) existent Bi0.5(K0.2Na0.8)0.5TiO3:xwt%MnO2 (BKNT:xMn) ceramic system is fabricated to investigate the ferroelectric and piezoelectric properties. All the ceramic samples have maintained the tetragonal (P4mm)-rhombohedral (R3c) structural duality due to MPB regional investigation of BKNT. The addition of MnO2 in BKNT has improved the multifunctional properties of the material at x ​= ​0.15. BKNT:0.15Mn ceramic has shown the maximum density of 6.98 ​g/cm3, remnant polarization (Pr) ​∼ ​32.5 ​μC/cm2, high impedance of ∼108 ​Ω, d33 of 206 ​pC/N, which are much improved properties than pure single phase BKNT and Bi0.5K0.5TiO3 ceramics. The dependence of dielectric constant (εr) on temperature suggests the relaxor behavior and the high Curie temperature (TC) ​∼ ​410 ​°C for BKNT:0.15Mn ceramic, higher than the TC ​∼ ​360 ​°C of pure BKNT ceramic. The poled ceramics have maintained the stable piezoelectric properties till 300 ​°C. The introduction of multivalence Mn has improved the multifunctional properties of the material significantly, making it a strong candidate to be utilized in actuators and sensors.

Dielectric relaxation of 1-butyl-3-methylimidazolium tetrafluoroborate/TX-100/toluene microemulsions: Structure transition, percolation mechanism, interfacial polarization and electrical properties of microdroplets

The dielectric relaxation spectra of the non-aqueous ionic liquid (IL) microemulsions composed of 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4])/p-(1,1,3,3-tetramethylbutyl)phenoxypolyoxyethyleneglycol (TX-100)/toluene were obtained, the measured frequency is between 1 MHz and 3 GHz. A unique dielectric relaxation located at 10–100 MHz was observed. The direct current (dc) conductivity data were obtained from the total dielectric loss. Near the percolation transition, weight fraction dependence of dc conductivity and static dielectric constant, frequency dependence of permittivity and loss angle all suggest that static percolation occurs in this hydrophilic IL microemulsion. Phase boundaries of IL-in-toluene (IL/O), bicontinuous (B.C.) and toluene-in-IL (O/IL) subregions were determined by the inflection points in the dependent curve of relaxation parameters varied with weight fraction. The mechanism of this dielectric relaxation is attributed to the interfacial polarization of droplets by analyzing relaxation time with Maxwell-Wagner theory. The phase parameters, which reflect the interior properties of the spherical dispersed particle, were calculated by Hanai theory. The dependence of phase parameters on the variation of sample composition was properly explained. For O/IL subregion, the continuous phase should be an IL/TX-100 binary solvent rather than the pure IL. For IL/O subregions, a certain amount of toluene was dissolved in the droplets.

Effects of Oxide Additives on the Phase Structures and Electrical Properties of SrBi4Ti4O15 High-Temperature Piezoelectric Ceramics.

In this work, SrBi4Ti4O15 (SBT) high-temperature piezoelectric ceramics with the addition of different oxides (Gd2O3, CeO2, MnO2 and Cr2O3) were fabricated by a conventional solid-state reaction route. The effects of oxide additives on the phase structures and electrical properties of the SBT ceramics were investigated. Firstly, X-ray diffraction analysis revealed that all these oxides-modified SBT ceramics prepared presented a single SrBi4Ti4O15 phase with orthorhombic symmetry and space group of Bb21m, the change in cell parameters indicated that these oxide additives had diffused into the crystalline lattice of SBT and formed solid solutions with it. The SBT ceramics with the addition of MnO2 achieved a high relative density of up to 97%. The temperature dependence of dielectric constant showed that the addition of Gd2O3 could increase the TC of SBT. At a low frequency of 100 Hz, those dielectric loss peaks appearing around 500 °C were attributed to the space-charge relaxation as an extrinsic dielectric response. The synergetic doping of CeO2 and Cr2O3 could reduce the space-charge-induced dielectric relaxation of SBT. The piezoelectricity measurement and electro-mechanical resonance analysis found that Cr2O3 can significantly enhance both d33 and kp of SBT, and produce a higher phase-angle maximum at resonance. Such an enhanced piezoelectricity was attributed to the further increased orthorhombic distortion after Ti4+ at B-site was substituted by Cr3+. Among these compositions, Sr0.92Gd0.053Bi4Ti4O15 + 0.2 wt% Cr2O3 (SGBT-Cr) presented the best electrical properties including TC = 555 °C, tan δ = 0.4%, kp = 6.35% and d33 = 28 pC/N, as well as a good thermally-stable piezoelectricity that the value of d33 was decreased by only 3.6% after being annealed at 500 °C for 4 h. Such advantages provided this material with potential applications in the high-stability piezoelectric sensors operated below 500 °C.

Effect of BaSnO3 on structural and electrical properties of lead free Na0.5Bi0.5TiO3 ceramic solid solution

A series of novel lead-free (1-x)(Na0.5Bi0.5)TiO3–xBaSnO3, (x = 0.00, 0.05, 0.10) ceramics were fabricated by solid-state air sintering route and their dielectric and microstructural properties were studied. Various experimental methods to characterize the fabricated ceramics such as PXRD, Raman spectra, SEM-EDS, UV-visible and dielectric studies. All the ceramics were crystallized by rhombohedral symmetry using PXRD and Rietveld profile refinement technique. The experimental atomic charge density distribution studies were performed and the bonding characteristics were analyzed. With increase of BSN content, the average grain size decreased and was characterized by scanning electron microscopy (SEM) technique. Energy dispersive x-ray (EDS) spectra indicate the presence elements and the diffusion of BSN into the rhombohedral phase of NBT matrix. The optical bandgap was determined by UV-Visible spectra and the values are found to be 3.05, 3.10 and 3.12 eV. The temperature dependence of dielectric constant (ε) provides evidence for dielectric anomalous behaviour in the higher doping of BSN concentration.

Photonic band structure in a two-dimensional photonic crystal with a Sierpinski triangle structure

The plane wave expansion method was used to calculate the photonic band structure of a hexagonal lattice in which the triangular GaAs scatterers have a Sierpinski structure. In triangles with lengths of less than 0.6 a, in the photonic band structure for low frequencies, the photonic band gaps appear mainly in the transverse-magnetic polarization, as shown by the results. Nevertheless, when the size of triangles increases above 0.8 a, an overlap of the photonic band gap in the transverse-electric and transverse-magnetic polarizations occurs. Hence, a complete photonic band gap is produced, where the photonic modes cannot propagate in either direction. In addition, we detected that another optimal condition for creating a complete photonic band gap is that the dielectric contrast should be greater than 12. Likewise, the pressure and temperature dependence of the GaAs dielectric constant are considered, detecting a higher frequency shift of the photonic band structure, when the temperature remains constant at 4 K and the pressure increases from 0 to 70 kbar.

Evidence of linear magnetoelectric effect in Mn4Nb2O9 single crystal

Magnetoelectric properties were carefully studied on Mn4Nb2O9 single crystal. With a clear anomaly on the temperature dependent dielectric constant at TN = 107 K, we measured the pyroelectric under different magnetic field. Magnetodielectric is proportional to H2, which is a typical sign of linear magnetoelectric effect. Polarization varies with the magnetic field in a positive correlation. All evidence shows Mn4Nb2O9 is a linear magnetoelectric material.

Behavior of the cutoff frequency in a one-dimensional photonic quasicrystal with an Octonacci sequence

In this work, we theoretically calculate the transmittance spectra for a one-dimensional photonic quasicrystal composed of a high-temperature superconductor and a semiconductor. The materials are organized based on the Octonacci sequence; in addition, we consider the dependence of dielectric constants and layer thicknesses on the applied pressure. When the temperature increases, the transmittance spectra shift toward shorter frequencies, coupled with a decrease in the cutoff frequency at different Octonacci sequence values. When the pressure increases, the layer thicknesses of the materials decrease, bringing about a shift toward higher transmittance spectra and cutoff frequencies. We also noticed that an increase in the layer thickness results in the maximization and emergence of new photonic band gaps.

A comprehensive comparative study of the performance of carbon‐ and copper‐based interconnects in ultra‐large‐scale integrated circuits

AbstractContinuous increase of transistor count in ultra‐large‐scale integrated (ULSI) circuits demands denser interconnection networks to guarantee normal operation. As the distances between adjacent interconnect lines shrinks, severe crosstalk effects appear. New interconnect materials and technologies are proposed to alleviate deteriorating crosstalk effects and maintain overall circuit performance at a desirable level. Carbon‐based materials including carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) are among promising candidate materials to replace copper in future ULSI interconnects. In this work, carbon‐based interconnects including multiwall carbon nanotubes (MWCNTs) and multilayer graphene nanoribbons (MLGNRs), both horizontal (HMLGNRs) and vertical (VMLGNRs), are compared with traditional copper interconnects in terms of crosstalk delay and noise. Due to lower surface roughness, boron nitride (BN) is considered as substrate material for carbon‐based interconnects. To obtain more accurate and reliable results, layer number dependence of dielectric constant of BN multilayers and surface roughness dependence of the resistivity of HMLGNR interconnects are considered. The role of interconnect length, line spacing, and interlayer distance (substrate thickness) in crosstalk delay and noise of coupled carbon‐ and Cu‐based interconnect lines is investigated. It is shown that VMLGNR interconnects with perfect GNR edges exhibit the least crosstalk delay while MWCNT interconnects show far less crosstalk noise than other materials.