IR-fourier spectroscopic study of homogeneous and heterophase melts and glasses in the K,Ca/NO<Subscript>3</Subscript> system

The infrared spectra of the homogeneous and heterophase melts and glasses of the K,Ca/NO₃ system were studied. The effects of finely disperse Al₂O₃ powder additions on the structural dynamic properties of K,Ca/NO₃ were revealed. The temperature dependence of the parameters of the vibration bands corresponding to the inner vibrations of NO ₃ ^? was studied. A model of structure and a mechanism of charge transfer in heterophase nitrate glasses were suggested.     

Pyroelectric properties of high-resistant KTiOPO4 crystals in the temperature range 4.2–300 K

The results of measuring the pyroelectric coefficient γ _s ^σ of nominally perfect KTiOPO₄ (KTP) crystals grown from solution in a melt with a potassium to phosphorus ratio of ～2 are presented. The γ _s ^σ (T) dependence is monotonic in the range from 4.2 to 250 K. Deviations from a linear dependence are observed beginning from 250 K, which is considered to be due to interstitial-potassium transport in the KTP crystal field. The spontaneous polarization of unclamped KTP samples is estimated from the results of the measurements. In terms of the crystal-physics approach, it is shown that the main contribution to a polar state of KTP is made by the dipole moments of two nonequivalent mesoscopic tetrahedra forming two sublattices that are polarized in opposite directions and bound by Ti(1) ions.     

Relaxation of vibrationally excited states in solid “nitrate–nitrite” binary systems

The processes of molecular relaxation in the solid NaNO₃–NaNO₂ and KNO₃–KNO₂ “nitrate–nitrite” binary systems have been investigated by Raman spectroscopy. The relaxation time of the vibration ν₁(A) of an NO^- ₃ anion in the binary system is found to be shorter than that in individual nitrate. The increase in the relaxation rate is explained by the existence of an additional mechanism of relaxation of vibrationally excited states of the nitrate ion in the system. This mechanism is related to the excitation of vibration of another anion (NO^- ₂) and generation of a lattice phonon. It has been established that this relaxation mechanism is implemented provided that the difference between the frequencies of the aforementioned vibrations correspond to the range of sufficiently high density of states in the phonon spectrum.     

Temperature-Phase Dependence of the Vibration Spectrum and Orientation Mobility of the Tetrafluoroborate Ion in n-Bu4NBF4 Organic Salt

Physics of the Solid State - The structural and dynamic properties of a tetrafluoroborate ion in n-Bu4NBF4 organic salt at different temperatures and phase states were studied by oscillation...     

Properties of metal-zinc oxide contacts

The known methods of forming surface barrier structures on zinc oxide are analyzed. The dependence of surface and contact properties of zinc oxide on thermal processing temperature in air and vacuum is studied. It is established that the contact may become rectifying or ohmic depending on the character of surface processing. It is shown that the major factor determining the properties of zinc-oxide contacts is the state of the semiconductor surface. The effect of moisture on the properties of such contact is studied.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 72–75, June, 1981.     

Absolute structure of La<Subscript>3</Subscript>Ga<Subscript>5</Subscript>SiO<Subscript>14</Subscript> langasite crystals

The absolute structure of La₃Ga₅SiO₁₄ piezoelectric crystals (a = 8.1746(6) Å, c = 5.1022(4) Å, space group P321, Z = 1) with the positive sense of rotation of the plane of polarization is refined using X-ray diffraction analysis (R = 1.37%, R _w = 1.71%, 2413 unique reflections, max sinθ/λ = 1.15 Å^?1). The contributions from the anharmonicity of thermal vibrations of lanthanum atoms are calculated with the use of the components of the third-and fourth-rank tensors. It is demonstrated that these contributions can have a significant effect.     

Effect of heat treatment on the structure and properties of a BiFeO<Subscript>3</Subscript> nanopowder

This paper presents the results of an investigation of changes in the structure, magnetic, electrical, and thermal properties of a nanostructured bismuth ferrite powder prepared by the combustion of nitrateorganic precursors before and after heat treatment at temperatures of 500, 600, 700, and 800°C. It has been shown that there is a dependence of the magnetic properties on the dispersion of the particles. The specific features of the temperature and frequency dependences of the dielectric properties over wide ranges of frequencies and temperatures, as well as near the Néel temperature, have been considered.