Crystal structure and thermal expansion of RbNaCaTh(Si8O20)

RbNaCaTh(Si₈O₂₀), which crystallizes in the turkestanite structural type, was synthesized by a solid-phase reaction for the first time. The crystal structure of this compound was refined by the Rietveld method (space group P4/mcc). The temperature dependence of the unit cell parameters was studied using high-temperature X-ray diffraction analysis, and the thermal expansion coefficients of this compound were determined.     

Effect of a DC external field on the photorefractive-response dynamics in crystals with double-donor centers and shallow traps

This paper presents a theoretical analysis of the dynamics of space-charge field formation in a photorefractive crystal with double-donor centers and shallow traps. The evolution of the photorefractive-grating recording processes in the absence of an external electric field, the relaxation of the grating in the presence of a reference beam, and its subsequent development under application of an external field are considered.     

Effect of Stoichiometry on the Light-Induced Absorption and Two-Beam Interaction of Light on a Reflection Grating in Bismuth Titanate Crystals

The results of experimental investigations into the dynamics of light-induced absorption for coherent incident light (the wavelength = 633 nm) and incoherent radiation of a light emitting diode ( 660 nm) in single bismuth titanate crystals with different stoichiometric structures are presented. It is demonstrated that the dynamics of two-wave interaction on the photorefractive reflection grating in (100)-cut samples illuminated with coherent light is nonmonotonic in character. Light-induced changes in the absorption coefficient and the efficiency of interaction on the reflection grating increase when the titanium oxide content in the examined samples decreases.     

Light-Induced Absorption in Bismuth Titanium Oxide Crystals Illuminated with Narrow-Band Light

Results of investigations into the dynamics of light-induced absorption in bismuth titanium oxide crystals doped with calcium (Bi₁₂TiO₂₀:Ca) illuminated with quasimonochromatic light of semiconductor light-emitting diodes at two wavelengths from the set = 870, 660, and 525 nm are presented. Based on an analysis of the experimental data, a model of charge transfer by defect centers describing the observed phenomena is suggested.     

Simulation of Steam Distillation of Multicomponent Mixtures of Higher Aliphatic Acids

A mathematical model of steam distillation of multicomponent mixtures of higher aliphatic acids is proposed, based on solving the equation of equilibrium states for closed systems with account of the non-ideal behavior of a solution.     

Dynamics of the Light-Induced Absorption in a Bi12TiO20 : Ca Crystal

The results of investigations into the dynamics of the light-induced absorption and of its dark relaxation in a Bi₁₂TiO₂₀ : Ca single crystal are presented. To illuminate the crystal and to measure the induced changes in the absorption, narrow-band radiation of an incoherent semiconductor light-emitting diode with the wavelength = 660 nm close to that of a helium-neon laser was used. The material parameters of the crystal are estimated based on a comparison of the experimental data with the results of calculations for a theoretical model that takes into consideration doubly ionized donor centers and shallow traps.     

Dynamics of photorefractive response in sillenite crystals with double-ionized donor centers and shallow traps

The dynamics of the photorefractive response in the Bi₁₂TiO₂₀ crystal with double-ionized donor centers and shallow traps is analyzed. Consideration is given to the time dependences of the recording of a photorefractive grating in the absence of an external electric field, its storage in the dark, and its development upon the application of an external field and turning on of a reading light beam.