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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Hu T., Gao Y., Molokeev M. S., Xia Z., Zhang Q.
Заглавие : Non-stoichiometry in Ca2Al2SiO7 enabling mixed-valent europium toward ratiometric temperature sensing
Место публикации : Sci. China Mater. - 2019. - Vol. 62, Is. 12. - P.1807–1814. - ISSN 20958226 (ISSN), DOI 10.1007/s40843-019-1202-x
Примечания : Cited References: 53. - This work was supported by the National Natural Science Foundation of China (51722202, 51972118 and 51572023), the Guangdong Provincial Science & Technology Project (2018A050506004), and Innovation Projects of Department of Education of Guangdong Province (2018KQNCX265).
Аннотация: Eu2+/Eu3+ mixed-valence couple co-doped material holds great potential for ratiometric temperature sensing owing to its different electronic configurations and electron-lattice interaction. Here, the correlation of nonstoichiometry in chemical composition, phase structures and luminescence propertis of Ca2Al2Si1−xO7:Eu is discussed, and controlled Eu2+/Eu3+ valence and tunable emission appear with decreasing Si content. It is found that the 2Ca2+ + Si4+ ↔ Eu2+ + Eu3+ + Al3+ cosubstitution accounts for the structural stability and charge balance mechanism. Benefiting from the diverse thermal dependent emission behaviors of Eu2+ and Eu3+, Ca2Al2Si1−xO7:Eu thermometer exhibits excellent temperature sensing performances with the maximum absolute and relative sensitivity being 0.024 K−1 (at 303 K) and 2.46% K−1 (at 443 K) and good signal discriminability. We propose that the emission quenching of Eu2+ is ascribed to 5d electrons depopulation through Eu2+/Eu3+ intervalence charge transfer state, while the quenching of Eu3+ comes from multi phonon relaxation. Our work demonstrates the potential of Ca2Al2Si1−xO7:Eu for noncontact optical thermometry, and also highlights mixed valence europium containing com pounds toward temperature sensing.
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Denisenko Y. G., Molokeev M. S., Krylov A. S., Aleksandrovsky A. S., Oreshonkov A. S., Atuchin V. V., Azarapin N. O., Plyusnin P. E., Sal'nikova E. I., Andreev O. V.
Заглавие : High-temperature oxidation of europium (II) sulfide
Место публикации : J. Ind. Eng. Chem. - 2019. - Vol. 79. - P.62-70. - ISSN 1226086X (ISSN) , DOI 10.1016/j.jiec.2019.05.006
Примечания : Cited References: 68. - The authors are grateful for the support from RFBR ( 18-02-00754 , 18-08-00985 , and 18-32-20011 ). This study was also supported by the Russian Science Foundation (project 19-42-02003 , in part of conceptualization).
Аннотация: The process of high-temperature oxidation of EuS in the air was explored in the temperature range of 500–1000 °C. The oxidation reaction enthalpy was determined (ΔH0exp = −1718.5 kJ/mol). The study of oxidation products allowed to establish the mechanism of EuS oxidation with oxygen. At 500–600 °C, EuS is oxidized to a mixture of Eu3+-containing compounds (Eu3S4, Eu2O2S). In the range of 700–1000 °C, only europium oxysulfate Eu2O2SO4 is formed. The structure refinement for Eu2O2SO4 was performed by the Rietveld method. The luminescence intensity of europium oxysulfate Eu2O2SO4 with characteristic 4f-4f transitions from the 5D0 state was investigated as a function of oxidation temperature.
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Denisova L. T., Molokeev M. S., Irtyugo L. A., Beletskii V. V., Kargin, Yu. F., Denisov V. M.
Заглавие : Synthesis, structure, and thermophysical properties of EuGaGe2O7
Место публикации : Inorg. Mater. - 2020. - Vol. 56, Is. 8. - P.854-858. - ISSN 0020-1685, DOI 10.1134/S002016852008004X. - ISSN 1608-3172(eISSN)
Примечания : Cited References: 18
Предметные рубрики: TEMPERATURE HEAT-CAPACITY
THERMODYNAMIC PROPERTIES
CRYSTAL-STRUCTURE
Аннотация: The europium gallium germanate EuGaGe2O7 has been prepared by solid-state reaction in air in the temperature range 1273–1473 K using a stoichiometric mixture of Eu2O3, Ga2O3, and GeO2. Its crystal structure has been determined by X-ray diffraction (sp. gr. P21/c, a = 7.1693(7) Å, b = 6.57008(6) Å, c = 12.7699(1) Å, β = 117.4522(5)°, V = 533.768(8) Å3). The heat capacity of polycrystalline samples has been determined by differential scanning calorimetry in the temperature range 350–1053 K and the experimental data have been used to calculate the thermodynamic properties (enthalpy increment, entropy change, and reduced Gibbs energy change) of EuGaGe2O7.
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4.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Denisenko Yu. G., Atuchin V. V., Molokeev M. S., Aleksandrovsky A. S., Oreshonkov A. S., Andreev O. V.
Заглавие : Synthesis, crystall structure, thermochemical and luminescent-spectral properties of europium sulphates
Коллективы : Mendeleev Congress on General and Applied Chemistry, Менделеевский съезд по общей и прикладной химии, Российская академия наук, Российское химическое общество им. Д.И. Менделеева, Российский фонд фундаментальных исследований, Санкт-Петербургский государственный университет, Санкт-Петербургский горный университет, Российский союз химиков, Институт физической химии и электрохимии имени А.Н. Фрумкина РАН
Место публикации : XXI Mendeleev Congress on General and Applied Chemistry: Book of abstracts : in 6 vols. - 2019. - Vol. 2b. - P.90
Примечания : Cited References: 2
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Chen M., Xia Z., Molokeev M. S., Lin C. C., Su C., Chuang Y. -C., Liu Q.
Заглавие : Probing Eu2+ luminescence from different crystallographic sites in Ca10M(PO4)7:Eu2+ (M = Li, Na, and K) with β-Ca3(PO4)2-type structure
Место публикации : Chem. Mater.: American Chemical Society, 2017. - Vol. 29, Is. 17. - P.7563-7570. - ISSN 08974756 (ISSN), DOI 10.1021/acs.chemmater.7b02724
Примечания : Cited References: 34. - The present work was supported by the National Natural Science Foundation of China (Grants 51722202, 91622125, and 51572023), Natural Science Foundations of Beijing (2172036), and Fundamental Research Funds for the Central Universities (FRF-TP-16-002A3). C.C.L. and C.C.S. acknowledge the financial support from the Ministry of Science and Technology of Taiwan (Contract No. MOST 104-2113-M-027-007-MY3), and M. Molokeev acknowledges support of the Russian Foundation for Basic Research (17-52-53031).
Ключевые слова (''Своб.индексиров.''): calcium--doping (additives)--excited states--light emission--lithium--luminescence--phosphors--photoluminescence--positive ions--rietveld refinement--single crystals--color tuning--crystallographic sites--different distributions--emission bands--local environments--long wavelength bands--luminescent centers--power diffraction data--europium
Аннотация: Eu2+ local environments in various crystallographic sites enable the different distributions of the emission and excitation energies and then realize the photoluminescence tuning of the Eu2+ doped solid state phosphors. Herein we report the Eu2+-doped Ca10M(PO4)7 (M = Li, Na, and K) phosphors with β-Ca3(PO4)2-type structure, in which there are five cation crystallographic sites, and the phosphors show a color tuning from bluish-violet to blue and yellow with the variation of M ions. The difference in decay rate monitored at selected wavelengths is related to multiple luminescent centers in Ca10M(PO4)7:Eu2+, and the occupied rates of Eu2+ in Ca(1), Ca(2), Ca(3), Na(4), and Ca(5) sites from Rietveld refinements using synchrotron power diffraction data confirm that Eu2+ enters into four cation sites except for Ca(5). Since the average bond lengths d(Ca-O) remain invariable in the Ca10M(PO4)7:Eu2+, the drastic changes of bond lengths d(M-O) and Eu2+ emission depending on the variation from Li to Na and K can provide insight into the distribution of Eu2+ ions. It is found that the emission band at 410 nm is ascribed to the occupation of Eu2+ in the Ca(1), Ca(2), and Ca(3) sites with similar local environments, while the long-wavelength band (466 or 511 nm) is attributed to Eu2+ at the M(4) site (M = Na and K). We show that the crystal-site engineering approach discussed herein can be applied to probe the luminescence of the dopants and provide a new method for photoluminescence tuning.
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhao M., Xia Z., Molokeev M. S., Ning L., Liu Q.
Заглавие : Temperature and Eu2+-doping induced phase selection in NaAlSiO4 polymorphs and the controlled yellow/blue emission
Место публикации : Chem. Mater.: American Chemical Society, 2017. - Vol. 29, Is. 15. - P.6552-6559. - ISSN 08974756 (ISSN), DOI 10.1021/acs.chemmater.7b02548
Примечания : Cited References: 48. - The present work was supported by the National Natural Science Foundation of China (Grants 91622125 and 51572023 and 11574003), Natural Science Foundations of Beijing (2172036), and Fundamental Research Funds for the Central Universities (FRF-TP-16-002A3). L.N. acknowledges the support from the Special and Excellent Research Fund of Anhui Normal University.
Ключевые слова (''Своб.индексиров.''): chemical modification--coordination reactions--europium--light emitting diodes--photoluminescence--functional properties--high color rendering index--local coordination structures--near ultraviolet excitations--structural transformation--synthesis temperatures--temperature dependent--white light emitting diodes--density functional theory
Аннотация: The union of temperature-dependent phase transition and relating structural transformation via modification of chemical compositions is of fundamental importance for the discovery of new materials or their functional properties optimization. Herein, the synthesis temperature and Eu2+-doping content induced phase selection and variations of the local structures in nepheline, low-carnegieite and high-carnegieite types of NaAlSiO4 polymorphs were studied in detail. The luminescence of Eu2+ in low-carnegieite and nepheline phases shows blue (460 nm) and yellow (540 nm) broad-band emissions, respectively, under near-ultraviolet excitation. The photoluminescence evolution can be triggered by the different synthesis temperatures in relation to the Eu2+-doping concentration, as corroborated by density functional theory calculations on the local coordination structures and corresponding mechanical stabilities in terms of the Debye temperature. The fabricated white light-emitting diode device with high color rendering index demonstrates that the multicolor phosphors from one system provides a new gateway for the photoluminescence tuning. © 2017 American Chemical Society.
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Atuchin V. V., Aleksandrovsky A. S., Bazarov B. G., Bazarova J. G., Chimitova, Olga D., Denisenko, Yuriy G., Gavrilova T. A., Krylov A. S., Maximovskiy, Eugene A., Molokeev M. S., Oreshonkov A. S., Pugachev, Alexey M., Surovtsev, Nikolay V.
Заглавие : Exploration of structural, vibrational and spectroscopic properties of self-activated orthorhombic double molybdate RbEu(MoO4)2 with isolated MoO4 units
Коллективы : RFBR [16-52-48010, 17-52-53031, 18-03-00557]; Ministry of Science and Higher Education of the Russian Federation [0339-2016-0007]; Act 211 Government of the Russian Federation [02.A03.21.0011]; Ministry of Education and Science of the Russian Federation [4.1346.2017/4.6]
Место публикации : J. Alloy. Compd. - 2019. - Vol. 785. - P.692-697. - ISSN 0925-8388, DOI 10.1016/j.jallcom.2019.01.013. - ISSN 1873-4669(eISSN)
Примечания : Cited References: 42. - The reported study was funded by RFBR according to research projects 16-52-48010, 17-52-53031 and 18-03-00557. Besides, this study was supported by the Ministry of Science and Higher Education of the Russian Federation (project 0339-2016-0007). The work was supported by Act 211 Government of the Russian Federation, contract No 02.A03.21.0011. Additionally, the work was partially supported by the Ministry of Education and Science of the Russian Federation (4.1346.2017/4.6).
Предметные рубрики: MORPHOLOGY-CONTROLLED SYNTHESIS
LUMINESCENCE PROPERTIES
Ключевые слова (''Своб.индексиров.''): rubidium europium molybdate--solid state reaction--rietveld refinement--dsc--raman luminescence
Аннотация: RbEu(MoO4)2 is synthesized by the two-step solid state reaction method. The crystal structure of RbEu(MoO4)2 is defined by Rietveld analysis in space group Pbcn with cell parameters a = 5.13502(5), b = 18.8581(2) and c = 8.12849(7) Å, V = 787.13(1) Å3, Z = 4 (RB = 0.86%). This molybdate possesses its phase transition at 817 K and melts at 1250 K. The Raman spectra were measured with the excitation at λ = 1064 and 514.5 nm. The photoluminescence spectrum is evaluated under the excitation at 514.5 nm. The absolute domination of hypersensitive 5D0→7F2 transition is observed. The ultranarrow 5D0→7F0 transition in RbEu(MoO4)2 is positioned at 580.2 nm being 0.2 nm blue shifted, with respect to that in Eu2(MoO4)3.
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Denisenko Y. G., Aleksandrovsky A. S., Atuchin V. V., Krylov A. S., Molokeev M. S., Oreshonkov A. S., Shestakov N. P., Andreev O. V.
Заглавие : Exploration of structural, thermal and spectroscopic properties of self-activated sulfate Eu2(SO4)3 with isolated SO4 groups
Место публикации : J. Ind. Eng. Chem. - 2018. - Vol. 68. - P.109-116. - ISSN 1226086X (ISSN), DOI 10.1016/j.jiec.2018.07.034
Примечания : Cited References: 83. - This work was supported by the Russian Foundation for Basic Research ( 16-52-48010 , 17-52-53031 ). The equipments of the Collective Use Center — Kirensky Institute of Physics, Federal Research Center KSC Siberian Branch Russian Academy of Sciences [ http://ccu.kirensky.ru/ ] was used.
Ключевые слова (''Своб.индексиров.''): europium sulfate--synthesis--structure--thermal analysis--photoluminescence
Аннотация: Eu2(SO4)3 was synthesized by chemical precipitation method and the crystal structure was determined by Rietveld analysis. The compound crystallizes in monoclinic space group С2/с. In the air environment, Eu2(SO4)3 is stable up to 670 °C. The sample of Eu2(SO4)3 was examined by Raman, Fourier-transform infrared absorption and luminescence spectroscopy methods. The low site symmetry of SO4 tetrahedra results in the appearance of the IR inactive ν1 mode around 1000 cm−1 and ν2 modes below 500 cm−1. The band intensities redistribution in the luminescent spectra of Eu3+ ions is analyzed in terms of the peculiarities of its local environment.
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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shaikhutdinov K. A., Popkov S. I., Semenov S. V., Balaev D. A., Dubrovskiy A. A., Sablina K. A., Volkov N. V.
Заглавие : Low-temperature resistivity of polycrystalline (La0.5Eu 0.5)0.7Pb0.3MnO3 in a magnetic fields
Место публикации : J. Phys. Conf. Ser. - 2010. - Vol. 200, Is. SECTION 5. - ISSN 17426588 (ISSN) , DOI 10.1088/1742-6596/200/5/052025
Ключевые слова (''Своб.индексиров.''): antiferromagnetic grains--comparative analysis--ferromagnetic grain--low temperatures--polycrystalline--specific heat measurement--spin dependent tunneling--transport and magnetic properties--antiferromagnetism--electric resistance--europium--grain boundaries--grain size and shape--lanthanum compounds--lead--magnetic field effects--magnetic properties--magnetoresistance--manganese oxide--single crystals--thermal variables measurement--lanthanum
Аннотация: The effect of grain boundaries on magnetoresistance (MR) of manganites have been investigated by the comparative analysis of the properties of single-crystal and polycrystalline (La0.5Eu0.5) 0.7Pb0.3MnO3. While MR of the single crystal is maximum near the Curie temperature and vanishes in the low-temperature region, the polycrystalline (La0.5Eu0.5)0.7Pb 0.3MnO3 sample exhibits high MR in the low-temperature region. In order to clarify the origin of the low-temperature MR, the transport and magnetic properties of the polycrystalline (La0.5Eu 0.5)0.7Pb0.3MnO3 in magnetic fields have been supplemented by study of magnetic properties and specific heat measurements. The results obtained could be attributed to spin-dependent tunneling between ferromagnetic grains through insulating antiferromagnetic grain boundaries. © 2010 IOP Publishing Ltd.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kartashev A. V., Flerov I. N., Volkov N. V., Sablina K. A.
Заглавие : Heat capacity and magnetocaloric effect in manganites (La1-yEuy)(0.7)Pb0.3MnO3 (y:0.2; 0.6)
Место публикации : J. Magn. Magn. Mater. - 2010. - Vol. 322, Is. 6. - P.622-627. - MAR. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2009.10.026
Примечания : Cited Reference Count: 17. - Гранты: This work was supported by the Krasnoyarsk's regional sciences foundation and RFBR in the framework of project "Siberia''(Grant no. 09-02-98001), by Integrational project of Siberian and Far Eastern Departments of RAS(no. 101) and by Council on Grants from the President of the Russian Federation for Support of Leading Scientific Schools(Projectno. NSh-1011.2008.2). Dr Maxim S. Molokeev is acknowledged for the X-raycharacterization of the samples.Финансирующая организация: Krasnoyarsk's regional sciences foundation [09-02-98001]; Siberian and Far Eastern Departments [101]; Russian Federation [NSh-1011.2008.2]
Предметные рубрики:
Ключевые слова (''Своб.индексиров.''): manganites--magnetic phase transition--heat capacity--magnetocaloric effect--heat capacity--magnetic phase transition--magnetocaloric effect--manganites--adiabatic calorimeters--heat capacities--magnetic phase transitions--magneto-caloric effects--magnetocaloric effect--multi-element--nonmagnetics--relative cooling power--temperature range--europium--lead--manganese compounds--oxide minerals--specific heat--phase transitions
Аннотация: Heat capacity and intensive magnetocaloric effect (MCE) in manganites (La1-yEuy)(0.7)Pb0.3MnO3[y=0.2; 0.6] (LEPM) were investigated by means of adiabatic calorimeter. The heat capacity anomaly as well as the values of both the intensive (Delta T-AD) and the extensive (Delta S-MCE) MCE were found to decrease upon increased replacement of La with nonmagnetic Eu. However, because of widening of the MCE peaks, the LEPM compounds show the relative cooling power, RCP/Delta H, comparable to other solid solutions of manganites. Owing to strong effect of Eu - La substitution on the Curie temperature, LEPM might have potential as the solid state refrigerants in multi-element cooling apparatus operating in a wide temperature range. (C) 2009 Elsevier B.V. All rights reserved.
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