Dielectric Constant Of Samples Research Articles

Bottom-up synthesis of novel cesium ferrate (Cs2FeO4) nanorods: Tailoring the structural and optical characteristics with room-temperature ferromagnetic and colossal dielectric performance

This paper presents a detailed protocol for the synthesis and characterization of cesium ferrate nanorods, a unique material that possesses a wide range of functionalities. These include the ability to demonstrate ferromagnetism at normal ambient temperature and the capacity to modify its structural, optical, and electrical properties. The XRD patterns specify the presence of an orthorhombic alkali ferrate phase (Cs2FeO4), with the size of the crystals increasing as the temperature rises. Furthermore, the XPS spectra of Cs 3d, Fe 2p, and O 1 s exhibit the formation of substances due to the peak positions fluctuate in reaction to temperature variations. The nanorod-like structure and size distribution of materials can be visualized using TEM and SEM. The UV spectra of the samples indicate broad absorption bands ranging from the visible to the near infrared (IR) region. Calcination of the as-prepared Cs2FeO4 at 400 and 600 ºC lowered the optical band gap from 2.15 to 2.04 and 2.06 eV, respectively. The temperature's synergistic effect is crucial in transforming materials from a paramagnetic to a ferromagnetic phase. The colossal sample's dielectric constant, which varies from around 107 at 600 ºC to 106 and 105 in the lower frequency band, and electrical conductivity show substantial fluctuations depending on the frequency. Nanorod systems have interesting optical, dielectric, and ferromagnetic properties at room temperature that could be used in many areas, such as photocatalysis, energy storage, and spintronics.

Synthesis, magnetic and dielectric properties of poly(m-phenylenediamine)/ZnNiFe2O4 nanocomposites

The different concentration of ZnNiFe2O4 nanoparticles dispersed Poly(m-phenylenediamine) (PmPD)/ZnNiFe2O4 nanocomposites were synthesized by in-situ chemical oxidative polymerization method and using auto combustion method for preparation of ZnNiFe2O4 nanoparticles. The synthesized PmPD/ZnNiFe2O4 nanocomposites were characterized by XRD, FTIR, SEM, TEM, TGA and VSM. The formation and crystalline size of PmPD/ZnNiFe2O4 nanocomposites were confirmed through XRD and FTIR. The surface, morphology and shape of the PmPD/ZnNiFe2O4 nanocomposites were studied by SEM and TEM. The concentration of ZnNiFe2O4 influenced the thermal stability of PmPD/ZnNiFe2O4 nanocomposites. The hysteresis loop of ZnNiFe2O4 and PmPD/ZnNiFe2O4 nanocomposites confirmed their ferromagnetic behaviour. The dielectric constant of samples was analysed with different temperatures and frequencies.

Structural, dielectric and magnetic properties of Nickel-Chromium substituted Magnesium ferrites, Mg1–Ni Fe2-xCrxO4 (0 ≤ x ≤ 0.7)

In this paper, we report the structural, dielectric, and magnetic properties of Mg1–xNixFe2-xCrxO4 (0 ≤ x ≤ 0.7) ferrites synthesized via a solid-state process. The XRD patterns indicated forming a single-phase cubic spinel structure with a Fd-3 m space group for all samples with crystallite sizes ranging from 31.63 to 73.52 nm. Scanning Electron Microscopy (SEM) showed the formation of dense microstructure with an average grain size of 129.2 to 414 nm. The elemental analysis (EDS) confirmed the chemical purity for all the prepared samples. The saturation magnetization (Ms) was found to be maximum for the composition x=0.3, after which it decreased due to the lower magnetic moment of Cr3+ ion (3 μB) than that of Fe3+ ion (5 μB). The samples' maximum magnetic saturation and coercivity are 62.04 emus/gm and 6.8 KOe, respectively. The measured sample's dielectric constant (ε') and loss tangent (tan δ) decreased with the increased applied field frequency, showing normal behavior. This can be explained in light of Maxwell–Wagner interfacial polarization and hopping of electrons between the Fe2+ ↔ Fe3+ ions. Thus, the synthesized Ni-Cr substituted MgFe2O4 ferrite material is promising for recording materials.

Estimation of S-parameters and dielectric permittivity of quartz ceramics samples in millimeter waveband

A modified Nicholson – Ross – Weir method was used to determine complex parameters and dielectric permittivity of ceramic materials in the range 78.33–118.1 GHz. The measuring equipment is a meter of complex reflection and transmission coefficients, a waveguide measuring canal with a special measuring cell, consisting of two irregular waveguides and a waveguide chamber between them, which provides insignificant influence of higher-order modes. The dependences of the amplitude and phase of the reflection and transmission coefficients on frequency were obtained experimentally for fluoroplastic and three ceramic samples in the frequency range 78.33–118.1 GHz. The obtained S-parameters are processed according to an algorithm that includes their averaging based on the Fourier transform in order to obtain the values of the dielectric permittivity. Fluoroplastic was used as a reference material with a known dielectric constant. The dielectric constant of fluoroplastic has a stable value of 2.1 in the above mentioned frequency range. The dielectric constant of sample No. 1 varies from 3.6 to 2.5 at the boundaries of the range, sample No. 2 – from 3.7 to 2.1, sample No. 3 – from 2.9 to 1.5. The experimental data are in satisfactory agreement with the literature data for other frequencies taking into account the limits set by the measurement uncertainty.

Morphological and magnetic features of columnar nanostructures CuO

Columnar nanostructures (CNS) were grown by plasma chemical synthesis at a gas mixture pressure of 90% He + 10% O2 200 Pa and substrate temperatures of 340K (sample 1) and 370K (sample 2). The effect of substrate temperature on the morphological, crystalline, magnetic, and impedance properties of CNS was studied. Scanning microscopy (SEM) showed that the morphology of CNS varies significantly from dendritic to wire structure. Energy dispersive X-ray spectroscopy (EDS) showed a change in the stoichiometry of the deficiency samples (Cu52O48) to an excess of oxygen (Cu42O58). X-ray diffraction analysis (XRD) and Rietveld fitting showed that samples 1 and 2 have a monoclinic crystal structure with a large proportion of the amorphous phase, the size of coherent scattering regions (CSR) was 26 nm (sample 1). Magnetic measurements showed that sample 1 exhibits ferromagnetic behavior, and at 6 K a magnetic hysteresis loop appears. Sample 2 from 250 K to room temperature exhibits diamagnetic behavior. A connection was found between the appearance of diamagnetism and a jump in the dielectric constant of sample 2. An assumption was made about the electron-ionic nature of the diamagnetism of sample 2.

Single resonator microwave device for monitoring the complex dielectric constant of liquid fuels and lubricants

A simplified structural diagram of a single-cavity microwave dielectric meter designed to control the complex permittivity of liquid fuels and lubricants is presented. The structural diagram of the microwave sensor of the dielectrometer, made in the form of a parallelepiped, inside which waveguide paths, a resonator, controlled and reference generators, mixing and detector diodes and attenuators is considered. A general view of the lower part of the microwave sensor housing is given.
 The technique of initial tuning of the microwave sensor is considered, during which the initial frequencies of the controlled and reference oscillators are set and the range of electronic frequency tuning of the frequency of the controlled generator is determined.
 A method for calibrating a dielectrometer with an empty cuvette is presented. This method makes it possible to determine the suitability of the cuvette for its use in measuring the complex dielectric constant of samples of fuels and lubricants, and to exclude the influence of the dispersion of the dielectric constant of the material of the cuvette on the results of measuring the complex dielectric constant of fuels and lubricants.
 The technique of studying the parameters of samples of fuels and lubricants is considered, based on which the measurement data are presented on a complex plane for analyzing the results obtained.
 A technique for studying the difference between a fuel and lubricant sample and its standard is presented, which includes measuring the parameters of an empty cell, measuring the real and imaginary components of the complex dielectric constant of the fuel and lubricant sample and its standard, and analyzing the differences between their real and imaginary components on a complex plane.

Analysis of Polarimetric Decomposition, Backscattering Coefficient, and Sample Properties for Identification and Layer Thickness Estimation of Silica Sand Distribution Using L-Band Synthetic Aperture Radar

Silica is one of the mineral needs of industry, especially in base materials for the primary or auxiliary raw materials. Silica sand on Rupat Island was identified on the northern coastline. Selected samples were measured to get the percentage of minerals/elements using X-ray fluorescence. Two adjacent scenes of ALOS PALSAR full-polarimetry data were used. The dielectric constant of samples was measured using a dielectric probe kit in the frequency range from 0.3 to 3.0 GHz and also used for calculating the backscattering coefficient. Freeman-Durdeen and Yamaguchi techniques were used to obtain the scattering decomposition of physical scattering from the incoherent object model base. Surface scattering is a very clear decomposition used to show the silica sand identification compared with other decompositions. From surface scattering, the backscattering coefficient value of silica sand resulted from −59 dB to −52 dB. Thickness estimation from satellite and field measurements show the minimum is 59 cm and the maximum is 74 cm, with the average differentiation between these measurements being 4.88 cm. The condition supported by the grain size of silica sand particles that have almost the same size and shape were conducted by using microscopic photograph testing. These values were caused by a slightly rough surface.

Materials classification by partial least squares using S-parameters

This paper presents a simple and usable algorithm, which is called Partial Least Squares, to classify the samples in different thicknesses and frequency range. This model employed to reconstruct the samples using S-parameters which are collected by Vector Network Analyzer in Free Space Measurement method. The relationship of between S-parameters is showed to classify the materials using proposed model. The Partial Least Squares algorithm has a good potential to classify the different samples with non-contactless and non-destructive measurement method. The classification process will be easy by using the proposed model, due to its practical and simple usage. In addition, the extraction techniques, which are Nicolson Ross Weir, Newton–Raphson, and Genetic Algorithm, are used in order to extract the dielectric constant of samples, in this study. The Newton–Raphson algorithm is selected to obtain the complex permittivity of samples since it gives best results than other extracting techniques and the results are used for classification.

Effect of nano-BaTiO3 on thermal, mechanical, and electrical properties of HDDA/TPA photopolymer prepared by a digital light processor RP machine

Abstract The acrylate-based photopolymer consists of tetra-functional polyester acrylate (TPA), and hexanediol diacrylate (HDDA) has been successfully composited with nano barium titanate (BaTiO3) and completely cured via a digital light processor RP machine. The degradation temperature, tensile strength, hardness, resistivity, and dielectric constant of samples were characterized by Thermo Gravimetric Analyzer Hi-Res TGA2950, Universal Tensile Machine JIA701, Hardness Shore D tester, Fluke 117 multimeter, and Agilent B1500A Semiconductor Device Analyzer, respectively. The morphology changes of the samples were also investigated using the JEOL JSM-6390LV scanning electron microscopy (SEM). The results show that the improvement of degradation temperature is not obvious. Furthermore, the modulus elasticity, hardness, and dielectric constant increase as the filler loading increases up to 2 phr, but the resistivity is vice versa. Interestingly, there is an inverse correlation between dielectric constant and resistivity of photopolymer/BaTiO3 nanocomposite.

Optical properties of the different tapered silicon nanowires based on KK relation

The optical properties of the various types of tapered silicon nanowires (SiNWs) have been investigated by the phase retrieving method of utilizing the experimental reflection spectra with the aid of the Kramers–Kronig (KK) relation. The effective refractive index (n) and the extinction coefficient (K) of each tapered SiNWs and combined silicon nanowires and microwires (CNMW) array samples can be obtained from concrete simulation by the KK relation. At the same time, we can also obtain the real part (ε′) and imaginary part (ε″) of the effective complex dielectric constant from the relation between the refractive index and the complex dielectric constant of samples. And the simulated results show that the relative material parameters (effective complex refractive index, effective complex dielectric function) can be modulated from a concrete material processing.

Effect of different forms of silica on sintering, microstructure and properties of borosilicate glass/Al2O3 composites

The effects of the introduction of silica glass and silica ceramic into Ca-Al-B-Si-O glass/ Al2O3 composites on decreasing the shrinkage and the dielectric constant of samples were investigated by FTIR, DSC, XRD and SEM. The results show that silica ceramic filler can better improve the formation of Si-O-Si network in the composites under high temperature, which leads to increased continuity of glass network at high temperature, and deduces the increase of viscosity of composites and further results in the decrease in the shrinkage of samples. Densification, three-point strength, and dielectric constant of samples decrease with the increase of silica glass or silica ceramic content. By contrast, Ca-Al-B-Si-O glass/Al2O3 composites with 4 wt% silica ceramic exhibit better properties of a bulk density of 2.81 g·cm−3, a porosity of 0.3%, a 3dp value of 202 MPa, a ɛ r value of 7.41, a tan δ value of 8.3×10−4 at 10 MHz and a well matching with Ag electrodes. This material is suitable to be used as the LTCC material for the application in wireless communications.

Low temperature sintering and properties of Ca–Al–B–Si–O glass/ceramic composites with various ceramic fillers

Low-temperature sintering and properties of low temperature co-fired ceramics materials based on a typical Ca–Al–B–Si–O glass and various ceramic fillers such as (Zr0.8Sn0.2)TiO4, (Ca0.5Mg0.5)TiO3, BaSm2Ti4O12 and CaTiO3 were investigated. Densification, crystallization and dielectric properties are found to strongly depend on the type of filler. The densification process of glass/ceramic composites with different ceramic fillers is mainly from 600 to 925 °C, and the initial compacting temperature of samples is 600 °C. The initial rapid densification of samples starts after glass softening temperature of samples. The XRD patterns of (Ca0.5Mg0.5)TiO3 and CaTiO3 samples demonstrate crystalline phases, CaTiO(SiO4) and CaTiSiO5, respectively, as a result of firing at 875 °C for 15 min. The high dielectric constant fillers produce high er values of the dielectric samples. The maximum dielectric constant of samples for (Zr0.8Sn0.2)TiO4, (Ca0.5Mg0.5)TiO3, BaSm2Ti4O12 and CaTiO3 filler is 14.02, 16.21, 18.64 and 23.78, respectively. Comparing with other samples, the specimens for (Ca0.5Mg0.5)TiO3 and CaTiO3 ceramic filler have lower dielectric loss. Especially, the sample for (Ca0.5Mg0.5)TiO3 filler exhibits the lowest dielectric loss of 0.00011.

High Frequency Dielectric Properties and Thermal Conductivity of AlN-BN Composites by Spark Plasma Sintering

AlN-BN composite is considered to be a promising material for microwave transparent applications. In this paper, a series of AlN-BN composites with various content of BN (0 wt%, 5 wt%, 15 wt% and 30 wt%) were prepared by spark plasma sintering with multiple components sintering additives at a low temperature (1650 °C), and the effect of sintering conditions and composition on the thermal conductivity and high frequency dielectric properties within frequency range from 10 MHz to 1.5 GHz was investigated. The results show that the spark plasma sintering process and the multiple components of the sintering additives promote the densification of the samples. The thermal conductivity and dielectric constant of samples decrease with increasing BN content, while the variation of the dielectric loss depends on the content of residual carbon and other impurities which may result in the relaxation loss of electronic polarization and conductive loss.

Effect of Glass Additive on Electrical Properties of PLZST Antiferroelectric Ceramics

Alkali-free barium boroaluminosilicate glass-modified PLZST antiferroelectric ceramics with glass contents between 0 and 8 wt.% have been fabricated respectively by a traditional solid phase reaction. The PLZST ceramics doped with alkali-free barium boroaluminosilicate glass showed typical antiferroelectric phase when the glass contents were below 6 wt.% and the refined grains were observed. The addition of glass decreased the dielectric constant of samples. With increasing of the glass additives, both the Curie temperature and the remanent polarization deceased. It may be that Ba2+entered in the perovskite structure, which acts as an important modified ion in the alkali-free barium boroaluminosilicate glass. Larger forward antiferroelectric-ferroelectric phase transition field (EAFE-FE>50 kV/cm) and higher breakdown strength (EBDS≥105 kV/cm) were displayed in glass-modified PLZST ceramics. The improvement properties of samples were benefit for energy storage which is desired for the high power energy storage capacitors and pulsed power applications.

Effects of substitutions of Nd3+ for Sr2+ on the properties of SrBi2Nb2O9 ceramics and their mechanism

（Sr1-3x/2Ax/2Ndx）Bi2Nb2O9 （x=0，0.05，0.1 and 0.2） ceramics are prepared by traditional solid-reaction method， and effects of substitutions of Nd3+ for Sr2+ on the properties of SrBi2Nb2O9 ceramics and their mechanism are investigated. The results show that the temperature spectra of dielectric constant and loss for these Nd-doped samples are obviously characteristic of ion relaxor polarization. The partial substitution of Nd3+ for Sr2+ leads to the slight reduction in remanent polarization （Pr） and the increase in piezoelectric coefficient d33， which can be attributed to the increase in dielectric constant of samples according to ferroelectric thermodynamics theory. Raman spectrum shows that no change in the Curie temperature （TC） of （Sr1-3x/2Ax/2Ndx） Bi2Nb2O9 samples is observed， which might result from no appreciable variation in NbO6 octahedron distortion. For （Sr1-3x/2Ax/2Ndx） Bi2Nb2O9 ceramics， the substitution of Nd3+ for Sr2+ increases permittivity εr， piezoelectric coefficient d33，and electromechanical coupling coefficient Kp and reduces mechanical quality factor Qm, but it does not change temperature coefficient of harmonic frequency value.

Apparent contrast of molecularly thin films of water at ionic crystal surfaces

We focus the apparent contrast of water islands formed at ionic crystal surfaces in air at room temperature (RT) using the non-contact monitoring mode of a scanning force microscope (SFM). Their apparent heights of water islands formed on LiF(001), CaF 2(111) and BaF 2(111) surfaces have been measured to be about 2, 1 and 1 nm, respectively. The water growth of a NaF(001) surface has two phases (phase I and phase II). The apparent heights of phase I and phase II have been measured to be about 2 and 1.5 nm, respectively. The apparent height of water films is shown to be strongly modified by the dielectric constant of sample and water, and the true thickness of water islands is discussed.

Raman investigation on (Ta 2O 5) 1−x(TiO 2) x system at different temperatures and pressures

Micro Raman spectra for (Ta 2O 5) 1−x(TiO 2) x reveal an induced Raman enhancement of the low frequency phonon modes for a critical TiO 2 content, x = 0.08. The temperature and pressure effects on these modes have also been studied. The Raman enhancement is shown to be associated with effects of the superstructure which is composed of TiO 6 octahedra and Ta-O clusters. Pressure Raman scattering on (Ta 2O 5) 0.92(TiO 2) 0.08 indicates that a phase transition occurs at ~6.22 Gpa. Based on our Raman scattering studies, the origin responsible for the enhanced dielectric constant in samples with TiO 2, content, x = 0.08, has been provided and discussed.

The grain size, dielectric properties and impedance spectroscopy in a modified ternary system of Pb(Zr, Ti)O3

The Pb(Zr, Ti)O3 (PZT) modified ternary ceramics prepared by standard ceramic techniques were studied in the early 1970s. Recently much attention has been devoted to PbB9B0O3 –PbZrO3 –PbTiO3 ternary systems where cations B9 and B0 substitute for Ti or Zr ions in the perovskite phase. In another report [1] the Pb(Mg, Nb)O3 –PbTiO3 –PbZrO3 system where B9 ˆ Mg and B 0 ˆ Nb [2–4] was studied. The electrical and electromechanical properties were compared between the samples obtained by the standard ceramic technique and the samples obtained using columbite as the precursor. The densities, electromechanical couplings and dielectric constants of samples prepared using the columbite were better than those prepared using the simple ceramic method, for the same conditions. The kinetics of grain growth for the two methods were quite different; however, the lower dielectric constant of the samples prepared using the simple ceramic method was affected considerably by their lower density. The sintered ceramics were useful in application such as accelerometers and infrared sensors in which high values of d33 and dielectric constant are important parameters. Similar properties have been reported by chemical techniques [5, 6]. Both samples showed a perovskite rhombohedral phase (reticular parameters: a ˆ 4:063 A; AE ˆ 89:928). In this paper we analyse the temperature dependence of the dielectric properties for the same prepared system by using the better technique reported by Perez et al. [1] (columbite precursor method). The raw materials were mixed with MgNb2O6 powder in order to obtain the nominal composition Pb(Mg1=3Nb2=3)0:375Ti0:375Zr0:25O3 ‡ 0:5 mol% NiO‡MnO2 and were calcined at 900 8C for 2 h. The pressed powder were sintered at 1200 8C for 2 h. The dielectric losses were measured using a PM6303 RLC bridge, and alternating current impedance measurements were carried out using a Hewlett–Packard HP 4192 impedance analyser controlled by a HP-85 microcomputer. The frequency range was from 5 Hz to 13 MHz. The applied voltage was 1 V in each measurement. The dependence of the losses with the temperature, measured at 1 kHz, is shown in Fig. 1. This dependence shows that the substitution of (Zr, Ti) for Mg2‡ and Nb5‡ does not increase the conductivity of samples. The real values up to 100 8C permit us to consider these materials for application in electronic devices in the range in which there are

Modified Method of Measuring Dielectric Constants

AbstractA modification is made to the method of measuring dielectric constants developed by Sinha and Brown. The mismatch occurring between the empty and the partially filled portions of the cavity is removed by putting a quarter-wavelength matching section at the end of the rod specimen. This considerably simplifies the system which becomes much easier to handle theoretically. Also, the computational labour in the evaluation of loss tangent is considerably reduced. The main advantage, however, of this modified method is the ability to measure the dielectric constants of samples having lengths less than half a wavelength, a facility not available with the original method.