Shows concentration changes of refractive index in binary systems of molten salts of alkali metals containing nitrite - and nitrate - anions. Refractive indices and molar refraction of the system KNO3 - NaNO2, and NaNO3 – KNO2 affirmed the concept of additivity and linearity of the isotherms changes in the composition.
Keywords: molten salt, nitrites and nitrates of alkali metals, refractive index, refraction
The electrical properties of composites based on La0.7Sr0.3MnO3 (LSMO) synthesized at the percolation threshold have been studied: LSMO / Li4P2O7, LSMO / Sb2O3, LSMO / GeO2. The activation energies of these compounds have been determined. New ceramic materials with silver interlayers between LSMO manganite crystallites have been synthesized. The current-voltage characteristics for the LSMO / GeO2 series are given. The nonlinearity of the characteristics is most pronounced for compositions near the percolation threshold, 85% LSMO / 15GeO2.
Keywords: lanthanum strontium manganite, composite material, ceramics, one-step synthesis, magnetoresistance, percolation threshold, dielectric constant, barrier layer, tunneling, spin polarization
Concentration changes in the frequencies of Raman spectra in binary salt molten alkali metal systems with a common cation Li / ClO4, NO3 are shown. An antibiotic change in the frequencies of stretching vibrations is noted.
Keywords: Concentration changes in the frequencies of Raman spectra in binary salt molten alkali metal systems with a common cation Li / ClO4, NO3 are shown. An antibiotic change in the frequencies of stretching vibrations is noted
A new class of materials is proposed that change their dielectric permittivity as a function of the magnetic field strength. Such materials are two-phase composites of composition La0.7Sr0.3MnO3 / I, where I is the isolating phase, Li4P2O7 or GeO2. The ratio of components is close to the percolation threshold: from 10% to 20% by weight. Dielectric properties have been studied in the frequency range of the measuring field from 1 kHz to 1 MHz in magnetic fields from 0 to 15 kOe. Samples have an inductive impedance, their permittivity is negative. In a magnetic field, the permittivity increases in absolute value and at room temperature the values of the magnetodielectric coefficient reach 28%.
Keywords: lanthanum strontium manganite, composite material, ceramics, one-step synthesis, magnetoresistance, percolation threshold, dielectric constant, barrier layer, tunneling, spin polarization
Based on our own, as well as literary experimental data, the analysis of the Influence of a barrier material used to create heterogeneous composites based on La0.7Sr0.3MnO3 on their magnetoresistive properties is carried out. Such composites differ in existence of an isotropic negative magnitorezistivnost (MR) connected from backs - dependent tunneling of carriers in magnetic field. The largest value MR up to 15% in the field of 15 kOe are shown when using glass-like GeO2 oxide at a percolation ratio of components.
Keywords: lanthanum strontium manganite, composite material, ceramics, one-step synthesis, magnetoresistance, percolation threshold, dielectric constant, barrier layer, tunneling, spin polarization
Showing concentration change of Raman spectra of frequencies in binary salt systems molten alkali metals with a common cation containing nitrate and perchlorate - anions. There persistence frequency when changing the composition of the molten salt systems.
Keywords: melts nitrates, alkali metal perchlorates, Raman spectra, binary salt systems
Many complex oxides of transition metals show effect of enormous dielectric permeability. New complex layered oxides LnSr2CuTiO6,5 (Ln = La, Nd, Pr) are synthesized. Their structure by means of x-ray diffraction on the Shimadzu XRD-7000 S is investigated. Processing of XRD was carried out in the program FULLPROF-2013. The main X-ray reflexes are indicated in space group I4/mmm (№ 139). The data of the crystal-chemical analysis which are carried out taking into account a charge state and coordination environment of cations show that distortion of coordination polyhedrons is significantly reduced in series Ln = La→Nd. The unit cell parameters naturally decrease according to reduction of ionic radiuses of La→Nd. Dielectric properties of materials investigated using the universal analyzer of a frequency response Solartron 1260A in the range of frequencies 1mHz - 16МHz with a signal amplitude 500-900 mV. Increasing the dielectric constant is possible due to the charge ordering caused by uneven distribution of charge. Frequency dependences of an imaginary and real part of dielectric constant are given.
Keywords: dielectric constant , complex oxide, transition metal, perovskite, x-ray diffraction, microstructure, crystal-chemical analysis, impedance- spectroscopy, charge ordering, coordination polyhedron
The problem of the stability of E.Reyssner plate on the three-dimensional elastic layer with predetermined constant elasticity. The end surfaces are smooth, communications holding layer. It is believed that the plate is in a flat stress-strain state of the effects on its cylindrical surface of the self-balanced load, with some numerical parameter characterizing the magnitude of the load at loss of stability of the plate. From the conditions of restraint ties, a system of equations for determining the numerical parameter. We give a method for calculating the lowest value of the parameter at which the fixed loss of stability of the plate. As special cases, the results of the classical theory and model of Winkler foundation.
Keywords: the self-balance loading, strained state, stress functions, stability loss
Construction of three-dimensional structures faces the need to cover the hard concrete layer with lightweight insulation and waterproof carpet. This combination of materials with different mechanical and physical properties requires the creation of methods for determining the stress-strain state of elastic composite layer lying on absolutely solid. According to these criteria the general solution of elasticity theory problem for each layer has been calculated. The system of differential equations is solved. A homogeneous solution can be used to study various problems of stress state in a layer. Formation of the problem of infinitely extending beamless surface has been drawn as an example. These solutions can be used in studding various problems of stress state layer. The solutions of engineering problems require the definition of complex roots of transcendental characteristic equation. In this paper, the roots were determined by Newton`s method. The obtained roots of the characteristic equation determine the stress and displacements in each point of a composite layer.
Keywords: eigenvalues, eigenfunctions, boundary conditions, a potential solution, vortex solution, differential operators, homogeneous system, the voltage of the plate
Lanthanum strontium manganite La0,67Sr0,33MnO3 which has a high spin polarization of the carriers has been used to create composite materials with different barrier materials - GeO2, Li4P2O7, C. The magnetoresistive properties of the synthesized ceramics at room temperature have been investigated. It has been found that the magnetoresistive isotropic negative values for samples with germanium oxide at room temperature in a magnetic field of 18 kOe reach a value of 15%, with the barriers of lithium pyrophosphate - 16%. It has been determined that the samples which contain 10-85% graphite at a field of 15 kOe exhibit positive magnetoresistance reaching a value of 15% .
Keywords: lanthanum strontium manganite, composite material, ceramics, magnetoresistance, X-ray diffraction, microstructure, barrier layer, tunneling, percolation transition, spin polarization, the Seebeck effect
Ceramic materials based on solid solutions La2-xSrxMO4, where M is Ni, Fe, Co, Cu, x = 0, 2 with layered K2NiF4 structure (structure of Ruddlesden-Popper) have been synthesized and investigated. The correlation of dielectric properties with a normalized bond lengths of the metal-oxygen has been observed. The existence of nickel atoms in the 2+ oxidation state for nickelates has been shown.
Keywords: solid solutions, colossal dielectric constant, resistivity, x-ray diffraction, dielectric spectrum, XANES, low-resistivity semiconductors, the activation energy, the distortion of the coordination polyhedra, oxygen non-stoichiometry
Composites La0,67Sr0,33MnO3 (SiO2, Sb2O3) with different weight ratios have been synthesized. Their magnetoresistive and dielectric properties have been investigated. It has been established that in the frequency range from 10 to 106 Hz for SiO2 concentration of 10% the colossal magnitudes of the dielectric constant ( ~ 4 • 104) take place. The values of the negative isotropic magnetoresistance for samples with silica at room temperature is 8.6%, with abarriers of antimony oxide reaches 12%, which makes it possible to use such materials in spintronics.
Keywords: Magnetoresistance, colossal dielectric permittivity, glass composites, X-ray diffraction, spin polarization, barrier layers, tunneling, microstructure, dielectric spectrum, Maxwell-Wagner effect.
The composite cathode material of the core@shell type with the LiMn2O4@LiCoO2 formula of has been successfully synthesized using the solid-state reactions in several stages. Its structure has been studied by means of X-ray diffraction, scanning and transmission electron microscopy and vibrational infrared spectroscopy. Electrochemical investigation in two-electrode cell has been showed improvement of characteristics of the synthesized cathode material than the constituent components. The specific power of LiMn2O4@LiCoO2 is 650 mWh/g, against 450 and 500 mWh/g for LiCoO2 and LiMn2O4, respectively.
Keywords: lithium-ion batteries, cathode materials, Delafosse, X-ray structural analysis, electron microscopy, electrochemical properties