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Каталог книг и брошюр библиотеки ИФ СО РАН

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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Guan M., Molokeev M. S., Zhou J.
Заглавие : Atomic deciphering of cation exchange mechanism in upconversion nanoparticles
Место публикации : J. Lumin. - 2020. - Vol. 224. - Ст.117289. - ISSN 00222313 (ISSN), DOI 10.1016/j.jlumin.2020.117289
Примечания : Cited References: 36. - The authors acknowledge the Science and Technology Innovation Committee of Shenzhen (Grant No. KQTD20170810110913065), Australian Research Council (ARC) Discovery Early Career Researcher Award Scheme (J. Z., DE 180100669), and the China Scholarship Council (Ming Guan, No. 201506400025)
Аннотация: Transition metal ion doping in upconversion nanoparticles (UCNPs) provides an effective way to enhance the luminescence for their wide array of applications. However, the doping sites of transition metal ions have not been comprehensively explored, and commonly assumed that transition metal ions replace the trivalent lanthanides within the lattice. Here we report that cation exchange of transition metal (Mn2+) in β-NaYF4:Yb3+/Er3+ UCNPs occurs through alkaline metal (Na+) replacement, via 2Na+ ↔ Mn2+ + Vacancy reaction. This process distorts the LnF9 polyhedrons and tailors the surrounding environment around the trivalent lanthanides, thereby improving the upconversion intensity from active lanthanides. Further confirmed by core-shell design and spectroscopic study, we prove that the transition–alkaline metal exchange enables both the emission enhancement and transition probability variation of activators.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Molokeev M. S., Vasiliev A. D., Kocharova A. G.
Заглавие : Crystal structures of room- and low-temperature phases in oxyfluoride (NH4)(2)KWO3F3
Место публикации : Powder Diffr. - 2007. - Vol. 22, Is. 3. - P.227-230. - ISSN 0885-7156, DOI 10.1154/1.2759491
Примечания : Cited References: 8. - Cover image: Artwork representing main idea of this article
Ключевые слова (''Своб.индексиров.''): structure determination--rietveld analysis--powder diffraction--phase transition--oxyfluoride
Аннотация: Crystal structures of (NH4)2KWO(3)F(3) at 298 K and 113 K were solved from X-ray powder diffraction data and refined by the Rietveld technique. The compound is isostructural with elpasolite K2NaAlF6 at room temperature with space group Fm-3m, a=8.95850(5) angstrom, V=718.961(7) angstrom(3), Z =4, D-x=3.363 g/cm(3), and M-W=364.02. The structure was refined over 18 parameters to R-wp =12.6%, R-p=10.9%, R-exp=5.03%, and R-B=3.27% from 40 independent reflections. (NH4)2KWO(3)F(3) was transformed upon cooling to a ferroelastic monoclinic phase with space group P2(1)/n, a'=6.3072(3) angstrom, b'=6.3028(3) angstrom, c'=8.9882(3) angstrom, beta'=90.242(2)degrees, V=357.30(3) angstrom(3), Z =2, and D-x=3.383 g/cm(3). The low-temperature structure at 113 K was refined over 28 parameters,P to R-wp=20.9%, R-p=21.3%, R-exp= 12.5%, and R-B=6.93% from 453 independent reflections. (C) 2007 International Centre for Diffraction Data.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Qiao J., Amachraa M., Molokeev M. S., Chuang Y. -C., Ong S. P., Zhang Q., Xia Z.
Заглавие : Engineering of K3YSi2O7 to Tune Photoluminescence with Selected Activators and Site Occupancy
Место публикации : Chem. Mater. - 2019. - Vol. 31, Is. 18. - P.7770-7778. - ISSN 08974756 (ISSN), DOI 10.1021/acs.chemmater.9b02990
Примечания : Cited References: 48. - This work was supported by the National Natural Science Foundation of China (Nos. 51722202, 51972118 and 51572023), Natural Science Foundations of Beijing (2172036), Fundamental Research Funds for the Central Universities (FRF-TP-18-002C1), and Guangdong Provincial Science & Technology Project (2018A050506004). This work was also supported by the National Science Foundation, Ceramics Program (No. 1911372), and the computational resources were provided by the Extreme Science and Engineering Discovery Environment (XSEDE) supported by the National Science Foundation (No. ACI-1548562).
Аннотация: The luminescence of rare earth ions (Eu2+, Ce3+, and Eu3+)-doped inorganic solids is attractive for the screening of phosphors applied in solid-state lighting and displays and significant to probe the occupied crystallographic sites in the lattice also offering new routes to photoluminescence tuning. Here, we report on the discovery of the Eu- and Ce-activated K3YSi2O7 phosphors. K3YSi2O7:Eu is effectively excited by 450 nm InGaN blue light-emitting diodes (LEDs) and displays an orange-red emission originated from characteristic transitions of both Eu2+ and Eu3+, while K3YSi2O7:Ce3+ shows green emission upon 394 nm near-ultraviolet (NUV) light excitation. Rietveld refinement verifies the successful doping of the activators, and density functional theory (DFT) calculations further support that Eu2+ occupies both K1 and Y2 crystallographic sites, while Ce3+ and Eu3+ only occupy the Y2 site; hence, the broad-band red emission of Eu2+ are attributed to a small DFT band gap (3.69 eV) of K3YSi2O7 host and a selective occupancy of Eu2+ in a highly distorted K1 site and a high crystal field splitting around Y2 sites. The white LEDs device utilizing orange-red-emitting K3YSi2O7:Eu and green-emitting K3YSi2O7:Ce3+ exhibits an excellent CRI of 90.1 at a correlated color temperature of 4523 K. Our work aims at bridging multivalent Eu2+/Eu3+ and Ce3+ site occupancy in the same host to realize photoluminescence tuning and especially exposes new ways to explore new phosphors with multicolor emission pumped by blue and NUV light for white LEDs.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Atuchin V. V., Subanakov A. K., Aleksandrovsky A. S., Bazarov B. G., Bazarova J. G., Dorzhieva S. G., Gavrilova T. A., Krylov A. S., Molokeev M. S., Oreshonkov A. S., Pugachev A. M., Tushinova Y. L., Yelisseyev A. P.
Заглавие : Exploration of structural, thermal, vibrational and spectroscopic properties of new noncentrosymmetric double borate Rb3NdB6O12
Место публикации : Adv. Powder Technol.: Elsevier, 2017. - Vol. 28, Is. 5. - P.1309-1315. - ISSN 09218831 (ISSN), DOI 10.1016/j.apt.2017.02.019
Примечания : Cited References: 42. - We are grateful to Guochun Zhang for the crystal structure data on K3YB6O12, and O. Tsydenova and A. Sarapulova for her consultations. This research was supported by SB RAS Program No.II.2P (No. 0356-2015-0412) and RSF (14-22-0143). The reported study was funded by RFBR according to the research projects 15-02-04950 and 15-52-53080, 16-32-00351, 16-52-48010 and 17-52-53031. Also, the work was supported by Act 211 Government of the Russian Federation, contract 02.A03.21.0011 and by the Ministry of Education and Science of the Russian Federation (4.1346.2017/PP).
Ключевые слова (''Своб.индексиров.''): rubidium neodymium borate--solid state reaction--rietveld refinement--dsc--raman scattering
Аннотация: New noncentrosymmetric rare earth borate Rb3NdB6O12 is found in the ternary system Rb2O–Nd2O3–B2O3. The Rb3NdB6O12 powder was fabricated by solid state synthesis at 1050 K for 72 h and the crystal structure was obtained by the Rietveld method. Rb3NdB6O12 crystallized in space group R32 with unit cell parameters a = 13.5236(4), c = 31.162(1) Å, Z = 3. From DSC measurements, the reversible phase transition (I type) in Rb3NdB6O12 is observed at 852–936 K. The 200 μm thick tablet is transparent over the spectral range of 0.3–6.5 μm and the band gap is found as Eg ∼ 6.29 eV. Nonlinear optical response of Rb3NdB6O12 tested via SHG is estimated to be higher than that of K3YB6O12. Blue shift of Nd luminescent lines is found in comparison with other borates. The vibrational parameters of Rb3NdB6O12 are evaluated by experimental methods.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Atuchin V. V., Aleksandrovsky A. S., Bazarov B. G., Bazarova J. G., Chimitova, Olga D., Denisenko, Yuriy G., Gavrilova T. A., Krylov A. S., Maximovskiy, Eugene A., Molokeev M. S., Oreshonkov A. S., Pugachev, Alexey M., Surovtsev, Nikolay V.
Заглавие : Exploration of structural, vibrational and spectroscopic properties of self-activated orthorhombic double molybdate RbEu(MoO4)2 with isolated MoO4 units
Коллективы : RFBR [16-52-48010, 17-52-53031, 18-03-00557]; Ministry of Science and Higher Education of the Russian Federation [0339-2016-0007]; Act 211 Government of the Russian Federation [02.A03.21.0011]; Ministry of Education and Science of the Russian Federation [4.1346.2017/4.6]
Место публикации : J. Alloy. Compd. - 2019. - Vol. 785. - P.692-697. - ISSN 0925-8388, DOI 10.1016/j.jallcom.2019.01.013. - ISSN 1873-4669(eISSN)
Примечания : Cited References: 42. - The reported study was funded by RFBR according to research projects 16-52-48010, 17-52-53031 and 18-03-00557. Besides, this study was supported by the Ministry of Science and Higher Education of the Russian Federation (project 0339-2016-0007). The work was supported by Act 211 Government of the Russian Federation, contract No 02.A03.21.0011. Additionally, the work was partially supported by the Ministry of Education and Science of the Russian Federation (4.1346.2017/4.6).
Предметные рубрики: MORPHOLOGY-CONTROLLED SYNTHESIS
LUMINESCENCE PROPERTIES
Ключевые слова (''Своб.индексиров.''): rubidium europium molybdate--solid state reaction--rietveld refinement--dsc--raman luminescence
Аннотация: RbEu(MoO4)2 is synthesized by the two-step solid state reaction method. The crystal structure of RbEu(MoO4)2 is defined by Rietveld analysis in space group Pbcn with cell parameters a = 5.13502(5), b = 18.8581(2) and c = 8.12849(7) Å, V = 787.13(1) Å3, Z = 4 (RB = 0.86%). This molybdate possesses its phase transition at 817 K and melts at 1250 K. The Raman spectra were measured with the excitation at λ = 1064 and 514.5 nm. The photoluminescence spectrum is evaluated under the excitation at 514.5 nm. The absolute domination of hypersensitive 5D0→7F2 transition is observed. The ultranarrow 5D0→7F0 transition in RbEu(MoO4)2 is positioned at 580.2 nm being 0.2 nm blue shifted, with respect to that in Eu2(MoO4)3.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Thakur, Atul, Verma, Ritesh, Wan, Fayu, Ravelo, Fayu, Edelman I. S., Ovchinnikov S. G., Thakur, Preeti
Заглавие : Investigation of structural, elastic and magnetic properties of Cu2+ ions substituted cobalt nano ferrites
Место публикации : J. Magn. Magn. Mater. - 2023. - Vol. 581. - Ст.170980. - ISSN 03048853 (ISSN), DOI 10.1016/j.jmmm.2023.170980. - ISSN 18734766 (eISSN)
Примечания : Cited References: 47. - This research work was supported by the National Key Research and Development Program of China (2022YFE010707). The author(s) would like to acknowledge the support provided under the DST-FIST Grant No. SR/FST/PS-I/2018/48 of Govt. of India. PT is thankful to DST-SERB TARE fellowship vide Sanction Order No TAR/2022/000414
Аннотация: In the present work, we synthesized the Cu-doped CoFe2O4 (Co1-xCuxFe2O4) nanoparticles with x = 0.0, 0.2, 0.4 and 0.6, by employing the citrate precursor method. The X-ray Diffraction (XRD) pattern confirmed the pure cubic structure formation with the Fd-3m space group. To know the structural purity of each sample as well as the distribution of cations, Rietveld refinement was carried out. The crystallite size increases from 39.55 nm to 41.80 nm upto x = 0.2 and with further doping of Cu2+ ions it decreases to 36.27 nm. Similar variation is observed in the lattice parameter where the value of ‘a’ first increases from 8.378 Å to 8.381 Å and then decreases to 8.377 Å. The development of a non-uniform grain is seen using scanning electron microscope (SEM), which reveals the reduction in grain size. Fourier Transform Infrared Spectroscopy (FTIR) showed the two peaks ν1 and ν2 for all the samples around 541 cm−1 and 408 cm−1, respectively, which further decreases to 532.5 cm−1 and 402.5 cm−1 as the dopant ion concentration increases. The Stiffness constant, and Elastic modulus decrease with doping whereas, the Poisson’s ratio and Pugh’s ratio show a constant value of around 0.249 and 1.660, respectively. Vibrating Sample Magnetometer (VSM) analysis shows a decrease in saturation magnetization (σs) value from 76.85 emu/g to 43.62 emu/g. The net magnetic moment (nB) decreases from 3.29 μB to 1.85 μB and the effective anisotropy constant value decreases from 10.672erg/g to 4.461erg/g. Thus, the prepared nanoparticles provide a way forward for their industrial applications.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Atuchin V. V., Gavrilova T. A., Kesler V. G., Molokeev M. S., Aleksandrov K. S.
Заглавие : Low-temperature synthesis and structural properties of ferroelectric K 3WO3F3 elpasolite
Место публикации : Chem. Phys. Lett. - 2010. - Vol. 493, Is. 1-3. - P.83-86. - ISSN 0009-2614, DOI 10.1016/j.cplett.2010.05.023
Примечания : Cited References: 37
Предметные рубрики: PEROVSKITE-LIKE OXYFLUORIDES
CORE-LEVEL SPECTROSCOPY
PHASE-TRANSITIONS
SOLID-STATE
ELECTRON-DIFFRACTION
DIFFUSE-SCATTERING
RHEED ANALYSIS
POLAR
BEHAVIOR
(NH4)(3)TIOF5
Ключевые слова (''Своб.индексиров.''): chemical synthesis--elpasolite--ferroelectric phase transition--fluorine atoms--low temperature synthesis--low temperatures--oxyfluorides--partial ordering--room temperature--sem--space groups--structure parameter--xrd--chemical properties--ferroelectric materials--ferroelectricity--fluorine--oxygen--phase transitions--rietveld method--single crystals--synthesis (chemical)--x ray photoelectron spectroscopy--x ray powder diffraction--scanning electron microscopy
Аннотация: Low-temperature ferroelectric G2 polymorph of K3WO 3F3 has been prepared by chemical synthesis. Structural and chemical properties of the final product have been evaluated with X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Structure parameters of G2-K 3WO3F3 are refined by the Rietveld method from XRD data measured at room temperature (space group Cm, Z = 2, a = 8.7350(3), b = 8.6808(5), c = 6.1581(3), ? = 135.124(3), V = 329.46(3) 3; RB = 2.47%). Partial ordering of oxygen and fluorine atoms has been found over anion positions. Mechanism of ferroelectric phase transition in A2BMO3F3 oxyfluorides is discussed. В© 2010 Elsevier B.V. All rights reserved.
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Вид документа : Статья из журнала
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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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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pustovarov V. A., Ogorodnikov I. N., Omelkov S. I., Molokeev M. S., Kozlov A. V., Isaenko L. I.
Заглавие : Photoluminescence of monoclinic Li3AlF6 crystals under vacuum ultraviolet and soft X-ray excitations
Место публикации : Opt. Mater.: Elsevier, 2015. - Vol. 49. - P.201-207. - ISSN 0925-3467, DOI 10.1016/j.optmat.2015.09.011
Примечания : Cited References: 49. - This work was partly supported by the Ministry of Education and Science of the Russian Federation (the basic part of the government mandate); Center of Excellence "Radiation and Nuclear Technologies" (Competitiveness Enhancement Program of Ural Federal University, Russia), HASYLAB DESY (Projects Nos. 20110843, 20080119EC), European Social Fund ("Mobilitas" program, MJD219), Estonian Research Council (Institutional Research Funding IUT02-26) and Baltic Science Link project coordinated by the Swedish Research Council, VR
Предметные рубрики: LiBaAlF6 single-crystals
F-type centers
LiBaF3 crystals
Color-centers
Recombination luminescence
Rietveld refinement
VUV spectroscopy
Trapped excitons
Energy-transfer
Pure
Ключевые слова (''Своб.индексиров.''): li3alf6--time-resolved luminescence--vuv spectroscopy--defects
Аннотация: Using Bridgman technique we have grown monoclinic β-LiAF crystals suitable for optical studies, performed XRD-identification and Rietveld refinement of the crystal structure and carried out a photoluminescence study upon vacuum ultraviolet (VUV) and extreme ultraviolet (XUV)-excitations, using the low-temperature (T = 7.2 K) time-resolved VUV-spectroscopy technique. The intrinsic PL emission band at 340–350 nm has been identified as due to radiative recombination of self-trapped excitons. The electronic structure parameters were determined: bandgap E g ≈ 12.5 eV, energy threshold for creation of unrelaxed excitons 11.8 eV < E n < 12.5 eV . The PL emission bands at 320–325 and 450 nm were attributed to luminescence caused by lattice defects. We have discovered an efficient excitation of PL emission bands in the energy range of interband transitions ( E ex > 13.5 eV), as well as in the energy range of core transitions at 130 eV. We have revealed UV–VUV PL emission bands at 170 and 208 nm due to defects. A reasonable assumptions about the origin of the UV–VUV bands were discussed.
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10.

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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