T. B. Bekker
Russian Academy of Sciences
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Featured researches published by T. B. Bekker.
Crystallography Reports | 2009
A. E. Kokh; N. G. Kononova; T. B. Bekker; P. P. Fedorov; E. A. Nigmatulina; A. G. Ivanova
The phase formation in the BaB2O4-NaF cut has been investigated by the methods of solid-phase synthesis, visual polythermal analysis, and spontaneous crystallization on a platinum loop. A range of primary crystallization of the new compound Ba2Na3[B3O6]2F (hexagonal system, P63/m, a = 7.346(1) Å, c = 12.636(2) Å) is revealed in this cut, which is used to grow single crystals of low-temperature barium borate modification β-BaB2O4.
High Pressure Research | 2013
Sergey V. Rashchenko; Anna Yu. Likhacheva; T. B. Bekker
A new simplified synthesis of monocrystalline chips of SrB4O7: Sm2+ pressure calibrant, well-suited for the diamond anvil cell (DAC) powder diffraction experiments, is proposed. It consists of ordinary solid-state synthesis of fine-grained SrB4O7: Sm2+ and subsequent annealing near melting temperature. The obtained material was characterized and tested in HP-HT DAC experiment.
Journal of Applied Crystallography | 2013
Sergey V. Rashchenko; T. B. Bekker; V. V. Bakakin; Yurii V. Seryotkin; Alexander E. Kokh; Peter Gille; Arthur I. Popov; P. P. Fedorov
A comprehensive study of the BaF2-Ba3(BO 3)2 phase diagram has revealed a significant difference between the two intermediate phases Ba5(BO3)3F and Ba 7(BO3)4-y F2+3y. The latter exhibited (BO 3)3- ↔ 3F- anionic substitution which, unusually, strongly influences the solidus temperature. A comparison of the Ba5(BO3)3F and Ba7(BO3)4-y F2+3y crystal structures, along with consideration of other compounds demonstrating (BO3)3- ↔ 3F- isomorphism, allows for the disclosure of the mechanism of (BO3)3- ↔ 3F - heterovalent anionic substitution in fluoride borates via [(BO 3)F]4- tetrahedral groups being replaced by four fluoride anions. No exception to this mechanism has been discovered among all known phases with (BO3)3- ↔ 3F- substitution.
CrystEngComm | 2012
T. B. Bekker; Sergey V. Rashchenko; V. V. Bakakin; Yu. V. Seryotkin; P. P. Fedorov; A. E. Kokh; S. Yu. Stonoga
Detailed study of the BaB2O4–BaF2–BaO system resulted in the discovery of the new Ba7(BO3)4−xF2+3x solid solution belonging to the BaF2–Ba3(BO3)2 section. The distinguishing feature of the crystal structure of Ba7(BO3)4−xF2+3x phase is its extensive (BO3)3− ↔ 3F− anionic isomorphic substitution, confirmed by X-ray diffraction study of Ba7(BO3)3.51F3.47 (x = 0.49) single crystals (space group P63; a = 11.18241(11) A, c = 7.23720(8) A). The area of homogeneity for Ba7(BO3)4−xF2+3x solid solution spans between Ba7(BO3)3.35F3.95 and Ba7(BO3)3.79F2.63 compositions (0.21 < x < 0.65). Also, a new orthorhombic phase with a tentative composition of Ba5(BO3)3F has been identified in XRD powder patterns and indexed with cell parameters a = 7.605 A, b = 14.843 A and c = 10.291 A.
Crystallography Reports | 2010
T. B. Bekker; N. G. Kononova; A. E. Kokh; S. V. Kuznetsov; P. P. Fedorov
The phase equilibria in the Ba2Na3[B3O6]2F-BaF2 section, which belongs to the ternary mutual Ba, Na//BO2,F system, have been studied by the methods of solid-phase synthesis, visual polythermal analysis, and differential-thermal analyses. It is shown that this section can be used to grow bulk Ba2Na3[B3O6]2F crystals.
Crystallography Reports | 2003
N. G. Kononova; A. E. Kokh; T. B. Bekker; N. G. Furmanova; B. A. Maksimov; V. N. Molchanov; P. P. Fedorov
Crystals of NaBaBO3 were grown by spontaneous crystallization on a platinum loop from the BaO-B2O3-Na2O system using the flux technique. The crystals have a highly disordered block structure. X-ray diffraction study λMoKα, 518 independent reflections, R = 0.0272) demonstrated that the structure of these crystals is identical with that established previously by other researchers for a sample prepared by cooling a stoichiometric melt.
CrystEngComm | 2011
T. B. Bekker; Alexander E. Kokh; P. P. Fedorov
The phase formation in the BaB2O4–BaF2 system has been studied. According to the results obtained, the BaB2O4–BaF2 system is quasi binary with the eutectic at 760 °C, 41 mol% of BaB2O4, and 59 mol% of BaF2. The fast pyrohydrolysis of BaF2 in air causes the gradual transformation of the BaB2O4–BaF2 system into the BaB2O4–BaO system and results in the co-crystallization of BaB2O4 and Ba5B4O11 phases, making the growth of large high-quality β-BaB2O4 crystals in air impossible.
Crystallography Reports | 2005
A. E. Kokh; N. G. Kononova; T. B. Bekker; V. A. Vlezko; P. V. Mokrushnikov; V. N. Popov
It is suggested to change the symmetry and rotation of thermal field as a method of contact-free control of the heat and mass transfer in crystal growth. By the example of growth of the low-temperature barium borate (β-BaB2O4) phase, a technically important crystal with nonlinear-optical properties, it is shown that the use of the suggested method allows one to grow larger crystals of a higher quality.
Journal of Structural Chemistry | 2015
Sergey V. Rashchenko; V. V. Bakakin; Svetlana G. Kozlova; T. B. Bekker; P. P. Fedorov
In the work the structures of fluoride borates demonstrating the substitution with the stoichiometry (BO3)3− ↔ 3F− are analyzed and the specific role of tetrahedral anionic [X4]4− groups is revealed in this substitution. The possibility of the F-F interaction in [F4]4− groups uncharacteristic of ionic crystals is confirmed by ab initio quantum chemical simulation of the crystal structure of Ba4−xSr3+x(BO3)4−yF2+3y.
Inorganic Materials | 2010
A. E. Kokh; N. G. Kononova; T. B. Bekker; P. P. Fedorov; S. V. Kuznetsov
Phase equilibria in the BaB2O4-NaF system have been studied by a modified visual thermal analysis technique and differential thermal analysis. The phase diagram obtained in this study differs drastically from that reported previously. The system is shown to contain the primary crystallization field of a new compound, Ba2Na3[B3O6]2F.