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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Arkhipkin V. G., Gunyakov V. A., Myslivets S. A., Zyryanov V. Ya., Shabanov V. F.
Заглавие : Angular tuning of defect modes spectrum in the one-dimensional photonic crystal with liquid-crystal layer
Место публикации : Eur. Phys. J. E. - NEW YORK: SPRINGER, 2007. - Vol. 24, Is. 3. - С. 297-302. - NOV. - ISSN 1292-8941, DOI 10.1140/epje/i2007-10239-7
Примечания : Cited Reference Count: 28
Предметные рубрики: PERIODIC STRUCTURE
REFRACTIVE-INDEX
ENHANCEMENT
LIGHT
LASER
Ключевые слова (''Своб.индексиров.''): 42.25.bs wave propagation, transmission and absorption--42.70.df liquid crystals--42.70.qs photonic bandgap materials--angles of incidence--angular tuning--defect modes--electric polarization--photonic bandgap materials--radiation losses--absorption--defects--light polarization--liquid crystals--one dimensional--phase shift--wave propagation--photonic crystals
Аннотация: A one-dimensional ZrO2/SiO2 photonic crystal with a 4-n -pentyl-4'-cyanobiphenyl (5CB) nematic defect layer was used to investigate the transmission spectra of light polarized parallel and perpendicular to the liquid-crystal director at different angles of incidence. The spectra of the photonic crystal were shown to split into four polarized components T-ij at oblique incidence. When the incident angle increased, the bandgap edges and the defect modes shifted towards short wavelengths, while the amplitudes of the defect modes increased for the transverse magnetic polarization and decreased for the transverse electric polarization. The observed discrepancy between the defect mode amplitudes in the center and near the edges of the photonic bandgap was found to be related to the radiation losses inside the defect layer of a non-ideal photonic crystal. The simulated transmission spectra obtained using recurrence relations and taking into account the decay of defect modes are in good agreement with the experimental data.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrovsky A.S., Vyunishev A.M., Zaitsev A.I., Slabko V.V.
Заглавие : Random quasi-phase-matched conversion of broadband radiation in a nonlinear photonic crystal
Место публикации : Phys. Rev. A. - 2010. - Vol. 82, Is. 5. - ISSN 1050-2947, DOI 10.1103/PhysRevA.82.055806
Примечания : Cited Reference Count: 22. - Гранты: The work was supported by the Ministry of Education and Science of the Russian Federation (Contract 16.740.11.0150), Grant of the President of the Russian Federation for the support of leading scientific schools No. SS-4645.2010.2, Grant No. RNP.2.1.1.3455, Projects 2.5.2 and 3.9.1 of PSB RAS, and Projects No. 27.1 and No. 5 of SB RAS. A. M. Vyunishev is grateful for the support from Krasnoyarsk Regional Fund of Science and Technical Activity Support.Финансирующая организация: Ministry of Education and Science of the Russian Federation [16.740.11.0150]; Russian Federation for the support of leading scientific schools [SS-4645.2010.2, RNP.2.1.1.3455]; PSB RAS [2.5.2, 3.9.1]; SB RAS [27.1, 5]; Krasnoyarsk Regional Fund of Science and Technical Activity
Ключевые слова (''Своб.индексиров.''): broad spectrum--broadband radiation--femtosecond laser pulse--fundamental wave--nonlinear generation--nonlinear photonic crystals--quasi-phase-matched--quasi-phase-matched frequency doubling--red shift--shorter wavelength--tetraborate--tuning ranges--vacuum ultraviolets--band structure--crystal structure--strontium--ultrafast lasers--ultrashort pulses--photonic crystals
Аннотация: Radiation in the range 187.5-215 nm was generated via random quasi-phase-matched frequency doubling of femtosecond laser pulses in nonlinear photonic crystals of strontium tetraborate. Abroad spectrum of fundamental radiation favors the probing of the nonlinear photonic crystal band structure. The red shift of the band structure upon the fundamental wave-vector rotation was observed. No principal limitations of the tuning range at its shorter wavelength boundary from the nonlinear photonic crystal (NPC) material are found. Calculation shows that the NPC structure enables enhancement of nonlinear generation in the vacuum ultraviolet.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Aleksandrovsky A.S., Vyunishev A.M., Zaitsev A.I., Ikonnikov A.A., Pospelov G.I., Slabko V.V.
Заглавие : Phase matched conversion of radiation in nonlinear photonic crystals of strontium tetraborate
Место публикации : Proceedings of SPIE - The International Society for Optical Engineering. - 2011. - Vol. 7993: ICONO 2010: International Conference on Coherent and Nonlinear Optics (23 August 2010 through 26 August 2010, Kazan, ) Conference code: 83828. - ISBN 0277786X (ISSN); 9780819485663 (ISBN), DOI 10.1117/12.872943
Ключевые слова (''Своб.индексиров.''): nonlinear photonic crystal--random quasi phase matching--second harmonic generation--strontium tetraborate--average power--deep uv--enhancement factor--fs pulse--monodomains--nonlinear photonic crystals--quasi-phase-matched frequency doubling--radiation source--random quasi phase matching--rotational shift--second harmonic generation--tetraborate--tuning ranges--band structure--harmonic generation--nonlinear optics--optical materials--phase matching--quantum optics--strontium--photonic crystals
Аннотация: Random quasi-phase-matched frequency doubling of fs pulses to the deep UV was obtained in 1D nonlinear photonic crystal (NPC) of strontium tetraborate. Tuning range of generated radiation is from 187.5 to 215 nm. The spectrum of generated radiation consists from series of peaks with the width of order of 1 A. These peaks are the manifestation of the NPC band structure. Using fs oscillator as the fundamental radiation source, maximum average power of generated radiation is of order 1 ?W, the enhancement factor with respect to monodomain sample being of order of several hundred. The red rotational shift of NPC band structure is experimentally demonstrated. © 2011 SPIE.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Nelson C. S., Bezmaternykh L. N., Gudim, I. A.
Заглавие : Temperature- and Field-Tuning of Magnetic Phases in Multiferroic NdFe3(BO3)4
Коллективы : Korean Physical Society, Korean Magnetics Society, International Union of Pure and Applied Physics, International conference on magnetism (19; 2012 ; Jul ; 8-13; Busan, Korea/ Bexco, Korea)
Место публикации : The 19th International Conference on Magnetism with Strongly Correlated Electron Systems: book of abstracts. - 2012. - Ст.PA02. - P.116
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Nelson C. S., Bezmaternykh L. N., Gudim, I. A.
Заглавие : Temperature- and magnetic-field-tuning of magnetic phases in multiferroic NdFe3(BO3)4
Место публикации : J. Korean Phys. Soc. - 2013. - Vol. 62, Is. 10. - P.1410-1413. - DOI 10.3938/jkps.62.1410
Ключевые слова (''Своб.индексиров.''): multiferroics--rare earth ferroborates--magnetic phase transitions--мультиферроики--редко-земельные ферробораты--магнитные фазовые переходы
Аннотация: We report the low-temperature coexistence in NdFe3(BO3)4 of an incommensurate magnetic phase with a strained commensurate magnetic phase that is primarily at the surface of the crystal Increasing the temperature or magnetic ﬁeld decreases the incommensurability and stabilizes the commensurate magnetic phase above Tic ≈ 14 K or Hic = 0.9 T. A comparison to published studies indicates the onset of longitudinal magnetostriction and electric polarization at the magnetic ﬁeldinduced transition, which may arise due to a basal plane spin-ﬂop and canting of moments along the ﬁeld direction.Мы сообщаем о сосуществовании при низкой температуры в NdFe3(BO3)4 несоразмерной магнитной фазы с напряженной соразмерной магнитной фазой, которая проявляется прежде всего вблизи поверхности кристалла. Увеличение температуры или магнитного поля уменьшает несоразмерность и стабилизирует соразмерную магнитную фазу выше Тнесоразм ≈ 14 K или Ннесоразм = 0.9 T. Сравнение с уже опубликованными данными указывает на появление продольной магнитострикции и электрической поляризации в магнитоиндуцированном переходе, который может возникнуть из-за спин-флоп перехода в базовой плоскости и скашивания моментов вдоль направления магнитного поля.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Li G., Lin C. C., Chen W.-T., Molokeev M. S., Atuchin V. V., Chiang C.-Y., Zhou W., Wang C.-W., Li W.-H., Sheu H.-S., Chan T.-S., Ma C., Liu R.-S.
Заглавие : Photoluminescence tuning via cation substitution in oxonitridosilicate phosphors: DFT calculations, different site occupations, and luminescence mechanisms
Место публикации : Chem. Mater.: American Chemical Society, 2014. - Vol. 26, Is. 9. - P.2991-3001. - ISSN 0897-4756, DOI 10.1021/cm500844v. - ISSN 1520-5002
Примечания : Cited References: 62. - The authors would like to thank the Ministry of Science and Technology of Taiwan (Contract No. MOST 101-2113-M-002-014-MY3), the National Synchrotron Radiation Research Center, Taiwan, the National Natural Science Foundation of China (Grant No. NSFC 21301162), and the Fundamental Research Funds for the Central Universities (Grant No. CUG 130402) for financially supporting this research. Victor V. Atuchin gratefully acknowledges the Ministry of Education and Science of the Russian Federation for the financial support.
Предметные рубрики: LIGHT-EMITTING-DIODES
HIGH-TEMPERATURE SYNTHESIS
LED CONVERSION PHOSPHORS
CRYSTAL X-RAY
WHITE-LIGHT
ORDERED DISTRIBUTION
GREEN PHOSPHOR
LAYERED OXONITRIDOSILICATE
REAL STRUCTURE
AB-INITIO
Аннотация: Tuning and optimizing luminescent properties of oxonitridosilicates phosphors are important for white light-emitting diode (WLED) applications. To improve the color rendering index, correlated color temperature and thermal stability of layer-structured MSi2O2N2:Eu (M = Sr, Ba) phosphors, cation substitutions have been used to adjust their luminescent properties. However, the underlying mechanisms are still unclear. In this research, a series of (Sr1-xBax)Si2O2N2:Eu (0 ≤ x ≤ 1) compounds were prepared by solid-state reaction, after which systematic emission variations were investigated. The crystal structures of (Sr1-xBax)Si2O2N2:Eu (0 ≤ x ≤ 1) are nominally divided into three sections, namely, Phase 1 (0 ≤ x ≤ 0.65), Phase 2 (0.65 x 0.80), and Phase 3 (0.80 ≤ x ≤ 1) based on the X-ray diffraction measurements. These experimental results are further confirmed by optimizing the crystal structure data with first-principle calculations. Continuous luminescence adjustments from green to yellow are observed in Phase 1 with gradual replacement of Sr2+ with Ba2+, and the abnormal redshift is clarified through extended X-ray absorption fine structure analysis. Sr(Eu)-O/N bond length shrinkage in local structure causes the redshift emission, and the corresponding luminescence mechanism is proposed. Controllable luminescence in Phase 2 (from blue to white) and Phase 3 (from cyan to yellowish green) are observed. Based on the high-resolution transmission electron microscopy and selected area electron diffraction analysis, the two kinds of luminescence tuning are attributed to phase segregation. This study serves as a guide in developing oxonitride luminescent materials with controllable optical properties based on variations in local coordination environments through cation substitutions.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Xia, Zhiguo, Ma C., Molokeev M. S., Liu Q., Rickert K., Poeppelmeier K. R.
Заглавие : Chemical unit cosubstitution and tuning of photoluminescence in the Ca2(Al1-xMgx)(Al1-xSi1+x)O7:Eu2+ phosphor
Место публикации : J. Am. Chem. Soc.: American Chemical Society, 2015. - Vol. 137, Is. 39. - P.12494-12497. - ISSN 0002-7863, DOI 10.1021/jacs.5b08315
Примечания : Cited References: 24. - This work was supported by the National Natural Science Foundations of China (Grant Nos. 51572023 and 51272242), Natural Science Foundations of Beijing (2132050), the Program for New Century Excellent Talents in University of Ministry of Education of China (NCET-12-0950), Beijing Nova Program (Z131103000413047), and the Funds of the State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, CAS (RERU2015022). C.M. acknowledges financial support from National Natural Science Foundation of China (Grant No. 11204393), Natural Science Foundation Project of Chongqing (Grant No. CSTC2014JCYJA50034), and National Training Programs of Innovation and Entrepreneurship for Undergraduates (Grant No. 201410617001). K.R. recognizes that this material is based upon work supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE-1324585.
Предметные рубрики: LUMINESCENCE PROPERTIES
TRANSITIONS
IONS
Аннотация: The union of structural and spectroscopic modeling can accelerate the discovery and improvement of phosphor materials if guided by an appropriate principle. Herein, we describe the concept of chemical unit cosubstitution as one such potential design scheme. We corroborate this strategy experimentally and computationally by applying it to the Ca2(Al1-xMgx)(Al1-xSi1+x)O7:Eu2+ solid solution phosphor. The cosubstitution is shown to be restricted to tetrahedral sites, which enables the tuning of luminescent properties. The emission peaks shift from 513 to 538 nm with a decreasing Stokes shift, which has been simulated by a crystal-field model. The correlation between the 5d crystal-field splitting of Eu2+ ions and the local geometry structure of the substituted sites is also revealed. Moreover, an energy decrease of the electron-phonon coupling effect is explained on the basis of the configurational coordinate model. © 2015 American Chemical Society.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Chen M., Xia Z., Molokeev M. S., Liu Q.
Заглавие : Insights into Ba4Si6O16 structure and photoluminescence tuning of Ba4Si6O16:Ce3+,Eu2+ phosphors
Место публикации : J. Mater. Chem. C: Royal Society of Chemistry, 2015. - Vol. 3, Is. 48. - P.12477-12483. - ISSN 20507534 (ISSN), DOI 10.1039/c5tc03271g
Примечания : Cited References: 39. - This work was supported by the National Natural Science Foundations of China (Grant No. 51572023 and 51272242), Natural Science Foundations of Beijing (2132050), the Program for New Century Excellent Talents in University of Ministry of Education of China (NCET-12-0950), Beijing Nova Program (Z131103000413047), the Funds of the State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University (KF201306), and Fundamental Research Funds for the Central Universities (FRF-TP-14-005A1).
Предметные рубрики: LIGHT-EMITTING-DIODES
ENERGY-TRANSFER
LUMINESCENCE PROPERTIES
WHITE-LIGHT
GLASS-CERAMICS
BA PHOSPHORS
EMISSION
GREEN
EU2+
FLUORESCENCE
Аннотация: The versatile polymorphism and chemical compositions of barium silicates have been studied for a long time and their crystal structures have been established. Herein, we focused on the understanding of the crystal structure of the Ba4Si6O16 phase and the structural correlation of Ba4Si6O16 and Ba2Si3O8; moreover, the luminescence properties of Ce3+,Eu2+-co-activated Ba4Si6O16 phosphors have been discussed. Ba4Si6O16:Ce3+,Eu2+ phosphors show tunable blue-green emission upon excitation with 365 nm ultraviolet (UV) light. The blue emission originates from Ce3+, whereas the bluish-green emission is ascribed to Eu2+, and variation in the emission peak wavelength from 442 to 497 nm can be achieved by properly tuning the Ce3+/Eu2+ ratio. Energy transfer from Ce3+ to Eu2+ in the Ba4Si6O16 host has been validated by the variation of emission spectra as well as the variation of Ce3+ decay lifetimes with increasing Eu2+ concentration, and the energy transfer mechanism is demonstrated to be a resonant type via a dipole-dipole process. The results suggest that Ba4Si6O16:Ce3+,Eu2+ phosphors are potential candidates as a blue-green component for UV-excited white light-emitting diodes. © 2015 The Royal Society of Chemistry.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Xia Z., Liu G., Wen J., Mei Z., Balasubramanian M., Molokeev M. S., Peng L., Gu L., Miller D. J., Liu Q., Poeppelmeier K. R.
Заглавие : Tuning of photoluminescence by cation nanosegregation in the (CaMg)x(NaSc)1-xSi2O6 solid solution
Место публикации : J. Am. Chem. Soc.: American Chemical Society, 2016. - Vol. 138, Is. 4. - P.1158-1161. - ISSN 00027863 (ISSN), DOI 10.1021/jacs.5b12788
Примечания : Cited References: 23. - Work performed by Z.X. and Q.L. was supported by the National Natural Science Foundation of China (51272242 and 51572023), the Program for New Century Excellent Talents in the University of the Ministry of Education of China (NCET-12-0950), and the Beijing Nova Program (Z131103000413047). Work performed by G.L., J.W., Z.M., M.B., and D.J.M. at Argonne National Laboratory was supported by the Office of Basic Energy Sciences of the U.S. Department of Energy (DOE) through Grant DE-AC02-06CH11357 for research on heavy elements chemistry and materials sciences. TEM was accomplished in part at the Center for Nanoscale Materials, a DOE Office of Science User Facility under Contract DE-AC02-06CH11357. Sector 20 operations at APS are supported by DOE and the Canadian Light Source, with additional support from the University of Washington. G.L. acknowledges travel support from the CAS/SAFEA International Partnership Program for Creative Research Teams. K.R.P. gratefully acknowledges support from the National Science Foundation (DMR-1307698).
Предметные рубрики: SPINODAL DECOMPOSITION
ENERGY-TRANSFER
EXSOLUTION
CLINOPYROXEN
NANOCRYSTALS
SEGREGATION
MECHANISMS
PYROXENESS
JERVISITE
PHOSPHORS
Аннотация: Controlled photoluminescence tuning is important for the optimization and modification of phosphor materials. Herein we report an isostructural solid solution of (CaMg)x(NaSc)1-xSi2O6 (0 < x < 1) in which cation nanosegregation leads to the presence of two dilute Eu2+ centers. The distinct nanodomains of isostructural (CaMg)Si2O6 and (NaSc)Si2O6 contain a proportional number of Eu2+ ions with unique, independent spectroscopic signatures. Density functional theory calculations provided a theoretical understanding of the nanosegregation and indicated that the homogeneous solid solution is energetically unstable. It is shown that nanosegregation allows predictive control of color rendering and therefore provides a new method of phosphor development. © 2016 American Chemical Society.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhang M., Xia Z., Molokeev M. S., Shi L., Liu Q.
Заглавие : New insight into the crystal structure of Sr4Ca(PO4)2SiO4 and the photoluminescence tuning of Sr4Ca(PO4)2SiO4:Ce3+,Na+,Eu2+ phosphors
Место публикации : J. Mater. Chem. C: Royal Society of Chemistry, 2016. - Vol. 4, Is. 38. - P.9078-9084. - ISSN 20507534 (ISSN), DOI 10.1039/c6tc03373c
Примечания : Cited References: 31
Ключевые слова (''Своб.индексиров.''): calcium--energy transfer--europium--light emission--light emitting diodes--luminescence--phosphate minerals--phosphors--photoluminescence--positive ions--rietveld refinement--tuning--chemical compositions--energy transfer mechanisms--green component--hexagonal cells--luminescence properties--single phase--solid state method--white lightemitting diodes (wleds)--crystal structure
Аннотация: A new single phase based on the substitution of a Sr cation by a Ca cation in the apatite-type Sr5(PO4)2(SiO4) has been fabricated with the nominal chemical composition of Sr4Ca(PO4)2(SiO4), which appears as a definite compound rather than a solid solution between (Sr,Ca)3(PO4)2 and (Sr,Ca)2SiO4. The crystal structure of Sr4Ca(PO4)2(SiO4) has been firstly analysed by the difference electron map, and further resolved by the Rietveld refinement, and the final composition has been determined as Sr4Ca(PO4)(2+x)(SiO4)(1-x)(OH)x (x = 0.64) with a hexagonal cell (P63/m). The Ce3+/Eu2+ codoped Sr4Ca(PO4)2SiO4 phosphors have been designed and prepared by the solid state method, and the photoluminescence tuning from blue to green upon 365 nm ultraviolet (UV) radiation can be realized, which is ascribed to the energy transfer from Ce3+ to Eu2+ ions. The luminescence properties and the energy transfer mechanism in Ce3+/Eu2+ codoped Sr4Ca(PO4)2SiO4 phosphors have been discussed, which might act as potential candidates for blue-green components in UV-pumped white light emitting diodes (WLEDs). © 2016 The Royal Society of Chemistry.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Wang H.-T., Wu P.-C., Timofeev I. V., Zyryanov V. Ya., Lee W.
Заглавие : Dynamic tuning and memory switching of defect modes in a hybrid photonic structure
Место публикации : Crystals. - 2016. - Vol. 6, Is. 10. - Ст.129. - ISSN 20734352 (ISSN), DOI 10.3390/cryst6100129
Примечания : Cited References: 32. - This work was financially sponsored by the Ministry of Science and Technology (MOST), Taiwan, under grant No. 103-2923-M-009-003-MY3, the Ministry of Education and Science of the Russian Federation under state order No. 3.1276.2014/K, and by the Siberian Branch of the Russian Academy of Sciences under Complex Program II.2P (projects Nos. 0358-2015-0010 and 0358-2015-0011).
Ключевые слова (''Своб.индексиров.''): dual-frequency liquid crystals--energy-efficient photonic devices--photonic crystals
Аннотация: We propose a memorable and electrically tunable photonic device by infiltrating a dual-mode chiral-doped dual-frequency liquid crystal (LC) as the central defect layer in a one-dimensional photonic crystal (PC). According to the transmission properties of this structure, the wavelength tunability of defect modes is obtained by manipulating the LC layer in the dynamic mode due to the electrically controlled birefringence effect. Moreover, the switching between two memorable states, the splay and π-twist states, creates two distinct sets of defect modes at null voltage. The spectral characteristics of this device ensure its potential application as an energy-efficient multichannel wavelength filter.
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12.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Semenov S. V., Gokhfeld D. M., Balaev D. A., Yakimov I. S., Petrov M. I.
Заглавие : Tuning the peak effect by in Y1-xNdxBa2Cu3O7-δ compound by Nd doping
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.3PO-I-19. - P.576
Примечания : Библиогр.: 4
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13.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Kuzovnikova L.A., Denisova E. A., Chekanova L. A., Nemtsev I. V., Komogortsev S. V., Iskhakov R. S.
Заглавие : Tuning local magnetic anisotropy in core-shell Co@Cu particles by dynamic compacting and the shell build-up
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-I1-8. - P.788 (Шифр 29916280)
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Sadreev A. F., Pilipchuk A. S., Lyapina A. A.
Заглавие : Tuning of Fano resonances by rotation of continuum: Wave faucet
Коллективы : RFBR [17-02-00440]
Место публикации : Europhys. Lett. - 2017. - Vol. 117, Is. 5. - Ст.50011. - ISSN 0295-5075, DOI 10.1209/0295-5075/117/50011. - ISSN 1286-4854(eISSN)
Примечания : Cited References:35. - This work has been supported by RFBR through Grant 17-02-00440. The authors thank E. N. Bulgakov and D. N. Maksimov for helpful discussions.
Предметные рубрики: BOUND-STATES
TRAPPED MODES
ACOUSTIC RESONANCES
Аннотация: We consider wave transmission in a non-axisymmetric waveguide which consists of cylindrical resonator and two semi-infinite cylindrical waveguides whose axes are shifted relative to each other by azimuthal angle Δϕ. Although rotation by Δϕ does not change the eigenfrequency spectrum of the resonator, it effectively tunes the Fano resonances and respectively gives rise to an analog of a faucet opening and closing wave flux under rotation. Moreover, under the rotation of the waveguide and variation of the length of resonator, numerous events of the Fano resonance collapse occur to argue for the bound states in the continuum. In the nearest vicinity of the bound states scattering wave function with orbital angular momentum shows phase dislocations with giant vortical acoustic flows around.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gokhfeld D. M., Balaev D. A., Yakimov I. S., Petrov M. I., Semenov S. V.
Заглавие : Tuning the peak effect in the Y1−xNdxBa2Cu3O7−δ compound
Место публикации : Ceram. Int.: Elsevier, 2017. - Vol. 43, Is. 13. - P.9985-9991. - ISSN 02728842 (ISSN), DOI 10.1016/j.ceramint.2017.05.011
Примечания : Cited References: 37. - This work was supported by the Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund to the research project no. 16-48-243018 and the Russian Foundation for Basic Research, project no. 16-38-00400.
Ключевые слова (''Своб.индексиров.''): peak effect--bulk superconductors--critical current--pinning--characterization--ybco
Аннотация: Polycrystalline Y1−xNdxBa2Cu3O7−δ (x=0.02, 0.11, and 0.25) superconductors are synthesized. Nd atoms are uniformly distributed over grains. The magnetization loops of the samples have a pronounced second peak in a wide temperature range. The magnetization data are analyzed using the extended critical state model. It is found that the order-disorder transition of the vortex lattice is affected by doping with neodymium and temperature; the second-peak field and width decrease monotonically with increasing x value. The undoped polycrystalline YBa2Cu3O7−δ compound is assumed to exhibit the peak effect in higher magnetic fields.
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16.

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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17.

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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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Xing G., Feng Y., Pan M., Wei Y., Li G., Dang P., Liang S., Molokeev M. S., Cheng Z., Lin J.
Заглавие : Photoluminescence tuning in a novel Bi3+/Mn4+ co-doped La2ATiO6:(A = Mg, Zn) double perovskite structure: Phase transition and energy transfer
Место публикации : J. Mater. Chem. C. - 2018. - Vol. 6, Is. 48. - P.13136-13147. - ISSN 20507534 (ISSN), DOI 10.1039/c8tc05171b
Примечания : Cited References: 60. - This work was supported by the National Natural Science Foundation of China (Grant No. 51672259, 51672265, 21521092, 51750110511), the Engineering Research Center of Nano-Geomaterials of Ministry of Education, China University of Geosciences (Wuhan) (No. NGM2016KF002), the Key Research Program of Frontier Sciences, CAS (Grant No. YZDYSSW-JSC018), and the projects for science and technology development plan of Jilin province (20170414003GH), the Program for Jiangmen Innovative Research Team (No. [2017]385), and the major program of basic research and applied research of Guangdong Province (2017KZDXM083).
Ключевые слова (''Своб.индексиров.''): crystal symmetry--energy transfer--light--luminescence--perovskite--phosphors--rietveld refinement
Аннотация: Red-emitting phosphors are indispensable compounds which are used to achieve a warm white light in phosphor-converted white light emitting diodes (pc-WLEDs). However, the luminous efficiency and stability of red phosphors are still big challenges. In this work, we developed red-emitting double perovskite phosphors La2ATiO6:Bi3+,Mn4+ (A = Mg, Zn) (LAT:Bi3+,Mn4+) and discuss the relationship between the double perovskite phosphor structure and the luminescence performance in detail. According to the Rietveld refinement results for the La2Mg(1−w)ZnwTiO6:Bi3+,Mn4+ (0 ≤ w ≤ 1) (LM(1−w)ZwT:Bi3+,Mn4+) solid solution, the proposed mechanism of the spectral adjustment is ascribed to the appearance of the phase transition, which results in a lower local structural symmetry of the [LaO12] polyhedron and the variation of the crystal field environment for Mn4+. Notably, this is the first time that the influence of the local structure variation on the luminescence tuning in double perovskite structure phosphors has been revealed, and this could offer guidance for the development of new phosphor system. By designing Mg2+/Zn2+ cation substitution, the internal quantum efficiency (IQE) is remarkably enhanced beyond 20%. In addition, we succeeded in achieving a Bi3+/Mn4+ co-doped energy transfer in the double perovskite structure phosphors. Owing to the Bi3+ → Mn4+ energy transfer in LAT, the red emission of the Mn4+ ions could be dramatically enhanced. The energy transfer efficiency of LAT:Bi3+,Mn4+ eventually exceeded 90%. The IQE and the thermal stability were all enhanced by around 30% compared to the non-co-doped samples, respectively. These results indicate that the Bi3+ → Mn4+ energy transfer strategy could play a pivotal role in the development of highly efficient red-emitting phosphors. The performance of the fabricated pc-WLEDs devices indicates that LAT:Bi3+,Mn4+ could be a promising red phosphor for near ultraviolet (n-UV) based warm pc-WLEDs.
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19.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Tarasov A. S., Visotin M. A., Volochaev M. N., Solovyov L. A., Aleksandrovsky A. S., Rautskii M. V., Zhandun V. S., Yakovlev I. A., Nemtsev I. V., Varnakov S. N., Ovchinnikov S. G.
Заглавие : Tuning the magnetic, transport and optical properties of FeSi2 nanocrystals
Коллективы : Asian School-Conference on Physics and Technology of Nanostructured Materials, Азиатская школа-конференция по физике и технологии наноструктурированных материалов, Институт автоматики и процессов управления ДВО РАН, Дальневосточный федеральный университет
Место публикации : Fourth Asian school-conference on physics and technology of nanostructured materials (ASCO-NANOMAT 2018): proceedings. - Vladivostok: Dalnauka, 2018. - P.143
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Liang S. S., Dang P. P., Li G. G., Molokeev M. S., Wei Y., Lian H. Z., Shang M. M., Al Kheraiff A. A., Lin J.
Заглавие : Controllable two-dimensional luminescence tuning in Eu2+,Mn2+ doped (Ca,Sr)9Sc(PO4)7 based on crystal field regulation and energy transfer
Место публикации : J. Mater. Chem. C. - 2018. - Vol. 6, Is. 25. - P.6714-6725. - ISSN 2050-7526, DOI 10.1039/c8tc01825a. - ISSN 2050-7534(eISSN)
Примечания : Cited References: 63. - This work was financially supported by the National Natural Science Foundation of China (NSFC No. 51672265, 51672266, 21521092, 51750110511, 51672257, and 51672259), the Key Research Program of Frontier Sciences of CAS (Grant No. YZDY-SSW-JSC018), the National Basic Research Program of China (2014CB643803), the Scientific and Technological Department of Jilin Province (Grant No. 20150520029JH and 20170414003GH), Jiangmen Innovative Research Team Program (2017) and Major Program of Basic Research and Applied Research of Guangdong Province (2017KZDXM083), the Russian Science Foundation (Grant No. 17-12-01047), and the Distinguished Scientist Fellowship Program of King Saud University, as well as the Deanship of Scientific Research at King Saud University through research group no. (RG-1939-038).
Предметные рубрики: SOLID-SOLUTION PHOSPHORS
LIGHT-EMITTING-DIODES
CATION SUBSTITUTION
Аннотация: Currently, controllable luminescence tuning and the generation of single component white emission are viable strategies to modify and optimize the luminescence performances of phosphors, which offer appealing prospects for the w-LED lighting industry. In this paper, we designed two-dimensional (2D) tunable color coordinates on the CIE diagram in the Eu2+,Mn2+ doped (Ca,Sr)9xSc(PO4)7 system by a combination of crystal field regulation and the energy transfer method. X-ray powder diffraction (XRD) and Rietveld refinement were utilized to analyze the phase composition and structural variation of the studied phosphors. The transmission electron microscopy (TEM) and photoluminescence spectra were exploited to analyze the generation of nanosegregation. The effects of the schedule of cation substitutions and energy transfer on the photoluminescence properties were investigated in detail. The corresponding luminescence mechanisms of the red-shifted emission with Sr2+ → Ca2+ substitution and Eu2+ → Mn2+ energy transfer were deeply discussed and proposed. In addition, the temperature-dependent thermal quenching behavior and the electroluminescence (EL) performance of the fabricated w-LED devices were also investigated to characterize the prepared Ca9(1−0.03−x−y)Sr9xSc(PO4)7:0.27Eu2+,9yMn2+. Finally, a representative w-LED device composed of a 369 nm UV chip and Ca9(1−0.03−0.02−0.5)Sr4.5Sc(PO4)7:0.27Eu2+,0.18Mn2+ could present excellent EL performance with the parameters CRI = 88, CCT = 3122 K and color coordinate (0.45, 0.44), which could well meet the commercial standard of warm white light. Therefore, our results suggest that this two-step luminescence tuning method is feasible to be applied in other phosphor systems for obtaining efficient white emitting phosphors.
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