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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) : Belskaya N. A., Khrapova E. K., Ivanova A. A., Eremin E. V., Pavlov S. I., Krasilin A. A.
Заглавие : Structure refinement and magnetic properties of synthetic Co3Ge2O5(OH)4 phyllogermanate
Колич.характеристики :7 с
Место публикации : J. Magn. Magn. Mater. - 2023. - Vol. 587. - Ст.171262. - ISSN 03048853 (ISSN), DOI 10.1016/j.jmmm.2023.171262. - ISSN 18734766 (eISSN)
Примечания : Cited References: 51. - The authors are grateful to Dr. N.V. Kazak and Dr. A.A. Levin for a lot of fruitful discussions. Magnetisation measurements were carried out in the Common Access Facility Centres of SBRAS (Krasnoyarsk, Russia) X-ray powder diffraction measurements were performed at the Engineering Centre of St. Petersburg State Institute of TechnologyThe study was supported by grant No. 23-22-00245 of the Russian Science Foundation, https://rscf.ru/project/23-22-00245/
Аннотация: Co3Ge2O5(OH)4 relates to a specific group of 1:1 layered compounds with an ability to form either platy or tubular particles depending on chemical composition. Despite successful synthesis and perspective application, there is a lack of information on its crystal structure and magnetic properties, granted by Co ions. Co3Ge2O5(OH)4 phyllogermanate nanoparticles have been obtained using a hydrothermal method and characterised using powder X-ray diffraction and magnetisation measurements. Triclinic symmetry with a 1:P1 space group has been established. The unit cell contains three layers perpendicular to the c crystallographic direction, with 7.6 Å spacing and –b/3 shift of the middle layer. At a low magnetic field of 100 Oe the compound undergoes a magnetic transition at TN=5.2 K. The field of 9 T is not sufficient to take the sample to a magnetically saturated state with an asymptotic magnetic moment of 2.43 μB/Co2+. The estimations of the intralayer and interlayer exchange constants give values of J1/kB=2.75 K and J2/kB=0.25 K, respectively.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Sal'nikova E. I., Denisenko Y. G., Kolesnikov I. E., Lahderanta E., Andreev O. V., Azarapin N. O., Basova S. A., Gubin A. A., Oreshonkov A. S.
Заглавие : Synthesis and luminescent properties of (RE0.95Ln0.05)2O2S (RE = La, Y; Ln = Ho, Tm)
Место публикации : J. Solid State Chem. - 2021. - Vol. 293. - Ст.121753. - ISSN 00224596 (ISSN), DOI 10.1016/j.jssc.2020.121753
Примечания : Cited References: 33
Аннотация: Solid solutions of oxysulfides (RE0.95Ln0.05)2O2S (RE = La, Y; Ln = Ho, Tm) were obtained by hydrogen reduction of the co-precipitated sulfates followed by sulfidation of the reaction products. The crystal chemical characteristics of the obtained compounds were refined by the Rietveld method. Morphological certification of particles in the dynamics of synthesis was performed. Most of the particles produced by chemical reactions have a cut that indicates the formation of a compound with a hexagonal syngony with angles of 60 and 120°. This indicates that the thermal effect of gaseous reagents H2, H2S on sulfates leads to heterogeneous reactions of thermal dissociation and the formation of new phases. Steady state luminescence properties displayed characteristic sharp bands corresponding to 4f-4f transitions. Luminescence decay curves of all studied samples showed monoexponential decay with microsecond and hundreds microsecond lifetimes depending on doping ions. Calculated color coordinates of Ho3+ and Tm3+-doped powders make them promising candidates to be used as phosphors.
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Вид документа : Статья из журнала
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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
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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
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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) : Jiang C., Brik M. G., Li L., Li L., Peng J., Wu J., Molokeev M. S., Wong K. -L., Peng M.
Заглавие : The electronic and optical properties of a narrow-band red-emitting nanophosphor K2NaGaF6:Mn4+ for warm white light-emitting diodes
Место публикации : J. Mater. Chem. C. - 2018. - Vol. 6, Is. 12. - P.3016-3025. - ISSN 20507534 (ISSN), DOI 10.1039/c7tc05098d
Примечания : Cited References: 55. - We acknowledge the financial support received from the Program for Innovative Research Team in University of Ministry of Education of China (Grant No. IRT_17R38), the Key Program of Guangzhou Scientific Research Special Project (Grant No. 201607020009), the National Natural Science Foundation of China (Grant No. 51672085, 51322208, 3160440), and the Fundamental Research Funds for the Central Universities. M. G. Brik acknowledges the supports received from the Recruitment Program of High-end Foreign Experts (Grant No. GDW20145200225), the Programme for the Foreign Experts offered by Chongqing University of Posts and Telecommunications, Ministry of Education and Research of Estonia, (Project PUT430) and European Regional Development Fund (Project TK141), and the Guest Professorship at Kyoto University (Prof. S. Tanabe laboratory). The first-principles calculations were carried out using the resources provided by the Wroclaw centre for Networking and Supercomputing (http://wcss.pl; Grant No. WCSS#10117290).
Ключевые слова (''Своб.индексиров.''): energy efficiency--gallium compounds--light emission--light emitting diodes--manganese--manganese compounds--optical properties--phosphors--precipitation (chemical)--quenching--rietveld refinement--sodium compounds
Аннотация: Recently, as a key red component in the development of warm white light-emitting diodes (WLEDs), Recently, as a key red component in the development of warm white light-emitting diodes (WLEDs), Mn4+-doped fluorides with narrow red emission have sparked rapidly growing interest because they improve color rendition and enhance the visual energy efficiency. Herein, a red nanophosphor, K2NaGaF6:Mn4+, with a diameter of 150-250 nm has been synthesized using a simple co-precipitation method. Rietveld refinement reveals that it crystallizes in the space group Fm3m with the cell parameter a = 8.25320(4) Å. The exchange charge model (ECM) has been used to calculate the energy levels of Mn4+ ions in K2NaGaF6, which match well with the experimental spectra. The as-synthesized phosphor exhibits a narrow red emission at around 630 nm (spin-forbidden 2Eg → 4A2 transition of Mn4+ ions) when excited at 365 nm (4A2g → 4T1g) and 467 nm (4A2g → 4T2g), with a quantum efficiency (QE) of 61% and good resistance to thermal quenching. Based on the structure, the formation mechanism of ZPL has been discussed. In addition, the concentration-dependent decay curves of Mn4+ in K2NaGaF6 were fitted using the Inokuti-Hirayama model, suggesting that the dipole-dipole interactions determine the concentration quenching. Finally, encouraged by the good performance, a warm LED with a CRI of 89.4 and CCT of 3779 K was fabricated by employing the title nanophosphor as the red component. Our findings suggest that K2NaGaF6:Mn4+ can be a viable candidate for the red phosphor used in warm WLEDs.
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Вид документа : Статья из журнала
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Автор(ы) : Коржнева, Ксения Евгеньевна, Исаенко, Людмила Ивановна, Елисеев, Александр Павлович, Голошумова, Алина Александровна, Тарасова, Александра Юрьевна, Молокеев, Максим Сергеевич
Заглавие : Исследования твердых растворов состава Pb1-xBax(NO3)2
Место публикации : Фундамент. пробл. совр. материаловед. - 2018. - Т. 15, № 3. - С. 360-365. - ISSN 1811-1416, DOI 10.25712/ASTU.1811-1416.2018.03.008
Примечания : Библиогр.: 13. - 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 водных растворов--твердый раствор состава pb1-xbax(no3)2--рентгенофазовый анализ--метод ритвельда--crystal growth from aqueous solution--solid solution ofpb1-xbax(no3)2--powder x-ray diffraction analysis--rietveld method
Аннотация: При исследовании системы Pb(NO3)2–Ba(NO3)2–H2O впервые были получены соединения состава Pb0,75Ba0,25(NO3)2, Pb0,68Ba0,32(NO3)2, Ba0,58Pb0,42(NO3)2, Ba0,73Pb0,27(NO3)2. Кристаллы выращивались из водных растворов с разным соотношением Pb(NO3)2 к Ba(NO3)2. Во всех поставленных экспериментах рост осуществлялся путем медленного охлаждения со скоростью 1°С/сутки в диапазоне температур 75 – 45При исследовании системы Pb(NO3)2–Ba(NO3)2–H2O впервые были получены соединения состава Pb0,75Ba0,25(NO3)2, Pb0,68Ba0,32(NO3)2, Ba0,58Pb0,42(NO3)2, Ba0,73Pb0,27(NO3)2. Кристаллы выращивались из водных растворов с разным соотношением Pb(NO3)2 к Ba(NO3)2. Во всех поставленных экспериментах рост осуществлялся путем медленного охлаждения со скоростью 1При исследовании системы Pb(NO3)2–Ba(NO3)2–H2O впервые были получены соединения состава Pb0,75Ba0,25(NO3)2, Pb0,68Ba0,32(NO3)2, Ba0,58Pb0,42(NO3)2, Ba0,73Pb0,27(NO3)2. Кристаллы выращивались из водных растворов с разным соотношением Pb(NO3)2 к Ba(NO3)2. Во всех поставленных экспериментах рост осуществлялся путем медленного охлаждения со скоростью 1oС/сутки в диапазоне температур 75 – 45оС. С помощью рентгенофазового анализа на базе экспериментальных данных была построена часть фазовой диаграммы системы Pb(NO3)2–Ba(NO3)2–H2O и выделены поля кристаллизации Ba(NO3)2 и непрерывного ряда твердых растворов состава Pb1-xBax(NO3)2. Выращенные кристаллы исследовали с помощью рентгенофазового анализа, и для полученных рентгенограмм делали уточнение методом Ритвельда. Все пики на рентгенограммах были проиндексированы кубической центросимметричной структурой (Pa-3) с параметрами, близкими к Ba(NO3)2. При взаимодействии простых соединений нитрата свинца и бария образуется ряд твердых растворов с постепенным увеличением объема и параметров ячейки от чистого нитрата свинца к чистому нитрату бария. Данная структура также характеризуется одинаковым координационным числом катионов 12, разными ионными радиусами Pb 1.49, Ba 1.61, а также одним видом равностороннего NO3 треугольника с углами 60о и длинами связей от 2,1078 до 2,1597. Кристалл Pb0,68Ba0,32(NO3)2 прозрачен в диапазоне 0,304-3,5 микрон. Была проведена оценка ширины запрещенной зоны, которая составила 3,81 и 3,88 эВ при 300 и 80 К, соответственно.С/сутки в диапазоне температур 75 – 45°С. С помощью рентгенофазового анализа на базе экспериментальных данных была построена часть фазовой диаграммы системы Pb(NO3)2–Ba(NO3)2–H2O и выделены поля кристаллизации Ba(NO3)2 и непрерывного ряда твердых растворов состава Pb1-xBax(NO3)2. Выращенные кристаллы исследовали с помощью рентгенофазового анализа, и для полученных рентгенограмм делали уточнение методом Ритвельда. Все пики на рентгенограммах были проиндексированы кубической центросимметричной структурой (Pa-3) с параметрами, близкими к Ba(NO3)2. При взаимодействии простых соединений нитрата свинца и бария образуется ряд твердых растворов с постепенным увеличением объема и параметров ячейки от чистого нитрата свинца к чистому нитрату бария. Данная структура также характеризуется одинаковым координационным числом катионов 12, разными ионными радиусами Pb 1.49, Ba 1.61, а также одним видом равностороннего NO3 треугольника с углами 60° и длинами связей от 2,1078 до 2,1597. Кристалл Pb0,68Ba0,32(NO3)2 прозрачен в диапазоне 0,304-3,5 микрон. Была проведена оценка ширины запрещенной зоны, которая составила 3,81 и 3,88 эВ при 300 и 80 К, соответственно.С. С помощью рентгенофазового анализа на базе экспериментальных данных была построена часть фазовой диаграммы системы Pb(NO3)2–Ba(NO3)2–H2O и выделены поля кристаллизации Ba(NO3)2 и непрерывного ряда твердых растворов состава Pb1-xBax(NO3)2. Выращенные кристаллы исследовали с помощью рентгенофазового анализа, и для полученных рентгенограмм делали уточнение методом Ритвельда. Все пики на рентгенограммах были проиндексированы кубической центросимметричной структурой (Pa-3) с параметрами, близкими к Ba(NO3)2. При взаимодействии простых соединений нитрата свинца и бария образуется ряд твердых растворов с постепенным увеличением объема и параметров ячейки от чистого нитрата свинца к чистому нитрату бария. Данная структура также характеризуется одинаковым координационным числом катионов 12, разными ионными радиусами Pb 1.49, Ba 1.61, а также одним видом равностороннего NO3 треугольника с углами 60° и длинами связей от 2,1078 до 2,1597. Кристалл Pb0,68Ba0,32(NO3)2 прозрачен в диапазоне 0,304-3,5 микрон. Была проведена оценка ширины запрещенной зоны, которая составила 3,81 и 3,88 эВ при 300 и 80 К, соответственно.During the present study of Pb(NO3)2-Ba(NO3)2-H2O system Pb0,75Ba0,25(NO3)2, Pb0,68Ba0,32(NO3)2, Ba0,58Pb0,42(NO3)2, Ba0,73Pb0,27(NO3)2 compounds were obtained for the first time. The crystals were grown from aqueous solutions with different ratios of Pb(NO3)2 to Ba(NO3)2. The growth was carried out by slow cooling at a rate of 1°/day in the temperature range of 75-45°C in all experiments. Using x-ray diffraction phase analysis part of Pb(NO3)2-Ba(NO3)2-H2O phase diagram was built and the crystallization fields of Ba(NO3)2 and a continuous series of Pb1-xBax(NO3)2 solid solutions were selected on the basis of the experimental data. The grown crystals were investigated by x-ray phase analysis and the obtained x-ray diffraction patterns were refined by the Rietveld method. All peaks in patterns were indexed by a cubic centrosymmetric structure (Pa-3) with parameters close to Ba(NO3)2. The interaction of simple compounds of lead and barium nitrates produces a number of solid solutions with a gradual increase in the volume and parameters of the unit cell from pure lead nitrate to pure barium nitrate. Their structure is characterized by the same coordination number (12) for cations with different radii: Pb2+ (1.49), Ba2+ (1.61), as well as one kind of equilateral NO3 triangle with angles of 60° and bond lengths from 2.1078 to 2.197 Å. Pb0,68Ba0,32(NO3)2 crystal is transparent in the range of 0,304-3,5 microns. The band gap was estimated as 3.81 and 3.88 eV at 300 and 80 K, respectively.
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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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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Atuchin V. V., Subanakov A. K., Aleksandrovsky A. S., Bazarov B. G., Bazarova J. G., Gavrilova T. A., Krylov A. S., Molokeev M. S., Oreshonkov A. S., Stefanovich S. Y.
Заглавие : Structural and spectroscopic properties of new noncentrosymmetric self-activated borate Rb3EuB6O12 with B5O10 units
Место публикации : Mater. Des. - 2018. - Vol. 140. - P.488-494. - ISSN 02641275 (ISSN), DOI 10.1016/j.matdes.2017.12.004
Примечания : Cited References: 53. - We are grateful to Guochun Zhang for the crystal structure materials on K3YB6O12 and O. Tsydenova, A. Sarapulova for the consultations. The work was supported by Projects № 0356-2015-0412 of SB RAS Program № II.2P and № 0339-2016-0007. The reported study was funded by RFBR according to research projects 16-52-48010, 17-02-00920, 17-03-00886 and 17-52-53031 and RSF project 14-22-00143. 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 (5.5523.2017/8.9). This research was supported by Grant no. 8.2.01.2017 of Tomsk State University Academic D.I. Mendeleev Fund Program.
Ключевые слова (''Своб.индексиров.''): rubidium rare earth borate--solid state reaction--rietveld refinement--raman--infrared spectroscopy--luminescence
Аннотация: New noncentrosymmetric double borate Rb3EuB6O12 was designed and synthesized by the solid state reaction method, and its crystallographic parameters were obtained by Rietveld analysis. This borate crystallizes in the trigonal space group R32 with cell parameters a = 13.4604(2) Å, c = 30.7981(5) Å, Z = 15. Its structure features a three-dimensional framework composed of the [B5O10]5 − groups that are bridged by Eu-O polyhedra. The existence of B5O10 group in the structure was confirmed by vibrational spectroscopy. Rb3EuB6O12 melts incongruently at 1101 K. The second harmonic generation effect of Rb3EuB6O12 is 16 times higher than that of the α-quartz standard. In the luminescence spectrum, the domination of a single prominent narrow line from the hypersensitive 5D0 - 7F2 manifold of Eu3 + ions is observed, while the 5D0 - 7F1 manifold and ultranarrow 5D0 - 7F0 line are of comparable peak intensity. These features are explained by a specific local symmetry of the Eu3+ ion within the crystal structure of Rb3EuB6O12.
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11.

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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12.

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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13.

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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14.

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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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Atuchin V. V., Molokeev M. S., Yurkin G. Yu., Gavrilova T. A., Kesler V. G., Laptash N. M., Flerov I. N., Patrin G. S.
Заглавие : Synthesis, structural, magnetic, and electronic properties of cubic CsMnMoO3F3 oxyfluoride
Место публикации : J. Phys. Chem. C: American Chemical Society, 2012. - Vol. 116, Is. 18. - P.10162-10170. - ISSN 1932-7447, DOI 10.1021/jp302020f
Примечания : Cited References: 64. - We thank Dr. A.M. Ziatdinov for the electron paramagnetic resonance measurements. This study was partly supported by SB RAS (Grant 28).
Предметные рубрики: RAY PHOTOELECTRON-SPECTROSCOPY
PHASE-TRANSITIONS
CORE LEVELS
SURFACE CHARACTERIZATION
CRYSTAL-STRUCTURE
CLEAVED SURFACE
MIXED-VALENCE
OXIDES
MN
MOLYBDENUM
Chemical bondings
Cubic phase
Energy differences
Heat capacity measurements
Oxyfluorides
Powder samples
Solid-state synthesis
Space Groups
Temperature range
Valence electron
Binding energy
Chemical bonds
Electronic structure
Fluorine compounds
Magnetic properties
Metal ions
Photoelectrons
Rietveld method
X ray photoelectron spectroscopy
Electronic properties
Аннотация: A powder sample of CsMnMoO3F3 oxyfluoride has been prepared by solid state synthesis. The pyrochlore-related crystal structure of CsMnMoO3F3 has been refined by the Rietveld method at T = 298 K (space group Fd-3m, a = 10.59141(4) angstrom, V = 1188.123(8) angstrom(3); R-B = 3.44%). The stability of the cubic phase has been obtained over the temperature range T = 110-293 K by heat capacity measurements. Magnetic properties have been measured over the range of T = 2-300 K. The electronic structure of CsMnMoO3F3 has been evaluated by X-ray photoelectron spectroscopy. Chemical bonding effects have been discussed for all metal ions using binding energy difference parameters and wide comparison with related oxides and fluorides. The competition between O-2(-) and F- ions for metal valence electrons has been found.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Atuchin V. V., Bazarov B. G., Gavrilova T. A., Grossman V. G., Molokeev M. S., Bazarova Zh. G.
Заглавие : Preparation and structural properties of nonlinear optical borates K 2(1-x)Rb 2xAl 2B 2O 7, 0 ˂ x ˂ 0.75
Место публикации : J. Alloys Compd.: Elsevier, 2012. - Vol. 515. - P.119-122. - ISSN 0925-8388, DOI 10.1016/j.jallcom.2011.11.115
Примечания : Cited References: 30. - This study was supported by SB RAS (Grant 34) and RFBR Grants 11-02-90706-mob_st and 11-03-00867a.
Предметные рубрики: UV-light generation
Frequence-conversion
K2Al2B2O7 crystal
Composition ratio
Mixed-crystals
Growth
KRbAl2B2O7
NLO properties
Non-linear optical
Non-linear optical properties
Rietveld analysis of X-ray powder diffraction data
Solubility limits
Space Groups
Structural parameter
Ключевые слова (''Своб.индексиров.''): krbal2b2o7--solid solution--crystal structure--nlo properties
Аннотация: The structures of K 2(1-x)Rb 2xAl 2B 2O 7, x = 0.25, 0.5, 0.75, have been determined in space group P321 through Rietveld analysis of X-ray powder diffraction data. The solubility limit in K 2(1-x)Rb 2xAl 2B 2O 7 crystals has been estimated as x similar to 0.83-0.9. Nonlinear optical properties of KRbAl 2B 2O 7 have been verified by powder Kurtz-Perry method. Mechanisms of structural parameter variation in K 2Al 2B 2O 7 crystal family have been discussed.
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17.

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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18.

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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