172 research outputs found
Phase chemistry in the Ca-Mn-Sb-O system at 1160-1250 °C
Phase equilibrium in the Ca-Mn-Sb-O system was studied in air at the temperature range from 1160 to 1250°C and a pseudo-quaternary phase diagram for the system CaO-MnO-Mn2O3-Sb2O5 is presented. The following compounds were discovered: new antimonate Ca 7Sb2O12 with a perovskite-like structure, solid solutions Mn2-xCaxSb2O7 (0 ≤ x ≤ 1.6) with a 3T-weberite structure, and Ca2-xMn xSb2O7 (0 ≤ x ≤ 0.23) with a 2O-weberite structure, as well as solid solutions Ca2Mn1+xSb 1-xO6 with monoclinic (0 ≤ x ≤ 0.67) and orthorhombic (0.75 ≤ x ≤ 1) perovskite structures. The existence of a number of double and ternary oxides and solid solutions on the basis of Sb 5+ and Mn2+, Mn3+, Mn4+ and with mixed manganese valence is confirmed. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
First Principles Study of the Electronic and Vibrational Properties of LiNbO2
In the layered transition metal oxide LiNbO the Nb () ion is
trigonal-prismatically coordinated with O ions, with the resulting crystal
field leading to a single band system for low energy properties. A
tight-binding representation shows that intraplanar second neighbor hopping
meV dominates the first neighbor interaction ( meV). The
first and third neighbor couplings are strongly modified by oxygen
displacements of the symmetric Raman-active vibrational mode, and
electron-phonon coupling to this motion may provide the coupling mechanism for
superconductivity in Li-deficient samples (where K). We calculate all
zone-center phonon modes, identify infrared (IR) and Raman active modes, and
report LO-TO splitting of the IR modes. The Born effective charges for the
metal ions are found to have considerable anisotropy reflecting the degree to
which the ions participate in interlayer coupling and covalent bonding. Insight
into the microscopic origin of the valence band density, composed of Nb
states with some mixing of O states, is obtained from examining
Wannier functions for these bands.Comment: 12 pages, 7 figures; Updated with reviewer comments; Updated
reference
Professionally-Oriented Foreign Language Teaching of Master’s Degree Students
The issue of professionally-oriented foreign language teaching is relevant for foreign language teachers and for future professionals whose work lies in the field of intercultural communication. Foreign language skills become one of the essential requirements for technical professionals. One can determine the efficiency of the educational process by the educational tools and materials. An urgent task is to develop the standards for foreign language teaching of master’s degree students of engineering specialties. There are typical situations that arise in professional communication in the process of creating a teaching program. Professionals’ requirements regarding speech are taken into account. The method of projects in teaching allows master’s degree students to show independence in planning, organizing, controlling their activities, studying practical problems of modern age by means of a foreign language in the real information space. Designing the teaching program based on new educational standards imposes new requirements on assessing relevant competencies in master’s degree students. Individual work as an integral element of the educational process contributes to the improvement of professional qualifications
Synthesis and crystal structure of a new hexagonal perovskite 7H-Ba7Li1.75Mn3.5O15.75 with Mn4+/Mn5+ charge distribution.
Our work describes the synthesis and crystal structure of a new hexagonal perovskite 7H-Ba7Li1.75Mn3.5O15.75with Mn4+/Mn5+charge distribution.</p
Correction: Synthesis and crystal structure of a new hexagonal perovskite 7H-Ba7Li1.75Mn3.5O15.75 with Mn4+/Mn5+ charge distribution.
The authors regret a spelling mistake in the surname of one of authors. The surname given as ‘Vasilev’ should be ‘Vasiliev’.
Furthermore a second affiliation for the author A. D. Vasiliev was inadvertently omitted. The correct spelling and affiliations of
all the authors for this paper is as shown above.
The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers
Thermobaric synthesis, structure, and properties of Dy x Cu 3V4O12
The perovskite-like compound Dy x Cu3V 4O12 (x = 0.67-0.75) is synthesized under high pressure (P = 4.0-9.0 GPa) and temperature (T = 1000 C). Its crystal structure is determined (Im-3 space group, Z = 2, a = 7.29348(7) Å) by means of powder X-ray diffraction. The basic lengths and bond angles are defined. It is found that the high-pressure phase of Dy x Cu3V 4O12 is characterized by metallic conductivity and paramagnetic properties. © 2013 Allerton Press, Inc
Synthesis and characterization of the new high pressure phases A Cu 3 v 4O 12 (A =Gd, Tb, Er)
New ACu3V4O12 (A=Gd, Tb, Er) phases have been prepared at high pressure and high-temperature conditions (P∼8-9 GPa, T∼1000°C) in a toroid-type high pressure cell. These compounds crystallize in the cubic symmetry with a perovskite-like structure. At ambient pressure, they are paramagnetic and have activation-type conductivity. The effect of high pressure (10-50 GPa) on the electrical properties of the materials was analyzed in the temperature range from 78 to 300 K. Pressure ranges of the transition from activation type to metallic conductivity have been determined. The crystal structure of ACu3V4O12 (A=Gd, Tb, Er) was found to be stable up to 50 GPa. © 2013 Copyright Taylor and Francis Group, LLC
RHENIUM CARBIDES PREPARED BY THERMOBARIC TREATMENT OF NANOSIZED PRECURSORS
PACS 61.05.cp; 61.50.Ks The products of thermobaric treatment (P = 6 GPa; T = 1800 • C) of mechanical mixtures of nanosized rhenium powder and sibunit have been studied. The formation of high-temperature phases with composition Re 2 C has been revealed
Experimental evidence of strong phonon scattering in isotopical disordered systems: The case of LiH_xD_{1-x} crystals
The observation of the local - mode vibration, the two - mode behavior of the
LO phonons at large isotope concentration, as well as large line broadening in
LIH - D mixed crystals directly evidence strong additional phonon scattering
due to the isotope - induced disorder.Comment: 9 pages, 4 figure
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