A. E. Kokh

A. E. Kokh
Sobolev Institute of Geology and Mineralogy · Crystal Growth lab

About

175
Publications
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1,412
Citations
Citations since 2016
53 Research Items
636 Citations
2016201720182019202020212022020406080100
2016201720182019202020212022020406080100
2016201720182019202020212022020406080100
2016201720182019202020212022020406080100

Publications

Publications (175)
Article
Noncentrosymmetric borates K7MIn2-xYbx(B5O10)3 (M = Ca, Sr, Ba; x=0…2) were synthesized by the solid state reaction and the crystals were successfully grown by the top seeded solution growth method using the K2O-B2O3-MF2 flux. According to Rietveld refinement, the crystal structure belongs to the noncentrosymmetric R32 space group. Also, the octahe...
Conference Paper
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В настоящее время многие исследования в области материаловедения связаны с разработкой более совершенных и экологичных источников света и люминофоров. Часть из этих проектов сфокусированы на боратах из-за их высокой химической, термической и радиационной стабильности, широкой области прозрачности и высокого порога лазерного излучения. Кроме того, б...
Conference Paper
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Сегодняшний мир невозможно представить без высокотехнологичных устройств, для производства которых используется большое количество кристаллов различных соединений. Так, одними из перспективных соединений для оптических применений являются вольфраматы и молибдаты. Молибден и вольфрам входят в шестую группу периодической системы, а также располаг...
Conference Paper
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RSc3(BO3)4, KCaR(BO3)2 and Li3Ba4Sc3B8O22 (R=La-Eu) rare earth borates were obtained by spontaneous crystallization from flux. Thermal, structural and some optical properties (Raman spectra and UV-vis-NIR diffuse reflectance spectra were studied. Second harmonic generation relative KH2PO4 was estimated for noncentrosymmetric scandium borates. The...
Article
NaSrR(BO 3) 2 (R = Ho−Lu, Y, Sc) compounds were obtained for the first time. Their structures exhibit disordered positions of Sr 2+ and Na + atoms while RO6 polyhedra are connected through the BO3 groups. Large distances between R atoms and high transparency in the range of 250−900 nm make them promising for phosphor applications. A pathway to obta...
Article
RBO3 – ScBO3 diagrams (R = La, Pr and Nd) were investigated by the solid state synthesis and DSC methods. In these systems the solid solutions based on RSc3(BO3)4, RBO3 and ScBO3 were identified. The single crystals of RSc3(BO3)4 were grown by spontaneous crystallization method from LiBO2-LiF flux. The borates containing Pr and Nd have typical lumi...
Article
The EuBO3 – ScBO3 system was investigated by solid state synthesis and DSC methods. In this system a new EuSc(BO3)2 compound was found. It crystallizes in R3 ̅ space group with unit cell parameters a=4.8939(1)Å, c=16.2663(5)Å. While another compound in this system EuSc3(BO3)4 has two modifications: low temperature α-C2/c (a=7.687(1) Å, b=9.810(2) Å...
Conference Paper
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At present, many research projects are related to the development of more environmentally friendly light sources and luminophores. These projects have focused on borates due to their high chemical stability, thermal and radiation stability, wide transparency region and high laser threshold. In addition, borate compounds have diverse chemical compos...
Conference Paper
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Минерал бючлиит (K2Ca(CO3)2) кристаллизуется в тригональной пространственной группе R3m с параметрами элементарной ячейки a = 5.4526(12) Å, c = 17.781(8) Å, Z = 3. Структура бючлиита представлена атомами К1+ с девятерной координацией, которые имеют два типа связей K-O, из которых 6 коротких (2.86 Å) и 3 длинных (3.07 Å), тогда как атомы Ca2+ распол...
Article
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A new luminescent material based on complex borate NaBaY(BO3)2 doped with Tb3+ and Eu3+ ions was obtained by high-temperature solid-state synthesis. Using X-ray diffraction analysis it was shown that NaBaY(BO3)2:0.07Tb3+:0.1Eu3+ crystallizes in trigonal system with the space group R-3m and isotypic with the mineral buetschliit K2Ca(CO3)2. The cryst...
Article
The LiBa12(BO3)7F4 crystals doped Nd3+ and Pr3+ were grown from hightemperature solution melts, using the TSSG method. All the samples have the wide absorption band in the visible range of 350-650 nm related to the dichroism, which is typical for other colored “antizeolites”. Strong radiation bands are associated with well known electronic transiti...
Article
Herein we report the growth of new RxLayScz(BO3)4 (x + y+z = 4, R = Sm, Tb) crystals with large second-harmonic generation (SHG) responses. The obtained compounds, grown from eutectic LiBO2-LiF flux by the TSSG method, crystallize in the space group P321 with the cell parameters a = 9.800(15) Å and c = 7.9565(7) Å for Sm0.34La0.68Sc2.98(BO3)4 and a...
Article
Novel KCaR(BO3)2 (R = La, Pr and Nd) compounds have been obtained by solid-state synthesis. Specifically, single crystals of KCaNd(BO3)2 and KCaPr(BO3)2 were grown by using a top seeded solution growth method from the KBO2 flux. These crystal compounds belong to the orthorhombic system, Pbca space group. KCaLa(BO3)2 exhibits high transparency in th...
Article
A new lithium barium scandium borate (Li3Ba4Sc3B8O22) was obtained by solid-state synthesis and grown by spontaneous crystallization. Single-crystal X-ray diffraction analysis showed that it crystallizes in the centrosymmetric space group P-1 with the cell dimensions a = 5.2230(4) Å, b = 8.5609(6) Å, c = 11.4157(8) Å, α = 73.3750(6)°, β = 78.5020(6...
Chapter
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Complex ortohoborates of rare earth metals with the general chemical formula RxLa1−xSc3(BO3)4 (R = Sm, Tb) have been obtained by solid state synthesis and spontaneous crystallization. These crystals belong to the huntite family with the space group R32 and for x = 0.5 have unit cell parameters a = 9.823(6), c = 7.975(3) (SLSB) and a = 9.803(3), c =...
Article
The authors employ methods of spontaneous crystallization on a platinum loop, modified visual polythermal analysis (VPA), solid phase synthesis, differential thermal analysis (DTA), X-ray powder diffraction (XRD) analysis and chemical analyses, in order to study chemical processes and phase formation in the BaB2O4–LiF–Li2O system. In this system th...
Article
This review focuses on the recently discovered new compounds in the MMeR(BO3)2 borate family (where M = alkali metal, Me = alkaline earth metal, and R = rare-earth element), describing their crystal structures and luminescent properties. The basic building block for this structure is the two-layer {R[A(BO3)2]2} package (where A is an alkali metal a...
Article
Non-centrosymmetric borates K 7 CaR 2 (B 5 O 10 ) 3 have been synthesized by solid state reaction and successfully grown by the top seeded solution growth method using K 2 O-B 2 O 3 -CaF 2 flux. IR, Raman, absorption spectra as well as data on melting temperature for the crystals were obtained. Optical properties like UV absorption edge and SHG int...
Article
time. Crystals of the compound melts congruently at 1007 oC, however melt crystallization of high quality crystal is impossible due to phase transition at ~920 oC. The top seeded solution method from Li2WO4-WO3 flux was successfully applied reducing the growth temperature below 900 oC. According to single crystal x-ray measurements, the crystal cor...
Article
Phase equilibria in the ΒaΒ2O4–LiF–NaF section of the quaternary reciprocal system Li, Na, Ba // BO2, F are studied by the solid‐phase synthesis, differential thermal analysis, and visual polythermal analysis techniques. It is shown that this system can be used for the growth of bulk β‐ΒaΒ2O4 crystals. Phase equilibria in the ΒaΒ2O4–LiF–NaF section...
Article
A new class of the so-called ‘anti-zeolite’ fluoride borates has been recently discovered. These fluoride borates are built of porous framework made of [Ba12(BO3)6]6+ building blocks (hence called as ‘anti’-zeolitic framework). The framework bound spacious cages and channels where highly mobile ‘guest’ anions are situated, e.g. (BO3)3-, (F4)4-, (F2...
Article
Non-centrosymmetric borates K7CaY2(B5O10)3 have been synthesized by solid state reaction and the crystals were successfully grown by the top seeded solution growth method using K2O-B2O3-CaF2 flux. According to the single X-ray diffraction, the structure belongs to the R32 space group with lattice parameters a = 13.2516(2) Å and c = 14.9679(3) Å. IR...
Article
Crystals of the MnxBa12(BO3)8-2xF8xphase were grown from a high-temperature solution. This new fluoride borate is built of positively charged [Ba12(BO3)6]6+blocks, the so-called "anti-zeolite" pattern. Using X-ray single-crystal diffraction, the bulk atomic arrangement in the centrosymmetric tetragonal unit cell in I4/mcm could be elucidated. Cryst...
Article
The anisotropy of optical properties of nonlinear lithium borate (LBO) crystals in the range of 0.2–2 THz is investigated by time-domain THz spectroscopy at room temperature and at T = 81 K. It is shown that the birefringence dramatically decreases upon cooling, as a result of which phase-matching conditions cannot be implemented. At the same time,...
Article
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The anisotropy of optical properties of high quality beta barium borate crystal (β-BaB2O4, β-BBO) was studied in the main transparency window by using classic spectroscopic methods and in the range of 0.2 – 2 THz by using THz time-domain spectroscopy. β-BBO crystals were grown by the top-seeded solution technique in a highly resistive furnace with...
Article
Full-text available
Lithium triborate LiB3O5 (LBO) crystals are widely used for frequency conversion of the near-IR lasers within main transparency windows. Their optical properties at these wavelengths are well studied. However, very little work has been published on the properties in the terahertz (THz) range. There was a lack of data on the refractive indices, the...
Article
The search for compounds with the formula composition KBaR(BO3)2 has been performed by solid-phase synthesis and differential thermal analysis. The compounds synthesized in this series are KBaPr(BO3)2 and KBaNd(BO3)2, which are isostructural to KBaY(BO3)2, are isotypical to butschliite K2Ca(CO3)2, and crystallize in a trigonal system with space gro...
Article
The first systematic study of the BaO–B2O3 system and barium orthoborate Ba3B2O6 (3BaO·B2O3) was reported in 1949. Thereafter, the system was repeatedly refined but the structure of Ba3B2O6 compound has not been adequately studied yet. In our study we have, for the first time, obtained the crystalline samples of Ba3B2O6. The solved structure (Pbam,...
Article
Three new rare-earth based orthoborates KSrR(BO3)2, with R = Y, Tb, Yb were synthesized by solid-state reaction method. Single crystals of KSrR(BO3)2 were obtained by spontaneous crystallization using selected flux. Single-crystal X-ray diffraction measurements reveal that KSrY(BO3)2 crystallizes in monoclinic space group P21/m with cell parameters...
Article
Two new rare-earth orthoborates KBaPr(BO3)2 and KBaNd(BO3)2 were synthesized using a two-step solid-state reaction, both of them are stable in the temperature range 850-1000°C. KBaNd(BO3)2 and KBaPr(BO3)2 show incongruent melting at 1019°S and 1005°S, respectively. Prepared compounds crystallize in the trigonal system with space group R3-m with cel...
Article
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Bulk crystals of new huntite type borates were grown by TSSG method using eutectic LiBO2–LiF as a flux. Chemical composition, X-ray diffraction, optical absorption and fluorescence spectra of the grown samples were studied.
Article
Studied LixNa1-xBa12(BO3)7F4 (P42bc) solid solution belongs to the new class of "antizeolite" borates with [Ba12(BO3)6](6+) cation pattern, which contains channels filled by anionic clusters. Optical-quality crystals were grown from the compositions with different sodium-lithium ratio. The results of Rietveld refinement based on powder data demonst...
Article
THz optical properties of lithium borate (LBO) crystals were measured using time-domain spectroscopy (TDS). The LBO crystal samples were of high optical quality and were cut and polished along the 〈100〉, 〈010〉 and 〈001〉 axes. Two independent measurements were performed in order to confirm the reproducibility and consistency of results. The contradi...
Article
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In order to find the optimum solvent for the growth of nonlinear optical β-BaB 2 O 4 crystals, the phase relationships in the ternary reciprocal system Li, Ba // BO 2 , F have been studied using solid state synthesis, differential thermal analysis and X-ray powder diffraction. Isothermal and polythermal sections of the system Li, Ba // BO 2 , F are...
Cover Page
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Tetragonal [Ba12(BO3)6]6+ cation pattern of the Ba3(BO3)2 structure with channels along c axis and fragment of a channel. Ba, O, and B atoms are shown in blue, red and black, respectively. For disordered (BO3)3– groups inside the channel, occupancy of atoms is shown by partial filling. The drawing was prepared using VESTA software (Momma, K., and F...
Article
Comparative model analysis of the possibilities of down-conversion into the terahertz (THz) frequency range of radiation of all-solid-state femtosecond Ti:Sapphire laser systems and hybrid systems based on the same type lasers and equipped with amplifiers on XeF(C-A) and XeCl(C-A) molecules of excimer gases with harmonic generators on nonlinear LBO...
Article
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Six new rare-earth orthoborates NaBaR(BO3)2, with R = Tb, Dy, Ho, Er, Tm, Lu were synthesized using a multiple-step solid-state reaction. These new orthoborates continue the previously described isostructural lines of three-cation orthoborates NaBaR(BO3)2, by R = Sc, Y, Yb. The structure of synthesized solid compounds is isotypic with the mineral e...
Article
The bulk crystals of LiBa12(BO3)7F4 were obtained from two flux compositions by the top seeded solution growth method. Crystals grown from BaCO3:BaF2:H3BO3:Li2CO3 = 3:3:3:1 charge were found to have a distinct linear dichroism effect at 0.35–0.65 and around 0.73 μm. This suggests application of the material in the production of polarizing filters a...
Article
A novel compound containing three cation alkali, alkali earth, rare earth orthoborate KBaSm(BO3)2 was synthesized by using two-step solid-state method. Results of powder X-ray diffraction analysis (XRD) and FTIR spectroscopy showed that this compound is isostructural with known compounds KBaY(BO3)2 [1] and KBaTbB2O6 [2] and refers to trigonal cryst...
Article
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In this article, we report how the growth method used for barium beta-borate β-BaB2O4 (BBO) impacts its high power second harmonic generation properties in the deep-UV. We compared a BBO crystal grown by flux (Top Seeded Solution Growth or TSSG) and a BBO crystal grown by the Czochralski (CZ) method. We first characterized their transparency proper...
Article
High quality lithium borate (LBO) samples cut along (1 0 0), (0 1 0) and (0 0 1) axes were studied by terahertz time-domain spectroscopy (THz TDS) between 0.2–3 THz. It was found that in the direction of crystallographic axis X the optical absorption coefficient is the lowest amongst all known anisotropic nonlinear crystals, and that birefringence...
Article
Using BaCO3, H3BO3, and LiF as starting materials a phase diagram of the title system is established by solid state synthesis (Pt crucible, 700 °C, 3—5 d), differential thermal analysis, modified visual polythermal analysis, and XRD.
Article
Solid state synthesis, differencial thermal analysis and visual polythermal analysis were applied to study the phase equilibria in BaB2O4-LiF system. A phase diagram BaB2O4-LiF has been plotted for the first time. The system has proved applicable for growing β-BaB2O4 bulk crystals. Barium borate β-BaB2O4 (BBO) single crystals of low-temperature mod...
Article
GaSe1−xSx (x = 0, 0.01, 0.05, 0.13, 0.22, 0.29, 0.44) crystals were grown by modified vertical Bridgman method that provided (0001) crystal plane orientation perpendicular to growth axis. Absorption coefficient is minimal (decreased by up to 3 times) in the THz range at the optimal S-doping of 3 weight % (x = 0.13). Increased S content causes the a...
Article
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Chemical processes and phase equilibria in BaB2O4-MF (M = Li, Na, or K) systems were studied. Liquidus curves for these sections were constructed. The primary crystallization field of the low-temperature barium borate phase (beta-BaB2O4) for the BaB2O4-(LiF)(2) system was found to lie in the range 65-50 mol % BaB2O4; for the BaB2O4-NaF system, in t...
Article
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Solubility curves are plotted and optimal solvents for growing lithium triborate (LiB3O5) single crystals are determined. The crystallization range of this compound in the Li2O-B2O3-MoO3 system is refined. The molybdenum content in the crystals grown is analyzed.
Article
Methods of spontaneous crystallization on a platinum loop, modified VPA method, solid phase synthesis. X-ray powder diffraction analysis and chemical analyses were used to study phase formation in the Li, Ba//BO2, F ternary reciprocal system and the base of the BaO-B2O3-Li2O prism of quaternary reciprocal system Ba, B, Li//O, F. In these systems th...
Article
The conceptual design of ultra-high intensity multichannel laser system with coherent beam combining is presented. Design of 1 PW and 10 PW laser channels with pulse repetition rate of 10 Hz based on optical parametric amplification in LBO crystals is considered. Requirements of the most critical pulse parameters for high efficiency coherent beam c...
Article
A growth station for growing paratelluthe single crystals is presented. Modification of Czochralski furnace consists of nonuniform heating of melt by remaining low temperature gradients near the front of crystallization. It is supposed that local overheating of the lower parts of the melt breaks particle associates in the melt. This assumption is c...
Article
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We have observed unusual asymmetrical refractive index change as a result of femtosecond laser inscription in a crystal without center of inversion. Profile of the refractive index change exhibits sign turn within the domain of femtosecond pulse exposure.
Conference Paper
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LYSB, NdYSB, and PrYSB borate crystals show interesting optical non linear properties, optical quality for theses three crystal is studied then we report absorption spectra, and second harmonic generation coefficients deff for type I phase matching.
Article
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A comprehensive study of the BaF2-Ba-3(BO3)(2) phase diagram has revealed a significant difference between the two intermediate phases Ba-5(BO3)(3)F and Ba-7(BO3)(4-y)F2+3y. The latter exhibited (BO3)(3-) <-> 3F(-) anionic substitution which, unusually, strongly influences the solidus temperature. A comparison of the Ba-5(BO3)(3)F and Ba-7(BO3)(4-y...
Article
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Les cristaux de borate LYSB, NdYSB et PrYSB présentent des propriétés optique-non linéaires intéressantes pour la conversion de fréquence dans le visible, la substitution du La par le Nd ou le Pr permet de stabiliser la croissance et d'obtenir des auto-doubleurs de fréquence. Des premières études de spectroscopie d'absorption, de spectroscopie Rama...
Article
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The solubility of rare-earth orthoborates and LaSc3(BO3)4 in LiBO2-LiF solvents has been studied. Spontaneous crystals have been grown and the solvent used has been shown to be attractive for the growth of bulk crystals at t ≤ 1000°C. The α- and γ-phases of LaSc3(BO3)4 have been shown to be identical.
Article
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An optical quality GaSe:InS single crystal has been grown by modified Bridgman technique using nonstationary temperature distribution for effective melt mixing. The phase composition of the crystal has been verified with XRD and TEM. The chemical composition variation along the crystal has been evaluated with electron probe microanalysis (EPMA), at...
Article
Modified GaSe single crystal was grown from the melt with charge composition GaSe + 10 mass% of AgGaSe2. Lattice structure, visible to mid-IR and further THz range optical properties, as well as Raman spectra were studied in details. The grown crystal was identified as epsilon-GaSe:Ag (0.04 mass%). This silver content in GaSe has resulted in 6% dec...
Article
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A search for compounds of the NaBaR(BO3)2 composition (where R = La3+, Nd3+, Gd3+, or Yb3+) is performed by solid state synthesis and spontaneous crystallization. A new compound, NaBaYb(BO3)2, is found in this series. It crystallizes in space group $R\bar 3$ and belongs to the family of sublayer complex orthoborates with isolated BO3 groups NaBaR...