Papers by Keyword: Complex Impedance

Abstract: A-site Mn-doped La_1-xMn_xTiO_3+δ and B-site doped LaMn_xTi_1-xO_3+δ (x = 0.1, 0.2) composites were synthesized by conventional solid-state reaction method. The low-frequency complex dielectric properties of the composites were investigated as functions of temperature (77 K ≤ T ≤ 360 K) and frequency (100 Hz ≤ f ≤ 1 MHz), respectively. The dielectric constants of A-site doped samples are higher than that of B-site doped samples. The loss tangents of the low doped samples are much less than that of the high doped samples. The A-site doped composites exhibit intrinsic dielectric response with a dielectric constant of ~40 in the temperature below 250 K. Interestingly, the dielectric constants of B-site doped composites always increased in the temperature range from 77 to 360 K. And it is clearly observed that extraordinarily low dielectric loss tangents appear in LaMn_0.1Ti_0.9O_3+δ, which are much lower than that of LaMn_0.2Ti_0.8O_3+δ. These changes indicate that the doped content can affect the intrinsic dielectric characteristics significantly.

Abstract: Lithium ion batteries have become a popular power source for portable electronic equipments. It is found to be superior in gravimetric energy density as it provides about 1.5 times more energy compared to nickel hydride battery. In this study, Polyethylene Oxide based polymer electrolytes were used for investigation. PEO based solid polymer electrolyte films were prepared by solution casting technique with different concentration of salt and different %wt of zirconia nanofiller. The X-ray diffraction analysis was carried out for the identification of compounds available in the sample and to determine the relative concentrations by the intensities of pattern lines. Also the superposition of absorption bands of specific functional groups was confirmed with the infra-red spectrum of FTIR. The Complex Impedance Spectroscopy technique was further used to measure the cell admittance / impedance in a wide range of frequencies and analyzed in the complex admittance/ impedance plane. From the impedance test results it is observed that the conductivity of polymer electrolyte was improved from 7.39×10−4 Scm−1 to 5.24×10−3 Scm−1 after adding 3%wt of ZrO₂ nanofiller with pure polymer. Set up of nano Lab is rare, new and uncommon. It is also an emerging technology. Fabrication of powder needs extra machines which are not popular among common people. It will become popular in the coming future. When particle size is reduced, the quantity of powder is reduced, quality is increased.

Abstract: Conditions for the formation of (1-x)BaTiO₃–xLi_0.5Bi_0.5TiO₃ (0 ≤ x ≤0.6) solid solutions with positive temperature coefficient of resistance (PTCR) effect were studied. Solid solutions were prepared by solid state reaction technique. Samples were sintered under reducing atmosphere N₂/H₂ in the temperature range 1200–1450 °C with subsequent oxidation in air. The phase composition was investigated by X-ray powder diffraction method. It was found that samples of (1-x)BaTiO₃–xLi_0.5Bi_0.5TiO₃ (0 ≤ x ≤0.6) solid solutions at room temperature exhibit perovskite structure. Unit cell parameters of unstable at the room temperature compound Li_0.5Bi_0.5TiO₃ were determined by extrapolation of concentration dependence of the unit cell parameters in the (1-x)BaTiO₃–xLi_0.5Bi_0.5TiO₃ system. It was shown that minimum value of resistivity ρ_min rises with increase in x value. Complex impedance method shown that ceramic grains of (1-x)BaTiO₃–xLi_0.5Bi_0.5TiO₃ materials consist of three areas with different electrical properties. Boundary and outerlayer region of grains make the main contribution to the PTCR effect in lithium-containing solid solutions. It was shown that magnitude of the potential barrier's decreases with increasing x.

Abstract: Consideration of radial inhomogeneity of soil, an analytical solution to horizontal vibration of pile in radial inhomogeneous soil is deduced, and the parameters influencing the horizontal vibration characteristics of the pile in radial inhomogeneous soil is analyzed carefully. The number of the radial layers of the inner soil, the thickness of the inner soil, the weakened degree and the ratio of length and radius can obviously affect complex impedance of the top of the pile. Before analyzing horizontal vibration of pile, choice a reasonable number of the radial layers of the inner soil and proper thickness of the inner soil, which is crucial. The more is the weakened degree of the inner soil, the stronger the fluctuations of horizontal vibration of pile are. The ratio of length and radius can influent horizontal vibration of pile within a certain range.

Abstract: In this paper, a nondestructive technique is used as a tool to control cracks and microcracks in materials. A simulation by a numerical approach such as the finite element method is employed to detect cracks and eventually; to study their propagation using a crucial parameter such as the stress intensity factor. This approach has been used in the aircraft industry to control cracks. Besides, it makes it possible to highlight the defects of parts while preserving the integrity of the controlled products. On the other side, it is proven that the reliability of the control of defects gives convincing results for the improvement of the quality and the safety of the material .

Abstract: This paper aims at proving the complex impedance of the inductor and capacitor elements and applying the proved complex impedance concept to directly obtain the transfer function model of the complicated circuit network. Based on Laplace Transformation method, the complex impedances of the inductor and capacitor elements are proved. Using the proved complex impedances and the equivalent complex impedances in series and in parallel, both the transfer functions of the passive and active circuit networks are modeled. This facilitates the transfer function modeling of the complicated circuit network very much.

Abstract: In this paper, a nondestructive technique is used as a tool to control cracks and microcracks in materials. A simulation by a numerical approach such as the finite element method is employed to detect cracks in materials and eventually to study their propagation using a crucial parameter such as the stress intensity factor. This approach has been used in the aircraft industry to control cracks. Besides, it makes it possible to highlight the defects of parts while preserving the integrity of the controlled products. On the other side, it highlights the reliability of the control of defects and gives convincing results for the improvement of the quality and the safety of the material.

Abstract: The dielectric and electric properties of poly (methyl Methacrylate) (PMMA) and Poly (vinyl Pyrrolidione) (PVP) in polar solvent have been studied in the frequency range of 20 Hz to 2 MHz at room temperature. The effect of polar solvent environment on the dielectric and electrical parameters such as the complex dielectric constant (Є*), relaxation times complex electrical modulus (M*) and complex impedance (Z*) has been analysed . Dielectric dispersion curves show that the polymer concentration plays an important role in governing its segmental motion in solvent solution. At low frequencies, the ionic conduction and electrode polarization seems to have dominant influence on the large increase of complex dielectric constant values.

Abstract: The complex relative dielectric function ε*(ω) = ε’- jε” of anisole (AN), 1-heptanol (1-HeOH) and their binary mixtures of varying concentration have been measured using Precision LCR meter in the frequency range 20 Hz to 2 MHz at 303 K. The electrical/dielectric properties of the liquid samples are represented in terms of intensive quantities namely, complex relative dielectric function ε*(ω), electrical modulus M*(ω), electrical conductivity σ*(ω) and extensive quantities, i.e. complex admittance Y*(ω) and complex impedance Z*(ω). All of these presentations are used to explore various processes contributed in the electrical/dielectric properties of the mixtures of two polar liquids.

Abstract: We have investigated of composite (1-x)Ba_0.5Sr_0.5Fe_11.7Mn_0.15Ti_0.15 / xLa_0.7Ba_0.3MnO₃ by conventional ceramic method. The sturcture of composite and complex impedance are carried out by XRD, SEM and Impedance Spectroscopy. With changing the weight ratio from x=0; 0.3; 0.5 and x=1 the phase exhibit the composite behavior. Very interestingly, for the case of the case of weight ratio x=0.5 and 0.7 showed the complex impedance with xemicircle pattern in frequency range from 1 KHz to 1 MHz.