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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Knyazev Yu. V., Balaev D. A., Kirillov V. L., Bayukov O. A., Mart'yanov O. N.
Заглавие : Mossbauer spectroscopy study of the superparamagnetism of ultrasmall ε-Fe2O3 nanoparticles
Коллективы : Russian Science Foundation [17-12-01111]
Место публикации : JETP Letters. - 2018. - Vol. 108, Is. 8. - P.527-531. - ISSN 0021-3640, DOI 10.1134/S0021364018200092. - ISSN 1090-6487(eISSN)
Примечания : Cited References: 22. - This work was supported by the Russian Science Foundation (project no. 17-12-01111).
Предметные рубрики: High-temperature
Particles
ε-Fe2O3
Phase
Model
Аннотация: The superparamagnetism of an ensemble of ϵ-Fe2O3 nanoparticles with a mean size of 3.9 nm dispersed in a xerogel SiO2 matrix is studied by the Mössbauer spectroscopy method. It is shown that most nanoparticles at room temperature are in the superparamagnetic (unblocked) state. As the temperature decreases, the progressive blocking of the magnetic moments of the particles occurs, which is manifested in the Mössbauer spectra as the transformation of the quadrupole doublet into a Zeeman sextet. The analysis of the relative intensity of the superparamagnetic (quadrupole doublet) and magnetically split (sextets) spectral components in the range of 4–300 K provides the particle size distribution, which is in agreement with the transmission electron microscopy data. The values of the effective magnetic anisotropy constants (Keff) are determined, and the contribution of surface anisotropy (KS) is estimated for particles of various sizes. It is shown that the quantity Keff is inversely proportional to the particle size, which indicates the significant contribution of the surface to the magnetic state of the ϵ-Fe2O3 nanoparticles with the size of several nanometers.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Smirnova E. S., Alekseeva O. A., Dudka A. P., Khmelenin D. N., Frolov K. V., Lyubutina M. V., Gudim I. A., Lyubutin I. S.
Заглавие : Crystal structure and structural phase transition in bismuth-containing HoFe3(BO3)4 in the temperature range 11–500 K
Место публикации : Acta Crystallogr. B. - 2019. - Vol. 75. - P.954-968. - ISSN 20525192 (ISSN), DOI 10.1107/S2052520619010473
Примечания : Cited References: 37. - The authors are grateful to D. Yu. Chernyshov (SNBL, ESRF, Grenoble) for his assistance in obtaining the experimental data. This work was performed using the equipment of the Shared Research Center FSRC ‘Crystallography and Photonics’ RAS and was supported by the Russian Ministry of Education and Science (project RFMEFI62119X0035)This work was supported by the Ministry of Science and Higher Education within the State assignment FSRC ‘Crystallography and Photonics’ RAS and partially by the Russian Foundation for Basic Research (grant No. 17-02-00766)
Аннотация: An accurate single-crystal X-ray diffraction study of bismuth-containing HoFe3(BO3)4 between 11 and 500 K has revealed structural phase transition at Tstr = 365 K. The Bi atoms enter the composition from Bi2Mo3O12-based flux during crystal growth and significantly affect Tstr. The content of Bi was estimated by two independent methods, establishing the composition as (Ho0.96Bi0.04)Fe3(BO3)4. In the low-temperature (LT) phase below Tstr the (Ho0.96Bi0.04)Fe3(BO3)4 crystal symmetry is trigonal, of space group P3121, whereas at high temperature (HT) above 365 K the symmetry increases to space group R32. There is a sharp jump of oxygen O1 (LT) and O2 (LT) atomic displacement parameters (ADP) at Tstr. O1 and O2 ADP ellipsoids are the most elongated over 90–500 K. In space group R32 specific distances decrease steadily or do not change with decreasing temperature. In space group P3121 the distortion of the polyhedra Ho(Bi)O6, Fe1O6 and Fe2O6, B2O3 and B3O3 increases with decreasing temperature, whereas the triangles B1O3 remain almost equilateral. All BO3 triangles deviate from the ab plane with decreasing temperature. Fe–Fe distances in Fe1 chains decrease, while distances in Fe2 chains increase with decreasing temperature. The Mössbauer study confirms that the FeO6 octahedra undergo complex dynamic distortions. However, all observed distortions are rather small, and the general change in symmetry during the structural phase transition has very little influence on the local environment of iron in oxygen octahedra. The Mössbauer spectra do not distinguish two structurally different Fe1 and Fe2 positions in the LT phase. The characteristic temperatures of cation thermal vibrations were calculated using X-ray diffraction and Mössbauer data.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Frolov K. V., Lyubutin I. S., Alekseeva O. A., Smirnova E. S., Verin I. A., Temerov V. L., Bezmaternykh L. N., Gudim I. A., Artemov V. V., Dmitrieva T. V.
Заглавие : Dynamics of structural and magnetic phase transitions in ferroborate YFe3(BO3)4
Место публикации : J. Alloys Compd. - 2018. - Vol. 748. - P.989-994. - ISSN 09258388 (ISSN), DOI 10.1016/j.jallcom.2018.03.243
Примечания : Cited References: 58. - We thank Dr. A.P. Dudka for help in the low temperature XRD measurements and Dr. D.Yu. Chernyshov for help in the synchrotron XRD measurements. This study was supported by the Federal Agency of Scientific Organizations (Agreement No 007-ГЗ/Ч3363/26 ) in parts of energy-dispersive X-ray microanalysis, high-temperature XRD, and Mossbauer measurements, by the Russian Foundation for Basic Research (project #17-02-00766а ) in parts of low-temperature XRD and Mossbauer measurements, Russian Ministry of Education and Science and performed using the equipment of the Shared Research Center of the Shubnikov Institute of Crystallography of FSRC “Crystallography and Photonics” RAS.
Ключевые слова (''Своб.индексиров.''): multiferroics--rare-earth compounds--x-ray diffraction--mossbauer spectroscopy--crystal structure
Аннотация: X-ray analysis of the YFe3(BO3)4 single crystal revealed different behavior of parameters of the crystal cell with an increase in temperature from 25 to 500 K. The parameters a and b initially increase monotonically and then rise sharply in the range between 360 and 380 K, which corresponds to the structural phase transition. The parameter c initially decreases linearly upon heating and then begins to increase, passing through a minimum at 90 K. In the interval of 200–500 K the parameter c grows linearly and does not undergo anomalies at the structural phase transition. The results of Mössbauer measurements at 57Fe nuclei in the paramagnetic phase of YFe3(BO3)4 correlate well with the XRD data, but they do not separate the two structural states of iron ions Fe1 and Fe2 arising in the P3121 phase during the structural phase transition. The temperature of the magnetic phase transition TN = 39.42(16) K is established, below which the iron ions form a 3D magnetic order of the Heisenberg type. The calculated “Mössbauer” Debye temperature ΘM = 340(2) K turned out to be three times lower than the Debye temperature of the entire crystal lattice TD = 1020 K. Mössbauer data indicate a weak bonding between the helicoidal chains of iron and the rest of the crystal lattice.Рентгеновский анализ монокристалла YFe3(bo3-серии)4 выявил различие в поведении параметров кристаллической ячейки с увеличением температуры от 25 до 500 к. Параметры a и b сначала монотонно возрастают, а затем резко поднимется в диапазон между 360 и 380 К, что соответствует структурному фазовому переходу. Параметр c сначала линейно уменьшается при нагревании, а затем начинает возрастать, проходя через минимум при 90 K. В интервале 200-500 K параметр c растет линейно и не претерпевает аномалий при структурном фазовом переходе. Результаты Мёсбауэровской спектроскопии ядер 57Fe в парамагнитной фазе в YFe3(BO3)4 коррелируют с РСА, но они не разделяют двух структурных состояний ионов железа Fe1 и Fe2, возникающие в фазе P3121 в процессе структурного перехода. Установили температуру магнитного фазового перехода TN= 39.42(16) К, в результате которого ионы железа образуют 3D магнитный порядок типа Гейзенберга. Рассчитанная по Мёссбауэру Дебаевская температура QM= 340(2) K оказалась в три раза ниже температуры Дебая внутри кристаллической решетки TD= 1020 K. Данные Мёсбауэра указывают на слабую связь между геликоидальными цепочками железной и остальных кристаллических решеток.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Yakushkin S. S., Balaev D. A., Dubrovskiy A. A., Semenov S. V., Knyazev Yu. V., Bayukov O. A., Kirillov V. L., Ivantsov R. D., Edelman I. S., Martyanov O. N.
Заглавие : ε-Fe2O3 nanoparticles embedded in silica xerogel – Magnetic metamaterial
Место публикации : Ceram. Int. - 2018. - Vol. 44, Is. 15. - P.17852-17857. - ISSN 02728842 (ISSN), DOI 10.1016/j.ceramint.2018.06.254
Примечания : Cited References: 31. - This work was supported by the Russian Science Foundation, project no. 17-12-01111.
Ключевые слова (''Своб.индексиров.''): ε-fe2o3 iron oxide nanoparticles--metamaterial--mossbauer spectroscopy--magnetic properties--magnetic circular dichroism
Аннотация: A novel method for synthesizing a new metamaterial based on ε-Fe2O3 nanoparticles immobilized in the xerogel matrix was proposed. Samples with different contents of ε-Fe2O3 nanoparticles dispersed in silica xerogel were synthesized by impregnation of as prepared hydrogel with iron (II) salts with the subsequent calcination. The structure and magnetic properties of the prepared composites were studied by transmission electron microscopy, X-ray diffraction, Mössbauer spectroscopy, and static magnetic measurements. The absence of other iron oxide polymorphs, controllable particle size distribution, and high ε-Fe2O3 nanoparticle concentration in combination with the weak interparticle magnetic interactions ensured the preservation of the unique magnetic properties of individual ε-Fe2O3 nanoparticles and allowed us to obtain a novel metamaterial. The high optical transparency and homogeneity of the prepared composites made it possible to detect the magnetic circular dichroism (MCD) of the magnetic silica xerogel, which is typical of the ε-Fe2O3-based systems.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Semenov S. V., Dubrovskii A. A., Krasikov A. A., Popkov S. I., Yakushkin S. S., Kirillov V. L., Mart'yanov O. N.
Заглавие : Synthesis and magnetic properties of the core-shell Fe3O4/CoFe2O4 nanoparticles
Коллективы : Russian Science FoundationRussian Science Foundation (RSF) [17-12-01111]
Место публикации : Phys. Solid State. - 2020. - Vol. 62, Is. 2. - P.285-290. - ISSN 1063-7834, DOI 10.1134/S1063783420020043. - ISSN 1090-6460(eISSN)
Примечания : Cited References: 37. - This study was supported by the Russian Science Foundation, project no. 17-12-01111.
Предметные рубрики: MOSSBAUER
ENSEMBLE
Аннотация: The Fe3O4/CoFe2O4 nanoparticles with a core-shell structure with an average size of 5 nm have been obtained by codeposition from the iron and cobalt chloride solutions. An analysis of the magnetic properties of the obtained system and their comparison with the data for single-phase Fe3O4 (4 nm) and CoFe2O4 (6 nm) nanoparticles has led to the conclusion about a noticeable interaction between the soft magnetic (Fe3O4) and hard magnetic (CoFe2O4) phases forming the core and shell of hybrid particles.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Plotnikova A. A., Bragin V. I., Knyazev Yu. V.
Заглавие : Structural Characteristics and Processability of Sphalerite in Lead-Zinc Ore of the Gorevka Deposit
Место публикации : J. Min. Sci. - 2019. - Vol. 55, Is. 6. - P.995-1006. - ISSN 1062-7391, DOI 10.1134/S1062739119066381. - ISSN 1573-8736(eISSN)
Примечания : Cited References: 33
Аннотация: The theoretical and experimental substantiation of the behavior of ferrous sphalerite in magnetic separation is given in terms of the Gorevka deposit ore. In sphalerite of this deposit, the content of isomorphous iron ranges as 4-9%. The Mossbauer spectroscopy showed the singlet and two doublet lines of iron, demonstrating separate arrays of iron atoms in sphalerite lattice, with formation of Fe-Fe pairs and clusters of three or more iron atoms. It is found that distribution of iron in sphalerite into three forms coincides for magnetic and nonmagnetic products of zinc concentrate separation. It is determined that magnetic separation undivides sphalerite grains by the isomorphous iron content but is governed by the genetic features of the deposit formation-association of sphalerite with magnetic minerals (pyrrhotine and siderite) and the absence of such associations in galena.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Abramova G. M., Knyazev Yu. V., Bayukov O. A., Kubrin S. P.
Заглавие : Magnetic states of Fe2+ ions in FexMn1–xS induced by chemical pressure
Место публикации : Phys. Solid State. - 2021. - Vol. 63, Is. 1. - P.68-74. - ISSN 10637834 (ISSN), DOI 10.1134/S1063783421010029
Примечания : Cited References: 25. - The work was partially supported by the Ministry of Science and Higher Education of the Russian Federation (state contract in the sphere of scientific activities, Southern Federal University, 2020)
Аннотация: Influence of the chemical pressure (x) in single crystals of FexMn1 – xS (0.12 ≤ x ≤ 0.29) on the spin state of iron ions was studied by Mössbauer spectroscopy in the temperature range from 4.2 to 300 K. Peculiarities of formation of the paramagnetic and antiferromagnetic phases of solid solutions were found. Substitution of Fe2+ cations in the high-spin state for Mn2+ was found to occur in FexMn1 – xS as x changes. A decrease in the distance between the ions in FexMn1 – xS induces changes in the state of the Fe2+ ions in the samples with x = 0.25 and 0.29. The asymmetry parameter of the electric field gradient (EFG) tensor and the angle between the directions of the magnetic moment and the principal axis of the electric field gradient were found to change in the magnetically ordered phase at 4.2 K; the angle between the magnetic moment and the electric field gradient axis changes from 21° in the sample with x = 0.12 to 33° when x = 0.29.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Knyazev Yu. V., Chumakov A. I., Dubrovskiy A. A., Semenov S. V., Sergueev I., Yakushkin S. S., Kirillov V. L., Martyanov O. N., Balaev D. A.
Заглавие : Nuclear forward scattering application to the spiral magnetic structure study in epsilon-Fe2O3
Коллективы : Russian Science FoundationRussian Science Foundation (RSF) [17-12-01111, SC-4708]
Место публикации : Phys. Rev. B. - 2020. - Vol. 101, Is. 9. - Ст.094408. - ISSN 2469-9950, DOI 10.1103/PhysRevB.101.094408. - ISSN 2469-9969(eISSN)
Примечания : Cited References: 44. - We thank Dr. Natalia Kazak for assistance with the NFS measurements. This study was supported by the Russian Science Foundation, Project No. 17-12-01111. We thank the European Synchrotron Radiation Facility for provision of the synchrotron radiation facilities at the beamline ID18 (Exp. No. SC-4708)
Предметные рубрики: INCOMMENSURATE STRUCTURES
MOSSBAUER-SPECTROSCOPY
HIGH-TEMPERATURE
Аннотация: The ε−Fe2O3 magnetic structure has been analyzed using the synchrotron radiation source. Time spectra of nuclear forward scattering for isolated nanoparticles with an average size of 8 nm immobilized in a xerogel matrix have been recorded in the temperature range of 4–300K in applied magnetic fields of 0–4T in the longitudinal direction at the European Synchrotron Radiation Facility (ESRF, Grenoble, France). It has been found that the external magnetic field does not qualitatively change the Hhf(T) behavior, but makes a strong opposite impact on the hyperfine fields in the nonequivalent iron sites, leading to the divergence of Hhf polar angle dependences below 80 K. A complete diagram of the ε−Fe2O3 magnetic structure in the temperature range of 4–300K is proposed. At 300 K, the ε−Fe2O3 compound is confirmed to be a collinear ferrimagnet. The experimental results show that the magnetic transition at 150–80K leads to the formation of a noncollinear magnetic structure. Furthermore, in the range of the 80–4 K, the ground state of a magnetic spiral is established. The experimental results are supplemented by the analysis of the exchange interactions and temperature dependence of the magnetization in a magnetic field of 7 T.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kremneva A. M., Fedorov A. V., Bulavchenko O. A., Knyazev Yu. V., Saraev A. A., Yakovlev V. A., Kaichev V. V.
Заглавие : Effect of calcination temperature on activity of Fe2O3-Al2O3 nanocomposite catalysts in CO oxidation
Коллективы : Russian Science FoundationRussian Science Foundation (RSF) [17-73-20157]; National center of investigation of catalysts" at Boreskov Institute of Catalysis
Место публикации : Catal. Lett. - 2020. - Vol. 150. - P.3377-3385. - ISSN 1011-372X, DOI 10.1007/s10562-020-03250-8. - ISSN 1572-879X(eISSN)
Примечания : Cited References: 31. - This work was supported by the Russian Science Foundation (Grant No. 17-73-20157). The experiments were performed using facilities of the shared research center "National center of investigation of catalysts" at Boreskov Institute of Catalysis. The authors thank A.Yu. Gladky for the TPR measurements and Z.S. Vinokurov for the XRD measurements.
Предметные рубрики: MOSSBAUER
SPECTROSCOPY
CHEMISTRY
IRON
XPS
ADSORPTION
OXYGEN
FE
Аннотация: Nanocomposite Fe–Al oxide catalysts were prepared by the melting of iron and aluminum nitrates with the subsequent calcination in air at different temperatures. It was found that the catalysts calcined at 450 °C are more active in the oxidation of CO than the catalysts calcined at 700 °C. X-ray diffraction and X-ray photoelectron spectroscopy showed that all the catalysts consist of hematite, α-Fe2O3 nanoparticles, and Al2O3 in an amorphous state. Iron oxide is the active component, which provides the oxidation of CO, while alumina is a texture promoter. The increase in the calcination temperature leads to a minor increase in the average size of hematite nanoparticles and an insignificant decrease in the specific surface area. Kinetic measurements showed that the oxidation of CO over the Fe–Al catalysts calcined at 450 and 700 °C proceeds with the activation energy of 61–69 and 91 kJ/mol, respectively. This means that the low-temperature and high-temperature catalysts contain different active species. Temperature-programmed reduction with CO indicated that the decrease in the calcination temperature improves the reducibility of the Fe-Al nanocomposites. According to 57Fe Mössbauer spectroscopy, the low-temperature catalysts contain hydrated iron oxides (acagenite and ferrihydrite) and a significant amount of highly defective hematite, which is absent in the high-temperature catalyst. These species can provide the enhanced activity of the low-temperature catalysts in the oxidation of CO.
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10.

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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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Anshits A. G., Bayukov O. A., Kondratenko E. V., Anshits N. N., Pletnev O. N., Rabchevskii E. V., Solovyov L. A.
Заглавие : Catalytic properties and nature of active centers of ferrospheres in oxidative coupling of methane
Коллективы : Russian Science Foundation [14-13-00289]
Место публикации : Appl. Catal. A-Gen.: Elsevier Science, 2016. - Vol. 524. - P.192-199. - ISSN 0926-860X, DOI 10.1016/j.apcata.2016.06.032. - ISSN 1873-3875(eISSN)
Примечания : Cited References:47. - This study was supported by the Russian Science Foundation (project no. 14-13-00289).
Предметные рубрики: GLASS CRYSTAL CATALYSTS
MAGNETIC-PROPERTIES
PROFILE REFINEMENT
FLY-ASH
MOSSBAUER
MICROSPHERES
PERFORMANCE
CONVERSION
ETHYLENE
OXIDE
Ключевые слова (''Своб.индексиров.''): methane coupling--active center--ferrospinel--mossbauer spectroscopy
Аннотация: Ferrospheres with the Fe2O3 content in the range from 76 to 97 wt% were applied as catalysts for the oxidative coupling of methane (OCM). To identify their phase composition and distribution of iron sites, the ferrospheres were characterized by X-ray powder diffraction and Mossbauer spectroscopy before and after the OCM reaction. Magnetite-based ferrite spinel, hematite and aluminosilicate glasses were established to be the main phases. The ferrospinel of all ferrospheres partially oxidized to hematite after the OCM reaction. It was established that the yield of C-2-hydrocarbons sharply increased at the ferrospheres with Fe2O3 content higher than 89 wt% The spinel phase of these ferrospheres includes Fevv3+(B) sites with a Ca2+ tetrahedral cation and an octahedral cation vacancy among the nearest neighbors. A linear correlation between the yield of C-2-hydrocarbons (ethane and ethylene) and the content of such sites was established, thus indicating that their electrophilic oxygen species participate in selective CH4 conversion to C2H6. (C) 2016 Elsevier B.V. All rights reserved.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bayukov O. A., Petrakovskii G. A., Sablina K. A., Savitskii A. F.
Заглавие : Mossbauer study of copper ferrite
Место публикации : Fiz. Tverd. Tela: MEZHDUNARODNAYA KNIGA, 1995. - Vol. 37, Is. 8. - P.2409-2412. - ISSN 0367-3294
Примечания : Cited References: 9
Предметные рубрики: CU-ZN FERRITE
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Frolov G. I., Bayukov O. A., Zhigalov V. S., Kveglis L. I., Myagkov V. G.
Заглавие : Electron-microscopy and mossbauer study of superlattices in iron films
Место публикации : JETP Letters. - 1995. - Vol. 61, Is. 1. - P.63-67. - ISSN 0021-3640
Примечания : Cited References: 6
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Krasikov A. A., Stolyar S. V., Iskhakov R. S., Ladygina V. P., Yaroslavtsev R. N., Bayukov O. A., Vorotynov A. M., Volochaev M. N., Dubrovskiy A. A.
Заглавие : Change in the magnetic properties of nanoferrihydrite with an increase in the volume of nanoparticles during low-temperature annealing
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2016. - Vol. 58, Is. 9. - P.1782-1791. - ISSN 10637834 (ISSN), DOI 10.1134/S1063783416090092
Примечания : Cited References: 32. - This study was supported by the Ministry of Education and Science of the Russian Federation within the State Task for 2014-2016.
Предметные рубрики: FERRIHYDRITE NANOPARTICLES
BACTERIAL FERRIHYDRITE
FERRITIN
HYSTERESIS
MOSSBAUER
ORIGIN
Аннотация: The results of the investigation into the effect of low-temperature annealing of a powder of nanoparticles of bacterial ferrihydrite on its magnetic properties have been presented. It has been found that an increase in the time (up to 240 h) and temperature (in the range from 150 to 200°C) of annealing leads to a monotonic increase in the superparamagnetic blocking temperature, the coercive force, and the threshold field of the opening of the magnetic hysteresis loop (at liquid-helium temperatures), as well as to an increase in the magnetic resonance line width at low temperatures and in the magnetic susceptibility at room temperature. At the same time, according to the results of the analysis of the Mossbauer spectra, the annealing of ferrihydrite does not lead to the formation of new iron oxide phases. Most of these features are well consistent with the fact that the low-temperature annealing of ferrihydrite causes an increase in the size of nanoparticles, which is confirmed by the results of transmission electron microscopy studies. © 2016, Pleiades Publishing, Ltd.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Yakushkin S. S., Balaev D. A., Dubrovskiy A. A., Semenov S. V., Shaikhutdinov K. A., Kazakova M. A., Bukhtiyarova G. A., Martyanov O. N., Bayukov O. A.
Заглавие : Evolution of the Fe3+ ion local environment during the phase transition ε-Fe2O3 → α-Fe2O3
Место публикации : J. Supercond. Nov. Magn. - 2018. - Vol. 31, Is. 4. - P.1209–1217. - ISSN 15571939 (ISSN), DOI 10.1007/s10948-017-4307-y
Примечания : Cited References: 37. - The work was supported by the Russian Science Foundation (Grant No. 17-12-01111).
Ключевые слова (''Своб.индексиров.''): ε−fe2o3 iron oxide nanoparticles--phase transition--structure size effect--magnetic properties--mossbauer spectroscopy
Аннотация: Evolution of the local environment of Fe3+ ions in deposited Fe2O3/SiO2 nanoparticles formed in samples with different iron contents was investigated in order to establish the conditions for obtaining the stable ε-Fe2O3/SiO2 samples without impurities of other iron oxide polymorphs. Microstructure of the samples with an iron content of up to 16% is studied by high-resolution transmission electron microscopy, X-ray diffraction analysis, and Mössbauer spectroscopy, and their magnetic properties are examined. At iron concentrations below 6%, calcinations of iron-containing precursor nanoparticles in a silica gel matrix lead to the formation of the ε-Fe2O3 iron oxide polymorphic modification without foreign phase impurities, while at the iron concentration in the range of 6–12%, the hematite phase forms in the sample in the fraction of no more than 5%. It is concluded on the basis of the data obtained that the spatial stabilization of iron-containing particles is one of the main factors facilitating the formation of the ε-Fe2O3 phase in a silica gel matrix without other iron oxide polymorphs. It is demonstrated that the increase in the iron content leads to the formation of larger particles in the sample and gradual changes of the Fe3+ ion local environment during the phase transition ε-Fe2O3 → α-Fe2O3.
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16.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Сильянов С. А., Князев, Юрий Владимирович, Некрасова Н. А.
Заглавие : Cтруктура арсенопирита золоторудных месторождений енисейского кряжа по данным мессбауэровской спектроскопии
Коллективы : Министерство природных ресурсов и экологии Российской Федерации, Федеральное агентство по недропользованию, Всероссийский научно-исследовательский геологический институт им. А. П. Карпинского, Международная конференция молодых ученых и специалистов памяти академика А. П. Карпинского
Место публикации : Взаимодействие учрежд. Роснедра, Минобрнауки России и РАН при регион. геол. изучении территории РФ и ее континент. шельфа: материалы конференции: ВСЕГЕИ, 2017. - С. 813-815. - ISBN 978-5-93761-255-7
Примечания : Библиогр.: 6
Аннотация: Проведено мессбауэровское исследование структуры арсенопиритов золоторудныхместорождений Енисейского кряжа. В структуре минерала обнаружены неэквивалентные позиции атомов железа, которые можно соотнести с таковыми в пирите, леллингите и арсенопирите. В изученных арсенопиритах одновременно возникают позиции железа с составом координационной сферы: {6S}, {5S1As}, {4S2As}, {3S3As}, {2S4As}, {1S5As}, {6As}. Для арсенопиритовой позиции {3As3S} установлены дополнительные конфигурации лигандного окружения, что указывает на разупорядочение арсенопиритовой фазы. Заселенность позиций железа с различными конфигурациями лигандов зависит от соотношения S и As в образце. The Mossbauer study of the structure of arsenopyrite from the gold ore deposits of the Yenisei Ridge has been performed. The non-equivalent positions of iron atoms have been identiﬁ ed in the structure of the mineral. They correspond conventionally to pyrite, lollingite and arsenopyrite. In the studied arsenopyrites the iron positions occur simultaneously with the composition of the coordination sphere: {6S}, {5S1As}, {4S2As}, {3S3As}, {2S4As}, {1S5As}, and {6As}. Additional conﬁ gurations of the ligand surroundings have been identiﬁ ed for the arsenopyrite position {3As3S}. This indicates the disordering of the arsenopyrite phase. The occupancy of the iron positions with different ligand conﬁ gurations depends on the S to As ratio in the specimen.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Кирик С. Д., Сазонов А. М., Сильянов С. А., Баюков, Олег Артемьевич
Заглавие : Исследование разупорядочения в структуре природного арсенопирита рентгеноструктурным анализом поликристаллов и ядерным гамма-резонансом
Место публикации : Журн. СФУ. Сер. "Техника и технологии". - 2017. - Т. 10, № 5. - С. 578-592. - ISSN 1999-494X, DOI 10.17516/1999-494X-2017-10-5-578-592; J. Sib. Fed. Univ. Eng. Technol.
Примечания : Библиогр.: 12
Ключевые слова (''Своб.индексиров.''): arsenopyrite--crystal structure--disordering--x-ray diffraction analysis--mossbauer spectroscopy--арсенопирит--кристаллическая структура--разупорядочение--рентгеноструктурный анализ--месбауэровская спектроскопия
Аннотация: Для выявления особенностей разупорядочения кристаллической структуры в геологических условиях проведено сравнительное рентгеноспектральное, рентгеноструктурное и мессбауэровское исследование природных образцов арсенопирита FeAsS. Для исследования отобрано три практически однофазных поликристаллических образца из руд месторождений «Благодатное» и «Олимпиада» (Красноярский край) с химическим составом близким к стехиометрическому (I), с избытком серы (II) и мышьяка (III). Расшифровка мессбауэровских спектров обнаружила наличие в веществе трех форм Fe(2+). Первая ассоциирована с октаэдрическим окружением железа типа [As 3 S 3 ], вторая [S 6 ] и третья [As 6 ] формы условно связаны с минералами FeS 2 и FeAs 2 . Согласно данным ЯГР в образце (I) атомы железа на 95 % находятся в основной форме. Другие формы присутствуют в примерно равных долях. В образцах (II) и (III) обнаружено 73 и 56 % железа в основной форме, в качестве побочных форм преобладают FeS 2 или FeAs 2 соответственно. Уточнение кристаллической структуры по рентгеновским поликристаллическим данным проведено в Пр.гр. P2 1 /c. Атомы железа размещаются в единственной катионной позиции структуры арсенопирита. Структурные изменения происходят в анионной подрешетке путем разупорядочения основного координационного окружения железа [FeAs 3 S 3 ] до состояния, описываемого как [Fe(As 3-х S x )(S 3-y As y )]. Установлено, что взаимное замещение анионов сопровождается небольшим сдвигом атомной позиции из-за разницы межатомных состояний Fe-S и Fe-As. Разупорядоченное состояние допускает преобладание одного из анионов. В результате в реальном кристалле образуется набор состояний атома железа, различающихся по составу координационной сферы и по пространственной конфигурации заместителей в ней. Разупорядочение координационного окружения количественно соответствует данным ЯГР-спектроскопии.The features of the FeAsS arsenopyrite crystal structure disordering occurred in geological conditions were studied by elemental analysis, X-ray diffraction and Mossbauer techniques using natural samples. There were selected and studied three practically single-phase polycrystalline samples of Blagodatnoe and Olimpiada ore deposits (Krasnoyarsk region) with the chemical composition close to stoichiometry (I), with excess sulfur (II) and arsenic (III). The Mossbauer (NGR) study detected the presence of the three forms of Fe(2+) in the substance. The first was associated with octahedral iron environment of [As 3 S 3 ] type, the second with [S 6 ] and third with [As 6 ] forms conventionally associated with ordered arsenopyrite and FeS 2 , FeAs 2 minerals. According to NGR data the iron atoms at 95 % were in the main form in the sample (I). Other forms were present about in equal parts. There were detected 73 % and 56 % of iron in its basic form for samples (II) and (III) respectively with FeS 2 , FeAs 2 dominated as by-forms.X-ray powder crystal structure refinement was carried out in Space group P2 1 /c. It was established that the iron atoms were in cationic positions of the arsenopyrite. Additional crystallographic positions of iron were not detected. The structure variation mainly occurred in the anion sublattice disordering the primary iron coordination from [FeAs 3 S 3 ] to the condition described as [Fe(As 3-х S x )(S 3-y As y )]. It was established that the mutual substitution of anions was accompanied by a small shift of the atomic positions due to the difference in the interatomic distances of Fe-S and Fe-As. Disordered condition admits the predominance of one of the anions. As a result, there are the set of the iron atom states with different composition and spatial configuration of the substituents in the coordination sphere in the real crystal. The disordering coordination of iron atoms obtained from X-ray diffracted data quantitatively corresponds to the data of NGR spectroscopy.
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18.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Frolov K. V., Lyubutin I. S., Smirnova E. S., Alekseeva O. A., Bezmaternykh L. N., Gudim, I. A.
Заглавие : Magnetic and structural properties of the NdFe3(BO3)4 AND SmFe3(BO3)4 multiferroics studied with mossbauer spectroscopy
Коллективы : Moscow International Symposium on Magnetism, Московский государственный университет им. М.В. Ломоносова, Российский фонд фундаментальных исследований
Место публикации : Moscow International Symposium on Magnetism (MISM-2017): 1-7 July 2017 : book of abstracts. - 2017. - Ст.4PO-J-42. - P.921 (Шифр 29916280)
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ivantsov R. D., Lin C. -R., Ivanova O. S., Altunin R. R., Knyazev Yu. V., Molokeev M. S., Zharkov S. M., Chen Y. -Z., Lin E. -S., Chen B. -Y., Shestakov N. P., Edelman I. S.
Заглавие : Mossbauer and MCD spectroscopy of the Fe3S4 nanoparticles synthesized by the thermal decomposition method with two different surfactants
Место публикации : Curr. Appl. Phys. - 2021. - Vol. 25. - P.55-61. - ISSN 15671739 (ISSN), DOI 10.1016/j.cap.2021.02.013
Примечания : Cited References: 30. - The reported study was funded by Joint Research Project of Russian Foundation for Basic Research № 19-52-52002 and Ministry of Science and Technology, Taiwan MOST № 108-2923-M-153-001-MY3 and № 106-2112-M-153-001-MY3 , and by Russian Foundation for Basic Research with Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science , the research project number 19-42-240005 : “Features of the electronic structure, magnetic properties and optical excitations in nanocrystals of the multifunctional magnetic chalcogenides Fe3S4 and FeSe”. The electron microscopy and electron diffraction investigations were conducted in the SFU Joint Scientific Center supported by the State assignment (#FSRZ-2020-0011) of the Ministry of Science and Higher Education of the Russian Federation. The thermal-gravity measurements were carried out with the differential Scanning Calorimeter DSC 204 F-1 Phoenix (NETZSCH) in the Krasnoyarsk Regional Center of Research Equipment of Federal Research Center «Krasnoyarsk Science Center SB RAS»
Аннотация: Greigite (Fe3S4) nanoparticles (NPs) were fabricated by the thermal decomposition method using two different surfactants: oleylamine (OLA) and 1-hexadecylamine (HDA). In both cases, the synthesized NPs were characterized as the Fe3S4 nanocrystals with minor inclusions of Fe9S11 phase. FT-IR spectroscopy and thermo-gravimetric analysis allow concluding about OLA or HDA shells covering magnetic core of NPs. Mossbauer spectra has revealed deviations of iron ions distribution among crystal positions from that presented in literature for pure greigite. In accordance with these deviations, the pronounce changes are observed in the magnetic circular dichroism (MCD) spectra which manifest themselves as the spectrum shift to higher energies of electromagnetic waves and redistribution of the MCD maximum intensities. These effects are associated with a change in the density of electronic states in the samples due to the redistribution of iron ions between octahedral and tetrahedral positions in nanocrystals under the influence of surfactants.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mikhlin Y. L., Likhatski M. N., Romanchenko A. S., Vorobyev S. A., Tomashevich Y. V., Fetisova O. Yu., Bayukov O. A., Knyazev Yu. V., Nemtsev I. V., Karasev S. V., Karacharov A. A., Borisov R. V.
Заглавие : Valleriite-containing ore from Kingash deposit (Siberia, Russia): Mossbauer and X-ray photoelectron spectroscopy characterization, thermal and interfacial properties
Место публикации : J. Sib. Fed. Univ. Chem. - 2022. - Vol. 15, Is. 3. - P.303-317. - ISSN 19982836 (ISSN), DOI 10.17516/1998-2836-0294; Журн. СФУ. Химия
Примечания : Cited References: 25. - This research was funded by the Russian Foundation for Basic Research, Krasnoyarsk Territory Science Foundation and Krasnoyarsk Territory Administration, grant number 20-43-242903. Facilities of the Krasnoyarsk Regional Center of Research Equipment of Federal Research Center «Krasnoyarsk Science Center SB RAS» were employed in the work
Аннотация: Valleriite, (Cu,Fe)S2×n(Mg,Al,Fe)(OH)2, and related layered minerals are of interest due to their unusual two-dimensional structure, formation mechanisms, physical and chemical properties, and potential involvement into mineral processing and materials science applications. Here, we have studied Kingash Cu-Ni ore samples containing 10-25% of valleriite in association with serpentines (lizardite and chrysotile) and magnetite using scanning electron microscopy and electron microprobe analysis, Mössbauer spectroscopy, X-ray photoelectron spectroscopy (XPS), thermal analysis and zeta potential measurement. The data are compared with those for Al-doped valleriite synthesized via a hydrothermal route. It was found that the Kingash valleriite contains excessive iron relative to CuFeS2 stoichiometry, which mainly occurs, leaving aside magnetite, as Fe3+-OH species in hydroxide layers of valleriite and minor Fe centers in serpentines. Thermal dehydroxylation of hydroxide layers of valleriites occurs near 500oC in inert atmosphere; in air, sulfide sheets oxidize with an exothermal peak at 447oC, and sulfur oxides don't volatilize but react with hydroxide groups of valleriite rather than serpentines. Zeta potential measurements of coarse ore particles using the flow potential technique suggested that the surface of valleriite is negatively charged in a wide pH range while the positive values at low pHs for fine particles are inflicted by serpentine. The findings demonstrate close resemblance of the natural and synthetic Al-doped valleriites, and the key role of valleriite, despite its moderate content, for the interfacial characteristics of the valleriite-bearing ores.Валлериит, (Cu, Fe)S2×n(Mg, Al, Fe)(OH)2 и родственные ему слоистые минералы представляют интерес в связи с их необычной двумерной структурой, механизмами образования, физическими и химическими свойствами и возможностью применения в процессах переработки полезных ископаемых и материаловедения. В настоящей работе с помощью сканирующей электронной микроскопии и электронного микрозондового анализа, мессбауэровской спектроскопии, рентгеновской фотоэлектронной спектроскопии (РФЭС), термического анализа и измерения дзета-потенциала нами были изучены образцы медно-никелевых руд Кингашского месторождения, содержащие 10–25 % валлериита в ассоциации с серпентинами (лизардит и хризотил) и магнетитом. Было проведено сравнение полученных данных с результатами измерений легированного алюминием валлериита, синтезированного гидротермальным способом. Установлено, что валлериит Кингашского месторождения содержит избыточное железо по отношению к стехиометрии CuFeS2, которое представлено в основном, не считая магнетита, в виде центров Fe3+-OH, расположенных в гидроксидных слоях валлериита и небольшого числа примесей Fe в серпентинах. Термическое дигидроксилирование гидроксидных слоев валлериитов происходит около 500 °C в инертной атмосфере; на воздухе сульфидные слои окисляются с экзотермическим пиком при 447 °C, а оксиды серы не улетучиваются, а реагируют скорее с гидроксидными группами валлериита, чем с серпентинами. Измерения дзета-потенциала крупных частиц руды с использованием метода потенциала протекания показали, что поверхность валлериита отрицательно заряжена в широком диапазоне рН, в то время как положительные показатели при низких значениях рН для более мелких частиц обусловлены присутствием серпентина. Полученные данные демонстрируют близкое сходство природного и синтетического валлериитов, легированного алюминием, и его ключевую роль для межфазных характеристик валлериитсодержащих руд, даже при его умеренном содержании.
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