Dielectric Permittivity Measurements Research Articles

State-of-the-Art Inkjet-Printed Metal-Insulator-Metal (MIM) Capacitors on Silicon Substrate

Vertically-integrated metal-insulator-metal (MIM) capacitors on silicon are demonstrated for the first time utilizing an entirely additive RF-specific inkjet-printing process. The inkjet-printed MIM capacitors demonstrate a high capacitance per unit area of up to 33 pF/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> by utilizing novel dielectric inks, while achieving quality factors (Q) up to 25 and self-resonant frequencies (SRFs) above 1 GHz. Measurements of dielectric permittivity, leakage current, voltage breakdown, and fabrication repeatability are presented confirming the high-performance operation of the printed MIM capacitors.

Permittivity and Loss Characterization of SU-8 Films for mmW and Terahertz Applications

The dielectric permittivity measurement of thick SU-8 film is presented for the entire frequency band of 1 GHz to 1 THz. SU-8 is a high-resolution UV-patternable photoresist that can be used for fabrication of high-aspect-ratio 3-D structures for millimeter-wave and terahertz devices. Here, we report the measured dielectric constant and loss tangent of SU-8 films using terahertz time-domain spectroscopy. A quadratic polynomial model is established for the accurate calculation of complex permittivity up to 1 THz. The loss tangent of fully cross-linked 430- $\mu\hbox{m}$ -thick SU-8 film was measured to be 0.015, 0.027, and 0.055 at 1, 200, and 1000 GHz, respectively. Similarly, relative permittivity was found to be 3.24, 3.23, and 2.92. The fabrication process and level of cross-linking were demonstrated to have significant impact on the loss behavior of this material and the impact of cross-linking on dielectric permittivity is quantified across a wide frequency band. The characterization results reported in this letter are a platform for developing next-generation millimeter-wave and terahertz devices.

Reduction of the Curie temperature in the multiferroic Bi5Fe1+xTi3−xO15 solid solution

In this work, the phase diagram of the system Bi4Ti3O12-BiFeO3 in the region of the solid solution Bi5Fe1+xTi3−xO15 was refined. The limit of solubility was determined to be at x = 0.1. The Curie temperature (TC) of the ferroelectric phase transition was determined by dielectric permittivity measurements at 100 kHz for the phase Bi5FeTi3O15 as well as for the solid solution. A decrease in TC from 750 °C to 742 °C (solid solution at x = 0.1) was found. These results can be explained in terms of the perturbation of the oxygen octahedral perovskite layers resulting from the substitution of Ti4+ by Fe3+ ions.

The magnetoelectric coupling effect in multiferroic composites based on PZT–ferrite

In the multiferroic materials, the dielectric and magnetic properties are closely correlated through the coupling interaction between the ferroelectric and magnetic order. We attempted to determine the values of magnetoelectric coupling coefficient , from the temperature dependences of the dielectric permittivity for the ferroelectric–ferromagnetic composite PZT–ferrite type, namely PSZTC–NiZn and PBZTN–NiZn. The main component of the ferroelectric–ferromagnetic composite was PZT type powder (with ferroelectric properties), which was synthesized using sintering of a mixture of simple oxides in solid phase. The second element of the ferroelectric–ferromagnetic composite was the ferrite powder (with ferromagnetic properties). Ferrite powder was synthesized using calcination. Next, the mixed components were synthesized using sintering of the mixture of simple oxides in a solid phase (compaction by a free sintering method). The temperature dependences of the dielectric permittivity ( ε ) for the different frequencies and for both multiferroic composites were investigated. Based on dielectric measurements and theoretical considerations, the values of the magnetoelectric coupling coefficient were specified. • The magnetoelectric effect at two different ferroelectric–ferromagnetic composites based on a PZT and nickel–zinc ferrite. • Multiferroics composite incorporate both ferroelectric and magnetic phases. • The mechanism of the magnetoelectric coupling between ferroelectric and magnetic properties, in multiferroic composites, is caused by the strain. • The determination of the magnetoelectric coupling coefficient based on a theoretical model and the measurements of dielectric permittivity.

Dielectric dispersion and hydrogen bonding interactions study of aqueous D-mannitol using time domain reflectometry

The measurement of complex dielectric permittivity of binary mixtures of D-mannitol and water have been carried out in the frequency range of 10 MHz to 30 GHz using time domain reflectometry (TDR) technique. Measurements were done at different temperatures ranging from 5°C to 25°C for different weight fractions of D-mannitol (0 < WM ≤ 0.18) in water. The dielectric relaxation behaviour of these mixtures is explained using Cole–Davidson model. The dielectric parameters such as static dielectric constant and relaxation time for the mixtures have been evaluated. The activation energy decreases with increased D-mannitol content in the mixture. The molecular interaction between D-mannitol and water molecules is discussed using the Kirkwood correlation factor and Thermodynamic parameters.

Structural, magnetic, dielectric and optical properties of nickel ferrite nanoparticles synthesized by co-precipitation method

Nickel ferrite nanoparticles were synthesized by wet chemical co-precipitation method and the corresponding temperature dependent structural, magnetic and optical properties of these nanoparticles have been investigated. X-ray diffraction patterns show the single phase cubic spinal crystal structure belonging to the space group Fd3m. The average crystallite size varies in the range 8–20nm with varying sintering temperature. Raman spectroscopy exhibits a doublet-like peak behaviour which indicates the presence of mixed spinel structure. The saturation magnetization, coercivity and remanence increase with increasing sintering temperature from 250 to 550°C. The non-saturation and low values of magnetization at high fields indicate the strong surface effects to magnetization in NiFe2O4 nanoparticles. The g-value calculated from electron spin resonance spectrum indicates the transfer of divalent metallic ion from octahedral to tetrahedral site (i.e. mixed spinel structure). The dielectric permittivity, loss tangent and ac conductivity measurements show strong temperature dependence at all frequencies. The observed ac conductivity response suggests that the conduction in ferrite nanoparticles is due to feeble polaron hopping between Fe3+/Fe2+ ions. Room temperature UV–vis diffuse spectra indicate that NiFe2O4 is an indirect band gap material with band gap ranges from 1.27 to 1.47eV with varying sintering temperature. The photoluminescence study clearly indicates that the Ni2+ ions occupy both octahedral and tetrahedral sites confirming mixed spinel structure.

Dielectric spectra of water–oil-saturated porous media for the kHz range and determination of volume fractions of system components

The article presents a novel procedure of finding the water–oil ratio in a saturated porous medium by dielectric spectroscopy. Based on the study of experimental measurements of dielectric permittivity and the dielectric loss factor, it has been established that the dielectric spectrum in the kHz and MHz frequency range of the electromagnetic field in a porous medium saturated with fresh water is a characteristic symmetrical curve, whose symmetry may be distorted when oil is introduced into the system. The type of symmetry, degree of distortion, and corresponding physical mechanisms of polarization enable one to find the water–oil ratio without resorting to the mixture formulae traditionally used for finding the water–oil ratio in Maxwell–Wagner relaxation.

Structural Transition in the Perovskite-like Bimetallic Azido Coordination Polymers: (NMe4)2[B′·B″(N3)6] (B′ = Cr3+, Fe3+; B″ = Na+, K+)

Through in situ variable-temperature single-crystal X-ray diffraction analysis, a solid–solid structural phase transition induced by the successive displacements of the [NMe4]+ guest and a subsequent abrupt order–disorder transform for both the cationic guest and the cage-like framework was tracked in four perovskite-like bimetallic azido coordination polymers: (NMe4)2[B′·B″(N3)6] (B′ = Cr3+, Fe3+; B″ = Na+, K+). Such structural transition was also confirmed by differential scanning calorimeter measurement, variable-temperature powder X-ray diffraction analysis, and variable-temperature dielectric permittivity measurement, as well as molecular dynamics simulation. Conclusively, these compounds provide a good host–guest model for understanding and modulating the thermal motion behavior of the [NMe4]+ guest in various confined spaces constructed by the perovskite-like azido frameworks.

ЧАСТОТНЫЕ И ТЕМПЕРАТУРНЫЕ ЗАВИСИМОСТИ ДИЭЛЕКТРИЧЕСКОЙ ПРОНИЦАЕМОСТИ И ТАНГЕНСА УГЛА ПОТЕРЬ НЕКОТОРЫХ НЕМАТИЧЕСКИХ ЖИДКИХ КРИСТАЛЛОВ

The substances, capable to be in a liquid crystal state show the fluidity and anisotropy of properties and, as a result of it, easily change structure under the influence of external factors. By the preliminary researches made by a polarizing and optical method, it was revealed that connections form only a nematic liquid crystal phase. In work modern ideas of processes of formation of electric polarization, anisotropy in liquid crystals are studied. Depending on a temperature range in the studied samples dipole-group and dipole-segmental polarization may occur. Types (α and β) of the relaxation processes, lying on the basis of a method of dielectric spectroscopy are considered. The dielectric spectroscopy is one of the most effective methods of studying of molecular structure and intermolecular interaction in liquid crystal, polar substances. Modern methods of measurements and theories of permittivity and losses allow to connect in some cases their dependence on temperature and frequency of electric field with a structure, for example loudspeakers of molecules of liquid crystals. The technique of measurement of dielectric losses and permittivity of materials is described at various temperatures, frequencies and preparation of samples for measurements. Electric properties of liquid crystals at various temperatures are very important at creation of new technologies. Results of a experimental study of temperature dependence of dielectric parameters of three, earlier low-studied, connections in the temperature interval covering nematic and isotropic (near transition are presented to nematic) phases. The sign of dielectric anisotropy of a mesophase is defined by the magnitude and the direction of the molecular dipolar moment, anisotropy of polarizability, degree of orderliness of molecules and also a structure of supramolecular structures.

Structural, ferroelectric, and optical properties of Pb0.60Ca0.20Sr0.20TiO3, Pb0.50Ca0.25Sr0.25TiO3 and Pb0.40Ca0.30Sr0.30TiO3 thin films prepared by the chemical solution deposition technique

Perovskite ferroelectric Pb0.60Ca0.20Sr0.20TiO3, Pb0.50Ca0.25Sr0.25TiO3 and Pb0.40Ca0.30Sr0.30TiO3, thin films were deposited on Pt/Ti/SiO2/Si and (100) LaAlO3 substrates by a chemical solution deposition method. XRD revealed the formation of pure thin films on both substrates. All thin films have very flat surfaces, and no droplets were found on their surfaces. Raman data showed a gradual phase transition from tetragonal to a pseudocubic perovskite structure in these thin films; a simultaneous increase in Ca and Sr contents at room temperature was also observed. Temperature-dependent dielectric permittivity measurements revealed a decreasing ferroelectric-to-paraelectric phase transition temperature with increasing Ca and Sr contents. At 100kHz, ferroelectric-to-paraelectric phase transition temperatures were approximately 505, 355 and 290K for Pb0.60Ca0.20Sr0.20TiO3, Pb0.50Ca0.25Sr0.25TiO3 and Pb0.40Ca0.30Sr0.30TiO3 thin films, respectively. The Eg of the films were estimated from Tauc׳s law and were found to be inversely dependent on the Ca and Sr content amounts.

Effect of Ni(II) substitution on phase stabilization electrical properties of BICo(III)VOX.20 oxide-ion conductor

The BICO0.20–xNIxVOX solid electrolyte was synthesized by the standard solid-state reaction. The effect of Ni(II) substitution for Co(III) on phase stabilization and oxide-ion performance has been investigated in the compositional range 0 ≤ x ≤ 0.20 using X-ray powder diffraction, differential thermal analysis and AC impedance spectroscopy. The highly conductive γ′-phase was effectively stabilized at room temperature for compositions with x ≥ 0.13 whose thermal stability increases with Ni content. The complex plane plots of impedance were typically represented at temperatures below 380 °C, suggesting a major contribution of polycrystalline grains to the overall electrical conductivity. The dielectric permittivity measurements revealed the fact that suppression of the ferroelectric transition is compositionally dependent. Interestingly, the maximum ionic conductivity at lower temperatures (~2.56 × 10−4 S cm−1 at 300 °C) was observed for the composition with x = 0.13. The variation of low-temperature conductivity with Ni content was accompanied with a general drop in the corresponding values of ΔELT. However, the local minimum high-temperature conductivity, σ600 °C ~ 2.26 × 10−2 S cm−1 for x = 0.10, coupled with a local maximum value of ΔEHT ~ 0.48 eV was attributed to an increased defect trapping effect correlated with the V(V) → V(IV) reduction at elevated temperatures.

In situ measurement of pavement thickness and dielectric permittivity by GPR using an antenna array

We present a ground penetrating radar (GPR) system, which uses an antenna array for in situ measurements of the thickness and dielectric permittivity of an asphalt pavement layer. We calibrated the antenna array by considering the antenna phase center and the antenna offset. The results of the laboratory measurements demonstrate that the proposed calibration method can greatly improve the accuracy of the velocity and thickness estimations when compared with the conventional method. A field measurement conducted on a highway pavement shows that the error of the thickness estimation of the asphalt layer is less than 6mm (10%).

X-ray diffraction, dielectric and Raman spectroscopy studies of Ba1−xNd2x/3(Ti0.9Zr0.1)O3 ceramics

Polycrystalline samples of Ba1−xNd2x/3(Ti0.9Zr0.1)O3 (0≤x≤0.125) have been synthesized by high-temperature solid-state reaction technique. These ceramics were characterized by X-ray diffraction as well as dielectric permittivity measurements and Raman spectroscopy. The ceramic samples crystallize in the tetragonal perovskite structure for x=0 and in cubic for 0.025≤x≤0.125. Dielectric measurements showed that prepared compositions exhibit an evolution from a classical ferroelectric to a relaxor ferroelectric with rising substitution rate x. TC or Tm decreases when neodymium (Nd) is introduced in the lattice of Ba(Ti0.9Zr0.1)O3. A relaxor character with ΔTm=12K and ε'r about 11.650 at 1kHz with Tm=212K was found for Ba0.9Nd0.06(Ti0.9Zr0.1)O3 composition. The evolution of the Raman spectra was studied as a function of compositions and temperatures. The results of the Raman spectroscopy studies confirm our dielectric measurements.

Measurement of Dielectric Permittivity and Thickness of Snow and Ice on a Brackish Lagoon Using GPR

We examine the use of ground penetrating radar (GPR) to simultaneously estimate snow and ice thickness. Since velocity is essential for depth inversion, we developed an automatic common mid-point (CMP) measurement system, which can work in an ultra-wide band. Envelope velocity spectrum, robust in reflection identification, is used to estimate the dielectric permittivity and layer thickness from CMP datasets. We tested our system on two 50-m-long test lines on a brackish lagoon, i.e., Lake Saroma, in Hokkaido, Japan, in February 2012. The first test line failed due to the existence of a radar-absorbing layer of a mixture of snow and seawater between the snow cover and sea ice. The estimated dielectric permittivity of both snow and ice on the second test line seems to be highly correlated with their surface temperature. Compared with the ground truth, the snow and ice thickness estimations possess a good accuracy, with a respective mean absolute error of about 2 cm (12%) and less than 2 cm (4%), which verifies the accuracy of their dielectric permittivity estimation. Then the estimated two-layer velocity model obtained by interpolation was used to continuously estimate the snow and ice thickness from the common-offset (CO) GPR profile acquired by a commercial GPR system. Our system and method appear capable of accurately measuring the dielectric permittivity and thickness of other layered media.

Influence of a co-substituted A-site on structural characteristics and ferroelectricity of (Pb, Ba, Ca)TiO3 complex perovskites: analysis of local-, medium- and long-range order

Thin films of A-site co-substituted, PbTiO3 (PTO) by Ba2+ and Ca2+, i.e., PBCT70, PBCT60, PBCT50 and PBCT40 were fabricated on Pt/Ti/SiO2/Si substrates by chemical solution deposition. Structures of the samples were investigated from the viewpoint of local-, medium- and long-range order by X-ray absorption near structure (XANES), micro-Raman and infrared spectroscopies and by X-ray diffraction (XRD). The films thickness were determined by using field-emission scanning electron microscope. The experimental results demonstrate that BaO12 clusters are the critical dominant ferroelectricity cause in PBCT thin films rather than CaO12 clusters. XRD analysis which was applied to investigate the crystal symmetry indicates the absence of long-range structural distortion for samples at higher concentrations of Ba2+ and Ca2+. However, an analysis of structural medium- and local-range order such as infrared, micro-Raman and XANES spectroscopies revealed that symmetry changes are much more prominent; i.e., local structural distortions remain. Temperature-dependent dielectric permittivity measurements confirmed a decreasing ferroelectric-to-paraelectric phase transition temperature and showed a broad phase transition with an increase in BaO12 and CaO12 clusters. In addition, the lack of long-range polar ordering for the ferroelectric dipole caused by symmetry changes decreases the remanent polarization.

Polymorphism of Chiral Thioester Studied by Dielectric Spectroscopy

Spectroscopy A.I. Wawrzyniak, J. Chru±ciel, R. Douali, F. Dubois, J.-M. Leblond, Ch. Legrand, D.M. Ossowska-Chru±ciel, M. Marzeca,∗, P. Ropa, J.M. Czerwiec and S. Wrobel Jagiellonian University, Institute of Physics, W.S. Reymonta 4, 30-059 Krakow, Poland Institute of Chemistry, Siedlce University of Natural Sciences and Humanities, 3-go Maja 54, 08-110 Siedlce, Poland Universite du Littoral Cote d'Opale, 50 rue F. Buisson, B.P. 717, 62228 Calais, France (S)-(+)-4′-[(4-(1-methylheptyloxycarbonylphenyl) thiocarbonylphenyl]-decyloxybenzoate (in short 10.OPOSMH) was studied by complementary methods. The substance shows rich polymorphism. In addition to ferroelectric and antiferroelectric smectic C∗ phases it possesses three ferrielectric sub-phases. Phase transitions between the phases were revealed by di erential scanning calorimetry and static dielectric permittivity measurements. The aim of this paper was to study phase transitions and di erences in dielectric spectra shown by di erent phases. Collective and molecular dynamics of all phases shown by 10.OPOSMH will be discussed in terms of theoretical models. Dielectric spectra of antiferroelectric phase show two characteristic dielectric relaxation modes: one connected with the molecular process (reorientation around the short axis) and the other originating from uctuations of antiferroelectric order parameters.

Laboratory and field assessment of the capacitance sensors Decagon 10HS and 5TE for estimating the water content of irrigated soils

Capacitance sensors such as Decagon 10HS and 5TE are increasingly used for soil water content (θ) estimation. However, their reliability and limitations in clayey soils irrigated with saline waters have not been completely characterized under field conditions. Four levels of soil water content were combined with six levels of soil salinity in twenty-four pots to assess the performance of both sensors in a wide range of soil salinities. A simplified power-law dielectric mixing model was calibrated in the laboratory to estimate the θ of a clay loam soil from the measurements of apparent dielectric permittivity (ɛb) performed with both sensors. The calibrated equation was subsequently validated for the estimation of θ at two depths in six irrigated salt-threatened soils with clayey textures in SE Spain. The 10HS sensor provides higher estimations of ɛb than the 5TE. Besides, the 5TE sensor was more sensitive to soil salinity. Consequently, a different calibration was carried out for each sensor. When all the soil salinity treatments were included in the calibrations, the results were poor. However, for soil apparent electrical conductivities below 1.7dSm−1 the 5TE sensor could be calibrated with low prediction errors, and with the calibration parameters b0 and b1 very close to their characteristic values in clayey and mineral soils. In field testing, the 5TE sensors calibrated with the obtained equation provided average correct estimations with an error of ±0.05m3m−3. On the contrary, the 10HS sensor overestimated the soil water content by 0.07m3m−3 on average. The proposed simple calibration equation for the 5TE sensor can be reliably used under field conditions to estimate θ of irrigated clayey soils up to an apparent electrical conductivity of 1.7dSm−1.

Condensation of the atomic relaxation vibrations in lead-magnesium-niobate at T=T*

We present neutron diffraction, dielectric permittivity, and photoconductivity measurements, evidencing that lead-magnesium niobate experiences a diffuse phase transformation between the spherical glass and quadrupole glass phases, in the temperature interval between 400 K and 500 K, with the quadrupole phase possessing extremely high magnitudes of dielectric permittivity. Our analysis shows that the integral diffuse scattering intensity may serve as an order parameter for this transformation. Our experimental dielectric permittivity data support this choice. These data are important for the applications desiring giant dielectric responses in a wide temperature intervals and not related to electron's excitations.

Time domain reflectometry-measuring dielectric permittivity to detect soil non-acqeous phase liquids contamination-decontamination processes

Contamination of soils with non-aqueous phase liquids (NAPL) constitutes a serious geo-environmental problem, given the toxicity level and high mobility of these organic compounds. To develop effective decontamination methods, characterisation and identification of contaminated soils are needed. The objective of this work is to explore the potential of dielectric permittivity measurements to detect the presence of NAPLs in soils. The dielectric permittivity was measured by Time Domain Reflectometry method (TDR) in soil samples with either different volumetric content of water (􀀅w) and NAPL (􀀅NAPL) or at different stages during immiscible displacement test carried out with two different flushing solutions. A mixing model proposed by Francisca and Montoro, was calibrated to estimate the volume fraction of contaminant present in soil. Obtained results, showed that soil contamination with NAPL and the monitoring of immiscible fluid displacement, during soil remediation processes, can be clearly identified from dielectric measurements.

In situ measurement of snowmelt infiltration under various topsoil cap thicknesses on a reclaimed site

Christensen, A. F., He, H., Dyck, M. F., Turner, L., Chanasyk, D. S., Naeth, M. A. and Nichol, C. 2013. In situ measurement of snowmelt infiltration under various topsoil cap thicknesses on a reclaimed site. Can. J. Soil Sci. 93: 497–510. Understanding the soil and climatic conditions affecting the partitioning of snowmelt to runoff and infiltration during spring snow ablation is a requisite for water resources management and environmental risk assessment in cold semi-arid regions. Soil freezing and thawing processes, snowmelt runoff or infiltration into seasonally frozen soils have been documented for natural, agricultural or forested systems but rarely studied in severely disturbed systems such as reclaimed lands. The objective of this study was to quantify the snowmelt infiltration/runoff on phosphogypsum (PG) tailings piles capped with varying thicknesses of topsoil (0.15, 0.3, and 0.46 m) at a phosphate fertilizer production facility in Alberta. There are currently no environmental regulations specifying topsoil capping thickness or characteristics for these types of tailings piles. Generally, the function of the topsoil cap is to facilitate plant growth and minimize the amount of drainage into the underlying PG. Experimental plots were established in 2006 to better understand the vegetation and water dynamics in this reconstructed soil. In 2011, time domain reflectometry (TDR) probes and temperature sensors were installed at various depths for continuous, simultaneous, and automated measurement of composite dielectric permittivity (ɛeff) and soil temperature, respectively. An on-site meteorological station was used to record routine weather data. Liquid water and ice content were calculated with TDR-measured effective permittivity (ɛeff) and a composite dielectric mixing model. Spatial and temporal change of total water content (ice and liquid) revealed that snowmelt infiltration into the topsoil cap increased with increasing topsoil depth and net soil water flux from the topsoil cap into the PG material was positive during the snowmelt period in the spring of 2011. Given the objective of the capping soil is to reduce drainage of water into the PG material it is recognized that a capping soil with a higher water-holding capacity could reduce the amount of meteoric water entering the tailings.