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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Мельникова, Светлана Владимировна, Лапташ Н. М.
Заглавие : Влияние атмосферной влажности на симметрию и фазовые переходы слоистых калиевых оксифторидов K2NbOF5·H2O
Место публикации : Физ. тверд. тела. - 2013. - Т. 55, Вып. 6. - С. 1142-1146
Примечания : Работа выполнена при финансовой поддержке гранта Президента РФ (НШ-4828.2012.2)
Аннотация: Выращены кристаллы K2NbOF5·H2O, проведены поляризационно-оптические исследования, измерены двулучепреломление и углы вращения оптической индикатрисы в интервале температур 100-400 K. Установлено, что при комнатной температуре этот слоистый кристалл в зависимости от степени влажности атмосферы может находиться в трех состояниях: A, B и C, различающихся симметрией и свойствами. Кристалл K2NbOF5·H2O в состоянии A, реализующийся при относительной влажности RH=90-100%, испытывает несобственный сегнетоэластический фазовый переход первого рода P 1=ftrightarrow C2/m, сопровождающийся сильными аномалиями оптических характеристик, двойникованием, появлением сдвиговой деформации x6 при температурах T2 downarrow ＝308 K и T2 uparrow ＝313 K. Наиболее устойчивое состояние K2NbOF5·H2O --- B (RH ＝20-90%) --- сохраняет моноклинную симметрию C2/m в области температур 100-370 K. В сухой атмосфере (RH ＝0-20%) или при T1~370 K кристалл становится безводным (K2NbOF5) с симметрией P4/nmm (состояние C). Различие кристаллов в состояниях A и B объясняется наличием или отсутствием молекул воды в межслоевых пространствах.20-90%) --- сохраняет моноклинную симметрию C2/m в области температур 100-370 K. В сухой атмосфере (RH ＝0-20%) или при T1~370 K кристалл становится безводным (K2NbOF5) с симметрией P4/nmm (состояние C). Различие кристаллов в состояниях A и B объясняется наличием или отсутствием молекул воды в межслоевых пространствах.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Головнёв, Николай Николаевич, Молокеев, Максим Сергеевич, Белаш М. Ю.
Заглавие : Кристаллическая структура 2-тиобарбитурата калия
Место публикации : Журн. структ. химии. - 2013. - Т. 54, № 3. - С. 512-516. - ISSN 0136-7463
Ключевые слова (''Своб.индексиров.''): кристаллическая структура--тиобарбитурат калия--водородные связи--π-π -взаимодействие--crystal structure--potassium thiobarbiturate--hydrogen bonds--π-π interaction
Аннотация: Определена кристаллическая и молекулярная структура тиобарбитурата калия C 4H 3KN 2O 2S (C 4H 4N 2O 2S — 2-тиобарбитуровая кислота, Н 2ТВА). Кристаллографические данные КНТВА: a = 11,2317(17), b = 3,8687(6), с = 14,557(2) Å, β = 97,448(4)°, V = 627,18(17) Å 3, пр. гр. P 2/ с, Z = 4. Каждый из ионов калия связан с четырьмя атомами кислорода и двумя атомами S, образуя искаженный октаэдр. Водородные связи N—H …O и C—H …S образуют разветвленную трехмерную сеть. Структура также стабилизирована π—π-взаимодействием гетероциклических ионов НТВА –.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zeer E. P., Kubarev Yu.G., Lundin A. G.
Заглавие : On the nature of phase transition in the potassium ferrocyanide crystal family
Коллективы : International meeting on ferroelectricity
Место публикации : Ferroelectrics. - 1978. - Vol. 20, Spesial issue. - P.223-224. - DOI 10.1080/00150197808237219
Примечания : Библиогр.: 12 назв.
Аннотация: The model and statistical description of the phase transitions in LiNH4SO4 were proposed. The nmr investigation of the high pressure phase was carried out.
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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) : Kononova O.N., Melnikov A.M., Borisova T.V., Krylov A. S.
Заглавие : Simultaneous ion exchange recovery of platinum and rhodium from chloride solutions
Место публикации : Hydrometallurgy. - 2011. - Vol. 105, Is. 3-4. - P.341-349. - JAN. - ISSN 0304-386X, DOI 10.1016/j.hydromet.2010.11.009
Примечания : Cited Reference Count: 46
Предметные рубрики: GROUP-METALS PGM
SEPARATION
CATALYST
ANION
ADSORPTION
EXTRACTION
CHEMISTRY
RESIN
Ключевые слова (''Своб.индексиров.''): platinum--rhodium--sorption--anion exchangers--chloride solutions--anion exchangers--chloride solutions--platinum--rhodium--sorption--ammonium thiocyanate--anion exchangers--basic parameters--chemical structure--chloride solutions--diffusion coefficients--distribution coefficient--exchange capacities--kinetic properties--noble metals--purolite--rhodium chloride--separation factors--sorption ability--work focus--ammonium compounds--chlorine compounds--desorption--hydrochloric acid--ion exchange--ion exchange resins--ions--platinum--platinum compounds--potassium hydroxide--precious metals--recovery--rhodium--sulfuric acid--thioureas--urea--rhodium compounds
Аннотация: This work focuses on the sorption recovery of platinum (II, IV) and rhodium (III) simultaneously present in chloride solutions, freshly prepared and stored over 3 months, on commercial anion exchangers with different physical and chemical structure. The sorption was carried out from solutions with 0.001-4.0 mol/L HCl. The initial platinum and rhodium concentrations in contacting solutions were 0.25-2.5 mmol/L Sorption and kinetic properties of the chosen anion exchangers were investigated and the basic parameters of exchange capacity, recovery, distribution coefficients, separation factors, process rate, diffusion coefficients and half-exchange times were calculated. It is shown that anion exchangers investigated possess high sorption ability to platinum and rhodium chloride complexes, which does not deteriorate in case of stored solutions. Desorption of platinum and rhodium from the resins investigated was carried out with hydrochloric acid (2 mol/L), thiourea (1 mol/L) in sulfuric acid (2 mol/L) or in potassium hydroxide (2 mol/L) as well as by ammonium thiocyanate (2 mol/L). It was shown that complete separation of platinum and rhodium can be carried out with 2 mol/L HCl on anion exchanger Purolite S 985, whereas 2 mol/L NH(4)SCN as an elution agent leads to complete separation of noble metals on anion exchangers Purolite S 985, Purolite A 500 and AM-2B. (C) 2010 Elsevier B.V. All rights reserved.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Vtyurin A. N., Isaenko L. I., Krylova S. N., Yelisseyev A., Shebanin A. P., Turchin P. P., Zamkova N. G., Zinenko V. I.
Заглавие : Raman spectra and elastic properties of KPb2Cl5 crystals
Место публикации : 11th International Conference on Phonon Scattering in Condensed Matter (PHONONS 2004) (JUL 25-30, 2004, St Petersburg, RUSSIA): WILEY-V C H VERLAG GMBH, 2004. - P3142-3145. - ISBN 3-527-40588-7, DOI 10.1002/pssc.200405401
Примечания : Cited References: 10
Предметные рубрики: LATTICE-DYNAMICS
Ключевые слова (''Своб.индексиров.''): computer simulation--crystal structure--eigenvalues and eigenfunctions--halogen compounds--nonlinear optics--phonons--potassium compounds--vectors--elastic constants--heavy cations--ionic electron envelopes--ionic interactions--raman scattering
Аннотация: Raman scattering spectra and elastic constants of KPb2Cl5 crystals have been studied. The results obtained are interpreted in terms of the ab initio lattice dynamics model taking into account multipole moments of ionic electron envelopes. The experimental results have been found to be in good agreement with numerical simulation; the narrow phonon spectra are shown to be due to a considerable contribution of heavy cations into the eigenvectors of the higher frequency lattice modes.
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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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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ivanov Y. N., Sukhovskii A. A., Aleksandrova I. P., Totz J., Michel D.
Заглавие : Nuclear spin resonance study of the ion mobility in a KHSeO4 crystal
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2004. - Vol. 46, Is. 10. - P1845-1850. - ISSN 1063-7834, DOI 10.1134/1.1809417
Примечания : Cited References: 15
Предметные рубрики: POTASSIUM HYDROGEN SULFATE
EXCHANGE NMR
SOLIDS
Аннотация: The ion mobility in a crystal of partially deuterated potassium hydroselenate (KHSe) was studied using nuclear spin resonance (NSR) of H-1, H-2, Se-77, and K-39 in a wide temperature range. The temperature dependences of the deuterium NSR spectra above 360 K exhibit changes in the line shape characteristic of chemical exchange processes. These exchange processes were studied in detail using two-dimensional H-2 NSR spectroscopy. It was ascertained that the exchange between deuterons of hydrogen bonds take place in the entire temperature range under study. However, the measured conductivity was approximately one-hundredfold lower than that estimated from the exchange frequencies. It was assumed that the low conductivity in the temperature range under study is caused by closed dimers of SeO4 groups in the KHSe structure. (C) 2004 MAIK "Nauka / Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : BAYUKOV O. A., PETRAKOVSKII G. A., SABLINA K. A., MATVEIKO E. N.
Заглавие : MOSSBAUER STUDY OF POTASSIUM FERRITES
Место публикации : Fiz. Tverd. Tela: MEZHDUNARODNAYA KNIGA, 1993. - Vol. 35, Is. 6. - P1449-1456. - ISSN 0367-3294
Примечания : Cited References: 16
Предметные рубрики: BETA-ALUMINA
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Melnikova S. V., Laptash N. M.
Заглавие : Influence of atmospheric humidity on the symmetry and phase transitions of layered potassium oxyfluorides K2NbOF5 center dot H2O
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2013. - Vol. 55, Is. 6. - P.1231-1235. - ISSN 1063-7834, DOI 10.1134/S1063783413060243
Примечания : Cited References: 8. - This study was supported by the Council on Grants from the President of the Russian Federation (grant no. NSh-4828.2012.2).
Предметные рубрики: OXOPEROXOFLUORO COMPLEXES
MO V
CRYSTAL STRUCTURE
OXOFLUORO
MONOHYDRATE
Аннотация: Crystals of K2NbOF5 center dot H2O have been grown, polarization optical investigations have been performed, and the birefringence and rotation angle of the optical indicatrix have been measured in the temperature range 100-400 K. It has been found that, depending on the degree of atmospheric humidity, the layered K2NbOF5 center dot H2O crystal at room temperature can be in three states, namely, A, B, and C, which differ in symmetry and properties of the crystal. The K2NbOF5 center dot H2O crystal in the A state exists at a relative humidity RH = 90-100% and undergoes a first-order improper ferroelastic phase transition P a dagger" C2/m, which is accompanied by strong anomalies of the optical characteristics, twinning, and shear strain x (6) at temperatures T (2) (a dagger") = 308 K and T (2) (a dagger) = 313 K. The most stable state of the K2NbOF5 sdH(2)O crystal is the B state (RH = 20-90%), which retains the monoclinic symmetry C2/m in the temperature range 100-370 K. In a dry atmosphere (RH = 0-20%) or at T (1) a parts per thousand 370 K, the crystal becomes anhydrous (K2NbOF5) with the symmetry P4/nmm (the C state). The difference between the crystals in the states A and B is explained by the presence or absence of water molecules in interlayer spaces.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mel'nikova S. V., Laptash N. M.
Заглавие : Influence of atmospheric humidity on the symmetry and phase transitions of layered potassium oxyfluorides K2NbOF5 · H2O
Место публикации : Phys. solid state: Springer, 2013. - Vol. 55, Is. 6. - P.1231-1235
Аннотация: Crystals of K2NbOF5 · H2O have been grown, polarization optical investigations have been performed, and the birefringence and rotation angle of the optical indicatrix have been measured in the temperature range 100–400 K. It has been found that, depending on the degree of atmospheric humidity, the layered K2NbOF5 · H2O crystal at room temperature can be in three states, namely, A, B, and C, which differ in symmetry and properties of the crystal. The K2NbOF5 · H2O crystal in the A state exists at a relative humidity RH = 90–100% and undergoes a first-order improper ferroelastic phase transition P 1ˉ ↔ C2/m, which is accompanied by strong anomalies of the optical characteristics, twinning, and shear strain x 6 at temperatures T 2 ↓ = 308 K and T 2 ↑= 313 K. The most stable state of the K2NbOF5 sdH2O crystal is the B state (RH = 20–90%), which retains the monoclinic symmetry C2/m in the temperature range 100–370 K. In a dry atmosphere (RH = 0–20%) or at T 1 ≈ 370 K, the crystal becomes anhydrous (K2NbOF5) with the symmetry P4/nmm (the C state). The difference between the crystals in the states A and B is explained by the presence or absence of water molecules in interlayer spaces.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Makarova I. P., Verin I. A., Aleksandrov K. S.
Заглавие : X-ray diffraction study of RbLiCrO4
Коллективы : European meeting on ferroelectricity
Место публикации : Ferroelectrics. - 1991. - Vol. 124, Is. 1. - P.91-96. - ISSN 0015-0193, DOI 10.1080/00150199108209420
Примечания : Cited References: 12
Предметные рубрики: LITHIUM POTASSIUM-SULFATE
THERMAL VIBRATIONS
CRYSTALS
PROGRAM
KLISO4
LIKSO4
Аннотация: Crystal structure of RbLiCrO4 was determined in G3 phase (sp. gr. P31c) at 293, 428, 493, 523 K and in G2 phase (sp. gr. P63) at 553, 583 K applying X-ray diffraction data. The investigated crystals exhibit ‘twinning by merohedry’. The analysis of intensities and influence of anomalous scattering on them allowed us to choose twin elements and atomic configurations of twin domains for all the investigated specimens.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Makarova I. P., Verin I. A., Aleksandrov K. S.
Заглавие : Structure and twinning of RbLiCrO4 crystals
Место публикации : Acta Crystallogr. B. - 1993. - Vol. 49. - P.19-28. - ISSN 0108-7681, DOI 10.1107/S0108768192006141
Примечания : Cited References: 14
Предметные рубрики: LITHIUM POTASSIUM-SULFATE
NEUTRON-DIFFRACTION
THERMAL VIBRATIONS
KLISO4
PROGRAM
LIKSO4
Аннотация: The crystal structures of the G3 (space group P31c) and G2 (space group P6(3)) phases of RbLiCrO4 have been determined from X-ray diffraction data (Mo Kalpha radiation) at 293, 428, 493 and 523 K (G3 phase) and 553 and 583 K (G2 phase). The RbLiCrO4 crystals exhibit twinning by merohedry with twin laws in the G3 phase: 2 parallel-to [001], m perpendicular-to [001], 1BAR; in the G2 phase: m parallel-to [001], 2 perpendicular-to [001], 1BAR. The analysis of diffraction intensities and influence of anomalous scattering on them provided the unambiguous determination of the twin laws for all the specimens investigated. The structure has been refined using the approximation of the anharmonic thermal vibrations of atoms.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Lundin A. G., Zeer E. P.
Заглавие : Radiospectroscopic investigation of potassium ferrocyanide and isomorphous compounds
Коллективы : International Meeting on ferroelectricity
Место публикации : Proceedings of the International meeting on ferroelectricity. - Prague, 1966. - P.400-409
Примечания : Cited References: 10

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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Padamata, Sai Krishna, Yasinskiy, Andrey, Shabanov A. V., Bermeshev, Timofey, Yang, You-jian, Wang, Zhao-wen, Cao, Dao, Polyakov, Peter
Заглавие : Improving corrosion resistance of Cu-Al-based anodes in KF-AlF3-Al2O3 melts
Коллективы : State Assignment for the Science of Siberian Federal University, Russia [FSRZ-2020-0013]
Место публикации : Trans. Nonferrous Met. Soc. China. - 2022. - Vol. 32, Is. 1. - P.354-363. - ISSN 1003-6326, DOI 10.1016/S1003-6326(22)65800-X. - ISSN 2210-3384(eISSN)
Примечания : Cited References: 24. - The work is performed as a part of the State Assignment for the Science of Siberian Federal University, Russia (No. FSRZ-2020-0013) . Use of Krasnoyarsk Regional Center of Research Equipment of Federal Research Center "Krasnoyarsk Science Center SB RAS" is acknowledged
Предметные рубрики: NI-FE
ALUMINUM ELECTROLYSIS
INERT ANODES
NICKEL FERRITE
BEHAVIOR
Аннотация: The anodic behaviour of pre-oxidised and non-oxidised Cu−Al-based anodes (Cu−10Al and Cu−9.8Al−2Mn) in KF−AlF3−Al2O3 melts was studied through galvanostatic and potentiodynamic polarization techniques. The alloy compositions were oxidised for a short-term (8 h) at 700 °C, followed by galvanostatic polarization for 1 h at 800 °C with an applied current density of 0.4 A/cm2. The potentiodynamic curves were recorded with a sweep rate of 0.01 V/s. XRD analysis was conducted on frozen melt samples collected on the surface of the anode, and SEM observation was performed on the anode after the experiment to study the phases of the scales formed on the alloys. All the anode materials had a steady potential between 2.30 and 2.50 V(vs Al/AlF3). The corrosion rates of the anodes were calculated from the data acquired through potentiodynamic polarization. It was seen that pre-oxidised anodes possess a low corrosion rate compared to those without pre-oxidation treatment.
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16.

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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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Gorev M. V., Kartashev A. V., Pogorel'tsev E. I., Laptash N. M.
Заглавие : Heat capacity, thermal expansion and barocaloric effect in fluoride K2TaF7
Место публикации : J. Mater. Sci. - 2019. - Vol. 54, Is. 23. - P.14287–14295. - ISSN 00222461 (ISSN), DOI 10.1007/s10853-019-03924-8
Примечания : Cited References: 20. - The reported study was funded by RFBR according to the research Project No. 18-02-00269_a.
Аннотация: The heat capacity and thermal expansion of potassium heptafluorotantalate were studied. The room temperature phase P21/c is stable at least to 4 K. The strong first-order phase transition P21/c−Pnma at T0=486.2K is accompanied by giant changes in the entropy, ΔS0=22.3J(molK)−1, and volume strain, δV0/V=−3.6%. A rather high sensitivity of K2TaF7 to pressure was found, dT0/dp=−220KGPa−1. Significant extensive and intensive barocaloric effects are found at low pressure. The possibility of improving the barocaloric properties is discussed.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Golovnev N. N., Molokeev M. S., Lesnikov M. K.
Заглавие : Structure of potassium and cesium barbiturates
Коллективы : Ministry of Education and Science [4.7666.2017/BCh]
Место публикации : Russ. J. Inorg. Chem. - 2018. - Vol. 63, Is. 10. - P.1315-1321. - ISSN 0036-0236, DOI 10.1134/S0036023618100078. - ISSN 1531-8613(eISSN)
Примечания : Cited References: 25. - This work was performed within the state task from the Ministry of Education and Science to the Siberian Federal University in 2017-2019 (4.7666.2017/BCh).
Предметные рубрики: CRYSTAL-STRUCTURE
THERMAL-PROPERTIES
1,3-DIETHYL-2-THIOBARBITURATE
Ключевые слова (''Своб.индексиров.''): potassium and cesium barbiturates--synthesis--structure--thermal decomposition
Аннотация: The structures of catena-[K(μ6-Hba−O,O,O,O′,O′,O″)] (I) and catena-[Cs(μ6-Hba–O,O,O′,O′,O″,O″)] (II), where Н2ba is barbituric acid C4H4N2O3, were characterized by powder X-ray diffraction. Crystallographic data: a = 14.1603 (4) Å, b = 3.68977 (9) Å, c = 10.9508 (3) Å, β = 82.226 (1)°, V = 566.90 (3) Å3, space group P21/n, Z = 4 for I; a = 14.652 (1) Å, b = 11.7275 (7) Å, c = 3.8098 (3) Å, β = 79.140 (6)°, V = 642.90 (8) Å3, space group C2/m, Z = 4 for II. The structural topologies of alkali metal complexes with barbituric acid and some its derivatives were compared. The thermal stability of complexes I and II in an air atmosphere was studied.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Golovnev N. N., Molokeev M. S., Belash M. Y.
Заглавие : Crystal structure of potassium 2-thiobarbiturate
Место публикации : J. Struct. Chem.: MAIK Nauka-Interperiodica / Springer, 2013. - Vol. 54, Is. 3. - P.566-570. - ISSN 0022-4766, DOI 10.1134/S0022476613030141
Примечания : Cited References: 18. - The work was supported by the grant of the President of the Russian Federation for the support of leading scientific schools of the Russian Federation (NSh-4828.2012.2) and the Federal Targeted Program "Scientific and Scientific Pedagogical Personnel of Innovative Russia, 2009-2013" (State contracts Nos. 02.740.11.0269 and 02.740.11.0629).
Предметные рубрики: ACID
Ключевые слова (''Своб.индексиров.''): crystal structure--potassium thiobarbiturate--hydrogen bonds--pi-pi interaction
Аннотация: The crystal and molecular structure of potassium thiobarbiturate C4H3KN2O2S (C4H4N2O2S-2-thiobarbituric acid, H(2)TBA) is determined. Crystallographic data for KHTBA are as follows: a = 11.2317(17) , b = 3.8687(6) , c = 14.557(2) , beta = 97.448(4)A degrees, V = 627.18(17) (3), space group P2/c, Z = 4. Each potassium ion is linked with four oxygen atoms and two S atoms forming a distorted octahedron. N-HaEuro broken vertical bar O and C-HaEuro broken vertical bar S hydrogen bonds form a branched three-dimensional network. The structure is also stabilized by the pi-pi interaction of heterocyclic HTBA(-) ions.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kliava J., Edelman I. S., Ivanova O. S., Ivantsov R. D., Bayukov O. A., Petrakovskaja E. A., Zaikovskiy V., Bruckental I., Yeshurun Y., Stepanov S.
Заглавие : Formation and evolution of magnetic nanoparticles in borate glass simultaneously doped with Fe and Mn oxides
Коллективы :
Место публикации : J. Appl. Phys.: AMER INST PHYSICS, 2008. - Vol. 104, Is. 10. - Ст.103917. - ISSN 0021-8979, DOI 10.1063/1.3021289
Примечания : Cited References: 37. - A financial support from the Russian Foundation for Basic Research (RFBR)-CNRS (Grant No. 07-02-92174) is highly appreciated. R. Ivantsov is grateful to the Russian Science Support Foundation. Y. Yeshurun acknowledges the support of the Israel Scienc Foundation (ISF).
Предметные рубрики: COBALT FERRITE PARTICLES
SUPERPARAMAGNETIC RESONANCE
GAMMA-FE2O3 NANOPARTICLES
MATRIX
SIZE
SYSTEMS
Ключевые слова (''Своб.индексиров.''): aluminium compounds--borate glasses--coercive force--faraday effect--heat treatment--iron compounds--magnetic hysteresis--magnetic particles--magnetic susceptibility--manganese compounds--mossbauer effect--nanoparticles--paramagnetic materials--potassium compounds--remanence--superparamagnetism--transmission electron microscopy--x-ray chemical analysis--atomic spectroscopy--auger electron spectroscopy--crystal structure--electric relays--electronic medical equipment--ferrite--ferrites--glass--heat treatment--hysteresis--hysteresis loops--magnetic properties--magnetic resonance measurement--magnetic susceptibility--magnetism--manganese--manganese compounds--molybdenum--nanoparticles--optical properties--ozone water treatment--polydispersity--superparamagnetism--borate glasses--concentration ratios--electron magnetic resonances--emr spectrums--experimental techniques--faraday rotations--glass compositions--glass matrixes--glass preparations--magnetic measurements--magnetic nano particles--magnetic orders--magnetically ordered systems--magneto-optical properties--manganese ferrites--mean diameters--mn oxides--phase states--polydisperse nanoparticles--remnant magnetizations--ssbauer spectroscopies--superparamagnetic--superparamagnetic states--thermal treatments--variable temperatures--magnetic materials
Аннотация: Evolution of the phase state of paramagnetic additions at various stages of synthesis and subsequent thermal treatment of glasses of the system Al(2)O(3)-K(2)O-B(2)O(3) simultaneously doped with Fe(2)O(3) and MnO is studied by means of a combination of experimental techniques: Faraday rotation (FR), electron magnetic resonance (EMR), transmission electron microscopy (TEM), Mossbauer spectroscopy, and magnetic measurements. Both FR and EMR show that magnetically ordered clusters occur already at the first stage of the glass preparation. In particular, for the ratio of the Fe and Mn oxides in the charge close to 3:2, fine magnetic nanoparticles are formed with characteristics similar to those of manganese ferrite. By computer simulating the EMR spectra at variable temperatures, a superparamagnetic nature of these nanoparticles is confirmed and their mean diameter is estimated as approximately 3.2 nm. In the thermally treated glasses larger magnetic nanoparticles are formed, giving rise to FR spectra, characteristic of magnetically ordered systems, and the EMR spectra different from those in as-prepared glasses but also showing superparamagnetic narrowing. The Mossbauer spectroscopy corroborates the manganese ferrite structure of the nanoparticles and indicates their coexistence in the ferrimagnetic and superparamagnetic states. The TEM shows the presence of polydisperse nanoparticles on the background of the glass matrix, and electron diffraction of a selected region containing larger particles indicates a crystal structure close to that of MnFe(2)O(4). Energy-dispersive atomic x-ray spectra confirm that the major part of Fe and Mn introduced to the glass composition is gathered in the particles, with the concentration ratio close to 2:1, characteristic of bulk MnFe(2)O(4). Magnetic hysteresis loops of samples subjected to an additional thermal treatment demonstrate a strong increase in the coercive force, remnant magnetization, and high-field magnetic susceptibility with temperature decrease. The consistent results obtained using various techniques demonstrate that the formation of nanoparticles with characteristics close to those of MnFe(2)O(4) confers to these glasses magnetic and magneto-optical properties typical of substances possessing magnetic order.
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