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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Nikiforov A. A., Krylov A. S., Krylova S. N., Gorshkov V. S., Pelegov D. V.
Заглавие : Temperature Raman study of Li4Ti5O12 and ambiguity in the number of its bands
Колич.характеристики :10 с
Место публикации : J. Raman Spectrosc. - 2024. - Vol. 55, Is. 3. - P.406-415. - ISSN 03770486 (ISSN), DOI 10.1002/jrs.6641. - ISSN 10974555 (eISSN)
Примечания : Cited References: 51. - The research was funded by the Russian Science Foundation (project No 22-22-00350, https://rscf.ru/project/22-22-00350)
Аннотация: The two primary physical methods for identifying lithium titanate, a negative electrode material used commercially, are X-Ray diffraction and Raman spectroscopy. Although there are many publications on this topic, they are focused mainly on chemistry, so there are still some points that require clarification from a physical and methodological point of view. Difference of experimentally observed and theoretically predicted Raman spectra was explained through a combination of experiments and computations. The work comprises experiments and computations to explain why there are different numbers of predicted and observed Raman-active bands. Our low-temperature study and the analysis of thermal shifts during heating led us to conclude that the approach with surplus bands is advantageous and we recommend using major F2g band shifts to estimate the sample heating.
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krylov A. S., Krylova S. N., Vtyurin A. N., Roginskii, Evgenii M., Jin, Li, Tian, Ye, Wei, Xiaoyong
Заглавие : Temperature phase transitions in silver niobate and lithium-tantal-modified silver niobate ceramics
Место публикации : Phys. Chem. Chem. Phys. - 2023. - Vol. 25, Is. 16. - P.11410-11417. - ISSN 14639076 (ISSN), DOI 10.1039/D3CP00607G. - ISSN 14639084 (eISSN)
Примечания : Cited References: 42. - The work was financially supported by the Russian Foundation for Basic Research and DFG project number No 21-52-12018. The temperature Raman experiments were performed in the Krasnoyarsk Regional Center of Research Equipment of Federal Research Center “Krasnoyarsk Science Center SB RAS”
Аннотация: The temperature behaviour of the 0.955 AgNbO3--0.045 LiTaO3and AgNbO3 ceramics were studied in the range from 10 to 415 K by Raman spectroscopy. Ab initio calculations of the Raman spectra in the Pmc21 phase of AgNbO3 were carried out using three potentials (A-PZ, PBE, PBEsol) for spectra interpretation. The Raman spectra peculiarities in AgNbO3 ceramics is observed and explained. The differences in the spectra of the 0.955 AgNbO3--0.045 LiTaO3 and AgNbO3 ceramics are shown. The temperatures of structural changes in the 0.955 AgNbO3--0.45 LiTaO3 and AgNbO3 ceramics were discussed. The structural phase transition below 120 K have been observed in silver niobate. The phase transition has been observed at 310 K and below 150 K in 0.955 AgNbO3--0.045 LiTaO3.
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Isaenko L., Dong L., Kurus A., Lin Z., Yelisseyev A., Lobanov S., Molokeev M. S., Korzhneva K., Goloshumova A.
Заглавие : LixAg1–xGaSe2: interplay between lithium and silver in mid-infrared nonlinear optical chalcogenides
Место публикации : Adv. Opt. Mater. - 2022. - Vol. 10, Is. 24. - Ст.2201727. - ISSN 21951071 (ISSN), DOI 10.1002/adom.202201727
Примечания : Cited References: 37. - This work was supported by the National Natural Science Foundation of China (Grant No. 22133004), Russian Science Foundation, grant # 19‐12‐00085‐P (crystal growth, crystal structure analysis, band gap measurement) and partly done on state assignment of IGM SB RAS (composition chemical analysis)
Аннотация: AgGaSe2 and LiGaSe2 are two famous mid-infrared nonlinear optical (NLO) materials with similar chemical formula but different structural symmetry. The former material has relatively larger NLO effect and birefringence but rather small energy band gap, while the latter is the opposite. Aiming at achieving a good balance of NLO properties, here the substitution between silver and lithium ions on the evolution of structural and optical properties in a new series of LixAg1–xGaSe2 crystals is systematically investigated. It reveals that, with the increase of Li content, LixAg1–xGaSe2 almost keeps the same tetragonal symmetry with AgGaSe2 until x ≈ 0.9. The NLO effects and birefringence values vary with respect to x with the largest variation at x = 0.8–0.9. The optimal combination of birefringence (0.03–0.025) and nonlinear parameters (26–30 pm V−1) is achieved at x = 0.4–0.5. As the energy band gap increases with the increase of x, the maximal value of 2.2 eV for chalcopyrite structure suggests that the laser-induced damage threshold of LixAg1–xGaSe2 would be as large as five-fold of AgGaSe2. This study provides a good example to show that the rational substitution between Li and Ag can significantly improve the balance of NLO properties in chalcogenides.
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kurus, Alexey, Yelisseyev, Alexander, Lobanov, Sergei, Plyusnin, Pavel, Molokeev M. S., Solovyev, Leonid, Samoshkin, Dmitry, Stankus, Sergei, Melnikova S. V., Isaenko, Lyudmila
Заглавие : Thermophysical properties of lithium thiogallate that are important for optical applications
Коллективы : Russian Science Foundation, RussiaRussian Science Foundation (RSF) [19-12-00085]; RFBRRussian Foundation for Basic Research (RFBR) [20-42-543006\20]; Novosibirsk region [20-42-543006\20]
Место публикации : RSC Adv. - 2021. - Vol. 11, Is. 62. - P.39177-39187. - ISSN 2046-2069(eISSN), DOI 10.1039/d1ra05698k
Примечания : Cited References: 41. - Crystal growth and investigation of physical properties were supported by Russian Science Foundation, Russia (#19-12-00085). Spectroscopic study was performed on a state assignment of the Institute of Geology and Mineralogy, Siberian Branch of Russian Academy of Sciences Russia and Ministry of Science and Higher Education, Russia. Measurements of thermal conductivity were funded by RFBR and Novosibirsk region (grant #20-42-543006\20)
Предметные рубрики: NON-ENANTIOMORPHOUS CRYSTAL
MID-IR
SINGLE-CRYSTALS
FLASH METHOD
Аннотация: Lithium thiogallate LiGaS2 is one of the most common nonlinear crystals for mid-IR due to its extreme beam strength and wide transparency range; however, its thermophysical properties have not yet been practically studied. Large crystals of high optical quality are grown. DTA revealed features at 1224 K below melting point (1304 K) that are associated with the oxygen containing compounds of the LiGaO2−xSx type. The thermal conductivity of LiGaS2 (about 10.05 W (m−1 K−1)) and band gap value (3.93 eV at 300 K) are found to be the highest in the LiBC2 family. Isotropic points in the dispersion characteristics for the refractive index are found and LiGaS2-based narrow-band optical filters, smoothly tunable with temperature changes, are demonstrated. Intense blue photoluminescence of anionic vacancies VS is observed at room temperature after annealing LiGaS2 in vacuum, whereas orange low-temperature emission is related to self-trapped excitons. When LiGaS2 crystals are heated, spontaneous luminescence (pyroluminescence) takes place, or thermoluminescence after preliminary UV excitation; the parameters of traps of charge carriers are estimated. The obtained data confirm the high optical stability of this material and open up prospects for the creation of new optical devices based on LiGaS2.
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Drokina T. V., Petrakovskii G. A., Bayukov O. A., Molokeev M. S., Vorotynov A. M., Popkov S. I., Velikanov D. A.
Заглавие : Physical properties of a frustrated uasi-one-dimensional NaCuFe2(VO4)3 magnet and effect of chemical pressure induced by the substitution of sodium for lithium
Место публикации : Phys. Solid State. - 2020. - Vol. 62, Is. 2. - P.297-307. - ISSN 10637834 (ISSN), DOI 10.1134/S1063783420020122
Примечания : Cited References: 22
Аннотация: The structural, thermal, static magnetic, and resonance properties of the low-dimensional NaCuFe2(VO4)3 compound obtained by the solid-phase synthesis have been investigated. In the temperature range of 110–300 K, the electron spin resonance in the X band with a g factor of 2.008 has been detected. The magnetic properties of a sample with a high frustration level in the paramagnetic, antiferromagnetic, and disordered states have been examined. A shift of the Neel temperature to the high-temperature region in an external magnetic field has been observed. The origin of the disordered magnetism in NaCuFe2(VO4)3 are discussed. The features of substitution of sodium for lithium on the physical properties of the ACuFe2(VO4)3 (A = Na, Li) system have been established. It is shown that the chemical pressure changes the crystal lattice parameters, spacings between magnetic ions, and crystallite size, which is reflected in the physical properties of the material.
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6.

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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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Golovnev N. N., Molokeev M. S., Lesnikov M. K., Vereshchagin S. N.
Заглавие : Polymeric lithium(I) diaquabarbiturate: Crystal structure
Коллективы : Ministry of Education and Science of the Russian Federation [3049]
Место публикации : Russ. J. Inorg. Chem.: MAIK Nauka-Interperiodica / Springer, 2017. - Vol. 62, Is. 6. - P.746-750. - ISSN 0036-0236, DOI 10.1134/S0036023617060092. - ISSN 1531-8613(eISSN)
Примечания : Cited References:23. - This work was performed in the Siberian Federal University within the State task of the Ministry of Education and Science of the Russian Federation for the period of 2014-2016 (project no. 3049).
Предметные рубрики: IONIC CO-CRYSTALS
BARBITURIC-ACID
COMPLEXES
NA
LI
Аннотация: The lithium(I) catena-diaquabarbiturate complex [Li(H2O)2(HBA–O,O′)]n (I), where Н2ВА is barbituric acid, has been structurally characterized by X-ray diffraction (CIF file CCDC no. 1447689), and its thermal decomposition and IR spectrum have been studied. Crystals of complex I are monoclinic, a = 6.4306(7) Å, b = 16.720(1) Å, c = 7.1732(8) Å, β = 108.253(4)°, V = 732.5(1) Å3, space group P21/c, and Z = 4. One independent μ2-bridging HBA– ligand is coordinated to two Li(I) ions via the two oxygen atoms of C4(6)=O carbonyl groups. Each Li+ ion is linked with two μ2-HBA– ions and two terminal water molecules at tetrahedron vertices. μ2-HBA– ions link tetrahedra into a chain. The structure is stabilized by multiple hydrogen bonds and π–π-interaction between HBA–. The shift of ν(C=O) vibration bands in the IR spectrum of complex I in comparison with Н2ВА towards lower frequencies agrees with the coordination of HBA– via oxygen atoms. The dehydration of complex I occurs in two stages in the regions of 100–150 and 150–240°C.
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8.

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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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorev M. V., Bondarev V. S., Raevskaya S. I., Flerov I. N., Malitskaya M. A., Raevskii I. P.
Заглавие : Thermophysical study of structural phase transitions in Na0.95Li0.05NbO3 solid solution
Место публикации : Bull. Russ. Acad. Sci. Phys.: Allerton Press, 2016. - Vol. 80, Is. 9. - P.1046-1050. - ISSN 10628738 (ISSN), DOI 10.3103/S1062873816090148
Примечания : Cited References: 18. - This work was supported by Southern Federal University, project no. 213.01-2014/012-VG.
Ключевые слова (''Своб.индексиров.''): niobium oxide--sodium--specific heat--temperature distribution--thermal expansion--ceramic samples--effect of heat treatments--possible mechanisms--sodium lithium niobate--structural distortions--structural phase transition--temperature dependence--temperature range--lithium
Аннотация: Temperature dependences of specific heat Cp(T) and coefficient of thermal expansion α(T) for Na0.95Li0.05NbO3 sodium-lithium niobate ceramic samples are investigated in the temperature range of 100–800 K. The Cp(T) and α(T) anomalies at T3 = 310 ± 3 K, T2 = 630 ± 8 K, and T1 = 710 ± 10 K are observed, which correspond to the sequence of phase transitions N ↔ Q ↔ S(R) ↔ T2(S). The effect of heat treatment of the samples on the sequence of structural distortions was established. It is demonstrated that annealing of the samples at 603 K leads to splitting of the anomaly corresponding to the phase transition Q → R/S in two anomalies. After sample heating to 800 K, the only anomaly is observed in both the Cp(T) and α(T) dependence. Possible mechanisms of the observed phenomena are discussed.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Михалева Н. С., Кузубов, Александр Александрович, Попов, Захар Иванович, Еремина А. Д., Высотин, Максим Александрович
Заглавие : Теоретическое исследование внедрения атомов лития в кремний
Место публикации : Вестник СибГАУ. - Красноярск: СибГАУ, 2015. - Т. 16, № 2. - С. 456-463. - ISSN 1816-9724
Примечания : Библиогр.: 55
Ключевые слова (''Своб.индексиров.''): диффузия--литий--кремний--dft--diffusion--lithium--silicon
Аннотация: Рассматривается процесс диффузии атомов лития в приповерхностные слои кремния (001). Расчеты выполнялись в рамках теории функционала плотности. Показано, что при малой концентрации лития на реконструированной поверхности кремния (001) энергия связи в подповерхностном слое ниже, чем на поверхности, что препятствует диффузии лития внутрь кристалла. Подобная ситуация существенно не меняется при увеличении температуры. Анализ частот перескока одиночных атомов лития с поверхности в приповерхностные слои показал, что в случае малых концентраций миграция атомарного Li будет осуществляться практически по одному пути реакции (из положения L-состояния, в котором литий находится в канале между димерами). При концентрации лития в два монослоя, наоборот, диффузия в подповерхностные слои становится более предпочтительна. Поскольку при достижении концентрации в один монослой происходит изменение симметрии димеров, диффузия лития внутрь кристалла также облегчается вследствие увеличения плотности положений в каналах между димерами. Таким образом, результат моделирования позволил объяснить причину экспериментального факта затруднения диффузии лития при прохождении через данную поверхность и определить пути возможной модификации поверхности, которая должна увеличить энергию связи атомов лития в приповерхностных состояниях при низких степенях заполнения им поверхности.The article deals with a theoretical investigation of lithium diffusion through silicon (001) surface within density functional theory formalism. It was shown that it is more energetically favorable for dilute lithium atoms to stay atop fully-relaxed silicon (001) surface than beneath it. This fact hampers the diffusion into the silicon crystal and the situation doesn't change significantly with increase in temperature. The frequencies of lithium atom hopping from the surface to the subsurface layers of silicon crystal were estimated. The analysis of frequencies for different transition paths indicates that in the case of dilute concentration Li atoms are likely to migrate through the surface from one type of sites (site L-located in channels between silicon dimers). With increasing of lithium concentration up to 1 monolayer and further, the silicon (001) surface swaps the asymmetric dimers reconstruction model for symmetric, leading to doubling of number of the sites in between silicon dimers. After the concentration reaches 2 monolayers, the binding energy of Li atoms on the surface becomes less than binding energy beneath the surface, so the diffusion turns to be thermodynamically allowed. As a result of the investigation, the ab-initio modeling puts light on the cause of experimentally observed decelerated lithium diffusion through silicon (001) surface and delivers an opportunity to determine possible techniques for surface modification, which will increase lithium atom binding energies in sites beneath silicon surface at low lithium concentrations.
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