Ion Conductivity and Vibrational Spectra of LiNO3–KNO3 + Al2O3 Composites

Russian Journal of Electrochemistry - Composite solid electrolytes are synthesized on the basis of the eutectic nitrate mixture of 0.42LiNO3–0.58KNO3 doped by aluminum oxide nanosized powder....     

Isochoric heat capacity and <Emphasis Type="Italic">T</Emphasis>-ρ dependence of cooling agents and their mixtures along the phase equilibrium line

The entropy data were used to calculate the isochoric heat capacity along the phase equilibrium line. The rules governing the thermodynamic properties of cooling agents and possible alternative mixture variants were analyzed.     

AC conductivity of BiFeO<Subscript>3</Subscript> ceramics obtained by spark plasma sintering of nanopowder

The structure and electrical properties of BiFeO₃ ceramics obtained by spark plasma sintering of a nanopowder are investigated. The nanopowder was synthesized by burning of an organic nitrate precursor. The ac conductivity was measured in a frequency range of 1 kHz–10 MHz in a temperature interval of 25–500°C. It is established that the temperature conductivity coefficients above and below ~350°C significantly differ with both alternating and direct currents. The frequency dependence of the conductivity obeys the Jonscher power law σ ~ ω ^s , where s < 1. The interpretation of this behavior is given in the framework of the model of correlated hops of charge carriers over potential barriers. It is assumed that the hopping mechanism is realized between Fe²⁺ and Fe³⁺ ions in ceramic grains. The role of oxygen vacancies in the conduction is also discussed.     

Specific features of the thermal physical properties of relaxor ceramics based on lead zirconate titanate

The heat capacity and thermal expansion of ferroelectric relaxors based on lead zirconate titanate are studied near the diffuse phase transition. It is shown that no spontaneous phase transitions from the paraelectric phase to the ferroelectric phase and from the relaxor state to the normal ferroelectric state occur in an ensemble of nanometer-sized polar regions. It is noted that the transitions can be caused only by external electric fields or storage for a fairly long time.     

Calculation of the Parameters of the Dimeric Association of Water Molecules and Determination of Their Temperature Dependence

The conditions are determined, and the parameters for the onset of the mode of dimeric molecular association in the water system are estimated. The characteristics of dimeric associates of molecules are determined. The region of anomalous thermal compression water is increased from T ≤ 4°C to T ≤ 66.4°C by introducing the temperature equivalent T₀ of the energy of proton transition from molecule to molecule into the parameter of resonant interaction of atoms of different molecules. The time of transfer of excitation energy correlates with the periods of the valence and deformation vibrations of the molecules. Therefore, a molecule that performs valence vibrations “has time” to store an excitation energy sufficient to provide a parallel orientation of the spins of the nuclei of the hydrogen atoms in the molecules. Molecules that perform deformation vibrations have zero spins because of the smallness of the frequencies of such vibrations.     

Diffusion-path approximation in nonlocal electron kinetics

For the positive column of a discharge, nonlocal distribution functions obtained by averaging over radial diffusion paths are compared with the exact solution to the kinetic elliptic equation. For a discharge in argon, as an example, the limits of applicability of the approximate solution for various macroscopic characteristics of the plasma were identified. It was previously believed that the approximation based on averaging has the limits of applicability determined by the condition that the plasma inhomogeneity size be smaller than the energy relaxation length. This condition restricts the applicability of the approximation to low pressures. In the present work, it is shown that, for determining a number of macroscopic parameters, such as the concentration, mean energy, mobility, diffusion coefficient, and thermal conductivity of electrons, the pathaveraging approximation works well over a pressure range of up to a few Torr. A number of subtle characteristics, such as the excitation rate, ionization rate, and others, largely influenced by fast electrons, cannot be calculated from the averaged distribution functions at pressures above a few tenths of a Torr.     

Refinement of the atomic structure of CdTe single crystals

A comparative refinement of the anharmonic and disordered models of the atomic structure was performed based on precision X-ray diffraction data sets collected from a CdTe single crystal at 295, 376, 491, and 583 K. Although both models provide the asymmetric contributions of Cd and Te to the structure factors, the anharmonic model seems to be more advantageous.     

Formation of a ZnO–C Composite with a Nanocrystalline Structure

Technical Physics - The formation of a nanocrystalline composite of a ZnO–C system with simultaneous mechanical activation of a mixture of zinc oxide and graphite powders in a ball mill in an...     

Structure and Dielectric Properties of Bi1 – xSmxFeO3 Nanostructured Ceramics

Physics of the Solid State - Structure and dielectric properties of polycrystalline multiferroics of Bi1&nbsp;–&nbsp;xSmxFeO3 (x = 0–0.2) system are studied. Using X-ray...     

Crystal structure of potassium titanyl phosphate doped with zirconium

This paper reports on the results of precision X-ray structural investigations of single crystals of the compounds KTi_0.96Zr_0.04OPO₄ (at 293 K) and KTi_0.97Zr_0.03OPO₄ (at 293 and 105 K). No significant splitting of the positions occupied by potassium atoms is revealed. This result is in agreement with a considerable decrease in the electrical conductivity of potassium titanyl phosphate KTiOPO₄ (KTP) crystals doped with zirconium (KTP: Zr) as compared to crystals of undoped potassium titanyl phosphate. It is established that the difference between the Ti-O bond lengths in chains formed by titanium octahedra is not a single structural parameter responsible for the nonlinear optical properties of crystals in this series.