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The open-ended coaxial probe method is the most commonly used approach for retrieving the dielectric properties of human tissues. This method is also often used to identify cancer because of the difference between the dielectric properties of normal and malignant tissues. This technique not only ensures quick measurement but also has a good identification effect. Although it has the potential to be utilized in tumor surgeries, its clinical application is hindered by the lack of an established identifiable tumor size. In this study, we examine the minimum detectable size of liver tumors by simulation and Mann–Whitney U test. Then, a phantom experiment was conducted to verify the simulation results. For Probes 1, 2, 3, and 4, the smallest cancer tumor detectable size is 0.59, 1.05, 1.85, and 2.95 mm radius, respectively. Furthermore, an evaluation approach for investigating the minimum detectable size of tumors through different probes is proposed. The results showed that the identification sizes were affected by the frequency and size of the probe. Moreover, the minimum detectable size of liver cancer and the crucial factors were investigated in this work. [ABSTRACT FROM AUTHOR]

The dielectric measurements of thiamine hydrochloride (vitamin B1 hydrochloride) and dimethyl sulphoxide (DMSO) binary mixtures have been carried out in the frequency range of 10 MHz to 50 GHz at 25°C, 20°C and 15°C using the TDR technique. The dielectric parameters such as complex dielectric permittivity ɛ*(ω), static dielectric permittivity (ɛs), relaxation time (τ), and asymmetric distribution parameter (β) are obtained by using Cole-Davidson model. These parameters are used to compute thermodynamic properties, Kirkwood correlation factor (geff), and excess molar volume (VE). The heteromolecular H-bonding existing in the binary mixture is explained. [ABSTRACT FROM AUTHOR]

In this work, a mesoporous silica (SBA-15) was synthesized using a hydrothermal method and the surface of the SBA-15 was further modified by utilizing the organosilane compound γ- aminopropyltriethoxysilane(APTES); FT-IR testing confirmed the successful grafting of these organic groups onto the surface of the SBA-15, the result being the AP-S. Composite films were subsequently prepared through a casting method, with SBA-15 and AP-S serving as the inorganic filler particles, and PVA acting as the matrix material. These films were characterized by tensile texts, dynamic mechanical analysis, scanning electron microscopy, and dielectric measurements. The results showed that the tensile modulus, loss modulus and dielectric properties of the modified AP-S/PVA composite films were improved compared with those of SBA-15/PVA, with the tensile strength being the largest at 145.25 MPa when the AP-S content was 2%. This result combined with the SEM analysis, shows that the incorporation of SBA-15 modified by APTES into PVA films can effectively improve the dispersion of SBA-15 in the PVA films, which can also explain the performance enhancement. [ABSTRACT FROM AUTHOR]

In this report, I studied the structural, morphological, and dielectric properties of new ferroelectric compounds prepared according to the formula Ba0.95Sr0.05Ti1-ySnyO3. The solid-state reaction method enhanced by a high-efficiency metal ball mill was used in the preparation process. The quantitative and qualitative analysis of the XRD patterns confirmed the crystallization of the samples y = 0.00, 0.05 in the tetragonal crystal system and the presence of the tetragonal and cubic crystal systems together in the samples y = 0.10, 0.14. Formation of BaSnO3 impurities in very low percentages in the doped samples. Their prevalence increases with increasing tin content, reaching 8.7% at the ratio y = 0.14. SEM images of the ceramic samples showed the formation of nano-ceramics with a high degree of condensation at the doping ratio y = 0.05. The dielectric analyses showed high thermal stability in the dielectric properties of the ceramic samples y = 0.05, 0.10, which was shown by the flatness of the dielectric constant curve over the entire temperature range studied, where this stability is attributed to the structure of the nano-grains that resist the ferroelectric-paraelectric phase transition. Furthermore, the dielectric properties were interpreted by accurately linking the dielectric measurements with the nano-structural and polar properties. [ABSTRACT FROM AUTHOR]

Complex dielectric measurements were performed in 1-nitropropane (NTP) and DMSO mixtures at various concentrations in the frequency range of 10 MHz to 50 GHz using time domain reflectometry technique. The excess inverse relaxation time values were found to be negative, indicating that the dipoles rotated more slowly. Alenka Luzar's hydrogen-bonded theory is used to calculate theoretical estimates of the static dielectric constant. The variations in dielectric parameters such as dielectric constant, relaxation time, Kirkwood correlation factor and excess properties observed in the study confirm the existence of intermolecular interactions within the NTP-DMSO mixtures. [ABSTRACT FROM AUTHOR]

We study the effects of concentration and size of the doped silver nanoparticles on material properties of 6CB nematic: 4-hexyl-4'-cyanobiphenyl using electrical, dielectric measurements along with the polarising microscopy methods. We show that the dispersed NPs do not affect the nematic-isotropic liquid transition temperature. We report that the doped NPs decrease the dielectric anisotropy, elasticity and viscosity of the material. We attribute this behaviour to the fact that the dispersed NPs lower the orientational order parameter of the nematic. However, the threshold voltage stays almost unaffected by the doped NPs and the switching-off time is decreased only at certain NPs concentration. Using our measured data, we test the validity of the predicted by the classical Maier-Saupe theory, linear dependence of the elasticity vs the square root of the order parameter. We show that while for the pure sample the mentioned dependence follows the classical prediction, the dispersed samples elasticity shows anomalous behaviour. We report that the mentioned dependence predicted by Gelbart-Ben Shaul theory fits well with the doped samples measured data. [ABSTRACT FROM AUTHOR]

Epoxy nano-magnetic composites exhibit remarkable and promising properties by synergistically combining the properties of epoxy resin and magnetic nanofillers. The current study deals with the synthesis of Fe3O4, NiFe2O4, and CoFe2O4 nanoparticles and their respective nanoparticles-doped epoxy composites, as well as the structural, optical, and dielectric characterization of the resultant nano-composites. To investigate the surface morphology of the synthesized nanoparticles, field emission electron microscopy (FESEM) analysis was employed. By measuring electron diffraction spectroscopy (EDS), the presence of various chemicals was verified. X-ray diffraction (XRD) was used to determine the structural details of the synthesized nanoparticles and nanoparticles-doped epoxy composites. The structural chemistry and surface functionality of the nano-epoxy composites were investigated using Fourier transform infrared spectroscopy (FTIR). The magnetic properties of the synthesized nanoparticles and nanoparticles loaded epoxy composites were also studied using a vibrating sample magnetometer (VSM). UV–visible reflection spectroscopy was also carried out to find the optical properties of the synthesized nanoparticles, neat (undoped) epoxy, and nanoparticles-doped epoxy composites. Dielectric spectroscopy measurements of nanoparticles-doped epoxy composites were performed using an Agilent E4980A precision LCR (Inductance Capacitance Resistance) meter with an Agilent 16451B-test fixture LCR and vector network analyzer (VNA) in the frequency span of 10 kHz to 2 MHz and 200 MHz to 20 GHz, respectively. The influence of the synthesized nanoparticles on the neat (undoped) epoxy composites and the results in view of future applications are fully discussed. [ABSTRACT FROM AUTHOR]

Bismuth layered compound with the composition SrBi1.5La0.5Nb2O9 has been prepared using conventional solid-state reaction method. Crystallographic planes have been identified using X-ray diffraction studies. The dielectric studies have been done as a function of frequency and temperature. Low temperature dielectric measurement shows phase transition in which peak dielectric constant shifts from 260K to 280K with the increase in frequency from 1 kHz to 1 MHz. Room temperature dielectric constant has been found to be nearly frequency independent for this composition making it a potential candidate for the capacitor applications. The prepared ceramic was modelled using the Vogel – Fulcher relationship. [ABSTRACT FROM AUTHOR]

Structural and electric characteristics of Gd, Li and Sr modified Bismuth Sodium Titanate i.e. (Bi0.5Na0.5)0.6(Gd0.5Li0.5)0.2Sr0.2TiO3 (BNGLST) composition is demonstrated. BNGLST was synthesized by the solid-state mixed oxide method using the stoichiometrically weighed constituent oxides and carbonates. The homogenously wet mixed powder was calcined at 1000 °C for 12h and compressed pellets were sintered at 1250 °C for 2h. X-ray diffraction was carried out to confirm the phase formation. Crystallographic information was extracted from the Rietveld refinement of the XRD data. Dielectric measurement was carried out from room temperature to 300 °C at 1 kHz − 1 MHz frequencies. The a.c. conductivity associated with oxygen ion conduction is discussed in detail as a function of temperature and frequency. [ABSTRACT FROM AUTHOR]

This letter quantifies the phases by Rietveld refinement of perovskite relaxor ferroelectric ceramics of lanthanum-modified lead titanate zirconate (PLZT 9/65/35) as a function of temperature. The refinement results show the relative limit of phases between the polar electrical percolation and their vanishing as a function of temperature, coincident with dielectric measurements. The quantification of polar/nonpolar phases simultaneously is structural description of the polar clusters in relaxor ferroelectrics ceramics. The temperature changes in the polar/nonpolar phase ratio suggest a volume dynamism of the polar clusters as a function of temperature. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive investigation on the synthesis, characterization, and dielectric properties of BaFeO3-x material. The solid-state process was utilized, employing high-purity BaCO3 and Fe2O3 precursors. The calcination step at different temperatures (800 °C, 900 °C, and 1000 °C) revealed that the sample calcined at 1000 °C exhibited the desired perovskite phase with no impurities. Morphological analysis through scanning electron microscopy (SEM) exhibited homogenous cubic grains with well-defined shapes and sizes. The sintered pellets at 1100 °C demonstrated excellent densification, devoid of visible pores or voids, and well-structured grain boundaries. The dielectric measurements unveiled intriguing properties of the BaFeO3-x samples. The dielectric constant exhibited a remarkable peak value of 55,000 at the transition temperature of 145 °C, with an increasing trend as the frequency increased. The dielectric constant also demonstrated frequency-dependent behavior, with higher values at lower frequencies. The dielectric loss remained low below the transition temperature but increased beyond it. Additionally, the modified Uchino law was applied, revealing a linear fit between ln[(εmax/εr)-1] and ln(T˗Tm) at 1 kHz, with a slope of γ (2.8721) and a characteristic length scale of δ (64.34). These findings provide insights into the temperature-dependent dielectric behavior of the material. This study highlights the significance of calcination temperature for achieving the desired crystal structure, as well as the importance of sintering in obtaining dense and well-structured pellets. The intriguing dielectric properties of BaFeO3-x offer potential applications in electronics and energy storage. [ABSTRACT FROM AUTHOR]

The solid-state reaction technique was executed to form a hexagonal double perovskite Bi2FeMnO6 nanopowder. X-ray diffraction (XRD) analysis gives information regarding the product's average crystallite size of 27.9 nm and lattice strain of 0.00125, respectively. The Ultra-Violet (UV) visible spectroscopy data provides a band gap energy of 2.49 eV, which may be a suitable range for photovoltaic applications. Fourier Transform Infrared (FTIR) spectroscopy data analysis reveals the presence of all constituent atomic vibration bands. The dielectric measurements confirmed the presence of the Maxwell-Wanger type of dispersion. The negative temperature coefficient of resistance (NTCR) character is well understood from impedance spectroscopy. The electrical modulus results indicate the presence of a non-Debye-type of relaxation mechanism in the sample. Analyzing ac conductivity data reveals the thermally activated conduction process. The sample's semi-conducting character was confirmed by both Nyquist and Cole-Cole plots. [ABSTRACT FROM AUTHOR]

In this report, we are presenting the effect of B-site co-doping with Sn and Zr (2% each) on frequency and temperature-dependent dielectric and electrical properties of Ba0.5Sr0.5TiO3 (BST). The desired compound is synthesised following solid-state reaction route and the structural and micro-structural study of the resulting compound is done using X-ray diffractometer (XRD) and scanning electron microscope (SEM) technique. XRD study revealed that the parent structure of BST is mostly retained after co-doping. SEM micrograph analysis presented dense packing of grains of different sizes distributed all over the volume of compound formed. The compound was found to have a moderate value of dielectric constant and low tangent loss along with a near stable response of these dielectric properties over the studied frequency range, suggesting its possible application in tuneable matching networks and frequency agile antennas. Electrical properties study suggested a non-Debye type electrical response with a thermally activated conduction mechanism occurring in the material. The dependence of conductivity with temperature showed negative temperature coefficient of temperature behaviour of the compound and the ac conductivity spectrum followed Johnscher's power law. The variation of exponent with temperature suggested correlated barrier hopping conduction mechanism in the material. [ABSTRACT FROM AUTHOR]

A liquid crystal (LC) with negative dielectric anisotropy called N-(4-Methoxybenzylidene)-4-Butylaniline (MBBA) doped with the ionic agent cetyltrimethylammonium bromide (CTAB) has been investigated as a speckle suppression device to reduce the laser's speckle contrast. The electrohydrodynamic instabilities (EHDI) effect in LC is exploited to reduce speckle contrast. The EHDI effect causes chaotic turbulence in LC, resulting in dynamic scattering of the incident light beam. In order to investigate the electro-optic properties and frequency region for optimal performance, optical measurements and dielectric spectroscopy of the pristine and doped LC are performed. The dielectric characteristics of the LC demonstrate that the frequency range to produce the EHDI effect in the LC cell is broadened as the ionic agent is doped. The inclusion of ions also enhances the ion density, mobility, and conductivity in LC. The increase in ion density and mobility enhances the turbulence in the LC at a faster rate; as a result, the dynamic scattering becomes more rapid. When measured with a charge-coupled device (CCD) camera, the faster dynamic scattering provides higher suppression in the laser's speckle contrast. This method can be used to reduce the speckle contrast in laser source-based imaging and projection displays. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive investigation on the synthesis, characterization, and dielectric properties of BaFeO3-x material. The solid-state process was utilized, employing high-purity BaCO3 and Fe2O3 precursors. The calcination step at different temperatures (800 °C, 900 °C, and 1000 °C) revealed that the sample calcined at 1000 °C exhibited the desired perovskite phase with no impurities. Morphological analysis through scanning electron microscopy (SEM) exhibited homogenous cubic grains with well-defined shapes and sizes. The sintered pellets at 1100 °C demonstrated excellent densification, devoid of visible pores or voids, and well-structured grain boundaries. The dielectric measurements unveiled intriguing properties of the BaFeO3-x samples. The dielectric constant exhibited a remarkable peak value of 55,000 at the transition temperature of 145 °C, with an increasing trend as the frequency increased. The dielectric constant also demonstrated frequency-dependent behavior, with higher values at lower frequencies. The dielectric loss remained low below the transition temperature but increased beyond it. Additionally, the modified Uchino law was applied, revealing a linear fit between ln[(εmax/εr)-1] and ln(T˗Tm) at 1 kHz, with a slope of γ (2.8721) and a characteristic length scale of δ (64.34). These findings provide insights into the temperature-dependent dielectric behavior of the material. This study highlights the significance of calcination temperature for achieving the desired crystal structure, as well as the importance of sintering in obtaining dense and well-structured pellets. The intriguing dielectric properties of BaFeO3-x offer potential applications in electronics and energy storage. [ABSTRACT FROM AUTHOR]

The solid-state reaction technique was executed to form a hexagonal double perovskite Bi2FeMnO6 nanopowder. X-ray diffraction (XRD) analysis gives information regarding the product's average crystallite size of 27.9 nm and lattice strain of 0.00125, respectively. The Ultra-Violet (UV) visible spectroscopy data provides a band gap energy of 2.49 eV, which may be a suitable range for photovoltaic applications. Fourier Transform Infrared (FTIR) spectroscopy data analysis reveals the presence of all constituent atomic vibration bands. The dielectric measurements confirmed the presence of the Maxwell-Wanger type of dispersion. The negative temperature coefficient of resistance (NTCR) character is well understood from impedance spectroscopy. The electrical modulus results indicate the presence of a non-Debye-type of relaxation mechanism in the sample. Analyzing ac conductivity data reveals the thermally activated conduction process. The sample's semi-conducting character was confirmed by both Nyquist and Cole-Cole plots. [ABSTRACT FROM AUTHOR]

An ongoing and elusive task is to create single phase anode materials for solid oxide fuel cells (SOFC). Compared to the typical Ni-YSZ cermet anode, perovskite oxide based anode material has a number of benefits. Here, we present the structural and electrical characteristics of Y3+ doped SrTiO3 ceramics that are used as the anode in solid oxide fuel cells. The samples with nominal composition x = 0 and 0.05 were synthesized by high energy ball milling. The powder X-ray diffraction pattern reveals that the synthesized samples crystallize into cubic crystal structure with space group Pm3m for both the compositions. The samples were sintered at a temperature of 1300 °C for 6h. The sintered density of the samples was found to be greater than 97%. The temperature dependent dielectric measurement studies reveal that dielectric constant increases with yttrium doping and shows relaxer behavior. A higher dielectric constant and electrical conductivity was observed for the Y-doped sample which fulfill the basic requirement for anode materials of solid oxide fuel cells. [ABSTRACT FROM AUTHOR]

Crystal structure and Dielectric properties investigation of lead-free Bi0.35Na0.25Li0.1Sr0.3TiO3 (BNLST) composite is reported. The required solid solution was synthesized using oxides and carbonates via the solid-state reaction method. The stoichiometrically weighed and mixed powder was calcined at 800 °C for 12 h, and the pellets were sintered at 1250 °C for 2 h. XRD measurements confirm the formation of single-phase rhombohedral perovskite structure and the crystal structure was refined using the X'Pert High-score plus software. The full-width half maxima of the XRD peak was used to compute the average crystallite size employing the Debye-Scherrer, Williamson-Hall, and Halder-Wagner techniques. The BNLST's dielectric measurements were performed as a function of temperature at five distinct frequencies in the range of 100 Hz–1 MHz. The phase transition temperatures are shifted toward room temperature with the doping of Li and Sr. The diffuseness parameters of the phase transition, the a.c. electrical conductivity and the activation energy are estimated for the BNLST composite. [ABSTRACT FROM AUTHOR]

Complex dielectric measurements by using the Time Domain Reflectometry technique between the frequency range 10 MHz to 30 GHz have been accomplished for different concentrations of 1-iodobutane (IDB) and 1, 4-Dioxane (DX) binary mixtures at 5 °C to 25 °C temperatures. Debye model was used to fit the complex permittivity spectra of IDB-DX binary mixture. The Luzar model is applied to calculate the average number of hydrogen bonds in IDB-IDB and IDB-DX molecules. The measured value of hydrogen bond density is found to be maximum for this binary mixture at dioxane concentration VDX ≈ 0.7. To study the dielectric behavior and to observe the modification in the strength of hydrogen bond in the presence of other nonpolar molecule is the main aim of the proposed work. Measurement of Kirkwood correlation factor and Bruggeman factor provide the valuable information regarding the formation of hydrogen bonded molecular multimers and intermolecular interaction in the binary mixture. Information on the molecular interactions in binary mixtures is also provided by the study. [ABSTRACT FROM AUTHOR]

This study focused on the rare-earth hetero-valent substituted perovskite BaMO3 (M = Ce, Pr and Tb) which expected to show magnetoelectric response. In general, diamagnetic feature is presented in the 4f0 BaCeO3 system down to 2 K which is chosen as a reference in the study while BaPrO3 (4f1) and BaTbO3 (4f7) display antiferromagnetic phase transition at TN = 11.7 and 33.2 K, respectively, measured by MPMS magnetometer. At high oxygen partial pressure and donor ion-substitution (Nb5+), the BaMO3 systems demonstrate a similar defect chemistry to titanate perovskite which compensated by Ba-vacancy. Dielectric relaxation is detected for the doublet (BaPrO3 and BaTbO3) at the antiferromagnetic phase transition region. In order to examine the magnetoelectric response, the 8 Tesla of magnetic field is applied to the samples during the dielectric measurement. BaTbO3 shows a modest magnetoelectric response around 0.2% at the antiferromagnetic phase transition while that of BaPrO3 is silent. The activation energies derived from Arrhenius equation are reported to be in the range of 0.2 − 0.6 eV. [ABSTRACT FROM AUTHOR]

The dielectric constant measurements of Fe implanted TlInS2 and TlGaSe2 crystals without and under application of constant magnetic field have been performed. It has been observed that the implantation of the crystals with Fe ions caused the formation of ferromagnetic layer in the irradiated region, which leads to considerable shifts of the successive incommensurate and commensurate phase transitions to high temperatures in the heating regime. Remarkable shifts of the phase transition temperatures back to the low temperature region on heating of the samples were observed on applying the magnetic field perpendicularly to the implanted surface. None changes of the phase transition temperature points on measurements of the samples have been observed in cooling regime. The obtained results are interpreted as magnetodielectric effects that resulted from magnetoelectric coupling between ferromagnetic and ferroelectric constituents of the composite structure. [ABSTRACT FROM AUTHOR]

Antiferroelectricity is a desirable property of liquid crystalline materials. Therefore, we synthesised and studied two new chiral rod-like mesogens with a molecular core based on two biphenyls connected via ester linkage, with the phenyl substituted by a fluorine atom. The studied mesogens are characterised by nuclear magnetic resonance spectroscopy and mass spectrometry analysis. They have methyl heptyl in the chiral chain and exhibit an antiferroelectric phase in a very broad temperature range. We investigated their mesomorphic properties and confirmed the phase identification by differential scanning calorimetry and broad-frequency dielectric spectroscopy measurements. Additionally, we compared the studied mesogens with previously synthesised analogous materials. Two mixtures were formulated using a base mixture and new mesogens. The helical pitch of the synthesised mesogens and formulated mixtures was estimated using the selective reflection method. [ABSTRACT FROM AUTHOR]

Detailed heat capacity, birefringence and dielectric anisotropy measurements have been carried out near the nematic – smectic-C (NC) and the nematic – smectic-A (NA) phase transitions of a mesogenic binary system. Important feature is the existence of two tricritical points one for the NC transition and other for the NA transition. The dependence of critical exponent (α) is well explained in terms of temperature ratios (TNC/TNI and TNA/TNI) for the NC and NA phase transitions. Both transitions exhibit non-universal behaviour and showing effective critical exponents in between tricritical and 3D-XY values. However, the nematic range necessary for the NC tricritical point is quite large (>20°C). The enthalpy, phase shift and imaginary heat capacity are also analogous to the nature of the critical exponent (α). Moreover, within a very small concentration range, the smectic-A – smectic-C (AC) transition line appears. Although the smectic-A width above the AC transition is quite small~2K, heat capacity and birefringence data clearly confirm second-order nature. Additionally, there exists a region where the NC, NA and AC line segments converge, i.e. a NAC multicritical point. At this point, the latent heat for the NC, NA and AC transition lines disappears, indicating an obvious second-order nature of the NAC multicritical point. [ABSTRACT FROM AUTHOR]

The arrangement and shape of coils for permittivity measurement of a dielectric sandwiched between carbon fiber reinforced plastics (CFRPs) using electromagnetic induction testing (EIT) is investigated here. First, the influence of the electromagnetic shielding effectiveness of the CFRPs on the permittivity measurement using EIT was examined by finite element analysis (FEA). The effectiveness was lower than that of general metals, indicating that EIT can be used for permittivity measurement. Next, the coil arrangement and shape suitable for permittivity measurement were investigated by FEA. The use of two rectangular spiral coils, one as a driver coil and the other as a pickup coil, was adopted. Finally, the permittivity was measured experimentally using the coil arrangement, geometry, and test conditions determined based on the FEA results. The experimental results showed that the output voltage increased as the permittivity increased, demonstrating the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Simultaneous influence of marination and storage on dielectric properties of chicken meat was investigated through dielectric measurements at microwave frequencies. For this purpose, an open-ended coaxial probe and a vector network analyzer were used for measurement of the dielectric properties between 200 MHz and 20 GHz and at a room temperature of 22 °C. For all chicken samples, the same general trend was observed for the variations of dielectric properties with frequency. The dielectric constant decreased with frequency with significant slope change at about 5 GHz. The dielectric loss factor decreased sharply up to 2 GHz and then increased with frequency showing a broad relaxation above 8 GHz. Values of the dielectric constant and dielectric loss factor measured for marinated chicken meat samples were greater than those of non-marinated samples and this was more significant for the dielectric loss factor at lower frequencies. In addition, each level of marination was distinctly observed over the same frequency range. Investigation of the influence of storage revealed that the dielectric loss factor of marinated samples decreased over the storage period while those of non-marinated sample slightly increased with storage time. For both marinated and non-marinated samples, water loss increased with storage time. [ABSTRACT FROM AUTHOR]

Time Domain Reflectometry (TDR) and frequency domain techniques have been used for the dielectric measurement of methyl cellulose (MC) with water for different concentrations and frequency ranges from 20 Hz to 2 MHz and 10 MHz to 30 GHz at 25°C. The dielectric relaxation in these mixtures can be represented by the Debye relaxation behaviour. The dielectric parameters such as complex permittivity ε*(ω), complex electrical modulus M*(ω), complex electrical conductivity σ*(ω), loss tangent (tan δ), static dielectric constant (ε0) and relaxation time (τ) have been determined. The variation of dielectric parameters of methyl cellulose (MC) in water suggested that methyl cellulose (MC) bonds with water alter its structure and electric dipole moment. [ABSTRACT FROM AUTHOR]

The present article shows an original transmission-reflection-based method to characterise the microwave dielectric properties of liquid crystals. This new method offering broadband capabilities of transmission-reflection method without the need for vector network analyser calibration. It is based on two measurements in the frequency range: one measurement is performed with the empty cell, the other with the cell filled with the material. The analysis of the two recorded scattering matrices allows to eliminate all error terms and to extract real and imaginary parts of the complex dielectric constant. In this paper, we first present this method, its validation in comparison to other characterisation methods. Secondly, we present an appropriate measuring cell which allows measurements in the frequency range 26 GHz-40 GHz which is also well-suited for temperature-dependent measurements. This method is used to perform dielectric microwave measurements on 5CB liquid crystal. Finally, we discuss the temperature-dependent microwave dielectric properties (permittivity, losses and dielectric anisotropy). [ABSTRACT FROM AUTHOR]

We report on observations of optical switching in bent-core liquid crystals possessing azocinnamoyl groups in both elongated side arms. UV-activated switching was observed in two of the synthesised materials, both of which were studied optically and with dielectric spectroscopy. Polarising microscopy was used to measure the changes in optical transmittance, and while no illumination effect was seen in the nematic phase, visible changes were observed in the smectic phase, most pronounced in the close vicinity of the smectic to nematic-phase transition. Switching dynamics was characterised, and we found that the average switching time varies strongly with temperature. The relaxation process is faster (below $200\,\,{\rm{ms}}$ 200 m s ) and exhibits no significant temperature dependence. Dielectric measurements have shown that the observed smectic C phases were not polar with the molecules possessing a rather small electric dipole moment. Upon illumination, small differences in the dielectric permittivity were observed only in the smectic phase, suggesting that the illumination effect can be attributed to changes in the molecular conformational and orientational order. [ABSTRACT FROM AUTHOR]

Reconfigurable microwave material is a promising candidate for designing and manufacturing tunable microwave components. Nematic liquid crystals (NLC) are such materials since their permittivity can be tuned by an external electric field. However, many NLC mixtures were not properly characterised at higher frequency bands due to requiring a complex measurement setup. In this work, a novel method using circular patch resonator (CPR) is developed to measure the dielectric constant and loss tangent of NLCs at microwave frequencies. In addition to using the cavity model for the preliminary design and analysing the fringing effect for a better accuracy, full-wave simulations are employed to confirm the final design and aid the characteristic analysis. Three prototypes were fabricated and measured to reduce uncertainty from manufacturing defects. To avoid the possible damage when higher voltage is required for a large range tuning, a coupling mechanism is proposed between the microstrip line and coplanar waveguides (CPWs) to replace connection through vias. A high accuracy with an uncertainty of 0.02 for relative permittivity estimate has been demonstrated with experiment verification, approximate 80% improvement than other typical methods. The simple design and PCB-based manufacturing techniques can be widely employed to characterise the properties of newly-developed LC mixtures. [ABSTRACT FROM AUTHOR]

The polyimides were prepared by pyromellitic dianhydride (PMDA) or 4,4'-(4,4'-Isopropylidenediphenoxy)diphthalic anhydride (BPADA) as dianhydride monomer and 1,4-bis(4-aminophenoxy)benzene(TPE-Q) or 1,3-bis(4-aminophenoxy)benzene(TPE-R) as diamine monomer. The polyimides were well characterized by FT-IR, thermogravimetric analysis, dynamic thermomechanical analysis, dielectric measurement and tensile test. The flexibility of polyimide molecular chain was judged by the comparison of molecular volumes, molecular length and conformation transition energy through molecular simulations. [ABSTRACT FROM AUTHOR]

Electromagnetic interference (EMI) shielding inks are generally conducting inks and therefore, are mostly reflection based. EMI shielding based on reflection are sometimes not suitable for certain applications apart from the fact that they themselves act as secondary source of EM waves. Here, we develop reduced graphene oxide (rGO)- zinc nickel ferrite (ZNF) and rGO-manganese (Mn)-doped zinc nickel ferrite inks for EM absorption in X-band, which have been tested in liquid state, coatings, and as printed meta-structures demonstrating versatile use of the inks. As a coating, the average EMI shielding of more than 30 dB is achieved in the 8 to 12 GHz range. The absorption properties of the rGO based ink can be increased from 50% to more than 80% by addition of a ferrite composite and can further be tuned by Mn doping. The dielectric measurement studies reveal that addition of Mn creates sites for interfacial polarization. The interfaces between polymer matrix, rGO, ZNF, and Mn contribute to conductivity, dipole and interfacial polarization losses, thereby augmenting absorption dominated EMI shielding. Cole-cole plot for the inks also indicates multiple relaxation processes confirming the role interfaces in absorption properties of the composite ink. [ABSTRACT FROM AUTHOR]

3D-printed electronics belong to new approaches to how to build a complex object with multiple desired functions. For that purpose, materials with specific electric properties are needed: conductors, insulators, magnetics, or dielectrics with high permittivity. However, such materials are not commonly available in the form of filament for fused deposition modelling since the development is still ongoing. This paper describes the electrical properties of PETG-ceramic composite filaments. PETG (polyethylene terephthalate glycol-modified) was filled with titanium dioxide (10 and 20 wt.%) to increase the dielectric constant and, simultaneously, to preserve printing simplicity as the material key advantage. Dielectric spectroscopy and measurement of volume resistivity were performed on printed samples. Relative permittivity increased by 50% for a composite filled with 20 wt.% of ceramic particles (εr = 2.5÷4.4) against pure PETG. Permittivity and dielectric loss exhibited frequency and temperature independence. The prepared composite can be used for dielectric applications in electronics. [ABSTRACT FROM AUTHOR]

Herein, a small concentration (0.05 wt %) of reduced graphene oxide is dispersed in the liquid crystalline media. Thermodynamic study shows the reduction of the transition temperature, enthalpy and entropy of the reduced graphene oxide dispersed nanocomposite. Optical study suggests the decrease of the optical bandgap of the dispersed nanocomposite as compared to that of the pure sample. Dielectric spectroscopic measurement is done for measuring the permittivity and conductivity of the pure and the dispersed samples. The value of dielectric anisotropy has decreased for the dispersed nanocomposite whereas the value of ionic (DC) conductivity of the dispersed nanocomposite has increased by 3 orders of the magnitude as compared to that of the pristine sample. The activation energy for DC conductivity has reduced in the dispersed nanocomposite which is responsible for the increment in DC conductivity of the system. The cut-off region of DC conductivity has increased in the dispersed nanocomposite. Electro-optical studies suggest the reduction of the threshold voltage for the Freedericksz transition, splay elastic constant and rotational viscosity for the dispersed nanocomposite. [ABSTRACT FROM AUTHOR]

A dielectric-based method for real-time tracking of changes in water activity in almond kernels is proposed. The method is based on measurement of the dielectric properties at a single microwave frequency. Samples of almond kernels (Butte/Padre and Nonpareil) were placed in a chamber with high humidity and their dielectric properties were measured at 10 GHz and room temperature (22 °C) every few hours. The dielectric properties increased linearly with time and exponentially with water activity. A three-parameter exponential growth equation provided relationships correlating the dielectric constant (ε'), the dielectric loss factor, (ε"), and the loss tangent (ε"/ε') with water activity with high coefficients of determination (r2). From these equations, water activity calibration equations were obtained. Performance of these equations in predicting water activity under dynamic situations were assessed by calculating the standard error of calibration (SEC). Values of SEC ranged from 0.01 to 0.05. [ABSTRACT FROM AUTHOR]

In the present work, the Sr(Fe0.5Nb0.5)1-xMnxO3 powders were synthesized via a molten salt technique. Pure phase perovskite was obtained at 800 °C which was very low compared to previous works prepared by solid state reaction technique (> 1200 °C). XRD analysis for the Sr(Fe0.5Nb0.5)1-xMnxO3 ceramics revealed that the unit cell had an orthorhombic symmetry. Examination of dielectric measurement showed that all ceramic samples exhibited very high dielectric constants (εr,max > 200,000 at 1 kHz). The dielectric data showed that all ceramics exhibited a relaxor like behavior. Loss tangent value tended to decrease with increasing Mn, especially at low temperature range. The obtained loss tangent values were found to be lower than those reported in previous works. Impedance spectroscopy analysis revealed that the relaxor like behavior could be related with bulk grain, grain boundaries and electrode responses, where the samples had a heterogeneous conduction. Type of electrode and applied voltage had strong effects on the dielectric behavior. [ABSTRACT FROM AUTHOR]

Pure and Cu/Ag co-doped ZnO nanoparticles were synthesised by the co-precipitation method. The phase and structural analysis of ZnO nanoparticles were examined by using XRD and Williamson-Hall plots. XRD spectra revealed that prepared samples exhibit hexagonal wurtzite structure of ZnO. The change in lattice parameters, bond length, dislocation density and strain indicates that Cu and Ag were successfully incorporated. UV vis studies indicated the red shift in the absorption band attributed to defects induced after dopant additions. The dielectric measurements showed that the dielectric constant was found to increase and the dielectric loss decreases with increase in dopant percentage. Additions of Cu and Ag in ZnO lattice may lead to supplement grain boundary defects which can increase polarisation. The relatively higher values of ac conductivity were also found due to modulation of charge carrier density after dopant additions which suggest that the diffusion controlled charge carrier hopping mechanism is involved. [ABSTRACT FROM AUTHOR]

A refractive-mixing dielectric model for frozen and thawed organic-rich soils at a frequency of 435 MHz was developed in this letter. The model was developed based on the dielectric measurements of five soil samples in which organic matter content was variated from 35% to 80% (by weight). Dielectric measurements were conducted in the range of volumetric soil moisture from ~2% to 60%, and the range of temperature from −30°C to 25°C. Coefficient of determination (R2) and root mean square error (RMSE) between predicted by the model and measured values for real ( ε ′ ) and imaginary ( ε ′ ′ ) part of complex relative permittivity are R ε ′ 2 = 0.989 ( R M S E ε ′ =0.602) and R ε ′ ′ 2 = 0.906 ( R M S E ε ′ ′ =0.404), respectively. The developed dielectric model can be used for creating remote sensing algorithms (soil moisture retrieval in the root zone, active layer thickness and ice content measuring in permafrost area, etc.) in P-band. [ABSTRACT FROM AUTHOR]

0.9Bi1-xNdxFeO3 − 0.1PbTiO3 solid solution with x = 0.05, 0.10, 0.15 and 0.20 were success fully synthesized by the standard solid-state reaction method. The effect of Nd3+ion substitution on structural, micro structural, ferroelectric, magnetic and dielectric properties of 0.9BiFeO3-0.1PbTiO3 have been investigated. The XRD analysis for the samples under study revealed distorted rhombohedral structure with R3C space group. 0.9Bi1-xNdxFeO3 − 0.1PbTiO3 i.e. (BNFPT)x with x = 0.05, 0.10, 0.15 and 0.20 compounds crystallized as single-phase materials with the same structure as the parent BiFeO3 compound. The SEM study revealed the uniform grain scattering for all prepared samples. Raman spectroscopy showed disappearance of some Raman modes indicated a structural phase transition with substitution of Nd dopants at Bi site and also confirmed the distorted rhombohedral perovskite structure of (BNFPT)x compounds with R3c symmetry. Dielectric measurements reveals that, around Neel temperature, all the samples exhibit magneto-electric coupling and also improved dielectric properties with addition of dopants in BiFeO3(BFO) compound. All the prepared samples exhibit weak ferro-magnetic character at room temperature. However, the variation in linear behavior and enhancement in magnetization is found at 5 K which shows gradual increase in remnant magnetization from 0.00785 emu/g to 0.37513 emu/g with increase in Nd doping for all (BNFPT)x samples. Nd doping reduces leakage current by three orders of magnitude, from 10−4 to 10−7. Ferroelectric study revealed the pinning effect in hysteresis loops with low remnant polarization and coercive field which can be related to the energy storage performance of the samples. [ABSTRACT FROM AUTHOR]

The powder samples of (Na0.5Bi0.5)0.705Ba0.045Sr0.25TiO3-xLa2O3 (NBBSLT) have been prepared successfully by a wet solid-phase method. The effects of La doping on the morphology, ferroelectric and dielectric properties of NBBSLT ceramics were studied. XRD results show that the composite has perovskite structure. The dense phase morphology of NBBSLT was observed by SEM. Dielectric measurements show that depolarization temperature and Curie temperature move toward low temperature. With the increase of La content, the ferroelectric hysteresis loops at room temperature become thinner at first and then wider. The NBBSLT ceramics have excellent energy storage properties when the La content is 0.04. [ABSTRACT FROM AUTHOR]

Complexes [Zn(C6H5CONH2)2Br2] and [Zn((NH2)2CO)2Br2] were synthesized and characterized by elemental analysis, IR spectroscopy, and X-ray diffraction and compared to other complexes of zinc halides with benzamide and urea. In all complexes, the zinc ion has a tetrahedral coordination environment of two halide ligands and two oxygen atoms of two amide ligands. The structure of [Zn(C6H5CONH2)2Br2] (orthorhombic, Pna21, a = 29.207(6), b = 7.5826(14), c = 14.753(3) Å, Z = 8) is not isostructural to the chloride and iodide compounds. The [Zn((NH2)2CO)2Br2] complex (triclinic, P-1, a = 6.4435(9), b = 7.096(1), c = 11.7079(18) Å, α = 88.119(9)°, β = 77.005(9)°, γ = 66.320(8)°, Z = 2) is isostructural to [Zn((NH2)2CO)2Cl2], and they both differ from [Zn((NH2)2CO)2I2]. Dipole moments of complexes of various zinc halides with benzamide, urea, and dimethylformamide were calculated; they vary in the 9–13 D range. Complexes of zinc halides with amides were used to prepare films with the use of cellulose diacetate as a polymer matrix. Dielectric measurements showed the presence of a pronounced electret effect. [ABSTRACT FROM AUTHOR]

Phase formations and dielectric properties of lead free barium titanate bismuth zinc zirconate, BaTiO3-Bi(Zn0.5Zr0.5)O3 (BT-BZZ), were comparatively investigated between two different synthesis routes, solid state reaction and salt flux assistance methods. The perovskite (1-x)BT-(x)BZZ ceramics, where x = 0.02, 0.05 and 0.10, were synthesized by using reagent grade oxides and the NaCl salt was used as a surface active agent to lower the calcination temperature. Phase formations were examined by X-ray diffraction technique (XRD). It was found that the solid solutions of (1-x)BT-(x)BZZ can be obtained with lower temperature at least 200 °C via salt flux assistance method. The NaCl salt addition could result in single phase of perovskite structure at every compositions with the calcination temperature as low as 800 °C. Dielectric measurements revealed that the Curie temperature (Tc) shifted to lower temperature with increase of BZZ concentration. Moreover, the dielectric behavior transformed to diffuse phase transition when x = 0.1. The samples prepared via salt flux assistance method exhibited smaller grain size which were revealed by scanning electron microscope. In addition, P-E hysteresis measurements illustrated the higher high E-field dielectric constant with the narrower P-E loop when the salt flux was applied. [ABSTRACT FROM AUTHOR]

B2O3–Bi2O3–SiO2–Sm2O3 glasses have been synthesized by melt quench technique for different mol% Sm2O3. The electrical behavior of these glasses was studied by impedance spectroscopy technique at room temperature, covering the frequency range between 1 M and 1 GHz. In addition, dielectric measurements were made to evaluate the dependence of the dielectric constant different Sm ions. The dielectric constant is approximately 3200 at room temperature for 0.5 mol% Sm-doped compositions at 645 MHz frequency. The results show significant variations for the real part and large variations for the imaginary part among different frequency with different Sm fractions. Complex impedance analysis was used to estimate its electrical conductivity as well as its corresponding optical properties. [ABSTRACT FROM AUTHOR]

We study the effects of graphene nanoparticles on dielectric and material properties of 5CB nematic: 4-he-4ʹ-cyanobiphenyl. Using the experimental methods of dielectric measurements and polarising microscopy we show that the dispersed NPs decrease the nematic-isotropic liquid transition temperature. The doped NPs also decrease the dielectric anisotropy, elasticity and viscosity of the material. We propose that all mentioned decreases are caused by the distortion of LC molecules orientational order by disc-shaped graphene NPs, which have 'weak' anisotropy. We report that the threshold voltage stays almost unaffected by the doped GNPs. On the contrary, the doped NPs significantly (4–5 times) decrease the switching-off time of the nematic. This fact makes the studied systems promising candidates for their applications in electro-optical devises. We also test the validity of the classical Maier-Saupe theory, which predicts a linear dependence of the elasticity vs the square root of the order parameter. By comparing experimental data with the theoretical prediction, we show that the pure nematic's behaviour follows the classical prediction. However, the doped samples behaviour departs from the classical prediction.. [ABSTRACT FROM AUTHOR]

The dielectric measurements have been executed by making the use of time domain reflectometry (TDR) technique for 1-pentanol and ethanol in the pure form and for their binary liquid mixture in the frequency interim of 10 MHz–50 GHz at varying temperatures, respectively. The complex permittivity spectra studied show Debye behaviour and plotted as the function of frequency. The temperature-dependent dielectric constant and relaxation time values were estimated. The Kirkwood correlation factor (geff) has also been studied to determine the alignment of dipole moments in mixture. The thermodynamic parameters and temperature-dependent behaviour of relaxation time, i.e. Arrhenius plot, have been studied. [ABSTRACT FROM AUTHOR]

This study distinguishes the design and analysis of a coaxial probe for measurement of biological body dielectric properties, in this measurement estimating the human tissue-equivalent liquid (TEL) permittivity and conductivity, to monitor and maintain the international standards for specific absorption rate (SAR) evaluation over the frequency band of 800 MHz-5 GHz. In addition, deionized (DI) water and ethanediol dielectric properties have been evaluated and the designed probe results compared to the commercial Dielectric Assessment kit (DAK) 3.5 probe. The obtained results are in good agreement with each other, moreover, the SAR calculation and each source of uncertainty budget analysis are estimated. Therefore, this fabricated probe may be suitable for liquid dielectric properties measurement. [ABSTRACT FROM AUTHOR]

Recently nanoparticles (NPs) are extensively explored as the dopant in liquid crystal (LC) materials because of their phenomenal properties such as good guest–host interaction and high surface to volume ratio. Keeping this motivation into mind, we have observed the influence of newly synthesized cobalt oxide (CoO) NPs on the dielectric and optical properties of nematic LC (NLC) namely 5 CB. For the observation of dielectric properties, we have performed dielectric spectroscopic measurements in the frequency range from 20 Hz to 1 MHz. The sample cell thickness-dependent studies have been performed to perceive the effect of applied field strength on dielectric parameters in presence of CoO NPs. Along with it, we have observed the alignment of the mesogens through the optical microscopy. So doping of such NPs serves various potential applications in the field of research as well as being proven to be cost-effective for industrial applications. In this article, we report the variation in dielectric properties of nematic liquid crystal (NLC) namely 5CB by the means of cobalt oxide nanoparticles (CoO NPs) doping. These CoO NPs may work as the ion absorbing agent in the NLC medium and can easily modify dielectric properties without influencing molecular alignment. Along with this, we have performed the LC sample cell thickness dependent studies of pure and CoO NPs doped 5 CB. [ABSTRACT FROM AUTHOR]

Dielectric properties of any particular material will determine the level of microwave (MW) heating. Therefore, measurement of the dielectric properties of MW treatment subject materials is necessary. This study investigated the dielectric properties of six roughages and three concentrate animal feeds across the microwave frequency range of 1 × 109 to 5 × 109 Hz. Six treatment groups, named control (at equilibrium moisture constant), oven dried (0% moisture), 25% moisture added, 50% moisture added, 75% moisture added, and 100% moisture added groups were prepared for the study. Three separate replications and five observations for each replication were used to assess the dielectric properties of these materials. The results showed that for increasing moisture content, from oven-dried, though the control status, to 100% added moisture, both the dielectric constant (real part) and the dielectric loss factor (imaginary part) increased for both the roughages and concentrates. However, the responses were not linear. The oven-dried plant samples' dielectric properties were very low compared with those of the higher moisture content samples. Thus, the sample's moisture content was the dominant contributor to the feed samples' dielectric behavior. Among all the feed samples, faba bean and wheat grain showed the highest response to added moisture. Mathematical models were developed to explain the dielectric properties of feeds as a function of frequency and moisture content. The goodness of fit (r2) for these models' real part varied between 0.85–0.99 for roughage and 0.98–0.99 for concentrate feed type. On the other hand, the goodness of fit for the imaginary part varied between 0.59–0.78 for roughage, and 0.81–0.93 for concentrate feeds. [ABSTRACT FROM AUTHOR]

Nanocomposites C:S-1:4 comprising cobalt ferrite (CoFe2O4), strontium ferrite (SrFe12O19) and C:B-1:4 containing cobalt ferrite (CoFe2O4), barium ferrite (BaFe12O19) were synthesized in weight ratios of 1:4 by chemical co-precipitation route with higher content corresponding to SrFe12O19 and BaFe12O19. Rietveld refinement was employed to confirm the presence of independent CoFe2O4, SrFe12O19 and BaFe12O19 phases. The average crystallite size of CoFe2O4 and SrFe12O19 in C:S-1:4 was observed as 20 nm and 56 nm which depicts an increase as compared to individual components. The observed lattice strain in C:S-1:4 was 0.05% and 0.03% for CoFe2O4 and SrFe12O19. In C:B-1:4, the value of strain was 0.06% and 0.04% for CoFe2O4 and BaFe12O19. Increased lattice strain was observed in the prepared composites. Increase in impedance for the prepared composites was observed from measurements performed in the frequency range 20 –106 Hz. Conduction mechanism was explained by overlapping large polaron tunneling model. Dielectric loss measurements for the prepared composites were observed to decrease establishing their usage in microwave applications. [ABSTRACT FROM AUTHOR]

Measuring the dielectric properties of the fabric is much important when it is used as a substrate material for flexible electronic devices. However, the classical resonant cavity is not accurate for thin fabric measurement. This article applied the strip line ring resonator principle, which was successfully used to measure the dielectric constant of the thin film. The ring resonator was constructed by 12-layer fabric stacked together with single-side copper-etched RO5880 substrate. The resonant frequency and Q factor were measured and compared with finite element simulation results, and then the dielectric constant and loss were accurately deduced. First, a RO5880 was used as the unknown substrate to replace the fabric to verify its accuracy, and the relative error of dielectric constant and loss is 0.9% and 5.6%, respectively. And then, the same method was used to measure the fabric. As a result, the dielectric constant and loss tangent of fabric were 2.4 ± 0.05 and 0.05 ± 0.01, respectively. [ABSTRACT FROM AUTHOR]

It is vital to determine the dielectric characterization of hemp plant (Cannabis Sativa) for microwave remote sensing to increase its accuracy and to improve algorithms for satellite data interpretation. For that, this study provides the measurement results of complex permittivity of hemp stems and leaves in terms of various moisture contents (MC) in 8–12.4 GHz in a laboratory with a temperature of 25°C and a relative humidity of 59%. With the measurement data, the dielectric properties are modelled as a second-order polynomial function based on a curve-fitting method depending on the frequency and MC. For hemp stems and leaves with various MC, while the real part of the relative complex permittivity ( ε ′ ) ranges between 2.1–7.2 and 1.5–6.1, the imaginary part of that ( ε ″ ) varies in 0.3–4.5 and 0.2–4.2, respectively. The measured and modelled results are compatible with each other. [ABSTRACT FROM AUTHOR]