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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fedorov A. S., Visotin M. A., Sosedkin, Oleg A., Eremkin, Egor V.
Заглавие : MD investigations of of heat flow throw interfaces in 1D systems
Место публикации : J. Sib. Fed. Univ. Math. Phys. - 2023. - Vol. 16, Is. 3. - P.385-396. - ISSN 19971397 (ISSN); Журн. СФУ. Матем. и физ. - ISSN 23136022 (eISSN)
Примечания : Cited References: 26
Аннотация: Molecular dynamic calculations (MD) of heterogeneous 1D periodical systems are presented. It is proposed the new technique of direct calculations of thermal conductivity, where there is only one thermostat in one piece of unit cell as well as another piece where artificial friction forces act on atoms. With the help of this scheme, calculations of 1D heterogeneous systems having regions with atoms of different atomic masses are presented. It is shown that the difference in atomic masses in adjacent regions of the systems leads to a significant temperature jump at interfaces between these regions. This temperature jump exists independently of the mass ratio on both sides of the interface.The reasons for these jumps are discussed. It is also shown that, by changing the alternation of regions with different masses of atoms, it is possible to reduce the total thermal conductivity of the system by several times. On the base of these results, we can hope that for three-dimensional structures also, the thermal conductivity can be significantly reduced.Представлены молекулярно-динамические расчеты (МД) гетерогенных одномерных периодических систем. Предлагается новая методика прямых расчетов теплопроводности, при которой в одном элементе элементарной ячейки находится только один термостат, а в другом элементе действуют силы искусственного трения на атомы. С помощью этой схемы представлены расчеты одномерных гетерогенных систем, имеющих области с атомами разной атомной массы. Показано, что различие атомных масс в соседних областях систем приводит к значительному скачку температуры на границах раздела между этими областями. Этот скачок температуры существует независимо от отношения масс по обе стороны от границы раздела. Обсуждаются причины этих скачков. Также показано, что, изменяя чередование областей с разной массой атомов, можно в несколько раз уменьшить общую теплопроводность системы. На основании этих результатов можно надеяться, что и для трехмерных структур теплопроводность может быть значительно снижена.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Spiridonova T. S., Solodovnikov S. F., Molokeev M. S., Solodovnikova Z. A., Savina A. A., Kadyrova Y. M., Sukhikh A. S., Kovtunets E. V., Khaikina E. G.
Заглавие : Synthesis, crystal structures, and properties of new acentric glaserite-related compounds Rb7Ag5–3xSc2+x(XO4)9 (X = Mo, W)
Место публикации : J. Solid State Chem. - 2022. - Vol. 305. - Ст.122638. - ISSN 00224596 (ISSN), DOI 10.1016/j.jssc.2021.122638
Примечания : Cited References: 71. - This research was supported by the Ministry of Science and Higher Education of the Russian Federation , projects No. 0273-2021-0008 (Baikal Institute of Nature Management, SB RAS), and No. 121031700313-8 (Nikolaev Institute of Inorganic Chemistry, SB RAS), as well as partial financial support from the Russian Foundation for Basic Research (project No. № 20-03-00533)
Аннотация: The subsolidus phase equilibria in the system Ag2MoO4–Rb2MoO4–Sc2(MoO4)3 were studied and two new triple molybdates, Rb9Ag3Sc2(MoO4)9 and Rb7Ag5Sc2(MoO4)9, were found. The structures of Rb7Ag5Sc2(MoO4)9 and isostructural Rb7Ag5Sc2(WO4)9 of the Cs7Na5Yb2(MoO4)9 type (the space group R32) were determined. The found composition of the triple tungstate crystal, Rb7Ag4.61Sc2.13(WO4)9, indicates a non-stoichiometric compound formula, Rb7Ag5–3xSc2+x(WO4)9. Both structures have one incompletely occupied Ag site, and structure Rb7Ag4.61Sc2.13(WO4)9 also contains two positions with mixed Ag and Sc. Both compounds contain ‘lanterns’ [M2(XO4)9] (M = (Sc, Ag), Sc; X = Mo, W), which are strengthened by three AgO2 dumbbells to give isolated building blocks [Ag3M2(XO4)9] forming two-story hexagonal layers resembling the structure of glaserite K3Na(SO4)2. Similar layers of [Ag3Sc2(WO4)9]9− building blocks were also found by us in the structure of Rb9–xAg3+xSc2(WO4)9, which is close to that of Rb9Ag3Sc2(MoO4)9. Similar layers of the [M2(TO4)9] units were also observed in Cs7Na5Yb2(MoO4)9 and Na13Sr2Ta2(PO4)9. The title compounds belong to the series of rhombohedral triple molybdates and tungstates with a ≈ 9–10 Å and large c-periods (more than 20 Å), which have layered or open 3D framework structures. Like many compounds of this series, Rb7Ag5Sc2(XO4)9 (Х = W, Mo) at elevated temperatures have significant ionic conductivity reaching values 6.1·10−3 S cm−1 at 703 K (X = Mo) and 1.4·10−3 S cm−1 at 733 K (X = W) with Еа = 0.7 eV and 0.6 eV, respectively.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Grossman V. G., Molokeev M. S., Bazarova J. G., Bazarov B. G.
Заглавие : High ionic conductivity of K5-xTlx(Mg0.5Hf1.5)(MoO4)6 (0 ≤ х ≤ 5) solid solutions
Место публикации : Solid State Sci. - 2022. - Vol. 134. - Ст.107027. - ISSN 12932558 (ISSN), DOI 10.1016/j.solidstatesciences.2022.107027
Примечания : Cited References: 39. - The work was supported by Basic Project of BINM SB RAS №0273-2021-0008. Structural analysis of materials in this study was partly supported by the Research Grant No. 075-15-2019-1886 from the Government of the Russian Federation . X-ray powder diffraction and thermal analysis were obtained using the equipment of the Collective Use Center BINM SB RAS
Аннотация: Novel K5-xTlx(Mg0.5Hf1.5)(MoO4)6 (0 ≤ х ≤ 5) oxides were successfully synthesized by solid state reaction. The results indicate the formation of a continuous series of solid solutions with the NASICON-like structure (sp. gr. R3¯c) in the composition range 0 x 5. The unit-cell parameters of the solid solutions increase linearly with composition, as a consequence of thallium substitution for potassium. The cation conductivity of Tl5Mg0.5Hf1.5(MoO4)6 has been shown to exceed the conductivity of the parent potassium magnesium hafnium molybdate. The highest total conductivity of 2.49 × 10−3 S/cm was found at 831 K for Tl5Mg0.5Hf1.5(MoO4)6.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Grossman, Victoria G., Molokeev M. S., Bazarova, Jibzema G., Bazarov, Bair G., Sorokin, Nikolay, I
Заглавие : Structural, thermal and electrical studies of thallium-scandium-hafnium(zirconium) molybdates
Коллективы : Basic Project of BINM SB RAS [0273-2021-0008]; Government of the Russian Federation [075-15-2019-1886]
Место публикации : J. Solid State Chem. - 2022. - Vol. 307. - Ст.122832. - ISSN 0022-4596, DOI 10.1016/j.jssc.2021.122832. - ISSN 1095-726X(eISSN)
Примечания : Cited References: 56. - The work was supported by Basic Project of BINM SB RAS N degrees 0273-2021-0008. Research was conducted using equipment of the CCU BINM SB RAS. Structural analysis of materials in this study was partly sup-ported by the Research Grant No. 075-15-2019-1886 from the Government of the Russian Federation
Предметные рубрики: POSITIVE ELECTRODE MATERIAL
CRYSTAL-STRUCTURE
IONIC-CONDUCTIVITY
Аннотация: Thallium scandium hafnium molybdate Tl5ScHf(MoO4)6 and thallium scandium zirconium molybdate Tl5ScZr(MoO4)6 crystallize in trigonal symmetry with the space group . The compounds are synthesized by sintering the finely powdered simple molybdates mixture in a muffle furnace at 723–823 K for 100 h. The crystal structures of Tl5ScHf(MoO4)6 and Tl5ScZr(MoO4)6 are obtained by Rietveld method. The following unit cell parameters are calculated for Tl5ScHf(MoO4)6: a = 10.62338 (5), c = 38.0579 (2) Å, V = 3719.64 (4) Å3, Z = 6 and for Tl5ScZr(MoO4)6: a = 10.63216 (7), c = 38.0716 (3) Å, V = 3727.14 (5) Å3, Z = 6. The conductivity of the Tl5ScHf(MoO4)6 and Tl5ScZr(MoO4)6 are measured between 293 and 860 K. The ionic conductivity of Tl5ScHf(MoO4)6 and Tl5ScZr(MoO4)6 molybdates are 8 × 10−4 S/cm and 8 × 10−3 S/cm (at 773 K); the activation energy of ionic transfer are 0.8 eV and 0.3 eV respectively.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Чжан А. В., Дрокин, Николай Александрович, Ничкова Н. М., Мороз Ж. М.
Заглавие : Особенности спектральных характеристик электрического импеданса увлажненных зерен пшеницы
Место публикации : Усп. совр. естествознания. - 2022. - № 5. - С. 34-38. - ISSN 1681-7494, DOI 10.17513/use.37821; Adv. curr. nat. sci.
Примечания : Библиогр.: 9
Аннотация: Целью работы является определение особенностей спектральных характеристик электрического импеданса зерен пшеницы. Исследованы электрофизические свойства цельных спрессованных, а также размолотых образцов зёрен пшеницы с различной влажностью в диапазоне частот от 1 Гц до 100 МГц. Исходная партия зерен предварительно высушивалась в нагревательном шкафу при температуре 60 °С и затем насыщалась влагой в паровой бане при той же температуре. Влажность оценивалась по разнице веса между исходным и подвергнутым воздействию образцами (сушке или увлажнению). Исследовались образцы двух типов, отличающихся способом подготовки и структурой. Образцы первого типа состояли из цельных зерен, которые помещались в пресс-форму и подвергались всестороннему сжатию небольшим давлением, что исключало наличие воздушных промежутков между зернами. В образцах второго типа зерна предварительно размалывались в ступе и затем в виде порошка помещались в измерительную ячейку. Измерительная ячейка с образцом при комнатной температуре подключалась к анализаторам спектров Elins 1500J и Agilent E5061B, которые позволяют получать частотные зависимости импеданса и фазы. Согласно полученным данным, область низких частот (до 10 кГц) характеризуется преобладающим влиянием активной составляющей полного сопротивления, в то время как выше этой частоты преобладает реактивная часть. Выявлены процессы накопления электрических зарядов у поверхности металлических электродов, которые экранируют внешнее электрическое поле и приводят к аномальному увеличению диэлектрической проницаемости и тангенса угла потерь в области низких частот. Полученные спектры сопоставлялись со спектрами наиболее подходящих эквивалентных электрических схем, радиотехнические компоненты которых помогают понять основные механизмы прохождения переменного электрического тока через неоднородную структуру зерна.The aim of this work is to determine the features of the spectral characteristics of the electrical impedance of wheat grains. The electrophysical properties of whole pressed and ground samples of wheat grains with different moisture content in the frequency range from 1 Hz to 100 MHz have been studied. The initial batch of grains was preliminarily dried in a heating cabinet at a temperature of 60°C and then saturated with moisture in a steam bath at the same temperature. Moisture was estimated from the difference in weight between the original and exposed samples (drying or wetting). Samples of two types were studied, differing in the method of preparation and structure. Samples of the first type consisted of whole grains, which were placed in a mold and subjected to all-round compression by a small pressure, which excluded the presence of air gaps between the grains. In samples of the second type, the grains were preliminarily ground in a mortar and then placed in the form of a powder into a measuring cell. The measuring cell with the sample at room temperature was connected to the Elins 1500J and Agilent E5061B spectrum analyzers, which make it possible to obtain the frequency dependences of the impedance and phase. According to the data obtained, the low-frequency region (up to 10 kHz) is characterized by the predominant influence of the active component of the impedance, while above this frequency, the reactive part predominates. The processes of accumulation of electric charges near the surface of metal electrodes, which shield the external electric field and lead to an anomalous increase in the permittivity and loss tangent in the low-frequency region are revealed. The obtained spectra were compared with the spectra of the most suitable equivalent electrical circuits, the radio engineering components of which help to understand the main mechanisms of the passage of an alternating electric current through a heterogeneous grain structure.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Чжан А. В., Дрокин, Николай Александрович, Ничкова Н. М., Мороз Ж. М.
Заглавие : Метод импедансной спектроскопии для тестирования увлажненных зерен пшеницы
Место публикации : Вестн. НГАУ. - 2022. - № 2. - С. 59-68. - ISSN 2072-6724, DOI 10.31677/2072-6724-2022-63-2-59-68; Bull. NSAU
Примечания : Библиогр.: 16
Аннотация: Представлены результаты исследования электрических и диэлектрических характеристик увлажнённых зёрен пшеницы методом измерений их комплексного электрического сопротивления (импеданса Z) в широком диапазоне частот (от 1 Гц до 100 МГц). Результаты измерений электрического импеданса зерна с поверхностным или объёмным содержанием влаги в разных условиях эксперимента могут дать полезную информацию о свойствах биологических тканей зерновых культур и использоваться для разработки нового типа импедансных датчиков для тестирования качества зерна и его влажности. В качестве объекта исследований использовались хорошо высушенные зёрна пшеницы и зёрна, насыщенные влагой и солевым раствором. Серьёзной проблемой при измерениях импеданса зёрен является выбор подходящего материала электродов, накладываемых на торцевые поверхности образцов. Электроды должны обеспечивать надёжный контакт с зерном и обладать минимальным переходным сопротивлением. Для исключения поперечной деформации торцевые поверхности прессованных образцов укрепляли защитным диэлектрическим кольцом. Такие контакты обеспечивали переходное сопротивление в пределах 1–2 Ом. В области низких частот выявлены процессы накопления электрических зарядов вблизи поверхности металлических электродов и на внутренних структурах зерна, приводящие к увеличению диэлектрической проницаемости и тангенса угла потерь. В области более высоких частот поведение активной и реактивной компонент импеданса определяется процессами диэлектрической релаксации. Полученные спектры импеданса сопоставлялись со спектрами наиболее подходящих эквивалентных электрических схем, радиотехнические компоненты которых позволяют понять основные механизмы прохождения переменного электрического тока через сложную неоднородную структуру зерна. Установлено, что увлажнение зерна подсоленной водой усиливает процесс накопления электрических зарядов и влияет на дисперсию действительной и мнимой компонент импеданса.The authors presented the results of a study of the electrical and dielectric characteristics of wetted wheat grains by measuring their complex electrical resistance (impedance Z) in a wide frequency range (from 1 Hz to 100 MHz). The results of electrical impedance measurements of grains with surface or volumetric moisture content under different experimental conditions can provide useful information on the properties of the biological tissues of grain crops. These results can also be used to develop a new type of impedance sensor for testing grain quality and moisture content. The authors used well-dried wheat grains and grains saturated with moisture and saline as objects of research. A major problem in grain impedance measurements is the selection of a suitable electrode material to be placed on the end surfaces of the samples. The electrodes must ensure reliable contact with the grain and have a minimum transient resistance. The end surfaces of the pressed samples were reinforced with a protective dielectric ring to prevent transverse deformation. These contacts provided a transition resistance between 1-2 ohms. The authors have identified processes of accumulation of electric charges near the surface of metal electrodes at low frequencies and on internal grain structures, leading to an increase in the dielectric permittivity and dissipation factor. The behavior of the active and reactive components of the impedance at higher frequencies is determined by dielectric relaxation processes. The obtained impedance spectra were compared with the spectra of the most suitable equivalent electrical circuits. The radio components of the circuits provide information about the basic mechanisms of alternating electric current flow through the complex inhomogeneous structure of the grain. The authors found that moistening the grain with saline water enhances the process of accumulation of electric charges and affects the dispersion of the real and imaginary components of the impedance.
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Вид документа : Статья из журнала
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Автор(ы) : Kazak N. V., Arauzo A., Bartolome J., Molokeev M. S., Dudnikov V. A., Solovyov L., Borus A., Ovchinnikov S. G.
Заглавие : Anisotropic thermal expansion and electronic transitions in the Co3BO5 ludwigite
Место публикации : Dalton Trans.: Royal Society of Chemistry, 2022. - Vol. 51, Is. 16. - С. 6345-6357. - ISSN 14779226 (ISSN), DOI 10.1039/d2dt00270a
Примечания : Cited References: 57. - We are grateful to the Russian Foundation for Basic Research (project no. 20-02-00559 and 21-52-12033) for supporting this paper. This work was performed within the framework of the budget project no. 0287-2021-0013 for the Institute of Chemistry and Chemical Technology SB RAS. We acknowledge the financial support from the Spanish Ministry of Economy, Industry and Competitiviness (MINECO), (Grant No. MAT2017-83468-R) and from the regional Government of Aragón (E12-20R RASMIA project)
Аннотация: The investigations of the crystal structure, magnetic and electronic properties of Co3BO5 at high temperatures were carried out using powder X-ray diffraction, magnetic susceptibility, electrical resistivity, and thermopower measurements. The orthorhombic symmetry (Sp.gr. Pbam) was observed at 300 K and no evidence of structural phase transitions was found up to 1000 K. The compound shows a strong anisotropy of the thermal expansion. A large negative thermal expansion along the a-axis is observed over a wide temperature range (T = 300–600 K) with αa = −35 M K−1 at T = 500 K with simultaneous expansion along the b- and c-axes with αb = 70 M K−1 and αc = 110 M K−1, respectively. The mechanisms of thermal expansion are explored by structural analysis. The activation energy of the conductivity decreases significantly above 700 K. Electronic transport was found to be a dominant conduction mechanism in the entire temperature range. The correlations between the thermal expansion, electrical resistivity, and effective magnetic moment were revealed and attributed to the evolution of the spin state of Co3+ ions towards the spin crossover and gradual charge-ordering transition.
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Вид документа : Статья из журнала
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Автор(ы) : Aplesnin S. S., Udod L. V., Sitnikov M. N., Romanova O. B.
Заглавие : Dielectric and transport properties, electric polarization at the sequential structural phase transitions in iron-substituted bismuth pyrostannate
Место публикации : Ceram. Int. - 2021. - Vol. 47, Is. 2. - P.1704-1711. - ISSN 02728842 (ISSN), DOI 10.1016/j.ceramint.2020.08.287
Примечания : Cited References: 33. - The reported study was funded by Russian Foundation for Basic Research project № 20-52-00005 Bel_a
Аннотация: The electrical characteristics including the electrical resistance, impedance, I–V characteristics, capacitance, dissipation factor, and thermoelectric power of the Bi2Sn2-хFeхO7 (х = 0.1, 0.2) stannates have been investigated in the temperature range of 100–600 K at frequencies of 102–106 Hz. The paramagnetic contribution of electrons to the dynamic magnetic susceptibility has been established. The conductivity mechanism of the compounds has been found from the I–V characteristics and the change in the carrier sign has been determined from the thermoelectric power. The hysteresis of the I–V curves, charge transfer currents and polarization current have been observed in the Bi2Sn1·8Fe0·2O7 compound. A nonlinear field dependence of the polarization in the orthorhombic phase has been found. The correlation between the obtained characteristics and the phase structure transitions has been established. Two relaxation channels and activation energy have been found using the Debye model. The hysteretic I–V characteristics have been explained using a model of the electronic structure and the dipole and migration polarization.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Grossman V. G., Molokeev M. S., Bazarov B. G., Bazarova J. G.
Заглавие : Potassium and thallium conductors with a trigonal structure in the M2MoO4–Cr2(MoO4)3–Hf(MoO4)2 (M = K, Tl) systems: Synthesis, structure, and ionic conductivity
Место публикации : J. Alloys Compd. - 2021. - Vol. 873. - Ст.159828. - ISSN 09258388 (ISSN), DOI 10.1016/j.jallcom.2021.159828
Примечания : Cited References: 62. - The work was supported by Basic Project of BINM SB RAS № 0273-2021-0008 . Research was conducted using equipment of the CCU BINM SB RAS (Ulan-Ude, Russia). Structural analysis of materials in this study was partly supported by the Research Grant No. 075-15-2019-1886 from the Government of the Russian Federation
Аннотация: The triple molybdates M5CrHf(MoO4)6 (M = K, Tl) and TlCrHf0.5(MoO4)3 were found upon studying the corresponding ternary molybdate systems M2MoO4–Cr2(MoO4)3–Hf(MoO4)2 (M = K, Tl) in the subsolidus region using X-ray powder diffraction. The crystal structures of M5CrHf(MoO4)6 (M = K, Tl) and TlCrHf0.5(MoO4)3 are refined by Rietveld method. M5CrHf(MoO4)6 (M = K, Tl) crystallizes in space group Rc with unit cell parameters: a = b = 10.45548 (5), c = 37.24614 (3) Å, V = 3526.14 (4) Å3, Z = 6 for K5CrHf(MoO4)6 and a = b = 10.53406 (12), c = 37.6837 (5) Å, V = 3621.39 (9) Å3, Z = 6 for Tl5CrHf(MoO4)6. TlCrHf0.5(MoO4)3 crystallizes in space group R with unit cell parameters: a = b = 12.9710 (2), c = 11.7825 (2) Å, V = 1716.78 (6) Å3, Z = 6. The thermal stability and electrical conductivity of the new compounds were investigated. Electrical conductivity measurements gave high values for the triple molybdates M5CrHf(MoO4)6 (M = K, Tl) (σ = 5.22 × 10−4 S / cm for K5CrHf(MoO4)6, σ = 1.1 × 10−2 S / cm for Tl5CrHf(MoO4)6 at 773 K) and relatively low values for the triple molybdate TlCrHf0.5(MoO4)3 (σ = 4.42 × 10−6 S / cm at 773 K).
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Orlov Yu. S., Vereshchagin S. N., Novikov, S., V, Burkov A. T., Borus A. A., Sitnikov, M., V, Solovyov L. A., Volochaev M. N., Dudnikov V. A.
Заглавие : Effect of mechanical activation on the thermoelectric properties of Sr1-xSmxTiO3 ceramics
Коллективы : Russian Science FoundationRussian Science Foundation (RSF) [19-72-00097]
Место публикации : Ceram. Int. - 2021. - Vol. 47, Is. 20. - P.28992-28999. - ISSN 0272-8842, DOI 10.1016/j.ceramint.2021.07.060. - ISSN 1873-3956(eISSN)
Примечания : Cited References: 31. - This study was supported by the Russian Science Foundation, project no. 19-72-00097
Предметные рубрики: SRTIO3
LA
MICROSTRUCTURE
CONDUCTIVITY
PERFORMANCE
FIGURE
MERIT
Аннотация: The Sr1-xSmxTiO3 (х = 0.025, 0.05, 0.075, 0.1, 0.2) strontium titanate solid solutions were prepared from oxides and carbonates using a conventional ceramic technology based on the mechanochemical activation. The electrical conductivity and Seebeck coefficient of the synthesized compounds were measured in the temperature range from 300 to 800 K. We found that the properties of the samples significantly depend on the preliminary mechanochemical activation. The thermoelectric power factor attains maximum value in the hydrogen reduced samples with concentration of х = 0.05 and 0.075 obtained from nanoparticles: 5.5 μW/(cm · K2) for Sr0.95Sm0.05TiO3 (580 K) and 4.10 μW/(cm · K2) for Sr0.925Sm0.075TiO3 (650 K). An increase in the annealing temperature of mechanically activated samples leads to an even greater increase in electrical conductivity and power factor: 9.2 μW/(cm · K2) for Sr0.925Sm0.075TiO3 (650 K).
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Romanova O. B., Aplesnin S. S., Udod L. V.
Заглавие : Effect of electron and hole doping on the transport characteristics of chalcogenide systems
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR); Belarusian Republican Foundation for Basic Research [20-52-00005]
Место публикации : Phys. Solid State. - 2021. - Vol. 63, Is. 5. - P.754-757. - ISSN 1063-7834, DOI 10.1134/S1063783421050152. - ISSN 1090-6460(eISSN)
Примечания : Cited References: 21. - This study was supported by the Russian Foundation for Basic Research and the Belarusian Republican Foundation for Basic Research, project no. 20-52-00005
Предметные рубрики: MAGNETIC-PROPERTIES
TRANSITION
Аннотация: The electrical properties of the Ag0.01Mn0.99S and Tm0.01Mn0.99S semiconductor compounds and the Hall effect in them have been investigated in the temperature range of 80-400 K in a magnetic field of 12 kOe. Using the I-V characteristics, the conductivity mechanism depending on the doping type and concentration has been established. Upon substitution of silver for manganese, the Mott-type conductivity has been found, while substitution of thulium causes the ohmic conductivity. The mobility and type of carriers have been determined from the Hall constant data.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Grossman, Victoria G., Bazarova J. G., Molokeev M. S., Bazarov B. G.
Заглавие : Thallium ionic conductivity of new thallium indium hafnium molybdate ceramics
Коллективы : RFBRRussian Foundation for Basic Research (RFBR) [0339-2016-0007]; [18-08-00799]; [18-03-00557]
Место публикации : Ionics. - 2020. - Vol. 26. - P.6157-6165. - ISSN 0947-7047, DOI 10.1007/s11581-020-03739-7. - ISSN 1862-0760(eISSN)
Примечания : Cited References: 60. - This study was carried out within the state assignment of FASO of Russia (Theme No 0339-2016-0007) as well was supported by RFBR Grants 18-08-00799 and 18-03-00557
Предметные рубрики: POSITIVE ELECTRODE MATERIAL
CRYSTAL-STRUCTURE
TRIPLE MOLYBDATE
Аннотация: In the process of studying the system Tl2MoO4–In2(MoO4)3–Hf(MoO4)2, a new thallium indium hafnium molybdate was found. The crystal structure of the molybdate Tl5InHf(MoO4)6 was determined in the centrosymmetric space group R3¯c (a = 10.63893 (5) Å, c = 38.1447(3) Å; V = 3739.04 (4) Å3, Z = 6). The structure is a three-dimensional framework consisting of alternating (Hf,In)O6-octahedra connected by МоО4-tetrahedra. Each octahedron has common vertices with tetrahedra. The atoms arranged in this way form channels extended along with the a and b axes, in which thallium atoms are located. The conductivity behavior of Tl5InHf(MoO4)6 ceramics was studied in the temperature range from 300 to 870 K. The conductivity of the heavy cations of thallium is activated with increasing temperature.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Romanova O. B., Aplesnin S. S., Udod L. V.
Заглавие : Electronic Structure Change at Cationic Substitition of Manganese Sulfide by Elements with Variable Valence
Место публикации : Sib. J. Sci. Technol. - 2020. - Vol. 21, Is. 3. - P.441-450. - ISSN 2587-6066, DOI 10.31772/2587-6066-2020-21-3-441-450; \b Сибирский журнал науки и технологий
Примечания : Cited References: 27. - The reported study was funded by RFBR and BRFBR, project number 20-00005 Bel_a
Аннотация: Cation-substituted solid solutions YbxMn1-xS were prepared by the melt method from polycristalline sulfide powders. The synthesized samples are antiferromagnetic semiconductors and, according to the results of X-ray structural analysis, have an FCC structure of the NaCl type. Structural, electrical, optical, and acoustic properties of the chalcogenide system YbxMn1-xS were studied in the temperature range 80 - 500 K. The effect of variable valence elements on the electronic structure of cationic substitution of manganese sulfide has been studied. The change in the electronic structure in the YbxMn1-xS system occurs due to the electron-phonon interaction. Samples with variable valence have anomalous compressibility, which is confirmed by the data on the thermal expansion coefficient and the change in the attenuation coefficient. As a result of inelastic interaction with d- electrons, the density of states at the Fermi level changes, this is reflected in the temperature dependence of the conductivity. The positions of the f-level and two electronic transitions were determined from the IR spectra. A zone of temperatures and concentrations was found, where a correlation of structural, electrical, optical and acoustic properties is observed. To explain the experimantal results, the electronic structure of the semiconductor is considered and a model is proposed that qualitatively describes the experiment.Методом расплава из поликристаллических порошков сульфидов приготовлены катион замещенные твердые растворы YbxMn1-xS. Синтезированные образцы являются антиферромагнитными полупроводниками и согласно результатам рентгеноструктурного анализа имеют ГЦК структуру типа NaCl. Проведены исследования структурных, электрических, оптических и акустических свойств халькогенидной системы YbxMn1-xS в интервале температур 80 - 500 К. Исследовано влияние на электронную структуру элементов переменной валентности при катионном замещении сульфида марганца. Изменение электронной структуры в системе YbxMn1-xS происходит за счет электрон-фононного взаимодействия. Образцы с переменной валентностью обладают аномальной сжимаемостью, что подтверждается данными коэффициента теплового расширения и изменением коэффициента затухания. В результате неупругого взаимодействия с d-электронами меняется плотность состояний на уровне Ферми, что отражается на температурной зависимости проводимости. Из ИК спектров определены положения f-уровня и два электронных перехода. Обнаружена область температур и концентраций, где наблюдается корреляция структурных, электрических, оптических и акустических свойств. Для объяснения экспериментальных результатов рассмотрена электронная структура полупроводника и предложена модель, качественно описывающая эксперимент.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Nikolaev S. V., Orlov Yu. S., Dudnikov V. A.
Заглавие : Electronic Structure and Conductivity of a Disordered A1–xBx Binary Alloy in the Cluster Approach for the Hubbard Model
Место публикации : J. Exp. Theor. Phys. - 2020. - Vol. 131, Is. 5. - P.823-837. - ISSN 10637761 (ISSN), DOI 10.1134/S1063776120100131
Примечания : Cited References: 27. - This study was supported by the Foundation “Basis” for development of theoretical physics and mathematics, Russian Foundation for Basic Research (project no. 19-03-00017), Government of Krasnoyarsk Territory and Krasnoyarsk Regional Fund of Science according to the research project “Electronic correlation effects and multiorbital physics in iron-based materials and cuprates” (no. 19-42-240007) and research project “Features of electron-phonon coupling in high-temperature superconductors with strong electronic correlations” (no. 18-42-240017)
Аннотация: We propose a method for calculating the electronic band structure of disordered systems with strong electron correlations. Various approaches to the description of electrical conductivity of disordered systems are considered. Calculations are based on determining the one-particle Green function of the system, which is averaged over different configurations of a cluster, on the Boltzmann formalism, and the Kubo linear response theory. As the basic model, we use the Hubbard model for an A –xBx binary alloy.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Grossman V., Adichtchev S. V., Atuchin V. V., Bazarov B. G., Bazarova J. G., Kuratieva N., Oreshonkov A. S., Pervukhina N. V., Surovtsev N. V.
Заглавие : Exploration of the structural and vibrational properties of the ternary molybdate Tl5BiHf(MoO4)6with isolated MoO4 units and Tl+ conductivity
Место публикации : Inorg. Chem. - 2020. - Vol. 59, Is. 17. - P.12681-12689. - ISSN 00201669 (ISSN), DOI 10.1021/acs.inorgchem.0c01762
Примечания : Cited References: 69. - This study was supported by the Russian Science Foundation (19-42-02003, in the part of conceptualization). The study was also funded by the RFBR according to research projects 18-08-00985, 18-08-00799, and 18-03-00557. This study was carried out within the state assignment of the FASO of Russia (Theme No. 0339-2016-0007)
Аннотация: The phase relations in the subsolidus region of the Tl2MoO4–Bi2(MoO4)3–Hf(MoO4)2 system were studied with the “intersecting cuts” method. The formation of the novel ternary molybdate Tl5BiHf(MoO4)6 is found in this ternary system. The compound has a phase transition at Tpt = 731 K (ΔH = −3.15 J/g) and melts at Tm = 871 K (ΔH = −41.71 J/g), as determined by a thermal analysis. Tl5BiHf(MoO4)6 single crystals were obtained by the spontaneous nucleation method. The crystal structure of Tl5BiHf(MoO4)6 was revealed by structure analysis methods. This molybdate crystallizes in the trigonal space group R3̅c with the unit cell parameters a = 10.6801(4) Å, c = 38.5518(14) Å, V = 3808.3(2) Å3, and Z = 6. The vibrational characteristics of Tl5BiHf(MoO4)6 were determined by Raman spectroscopy. The Tl5BiHf(MoO4)6 conductivity was measured at frequencies of 0.1, 1.0, and 10 kHz in the temperature range of 293–773 K; in this temperature range, the conductivity level was 10–12–10–7 S/cm.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Volochaev M. N., Granovsky A. B., Zhilova O. V., Kalinin Y. E., Ryl'kov V. V., Sumets M. P., Makagonov V. A., Pankov S. Y., Sitnikov A. V., Fadeev E., Lahderanta E., Foshin V.
Заглавие : Transport and magnetic phenomena in ZnO-С thin-film heterostructures
Место публикации : Superlattices Microstruct. - 2020. - Vol. 140. - Ст.106449. - ISSN 07496036 (ISSN), DOI 10.1016/j.spmi.2020.106449
Примечания : Cited References: 36. - The work was supported by the Ministry of Education and Science of Russia (project No. 3.1867.2017/4.6 ) and the RFBR (project No. 19-07-00471). The work was partially funded by the Academy of Finland
Аннотация: ZnO- and C-based heterostructures were fabricated by the layer-by-layer deposition technique using the ion-beam sputtering process. Structure, electrical and magnetic properties of fabricated heterostructures are discussed. The two-phase (ZnO and C) films are evolved into a multilayer structure, consisting of amorphous carbon and crystalline ZnO layers when the bilayer thickness increases. When carbon is added to ZnO, its electrical resistivity reduces. The conduction mechanism changes from the variable-range hopping in a narrow energy band to the nearest neighbors hopping in ZnO–C films with a thickness of h ˂ 150 nm. The temperature dependence of conductivity changes from the Arrhenius-like to logarithmic law, indicating that the strong charge localization turns into a weak one when the film thickness is about 150 nm. The negative magnetoresistance of up to 1% was detected at 77 K. The film ferromagnetism at the temperature of 10 K was not found.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Dudnikov V. A., Orlov Yu. S., Solovyov, Leonid A., Vereshchagin, Sergey N., Gavrilkin, Sergey Yu., Tsvetkov, Alexey Yu., Velikanov D. A., Gorev M. V., Novikov, Sergey V., Ovchinnikov S. G.
Заглавие : Effect of multiplicity fluctuation in cobalt ions on crystal structure, magnetic and electrical properties of NdCoO3 and SmCoO3
Коллективы : Russian Science FoundationRussian Science Foundation (RSF) [18-02-00022]
Место публикации : Molecules. - 2020. - Vol. 25, Is. 6. - Ст.1301. - ISSN 1420-3049(eISSN), DOI 10.3390/molecules25061301
Примечания : Cited References: 56. - This work is supported by the Russian Science Foundation grant 18-02-00022.
Предметные рубрики: SPIN-STATE TRANSITIONS
CO3+ ION
CONDUCTIVITY
TEMPERATURE
BEHAVIOR
Аннотация: The structural, magnetic, electrical, and dilatation properties of the rare-earth NdCoO3 and SmCoO3 cobaltites were investigated. Their comparative analysis was carried out and the effect of multiplicity fluctuations on physical properties of the studied cobaltites was considered. Correlations between the spin state change of cobalt ions and the temperature dependence anomalies of the lattice parameters, magnetic susceptibility, volume thermal expansion coefficient, and electrical resistance have been revealed. A comparison of the results with well-studied GdCoO3 allows one to single out both the general tendencies inherent in all rare-earth cobaltites taking into account the lanthanide contraction and peculiar properties of the samples containing Nd and Sm.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Knyazev Yu. V., Tarasov A. S., Platunov M. S., Trigub A. L., Bayukov O. A., Boronin A. I., Solovyov L. A., Rabchevskii E. V., Shishkina N. N., Anshits A. G.
Заглавие : Structural and electron transport properties of CaFe2O4 synthesized in air and in helium atmosphere
Место публикации : J. Alloys Compd. - 2020. - Vol. 820. - Ст.153073. - ISSN 0925-8388, DOI 10.1016/j.jallcom.2019.153073. - ISSN 1873-4669 (eISSN)
Примечания : Cited References: 37. - The reported study was partially supported by the Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science (grant #18-42-243011) and the UMNIK Program.
Аннотация: The samples with the CaFe2O4-type crystal structure were obtained by the solid-state reaction method at 1000 °C in the air and the helium atmosphere for the first time. We investigated the modification of the structural and electronic properties of the obtained samples. Mössbauer, XAFS-, XPS-spectroscopies, and dc-, ac-conductivity measurements were carried out. Mössbauer and XAFS-spectroscopies showed that the local environment of Fe and Ca cations does not change in the case of the inert atmosphere synthesis. Nevertheless, a sharp six-order increase in the electrical resistance observed at room temperature for the sample obtained in the in the helium atmosphere. Moreover, calculated from dc-conductivity data activation energy rises from 0.327 for the air-synthesized sample to 0.585 eV for helium-obtained one. This behavior indicates significant modification of in-band-gap energy structure, which correlated with thermally activated charge carriers. Our ac-conductivity measurements in the frequency range of 1 kHz–2 MHz for the CaFe2O4 obtained in the air showed the presence of defect levels in the energy band structure. Oxygen pressure reduction during the synthesis results in levels vanishing. Therefore, we suppose the key role of oxygen atoms in the transport properties of the material, which is indirectly confirmed by XPS data. In prospect, CaFe2O4 can be used in promising gas analyzers.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Moiseenko E. T., Altunin R. R., Zharkov S. M.
Заглавие : In situ electron diffraction and resistivity characterization of solid state reaction process in Cu/Al bilayer thin films
Место публикации : Metall. Mat. Trans. A. - 2020. - Vol. 51, Is. 3. - P.1428-1436. - ISSN 10735623 (ISSN), DOI 10.1007/s11661-019-05602-5
Примечания : Cited References: 52. - The authors wish to thank the financial support from the Russian Science Foundation (Grant #18-13-00080)
Аннотация: Solid state reaction processes in Cu/Al thin films have been studied using the methods of in situ electron diffraction and electrical resistivity measurements. The solid state reaction in the Cu/Al thin films has been found to begin already at 88 °C with the formation of the Al2Cu phase in the process of thermal heating in vacuum. The phase sequence at the solid state reaction in the films under study has been determined to be the following: Al2Cu → AlCu → Al4Cu9. A model has been suggested for describing the initial formation stage of intermetallic compounds at the solid state reaction in Cu/Al thin films. According to this model, at the initial stage, the intermetallic compounds are formed as separate crystallites at the interface in the Cu/Al thin films. The suggested model can be applied both to the formation of the first phase, Al2Cu, and to the subsequent phases: AlCu and Al4Cu9. For the Al4Cu9 phase the temperature coefficient of the electrical resistivity has been determined to be equal to αAl4Cu9= 1.1 × 10−3 K−1.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S., Sitnikov M. N., Kharkov A. M., Konovalov S. O., Vorotinov A. M.
Заглавие : Magnetoimpedance, Jahn-Teller transitions upon electron doping of manganese sulfide
Место публикации : J. Magn. Magn. Mater. - 2020. - Vol. 513. - Ст.167104. - ISSN 03048853 (ISSN), DOI 10.1016/j.jmmm.2020.167104
Примечания : Cited References: 42. - This study was supported by youth project_Reshetnev Siberian State University of Science and Technology
Аннотация: The effect of a magnetic field on the electrical and magnetic properties of manganese sulfide upon electron doping in the YbxMn1−xS (0.05 ˂ x ˂ 0.2) compound has been investigated. The change in the conductivity type from the Poole–Frenkel to Mott law have been established using the I–V characteristics and the change in the carrier type upon temperature and concentration variations has been observed. The effect of the sample prehistory on the conductivity, impedance, and magnetic susceptibility under the action of a magnetic field in a wide temperature range has been found. The trivalent state of ytterbium ions has been determined using the electron paramagnetic resonance study. The dynamic JT transitions temperature are found by IR method and by the electron paramagnetic resonance. Anomalies of carrier mobility and magneto-impedance were found in the vicinity of the Jahn-Teller transitions. The experimental data are explained by the localization of electrons with the formation of the interstitial orbital momenta and an orbital momentum into the site. The sample prehistory is related to the lifting of the orbital angular moments degeneracy and the direction of the axis of distortion of the octahedrons in a magnetic field.
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