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Abstract

Nondoped BiFeO3 (BFO) and doped Bi0.9La0.1Fe0.9Mn0.1O3 (BLFMO) thin films (d = 200–350 nm) were grown at 650–750 °C by RF sputtering on Si and SrTiO3(100), coated by conductive LaNiO3 films and La2/3Ca1/3MnO3/SrRuO3 bilayers. The complex dielectric permittivity of the films was measured at room temperature in the frequency range from 10 MHz to 10 GHz using parallel plate capacitor structures. Dielectric properties of the polycrystalline BFO films were compared with those of the epitaxial quality BLFMO films, and it was seen that the latter has better microwave performance than the former. The dielectric losses were below 0.05 at 1 GHz frequency, which may be acceptable for microwave applications.

Abstract

In this paper we present the results of investigations into ceramic samples of solid solution (1-x)(PbZr0.53Ti0.47O3)- x(PbFe0.5Ta0.503) (i.e. (1-x)PZT-xPFT) with x = 0.25, 0.35 and 0.45. We try to find the relation between the character of dielectric dispersion at various temperatures and the composition of this solution. We also describe the magnetic properties of investigated samples. With increasing the content of PFT also mass magnetization and mass susceptibility increase (i.e. magnetic properties are more pronounced) at every temperature. The temperature dependences of mass magnetization and re­ciprocal of mass susceptibility have similar runs for all the compositions. However, our magnetic investigations exhibit weak antiferromagnetic ordering instead of the ferromagnetic one at room temperature. We can also say that up to room tempera­ture any magnetic phase transition has not occurred. It may be a result of the conditions of the technological process during producing our PZT-PFT ceramics.

Abstract

Pure and cobalt doped (x = 0.05, 0.10, 0.15 mol %) polycrystalline potassium hexatitanate (K2Ti6O13) ceramics were synthesized using conventional solid state reaction route. XRD result confirmed the successful doping of Co in the K2Ti6O13 matrix, as no additional peak was observed in the pattern. Dielectric permittivity was found to decrease with the increase in frequency while it increased with the increase in doping. The dielectric loss decreased with small doping whereas excessive doping caused its augmentation. Ac conductivity (σac) has also been studied as a function of frequency at room temperature for all the samples. Scanning Electron Microscope (SEM) inspection of the synthesized samples showed the formation of rod like shapes. FTIR analysis was carried out to identify the chemical bonds present in the system.

Within the theory of linear magnetoelectroelasticity, the fracture analysis of a magneto - electrically dielectric crack embedded in a magnetoelectroelastic layer is investigated. The prescribed displacement, electric potential and magnetic potential boundary conditions on the layer surfaces are adopted. Applying the Hankel transform technique, the boundary - value problem is reduced to solving three coupling Fredholm integral equations of second kind. These equations are solved exactly. The corresponding semi - permeable crack - face magnetoelectric boundary conditions are adopted and the electric displacement and magnetic induction of crack interior are obtained explicitly. This field inside the crack is dependent on the material properties, applied loadings, the dielectric permittivity and magnetic permeability of crack interior, and the ratio of the crack length and the layer thickness. Field intensity factors are obtained as explicit expressions.

Abstract

One of important problems in aerospace engineering is to determine the amount of fluid in the tank in a microgravity environment. There are several methods for doing it, however, there are no proven methods to quickly gauge the amount of propellant in a tank in low gravity conditions. New and more accurate methods of such a measurement are being continually searched for. One of interesting solutions is using Electrical Capacitance Tomography (ECT) for this purpose. The article presents both numerical analysis and experimental test results using a spherical tank. The main purpose of the simulation was to determine the effect of the number of electrodes and noise signal level on the quality of reconstruction images. In numerical simulations, different models of dielectric permittivity distribution have been reconstructed. On the basis of numerical simulations, a 24-electrode sensor was designed and made. In experimental tests, different distribution of medium inside the spherical tank was investigated. The results show that the method can directly measure the mass of fuel in the tank, as well as it allows for a visualization of fuel distribution, independent of the tank position in space, and the liquid-propellant system will be used.

Abstract

The most attractive property of Li0.5La0.5TiO3 (LLTO) electrolytes is their high ionic conductivity. Studies have shown that LLTO is capable of existing in a state with an ionic conductivity of 10-3 S/cm, which is comparable to liquid electrolytes. In addition to the high ionic conductivity of the material, LLTO is electrochemically stable and able to withstand hundreds of cycles. So, the studies of the solid electrolyte material are very important for the development of lithium-ion batteries. In the present paper, Li0.5La0.5Ti1-xZrxO3 (x = 0.05 and 0.1) have been prepared by a solid-state reaction method at 1300 °C for 6 hours to improve electrolyte materials for lithium-ion batteries. The phase identified by X-ray diffractometry and crystal structure corresponds to pm3m (2 2 1) space group (Z = 1). The frequency and temperature dependence of impedance, dielectric permittivity, dielectric loss and electric modulus of the Li0.5La0.5Ti1-xZrxO3 (x = 0.05 and 0.1) have been investigated. The dielectric and impedance properties have been studied over a range of frequency (42 Hz to 5 MHz) and temperatures (30 °C to 100 °C). The frequency dependent plot of modulus shows that the conductivity relaxation is of non-Debye type.

Abstract

Layered oxide LiMO2 (Ni, Co, Mn) have been proposed as cathode materials for lithium-ion batteries. Mainly LiNiO2 is accepted as an attractive cathode material because of its various advantages such as low cost, high discharge capacity, good reversibility. The LiNi0.5Mn0.5O2 powders are synthesized by a sol-gel method using citric acid as a chelating agent. The structure of the synthesized material is analyzed by using XRD, FT-IR and the microstructures of the samples are observed by using FESEM. The intensities and positions of the peaks are in a good agreement with the previous results. The morphological changes are clearly observed as a result of manganese substitution. The Fourier transform infrared (FT-IR) spectra obtained with KBr pellet data reveal the structure of the oxide lattice constituted by LiO6 and NiO6 octahedra. The conductivity studies are characterized by (EIS) in the frequency range of 42 Hz to 1 MHz at room temperature to 120 °C. The dielectric properties are analyzed in the framework of complex dielectric permittivity and complex electric modulus formalisms. It indicates that the conductivity increases with increasing temperature. The fitting data of EIS plots replicate the non-Debye relaxation process with negative temperature coefficient of resistance (NTCR) behavior.

Abstract

Single crystal of glycine hydroflruoride (GHF) was grown from aqueous solution by slow evaporation technique. The structure of the grown crystal was tested and analyzed through X-ray powder diffraction. The functional groups have been identified from the FT-IR spectra. Slabs cut normal to the b-axis from the grown crystal were subjected to incident radiation with a wavelength range of 200 nm to 800 nm to investigate the transmittance and reflectance spectra. Linear optical parameters such as extinction coefficient k, refractive index n and both the real and imaginary parts: ∊real and ∊im of the dielectric permittivity were calculated as functions of the incident photon energy. The dispersion of the refractive index was fitted in terms of Cauchy formula and Wemple-DiDomenico single oscillator model. GHF crystals exhibited indirect optical interband transition and the optical energy gap Eg was determined by using Tauc plot. The indirect band gaps at elevated temperatures were determined and their temperature dependence was estimated. Optical band gap Eg values were found to decrease with an increase in crystal temperature; however, the band tail width exhibited opposite behavior. The nonlinear optical potential was examined by the second harmonic generation (SHG) test.

References 1. Matiss, I. (2014). Multi-element sensor for non-destructive measurement of the dielectric permittivity and thickness of dielectric plates and shells. NDT and E International, 66, 99-105. 2. Armitage D. H., & Gardiner, S. J. (2001). Classical Potential Theory. Springer, pp. 89-118. 3. Matiss, I. (2011). Electrical Measurement Techniques -a New Challenge for Non- Destructive Testing. Publishing House of Riga Technical University, Riga (in Latvian), pp.44-56. 4. Venema, G.A. (2005). The Foundations of Geometry. Prentice Hall, New Jersey, pp. 111-113.

motion, direction and dividing plane of cells as well as possible ways of influencing this with external probes. It also touches upon the basic question if electric field patterns are emerging from a particular biological structure or if they are the cause of it? Our aim is to gain a better understanding of the dielectric properties of skin by creating a model of wounded skin based on experimental dielectric permittivities. In particular we strengthen our conclusions by comparing them with recent potential measurements based upon a probe which is not in contact with