Dielectric Loss Tangent Tanδ Research Articles

Notably enhanced dielectric response with low loss in PVDF composites filled with RuO2–BaTiO3 hybrid particles

This study delineates the process of fabricating and the results of investigating the dielectric properties of hybrid particles created through the integration of Poly(vinylidene fluoride) (PVDF) filled with RuO2 coated on BaTiO3 nanoparticles (nBT), designated as RuO2–nBT. These hybrid particles were successfully synthesized employing a simple and cost–effective solid–state reaction method. The inclusion of RuO2–nBT in the PVDF matrix engendered a notable enhancement in its dielectric properties. Notably, a RuO2–nBT fraction of 0.5 manifested a dielectric constant (ε′) of 107.4 and a dielectric loss tangent (tanδ) value of 0.062 at 30 °C and 1 kHz. These findings signify the effective role of interfacial polarization occurring between the PVDF matrix and the RuO2–nBT hybrid particles, leading to a marked improvement in dielectric attributes. Moreover, the observed low tanδ value indicates the elimination of conductive pathways, an inhibitory effect attributed to the incorporation of RuO2–nBT hybrid particles. This study underscores the promising potential of RuO2–nBT hybrid particles in fine–tuning and augmenting the dielectric properties of polymer composites, particularly in scenarios necessitating low tanδ and high ε′ values.

Enhanced dielectric properties of PVDF polymer nanocomposites: A study on gold−decorated, surface−modified multiwalled carbon nanotubes

The integration of surface-modified multiwalled carbon nanotubes (fMWCNTs) into polymer nanocomposites has been extensively studied for their potential to enhance dielectric properties. This study, however, pioneers the use of a novel hybrid filler comprising fMWCNTs coated with metal nanoparticles, specifically aimed at augmenting the dielectric performance of polymers. In our research, poly(vinylidene fluoride) (PVDF) nanocomposite films were synthesized using fMWCNTs with a diameter of ∼6–9 nm and a length of 5 μm, adorned with gold nanoparticles (nAu) of ∼5.4 ± 0.9 nm via an adapted Turkevich method. Comprehensive analyses were conducted on nAu−fMWCNTs hybrid powder and their nanocomposites in PVDF with varying filler concentrations, confirming the formation of nAu−fMWCNTs with a weight ratio of 1.1 : 98.9. Three−phase percolative nanocomposites were produced by dispersing the hybrid filler in N,N−dimethylformamide, facilitated by interactions between the negative charge of nAu−fMWCNTs (zeta potential of ∼ −40.43 ± 0.46 mV) and polar phases of PVDF. This was verified through zeta potential and Fourier−transform infrared spectroscopy analyses. The dielectric permittivity (ε′) of the nanocomposites significantly increased from 17.8 to 524.8 (at 1 kHz) with filler loadings from 0.005 to 0.01 vol%, while the dielectric loss tangent (tanδ) showed a minor increase from 0.05 to 1.18. These enhancements are attributed to the elevated permittivity of nAu−fMWCNTs hybrid powder, PVDF's transition to the β−phase, and interfacial polarization effects. The restrained growth of nAu on fMWCNTs and the inhibition of conductive pathways in the polymer matrix contributed to the low tanδ values.

Dielectric properties of PANI‐PEG nanocomposites filled with silica media for antistatic applications

AbstractThe dielectric investigations of porous synthetic silica gel modified with polyaniline (PANI) and polyethylene glycol (PEG) polyblend at various concentrations are demonstrated in this paper. By using the chemical oxidative process to embed polyaniline (PANI) and polyethylene glycol (PEG) into a silica matrix, conducting gel nanocomposites were synthesized. For various dopant concentrations, the dielectric permittivity (ε′), D.C. conductivity (σdc), loss tangent (tanδ) and dielectric loss (ε″) were investigated. The samples were characterized using differential thermal analysis/thermogravimetric analysis, Fourier transform infrared spectroscopy and high‐resolution transmission electron microscopy. Depending on the co‐blend content, PANI‐PEG modified silica structures produce nanoparticles ranging in size from 9.9 to 48.1 nm. The variation of DC conductivity (σdc) with PANI/PEG content shows Maxwell‐Wagner Sillars (MWS) effect confirming the role of the conjugation and the structural order.

Investigation of Terp-Pyr/p-Si diode using complex impedance spectroscopy depending on measurement temperatures and frequencies

A unique Al/Terp-Pyr/p-Si/Al diode structure that has not before been presented was introduced in this paper. Utilizing capacitance-conductance-frequency (C-G-f) characteristics in the frequency range of 20 Hz− 1.5 MHz for four temperatures of 300 K, 325 K, 350 K, and 375 K, admittance analysis was carried out to disclose the impedance and dielectric properties of the diode. The appearance of interface states at the Terp-Pyr/p-Si interface leads to an increase in capacitance values at low frequencies. Using complex impedance spectroscopy, the impedance characteristics of the Al/ Terp-Pyr/p-Si/Al Schottky diode were examined. The fabricated diode’s dielectric, modulus, and ac conductivity properties were investigated in the same frequency and temperature range. It has been revealed that while ϵ′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\epsilon }^{{\\prime }}$$\\end{document} decreases up to high frequencies for all temperatures, it grows with temperature in the low-frequency zone. It becomes apparent that while the real component (M’) of modulus grows for all temperatures from low to high frequencies, it decreases at high frequencies as temperature rises. remarkably adjustable temperature, voltage, and frequency tuning of the dielectric constants (ϵ′,ϵ′′)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$({\\epsilon }^{{\\prime }},{{\\epsilon }^{{\\prime }}}^{{\\prime }})$$\\end{document} and dielectric loss tangent (tanδ). Additionally, the equivalent circuit of the Al/ Terp-Pyr/p-Si/Al Schottky diode and Cole-Cole diagrams were explored.

Optical and dielectric behavior of Al/CrO3/p-Si device

In this study, dielectric chromium trioxide (CrO3) metal oxide film layer was prepared by the spin coating method on Si wafer. It was estimated the optical parameters like the absorption coefficient (α), refractive index (n), extinction coefficient (k), complex dielectric permittivity and optical conductivity (σopt) as a function of the wavelength by means of the transmittance (T) and reflectance (R) data. In addition, the dielectric behavior of Al/CrO3/p-Si device was analyzed in a large frequency region (10 kHz-1 MHz) using admittance (Y = G + iωC) spectroscopy. Dielectric characteristics including dielectric constant (ε′), dielectric loss (ε"), and loss tangent (tanδ) showed high values at small frequency part and low values at huge frequency part. Aside from that, the value of AC electrical conductivity (σac) rises with the rise in frequency as well. The results show the prepared film and device may be used in photovoltaic and electronic device applications.

Effect of the titanium-dioxide addition on the structural, dielectric, and mechanical properties of different cement-based mortars with corundum aggregate

The primary objective of this study was to look into the role of titanium dioxide in the production of corundum-based mortars, with a focus on finding the optimal mortar composition for achieving improved mechanical and dielectric performances. Changes in the mix design (different binders, different additive dosages), as well as their effects on the hydration pathway, chemical bonds, phase modifications, and microstructure, were examined. These findings were then correlated to the designed mortars' mechanical strengths and dielectric properties. Experimental mortars were produced with binders made from ordinary Portland cement, high alumina cement, and their mixtures, and corundum as aggregate. Titanium dioxide was employed as an additive (3 and 5wt.%). Nine different mortars were submitted for comprehensive mineralogical and microstructural characterization upon curing and solidification. The compressive and flexural strengths were monitored throughout the 28-day period. The dielectric constant (εr), dielectric loss tangent (tanδ), and electrical resistivity (ρ) were measured over a frequency range of 100Hz to 1MHz. XRD analysis highlighted the appearance of mayenite as a dielectric-prone phase in the samples doped with titanium dioxide. Differential thermal analysis and FTIR spectroscopy identified a higher amount of extra-low crystalline phase in OPC and HAC mortars with TiO2 addition, which accelerated hydration mechanisms, created a surplus of hydration products and made a more compact cement matrix. TiO2 added in 3wt.% amount led to higher mechanical strengths in OPC-based mortars, while it improved the dielectric properties of HAC mortars.

Synthesis, characterization and dielectric relaxation studies of graphene quantum dots prepared by hydrothermal treatment method

Zero dimensional graphene quantum dots (GQDs) exhibit fascinating chemical and physical properties discovered by Pan et al., in 2010, due to the quantum confinement and edge effect. GQDs have been synthesized by hydrothermal treatment method from graphite powder as low cost, easy process, and large amount with high production yield. The functional groups of GQDs on the surface sites of carbon atoms have been studied through Fourier transform infrared spectroscopy (FTIR) analysis. X-ray diffraction (XRD) pattern of GQDs shows the broad diffraction at 2 θ = 24.47 ° with 0.36 nm an interlayer distance confirming the formation of the GQDs. Raman analysis reveals that GQDs show both D and G bands mostly the armchair edges. UV–visible spectra show absorption peak at 287 and 330 nm credited to π → π * and n → π * transitions due to the presence of conjugated carbon–carbon bonds and carbonyl groups. The particle size of GQDs is found below 5 nm from high- resolution transmission electron microscopy (HR-TEM) image. Scanning electron microscopy shows the surface morphology of GQDs are crumpled and aggregated thin sheets. Dielectric properties of synthesized GQDs have been studied in the range frequency between 0.01 and 105 Hz at different temperatures (25, 50, 75, and 100 °C). The dielectric relaxation mechanism is explained in the framework of dielectric loss tangent (tanδ), permittivity and electrical conductivity. The dielectric loss tangent increases with frequency and maximum peak decreases with frequency at all different temperatures due to present of polar groups in GQDs. Dielectric permittivity decreases with frequency at all different temperatures due to charge orientation and rotation of dipole moments. The electrical conductivity increases with frequency at all different temperature due to the GQDs is highly conductive nature. So synthesized GQDs can be used in electrical and electronic materials.

Dielectric analysis of surface modified nano-graphite: effects of frequency and thickness

The nano-graphite (NG) and acid modified nano-graphite (ANG) have been synthesized from graphite powder via mixture of strong acid (sulphuric acid and nitric acid) respectively by a soft chemistry route involving microwave, ultrasonic method and characterized by high-resolution electron microscopy (HR-TEM), scanning electron microscopy (SEM), fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), clearly demonstrated the successful synthesis of acid modified NG. SEM images confirmed the surface morphology of NG, and ANG and HR-TEM study shows the nanoparticles size of NG and ANG. FTIR data confirmed the presence of acid functional groups on the surface of synthesized NG powder. XRD data of NG and ANG shows that 2θ is at 26.43° and 0.336 nm is an interlayer distance (d). NG and ANG pellets have been prepared for their dielectric analysis with frequency for different thickness. The dielectric loss tangent (tanδ) spectra show relaxation peak with frequency and peak shifts due to presence of polar groups in the ANG. The capacitance values of NG and ANG decrease with frequency and increase with thicknesses due to the capacitive nature of nanoparticles. The dielectric permittivity decreases with frequency and increases with thickness due to the charge orientation and dipole moment change of functional groups of synthesized NG, and ANG. The electrical conductivity of NG and ANG nanoparticles increases with frequency and thickness of NG and ANG pellets due to the conductive nature. Electrical conductivity and dielectric permittivity of NG and ANG are found to highly rely on thickness, according to the dielectric evaluation.

Structural, dielectric and magnetic study of double perovskite La2CoMnO6

Polycrystalline double perovskite La2CoMnO6 sample was prepared via solid state reaction route and its structural, dielectric and magnetic properties were investigated. XRD confirmed the phase formation without any impurity. Rietveld refinement analysis suggested the presence of monoclinic (P21/n, ordered) as well as rhombohedral and orthorhombic (R3c &Pbnm, disordered) structures. Microstructural analysis using FESEM confirmed that average grain size lies in micrometer range. Dielectric constant (log ε′) and loss tangent (tanδ) both exhibited large values at lower frequencies as well as in higher temperature range. Nyquist impedance plot proposed NTCR (negative temperature coefficient of resistance) nature of double perovskite sample. DC conductivity showed increasing trend with increase in temperature and also, the conductivity is of the order of 10−2 S/m, which represent semiconducting behavior of prepared sample. Also, the analysis suggested the co-existence of thermal activation (TA), small polaron hopping (SPH) and variable range hopping (VRH) conduction mechanisms. Temperature dependent magnetic measurements (M-T) suggested that sample exhibit single magnetic transition at 226 K. Field dependent magnetic measurements (M-H) confirmed the ferromagnetic nature of the prepared sample. M-H loop is not well saturated even at 60 kOe which suggested the presence of anti-site disorder. Multi-domain magnetic structure of the prepared sample suggests its suitability for memory device applications.

Improvement of dielectric properties and thermal stability of CaCu3Ti4.2O12 ceramics for X8R type capacitors via Co2+ doping

Work on giant dielectric CaCu3Ti4O12 (CCTO) ceramics has been continuously ongoing to obtain materials with a high dielectric constant (ε') and low dielectric loss tangent (tanδ) with both values stable over a wide temperature range. Various methods have been used to modify the materials, such as doping and co-doping with different transition metals at Ca or Cu sites, molar variation of metals (Cu, Ca and Ti), including altering in the methods and conditions of ceramic preparation. In general, the most common problem found in this type of research is that increasing ε' also increases tanδ. Thus, in this work, a one-step polymer pyrolysis (PP) procedure was used to obtain Co2+-doped CaCu3-xCoxTi4.2O12 (x = 0.00, 0.03, 0.05, and 0.07) powders. Then, all powders were sintered to obtain ceramics using two different sintering conditions, 1050 °C for 10 h and 1080 °C for 5 h. The influence of Co2+ ions and sintering conditions on the microstructure, dielectric properties and thermal stability of CaCu3Ti4.2O12 ceramics was investigated. Substitution of Co2+ ions at Cu sites can reduce tanδ values and increase ε' in samples with x = 0.03 and 0.05. However, the tanδ and ε' values were concurrently reduced for x = 0.07. Remarkably, a ceramic with x = 0.07 sintered at 1080 °C for 5 h exhibited very low tanδ(∼0.009) and colossal ε' (∼11551) at 1 kHz and 30 °C, over a broad temperature range (−60 to 150 °C), with stability of Δε' ≤ ±15 %. This ceramic is a suggested candidate material for X8R capacitors. Moreover, increasing the Co2+ doping level could significantly raise the nonlinear coefficient (α) of the ceramics from ∼ 3.48 to 34.30. Additionally, the very high Eb values of ceramics with x = 0.07 sintered at 1050 °C for 10 h and 1080 °C for 5 h were significantly increased by ∼26.34 and 17.45 times, respectively, compared to an undoped ceramic. A widened temperature range where Δε' ≤ ±15 % and tanδ < 0.05 in all ceramics with increasing Co2+ concentration is likely a result of increased grain boundary resistance.

Structural, morphological, dielectric properties, impedance spectroscopy and electrical modulus of sintered Al6Si2O13–Mg2Al4Si5O18 composite for electronic applications

In this study, the sol-gel method of low-temperature synthesis was utilized to create mullite/cordierite precursor powder. The materials (TEOS) Si(C2H5O)4, Al(NO3)3.9H2O and Mg(NO3)2 were utilized as source of SiO2, Al2O3, and MgO oxides respectively in order to create mullite/cordierite precursor gel with various concentrations and designations (MC00, MC10, MC20, MC30, MC40, and MC50). Crystalline phases were seen and described using scanning electron microscopy (SEM) and powder X-ray diffraction (XRD). After the powder was formed at 1600 °C for an hour, its sintering was looked at. For all mixes, as the cordierite concentration rises, the bulk density rises and the open porosity decreases. The existence of a vitreous phase may be the cause of the rise in bulk density and reduction in open porosity seen with rising temperatures.The dielectric characteristics of the samples have been examined at room temperature; the relative dielectric constant (εr), loss tangent (tanδ), and dielectric characteristics were assessed at frequencies of 0.1 Hz, 1, 10, 100, and 1000 kHz. At 1 kHz, the relative dielectric constant values are closest to those of mullite (εr = ∼5 to ∼ 6), and c at 1 kHz. On the other hand, the lowest dielectric losses were observed (tanδ from ∼0.06 to ∼ 0.04). The Electrical properties, electrical resistivity, AC conductivity, impedance spectroscopy, electrical modulus, and the relative quality factor (QF) of pure mullite and mullite/cordierite composite sintered at 1600 °C for 1 h (MCyy) samples were investigated as a function of cordierite content at varied frequencies (0.01 Hz, 1 kHz, 100 kHz, and 1000 kHz). The hardness (HV) and coefficient of thermal expansion (CTE) of the composite material that underwent sintering at a temperature of 1600 °C were determined by the use of a hardness tester and a dilatometer, respectively. The rise in temperature, coupled with an equal quantity of cordierite, resulted in an elevation of the apparent density and a reduction in the open porosity. In the case of the specimen subjected to sintering at a temperature of 1600 °C, the introduction of cordierite content in the range of 0–40% resulted in an observed rise in HV value from 9.15 to 12.99 GPa. However, a further increase in cordierite content to 50% led to a decrease in HV value to 10.99 GPa. Nevertheless, the CTE value throughout the temperature range of 50–1200 °C exhibited a consistent decline, ranging from 5.37 × 10−6 to 2.32 × 10−6 K−1. Notably, the composite material consisting of 50 wt% cordierite had elevated HV and the most minimal CTE value.

Tunable dielectric characteristics ofTPU/PPycomposite film and foamyfilm with low loss over a wide range of temperature

AbstractIn the present research, thermoplastic polyurethane/polypyrrole (TPU/PPy) dielectric composites film and the lightweight foamyfilm are fabricated using the most simplified solvent casting and modified phase separation water immersion techniques, respectively. The establishment of chemical interaction and morphological investigations of the fabricated systems are analyzed by Raman spectroscopy and field emission scanning electron microscope (FESEM), respectively. Various dielectric properties, together with complex impedance, are determined over a wide range of frequencies (1 Hz–1 MHz) and temperatures (25°C–120°C). Most interestingly, above 30 Hz frequency, a significantly low value (&lt;0.1) dielectric loss tangent (tanδ) is obtained at ambient temperature. A 90:10 foamyfilm exhibits a dielectric permittivity (ε') and tanδof 236 and 0.05 at 50 Hz frequency, respectively. Both 90:10 film and foamyfilm systems exhibit a significantly increasing trend ofε′ as well as low tanδwith an increase in temperature over a wide range of frequencies. The thermogravimetric analysis (TGA) results of the 90:10 film and foamyfilm indicate the superior thermal stability of the 90:10 foamyfilm system. Based on the obtained low dielectric loss, the fabricated dielectric film, and foamyfilm can be employed in energy storage and high‐temperature sensing applications.

Structural and dielectric properties of GdFeAsO ceramic material

The iron-based ceramic GdFeAsO has been prepared by the solid-state reaction method. To identify the ceramic and its multiple applications we have performed structural, micro structural and electrical characterizations of the sample. The crystalline size and structure are calculated at room temperature using the X-ray Diffraction (XRD) technique. Tetragonal structure has been ensured from XRD. The lattice strain of the crystal is obtained using W.H. Plot, which ensured the structural stability of the crystal. The field emission scanning electron microscopy (FESEM) technique is used to study the surface morphology of the sample. Polycrystalline grains having spherical and cylindrical sizes of ranges 1-3 micrometer are obtained. The observed prominent peaks at 107.1cm−1,150.4cm−1,216.6cm−1,296.6cm−1,344.6cm−1 and 440.37cm−1 in the Raman spectra of the sample, are for the cubic phase of the Gd2O3 in the GdFeAsO compound material. The peak at 623.0cm−1 corresponds to α-Fe2O3 in the spectra reveals the presence of impurity oxide phases. The broad peaks in the Differential Scanning Calorimetry (DSC) graph at about (290°C) and (600°C) reveals the initiation of slow crystallization of the sample within the given temperature range. The dielectric properties such as the dielectric constant (εr) and loss tangent (tanδ) of the sample have been studied at different temperatures and frequencies with LCR meter. The high value of dielectric constants is seen to exist in the materials. There are two dielectric anomalies that are observed at lower and higher temperature region. The magnetic measurement has been performed by using Vibrating Sample Magnetometer (VSM) at room temperature and showed the non linearity in the magnetization versus field curve.

Synthesis and investigation of structural, elastic, and electrical properties of cobalt and magnesium substituted Ni–Zn spinel ferrite nanoparticles

The sol–gel auto-combustion approach was used to create Ni0.4M0.2Zn0.4Fe2O4 (M = Ni2+, Mg2+, and Co2+) nanoparticles. X-ray diffraction (XRD), Fourier transform infrared spectroscopy, energy dispersive x-ray spectroscopy (EDS), and an inductance–capacitance–resistance (LCR) meter were used to analyse the samples’ structural, elastic, and electrical properties. In all samples, the XRD patterns obtained indicated the formation of a monophasic cubic spinel structure with no identifiable impurity phase, which was supported by EDS investigations. The introduction of substituting ions, specifically Mg2+ and Co2+, into Ni–Zn ferrite nanoparticles results in an increase in the lattice parameter. The lattice parameter for Ni–Zn is 8.377 Å, while for the substituted nanoparticles it is 8.389 and 8.388 Å for Mg2+ and Co2+ respectively. Additionally, the crystallite size of the substituted nanoparticles increases to 46.57 nm from 40.75 nm for Ni–Zn. However, the x-ray density of the substituted nanoparticles decreases to 5.180 and 5.337 g cm−3 for Mg2+ and Co2+ respectively, from 5.358 g cm−3 for Ni–Zn. The elastic parameters, such as the Young’s modulus, Debye temperature, bulk modulus, and rigidity modulus, were calculated. The good elastic characteristics of Ni–Zn ferrite were confirmed and may be explained by the lower lattice parameter values and smaller crystallite sizes. Temperature and frequency effects on dielectric behaviour and AC electrical conductivity (σ AC) were investigated. At ambient temperature, the dielectric characteristics, specifically the dielectric constant (ϵ′) and loss tangent (tanδ), were computed over a frequency range of 100–2 MHz. The compositions display normal dielectric properties, which are attributed to the interfacial polarisation following the Maxwell–Wagner model. The AC conductivity of nanoparticles was shown to decrease when Mg2+ and Co2+ were substituted into Ni–Zn ferrite. Furthermore, the AC conductivity diminishes with decreasing frequency, which is a sign of ionic conductivity. There was a direct relationship between the temperature and the values of ϵ′, tanδ, and σ AC for different ions.

First-principles calculations to investigate the dielectric and optical anisotropy in two-dimensional monolayer calcium and magnesium difluorides in the vacuum ultraviolet

Anisotropic dielectric and optical properties of two-dimensional (2D) calcium and magnesium difluorides were investigated in the vacuum ultraviolet (VUV) region of the electromagnetic spectrum (EM) using the first principles density functional theory (DFT). The anisotropy between the in-plane and out-of-plane directions shows that these materials are uniaxial, exhibiting optical and dielectric anisotropy. The optical functions of these anisotropic materials-optical absorption, photoconductivity, refractive index, reflection and extinction coefficients, and electron energy loss (EEL) spectra-are calculated in the framework of DFT. The low refractive index values and relatively small extinction coefficient make these materials alternative low-index 2D materials for the long wavelengths in the VUV region of the EM spectrum. The reflection and transmission spectra indicate the antireflective property of these materials. The calculated EEL function shows less energy loss of fast-traveling electrons in the material's medium. The maxima in the EEL spectrum are the main feature of plasma oscillations. The dissipation in the incident light radiation energy propagating through the dielectric medium is estimated with the dielectric loss tangent (tanδ). The magnesium difluoride is identified as a less dielectric loss medium than calcium difluoride in the VUV region. The present results suggest that these 2D materials are promising in low refractive index, high reflective, and antireflective coating materials in optoelectronic device applications. Also, electronic studies revealed that these are excellent materials for gate insulators in field-effect transistors based on 2D electronic materials.

Exploring the coupling effect of ferromagnetic, Co0.8Zn0.2Fe2O4 with the ferroelectric, Ba0.5La0.5TiO3 at different concentrations in composite multiferroics

The solid-state reaction method is followed to fabricate multiferroic particulate composites, (1-x) Ba0.5La0.5TiO3 + (x) Co0.8Zn0.2Fe2O4 (x = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9, 1.0). X-ray diffraction patterns reflect the coexistence of the constituent phases in the composites after 4 h of sintering at 1200 °C. Cubic structures of both ferroelectric and ferrite phases confirmed from Rietveld refinement are distinctively dominant. The Fourier Transform Infrared (FTIR) spectrum confirms the characteristic vibration bonds of Co-ferrite, Zn-ferrite, and Ti-O. A slight variation of lattice parameters is observed with the increasing ferrite concentration. Bulk density reveals the inverse behavior of theoretical density. The obtained average grain size varies from 1.308 µm to 3.046 µm. All the composites have good ferromagnetic properties confirmed by hysteresis loops. The coercive field at x = 0.5 is 297.98 Oe, dramatically higher than other concentrations. The real part of permeability (μi′) gradually increases with increasing ferrite content as per the sum rule of the mixture. To investigate the electric properties of the samples, the dielectric constant (ε′) and loss tangent (tanδ) are measured in the frequency range of 100 Hz to 100 MHz. The dielectric constant (ε′) decreases at first and after x = 0.3, it begins to increase with further addition of the ferrite phase. The maximum dielectric constant (ε′) is 1092.08 at x = 0.9. The dielectric constant (ε′) and loss tangent (tanδ) display Maxwell-Wagner interfacial polarization and reduce from low to high frequency. All of the samples appear to be highly resistive indicating the reduction of leakage current. The dielectric constant (ε′) and resistivity show the opposite trend. P-E hysteresis loops indicate para-electric to ferroelectric transition.

Ultrahigh thermal stability of dielectric permittivity in 0.6Bi(Mg1/2Ti1/2)O3–0.4Ba0.8Ca0.2(Ti0.875Nb0.125)O3

0.6Bi(Mg1/2Ti1/2)O3–0.4Ba0.8Ca0.2(Nb0.125Ti0.875)O3 ceramics with a pseudo-cubic structure and re-entrant dipole glass behavior have been investigated via x-ray diffraction and dielectric permittivity–temperature spectra. It shows excellent dielectric–temperature stability with small variations of dielectric permittivity (±5%, 420–802 K) and dielectric loss tangent (tanδ &amp;lt; 2.5%, 441–647 K) in a wide temperature range. Three dielectric anomalies are observed from 290 to 1050 K. The low-temperature, weakly coupled re-entrant relaxor behavior was described using the Vogel–Fulcher law and the new glass model. The mid- and high-temperature dielectric anomalies are characterized by isothermal impedance and electrical modulus. The activation energy of both dielectric relaxation and conductivity follows the Arrhenius law in the temperature ranges of 633–753 and 833–973 K, respectively. The ultrahigh thermal stability of dielectric permittivity is attributed to the weak coupling of polar clusters, the formation of diffuse phase transition, and the local phase transition of calcium-containing perovskite. The results provide new insights into the defects behavior and the modification way of re-entrant relaxor behavior.

Origin of frequency and voltage dependent negative dielectric properties in the Al/p-Si Schottky diodes with (Cd0.3Zn0.7O) interfacial layer in the wide range of frequency and voltage

The real and imaginary parts of complex-dielectric (ε′, ε'') and electric-modulus (M′, M″), dielectric loss tangent (tanδ), and conductivity (σ) values of Al/(Cd0.3Zn0.7O)/p-Si Schottky Diode (SD) were obtained from capacitance/conductance vs. voltage/frequency (C/G-V-f) plots. Negative dielectric (ND) was observed under 50 kHz at about 3.5 V and the increase in the ε'' results from a drop in ND with increasing voltage, also known as inductive behavior. The rise in σac at high frequencies causes the eddy-current to grow, which in turn causes the ε” or tanδ to increase. While the relaxation process causes the value of M′ to decrease with increasing voltage, M″-V graphs reveal a peak at roughly 0.0V for each frequency. The obtained value of ε′ for Al/(Cd0.3Zn0.7O)/p-Si at 500 Hz is about 25 times higher than those using traditional SiO2 as an interfacial layer, and so it can be successfully used for more charge or energy storage.

A network of hydrogen bonds in the lattice of heavy atoms of single crystals of the KDP group: quantum nature of dipole interactions

In the work presented, the distinctive features of temperature behavior of dielectric permittivity ε, dielectric loss tangent tanδ and pyroelectric coefficient γ of classical ferroelectric KDP and crystals of its family, which have a network of strong OH…O hydrogen bonds, are discussed. Particular attention is focused on the evidence of quantum-chemical interactions in network of hydrogen bonds in the matrix of heavy nuclei.

The effects of microstructure on the dielectric, ferroelectric and impedance properties of 0.5Ba(Zr0·2Ti0.8)O3-0.5(Ba0·7Ca0.3)TiO3 ceramics

0.5Ba(Zr0·2Ti0.8)O3-0.5(Ba0·7Ca0.3)TiO3 (BCZT) ceramics with average grain sizes from 3.26 to 18.15 μm were synthesized by adjusting the sintering temperature in the solid-state-reaction process. The effects of various grain sizes on the dielectric, ferroelectric, and impedance properties of BCZT ceramics were studied, and the liquid phase in the grain boundary was observed. When a solid solution exists in the grain boundary, both the maximum dielectric constant εmax and loss tangent tanδ are affected by the competition between the grain size effect and liquid phase in the grain boundary morphology. The energy storage efficiency increases and the energy density decreases owing to the improved compactness and hindered grain boundary conduction. The contributions of grain and grain boundary are demonstrated by two arc curves in impedance spectra. The effects of different grain boundary morphologies on the electrical properties of BCZT ceramics were quantitatively obtained by high-temperature impedance patterns and DC conductivity fluctuations. These results help to prepare different targeted functional ceramics by designing specific microstructures.