INFLUENCE OF THE METHOD OF DOPING ON UNIFORMITY AND OPTICAL PROPERTIES OF LiNbO:Mg CRYSTALS

Представлены результаты сравнительных комплексных исследований методами спектроскопии комбинационного рассеяния света и лазерной коноскопии композиционной однородности и некоторых оптических свойства близких по составу сильно легированных монодоменизированных кристаллов LiNbO: Mg (5,03 мол. % MgO и LiNbO: Mg (4,75 мол. % MgO), с концентрацией магния, близкой к пороговому значению ≈ 5 мол. % MgO, выращенных из шихты, синтезированной с использованием прекурсора NbO : Mg (метод гомогенного легирования), а также выращенных при непосредственном добавлении магния в расплав (метод прямого легирования). Показано, что методом гомогенного легирования с использованием прекурсора NbO : Mg можно получать отличающиеся низким коэрцитивным полем более композиционно однородные сильно легированные монокристаллы LiNbO : Mg, чем методом прямого легирования расплава магнием. При этом более однородное распределение легирующей добавки в кристаллах гомогенного легирования начинает формироваться уже на стадии синтеза прекурсора NbO : Mg и шихты ниобата лития при формировании химически активных комплексов, определяющих преимущественно кислородно-октаэдрическую структуру прекурсора NbO : Mg. The paper considers results for strongly doped turned to a single domain state crystals LiNbO: Mg (5,03 mol % MgO and LiNbO: Mg (4,75 mol % MgO). Magnesium concentration in these crystals is close to each other and to threshold ≈ 5 mol % MgO . Crystals were grown from a charge synthesized using precursor LiNbO: Mg (homogeneous doping method) and from a charge obtained at a direct addition of magnesium to the charge (direct doping method). Complex studies were carried out by Raman spectroscopy and laser conoscopy. Compositional homogeneity and some optical properties of studied crystals are considered. Homogeneous doping with precursor NbO: Mg method allows us to obtain heavily doped LiNbO: Mg single crystals with low coercive field and more compositionally homogeneous than method of direct melt doping with magnesium. In this case, a more uniform distribution of the dopant in homogeneously doped crystals begins to form at the stage of NbO: Mg precursor synthesis during the formation of chemically active complexes that predominantly determine the oxygen-octahedral structure of the NbO: Mg precursor.

Design and synthesis of MOFs-derived CuO/g-C3N4 composites with octahedral structure as advanced anode materials for asymmetric supercapacitors with high energy and power densities

In this study, two-component composites consisting of transition metal copper oxide (CuO) and graphite carbon nitride (g-C3N4) were successfully synthesized. Firstly, a typical metal-organic framework (MOF) material, namely CuBTC, was...

Nanosized octahedral LiNi0.5Mn1.5O4 with predominant (111) facet as high performance cathode for Lithium-ion batteries

Nanosized octahedral LiNi0.5Mn1.5O4 with predominant (111) facet has been successfully fabricated using Mn3O4 nanoparticles precursors via a two-step synthesis, which involves a hydrothermal treatment and the subsequent calcination. The physical properties of the Mn3O4 precursor and the resultant LiNi0.5Mn1.5O4 were characterized by XRD (X-ray diffraction), TEM (transmission electron microscopy) and SEM (scanning electron microscopy). The charge-discharge tests show that the resultant LiNi0.5Mn1.5O4 exhibits excellent cyclability and rate capability, which delivers a discharge capacity of about 117 mAh g− 1 after 300 cycles, and maintains 94% of its initial discharge capacity (124.7 mAh g− 1) at 1C, even at a rate of 40C, a specific capacity of 99.2 mAh g− 1 could be still obtained for the O-LNMO. The superior electrochemical performance of the LNMO is mainly attributed to the synergistic effect of the nanosized octahedral structure and exposed (111) facets of the prepared LiNi0.5Mn1.5O4. We found that the nanosized octahedral structure can not only accommodate the lattice stress caused by John-Teller distortion but also provide short paths for Li+ ion transportation in the material. Additionally, the obtained predominant (111) facet is helpful to the formation of protective SEI film on the spinel LiNi0.5Mn1.5O4 electrode.

Enhancing the Activity and Stability of CuO/OMS-2 Catalyst for CO Oxidation at Low Temperature by Modification with Metal Oxides

In this study, mixed oxides of Mn-Cu and Fe-Cu on OMS-2 support having an octahedral structure were synthesized by the refluxing and impregnation methods. The characteristics of the materials were analyzed by XRD, FTIR, SEM, EDX, and H2-TPR. In the CO oxidation test, CuFeOx/OMS-2 had slightly higher catalytic activity but is significantly more stable than CuMnOx/OMS-2 and CuO/OMS-2. Due to its lower reduction temperature in H2-TPR analysis, the Mars-Van-Krevelen mechanism for CuFeOx/OMS-2 (Cu2+–O–Fe3+ ↔ Cu+–□–Fe2+) could take place more energetically than CuO/OMS-2 and CuMnOx/OMS-2 (Cu2+–O2−–Mn4+ ↔ Cu+–□–Mn3+). In addition, the interaction between Fe and Cu in the catalyst could improve the durability of the surface oxides structure in comparison with that between Mn and Cu. With the high specific rate and TOF of 28.6 mmol/h.g and 0.508, respectively, CuFeOx/OMS-2 has a great potential as an effective catalyst for low-temperature oxidation application in CO and possible VOCs removal.

Leap Zagreb Connection Numbers for Some Networks Models

The main object of this study is to determine the exact values of the topological indices which play a vital role in studying chemical information, structure properties like QSAR and QSPR. The first Zagreb index and second Zagreb index are among the most studied topological indices. We now consider analogous graph invariants, based on the second degrees of vertices, called leap Zagreb indices. We compute these indices for Tickysim SpiNNaker model, cyclic octahedral structure, Aztec diamond and extended Aztec diamond.

Crystal structures of a series of bis(acetylacetonato)oxovanadium(IV) complexes containing N-donor pyridyl ligands

Crystal structures for a series of bis(acetylacetonato)oxovanadium(IV) complexes containing N-donor pyridyl ligands are reported, namely, bis(acetylacetonato-κ2 O,O′)oxido(pyridine-κN)vanadium(IV), [V(C5H7O2)2O(C5H5N)], 1, bis(acetylacetonato-κ2 O,O′)oxido(pyridine-4-carbonitrile-κN)vanadium(IV), [V(C5H7O2)2O(C6H4N2)], 2, and bis(acetylacetonato-κ2 O,O′)(4-methoxypyridine-κN)oxidovanadium(IV), [V(C5H7O2)2O(C6H7NO)], 3, Compounds 1–3 have the formulae VO(C5H7O2)2 L, where L = pyridine (1), 4-cyano-pyridine (2), and 4-methoxypyridine (3). Compound 1 was previously reported [Meicheng et al. (1984). Kexue Tongbao, 29, 759–764 and DaSilva, Spiazzi, Bortolotto & Burrow (2007). Acta Crystallogr., E63, m2422] and redetermined here at cryogenic temperatures. Compounds 1 and 2 as pyridine and 4-cyanopyridine adducts, respectively, crystallize as distorted octahedral structures with the oxo and pyridyl ligands trans to one another. A crystallographic twofold axis runs through the O—V—N bonds. Compound 3 containing a 4-methoxypyridine ligand crystallizes as a distorted octahedral structure with the oxo and pyridyl ligands cis to one other, removing the twofold symmetry seen in the other complexes.