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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Попков, Сергей Иванович, Петров, Михаил Иванович, Балаев, Дмитрий Александрович, Шайхутдинов, Кирилл Александрович
Заглавие : Сосуществование сверхпроводимости и ферримагнетизма в композитах Y1Ba2Cu3O7+7.5%Y3(Al0.6Fe0.4)5O12 (транспортные свойства)
Коллективы : "Фундаментальные проблемы высокотемпературной сверхпроводимости", международная конференция
Место публикации : Третья международная конференция "Фундаментальные проблемы высокотемпературной сверхпроводимости" ФПС'08: 13-17 окт., Звенигород, 2008 : сборник трудов. - С. 160-161
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Петров, Михаил Иванович, Попков, Сергей Иванович, Балаев, Дмитрий Александрович, Шайхутдинов, Кирилл Александрович
Заглавие : Сосуществование сверхпроводимости и ферримагнетизма в композитах Y1Ba2Cu3O7+7.5%Y3(Al0.6Fe0.4)5O12 (магнитные свойства)
Коллективы : "Фундаментальные проблемы высокотемпературной сверхпроводимости", международная конференция
Место публикации : Третья Междунар. конф. "Фундам. пробл. высокотемпер. сверхпроводимости" ФПС'08: 13-17 окт., Звенигород, 2008 : сборник трудов. - С. 158-159
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Балаев, Дмитрий Александрович, Семенов, Сергей Васильевич, Гохфельд, Денис Михайлович
Заглавие : Развитие концепции эффективного поля в межгранульной среде гранулярного высокотемпературного сверхпроводника. Различное воздействие внутригранульных токов Мейсснера и вихрей Абрикосова на магнитотранспортные свойства Y-Ba-Cu-O
Коллективы : Сибирский семинар по высокотемпературной сверхпроводимости и физике наноструктур, Институт физики им. Л.В. Киренского Сибирского отделения РАН, Сибирский федеральный университет, Федеральный исследовательский центр "Красноярский научный центр Сибирского отделения Российской академии наук", Институт неорганической химии им. А.В. Николаева Сибирского отделения РАН, Омский государственный университет им. Ф.М. Достоевского
Место публикации : XIV Cибирский семинар по высокотемпературной сверхпроводимости и физике наноструктур (ОКНО-2023): сб. тезисов докладов/ орг. ком., прогр. ком. С. Г. Овчинников [и др.]. - Красноярск, 2023. - С. 19
Примечания : Библиогр.: 2
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Chen, Yu, Yang, Zhiyu, Jin, Jiance, Qiao, Jianwei, Wang, Yuzhen, Molokeev M. S., Swart, Hendrik C., Xia, Zhiguo
Заглавие : Site occupation engineering toward giant red-shifted photoluminescence in (Ba,Sr)2LaGaO5:Eu2+ phosphors
Колич.характеристики :8 с
Место публикации : Chem. Mater. - 2023. - Vol. 35, Is. 20. - P.8714-8721. - ISSN 08974756 (ISSN), DOI 10.1021/acs.chemmater.3c01980. - ISSN 15205002 (eISSN)
Примечания : Cited References: 35. - This research was supported by the National Key Research and Development Program of China (2021YFB3500401 and 2021YFE0105700), the National Natural Science Foundations of China (Grant Nos. 51972118 and 52102169), the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program (2017BT01X137), the China Postdoctoral Science Foundation (2021M691053), and the Young Elite Scientists Sponsorship Program by China Association for Science and Technology (No. YESS20200053). This work was also supported by the Ministry of Science and Higher Education of the Russian Federation as part of World-class Research Center program: “Advanced Digital Technologies”, contract no. 075-15-2022-314
Аннотация: Exploring oxide-based red-emitting phosphors is essential for improving the color rendering index (Ra) and reducing the correlated color temperature (CCT) of white-light-emitting diode (LED) lighting sources. Especially, it is challenging to design Eu2+ red emission in inorganic solids. Here, the Eu2+-activated oxide phosphor Sr2LaGaO5:Eu2+ was synthesized with red emission peaking at 618 nm under 450 nm excitation. The crystal structure and spectral analysis indicate that Eu2+ tends to occupy [Sr1/LaO8] polyhedrons with a smaller coordination number, resulting in a large crystal field splitting at the 5d level and realizing the broadband 4f–5d red emission. When Sr is substituted by Ba atoms, density functional theory calculations verify that Ba tends to enter [Sr2O10] with a large coordination number, further giving rise to the lattice distortion and a giant spectral redshift (618–800 nm). The white LED device fabricated by mixing red Sr1.8Ba0.2GaO5:Eu2+ and green Lu3Al5O12:Ce3+ phosphors exhibits a high color rendering index (Ra = 92.1) and a low color-dependent temperature (CCT = 4570 K). This study will give guidance for exploring new Eu2+ activated oxide-based red phosphors as well as achieving tunable emission through cations’ substitution.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gao, Huabo, Molokeev M. S., Chen, Qi, Min, Xin, Ma, Bin
Заглавие : Novel AMoO4:Eu3+ (A = Ca and Ba) optical thermometer: Investigation of effect of local ionic coordination environment on optical performance and temperature measurement sensitivity
Место публикации : Ceram. Int. - 2023. - Vol. 49, Is. 16. - P.26803-26810. - ISSN 02728842 (ISSN), DOI 10.1016/j.ceramint.2023.05.217. - ISSN 18733956 (eISSN)
Примечания : Cited References: 52. - The work was supported by the program of Science and Technology International Cooperation Project of Qinghai province (No. 2022-HZ-807) and the National Natural Science Foundation of China (Grant No. 51802172), and was carried out within the framework of the Strategic Academic Leadership Program “Priority-2030′′ for the Siberian Federal University
Аннотация: A range of Eu3+-doped AMoO4 (A = Ca and Ba) phosphors were successfully synthetized, and their crystal structures, optical performance, and temperature measurement sensitivities were investigated in detail. Peak doping concentration of CaMoO4:Eu3+ phosphor was 0.18, while peak doping concentration of BaMoO4:Eu3+ phosphor may be greater than 0.18. Then, temperature-dependent photoluminescence emission spectra of representative CaMoO4:0.09Eu3+ and BaMoO4:0.03Eu3+ phosphors were recorded. CaMoO4:0.09Eu3+ phosphor exhibited abnormal thermal quenching, which was attributed to defects caused by heterovalent substitution of ions and increase in the temperature, and good thermal stability. Finally, the possibility of using both phosphors as optical thermometers was discussed, which exhibited good temperature sensitivity. However, CaMoO4:0.09Eu3+ phosphor exhibited two peak absolute (Sa, 1.28 %K−1 and 1.39 %K−1) and relative sensitivities (Sr, 1.21 %K−1 and 1.20 %K−1). In addition, variation trend of Sr value with temperature was considerably peculiar. Two optimum Sa and Sr values were attributed to abnormal thermal quenching of CaMoO4:0.09Eu3+ phosphor. Peak Sa and Sr values of BaMoO4:0.03Eu3+ phosphor was 12.39 %K−1 and 0.89 %K−1, respectively. In addition, Sa of AMoO4:Eu3+ phosphor was negatively related to Eu3+ central asymmetry, while peak Sr value was more inclined to appropriate ionic central asymmetry.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Semenov S. V., Gokhfeld D. M.
Заглавие : Developing a concept of an effective field in the intergrain medium of a granular superconductor: Effect of the intragrain Meissner currents and Abrikosov vortices trapped in grains on the magnetotransport properties of a Y-Ba-Cu-O granular HTS
Колич.характеристики :18 с
Место публикации : J. Supercond. Nov. Magn. - 2023. - Vol. 36, Is. 7-9. - P.1631-1648. - ISSN 15571939 (ISSN), DOI 10.1007/s10948-023-06608-2. - ISSN 15571947 (eISSN)
Примечания : Cited References: 58. - The authors are grateful to M.I. Petrov, A.D. Balaev, and V.M. Sosnin for fruitful discussions and A.V. Shabanov and I.V. Nemtsev for scanning electron microscopy investigations. The scanning electron microscopy investigations and a part of magnetic measurements (performed on a LakeShore VSM 8604 facility) were carried out at the Krasnoyarsk Regional Center for Collective Use, Krasnoyarsk Scientific Center, Siberian Branch of the Russian Academy of Sciences. The study is performed within the state assignment of Kirensky Institute of Physics
Аннотация: Granular high-temperature superconductors (HTSs) are characterized by the hysteretic field dependences of magnetoresistance R(H) and critical current IC(H). These hysteretic effects are described within the concept of an effective field in the intergrain medium. The effective field is a superposition of external magnetic field H and the field induced by the magnetic moments of superconducting grains into intergrain spacings (grain boundaries). The magnetization of superconducting grains is determined by two contributions: Meissner (shielding) currents (MC) and trapped magnetic fluxes (Abrikosov vortices (AV)). To develop the concept of an effective field in the intergrain medium, the magnetotransport properties (R and IC) have been compared for two cases: (AV) the magnetization of superconducting grains is only determined by the trapped magnetic flux (zero external field) and (MC) HTS grains are in the Meissner state (the external field is weaker than the first critical field of grains). In a set of experiments, the main features of the hysteretic R(H) and M(H) dependences have been illustrated and the external conditions for implementing the AV and MC states have been established. It has been found that the effects of the Abrikosov vortices and intragrain Meissner currents on an effective field in the intergrain medium at the same magnetization values are noticeably different. This is a nontrivial fact that requires a thorough study of the impact of the anisotropy of the superconducting properties of grains on the configuration of the Meissner currents in them, as well as on the orientation of vortices both inside grains and near their surface. We suggest the explanation of observed stronger effect of the Meissner currents on the intergrain medium as compared with the effect of the Abrikosov vortices.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Yang, Zhiyu, Zhao, Yifei, Zhou, Yayun, Qiao, Jianwei, Chuang, Yu-Chun, Molokeev M. S., Xia, Zhiguo
Заглавие : Giant red-shifted emission in (Sr,Ba)Y2O4:Eu2+ phosphor toward broadband near-infrared luminescence
Коллективы : International Cooperation Project of National Key Research and Development Program of China [2021YFE0105700]; National Natural Science Foundations of ChinaNational Natural Science Foundation of China (NSFC) [51972118, 51961145101]; Guangzhou Science & Technology Project [202007020005]; Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program [2017BT01X137]; RFBRRussian Foundation for Basic Research (RFBR) [19-52-80003]
Место публикации : Adv. Funct. Mater. - 2022. - Vol. 32, Is. 1. - Ст.2103927. - ISSN 1616-301X, DOI 10.1002/adfm.202103927. - ISSN 1616-3028(eISSN)
Примечания : Cited References: 60. - This research was supported by the International Cooperation Project of National Key Research and Development Program of China (2021YFE0105700), National Natural Science Foundations of China (Grant No. 51972118 and 51961145101), Guangzhou Science & Technology Project (202007020005), and the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program (2017BT01X137). This work is also funded by RFBR according to the research project No. 19-52-80003
Предметные рубрики: LIGHT-SOURCES
PHOTOLUMINESCENCE
TRANSITION
CE3+
BLUE
SUBSTITUTION
Аннотация: Near-infrared (NIR) light-emitting diodes (LEDs) light sources are desirable in photonic, optoelectronic, and biological applications. However, developing broadband red and NIR-emitting phosphors with good thermal stability is always a challenge. Herein, the synthesis of Eu2+-activated SrY2O4 red phosphor with high photoluminescence quantum efficiency and broad emission band ranging from 540 to 770 nm and peaking at 620 nm under 450 nm excitation is designed. Sr/Ba substitution in SrY2O4:Eu2+ has been further utilized to achieve tunable emission by modifying the local environment, which facilitates the giant red-shifted emission from 620 to 773 nm while maintaining the outstanding thermal stability of SrY2O4:Eu2+. The NIR emission is attributed to the enhanced Stokes shift and crystal field strength originated from the local structural distortions of [Y1/Eu1O6] and [Y2/Eu2O6]. The investigation in charge distribution around Y/Eu provides additional insight into increasing covalency to tune the emission toward the NIR region. As-fabricated NIR phosphor-converted LEDs demonstration shows its potential in night-vision technologies. This study reveals the NIR luminescence mechanism of Eu2+ in oxide-based hosts and provides a design principle for exploiting Eu2+-doped NIR phosphors with good thermal stability.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zinenko V. I., Shinkorenko A. S.
Заглавие : Lattice dynamics and phase transitions in a crystal Ba2ZnTeO6
Место публикации : Phys. Solid State. - 2022. - Vol. 64, Is. 12. - P.1986-1992. - ISSN 10637834 (ISSN), DOI 10.21883/PSS.2022.12.54395.445. - ISSN 10906460 (eISSN)
Примечания : Cited References: 12. - The calculations were performed using the computer resources ”Integrated simulation and processing of data of mega-class scientific research units” of National Research Centre” Kurchatov Institute“ (http://ckp.urcki.ru)
Аннотация: The lattice dynamics of Ba2ZnTeO6 double perovskite in three phases has been studied. Vibrational spectra and dynamic charges are calculated. In the rhomobohedral phase R3¯m, soft modes were found; after their condensation, the C2/m phase was obtained, which agrees with the experiment. An assessment was made of the dependence of the enthalpy of different phases on pressure; it showed that the monoclinic phase is more favorable at 0 pressure, but as the pressure increases to 2.9 GPa, the cubic phase Fm3¯m becomes advantageous.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Зиненко, Виктор Иванович, Шинкоренко, Алексей Сергеевич
Заглавие : Динамика решетки и фазовые переходы в кристалле Ba2ZnTeO6
Место публикации : Физ. тверд. тела. - 2022. - Т. 64, Вып. 12. - С. 2021-2027. - ISSN 03673294, DOI 10.21883/FTT.2022.12.53656.445
Примечания : Библиогр.: 12. - Расчеты выполнены с использованием компьютерных ресурсов ”Комплексное моделирование и обработка данных научно-исследовательских установок мега-класса ”НИЦ ”Курчатовский институт“ (http://ckp.urcki.ru)
Аннотация: Выполнены исследования динамики решетки двойного перовскита Ba2ZnTeO6 в трех фазах. Вычислены колебательные спектры, динамические заряды. В ромобоэдрической фазе R3¯m были обнаружены мягкие моды, после их конденсации была получена фаза C2/m, что согласуется с экспериментом. Была проведена оценка зависимости энтальпии разных фаз от давления, она показала, что моноклинная фаза более выгодна при 0 давлении, но при увеличении давления до 2.9 GPa, становится выгодна кубическая фаза Fm3¯m.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Yang, Zhiyu, Zhou, Yayun, Qiao, Jianwei, Molokeev M. S., Xia, Zhiguo
Заглавие : Rapid synthesis of red-emitting Sr2Sc0.5Ga1.5O5:Eu2+ phosphors and the tunable photoluminescence via Sr/Ba substitution
Место публикации : Adv. Opt. Mater. - 2021. - Vol. 9. Is. 16. - Ст.2100131. - ISSN 2195-1071, DOI 10.1002/adom.202100131
Примечания : Cited References: 44. - Z.Y. and Y.Z. contributed equally to this work. This research was supported by the National Natural Science Foundations of China (Grant Nos. 51972118 and 51961145101), International Cooperation Project of National Key Research and Development Program of China (No. 2021YFE0105700), Guangzhou Science & Technology Project (No. 202007020005), and the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program (No. 2017BT01x137). This work was also funded by RFBR according to the research Project No. 19-52-80003
Предметные рубрики: LUMINESCENCE PROPERTIES
THERMAL-STABILITY
EU2+
GREEN
EU3+
SR
Аннотация: Discovering new Eu2+-doped red-emitting phosphors in oxide-based materials is a challenge for white light-emitting diode (WLED) applications. Herein, a highly efficient high-frequency induction heating method is employed to rapidly prepare the red-emitting Sr2Sc0.5Ga1.5O5:Eu2+ phosphors peaking at 614 nm and exhibiting a high photoluminescence quantum yield of 78.4% under the excitation of 440 nm. The structural and spectral analyses suggest that Eu2+ ions tend to enter the [Sc1/Ga1O6] and [Ga2O6] polyhedrons with small coordination numbers, leading to the broadband red emission originated from large crystal field splitting of Eu2+ 5d level. The chemical substitution of Ba in the Sr site enhances the thermal stability and helps to the photoluminescence tuning from 614 to 728 nm in SrBaSc0.5Ga1.5O5:Eu2+. The WLED device fabricated by blending the red Sr1.7Ba0.3Sc0.5Ga1.5O5:Eu2+ and yellow Y3(Al, Ga)5O12:Ce3+ phosphors shows a high color-rendering index (Ra = 91.1), and low color-correlated temperature (CCT = 4750 K). This study aims to provide a new synthesis method and design principle for guiding the development of Eu2+-doped oxide-based red phosphors with low preparation cost; moreover, the photoluminescence tuning strategy via cation substitutions is essential to achieve tunable emission, even the near-infrared luminescence.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Lai S., Hu T., Molokeev M. S., Xia Z.
Заглавие : Photoluminescence tuning in Ba3ScB3O9:Eu2+ phosphor by crystal-site engineering
Место публикации : Phys. Open. - 2021. - Vol. 8. - Ст.100077. - ISSN 26660326 (ISSN), DOI 10.1016/j.physo.2021.100077
Примечания : Cited References: 31. - The present work was supported by the National Natural Science Foundation of China (Grant Nos. 51972118 and 51961145101), International Cooperation Project of National Key Research and Development Program of China (2021YFE0105700), the Guangzhou Science & Technology Project (202007020005), and the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program (2017BT01X137). This work is also funded by RFBR according to the research project No. 19-52-80003
Аннотация: Controlled photoluminescence tuning is essential for optimizing and accelerating the application of phosphor materials. Here, we adopt the crystal-site engineering method to tailor the photoluminescence properties in Ba3ScB3O9:Eu2+. Ba3ScB3O9 host contains multiple cationic sites which help to finely regulate Eu2+ site occupancies and thus the emission color. The relationship between Eu2+ emission and the local environments has been analyzed, and we demonstrate that the emission colors of the phosphors can be widely tuned from NIR to yellow by chemically driving the Eu2+ from octahedrally-coordinated Sc3+ sites to nine-fold coordinated Ba2+ sites. Our study will initiate and guide more explorations on discovering new phosphors through crystal-site engineering.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Semenov S. V., Balaev D. A., Petrov M. I.
Заглавие : Universal behavior and temperature evolution of the magnetoresistance hysteresis in granular high-temperature superconductors Y-Ba-Cu-O
Место публикации : Phys. Solid State. - 2021. - Vol. 63, Is. 7. - P.1069-1080. - ISSN 1063-7834, DOI 10.1134/S1063783421070192. - ISSN 1090-6460(eISSN)
Примечания : Cited References: 80. - The authors are grateful to D.M. Gokhfeld for discussion of the results. The measurements of the transport properties were performed in part on a PPMS-6000 system of the Center for Collective Use, Krasnoyarsk Scientific Center, Siberian Branch of the Russian Academy of Sciences
Предметные рубрики: CRITICAL-CURRENT-DENSITY
CURRENT-VOLTAGE CHARACTERISTICS
MAGNETIC-FLUX COMPRESSION
Аннотация: Regularities in the behavior of the magnetoresistance hysteresis R(H) in the granular yttrium high-temperature superconductors (HTSs) have been established. For this purpose, a comparative analysis of the magnetotransport properties has been carried out on the granular HTS samples, which exhibit (i) approximately the same magnetic properties and temperatures of the onset of the superconducting transition (90.5–93.5 K, which is characteristic of HTS grains) and (ii) different critical transport currents JC (which is characteristic of grain boundaries). Despite a significant (by more than an order of magnitude) spread of the JC values for the three samples, a universal behavior of the magnetoresistance hysteresis has been found, which is apparently inherent in all the granular Y–Ba–Cu–O compounds. The R(H) hysteresis is extremely broad and, in a fairly wide external field range, the dependence of the magnetoresistance hysteresis width ΔН on the field Hdec (the external field for the decreasing hysteresis branch is Н = Hdec) is almost linear: ΔH ≈ Hdec. This behavior is observed over the entire temperature range of implementation of the superconducting state (the investigations have been carried out at temperatures of 77–88 and 4.2 K). The result obtained has been explained by considering the effective field in grain boundaries, which is a superposition of the external field and the field induced by the magnetic moments of grains. The field induced by grains, in turn, significantly increases in the region of grain boundaries due to the magnetic flux compression (the grain boundary length is shorter than the HTS grain size by several orders of magnitude). The aforesaid has been confirmed by the analysis of the R(H) hysteresis for the Y–Ba–Cu–O- and CuO-based HTS composite, in which the grain boundary length is purposefully increased; as a result, the flux compression is less pronounced and the R(H) hysteresis narrows.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Семенов, Сергей Васильевич, Балаев, Дмитрий Александрович, Петров, Михаил Иванович
Заглавие : Универсальность поведения гистерезиса магнитосопротивления и его температурной эволюции для гранулярных высокотемпературных сверхпроводников Y-Ba-Cu-O
Место публикации : Физ. тверд. тела. - 2021. - Т. 63, Вып. 7. - С. 854-865. - ISSN 0367-3294, DOI 10.21883/FTT.2021.07.51034.055
Примечания : Библиогр.: 80
Аннотация: Посвящена установлению закономерности в поведении гистерезиса магнитосопротивления R(H) гранулярных высокотемпературных сверхпроводников (ВТСП) иттриевой системы. Для этого проведено сравнительное исследование магнитотранспортных свойств образцов гранулярных ВТСП, обладающих (i) примерно одинаковыми магнитными свойствами и температурами начала сверхпроводящего перехода (90.5-93.5 K, что характеризует ВТСП гранулы) и (ii) различной величиной транспортного критического тока JC (что характеризует межгранульные границы). Несмотря на значительный разброс в величинах JC (более чем на порядок) исследованных трех образцов, обнаружено универсальное поведение гистерезиса магнитосопротивления, видимо, присущее всем гранулярным Y-Ba-Cu-O. Гистерезис R(H) очень широкий, и в достаточно большом интервале внешнего поля зависимость ширины гистерезиса магнитосопротивления Δ H от поля Hdec (внешнее поле H=Hdec для убывающей ветки гистерезиса) близка к линейной функции: Δ H≈Hdec. Это поведение наблюдается для всей температурной области реализации сверхпроводящего состояния (исследования проведены при температурах 77-88 и 4.2 K). Объяснение полученному результату основывается на концепции рассмотрения эффективного поля в межгранульных границах, которое является суперпозицией внешнего поля и поля, индуцированного магнитными моментами гранул. Индуцированное гранулами поле, в свою очередь, значительно усиливается в области межгранульных границ, благодаря эффекту сжатия магнитного потока (протяженность межгранульных границ на несколько порядков меньше размера ВТСП гранул). Вышесказанное подтверждается анализом гистерезиса R(H) для композитного ВТСП на основе Y-Ba-Cu-O и CuO, в котором протяженность межгранульных границ целенаправленно увеличена, как следствие, влияние эффекта сжатия потока проявляется меньше, а гистерезис R(H) сужается.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shtarev D. S., Shtareva, A., V, Kevorkyants R., Rudakova, A., V, Molokeev M. S., Bakiev, T., V, Bulanin K. M., Ryabchuk V. K., Serpone N.
Заглавие : Materials synthesis, characterization and DFT calculations of the visible-light-active perovskite-like barium bismuthate Ba1.264(4)Bi1.971(4)O4 photocatalyst
Коллективы : Russian Science FoundationRussian Science Foundation (RSF) [19-73-10013]; Saint-Petersburg State University [39054581]; Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR) [18-03-00855]
Место публикации : J. Mater. Chem. C. - 2020. - Vol. 8, Is. 10. - P.3509-3519. - ISSN 2050-7526, DOI 10.1039/c9tc06457e. - ISSN 2050-7534(eISSN)
Примечания : Cited References: 42. - The current research was kindly funded by a grant from the Russian Science Foundation (project No. 19-73-10013). R. K., A. V. R., V. K. R. and T. V. B. acknowledge financial support from Saint-Petersburg State University (Pure ID 39054581). A. V. R. thanks the Russian Foundation for Basic Research for a Grant No. 18-03-00855 that supported studies into the photoinduced hydrophilicity of the bismuthate. The authors are further grateful to the staff of the Khabarovsk Innovation and Analytical Center of the Yu. A. Kosygin Institute of Tectonics and Geophysics of the Far Eastern Branch of the Russian Academy of Sciences, and the Resource Centers of the Research Park at the Saint-Petersburg State University: (i) the Center for Diagnostics of Functional Materials for Medicine, Pharmacology and Nanoelectronics, (ii) the Center for Physical Methods of Surface Investigation, (iii) the Center for Optical and Laser Materials Research, and the laboratories of (iv) Nanotechnology and (v) Nanophotonics for their valuable assistance in carrying out the research and in providing the needed equipment. One of us (N.S.) is grateful to Prof. Angelo Albini and the staff of the PhotoGreen Laboratory at the University of Pavia, Italy, for their continued hospitality.
Предметные рубрики: OXIDE
NIO/SRBI2O4
SPECTRA
DRIVEN
CO2
LA
Аннотация: A perovskite-like barium bismuthate of the BaBi2O4 class, Ba1.264(4)Bi1.971(4)O4, has been prepared by solid-state synthesis and subsequently characterized by a number of experimental techniques (XPS, DRS, SEM, EDX and Raman spectroscopy), as well as by a DFT computational approach using the GGA Perdew–Burke–Ernzerhof (PBE) density functional to determine the energy band structure. XRD peaks were indexed to a rhombohedral cell (R[3 with combining macron]m) with parameters close to Ba0.156Bi0.844O1.422 (i.e., to Ba0.439Bi2.374O4), which upon Rietveld refinement gave Ba1.264(4)Bi1.971(4)O4. The Bi–O bond lengths determined from this refinement (1.86 and 2.31 Å) accorded with the bond lengths estimated from Raman spectra (1.97 and 2.26 Å). DFT calculations revealed the bismuthate to display two bandgaps that correspond to lower-energy indirect (2.28 eV) and to higher-energy direct (2.36 eV) electronic transitions in good agreement with the experimental bandgaps of 2.26 eV and 2.43 eV, respectively, from Tauc plots of DRS spectra. Relative to the indirect bandgap energy of 2.26 eV, the energies of the valence band and of the conduction band were, respectively, +1.14 eV and −1.12 eV. The photoactivity of Ba1.264(4)Bi1.971(4)O4 was examined toward the photoreduction of the greenhouse gas CO2 in aqueous media photoelectrochemically yielding alcohols and alkanes, while in the gas phase in an infrared cell reactor the products were carbon monoxide and alkanes.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Hao J., Tao M., Gao Z., Chen S., Liu Y., Wang H., Wei Y., Molokeev M. S., Li G.
Заглавие : Enhanced green emission and thermal stability of Ba3Si6O12N2:Eu2+ by Ce3+/P5+-doping: Unity energy transfer, charge compensation and lattice strain release
Место публикации : J. Lumines. - 2020. - Vol. 220. - Ст.116995. - ISSN 00222313 (ISSN), DOI 10.1016/j.jlumin.2019.116995
Примечания : Cited References: 66. - This work is financially supported by the National Natural Science Foundation of China (NSFC No. 51672259 , 51601131 ) and the Fundamental Research Fund for National Universities , China University of Geosciences (Wuhan)
Аннотация: To optimize luminescence properties of oxonitridosilicate phosphors are extremely necessary for improving lighting quality of white light-emitting diodes (WLEDs). Herein, we designed Ce3+, Eu2+ codoping and P5+-Si4+ substitution in the presentative Ba3Si6O12N2:Eu2+ green phosphor to realize an enhancement of luminescence efficiency and thermal stability. Rietveld refinement results of Ce3+, Eu2+, P5+-doped Ba3Si6O12N2 (BSON) confirmed the formation of pure trigonal phase (P-3) of Ba3Si6O12N2 and the successful doping of Ce3+, Eu2+, P5+ ions. Ce3+ and Eu2+ ions randomly occupy two Ba crystallographic sites. Interestingly, a near unity energy transfer (ET, ~100%) from Ce3+ ions to Eu2+ ions is observed. Meanwhile, the doping of P5+ ions into BSON also helps improving the luminescence efficiency and thermal stability, which should be attributed to the charge compensation and the relax of lattice strain. In addition, the white light emitting diodes (WLEDs) fabricated by employing P5+-doped BSON: Eu2+ present a better electroluminescence performance than BSON: Eu2+. This study could serve as a guide in developing optimized oxonitridosilicates phosphors with improved luminescence performances based on complete energy transfer and lattice variations in local coordination environments through cation substitutions, and the as-prepared Ce3+/P5+-codoped Ba3Si6O12N2:Eu2+ could be an excellent green-emitting phosphor for UV-to-Visible LED chips pumped WLEDs.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhang, Guangqing, Molokeev M. S., Ma, Qianchao, Yang, Xuening, Han, Shuiquan, Chen, Q.i., Zhong, Binnian, Ma, Bin
Заглавие : Structural analysis and optical temperature sensing performance of Eu3+-doped Ba3In(PO4)3
Место публикации : CrystEngComm. - 2020. - Vol. 22, Is. 35. - P.5809-5817. - ISSN 1466-8033, DOI 10.1039/d0ce00997k
Примечания : Cited References: 52. - This work was supported by the National Natural Science Foundation of China (Grant No. 51802172) and the Qinghai Provincial Natural Science Foundation for Young Scholars (No. 2018-ZJ-957Q)
Предметные рубрики: FLUORESCENCE INTENSITY RATIO
UP-CONVERSION EMISSIONS
RARE-EARTH IONS
Аннотация: Eu3+-Doped Ba3In(PO4)3 was synthesized through a high-temperature solid-phase method. According to the structure refinement based on X-ray diffraction and density functional theory, the crystal and energy band structures of Ba3In(1−x)(PO4)3:xEu3+ were studied and analyzed in detail. The effect of Eu3+ doping concentrations on emission was studied at an excitation wavelength of 393 nm. For the material Ba3In(1−x)(PO4)3:xEu3+(x = 0.01–0.30), the optimal doping level is confirmed to be 0.18. Due to the thermal quenching differences of Eu3+ at the 5D0 and 5D1 energy levels, and based on the temperature-variable fluorescence intensity ratio between emission peaks, the optical temperature measurement performance of this material in the temperature range from 298.15 K to 623.15 K was characterized, and the maximum absolute and relative sensor sensitivities (Sa and Sr) were determined to be 0.1002 K−1 and 4.058%, respectively. With temperature as the only variable, the color of the phosphor changes from red to yellow light with rising temperature. Besides, Sa and Sr values of this phosphor are comparable to other sensing materials. The results indicate that Eu3+-doped Ba3In(PO4)3 phosphors have great potential to be applied in optical temperature sensing.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Xiang J., Zheng J., Zhou Z., Suo H., Zhao X., Zhou X., Zhang N., Molokeev M. S., Guo C.
Заглавие : Enhancement of red emission and site analysis in Eu2+ doped new-type structure Ba3CaK(PO4)3 for plant growth white LEDs
Место публикации : Chem. Eng. J. - 2019. - Vol. 356. - P.236-244. - ISSN 13858947 (ISSN) , DOI 10.1016/j.cej.2018.09.036
Примечания : Cited References: 42. - This work was supported by National Natural Science Foundation of China (No. 11704312 , 51672215 , 11274251 ), Research Fund for the Doctoral Program of Higher Education of China (RFDP) (No. 20136101110017) and by RFBR (17-52-53031).
Ключевые слова (''Своб.индексиров.''): phosphor--ba3cak(po4)3--sites-dependent photoluminescence--plant growth--white leds
Аннотация: A novel compound Ba3CaK(PO4)3 (BCKP) with new-type structure was synthesized and its structure was determined by X-ray diffraction Rietveld refinement, in which crystal structure consists of Ba1O9, Ba2O12, Ba3O9, CaO8 and KO10 polyhedra, that's five cationic sites. As a phosphor host, Eu2+ doped BCKP emits cold white light with about 90% quantum efficiency (QE) through entering different cationic sites. Based on the results of refinement, three Eu2+ luminescence centers in sites Ca, Ba2 and K were clearly assigned in Eu2+ solely doped BCKP by the time-resolved emission spectra (TRES), Van Uitert equation, but the emissions of Eu2+ at Ba1 and Ba3 sites are not easy to be determined for the same coordination number (CN). According to their different spatial distribution of the coordinated atoms, the first-principles calculation was used to compute the d orbital splitting energy of Eu2+ ions in Ba1 and Ba3 sites to accurately distinguish the ambiguous luminescence centers. In order to meet the requirement of plant growth spectra, Mn2+ was introduced into BCKP: Eu2+ to enhance the red component of spectra, which not only perfectly match with the absorption spectra of carotenoid and chlorophyll-b, but also LEDs fabricated through combining 365 nm near ultraviolet (n-UV) chip with BCKP: Eu2+, Mn2+ phosphor exhibit excellent parameters including high color rendering index (Ra) (92), excellent correlated color temperature (CCT) (4486 K) and outstanding QE up to 65%. Results confirmed that BCKP: Eu2+/Mn2+ phosphor with great potential applications in white LEDs and plant growth.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Коржнева, Ксения Евгеньевна, Исаенко Л. И., Елисеев, Александр Павлович, Молокеев, Максим Сергеевич
Заглавие : Экспериментальное исследование процессов кристаллизации K2Ba(NO3)4 из раствор-расплава
Место публикации : Фундамент. пробл. совр. материаловед. - 2018. - Т. 15, № 1. - С. 11-15. - ISSN 1811-1416, DOI 10.25712/ASTU.1811-1416.2018.01.001
Примечания : Библиогр.: 7. - Работа выполнена в рамках государственного задания, проект № 0330 - 2016 - 0008 и при поддержке Российского фонда фундаментальных исследований (грант № 18-32-00359).
Ключевые слова (''Своб.индексиров.''): рост из раствор-расплава--двойные соединения--нецентросимметричные кристаллы k2ba(no3)4--рентгенофазовый и термический анализы--оптическое пропускание--growth from solution-melt--double compounds--noncentrosymmetrical crystals k2ba(no3)4--x-ray diffraction and thermal analysis--optical transmittance
Аннотация: С развитием технологий неуклонно возрастает потребность в высокоэффективных функциональных материалах. Поэтому все более важной и актуальной становится задача разработки принципов и алгоритмов поиска этих материалов. В настоящее время системы двойных нитратов привлекают внимание исследователей тем, что в этой группе существуют двойные соединения с нецентросимметричной структурой, которые рассматриваются как перспективные нелинейные материалы для коротковолнового диапазона. В результате проведенных ранее исследований из водных растворов были получены кристаллы K2Ba(NO3)4. Было выявлено, что K2Ba(NO3)4 при температуре 197,3 оС разлагается на KNO3 и Ba(NO3)2. Из-за большого количества дефектов (дендриты, зарастание основными гранями роста) оптическое качество этих кристаллов оказалось невысоким. Что обусловило необходимость поиска новых методик выращивания, обеспечивающих получение качественных оптически прозрачных кристаллов. Поэтому нами исследовались процессы кристаллизации K2Ba(NO3)4 из раствор-расплава. Подобран растворитель состава LiNO3-CsNO3-KNO3 с температурой эвтектик ниже температуры разложения двойного соединения. Выращены прозрачные кристаллы K2Ba(NO3)4 размером до 0,7 мм, определена их структура, показано отсутствие у них центра симметрии. На данных кристаллах были сняты спектры оптического пропускания. Исследование двух спектров данного соединения выращенного разными методами показало, что кристаллы, полученные из водных растворов, прозрачен от 0,25 мкм до 2,2 мкм, при этом наблюдается пик поглощения с максимум 0,3 мкм. Кристаллы, выращенные методом из раствор-расплава, прозрачны от 0,3 мкм до 2,2 мкм. Ширина запрещенной зоны составляет около 5 эВ.With the development of technology, the need for highly efficient functional materials is steadily increasing. Therefore, the developing of principles and algorithms for these materials' search becomes more and more important and actual. Currently systems of double nitrates attract researchers attention due to the double compounds with a noncentrosymmetric structure which are considered as promising nonlinear materials for the short-wave range. As a result of previous studies K2Ba(NO3)4 crystals were obtained from aqueous solutions. It was found that K2Ba(NO3)4 decomposes on KNO3 and Ba(NO3)2 at the temperature of 197.3 oC. Due to the large amount of defects (dendrites, overgrowing by the main growth facets), the optical quality of these crystals was not high. This necessitated the search for new growth techniques that provide the production of high-quality optically transparent crystals. Therefore, we investigated the processes of crystallization of K2Ba(NO3)4 from a solution-melt. A solvent of the LiNO3-CsNO3-KNO3 composition with a eutectic temperature below the decomposition temperature of the double compound was chosen. Transparent crystals of K2Ba(NO3)4 up to 0.7 mm in size were grown, their structure was determined, and the absence of center of symmetry was shown. The optical transmission spectra were investigated on these crystals. The study of two spectra of this compound grown by different methods showed that crystals obtained from aqueous solutions are transparent from 0.25 μm to 2.2 μm, with an absorption peak with a maximum of 0.3 μm. Crystals grown by the solution-melt method are transparent from 0.3 μm to 2.2 μm. The width of the band gap is about 5 eV.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhou Z., Zhang N., Chen J., Zhou X., Molokeev M. S., Guo C.
Заглавие : The Vis-NIR multicolor emitting phosphor Ba4Gd3Na3(PO4)6F2: Eu2+, Pr3+ for LED towards plant growth
Место публикации : J. Ind. Eng. Chem. - 2018. - Vol. 65. - P.411-417. - ISSN 1226086X (ISSN), DOI 10.1016/j.jiec.2018.05.014
Примечания : Cited References: 36. - This work was supported by National Natural Science Foundation of China (No. 11704312, 11274251), Research Fund for the Doctoral Program of Higher Education of China (RFDP) (No.20136101110017), Foundation of Key Laboratory of Photoelectric Technology in Shaanxi Province (15JS101).
Ключевые слова (''Своб.индексиров.''): phosphor--plant growth--leds--energy transfer
Аннотация: Photosynthesis process is the basic for plant growth, which needs energy from the light. The pigments of chlorophyll a, b and bacteriochlorophyll are responsible for the absorption of light, in which blue, red and near-infrared (NIR) light directly or indirectly promote the plant growth and enhancement of nurtiments. It is important for plant to support absorbable light, and phosphhor-converted light emitting diodes (pc-LEDs) are low-cost, energy-saving and enviromental friendly devices for plant growth. To develop a phosphor with emission covering the blue, red and NIR, a series of phosphors Ba4Gd3Na3(PO4)6F2: Eu2+, Pr3+ with blue, red and NIR multi-emitting were prepared. Their emissions not only match well with the absorption spectra of pigments in the plant, but also could be excited by near ultraviolet (n-UV) LED chip. The crystal structure of host Ba4Gd3Na3(PO4)6F2 was refined from the XRD data and three different crystallographic sites occupied by Eu2+ were determined through low temperature photoluminescence spectra. The energy transfer from Eu2+ to Pr3+ ions was also discussed in detail. Results indicated that the multi-emitting Ba4Gd3Na3(PO4)6F2: Eu2+, Pr3+ can serve as a phosphor candidate for plant growth LEDs.
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20.

Вид документа : Статья из журнала
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Автор(ы) : Balaev D. A., Semenov S. V., Pochekutov M. A.
Заглавие : Anisotropy of the magnetoresistance hysteresis in the granular superconductor Y-Ba-Cu-O at different magnetic-field and transport-current orientations
Место публикации : J. Appl. Phys.: American Institute of Physics, 2017. - Vol. 122, Is. 12. - Ст.123902. - ISSN 00218979 (ISSN), DOI 10.1063/1.4986253
Примечания : Cited References: 45. - This study was supported by the Russian Foundation for Basic Research, Government of the Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund to the research project No. 16-48-243018.
Ключевые слова (''Своб.индексиров.''): anisotropy--high temperature superconductors--hysteresis--magnetic fields--magnetic flux--magnetism--magnetoresistance--different-magnetic fields--external magnetic field--granular superconductors--macroscopic transport--magnetic flux compression--magneto transport properties--model representation--transport currents--superconducting materials
Аннотация: Dissipation in granular high-temperature superconductors (HTSs) during the passage of macroscopic transport current j is mainly determined by carrier tunneling through intergrain boundaries (Josephson junctions). In the presence of external magnetic field H, it is necessary to take into account the significant magnetic flux compression, which can lead to the situation when the effective field Beff in the intergrain boundaries exceeds the external field by an order of magnitude. This is observed as a wide hysteresis of the field dependence of magnetoresistance R(H). In this study, we investigate the R(H) hysteresis evolution in granular 1-2-3 HTSs in different j-H orientations. The magnetic flux compression significantly affects the magnetoresistance and its hysteresis for both perpendicular (H ⊥ j) and parallel (H ∥ j) orientations. The obtained experimental data on the R(H) hysteresis at the arbitrary angles θ = ∠H, j are explained using the approach developed for describing the magnetoresistance hysteresis in granular HTSs with regard to the magnetic flux compression and the model representations proposed by Daghero et al. [Phys. Rev. B 66(13), 11478 (2002)]. A concept of the effective field in the intergrain medium explains the well-known anisotropy of the magnetotransport properties of granular HTSs.
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