Physicochemical and technological peculiarities of multicomponent oxide crystal growth from melt by modified Stepanov technique

The peculiarities of the modified Stepanov technique are considered. The advantages of the method for growth of oxide crystals from melts of complex compositions are shown. Crystallization conditions are given to obtain optically homogeneous Sr _x Ba_{1 − x} Nb₂O₆, BaWO₄, SrMoO₄, LiNbO₃, and Ca₃(Nb, Ga)₂Ga₃O₁₂ single crystals using dies of capillary type.     

Investigation of ferroelectric properties of strontium barium niobate crystals by second harmonic generation technique

The ferroelectric properties of Sr _x Ba_{1 − x} Nb₂O₆ (SBN-x) crystals have been investigated using noncollinear (diffuse) second harmonic generation of IR radiation converted by a disordered domain structure. The switching characteristics have been determined from the dependences of the second harmonic intensity I _2ω(t) and I _2ω(E) for the SBN-0.75 crystals. These characteristics are in good agreement with the results of measurements by traditional methods and exhibit a number of specific features (long polarization relaxation times, irreproducibility of the shape of hysteresis loops, low-frequency dependence of the quantity E _c ) associated with the relaxor nature of SBN solid solutions. The kinetics of the diffuse second harmonic generation can be described in the framework of the phenomenological approach to polarization relaxation processes in relaxor ferroelectrics. The intensity of the diffuse second harmonic in switching is determined by the parameters (duration, amplitude) of the switching field pulse.     

Kinetics of toluene hydrogenation over platinum-titania catalysts in conditions of strong metal-support interaction

Toluene hydrogenation was investigated over different platinum-titania catalysts. It was found that the form of kinetic equation of the reaction does not depend on the modifications of titania (rutile, anatase) but the catalyst activity is different. The catalyst reduction at temperature higher than 300^oC leads to strong metal-support interaction (SMSI) which is manifested in a decrease of the reaction rate.     

Preparation and reactivity of metal-containing monomers. 23. Transition metal complexes of methacryloylacetone

The Cu(II), Ni(II), Co(II), Mn(II), Fe(III), and Cr(III) complexes of methacryloylacetone have been obtained. Magnetochemical, IR, and electronic spectroscopic studies have shown these to contain the copper ion in a square planar configuration, and the other metals in the octahedral configuration. The complexes have similar steric structures both in the crystal and in solution.Institute of Chemical Physics, Russian Academy of Sciences, 142432 Chernogolovka. I. I. Mechnikov Odessa State University. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 694–699, March, 1992.     

Growth and spectral-luminescent study of SrMoO<Subscript>4</Subscript> crystals doped with Tm<Superscript>3+</Superscript> ions

SrMoO₄ crystals doped with Tm³⁺ ions have been produced from a melt using the Czochralski method; their spectral-luminescent characteristics have been studied, and laser radiation has been generated at the wavelength of 1.94 μm using laser-diode excitation. The high absorption section at the wavelength of 795 nm, the fairly high luminescence section, the long lifetime at the upper laser level ³F4 of 1.5 ms, and a wide luminescence band allow one to hope for developing efficient tunable Tm³⁺: SrMoO₄ crystal lasers with diode pumping in the range of 1.7–2.0 μm, which are capable of implementing SRS self-transformation of radiation into the middle IR band.     

Synthesis,Physicochemical Properties,and Thermo-Oxidative Stability of Diesters of 5,7-Dimethyl-3-hydroxymethyl-1-adamantanol

Synthesis of 5,7-dimethyl-3-hydroxymethyl-1-adamantanol with limited conformational mobility and of a series of esters based thereon has been performed. The physicochemical properties and thermo-oxidative stability of synthesized diesters have been studied.     

Chemoselectivity of Nitroxylation of Cage Hydrocarbons

Russian Journal of Organic Chemistry - The composition of reaction mixtures obtained by nitroxylation of 13 cage hydrocarbons with 100% nitric acid and its mixtures with acetic acid, acetic...     

Study of the temperature dependence of the electrical conductivity in strontium-barium niobate crystals with different dopants

The electrical characteristics of single crystals of strontium-barium niobate solid solutions have been studied. The temperature dependences of the electrical conductivity were obtained for different SBN compositions, nominally pure SBN:61 and SBN:75 and SBN doped with rare earth and transition-metal impurities. The influence of the chemical composition of a solid solution, thermal treatment conditions, dopant concentration, and electrode type on the specific features of the electrical conductivity of single crystals in the temperature range 20–450°C is shown.