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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhu J., Xia, Zhiguo, Zhang Y., Molokeev M. S., Liu Q.
Заглавие : Structural phase transitions and photoluminescence properties of Eu3+ doped Ca(2-x)BaxLaNbO6 phosphors
Место публикации : Dalton Trans.: Royal Society of Chemistry, 2015. - Vol. 44, Is. 42. - P.18536-18543. - ISSN 1477-9226, DOI 10.1039/c5dt03430b
Примечания : Cited References: 27. - The present work was supported by the National Natural Science Foundation of China (Grant No. 51272027, 51472028 and 51272242), Natural Science Foundations of Beijing (2132050), the Program for New Century Excellent Talents in the University of the Ministry of Education of China (NCET-12-0950), Beijing Nova Program (Z131103000413047), Beijing Youth Excellent Talent Program (YETP0635), and the Funds of the State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University (KF201306)
Предметные рубрики: Double-perovskite
Luminescence properties
Thermal-stability
Crystal-chemistry
Red phosphors
White LEDs
Symmetry
Band
Ta
Ln
Аннотация: Crystal structures of the series of double perovskites Ca(2-x)BaxLaNbO6:Eu3+ phosphors have been examined by powder X-ray diffraction and Rietveld refinements. Ca2LaNbO6 has a monoclinic (P21/n) and Ba2LaNbO6 has a monoclinic (C2/m) structure. The structural phases of Ca(2-x)BaxLaNbO6:Eu3+ samples are divided into three sections depending on different Ca/Ba ratios: (1) monoclinic phase (P21/n) as Ca2LaNbO6 in the range of x = 0-0.1, (2) mixed phases containing Ca2LaNbO6 and Ba2LaNbO6 between 0.15 and 1.2, and (3) monoclinic phase (C2/m) as Ba2LaNbO6 for x = 1.4-2. Eu3+ ions act as the structural probes to study the structural phase transitions, and the evolution of the photoluminescence properties and thermal stability behaviours has been also comparatively investigated depending on different structural symmetries from Ca2LaNbO6 to Ba2LaNbO6 phase. The strong red emission from 5D0-7F2 peaking at 618 nm can be found in Ca2LaNbO6:Eu3+ phosphors, which is attributed to the low crystal field effect of the activator ions located in the highly distorted [Lao8] polyhedra sites. The composition-optimized phosphors can find applications in white light emitting diodes (LEDs).
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Liu H., Liao L., Molokeev M. S., Guo Q., Zhang Y., Mei L.
Заглавие : A novel single-phase white light emitting phosphor Ca9La(PO4)5(SiO4)F2:Dy3+: Synthesis, crystal structure and luminescence properties
Место публикации : RSC Adv.: Royal Society of Chemistry, 2016. - Vol. 6, Is. 29. - P.24577-24583. - ISSN 20462069 (ISSN), DOI 10.1039/c5ra23348h
Примечания : Cited References: 33. - We gratefully acknowledge the financial support by the National Natural Science Foundations of China (Grant no. 41172053), the Fundamental Research Funds for the Central Universities (Grant no. 2652013043), and Science and Technology Innovation Fund of the China University of Geosciences (Beijing).
Предметные рубрики: Energy-transfer
Diodes
LEDs
Emission
Ions
Excitation
Ce3+
Eu2+
Ln
Аннотация: A novel single-phase white light emitting phosphor Ca9La(PO4)5(SiO4)F2:Dy3+ was prepared through traditional high-temperature solid state technology. The crystal structures of Ca9La(PO4)5(SiO4)F2 with or without Dy3+ ions were refined by the Rietveld method. The diffuse reflection spectra, excitation spectra, emission spectra, and decay times were characterized to investigate the photoluminescence properties for application in white light-emitting diodes. The results showed that the Ca9La(PO4)5(SiO4)F2:Dy3+ phosphor could efficiently assimilate n-UV light and emit blue (∼485 nm) and yellow light (∼580 nm), originating from the f-f transitions of Dy3+. The critical Dy3+ quenching concentration (QC) was determined to be about 15 mol%, and the corresponding QC mechanism was verified to be the dipole-dipole interaction. Additionally, the emission colors of all samples were located close to the ideal white light region, and the optimal chromaticity coordinates and correlated color temperature (CCT) were determined to be (x = 0.338, y = 0.336) and 5262 K. All the above results indicate that the as-prepared Ca9La(PO4)5(SiO4)F2:Dy3+ phosphor could serve as a promising candidate for white-light n-UV-LEDs. © The Royal Society of Chemistry 2016.
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Wang X., Li J. -G., Molokeev M. S., Zhu Q., Li X., Sun X.
Заглавие : Layered hydroxyl sulfate: Controlled crystallization, structure analysis, and green derivation of multi-color luminescent (La,RE)2O2SO4 and (La,RE)2O2S phosphors (RE = Pr, Sm, Eu, Tb, and Dy)
Место публикации : Chem. Eng. J.: Elsevier, 2016. - Vol. 302. - P.577-586. - ISSN 13858947 (ISSN), DOI 10.1016/j.cej.2016.05.089
Примечания : Cited References: 50. - This work is supported in part by the National Natural Science Foundation of China (Grants Nos. 51172038, 51302032, and U1302272), the Fundamental Research Fund for the Central Universities (Grant No. N140204002), Grants-in-Aid for Scientific Research (KAKENHI No. 26420686), and the Russian Foundation for Basic Research (15-52-53080). X.J. Wang acknowledges financial support from the China Scholarship Council for her overseas Ph.D. study (Contract No. 201406080035) and the assistance of Q. Q. Zhu (University of Science and Technology of China) for his help with calcination.
Предметные рубрики: PHOTOLUMINESCENCE PROPERTIES
OXYSULFATE/OXYSULFIDE SYSTEMS
CRYSTAL-STRUCTURE
OXYGEN-STORAGE
Ln
NANOCOMPOSITES
EMISSION
CAPACITY
FAMILY
FABRICATION
Ключевые слова (''Своб.индексиров.''): sulfate type layered rare earth hydroxide--luminescence--oxysulfate--oxysulfide
Аннотация: The two important groups of Ln2O2SO4 and Ln2O2S compounds are traditionally synthesized with the involvements of environmentally harmful sulfur-containing reagents. We developed in this work a unique green approach for their synthesis, using Ln2(OH)4SO4·2H2O layered hydroxyl sulfate as the precursor (Ln-241 phase). Phase selective crystallization of La-241 under both atmospheric pressure and hydrothermal conditions was firstly optimized, followed by transformation into La2O2S and La2O2SO4 by controlled calcination. Rietveld structure refinement was performed for La-241, La(OH)SO4, La2O2SO4, and La2O2S, and the crystal structure and cell parameters of La-241 were originally reported. The photoluminescence performances of several important activators (Pr3+, Sm3+, Eu3+, Tb3+, and Dy3+) in the two hosts, in terms of excitation, emission, quantum yield, and color coordinates of emission, were thoroughly investigated, and multi-color luminescence including bright red, green, orange red, and yellow was obtained under ultraviolet excitation. Detailed investigations of Tb3+ photoluminescence revealed that the lack of 5D3 emission in La2O2S and the gradual quenching of 5D3 blue emission at a higher Tb3+ content (hence decreasing I488/I545 ratio and changing color coordinates) in La2O2SO4 were suggested to be due to thermal activation of the 5D3 electrons into the conduction band and cross relaxation between adjacent Tb3+, respectively. The synthesis approach developed in this work for La2O2SO4 and La2O2S, with water vapor as the only exhaust gas, is environmentally benign and holds great potential in the facile synthesis of analogous compounds of other lanthanides. © 2016 Elsevier B.V.
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Vereshchagin S. N., Dudnikov V. A., Shishkina N. N., Solovyov L. A.
Заглавие : Phase transformation behavior of Sr0.8Gd0.2CoO3-delta perovskite in the vicinity of order-disorder transition
Коллективы : Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund [16-43-240505 p_a, 16-02-00507A]
Место публикации : Thermochim. Acta: Elsevier Science, 2017. - Vol. 655. - P.34-41. - ISSN 0040-6031, DOI 10.10164/j.tca.2017.06.003. - ISSN 1872-762X(eISSN)
Примечания : Cited References:40. - The reported study was funded by Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund to the research project #16-43-240505 p_a and #16-02-00507A.
Предметные рубрики: OXYGEN SORPTION
OXIDES
PERFORMANCE
DIFFUSE
LN
Ключевые слова (''Своб.индексиров.''): perovskite--ruddlesden-popper phase--order-disorder--phase transition--dsc
Аннотация: The phase transformation behavior of a single-phase tetragonal Sr0.8Gd0.2CoO3-δ (with ordered distribution of Sr2+/Gd3+ cations and anion vacancies) was investigated by TG–DSC and XRD at 1100–1473 K and oxygen partial pressure p(O2) from 1 to 5·104 Pa. The first-order smeared order-disorder (o-d) phase transition involving heat absorption was observed at about 1383 K under O2-Ar flow with p(O2) 2.5 kPa. The crystal structure of the high-temperature phase was found to be cubic perovskite with disordered Sr2+/Gd3+ cations and anion vacancies. The temperature of o-d transition at p(O2) 2.5 kPa was not influenced by the heating rate or oxygen partial pressure. It was shown that at p(O2) 2.5 kPa the o-d transition gives rise to Sr0.8Gd0.2CoO3−δ decomposition to form CoO and Sr2.4Gd0.6Co2O7-δ − Ruddlesden-Popper type phase with novel composition. The phase boundaries between the ordered tetragonal Sr0.8Gd0.2CoO3−δ, disordered cubic Sr0.8Gd0.2CoO3−δ and CoO + Sr2.4Gd0.6Co2O7-δ composite as a function of temperature and p(O2) values were determined.
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Denisenko, Yu. G., Sal'nikova E. I., Basova S. A., Molokeev M. S., Krylov A. S., Aleksandrovsky A. S., Oreshonkov A. S., Atuchin V. V., Volkova S. S., Khritokhin N. A., Andreev O. V.
Заглавие : Synthesis of samarium oxysulfate Sm2O2SO4 in the high-temperature oxidation reaction and its structural, thermal and luminescent properties
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR) [18-02-00754, 18-32-20011]; Russian Science FoundationRussian Science Foundation (RSF) [19-42-02003]
Место публикации : Molecules. - 2020. - Vol. 25, Is. 6. - Ст.1330. - ISSN 1420-3049(eISSN), DOI 10.3390/molecules25061330
Примечания : Cited References: 56. - This research was funded by the Russian Foundation for Basic Research (Grants 18-02-00754, 18-32-20011) and Russian Science Foundation (project 19-42-02003).
Предметные рубрики: RARE-EARTH SULFATES
SPECTROSCOPIC PROPERTIES
OXYGEN-STORAGE
LN
LA
Аннотация: The oxidation process of samariumoxysulfide was studied in the temperature range of 500–1000 °C. Our DTA investigation allowed for establishing the main thermodynamic (∆Hºexp = −654.6 kJ/mol) and kinetic characteristics of the process (Ea = 244 kJ/mol, A = 2 × 1010). The enthalpy value of samarium oxysulfate (ΔHºf (Sm2O2SO4(monocl)) = −2294.0 kJ/mol) formation was calculated. The calculated process enthalpy value coincides with the value determined in the experiment. It was established that samarium oxysulfate crystallizes in the monoclinic symmetry class and its crystal structure belongs to space group C2/c with unit cell parameters a = 13.7442 (2), b = 4.20178 (4) and c = 8.16711 (8)Å, β = 107.224 (1)°, V = 450.498 (9)Å3, Z = 4. The main elements of the crystalline structure are obtained and the cation coordination environment is analyzed in detail. Vibrational spectroscopy methods confirmed the structural model adequacy. The Sm2O2SO4 luminescence spectra exhibit three main bands easily assignable to the transitions from 4G5/2 state to 6H5/2, 6H7/2, and 6H9/2 multiplets.
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kazak N. V., Ovchinnikov S. G., Balaev A. D., Ivanova N.B., Pashkevich, Yu. G., Michel C.R., Bondarenko G. V.
Заглавие : Magnetic and transport properties of Gd(0.9)A(0.1)CoO(3-delta) (A = Ba, Sr)
Место публикации : J. Magn. Magn. Mater. - 2009. - Vol. 321, Is. 9. - P.1266-1271. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2008.11.087
Примечания : Cited Reference Count: 31. - Гранты: This study was supported by the Rosnauka (Project no. MK-4278.2008.2), Russian Foundation for Basic Research (Project no. 08-02-90708 mob_st) and "Strongly correlated electrons'' program of the Department of Physical Sciences of RAS.Финансирующая организация: Rosnauka [MK-4278.2008.2]; Russian Foundation for Basic Research [08-02-90708 mob_st]; "Strongly correlated electrons'' program of the Department of Physical Sciences of RAS
Предметные рубрики: PEROVSKITE
PR
LA
EU
ND
LN
TRANSITION
SPIN
GD
SM
Ключевые слова (''Своб.индексиров.''): perovskite structure--doped cobaltite--magnetic susceptibility--metal-insulator transition--doped cobaltite--magnetic susceptibility--metal-insulator transition--perovskite structure--antiferromagnetism--barium--cobalt compounds--electric conductivity--ferromagnetic materials--ferromagnetism--gadolinium--magnetic susceptibility--metal insulator boundaries--oxide minerals--paramagnetic materials--perovskite--phase separation--semiconductor insulator boundaries--transport properties--antiferromagnetic--doped cobaltite--doped samples--electrical conductivity measurements--ferromagnetic transitions--insulator-metal transitions--magnetic and transport properties--magnetic behaviors--perovskite structure--temperature ranges--transport datum--x- ray diffractions--metal insulator transition
Аннотация: The X-ray diffraction, magnetization and electrical conductivity measurements for Gd(0.9)A(0.1)CoO(3-delta) (A = Ba, Sr) have been made. The complicated magnetic behavior, including the paramagnetic-ferromagnetic-antiferromagnetic and paramagnetic-ferromagnetic transitions, was found for Ba- and Sr-doped samples. The gradual insulator-metal transitions were observed in a wide temperature range T = 600-800 K. The complex magnetic and transport data could be explained on the basis of the structural phase separation. (C) 2009 Elsevier B.V. All rights reserved.
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