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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Chen M., Xia Z., Molokeev M. S., Wang T., Liu Q.
Заглавие : Tuning of photoluminescence and local structures of substituted cations in xSr2Ca(PO4)2-(1 - x)Ca10Li(PO4)7:Eu2+ phosphors
Место публикации : Chem. Mater.: American Chemical Society, 2017. - Vol. 29, Is. 3. - P.1430-1438. - ISSN 08974756 (ISSN), DOI 10.1021/acs.chemmater.7b00006
Примечания : Cited References: 37. - The present work was supported by the National Natural Science Foundation of China (Grants 91622125 and 51572023), Natural Science Foundations of Beijing (2172036), and Fundamental Research Funds for the Central Universities (FRF-TP-15-003A2).
Ключевые слова (''Своб.индексиров.''): calcium--energy transfer--europium--light emission--lithium--luminescence--phosphors--photoionization--photoluminescence--single crystals--composition ranges--crystal-field splitting--luminescence measurements--non-linear variation--photoionization process--polyhedra distortion--rare earth doped solids--temperature dependent--solid solutions
Аннотация: Local structure modification in solid solution is an essential part of photoluminescence tuning of rare earth doped solid state phosphors. Herein we report a new solid solution phosphor of Eu2+-doped xSr2Ca(PO4)2-(1 - x)Ca10Li(PO4)7 (0 ≤ x ≤ 1), which share the same β-Ca3(PO4)2 type structure in the full composition range. Depending on the x parameter variation in xSr2Ca(PO4)2-(1 - x)Ca10Li(PO4)7:Eu2+, the vacancies generated in the M(4) site enable the nonlinear variation of cell parameters and volume, and this increases the magnitude of M(4)O6 polyhedra distortion. The local structure modulation around the Eu2+ ions causes different luminescent behaviors of the two-peak emission and induces the photoluminescence tuning. The shift of the emission peaks in the solid solution phosphors with different compositions has been discussed. It remains invariable at x ≤ 0.5, but the red-shift is observed at x 0.5 which is attributed to combined effect of the crystal field splitting, Stokes shift, and energy transfer between Eu2+ ions. The temperature-dependent luminescence measurements are also performed, and it is shown that the photoionization process is responsible for the quenching effect.
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Boldyrev K. N., Stanislavchuk T. N., Klimin S. A., Popova M. N., Bezmaternykh L. N.
Заглавие : Terahertz spectroscopy of multiferroic EuFe3(BO3)4
Место публикации : Phys. Lett. A: Elsevier Science BV, 2012. - Vol. 376, Is. 37. - P.2562-2564. - ISSN 0375-9601, DOI 10.1016/j.physleta.2012.06.028
Примечания : Cited References: 19. - This work was partially supported by the Russian Foundation for Basic Research under Grants No. 10-02-01071-a and No. 09-02-00171-a, by the Ministry of Education and Science under Grant HIII-4828.2012.2, and by the Russian Academy of Sciences under the programs for basic research.
Предметные рубрики: SINGLE-CRYSTAL
GDFE3(BO3)4
Ключевые слова (''Своб.индексиров.''): terahertz spectroscopy--multiferroics--europium iron borate
Аннотация: The terahertz spectra of a rare-earth iron borate with the huntite structure are obtained for the first time. We study the low-temperature (4.0–90 K) α-polarized transmittance spectra of the EuFe3(BO3)4 single crystal in the region 0.9–6.0 THz. Pronounced shifts of phonon frequencies and appearance of new phonon modes at the temperature T S = 58 K of the R 32 → P 3 1 21 structural phase transition are observed. Additional shifts of phonon frequencies occur at the temperature T N = 34 K of the magnetic ordering of the Fe subsystem, thus evidencing the spin–phonon coupling in this multiferroic material.
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3.

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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4.

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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5.

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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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Atuchin V. V., Aleksandrovsky A. S., Chimitova O. D., Gavrilova T. A., Krylov A. S., Molokeev M. S., Oreshonkov A. S., Bazarov B. G., Bazarova J. G.
Заглавие : Synthesis and spectroscopic properties of monoclinic α-Eu2(MoO4)3
Коллективы : Ministry of Education and Science of the Russian Federation
Место публикации : J. Phys. Chem. C: American Chemical Society, 2014. - Vol. 118, Is. 28. - P.15404-15411. - ISSN 1932-7447, DOI 10.1021/jp5040739
Примечания : Cited References: 63. - This study is partly supported by the Ministry of Education and Science of the Russian Federation.
Предметные рубрики: RARE-EARTH MOLYBDATES
VIBRATIONAL PROPERTIES
LUMINESCENCE PROPERTIES
CRYSTAL-STRUCTURE
PHASE-TRANSITIONS
TRIPLE MOLYBDATE
SINGLE-CRYSTAL
X-RAY
PHOSPHORS
EUROPIUM
Аннотация: The microcrystals of monoclinic europium molybdate, alpha-Eu-2(MoO4)(3), have been fabricated by solid-state synthesis at T = 753-1273 K for 300 h. The crystal structure of alpha-Eu-2(MoO4)(3) has been refined by the Rietveld method and was found to belong to the space group C2/c with unit cell parameters a = 7.5576(1), b = 11.4709(2), c = 11.5158(2) angstrom, and beta = 109.278(1)degrees (R-B = 3.39%). About 40 narrow Raman lines have been observed in the Raman spectrum of the alpha-Eu-2(MoO4)(3) powder sample. The luminescence spectra of alpha-Eu-2(MoO4)(3) under excitation at 355 and 457.9 nm reveal domination of induced electric dipole transition D-5(0) - F-7(2) and the presence of ultranarrow lines at D-5(0) - F-7(0) and D-5(1) - F-7(0) transitions.
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shaykhutdinov K. A., Balaev D. A., Semenov S. V., Popkov S. I., Dubrovskiy A. A., Sapronova N. V., Volkov N. V.
Заглавие : Relaxation of low-temperature magnetoresistance and magnetization of polycrystalline (La0.5Eu0.5)(0.7)Pb0.3MnO3
Разночтения заглавия :авие SCOPUS: Relaxation of low-temperature magnetoresistance and magnetization of polycrystalline (La 0.5Eu 0.5) 0.7Pb 0.3MnO 3
Место публикации : J. Phys. D. - 2011. - Vol. 44, Is. 25. - Ст.255001. - ISSN 0022-3727, DOI 10.1088/0022-3727/44/25/255001
Примечания : Cited References: 34. - This work was partially supported by the Lavrentyev Competition of the Young Scientist's Projects of the Siberian Branch of the Russian Academy of Sciences, Project No 12. The authors are grateful to A D Balaev and V M Sosnin for useful discussions on the results.
Предметные рубрики: INSULATOR-METAL TRANSITION
GRANULAR FILMS
NANOPARTICLES
PR0.7CA0.3MNO3
PERCOLATION
MANGANITES
Ключевые слова (''Своб.индексиров.''): antiferromagnetic boundaries--characteristic value--ferromagnetic domains--ferromagnetic metal--lanthanum manganites--logarithmic law--low temperatures--magneto-resistive effect--polycrystalline--relative orientation--relaxation of magnetization--temperature fluctuation--time evolutions--time interval--tunnel magnetoresistance--antiferromagnetism--electric resistance--europium--ferromagnetic materials--ferromagnetism--grain boundaries--grain size and shape--lanthanum compounds--lead--magnetic domains--magnetic moments--magnetoelectronics--magnetoresistance--manganese oxide--magnetization
Аннотация: Hysteresis and relaxation of magnetoresistance and magnetization of substituted (La0.5Eu0.5)(0.7)Pb0.3MnO3 lanthanum manganite in a low-temperature region ( 40 K) are investigated. It is shown that at these temperature features of the magnetoresistive effect are determined mainly by spin-dependent tunnelling of carriers via insulating grain boundaries. As was demonstrated previously, the grain boundaries may be antiferromagnetically ordered. Therefore, relaxation of magnetization and resistance is determined by the processes of relative orientation of the magnetic moments of ferromagnetic domains neighbouring the antiferromagnetic boundary of ferromagnetic domains under the action of temperature fluctuations. It is shown that relaxation follows the logarithmic law within the time interval t similar to 10(2)-3x10(3) s. A comparison between time evolutions of the magnetic moment and resistance shows that magnetoresistance and magnetization are related as delta R
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrovsky A. S., Krylov A. S., Potseluyko A. M., Seredkin V. A., Zaitsev A. I., Zamkov A. V.
Заглавие : Pulsed laser deposition of europium borate glass films and their optical and magneto-optical properties
Коллективы : International Conference on Lasers, Applications, and Technologies
Место публикации : Laser-Assisted Micro- and Nanotechnologies. Proceedings of SPIE: [11-15 May 2005]/ ed. V. I. Konov [et al.]: SPIE-Int. Soc. Optical Engineering, 2006. - P.61610A
РИНЦ
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9.

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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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrovsky A. S., Arkhipkin V. G., Bezmaternykh L. N., Gudim I. A., Krylov A. S., Vagizov F.
Заглавие : Origin of color centers in the flux-grown europium gallium garnet
Место публикации : J. Appl. Phys.: AMER INST PHYSICS, 2008. - Vol. 103, Is. 8. - Ст.83102. - ISSN 0021-8979, DOI 10.1063/1.2902365
Примечания : Cited References: 7
Предметные рубрики: SPECTRA
IONS
Ключевые слова (''Своб.индексиров.''): absorption--europium alloys--garnets--ultraviolet radiation--calcium-free flux--flux-grown europium gallium garnet--color centers
Аннотация: Europium gallium garnet (EuGG) single crystals were grown from fluxes with various contents. Optical absorption spectra of EuGG grown from a flux containing calcium show an additional band in the ultraviolet and blue regions of the spectra as compared to the case of a calcium-free flux. Mossbauer spectra of the samples grown from the fluxes with different additives show no signs of other valence states of the europium ions except for 3+. However, they indicate changes in the crystal field due to the entrance of additive ions. The nature of the additional absorption must be the same as that for calcium-doped gadolinium gallium garnet, i.e., anion vacancies. Mossbauer isotope shifts and quadrupole splitting for EuGG are determined. (C) 2008 American Institute of Physics.
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