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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Бондарев, Виталий Сергеевич, Карташев, Андрей Васильевич, Горев, Михаил Васильевич, Флёров, Игорь Николаевич, Погорельцев, Евгений Ильич, Молокеев, Максим Сергеевич, Раевская С. И., Суздалев Д. В., Раевский И. П.
Заглавие : Теплофизические свойства керамики ниобата натрия в широкой области температур
Место публикации : Физ. тверд. тела. - 2013. - Т. 55, Вып. 4. - С. 752-758
Примечания : Работа выполнена при финансовой поддержке гранта Президента РФ по поддержке ведущих научных школ РФ (НШ-4828.2012.2) и гранта РФФИ N 12-02-31799\_мол\_а.
Аннотация: Выполнены исследования теплоемкости Cp(T) и коэффициента теплового расширения alpha(T) керамики NaNbO3 в области температур 2-800 K. Помимо аномалий, связанных с известными фазовыми переходами при T6~265 K, T5~638 K, T4~760 K и T3~793 K, обнаружены особенносaти поведения Cp(T) и alpha(T) вблизи T5''~500 K и T5'~600 K. Установлено, что все наблюдавшиеся структурные превращения в соответствии с величинами изменения энтропии не связаны с процессами упорядочения структурных элементов. Показано, что с ростом температуры объем ячейки при фазовых переходах вблизи 265, 515, 604 и 638 K убывает. Исследованы особенности перехода в фазу R3c . Проведен анализ двух возможных сценариев реализации последовательности фазовых превращений в интервале между T5 и T6.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Вальков, Валерий Владимирович, Валькова, Татьяна Александровна, Мицкан, Виталий Александрович
Заглавие : Природа эффективных взаимодействий, индуцирующих сверхпроводящую фазу с киральным параметром порядка в кобальтитах натрия
Коллективы : "Физика бессвинцовых пьезоактивных и родственных материалов (Анализ современного состояния и перспективы развития)", международный междисциплинарный молодежный симпозиум, Южный федеральный университет
Место публикации : Физика бессвинцовых пьезоактивных и родственных материалов (Анализ современного состояния и перспективы развития) (LFPM-2015) : труды. - Ростов-на-Дону: Изд-во ЮФУ, 2015. - Т. 1. - С. 90-92. - ISBN 978-5-9275-1648-3
Примечания : Библиогр.: 6 назв.
Аннотация: На основе анализа электронной структуры NaxCoO2 при учете сильных корреляций методом операторной формы теории возмущений получен эффективный гамильтониан, описывающий антиферромагнитный тип связи между локализованными состояниями ионов кобальта на треугольной решетке и перескоки электронов в верхней хаббардовской подзоне. Существенно, что учет всех процессов второго порядка по параметру перескока в режиме большого хаббардовского отталкивания электронов с противоположными проекциями спина на одном центре приводит к трехцентровым слагаемым эффективного гамильтониана, описывающим коррелированные перескоки. Эти слагаемые существенно влияют как на характер разрушения мтрехподрешеточной структуры антиферромагнитного упорядочения при допировании, так и на условия реализации сверхпроводящей фазы с киральным параметром порядка.In the framework of the operator form of perturbation theory an effective Hamiltonian, describing the antiferromagnetic type of the coupling between localized states of the cobalt ions on the triangular lattice and electron hoppings in the upper Hubbard subband, is derived basing on the analysis of the electronic structure of NaxCoO2 and at the accounting the strong correlation. It is essential that account for all the processes of the second order in the hopping parameter at the high Hubbard repulsion of electrons located on one site and possessing the opposite spin projections leads to threecenter terms in the effective Hamiltonian, which describe the correlated hoppings. These terms affect substantially the nature of the destruction of the three-sublattice structure of antiferromagnetic ordering with doping and impact on the conditions for the implementation of the superconducting phase with a chiral order parameter
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Vasiliev A. D., Laptash N. M.
Заглавие : Polymorphism of KNaNbOF5 crystals
Место публикации : J. Struct. Chem.: Springer, 2012. - Vol. 53, Is. 5. - P.902-906. - ISSN 0022-4766, DOI 10.1134/S0022476612050101
Примечания : Cited References: 11. - The work was supported by RFBR (grant No. 09-02-00062).
Предметные рубрики: OXIDE FLUORIDE ANIONS
Ключевые слова (''Своб.индексиров.''): potassium-sodium oxopentafluoroniobate--crystal structure--o/f order--concomitant polymorphism
Аннотация: X-ray crystallography is used to analyze the concomitant polymorphism of KNaNbOF5 crystals. The second beta-modification of the compound, crystallizing in the tetragonal crystal system is found for the first time: space group P4/nmm, a = 5.9352(2) , c =8.5487(5) , V = 301.14(2) (3), Z = 2, R1 = 0.0095. Parameters of the orthorhombic noncentrosymmetric structure of the alpha-phase, previously described by Poeppelmeier et al. (J. Am. Chem. Soc., 129, 13963-13969 (2007)), are refined and a comparative analysis of both structures is performed. The structures are characterized by the complete ordering of oxygen and fluorine atoms, the Nb-O distance in the alpha-phase (1.738(1) ) being noticeably longer than that in the beta-phase (1.709(2) ). In beta-KNaNbOF5, alternating NbOF5 and NaOF5 octahedra share vertices, while in alpha-KNaNbOF5, they share both vertices and edges. The existence of the non-polar centrosymmetric beta-modification of KNaNbOF5 cancels the assumption of the substantial contribution of potassium cations to the polar structure of alpha-KNaNbOF5.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Huang J., Su B., Song E., Molokeev M. S., Xia Z.
Заглавие : Ultra-broad-band-excitable Cu(I)-based organometallic halide with near-unity emission for light-emitting diode applications
Место публикации : Chem. Mater. - 2021. - Vol. 33, Is. 12. - P.4382-4389. - ISSN 08974756 (ISSN), DOI 10.1021/acs.chemmater.1c00085
Примечания : Cited References: 43. - This research was supported by the National Natural Science Foundation of China (Grant Nos. 51961145101 and 51972118), the Fundamental Research Funds for the Central Universities (D2190980), the Guangzhou Science and Technology Project (202007020005), International Cooperation Project of National Key Research and Development Program of China (2021YFE0105700), and the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program (2017BT01X137). The reported study was also funded by RFBR according to research project no. 19-52-80003
Аннотация: Low-dimensional hybrid metal halides demonstrate broad-band emission and high photoluminescence quantum yield (PLQY) acting as excellent candidates for a new generation of luminescent materials in lighting fields. However, most luminescent metal halides can only be excited by ultraviolet radiation, and the discovery of high-efficient emitters with broad-band excitation characteristics, especially upon efficient blue light irradiation, is a challenge. Herein, a zero-dimensional (0D) Cu(I)-based organometallic halide (18-crown-6)2Na2(H2O)3Cu4I6 (CNCI) was prepared with a green emission band centered at 536 nm and a near-unity PLQY (91.8%) upon excitation of 450 nm. Importantly, the ultrabroad excitation band covering a 300-500 nm range was observed in CNCI, and the luminescence mechanism has been discussed in detail. A white light-emitting diode (WLED) was fabricated with high luminous efficiency of 156 lm/W and a high color rendering index of 89.6. This work provides guidance for designing high-performance luminescent metal halides with suitable excitation characteristics and also promotes the application prospects of such materials in WLED fields.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorev M. V., Bondarev V. S., Raevskaya S. I., Flerov I. N., Malitskaya M. A., Raevskii I. P.
Заглавие : Thermophysical study of structural phase transitions in Na0.95Li0.05NbO3 solid solution
Место публикации : Bull. Russ. Acad. Sci. Phys.: Allerton Press, 2016. - Vol. 80, Is. 9. - P.1046-1050. - ISSN 10628738 (ISSN), DOI 10.3103/S1062873816090148
Примечания : Cited References: 18. - This work was supported by Southern Federal University, project no. 213.01-2014/012-VG.
Ключевые слова (''Своб.индексиров.''): niobium oxide--sodium--specific heat--temperature distribution--thermal expansion--ceramic samples--effect of heat treatments--possible mechanisms--sodium lithium niobate--structural distortions--structural phase transition--temperature dependence--temperature range--lithium
Аннотация: Temperature dependences of specific heat Cp(T) and coefficient of thermal expansion α(T) for Na0.95Li0.05NbO3 sodium-lithium niobate ceramic samples are investigated in the temperature range of 100–800 K. The Cp(T) and α(T) anomalies at T3 = 310 ± 3 K, T2 = 630 ± 8 K, and T1 = 710 ± 10 K are observed, which correspond to the sequence of phase transitions N ↔ Q ↔ S(R) ↔ T2(S). The effect of heat treatment of the samples on the sequence of structural distortions was established. It is demonstrated that annealing of the samples at 603 K leads to splitting of the anomaly corresponding to the phase transition Q → R/S in two anomalies. After sample heating to 800 K, the only anomaly is observed in both the Cp(T) and α(T) dependence. Possible mechanisms of the observed phenomena are discussed.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bondarev V. S., Kartashev A. V., Gorev M. V., Flerov I. N., Pogoreltsev E. I., Molokeev M. S., Raevskaya S. I., Suzdalev D. V., Raevskii I. P.
Заглавие : Thermal and physical properties of sodium niobate ceramics over a wide temperature range
Место публикации : Phys. Solid State. - 2013. - Vol. 55, Is. 4. - P.821-828. - DOI 10.1134/S1063783413040045
Аннотация: The temperature dependences of the heat capacity C p (T) and thermal expansion coefficient α(T) of NaNbO3 ceramic samples have been investigated in the temperature range from 2 to 800 K. In addition to the anomalies associated with the known phase transitions at temperatures T 6 ≈ 265 K, T 5 ≈ 638 K, T 4 ≈ 760 K, and T 3 ≈ 793 K, anomalies in the behavior of C p (T) and α(T) have been observed near T 5″ ≈ 500 K and T 5′ ≈ 600 K. It has been found that all the observed structural transformations, according to the values of the entropy change, are not related to the ordering of structural elements. It has been shown that, with an increase in the temperature, the unit cell volume during the phase transitions near 265, 515, 604, and 638 K decreases. The specific features of the transition to the phase R3c have been examined. Two possible scenarios of the sequence of phase transformations in the temperature range between T 5 and T 6 have been analyzed.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Jiang C., Brik M. G., Li L., Li L., Peng J., Wu J., Molokeev M. S., Wong K. -L., Peng M.
Заглавие : The electronic and optical properties of a narrow-band red-emitting nanophosphor K2NaGaF6:Mn4+ for warm white light-emitting diodes
Место публикации : J. Mater. Chem. C. - 2018. - Vol. 6, Is. 12. - P.3016-3025. - ISSN 20507534 (ISSN), DOI 10.1039/c7tc05098d
Примечания : Cited References: 55. - We acknowledge the financial support received from the Program for Innovative Research Team in University of Ministry of Education of China (Grant No. IRT_17R38), the Key Program of Guangzhou Scientific Research Special Project (Grant No. 201607020009), the National Natural Science Foundation of China (Grant No. 51672085, 51322208, 3160440), and the Fundamental Research Funds for the Central Universities. M. G. Brik acknowledges the supports received from the Recruitment Program of High-end Foreign Experts (Grant No. GDW20145200225), the Programme for the Foreign Experts offered by Chongqing University of Posts and Telecommunications, Ministry of Education and Research of Estonia, (Project PUT430) and European Regional Development Fund (Project TK141), and the Guest Professorship at Kyoto University (Prof. S. Tanabe laboratory). The first-principles calculations were carried out using the resources provided by the Wroclaw centre for Networking and Supercomputing (http://wcss.pl; Grant No. WCSS#10117290).
Ключевые слова (''Своб.индексиров.''): energy efficiency--gallium compounds--light emission--light emitting diodes--manganese--manganese compounds--optical properties--phosphors--precipitation (chemical)--quenching--rietveld refinement--sodium compounds
Аннотация: Recently, as a key red component in the development of warm white light-emitting diodes (WLEDs), Recently, as a key red component in the development of warm white light-emitting diodes (WLEDs), Mn4+-doped fluorides with narrow red emission have sparked rapidly growing interest because they improve color rendition and enhance the visual energy efficiency. Herein, a red nanophosphor, K2NaGaF6:Mn4+, with a diameter of 150-250 nm has been synthesized using a simple co-precipitation method. Rietveld refinement reveals that it crystallizes in the space group Fm3m with the cell parameter a = 8.25320(4) Å. The exchange charge model (ECM) has been used to calculate the energy levels of Mn4+ ions in K2NaGaF6, which match well with the experimental spectra. The as-synthesized phosphor exhibits a narrow red emission at around 630 nm (spin-forbidden 2Eg → 4A2 transition of Mn4+ ions) when excited at 365 nm (4A2g → 4T1g) and 467 nm (4A2g → 4T2g), with a quantum efficiency (QE) of 61% and good resistance to thermal quenching. Based on the structure, the formation mechanism of ZPL has been discussed. In addition, the concentration-dependent decay curves of Mn4+ in K2NaGaF6 were fitted using the Inokuti-Hirayama model, suggesting that the dipole-dipole interactions determine the concentration quenching. Finally, encouraged by the good performance, a warm LED with a CRI of 89.4 and CCT of 3779 K was fabricated by employing the title nanophosphor as the red component. Our findings suggest that K2NaGaF6:Mn4+ can be a viable candidate for the red phosphor used in warm WLEDs.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Savina A. A., Atuchin V. V., Solodovnikov S. F., Solodovnikova Z. A., Krylov A. S., Maximovsky E. A., Molokeev M. S., Oreshonkov A. S., Pugachev A. M., Khaikina E. G.
Заглавие : Synthesis, structural and spectroscopic properties of acentric triple molybdate Cs2NaBi(MoO4)3
Коллективы : Russian Foundation for Basic Research [4828.2012.2, 12-02-31205]; Federal Special Program "Scientific and scientific-pedagogical staff of innovative Russia" [8379]
Место публикации : J. Solid State Chem. - 2015. - Vol. 225. - P.53–58. - ISSN 0022-4596, DOI 10.1016/j.jssc.2014.11.023. - ISSN 1095-726X
Примечания : Cited References: 66. - The authors are grateful to Dr. K.M. Khal'baeva and Dr. Irina A. Gudkova for their assistance in preparing the compound and taking X-ray single-crystal diffraction data. This study is partly supported by the Russian Foundation for Basic Research (Grants 13-03-01020 and 14-03-00298). V.V.A., A.S.K. and A.S.O. gratefully acknowledge the Ministry of Education and Science of the Russian Federation for a partial financial support.
Предметные рубрики: CRYSTAL-STRUCTURE
SINGLE-CRYSTALS
VIBRATIONAL PROPERTIES
RAMAN-SPECTROSCOPY
HYDROTHERMAL SYNTHESIS
DIELECTRIC-PROPERTIES
SELECTIVE OXIDATION;
BISMUTH MOLYBDATES
IONIC-CONDUCTIVITY
OPTICAL-PROPERTIES
Ключевые слова (''Своб.индексиров.''): triple molybdate--sodium--cesium--bismuth--crystal structure--raman spectroscopy--crystal-structure--single-crystals--vibrational properties--raman-spectroscopy--hydrothermal synthesis--dielectric-properties--selective oxidation;--bismuth molybdates--ionic-conductivity--optical-properties
Аннотация: New ternary molybdate Cs2NaBi(MoO4)3 is synthesized in the system Na2MoO4–Cs2MoO4–Bi2(MoO4)3. The structure of Cs2NaBi(MoO4)3 of a new type is determined in noncentrosymmetric space group R3c, a=10.6435(2), c=40.9524(7) Å, V=4017.71(13) Å3, Z=12 in anisotropic approximation for all atoms taking into account racemic twinning. The structure is completely ordered, Mo atoms are tetrahedrally coordinated, Bi(1) and Bi(2) atoms are in octahedra, and Na(1) and Na(2) atoms have a distorted trigonal prismatic coordination. The Cs(1) and Cs(2) atoms are in the framework cavities with coordination numbers 12 and 10, respectively. No phase transitions were found in Cs2NaBi(MoO4)3 up to the melting point at 826 K. The compound shows an SHG signal, I2w/I2w(SiO2)=5 estimated by the powder method. The vibrational properties are evaluated by Raman spectroscopy, and 26 narrow lines are measured.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorev M. V., Bondarev V. S., Raevskaya S. I., Ivliev M. P., Raevskii I. P., Flerov I. N.
Заглавие : Studies of the heat capacity and thermal expansion of the Na0.95K0.05NbO3 solid solution
Коллективы : Council on Grants from the President of the Russian Federation for Support of Leading Scientific Schools of the Russian Federation [NSh-4828.2012.2]; Russian Foundation for Basic Research [12-02-31799 mol_a]
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2014. - Vol. 56, Is. 2. - P.367-372. - ISSN 1063-7834, DOI 10.1134/S1063783414020115. - ISSN 1090-6460
Примечания : Cited References: 27. - This study was supported by the Council on Grants from the President of the Russian Federation for Support of Leading Scientific Schools of the Russian Federation (grant no. NSh-4828.2012.2) and the Russian Foundation for Basic Research (project no. 12-02-31799 mol_a).
Предметные рубрики: SODIUM NIOBATE
PHASE-TRANSITIONS
TEMPERATURE-RANGE
SINGLE-CRYSTALS
KNBO3
FERROELECTRICS
DIFFRACTION
OCTAHEDRA
Аннотация: The heat capacity and thermal expansion of ceramic samples of the Na0.95K0.05NbO3 solid solution have been investigated over a wide temperature range of 100-750 K. The observed anomalies in the heat capacity and thermal expansion at T (4) = 297 K, T (3) = 535 K, T (2) = 665 K, and T (1) a parts per thousand 710 K correspond to the sequences of phase transitions N - Q - G - S - T1. It has been shown that, as a result of the phase transitions, the unit cell volume at T (4) and T (2) decreases, and at T (3) and T (1), increases with increasing temperature. The directions of the shift of the phase transition temperatures induced by hydrostatic pressure have been determined. It has been established that all structural transformations are accompanied by relatively small variations in the entropy. Different mechanisms of the structural distortions have been discussed.
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10.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Vereshchagin S.N., Vereshchagina T.A., Solovyov L.A., Shishkina N.N., Vasilieva N.G., Anshits A.G.
Заглавие : Solid-phase transformation of Cs+- and Sr2+-bearing zeolite sorbents derived from cenospheres to mineral-like forms
Место публикации : Materials Research Society Symposium Proceedings. - 2009. - Vol. 1193: 32nd Symposium on Scientific Basis for Nuclear Waste Management (24 May 2009 through 29 May 2009, St. Petersburg, ) Conference code: 79940. - С. 87-94. - ISBN 02729172 (ISSN); 9781605111667 (ISBN)
Ключевые слова (''Своб.индексиров.''): apparent activation energy--cenospheres--crystalline minerals--crystalline phasis--crystallization temperature--higher temperatures--long-term disposal--multi phase systems--pollucites--principal components--solid-phase transformation--temperature range--thermal treatment--thermochemical transformations--transformation temperatures--xrd analysis--activation energy--atmospheric pressure--cesium--crystalline materials--crystallization--fly ash--metallic glass--radioactive waste disposal--radioactive wastes--silicate minerals--sodium--sorbents--sorption--strontium--synthesis (chemical)--waste management--atmospheric temperature
Аннотация: The paper describes the studies of the transformation of Cs+- and Sr2+-containing zeolite sorbents synthesized from fly ash cenospheres to crystalline mineral composition, suitable for the long-term disposal. Series of Cs+- and Sr2+-exchanged NaP1-containing sorbents were subjected to the thermochemical transformation in the temperature range 40-1100°C at atmospheric pressure in air and the progress of reaction was monitored by DSC and XRD analysis. It was shown that initial sodium zeolite undergoes two-step transformation at 736-785°C and 892-982°C forming nepheline as the principle product, with the conversion temperatures being dependant on the heating rate. The thermal treatment of Cs+-bearing zeolite sorbent led to formation of a complex multiphase system, the principal components of which were nepheline and pollucite. Increasing cesium content in the samples led to a monotonous shift of crystallization peak to the higher temperature range (1005-1006°C). A more complicated behavior was observed for Sr2+-containing samples, for which the crystallization temperature tends to increase (compared with NaP1) at lower Sr contents, but it starts decreasing parallel to the Sr2+ content at Sr2+ loadings 10 mg/g. The principal crystalline phases in Sr-NaP1 sample conversion were nepheline and Sr2+- containing feldspar, the quantity of which increased parallel to the increase of strontium content in zeolite. Apparent activation energies of thermochemical transformations were calculated and possible approaches to reduce transformation temperature are discussed and experimentally illustrated. © 2009 Materials Research Society.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Popov E. A., Kotlyarskii M. M., Edelman I. S.
Заглавие : Temperature and field dependence of exciton-magnon absorption of NaMnCl//3.
Место публикации : Physica Status Solidi B - Basic Research. - 1985. - Vol. 132, Is. 2. - P.465-470. - ISSN 0370-1972
Ключевые слова (''Своб.индексиров.''): band structure--light - absorption--sodium compounds - optical properties--exciton-magnon absorption--sodium manganese chloride--magnetic materials
Аннотация: The behaviour of the optical absorption bands of NaMnCl//3 is experimentally studied in the region of the **6A//1//g to **4A//1//g, **4E//g(**4G) transition of the Mn**2** plus ion in the temperature range 1. 8 to 20 K and in magnetic fields up to 20 T. Exciton and its 'hot' magnon sidebands are observed in the spectrum. The anomalous temperature dependence of the exciton-magnon bands intensity is explained by participation of magnons with wave vector K does not equal 0 in absorption. The low energy exciton-magnon band is supposed to be due to simultaneous creation of an exciton and annihilation of three thermally created magnons.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Drokina T. V., Petrakovskii G. A., Bayukov O. A., Molokeev M. S., Vorotynov A. M., Popkov S. I., Velikanov D. A.
Заглавие : Physical properties of a frustrated uasi-one-dimensional NaCuFe2(VO4)3 magnet and effect of chemical pressure induced by the substitution of sodium for lithium
Место публикации : Phys. Solid State. - 2020. - Vol. 62, Is. 2. - P.297-307. - ISSN 10637834 (ISSN), DOI 10.1134/S1063783420020122
Примечания : Cited References: 22
Аннотация: The structural, thermal, static magnetic, and resonance properties of the low-dimensional NaCuFe2(VO4)3 compound obtained by the solid-phase synthesis have been investigated. In the temperature range of 110–300 K, the electron spin resonance in the X band with a g factor of 2.008 has been detected. The magnetic properties of a sample with a high frustration level in the paramagnetic, antiferromagnetic, and disordered states have been examined. A shift of the Neel temperature to the high-temperature region in an external magnetic field has been observed. The origin of the disordered magnetism in NaCuFe2(VO4)3 are discussed. The features of substitution of sodium for lithium on the physical properties of the ACuFe2(VO4)3 (A = Na, Li) system have been established. It is shown that the chemical pressure changes the crystal lattice parameters, spacings between magnetic ions, and crystallite size, which is reflected in the physical properties of the material.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Moshkina E. M., Krylov A. S., Kokh D., Shabanova K., Molokeev M. S., Bovina A. F., Plyaskin M., Rostovtsev N., Bezmaternykh L. N.
Заглавие : Multicomponent flux growth and composition control of Cu2MnBO5:Ga ludwigites
Место публикации : CrystEngComm. - 2022. - Vol. 24, Is. 19. - P.3565-3575. - ISSN 14668033 (ISSN), DOI 10.1039/d2ce00258b
Примечания : Cited References: 26. - This study was supported by the Russian Science Foundation (Grant No. 21-72-00130). The Raman, X-ray, and EDX data were obtained using the analytical equipment of the Krasnoyarsk Regional Center of Research Equipment of the Federal Research Center “Krasnoyarsk Science Center SB RAS”
Аннотация: To reach the concentration phase boundary between antiferromagnetic Cu2GaBO5 and ferrimagnetic Cu2MnBO5 ludwigites, solid solutions Cu2Mn1−xGaxBO5 (x = 0.05, 0.1, 0.15, 0.175) were grown by the flux technique using a multi-component solvent based on Bi2Mo3O12 with the addition of Na2B4O7 which significantly influenced the crystal formation and cation composition of the studied compounds. The content of the flux system was corrected taking into account the earlier established relationship of the partition coefficients of Mn2O3 and Ga2O3. The influence of the solvent components on the ludwigite crystallization was analyzed. The maximum size of the grown crystal was 1 × 1 × 4 mm3. The structure and cation composition of the grown compounds were studied using X-ray (X-ray diffraction, EDX (energy-dispersive X-ray spectroscopy)) and vibrational (Raman) spectroscopy techniques. The phase boundary of Cu2MnBO5–Cu2GaBO5 was found to be in the concentration range of x = 0.15–0.175, corresponding to a change in the monoclinic axis direction and a leap in the lattice parameters. The symmetry evolution of metal–oxygen octahedra for four nonequivalent cation positions was analyzed, and the unique crystal structure of Cu2MnBO5 demonstrated high rigidity relative to the introduction of Ga3+ cations. The polarized Raman spectra of monoclinic ludwigites were obtained and studied for the first time. A comparison of the spectra of the studied samples in both phases and orthorhombic ludwigites was made. A number of spectral features due to the monoclinic distortions in the crystal were found. In agreement with the Raman experiment, the concentration phase boundary was close to 0.15.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Makarov N. P., Popov A. K., Timofeev V. P.
Заглавие : Effective upconversion of CO2-laser radiation in sodium vapors
Разночтения заглавия :авие SCOPUS: Effective upconversion of CO2-laser radiation in sodium vapors
Место публикации : Appl. Phys. B. - 1983. - Vol. 30, Is. 1. - P.53-55. - ISSN 0721-7269, DOI 10.1007/BF00692659
Примечания : Cited References: 17
Ключевые слова (''Своб.индексиров.''): 42.65--42.80--lasers, carbon dioxide--sodium and alloys--light
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Romanova O. B., Ryabinkina L. I., Sokolov V. V., Pichugin A. Y., Velikanov D. A., Balaev D. A., Galyas A. I., Demidenko O. F., Makovetskii G. I., Yanushkevich K. I.
Заглавие : Magnetic properties and the metal-insulator transition in GdXMn1-XS solid solutions
Коллективы :
Разночтения заглавия :авие SCOPUS: Magnetic properties and the metal-insulator transition in GdX Mn1 - X S solid solutions
Место публикации : Solid State Commun.: PERGAMON-ELSEVIER SCIENCE LTD, 2010. - Vol. 150, Is. 13-14. - P602-604. - ISSN 0038-1098, DOI 10.1016/j.ssc.2009.12.042
Примечания : Cited References: 13. - This study was supported by the Russian Foundation for Basic Research project No. 09-02-00554_a; No. 09-02-92001-NNS_a; No. 08-02-90031 Bel_a and Belarus Foundation for Basic Research project No. F04-182; ADTF "Development of scientific potential of the higher school" No. 2.1.1/401.
Ключевые слова (''Своб.индексиров.''): insulator--metals--crystal growth--phase transitions--insulator--metals--crystal growth--phase transitions--insulator--metals--antiferromagnetic semiconductors--crystal growth--cubic lattice--metal-insulator phase transition--orders of magnitude--p-type--temperature range--thermoelectric properties--thermopowers--antiferromagnetic materials--antiferromagnetism--crystal growth--crystallization--electric properties--gadolinium--grain boundaries--magnetic fields--magnetic properties--manganese--manganese compounds--metal insulator boundaries--metals--semiconductor growth--semiconductor insulator boundaries--sodium chloride--solid solutions--solidification--metal insulator transition
Аннотация: The structural, magnetic, electrical, and thermoelectric properties of GdXMn1-XS (0.01
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S., Romanova O., Gorev M. V., Velikanov D. A., Gamzatov A. G., Aliev A. M.
Заглавие : Magnetic and thermophysical properties of GdxMn1-xS solid solutions
Место публикации : J. Phys.: Condens. Matter. - 2013. - Vol. 25, Is. 2. - Ст.025802. - P. - ISSN 0953-8984, DOI 10.1088/0953-8984/25/2/025802
Ключевые слова (''Своб.индексиров.''): antiferromagnetic orders--band state--face-centered cubic lattices--magnetic phase transitions--paramagnetic phase--temperature dependence--antiferromagnetism--electron transitions--gadolinium--manganese--paramagnetism--sodium chloride--specific heat--organic polymers
Аннотация: The structural, magnetic, and thermophysical properties of cation-substituted sulfides GdXMn1-XS (0.04 ? X ? 0.25) with the NaCl-type face-centered cubic lattice have been investigated. The range of existence of long-range antiferromagnetic order has been established. The anomalies observed in the temperature dependence of the specific heat correspond to the temperatures of the magnetic phase transition. The anomaly in the specific heat caused by electron transitions between the 4f levels and d band states has been observed. It has been found that the coefficient of thermal expansion decreases with increasing concentration of substituents in the magnetically ordered region and remains nearly invariable in the paramagnetic phase. В© 2013 IOP Publishing Ltd.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Popov A. K., Myslivets S. A., Gao J. Y., Zhang H. Z., Wellegehausen B.
Заглавие : Inversionless gain in a three-level system driven by a strong field and collisions
Место публикации : Chin. Phys. - 2000. - Vol. 9, Is. 2. - P.124-130. - ISSN 1009-1963
Примечания : Cited References: 45
Предметные рубрики: ELECTROMAGNETICALLY INDUCED TRANSPARENCY
POPULATION-INVERSION
LIGHT AMPLIFICATION
QUANTUM COHERENCE
REFRACTIVE-INDEX
LASER
INTERFERENCE
TRANSITIONS
SODIUM
ATOMS
Аннотация: Inversionless gain in a degenerate three-level system driven by a strong external field and by collisions with a buffer gas is investigated. The mechanism of population distribution in upper laser level, contributed by the collision transfer, as well as by relaxation, induced by pressure of a buffer gas, is discussed in detail. Explicit formulae for analysis of optimal conditions are derived. The idea developed here for the incoherent pump could be generalized to other systems.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Golovnev N. N., Molokeev M. S., Sterkhova, Irina V., Atuchin V. V., Sidorenko, Maxim Y.
Заглавие : Hydrates [Na2(H2O)x](2-thiobarbiturate)2 (x = 3, 4, 5): crystal structure, spectroscopic and thermal properties
Коллективы : Ministry of Education and Science of the Russian Federation [3049]
Место публикации : J. Coord. Chem.: Taylor & Francis, 2016. - Vol. 69, Is. 21. - P.3219-3230. - ISSN 0095-8972, DOI 10.1080/00958972.2016.1228914. - ISSN 1029-0389(eISSN)
Примечания : Cited References:33. - This work was supported by the the Ministry of Education and Science of the Russian Federation for research engineering of the Siberian Federal University [grant number 3049].
Предметные рубрики: 2-THIOBARBITURIC ACID
COMPLEXES
1,3-DIETHYL-2-THIOBARBITURATE
TRANSFORMATION
CESIUM
Na
Li
Ключевые слова (''Своб.индексиров.''): 2-thiobarbituric acid--sodium--coordination compound--x-ray diffraction--infrared spectroscopy--thermal analysis
Аннотация: The hydrates [Na2(H2O)3(Htba)2] (1) and [Na2(H2O)4(Htba)2] (2), where H2tba is 2-thiobarbituric acid, were obtained under different thermal conditions from aqueous solutions and were structurally characterized. The molecular and supramolecular structures were compared to the known structure of [Na2(H2O)5(Htba)2] (3). In polymeric 1–3, the Htba− ions are linked to Na+ through O and S forming octahedra. The decrease of the number of coordination water molecules led to an increase of the total number of bridge ligands (μ2-H2O, Htba−) and a change of the Htba− coordination. These factors induced higher distortion of the octahedra. It was assumed that hydrates, with a different number of coordinated water molecules, are more probable when the central metal has weaker bonds with O water molecules and with other ligands. The net topologies of 1–3 were compared. Thermal decomposition and IR spectra were analyzed for 1 and 2.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorelik V. S., Pyatyshev A. Y., Krylov A. S.
Заглавие : Raman scattering in sodium nitrite crystals near the phase transition
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2016. - Vol. 58, Is. 1. - P.170-176. - ISSN 10637834 (ISSN), DOI 10.1134/S1063783416010133
Примечания : Cited References: 39. - This study was supported by the Russian Foundation for Basic Research (project nos. 12-02-00491, 13-02-00449, 13-02-90420, and 14-02-00190).
Предметные рубрики: NaNO2
SPECTROSCOPY
DEPENDENCE
SPECTRUM
SEARCH
MODES
Аннотация: Optical Raman spectra of a ferroelectric sodium nitrite crystal have been detected in a wide spectrum range at various temperatures, including the region of the ferroelectric phase transition. A manifestation of a transverse soft polar mode of the A1(z) type responsible for the ferroelectric phase transition has been discovered in the spectrum at room temperature. This mode has been found to become overdamped even far from the ferroelectric phase transition temperature. This mode also appears as a central peak under heating. It has been found that the pseudoscalar mode of the A2 type has the highest intensity in the Raman spectrum of sodium nitrite. The frequency corresponding to the maximum intensity of this mode in the Raman spectrum varies from 130 cm–1 at 123 K to 106 cm–1 at T = 513 K. A fair agreement of the experimental data for the A1(z) mode with the Lyddane–Sachs–Teller relation has been established. The polariton curves for the A1(z) polar mode and the dispersion curves for axinons has been plotted. © 2016, Pleiades Publishing, Ltd.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorelik V. S., Pyatyshev A. Y., Krylov A. S.
Заглавие : Raman scattering in a ferroelectric sodium nitrite crystal
Место публикации : Bull. Russ. Acad. Sci. Phys.: Allerton Press Incorporation, 2016. - Vol. 80, Is. 9. - P.1127-1130. - ISSN 10628738 (ISSN), DOI 10.3103/S1062873816090136
Примечания : Cited References: 25
Ключевые слова (''Своб.индексиров.''): ferroelectric devices--ferroelectricity--raman scattering--sodium--ferroelectric phase transition--overdamped--sodium nitrite--soft modes--wide spectral range--ferroelectric materials
Аннотация: Raman spectra of the ferroelectric sodium nitrite are recorded over a wide spectral range at different temperatures, including the ferroelectric phase transition interval. The room-temperature Raman spectrum reveals the overdamped А1(z) soft mode which is attributed to the ferroelectric phase transition. © 2016, Allerton Press, Inc.
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