Structure and Optical Characteristics of Barium–Strontium Niobate Films on Al2O3 Substrates

Optics and Spectroscopy - The structure and optical characteristics of thin films of relaxor ferroelectric Ba0.5Sr0.5Nb2O6 grown by RF sputtering in an oxygen atmosphere on an Al2O3 substrate (c...     

Formation of a disordered (Glassy) phase in deformed solid <Superscript>4</Superscript>He in the region of supersolid state

A method has been proposed to create disorder in helium crystals by their deformation immediately during the experiment. Precise measurements of the pressure have been performed at a constant volume in samples of various qualities. It has been revealed that excess pressure, which is characterized by the quadratic temperature dependence typical of the disordered glassy phase and of the dislocation contribution to the pressure, is observed in the deformed crystals along with the phonon contribution to the pressure. The effect is observed in the supersolid-state region and disappears after the careful annealing of the crystals. The ultraslow relaxation of the pressure also characteristic of the glassy phase has been observed in the process of annealing of the crystals. The obtained experimental results have been analyzed in the framework of the dislocation model and the model of two-level tunneling states.     

Lewis acid sites in boralites

This work is aimed at modeling a framework L-site of a boralite using DFT and a cyclic cluster including one B and two Si atoms. A similar cluster was used earlier as a successful model for an L-site of a zeolite, which allows for the direct comparison of the properties of the two L-sites. It is shown that the boralitic L-site is rather weak. Unlike its zeolitic counterpart, it cannot bind a molecule of ethene or carbon monoxide. Only a base as strong as ammonia can form a stable 1:1 complex with the boralitic L-site. Water is found to bind to the boralitic L-site only if not less than two of its molecules are interacting with the model cluster. As water loading increases, the geometry of the BO₃ fragment undergoes gradual changes indicative of facile hydrolysis of the boralite lattice.     

Simple molecules on a zeolite acceptor center: A quantum-chemical approach

The effectiveness and reliability of the cluster approach to modeling the interaction of several simple molecules (CO, water, ammonia, ethylene, and methanol) with zeolite acceptor centers was shown on the basis of various quantum-chemical methods and a comparison with the data of direct measurements. The Al···CO bonds were found to form in the complex of CO with three-coordinate aluminum. This allows the CO molecule to be used as a test for the acceptor properties of zeolites. A comparison of the calculation results and experimental data on the interaction of one to three RH-type molecules with a zeolite fragment led us to conclude that water, ammonia, ethylene, and methanol acquired proton-donor properties in the field of zeolite acceptor centers. These properties were similar to those of bridge OH groups in hydrogen zeolite forms. Probable schemes of catalysis on zeolites should be constructed taking into account the possible participation of acceptor centers in the conversions of molecules of the type specified.     

Optical and X-Ray Investigation of Indium Oxide Films on Sapphire Substrates

Journal of Applied Spectroscopy - The results of ellipsometric, x-ray, and spectral studies of In2O3 films deposited by dc-magnetron sputtering on Al2O3 (012) substrates are presented. The...     

Features of interpreting ellipsometric measurement results

Modifications of commonly used Malin-Vedam and minimization methods for solving the inverse problem of ellipsometry are proposed. The fields and features of their application are described. Examples of using these methods for interpreting results of ellipsometric measurements of a diamond-like a-C:N film and La_0.7Sr_0.3MnO₃ films are presented.     

Spectral and X-Ray Studies of Indium Oxide Films on Sapphire Substrates

Optics and Spectroscopy - The results of studying the optical transmission and X-ray diffraction spectra of thin In2O3 films obtained by DC magnetron sputtering on Al2O3 (012) substrates are...