scholarly journals HYDROGEN BONDS IN LITHIUM NIOBATE CRYSTALS OF DIFFERENT COMPOSITION

2021 ◽  
pp. 376-382
Author(s):  
Николай Васильевич Сидоров ◽  
Наталья Александровна Теплякова ◽  
Михаил Николаевич Палатников
Keyword(s):  
Hydrogen Bonds ◽  
Lithium Niobate ◽  
Stoichiometric Composition ◽  
Cation Sublattice ◽  
Ionic Radii ◽  
Oh Groups ◽  
Dopant Incorporation ◽  
Wide Range ◽  
Crystal Properties ◽  
Lithium Niobate Crystals

Методом ИК-спектроскопии в области валентных колебаний OH - групп выполнен анализ комплексных дефектов, обусловленных наличием в структуре кристалла водородных связей, в номинально чистых кристаллах ниобата лития конгруэнтного и стехиометрического состава с разным отношением Li / Nb, а также в кристаллах LiNbO: Zn(0,04 - 6,5 мол.% ZnO), легированных цинком в широком диапазоне концентраций, полученным по технологии прямого легирования расплава. Выявлено влияние легирующих примесей на концентрацию OH - групп, вид и локализацию комплексных дефектов в структуре кристалла. Показано, что изменение количества позиций атомов водорода в структуре кристалла LiNbO позволяет с достаточной точностью судить о соответствии его состава стехиометрическому или конгруэнтному составу. Для легированных кристаллов LiNbO : Zn(0,04 - 6,5 мол.% ZnO) получены данные, свидетельствующие об изменении при прохождении концентрационных порогов характера комплексообразования OH - групп с точечными дефектами катионной подрешетки. При этом, вследствие изменения механизма вхождения легирующего катиона в структуру кардинально изменяются свойства кристалла. Вклад в различие частот (и, соответственно, в значение квазиупругих постоянных связей OH -) в спектре конгруэнтного кристалла и легированных кристаллов может вносить также различие электроотрицательностей и ионных радиусов основных и легирующих катионов. An analysis of complex defects was carried out by IR-spectroscopy method in the area of OH - groups stretching vibrations. The defects are caused by hydrogen bonds present in the structure of nominally pure congruent lithium niobate crystals, crystals of stoichiometric composition with a different Li / Nb ratio, as well as in LiNbO: Zn(0,04 - 6,5 мол.% ZnO) crystals doped in a wide range of concentrations due to direct doping of the melt method. Dopants were determined to influence OH - groups concentration, type and localization of complex defects in the crystals structure. A change in the amount of hydrogen sites in the LiNbO crystals structure was shown to evaluate the composition either stoichiometric or congruent. The character of OH - groups complexing with cation sublattice point defects was shown to change when doped crystals LiNbO: Zn(0,04 - 6,5 мол.% ZnO) trespass concentration thresholds. Dopant incorporation mechanism changes at this drastically, thus crystal properties also change quite sharply. Frequencies (as well as quasi-elastic constants of OH - bonds) change in congruent and doped crystals due to a difference in electronegativities and ionic radii of the main and dopant cations.

scholarly journals CALCULATION OF THE POINT DEFECT CONCENTRATION OF THE CATION SUBLATTICE AND HYDROXYL GROUPS IN LITHIUM NIOBATE CRYSTALS OF DIFFERENT COMPOSITION

2020 ◽  
pp. 200-205
Author(s):  
Наталья Александровна Теплякова ◽  
Николай Васильевич Сидоров ◽  
Михаил Николаевич Палатников
Keyword(s):  
Phase Diagram ◽  
Lithium Niobate ◽  
Point Defects ◽  
Cation Sublattice ◽  
Hydroxyl Groups ◽  
Ir Absorption ◽  
Oh Groups ◽  
Ir Absorption Spectra ◽  
Stretching Vibrations ◽  
Lithium Niobate Crystals

Исследованы ИК-спектры поглощения в области валентных колебаний OH - групп кристаллов ниобата лития стехиометрического и конгруэнтного составов. Рассчитана концентрация OH - групп, отношение Li / Nb, а также концентрация точечных дефектов Nb и V. Результаты расчетов совпадают с литературными данными и подтверждаются фазовой диаграммой ниобата лития. Показано, что увеличение количества свободных протонов (вносящих вклад в проводимость) может обуславливать более высокие электропроводность, скорость термической фиксации голограмм и снижение эффекта фоторефракции. The IR absorption spectra in the region of stretching vibrations of OH - groups of lithium niobate crystals of stoichiometric and congruent compositions are studied. The results of calculations of the OH - groups concentration, the Li / Nb ratio and the concentration of point defects Nb and V coincide with the literature data. The phase diagram of lithium niobate confirms these results. It is shown that an increase in the number of free protons that contribute to conductivity can lead to reducing the optical damage and higher electrical conductivity and the rate of thermal fixation of holograms.

scholarly journals Photoluminescence and features of the defective structure of nominally pure lithium niobate single crystals.

2020 ◽  
Vol 11 (3-2020) ◽  
pp. 173-177
Author(s):  
M. V. Smirnov ◽  
◽  
N. V. Sidorov ◽  
N. A. Teplyakova ◽  
V. B. Pikulev ◽  
...  
Keyword(s):  
Lithium Niobate ◽  
Stoichiometric Composition ◽  
Wavelength Region ◽  
Fundamental Absorption Edge ◽  
Photoluminescence Intensity ◽  
Cationic Sublattice ◽  
Short Wavelength Region ◽  
Defective Structure ◽  
Oh Groups ◽  
Lithium Niobate Crystals

The photoluminescence intensity in lithium niobate crystals close to the stoichiometric composition being lower than in a congruent crystal was established. The increase of Li / Nb ratio leads to shifting the photoluminescence bands to the short-wavelength region of the spectrum and changing the fundamental absorption edge of the crystals under study. It was shown that, in addition to point defects in the cationic sublattice, complex defects due to the presence of OH groups and compensation defects (VLi / VNb) in the structure can also contribute to photoluminescence.

scholarly journals COMPARATIVE ANALYSIS OF THE INFLUENCE OF DOPING IONS OF YTTRIUM AND BORON FORMATION OF DEFECTS IN LITHIUM NIOBATE CRYSTALS

2021 ◽  
pp. 411-420
Author(s):  
Ольга Ростиславна Стародуб ◽  
Вячеслав Михайлович Воскресенский ◽  
Николай Васильевич Сидоров ◽  
Михаил Николаевич Палатников
Keyword(s):  
Comparative Analysis ◽  
Lithium Niobate ◽  
Nonlinear Optical ◽  
Photorefractive Effect ◽  
Ionic Radii ◽  
Wide Range ◽  
Impurity Ions ◽  
Unit Cells ◽  
Impurity Ion ◽  
Lithium Niobate Crystals

Кристалл ниобата лития, являющийся широко используемым и весьма востребованным в настоящее время нелинейно-оптическим материалом, примечателен своей способностью к варьирования широкого спектра сегнетоэлектрических и нелинейно-оптических характеристик в зависимости от типа и концентрации примесного иона, а также от соотношения Li / Nb . На основе разработанного нами подхода к моделированию кластеров в кристалле ниобата лития, в котором рост кластера идёт не элементарными ячейками, а кислородными октаэдрами, проведён сравнительный анализ особенностей внедрения в кристалл примесных ионов иттрия и бора с одинаковым зарядом +3 . Показано, что встраивание, вследствие различного ионного радиуса, идёт по двум механизмам: если для металла иттрия действует обычный механизм, когда примесной ион локализуется внутри кислородного октаэдра, то ион неметаллического элемента бора встраивается в тетраэдрические пустоты структуры, а именно в кислородные плоскости, образующие октаэдр. При этом влияние данных примесных ионов на одну из важнейших характеристик ниобата лития оказывается диаметрально противоположным: иттрий усиливает фоторефрактивный эффект, бор -понижает, что необходимо учитывать при направлении целевого использования кристаллов ниобата лития. Lithium niobate crystals, which are a widely used and highly demanded as nonlinear optical material, are remarkable for their ability to vary a wide range of ferroelectric and nonlinear optical characteristics depending on the type and concentration of the impurity ion, as well as on the Li / Nb ratio. Based on our approach to modeling clusters in the lithium niobate crystal, in which the cluster grows not by unit cells, but by oxygen octahedra, we have carried out a comparative analysis of the features of the incorporation of impurity ions of yttrium and boron with the same charge +3 into the crystal. It is shown that due to the different ionic radii the incorporation proceeds by to two mechanisms. If for yttrium the usual mechanism operates, when the impurity ion is localized inside the oxygen octahedron. The ion of boron, i.e. a nonmetallic element, is incorporated into the tetrahedral voids of the structure, namely, into the oxygen planes forming the octahedron. In this case, the influence of these impurity ions on one of the most important characteristics of lithium niobate turns out to be diametrically opposite: yttrium enhances the photorefractive effect, boron decreases it, which must be taken into account in the direction of targeted use of lithium niobate crystals.

Photoluminescence and Features of the Defective Structure of Nominally Pure Lithium Niobate Crystals

2020 ◽  
Vol 312 ◽  
pp. 121-127
Author(s):  
Maxim Smirnov ◽  
Nikolay V. Sidorov ◽  
Natalya A. Teplyakova ◽  
Mikhail Palatnikov ◽  
Alexander Vjacheslavovich Syuy
Keyword(s):  
Lithium Niobate ◽  
Stoichiometric Composition ◽  
Wavelength Region ◽  
Fundamental Absorption Edge ◽  
Photoluminescence Intensity ◽  
Cationic Sublattice ◽  
Short Wavelength Region ◽  
Defective Structure ◽  
Oh Groups ◽  
Lithium Niobate Crystals

The photoluminescence intensity in lithium niobate crystals close to the stoichiometric composition is lower than in a congruent crystal was established. An increase in the Li / Nb ratio leads to a shift in the photoluminescence bands to the short-wavelength region of the spectrum and a change in the fundamental absorption edge of the crystals under study. It was shown that, in addition to point defects in the cationic sublattice, complex defects due to the presence of OH groups in the structure can also contribute to photoluminescence.

scholarly journals Boron Influence on Defect Structure and Properties of Lithium Niobate Crystals

Crystals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 458
Author(s):  
Nikolay V. Sidorov ◽  
Natalia A. Teplyakova ◽  
Olga V. Makarova ◽  
Mikhail N. Palatnikov ◽  
Roman A. Titov ◽  
...  
Keyword(s):  
Lithium Niobate ◽  
Defect Structure ◽  
Photorefractive Effect ◽  
Ferroelectric Properties ◽  
High Concentration ◽  
Oh Groups ◽  
Boron Doped ◽  
Compositional Uniformity ◽  
Boron Dopant ◽  
Lithium Niobate Crystals

Defect structure of nominally pure lithium niobate crystals grown from a boron doped charge have been studied by Raman and optical spectroscopy, laser conoscopy, and photoinduced light scattering. An influence of boron dopant on optical uniformity, photoelectrical fields values, and band gap have been also studied by these methods in LiNbO3 crystals. Despite a high concentration of boron in the charge (up to 2 mol%), content in the crystal does not exceed 10−4 wt%. We have calculated that boron incorporates only into tetrahedral voids of crystal structure as a part of groups [BO3]3−, which changes O–O bonds lengths in O6 octahedra. At this oxygen–metal clusters MeO6 (Me: Li, Nb) change their polarizability. The clusters determine optically nonlinear and ferroelectric properties of a crystal. Chemical interactions in the system Li2O–Nb2O5–B2O3 have been considered. Boron, being an active element, structures lithium niobate melt, which significantly influences defect structure and physical properties of a crystal grown from such a melt. At the same time, amount of defects NbLi and concentration of OH groups in LiNbO3:B is close to that in stoichiometric crystals; photorefractive effect, optical, and compositional uniformity on the contrary is higher.

Structural Features of Nominally Pure Lithium Niobate Crystals Grown from Boron-Doped Charge

2020 ◽  
Vol 312 ◽  
pp. 128-133
Author(s):  
Nikolay Sidorov ◽  
Roman Titov ◽  
Natalya A. Teplyakova ◽  
Mikhail Palatnikov ◽  
Alexander Vjacheslavovich Syuy
Keyword(s):  
Crystal Structure ◽  
Lithium Niobate ◽  
Single Crystals ◽  
Czochralski Method ◽  
Structural Features ◽  
Structural Defects ◽  
Cation Sublattice ◽  
Structural Units ◽  
Boron Doped ◽  
Lithium Niobate Crystals

The features of the structure of single crystals LiNbO3:B3+ (0.12 and 0.18 wt %) grown by the Czochralski method from the mixture of different genesis were studied. It was found that boron is able to incorporate into the crystal structure of lithium niobate in a trace amounts (~ 10–4–10–5 wt %), decreasing the concentration of structural defects NbLi. Thus, ordering of structural units of the cation sublattice of lithium niobate crystals grown from a congruent composition melt approach in that of stoichiometric crystals.

scholarly journals T-junction droplet generator realised in lithium niobate crystals by laser ablation

2014 ◽  
Vol 1 (1) ◽  
Author(s):  
G. Pozza ◽  
S. Kroesen ◽  
G. Bettella ◽  
A. Zaltron ◽  
M. Esseling ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Lithium Niobate ◽  
Laser Pulse ◽  
Femtosecond Laser ◽  
Droplet Generator ◽  
Wide Range ◽  
Junction Geometry ◽  
Fluidic Circuits ◽  
Pulse Energies ◽  
Lithium Niobate Crystals

AbstractA femtosecond laser at 800 nm was used to create micro-fluidic circuits on lithium niobate (LiNbO3) substrates by means of laser ablation, using different scanning velocities (100-500 μm/s) and laser pulse energies (1-20 μJ). The T-junction geometry was exploited to create on y-cut LiNbO3 crystals a droplet generator, whose microfluidic performance was characterized in a wide range of droplet generation frequencies, from few Hz to about 1 kHz.

scholarly journals Исследование структурного совершенства монокристаллов ниобата лития разного состава и генезиса методом ИК спектроскопии в области валентных колебаний водородных связей

2022 ◽  
Vol 130 (1) ◽  
pp. 160
Author(s):  
Л.А. Бобрева ◽  
Н.В. Сидоров ◽  
Н.А. Теплякова ◽  
М.Н. Палатников ◽  
С.А. Климин ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Hydrogen Atom ◽  
Point Defects ◽  
Sufficient Accuracy ◽  
Linbo3 Crystal ◽  
Cationic Sublattice ◽  
Ionic Radii ◽  
Oh Groups ◽  
A Charge ◽  
Lithium Niobate Crystals

We have analyzed complex defects due to the presence of hydrogen bonds in the crystal structure in nominally pure lithium niobate crystals with different Li/Nb ratio, in crystals alloyed with magnesium and zinc in a wide concentration range (LiNbO3 : Mg (0.19-5.91 mol.% MgO) and LiNbO3 : Zn (0.04-6.5 mol. % ZnO)) and in the double-alloyed crystals (LiNbO3 : Y(0.24) : Mg(0.63 wt. %) and LiNbO3 : Gd (0.25) : Mg(0.75 wt. %)), obtained by technology of direct melt alloying, and also in the double-alloyed crystal (LiNbO3 : Mg(5. 05 mol.% MgO) : Fe(0.009 mol.% Fe2O3)) grown from a charge synthesized using the technology of homogeneous alloying with magnesium and iron Nb2O5. We revealed the influence of doping impurities on the concentration of OH-groups, the type and localization of complex defects in the crystal structure. The change in the number of hydrogen atom positions in the structure of the LiNbO3 crystal allow us to judge with sufficient accuracy whether the crystal composition is stoichiometric or congruent. For doped crystals of different compositions data were obtained testifying to changes in the character of complexation of OH-groups with point defects of the cationic sublattice with formation of defects: MеLi-OH-, MеLi-MеNb-OН. A change in the mechanism of entry of the dopant cation into the structure dramatically affects the change in the properties of the crystal.The difference in the frequencies (and, correspondingly, in the values of the quasi-elastic constants of the O-H bonds) in the spectrum of a congruent crystal and doped crystals can also be contributed by differences in the electronegativity and ionic radii of the principal and doping cations.

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