Low-frequency Dielectric Properties Research Articles

Critical Model Insight into Broadband Dielectric Properties of Neopentyl Glycol (NPG).

This report presents the low-frequency (LF), static, and dynamic dielectric properties of neopentyl glycol (NPG), an orientationally disordered crystal (ODIC)-forming material important for the barocaloric effect applications. High-resolution tests were carried out for 173K<T<440K, in liquid, ODIC, and solid crystal phases. The support of the innovative distortion-sensitive analysis revealed a set of novel characterizations important for NPG and any ODIC-forming material. First, the dielectric constant in the liquid and ODIC phase follows the Mossotti Catastrophe-like pattern, linked to the Clausius-Mossotti local field. It challenges the heuristic paradigm forbidding such behavior for dipolar liquid dielectrics. For DC electric conductivity, the prevalence of the 'critical and activated' scaling relation is evidenced. It indicates that commonly applied VFT scaling might have only an effective parameterization meaning. The discussion of dielectric behavior in the low-frequency (LF) domain is worth stressing. It is significant for applications but hardly discussed due to the cognitive gap, making an analysis puzzling. For the contribution to the real part of dielectric permittivity in the LF domain, associated with translational processes, exponential changes in the liquid phase and hyperbolic changes in the ODIC phase are evidenced. The novelty also constitutes tgδ temperature dependence, related to energy dissipation. The results presented also reveal the strong postfreezing/pre-melting-type effects on the solid crystal side of the strongly discontinuous ODIC-solid crystal transition. So far, such a phenomenon has been observed only for the liquid-solid crystal melting transition. The discussion of a possible universal picture of the behavior in the liquid phase of liquid crystalline materials and in the liquid and ODIC phases of NPG is particularly worth stressing.

Structural, magnetic, low and high frequency dielectric properties of Al-substituted M-type SrCe hexaferrites synthesized in the presence of tecomastans (yellow bell) leaves extract

This paper represents a study of the effect of Al-substitutions on structural, magnetic, and dielectric properties of Sr0·8Ce0·2Fe12-xAlxO19 (x = 0.00, 0.25, 0.50, 0.75 and 1.00) ferrites synthesized in presence of yellow bell leaves extract. All samples were synthesized using the sol-gel combustion technique with the influence of green synthesis by using leaves of Tecomastans (yellow bell) plant. These samples were preheated at 550 °C for 4 h and finally calcinated at 1150 °C for 6h. These samples were characterized using XRD, FTIR spectroscopy, SEM, VSM, LCR measurements, and VNA measurements. XRD analysis confirm the formation of a magnetoplumbite M-phase (hexagonal) with a minor impurity phase of CeO2 in all samples. Lattice parameters a and c are obtained from rietveld refinement, which are found in the range from 5.859 Å to 5.883 Å, and 22.96 Å to 23.05 Å respectively. FTIR spectra confirm the absence of organic compounds and the presence of an absorption band in the fingerprint region, which are linked to the stretching of the metal-oxygen bond at the octahedral and tetrahedral sites. The surface morphology of these samples is analyzed using SEM images. Grains with hexagonal plate shapes were observed in each sample. The average grain size varies in the range of 0.565 μm–1.455 μm. EDS data confirms the presence of desired elements in the respective sample. VSM analysis shows hard magnetic behavior in all samples. Magnetic parameters were found in the range, Ms: 36.281–43.397 emu/g, Mr: 12.297–19.841 emu/g, Hc: 2.0987–3.814 kOe. In low-frequency (20 Hz-2 MHz) dielectric measurements, the dielectric constant is high at low frequencies, which rapidly falls as frequency increases. Loss tangent curve shows a relaxation peak for each sample above 200 kHz. AC conductivity is very low in the order of 10−5 S/m in plateau region below 2 kHz, which increases as frequency increases. Cole-Cole plot suggests the effect of grain boundary contribution is higher in non-substituted sample compared to Al-substituted samples. In high-frequency (0.2 GHz–20 GHz) measurements, the dielectric constant remains almost constant. These values are found in the range 5–7.5. Low loss tangent of 0–0.16 were observed in every sample in this frequency domain, with AC conductivity of the order of 10−2 S/m.

LOW FREQUENCY DIELECTRIC PROPERTIES OF AGRICULTURE SOIL CONTAMINATED BY POTASH CHEMICAL FERTILIZERS

Present paper investigates the impact of potash (KCl) contamination on the low-frequency (100 Hz - 1 MHz) dielectric properties of agricultural soil from the western Dhule district, India. Soil samples were spiked with varied KCl concentrations (0, 5, 10, and 20 mg) and analyzed using an LCR meter to measure dielectric constant, impedance, dielectric loss, and admittance. Results demonstrate a proportional increase in dielectric constant with increasing KCl concentration, indicating enhanced polarization within the soil matrix. Conversely, impedance and admittance displayed opposite trends, with impedance decreasing and admittance increasing as KCl concentration rose. Dielectric loss also exhibited a positive correlation with KCl content. This comprehensive investigation sheds light on the dynamic interplay between soil composition and dielectric properties under varying potash concentrations, contributing valuable insights to agricultural and environmental sciences.

The Dominance of Pretransitional Effects in Liquid Crystal-Based Nanocolloids: Nematogenic 4-methoxybenzylidene-4'-butylaniline with Transverse Permanent Dipole Moment and BaTiO3 Nanoparticles.

The report presents static, low-frequency, and dynamic dielectric properties in the isotropic liquid, nematic, and solid phases of MBBA and related nanocolloids with paraelectric BaTiO3 nanoparticles (spherical, d = 50 nm). MBBA (4-methoxybenzylidene-4'-butylaniline) is a liquid crystalline compound with a permanent dipole moment transverse to the long molecular axis. The distortions-sensitive analysis of the dielectric constant revealed its hidden pretransitional anomaly, strongly influenced by the addition of nanoparticles. The evolution of the dielectric constant in the nematic phase shows the split into two regions, with the crossover coinciding with the standard melting temperature. The 'universal' exponential-type behavior of the low-frequency contribution to the real part of the dielectric permittivity is found. The critical-like pretransitional behavior in the solid phase is also evidenced. This is explained by linking the Lipovsky model to the Mossotti catastrophe concept under quasi-negative pressure conditions. The explicit preference for the 'critical-like' evolution of the apparent activation enthalpy is worth stressing for dynamics. Finally, the long-range, 'critical-like' behavior of the dissipation factor (D = tgδ), covering the isotropic liquid and nematic phases, is shown.

Tuning low frequency dielectric properties of flexible ternary polymer blend film reinforced with bio- ionic liquid for the application in green electronics

Biofriendly conducting polymeric blends and composites exhibiting high dielectric constant and dielectric loss are promising for applications as sensors, actuators, microwave absorbing materials, fuel cells and biomedical applications. A great deal of work is reported on using fillers such as conductive nanomaterials, bio ceramics, carbon nanotubes, graphene etc in blends of Polyvinylchloride, Polyvinylpyrrolidone, Polymethylmethacrylate, Polyvinyl alcohol with conducting polymer Polypyrrole, Polyaniline for enhancing their conductivities, tailoring dielectric and electrical, thermal and surface properties of such polymeric materials. However, appropriate dispersion of such fillers in polymeric matrices remains technically challenging. In this regard, bio-ionic liquids have emerged as a novel class of materials and their combination with specific polymer blends opens the possibility to develop smart novel materials with different morphologies. Present work aims to explore the low frequency dielectric properties exhibited by free standing, flexible, biofriendly/biodegradable ternary polymer blend film of Polyvinylchloride-Polyvinylpyrrolidone-Polypyrrole reinforced with choline acetate. The detailed analysis of low frequency dielectric properties authenticates that addition of choline acetate result in modifying the dielectric properties of ternary polymer blend film.. The harmlessness of these films was confirmed from disk diffusion test indicating their benign nature towards (Escherichia coli) (CFT073) and (Bacillus subtilis). Therefore, the developed films can potentially be used for various scale multifunctional dielectric and electrical applications working in close contact with living matter, green electronics and various health monitoring systems.

Non-Destructive Detection of Golden Passion Fruit Quality Based on Dielectric Characteristics

This study pioneered a non-destructive testing approach to evaluating the physicochemical properties of golden passion fruit by developing a platform to analyze the fruit’s electrical characteristics. By using dielectric properties, the method accurately predicted the soluble solids content (SSC), Acidity and pulp percentage (PP) in passion fruit. The investigation entailed measuring the relative dielectric constant (ε′) and dielectric loss factor (ε″) for 192 samples across a spectrum of 34 frequencies from 0.05 to 100 kHz. The analysis revealed that with increasing frequency and fruit maturity, both ε′ and ε″ showed a declining trend. Moreover, there was a discernible correlation between the fruit’s physicochemical indicators and dielectric properties. In refining the dataset, 12 outliers were removed using the Local Outlier Factor (LOF) algorithm. The study employed various advanced feature extraction techniques, including Recursive Feature Elimination with Cross-Validation (RFECV), Permutation Importance based on Random Forest Regression (PI-RF), Permutation Importance based on Linear Regression (PI-LR) and Genetic Algorithm (GA). All the variables and the selected variables after screening were used as inputs to build Extreme Gradient Boosting (XGBoost) and Categorical Boosting (Cat-Boost) models to predict the SSC, Acidity and PP in passion fruit. The results indicate that the PI-RF-XGBoost model demonstrated superior performance in predicting both the SSC (R2 = 0.9240, RMSE = 0.2595) and the PP (R2 = 0.9092, RMSE = 0.0014) of passion fruit. Meanwhile, the GA-CatBoost model exhibited the best performance in predicting Acidity (R2 = 0.9471, RMSE = 0.1237). In addition, for the well-performing algorithms, the selected features are mainly concentrated within the frequency range of 0.05–6 kHz, which is consistent with the frequency range highly correlated with the dielectric properties and quality indicators. It is feasible to predict the quality indicators of fruit by detecting their low-frequency dielectric properties. This research offers significant insights and a valuable reference for non-destructive testing methods in assessing the quality of golden passion fruit.

Effect of reinforcing flexible biofriendly ternary polymer blend film with bio ionic liquid on structural, thermal and low-frequency dielectric properties for multifunctional biomedical and soft electronics applications

ABSTRACT In present work the effect of reinforcing choline acetate in PVC-PVP-50%PPy on structural, morphological, mechanical, thermal, electrical and low-frequency dielectric properties of base matrix is studied. Synergistic changes in structural, morphological, mechanical, thermal properties and dielectric parameters in low-frequency region of the host matrix are seen. Disk diffusion test for Escherichia coli and Bacillus subtilis shows that the blend film reinforced with Choline acetate showed their benign nature toward bacteria indicating their potentiality to be used for various scale multifunctional dielectric and electrical applications working in close contact with living matter, green electronics and various health monitoring systems.

Critical-like behavior of low-frequency dielectric properties in compressed liquid crystalline octyloxycyanobiphenyl (8OCB) and its nanocolloid with paraelectric BaTiO3

The report presents pressure-related broadband dielectric spectroscopy (BDS) studies in liquid crystalline octyloxycyanobiphenyl (8OCB) and its nanocolloid with BaTiO3 paraelectric nanoparticles. It is focused on the low-frequency (LF) domain, and the impact of pretransitional fluctuations. Studies were carried out in isotropic liquid, nematic, Smectic A, and solid crystal phases. In each case, the critical-type behavior for the LF contribution to the real part of dielectric permittivity and DC electric conductivity is evidenced. Studies of dielectric constant, related to the static frequency domain, revealed in SmA mesophase the shift from the XY-type to the mean-field type criticality when adding nanoparticles. The ‘giant’ premelting effect, with the critical-like portrayal, in the solid crystal phase, is also evidenced. Studies are supplemented by the polarizing microscopy insight into all tested phases appearing on compressing in 8OCB, and the nanocolloid. Photos show prenematic fluctuations in the isotropic liquid phase, phase transitions, changes within nematic and smectic mesophases on compressing, and the impact of nanoparticles.

Optical, thermal and electrical characterization of PEO/CMC incorporated with ZnO/TiO2 NPs for advanced flexible optoelectronic technologies

The optical, thermal, and electrical properties of a blend of polyethylene oxide (PEO) and carboxymethyl cellulose (CMC) are examined in the current work in relation to the effects of zinc oxide (ZnO) and titanium dioxide (TiO2) nanoparticles. To create hybrid ZnO/TiO2 NPs nanocomposites with a PEO/CMC matrix, the solution casting method was utilized. The XRD study results demonstrate that the nanocomposite films' crystallinity decreases with increasing ZnO/TiO2 NP concentrations. FT-IR spectra reveal the interaction between metal oxide NPs and the PEO/CMC composite. UV/Vis analytical spectroscopy was used to calculate the optical properties, such as the energy gap (Eg), refractive index (n), and the number of carbon atoms (M). The inclusion of 7 wt%ZnO/TiO2 NPs decreased the polymer matrix's allowed direct energy gap from 3.68 to 2.81 eV. The AC conductivity results show that the σdc of the nanocomposite samples decreases with increasing ZnO/TiO2 NPs concentrations. The σdc of the final sample (PEO/CMC@7 wt% ZnO/TiO2) was 5.18 × 10−7Scm−1. According to exponential factor (S) results, the dominates conduction mechanism is correlated barrier hopping (CBH) with non-Debye relaxation processes. Space charge polarization was demonstrated by large ε′ values in the low-frequency dielectric properties, whereas an increase in energy loss may be related with a larger εʹ' value in the composite samples. These results prove that these nanocomposites can be used in a variety of energy-related devices, such as flexible capacitors, and energy storage systems.

Green synthesis based X-type Ba–Zn Hexaferrites: Their structural, Hysteresis, Mӧssbauer, dielectric and electrical properties

Ba2Zn2Fe28O46 hexaferrite was prepared using green synthesis with different quantities of ginger root extract (obtained from 0.0, 17.5, 35, 52.5 and 70 g of ginger root) as a natural antioxidant reducing agent. The dried precipitates were preheated at 550 °C/4 h and finally heated at 1200 °C/5 h. The effect of ginger root extract on structural, phase purity, magnetic, Mӧssbauer and low frequency (10 Hz–2 MHz) dielectric properties were investigated. XRD analysis of samples prepared with extracts from 35, 52.5, and 70 g of ginger depicted pure X-phase, while the other samples (0.0, 17.5 g) showed the secondary phase of M-type (BaM, BaFe12O19) along with hematite (12% α-Fe2O3). Hence, samples with greater amounts of ginger extract formed single-phase X-type hexaferrite. Saturation magnetization (MS) varied from 40.8 A m2/kg without ginger extract to 69.8 A m2/kg with extract from 52.5 g ginger, and was <65 A m2/kg for all samples made with the ginger extract. All synthesized samples were relatively soft ferrites, and coercivity increased with amount of ginger extract used. The Mӧssbauer spectra explored six sextets of five magnetic sub-lattices, and the presence of Fe3+ (99.4–97.3 %) and Fe2+ (0.6–2.7 %) ions, with more Fe2+ present in the extract-derived samples. The variations in MS based on hysteresis loops were in agreement by Mössbauer spectroscopy. The use of the extract also significantly reduced the grain size, from 3.3 μm without ginger extract to 0.7–1.7 μm with the extract, with a corresponding increase in coercivity from 16 to 40–80 kA/m. The samples prepared with extracts from 35 g to 52.5 g ginger root possessed considerable real dielectric constant compared to the others, but the extract also increased conductivity in the high-frequency region. Complex impedance displayed low values in the high-frequency region, and Cole-Cole plots revealed that the main contribution to conductivity in extract-based samples was from the grains. The reducing action of the green extract not only produced single phase X ferrite, but it also reduced grain size to ∿1–2 μm and greatly increased MS.

Comparison of Mechanical and Low-Frequency Dielectric Properties of Thermally and Thermo-Mechanically Aged Low Voltage CSPE/XLPE Nuclear Power Plant Cables

During the service period of low-voltage nuclear cables, multiple stresses influence the aging of polymeric materials of cables. Thermal and radiation stresses are considered service aging factors in qualification tests, while the standards usually do not prescribe mechanical stress. CSPE/XLPE insulated nuclear cable samples were exposed to thermal and combined thermo-mechanical aging for more than 1200 h at 120 °C. The real and imaginary parts of permittivity were measured in the 200 μHz to 50 mHz range as dielectric properties. The Shore D hardness of the samples was measured to analyze the mechanical characteristics of the cable. To characterize the dielectric spectrum, derived quantities, namely central real and imaginary permittivities and real and imaginary permittivities’ central frequencies were calculated. The change of dielectric spectra did not show a clear trend with aging, but the imaginary permittivity’s central frequency was higher by 0.5 mHz in the case of thermo-mechanically aged samples. The Shore D hardness was also higher on the thermo-mechanically aged samples. These findings show the combined aging has a higher impact on the insulation properties. Hence, involving the mechanical stress in the aging procedure of cable qualification enables the design of more robust cables in a harsh environment.

Dielectric and microwave absorption properties of Na0.5Bi0.5TiO3–SrTiO3 system

In this work, we have investigated the structural, dielectric and microwave properties of Sr x (Na0.5Bi0.5)1– x TiO3 (0.25 ≤ x ≤ 0.75) prepared using the solid state reaction technique. The Rietveld refinement of the X-ray diffraction pattern at room temperature of the samples is performed to confirm the phase formation as well as the crystal structure of the materials. All the materials are synthesized in cubic Pm3m phase. The low-frequency dielectric properties of the materials are investigated using alternate current impedance spectroscopy in the frequency range from 50 to 1 MHz. The temperature dependence of the dielectric constant at different frequencies gives diffuse peaks which have been attributed to the occurrence of relaxor behavior in these materials. The magnitudes of ε′m, the maximum value of dielectric constant and T m, the temperature corresponding to ε′m are decreased with an increase of Sr2+ ion in the materials. The Vogel-Fulcher relation has been considered to explain the relaxor behavior of the materials. The microwave dielectric properties as well as reflection loss of the materials have also been studied in the frequency range from 1 GHz to 15 GHz.

Influence of Magnetite Nanoparticles Shape and Spontaneous Surface Oxidation on the Electron Transport Mechanism.

The spontaneous oxidation of a magnetite surface and shape design are major aspects of synthesizing various nanostructures with unique magnetic and electrical properties, catalytic activity, and biocompatibility. In this article, the roles of different organic modifiers on the shape and formation of an oxidized layer composed of maghemite were discussed and described in the context of magnetic and electrical properties. It was confirmed that Fe3O4 nanoparticles synthesized in the presence of triphenylphosphine could be characterized by cuboidal shape, a relatively low average particle size (9.6 ± 2.0 nm), and high saturation magnetization equal to 55.2 emu/g. Furthermore, it has been confirmed that low-frequency conductivity and dielectric properties are related to surface disordering and oxidation. The electric energy storage possibility increased for nanoparticles with a disordered and oxidized surface, whereas the dielectric losses in these particles were strongly related to their size. The cuboidal magnetite nanoparticles synthesized in the presence of triphenylphosphine had an ultrahigh electrical conductivity (1.02 × 10−4 S/cm at 10 Hz) in comparison to the spherical ones. At higher temperatures, the maghemite content altered the behavior of electrons. The electrical conductivity can be described by correlated barrier hopping or overlapping large polaron tunneling. Interestingly, the activation energies of electrons transport by the surface were similar for all the analyzed nanoparticles in low- and high-temperature ranges.

Investigation of the effect of in-situ grown PPy on low frequency dielectric properties and other properties of PVA-PVP blend film

Present study is carried out to understand the effect of conducting polymer, polypyrrole (PPy) on structural, morphological, thermal and dielectric properties of bio-compatible polymer blend film of polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP). The growth of PPy in the matrix of PVA–PVP was analyzed using XRD, FT-IR and SEM studies. The shifting in positions and broadening of XRD diffraction peaks of PVA–PVP-PPy from that of PVA–PVP indicates the structural modification and reduction in the crystallinity of the PVA–PVP due to incorporation of PPy. The SEM studies suggest scattered growth of PPy in PVA–PVP matrix at lower concentration of pyrrole monomer. As the monomer concentration is increased, the uniform and interconnected growth of PPy was observed in SEM micrographs. The TGA thermograms show faster thermal degradation of PVA–PVP- PPy films at lower temperature as compared to PVA–PVP films. The blend films of PVA–PVP- PPy exhibited enhanced values of dielectric constant and ac conductivity as compared to the virgin blend film which are observed to increase with increasing concentration of PPy. The high dielectric constant with high ac conductivity exhibited by PVA–PVP-PPy film suggests its possible application as flexible dielectric material for the development of biosensors, energy storage devices in field of green organic electronics.

Ambiguity in the interpretation of the low-frequency dielectric properties of biological tissues

The frequency-dependent behaviour of the dielectric properties of biological tissues in the frequency range below 1 kHz has been under debate since the past century. Here, we reanalyse the raw data of the main resource of the dielectric properties of biological tissues in impedance representation. Employing a Kramers-Kronig validity test and parameter estimation techniques, we can describe the data by two physical parametric models that correspond to opposing biophysical interpretations: on the one hand the data can be explained only by intrinsic tissue properties, but on the other hand evidence for electrode-specific effects can be found for all tissues under investigation. The first interpretation would justify the continued use of a parametric model comprising four Cole-Cole dispersions, which describe the dielectric properties from extremely low to very high frequencies. As an alternative that is in accordance with the second interpretation, we suggest to omit the slowest of the four dispersions in the model and increase the static conductivity to account for a frequency-independent conductivity below 1 kHz.

Measurement of the dielectric properties of various monoolein/ water mesophases between 90 and 140 GHz

Abstract In this paper, the dielectric properties of a series of glyceryl monoolein/ water liquid crystal systems containing 15, 20, 25, 30, 35, 40, 45, and 50 wt.-% water are measured between 90 and 140 GHz. An IEEE standard WR-08 waveguide shim is used as a sample holder. The holder is filled with the monoolein/water liquid crystal system during measurement. The S-parameters of the sample holder filled with the liquid crystal systems are measured using 90-140 GHz millimeter-wave test equipment. The dielectric properties of the crystal systems are extracted from the measured transmission parameters (S21) using the Newton algorithm. We find that the dielectric properties of these glyceryl monoolein/water liquid crystal systems from 90 GHz to 140 GHz are not sensitive to frequency. That is in contrast to the low-frequency dielectric properties in the literature. We also find that the imaginary component of the dielectric spectroscopy between 90 and 140 GHz can identify the phase of the monoolein/water liquid crystal system. The finds in this paper are important for monoolein study.

Measurement of the dielectric properties of various monoolein/ water mesophases between 90 and 140 GHz

Abstract In this paper, the dielectric properties of a series of glyceryl monoolein/ water liquid crystal systems containing 15, 20, 25, 30, 35, 40, 45, and 50 wt.-% water are measured between 90 and 140 GHz. An IEEE standard WR-08 waveguide shim is used as a sample holder. The holder is filled with the monoolein/water liquid crystal system during measurement. The S-parameters of the sample holder filled with the liquid crystal systems are measured using 90-140 GHz millimeter-wave test equipment. The dielectric properties of the crystal systems are extracted from the measured transmission parameters (S21) using the Newton algorithm. We find that the dielectric properties of these glyceryl monoolein/water liquid crystal systems from 90 GHz to 140 GHz are not sensitive to frequency. That is in contrast to the low-frequency dielectric properties in the literature. We also find that the imaginary component of the dielectric spectroscopy between 90 and 140 GHz can identify the phase of the monoolein/water liquid crystal system. The finds in this paper are important for monoolein study.

Raman spectra, photoluminescence, and low-frequency dielectric properties of Ba0.97La0.02Ti1−xNb4x/5O3 (x = 0.00, 0.05) ceramics at room temperature

We are interested to investigate the effect of Nb5+ addition on morphological, dielectric, and optical properties of Ba0.97La0.02Ti1−xNb4x/5O3 (for x = 0.00, 0.05) ceramics. The BLT and BLT0.95N0.04 were successfully synthesized by a low-cost molten-salt method. In addition, the structural phase purity of ceramics was definite by using X-ray diffraction (XRD) at room temperature (RT). Afterward, the morphology of our examples was explored using transmission electron microscopy (TEM) as well as dielectric characterizations. The dielectric constant decreased with increasing frequency. This is assigned to Maxwell–Wagner (M–W) interfacial polarization. What’s more, the room temperature photoluminescence (PL) spectra indicated a synergic effect on BLT1−xNb4x/5 ceramics. At RT, compared to BLT sample, the peaks in the visible region for doped compound are shifted to the highest wavelengths. Note also that width at mid-height reduce for Nb5+-doped BLT than none-doped example. Based on the photometric characterization and the results of the CIE coordinates, they discovered that synthesized perovskite may represent an appropriate candidate for semiconductor lighting devices and optoelectronic applications. Importantly, the tetragonal phases of BLT and BLT0.95Nb0.04 examples can be improved by XRD and Raman spectrum. The incorporation of ions La3+ in the Ba-site is remarkable by the peak observed about 805 cm−1. As well, all modes show a significant broadening with the incorporation of Nb5+ on the titanium-site.

Low frequency dielectric properties related to structure of cotton fabrics

The low-frequency dielectric properties of cotton fabrics in the fabric thickness direction are examined in relation to the fabric construction, thread count and solid volume fraction (SVF) at five different relative humidity levels. It is found that the real part of the relative permittivity increases with increase in thread count, and this is due to the associated increase in SVF. On the other hand, the imaginary part of the relative permittivity and loss tangent (dielectric loss) show no clear monotonic tendency to the SVF at highly moist environments. Permittivity is observed to change depending on fabric constructions under the controlled SVF. These observations indicate that, in addition to the SVF, the fabric geometrical parameters, which are influenced by construction methods, also need to be considered in low-frequency dielectric analysis.

Dielectric Properties of A, B-Site Mn-Doped LaTiO&lt;sub&gt;3+δ&lt;/sub&gt;

A-site Mn-doped La1-xMnxTiO3+δand B-site doped LaMnxTi1-xO3+δ(x = 0.1, 0.2) composites were synthesized by conventional solid-state reaction method. The low-frequency complex dielectric properties of the composites were investigated as functions of temperature (77 K ≤ T ≤ 360 K) and frequency (100 Hz ≤ f ≤ 1 MHz), respectively. The dielectric constants of A-site doped samples are higher than that of B-site doped samples. The loss tangents of the low doped samples are much less than that of the high doped samples. The A-site doped composites exhibit intrinsic dielectric response with a dielectric constant of ~40 in the temperature below 250 K. Interestingly, the dielectric constants of B-site doped composites always increased in the temperature range from 77 to 360 K. And it is clearly observed that extraordinarily low dielectric loss tangents appear in LaMn0.1Ti0.9O3+δ, which are much lower than that of LaMn0.2Ti0.8O3+δ. These changes indicate that the doped content can affect the intrinsic dielectric characteristics significantly.