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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ji, Haipeng, Hou, Xinghui, Molokeev M. S., Ueda, Jumpei, Tanabe, Setsuhisa, Brik M. G., Zhang, Zongtao, Wang, Y.u., Chen, Deliang
Заглавие : Ultrabroadband red luminescence of Mn4+ in MgAl2O4 peaking at 651 nm
Место публикации : Dalton Trans. - 2020. - Vol. 49, Is. 17. - P.5711-5721. - ISSN 1477-9226, DOI 10.1039/d0dt00931h. - ISSN 1477-9234(eISSN)
Примечания : Cited References: 54. - This study was partly supported by the National Natural Science Foundation of China (Grant No. 51902291 and 51574205), the China Postdoctoral Science Foundation (2019M662524, 2019M652574), the Postdoctoral Research Sponsorship in Henan Province (19030025, 001802045), the Natural Science Foundation of Guangdong Province (2018B030311022), the Guangdong Innovation Research Team for Higher Education (2017KCXTD030), and the High-level Talents Project of Dongguan University of Technology (KCYKYQD2017017). J. U. and S. T. were also supported by the JSPS KAKENHI (16H06441, 19H02798) and M. M. was also supported by the RFBR (19-52-80003).
Предметные рубрики: EMITTING PHOSPHOR
PHOTOLUMINESCENCE PROPERTIES
PHASE-TRANSITION
Аннотация: Blue light pumped red luminescence with broadband and high photon-energy emission is highly desired for phosphor-converted white light-emitting diodes (pc-wLEDs), to achieve a high color rendering index and high luminous efficacy. Mn4+-doped red-emitting phosphors generally exhibit sharp vibronic emissions associated with the parity- and spin-forbidden 2Eg → 4A2g transitions. In this paper, two abnormal luminescence behaviors were observed for Mn4+ in the MgAl2O4:Mn4+ spinel phosphor with a short wavelength emission band peaking at 651 nm. Firstly, the Mn4+ 2Eg → 4A2g transition exhibits ultrabroadband luminescence in MgAl2O4 and the large full-width at half-maximum (FWHM) is dependent both on the calcination temperature and on the partial substitution of Al3+ with Ga3+. Secondly, the thermal quenching behavior of the Mn4+ 2Eg → 4A2g luminescence in MgAl2O4 shows a dependence on its thermal treatment and preparation method. The Rietveld refinement and Raman results demonstrate that the variation in the FWHM of the luminescence spectra is a sum effect of structural ordering (i.e., isotropic displacement decrease of constituent atoms) and the Mg ↔ Al anti-site disorder. A model for the observed varying thermal quenching of luminescence was tentatively proposed. The intrinsic thermal quenching temperature of Mn4+ luminescence in MgAl2O4 was found to be 390–400 K using the samples prepared by the co-precipitation and molten salt methods. The present work gives a novel perspective to understand the luminescence spectra of Mn4+ 2Eg → 4A2g transition.
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Wang, Naizheng, Jiang, Xingxing, Molokeev M. S., Song, Gaomin, Guo, Shibin, Huang, Rongjin, Li, Laifeng, Wu, Yicheng, Lin, Zheshuai
Заглавие : Linear Zero Thermal Expansion in a Deep-Ultraviolet Transparent Crystal of BPO4 with Cristobalite-like Structure
Коллективы : National Scientific Foundations of China [51872297, 51702330, 51802321, 51890864]; Fujian Institute of Innovation [FJCXY18010201]; Youth Innovation Promotion Association in CAS [2017035]
Место публикации : Cryst. Growth Des. - 2019. - Vol. 19, Is. 6. - P.3109-3112. - ISSN 1528-7483, DOI 10.1021/acs.cgd.9b00361. - ISSN 1528-7505(eISSN)
Примечания : Cited References: 32. - This work was supported by the National Scientific Foundations of China (Grants 51872297, 51702330, 51802321 and 51890864) and Fujian Institute of Innovation (FJCXY18010201) in CAS, and the Youth Innovation Promotion Association in CAS (outstanding member for Z.L. and Grant 2017035 for X.J.).
Предметные рубрики: PHASE-TRANSITION
DIFFRACTION
QUARTZ
Аннотация: We report the discovery of the zero thermal expansion (ZTE) effect in BPO4, a famous deep-ultraviolet (DUV) optical material with cristobalite-like structure. It is revealed that BPO4 has a linear ZTE coefficient of -0.16(5) MK-1 along the c-axis as temperature increases from 13 to 300 K, which originates from the subtle counterbalance between the rotation-induced expansion and contraction effects among BO4 and PO4 groups. BPO4 is a unique DUV cristobalite-like material exhibiting the linear ZTE behavior.
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zaytseva I. V., Pugachev A. M., Okotrub K. A., Surovtsev N. V., Mikerin S. L., Krylov A. S.
Заглавие : Residual mechanical stresses in pressure treated BaTiO3 powder
Коллективы : RFBR [17-32-5009, 18-02-00399, AAAA-A17-117052410033-9]
Место публикации : Ceram. Int. - 2019. - Vol. 45, Is. 9. - P.12455-12460. - ISSN 0272-8842, DOI 10.1016/j.ceramint.2019.03.179. - ISSN 1873-3956(eISSN)
Примечания : Cited References: 33. - The reported study was funded by RFBR according to the research projects No. 17-32-5009, 18-02-00399 and State assignment No AAAA-A17-117052410033-9. The experiments were performed in the multiple-access center "High-Resolution Spectroscopy of Gases and Condensed Matter" in IA&E SBRAS (Novosibirsk, Russia) and Center for Common Use of the Krasnoyarsk Scientific Center, SBRAS (Krasnoyarsk, Russia).
Предметные рубрики: DIELECTRIC-PROPERTIES
PHASE-TRANSITION
DIAMOND ANVILS
RAMAN
Ключевые слова (''Своб.индексиров.''): residual mechanical stress--raman spectroscopy--high non-hydrostatic pressure--temperature treatment--residual pressure--batio3 ceramics
Аннотация: Here we present Raman spectroscopy approach to monitor the spatial distribution and the magnitude of the residual mechanical stresses in ceramic after non-hydrostatic pressure treatments. The residual pressure can be found from the E-phonon line shift (∼307 cm−1) in the Raman spectra. The relationship between the non-hydrostatic pressure (up to 11 GPa) and the shift of this line has been established. It is demonstrated that the change in the Raman line position (1332 cm−1) of the diamond anvil can be used for monitoring of applied non-hydrostatic pressures. A linear dependence of residual mechanical stresses on the applied pressures is found. Micro-Raman spectroscopy shows that the residual mechanical stresses are distributed fairly uniformly in the studied BaTiO3 samples at the micron scale. In the future, the proposed Raman technique can be used for monitoring the quality of produced BaTiO3 ceramics.
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Dudnikov V. A., Kazak N. V., Orlov Yu. S., Vereshchagin S. N., Gavrilkin, S. Yu., Tsvetkov, A. Yu., Gorev M. V., Veligzhanin A. A., Trigub A. L., Troyanchuk I. O., Ovchinnikov S. G.
Заглавие : Structural, Magnetic, and Thermodynamic Properties of Ordered and Disordered Cobaltite Gd0.1Sr0.9CoO3 – δ
Коллективы : Russian Foundation for Basic Research [17-02-00826, 16-02-00507, 18-52-00017 Bel_a]; Russian Federation [SP-1844.2016.1]; Ministry of Education and Science of the Russian Federation [RFMEFI61917X0007]
Место публикации : J. Exp. Theor. Phys. - 2019. - Vol. 128, Is. 4. - P.630-640. - ISSN 1063-7761, DOI 10.1134/S1063776119020171. - ISSN 1090-6509(eISSN)
Примечания : Cited References: 27. - This work was supported by the Russian Foundation for Basic Research (grant nos. 17-02-00826, 16-02-00507, and 18-52-00017 Bel_a) and by the Council on Grants of the President of the Russian Federation (SP-1844.2016.1). X-ray spectra were recorded using the equipment of a unique scientific facility Kurchatov Synchrotron Radiation Source financed by the Ministry of Education and Science of the Russian Federation (project ID RFMEFI61917X0007).
Предметные рубрики: PROFILE REFINEMENT
PHASE-TRANSITION
OXYGEN SORPTION
PEROVSKITE
Аннотация: The effect of cationic and anionic orderings on the crystal structure and magnetic properties of substituted rare-earth cobaltites Gd0.1Sr0.9CoO3 – δ was studied using X-ray diffraction, measurement of XANES spectra, and magnetic and thermodynamic characteristics. The effects of ordering cause a decrease in symmetry to tetragonal and a distortion of the coordination octahedra of CoO6. Anomalous magnetic and thermodynamic quantities are observed at 260 and 360 K, respectively, for disordered and ordered samples. The XANES spectra measured at the CoK edge did not reveal a noticeable shift in the absorption edge compared with the spectrum of original GdCoO3. This suggests that the charge compensation process is associated not only with a change in the electronic state of cobalt ions, but also with the emergence of holes in the 2p states of oxygen.
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Аверьянов, Евгений Михайлович
Заглавие : Температурные зависимости показателей преломления одноосных каламитных жидких кристаллов с высоким двупреломлением
Место публикации : Жидк. кристаллы и их практич. использ. - 2018. - Т. 18, № 2. - С. 53-63. - ISSN 1991-3966, DOI 10.18083/LCAppl.2018.2.53; Liq. Cryst. Appl.
Примечания : Библиогр.: 29
Предметные рубрики: PHASE-TRANSITION
ORIENTATIONAL ORDER
ISOTROPIC LIQUID
MOLECULES
Ключевые слова (''Своб.индексиров.''): жидкие кристаллы--температурные зависимости показателей преломления--liquid crystals--temperature dependences of the refractive indices
Аннотация: Температурные зависимости показателей преломления nj(t) и величин n(t) = (n|| + 2n⊥)/3, n(t) =ε-1/2, ε= (ε|| + 2ε⊥)/3, εj = nj2 для световых волн с поляризацией вдоль (j = ||) и нормально директору (j = ⊥) в одноосных каламитных жидких кристаллах (ЖК) исследованы в рамках микроскопического подхода с учетом анизотропии тензора локального поля fj(t) =1 + Lj(t)[εj(t)–1] и тензора Лорентца Lj(t). Показано, что известные отрицательные производные n(t)' = dn(t)/dt, n' и точка to минимума на зависимости n⊥(t) в каламитных ЖК отвечают малым и средним значениям двупреломления Δn = n|| – n⊥. Для ЖК с высокими величинами Δn и компонентами L⊥, превышающими пороговое значение L⊥e(nj), предсказаны два новых эффекта: положительные значения n', и наличие точки te максимума на зависимости n||(t). Для ряда нематиков с высокими значениями Δn определены компоненты Lj(t), подтверждено наличие предсказанных эффектов и условий их проявления, получены значения te и прослежена их связь с величиной Δn. Выяснены особенности перехода от ЖК с точкой to к ЖК с точкой te по мере роста Δn.The temperature dependences of the refractive indices nj(t) and the values n(t) = (n|| + 2n⊥)/3, n(t) =ε-1/2, ε= (ε|| + 2ε⊥)/3, εj = nj2 for the light waves polarized along (j = ||) and across (j = ⊥) the director in uniaxial calamitic liquid crystals (LCs) were studied within the microscopic approach with taking into account the anisotropy of the local-field tensor fj(t) =1 + Lj(t)[εj(t)–1] and the Lorentz tensor Lj(t). The known negative derivatives n(t)' = dn(t)/dt, n' and the point to of minimum at the dependence n⊥(t) for calamite LCs were shown to correspond to small and medium values of the birefringence Δn = n|| – n⊥. For LCs with high values of δn and components L⊥ exceeding the threshold value L⊥e two new effects were predicted: positive derivatives n', and the presence of the point te of maximum at the dependence n||(t). For a number of nematics with high values of Δn the components Lj(t) were determined, the presence of the predicted effects and the conditions for their manifestation were confirmed, the values te were obtained and their connection with the magnitude Δn were established. The features of the transition from LCs with point to to LCs with point c under gradual increase in Δn were cleared up.
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Верещагин С. Н., Дудников, Вячеслав Анатольевич, Соловьев, Леонид Александрович
Заглавие : Изучение фазового перехода порядок-беспорядок в нестехиометрическом Sr-Gd-кобальтате методами ДСК, ТГ и РСА
Место публикации : Журн. СФУ. Сер. "Химия". - 2016. - Т. 9, № 3. - С. 326-336. - ISSN 1998-2836, DOI 10.17516/1998-2836-2016-9-3-326-336; J. Sib. Fed. Univ. Chem. - ISSN 2313-6049(eISSN)
Примечания : Библиогр.: 26. - Исследование выполнено при финансовой поддержке Российского фонда фундаментальных исследований, Правительства Красноярского края, Красноярского краевого фонда поддержки научной и научно-технической деятельности в рамках научного проекта 16-43-240505 «р_а».
Предметные рубрики: PEROVSKITE-TYPE OXIDES
PHASE-TRANSITION
OXYGEN SORPTION
PERFORMANCE
Ключевые слова (''Своб.индексиров.''): perovskite--order-disorder--phase transition--dsc--перовскит--порядок-беспорядок--фазовый переход--дск
Аннотация: Методами термического и рентгеноструктурного анализа в интервале температур 11001473 К изучен процесс взаимопревращения тетрагонального перовскита Sr ( 0.8 ) Gd ( 0.2 ) CoO ( 3-d ) с упорядоченным расположением катионов Sr/Gd и анионных вакансий в кубическую разупорядоченную модификацию. Показано, что фазовое превращение протекает как размытый фазовый переход первого рода. Процесс разупорядочения не зависит от скорости нагрева и контролируется термодинамическими характеристиками процессов в кристалле, тогда как процесс образования упорядоченной тетрагональной структуры контролируется кинетическими факторами. Проведен количественный анализ температурной зависимости теплоемкости на основе размытых фазовых переходов.Process of interconversion of tetragonal Sr(0.8) Gd(0.2) CoO(3-d) (with ordered Sr/Gd cations and anion vacancies) to cubic one (with disordered structure) was studied by X-ray structural and thermal analysis at 1100-1473 K. It was shown that the transformation is a first order diffuse phase transition. The ramp rate does not affect cation and anion vacancies disordering which is controlled by thermodynamic parameters of the processes in the solid whereas cubic to tetragonal transition is kinetically controlled. A theory of diffuse phase transition was applied to quantitatively analyze heat capacity temperature dependence.
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Drokina T. V., Petrakovskii G. A., Molokeev M. S., Bondarev V. S., Velikanov D. A.
Заглавие : Synthesis and study of structural, thermodynamic, and magnetic properties of NaxLi1–xFeGe2O6 (x = 0.1–0.9) compounds
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2016. - Vol. 58, Is. 7. - P.1361-1370. - ISSN 10637834 (ISSN), DOI 10.1134/S1063783416070143
Примечания : Cited References: 20
Предметные рубрики: CLINOPYROXENE-TYPE LiFeGe2O6
PHASE-TRANSITION
PYROXENES
TEMPERATURE
LiFeSi2O6
CRYSTAL
Аннотация: The properties of NaxLi1–xFeGe2O6 (x = 0.1–0.9) solid solutions obtained via a solid-phase synthesis have been measured by X-ray diffraction, calorimetry, and magnetic method. The order–disorder transformations in low-dimensional NaxLi1–xFeGe2O6 (x = 0.1–0.9) spin systems with predominately antiferromagnetic exchange interaction have been revealed in the low-temperature susceptibility dependences. The study of thermal and physical properties has confirmed that substituting the sodium ions with the lithium ones induces the first-order structural phase transitions of the displacement type which are characterized by a symmetry change in monoclinic crystals from high-temperature C2/c space group to low-temperature P21/c space group. © 2016, Pleiades Publishing, Ltd.
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Ovchinnikova T. M., Plotkin V. V., Dyad'kov P. G.
Заглавие : Spin crossover and Mott-Hubbard transition under high pressure and high temperature in the low mantle of the Earth
Коллективы : International conference on interaction of intense energy fluxes , International Conference on Interaction of Intense Energy Fluxes with Matter (XXX; 1–6 March 2015; Elbrus, Kabardino-Balkaria, Russia)
Место публикации : J. Phys.: Conf. Ser./ International conference on interaction of intense energy fluxes (30 ; 2015 ; March ; 01-06): IOP Publishing, 2015. - Vol. 653. - Ст.012095. - ISSN 1742-6588, DOI 10.1088/1742-6596/653/1/012095
Примечания : Cited References:22
Предметные рубрики: PHASE-TRANSITION
GEOMAGNETIC DATA
MAGNESIOWUSTITE
IRON
METALLIZATION
LAYER
Аннотация: Effect of high pressure induced spin crossover on the magnetic, electronic and structural properties of the minerals forming the Earth's low mantle is discussed. The low temperature P, T phase diagram of ferropericlase has the quantum phase transition point P = 56 GPa at T = 0 confirmed recently by the synchrotron Mossbauer spectroscopy. The LDA+GTB calculated phase diagram describes the experimental data. Its extension to the high temperature resulted earlier in prediction of the metallic properties of the Earth's mantle at the depth 1400 km h 1800 km. Estimation of the electrical conductivity based on the percolation theory is given. We discuss also the thermodynamic properties and structural anomalies resulting from the spin crossover and metal insulator transition and compare them with the experimental seismic and geomagnetic field data.
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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S., Romanova O. B., Har'kov A. M., Balaev D. A., Gorev M. V., Vorotynov A. M., Sokolov V. V., Pichugin A.
Заглавие : Metal–semiconductor transition in SmxMn1−xS solid solutions
Место публикации : Phys. Status Solidi B. - 2012. - Vol. 249, Is. 4. - P.812-817. - ISSN 0370-1972, DOI 10.1002/pssb.201147327
Примечания : Cited References: 27. - This study was supported by the Russian Foundation for Basic Research project No 09-02-00554_a; No 09-02-92001-NNS_a; No 11-02-98018 r_sibir_a; ADTP "Development of scientific potential of the higher school" No. 2.1.1/11763.
Предметные рубрики: Magnetic-properties
Phase-transition
SmS
Valence
Pressure
Crystal
Lattice
CeRhSb
Ключевые слова (''Своб.индексиров.''): kondo effect--metal-semiconductor transition--semiconductors--variable-valence elements
Аннотация: The electrical resistivity of the SmxMn1−xS (0.15 ≤ x ≤ 0.25) solid solutions in the temperature range of 80–300 K was measured. Minimum and maximum in the temperature dependence of the resistivity were found, respectively, at T = 220 K for x = 0.15 and at T = 100 K for x = 0.2 compounds. This behavior is explained from the result of the mobility-edge movement, the disorder being due to elastic deformation and spin density fluctuations with short-range order. Metal–semiconductor phase transition versus concentration at xc = 0.25 is observed. Resistivity is described by scattering electrons with acoustic phonon mode and with localized manganese spin. From the thermal expansion coefficient the compression of the lattice below the Néel temperature for Sm0.2Mn0.8S is found.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Lyubutin I. S., Ovchinnikov S. G., Gavriliuk A. G., Struzhkin V. V.
Заглавие : Spin-crossover-induced Mott transition and the other scenarios of metallization in 3d(n) metal compounds
Разночтения заглавия :авие SCOPUS: Spin-crossover-induced Mott transition and the other scenarios of metallization in 3 dn metal compounds
Место публикации : Phys. Rev. B: AMER PHYSICAL SOC, 2009. - Vol. 79, Is. 8. - Ст.85125. - ISSN 1098-0121, DOI 10.1103/PhysRevB.79.085125
Примечания : Cited References: 41
Предметные рубрики: RARE-EARTH ORTHOFERRITES
NARROW ENERGY BANDS
HIGH-PRESSURE
MAGNETIC COLLAPSE
ELECTRON CORRELATIONS
PHASE-TRANSITION
STATE
Y3FE5O12
OXIDES
EQUATION
Ключевые слова (''Своб.индексиров.''): bismuth compounds--hubbard model--localised states--metal-insulator transition--metallisation--spin systems
Аннотация: A different "Hubbard energy control" mechanism of the insulator-metal transition (IMT) in Mott-Hubbard insulators is discussed. This mechanism can be initiated by the lattice compression and it is driven by a spin crossover of 3d(5) ions from the high-spin state to the low-spin state. The spin crossover suppresses the effective Hubbard parameter U-eff down to the value enabling the insulator-metal transition according to the Mott mechanism U-eff/W approximate to 1. The classification of possible scenarios of metallization in the other 3d(n) metal compounds is also performed.
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