N. G. Kononova

An investigation of the growth of β-BaB2O4 crystals in the BaB2O4-NaF system and new fluoroborate Ba2Na3[B3O6]2F

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.

Growth and non-linear optical properties of lithium triborate crystals

The Li 2 O-B 2 O 3 -MoO 3 ternary system was investigated to determine the region of growth of lithium triborate Li 2 O.3B 2 O 3 (LBO) crystals with good optical properties. The top-seeded solution growth method, the method of spontaneous crystallisation and solid-state reactions were used in this investigation. The phases were defined by the method of X-ray power diffraction. The data obtained in these experiments made it possible to choose the region of compositions of solutions in the Li 2 O-B 2 O 3 -MoO 3 system for the successful growth of LBO single crystals. LBO single crystals, up to 100 x 82 x 45 mm 3 in size and 290 g in weight, were grown free of cracks, bubbles and inclusions. These single crystals were of high optical quality: wavefront distortion (fringe per mm for λ = 0.633 μm) was lower than 1/150, absorption losses (0.25 μm < λ < 2.5 μm) in the resultant LBO single crystals were lower than 0.005 cm -1 , and the damage threshold at = 1.06 μm, τ = 10 ns in the LBO single crystals was more than 10.0 GW/cm 2 . High performance non-linear optical elements of various optical orientations, up to 20 x 20 x 20 mm 3 in size, were fabricated on our LBO crystals.

Nanoporous crystalline material CsLiB6O10

CsLiB6O10 crystals up to 60 × 40 × 20 mm in dimensions were prepared by top-seeded solution growth, and their interaction with water was studied. The crystals were found to be subject to hydration followed by hydrolysis, during which water leaches Cs from the structural channels to yield Cs2B10O16 · 8H2O as the final product. The channel dimensions are not large enough to incorporate ethanol or acetone molecules.

Crystal structure of the new barium borate Ba5(BO3)2(B2O5)

The crystal structure of the new barium borate Ba5(BO3)2(B2O5) is established (R = 0.0436). Single crystals were grown by spontaneous crystallization in the BaO-B2O3-Na2O system using the flux method. This compound crystallizes in the orthorhombic system, sp. gr. P212121; the unit-cell parameters are a = 9.590(2) Å, b = 16.659(3) Å, c = 22.919(6) Å, and Z = 12. The structure consists of coordination polyhedra of barium cations and the anionic groups [BO3] (planar triangles) and [B2O5] (vertex-sharing double [BO3] triangles), which form a pseudohexagonal framework. Melting of barium borate occurs by a peritectic reaction at 1170 ± 10°C.

Incorporation of alkali impurities into single crystals of barium metaborate β-BaB2O4

The impurities in single crystals of the low-temperature β modification of BaB2O4 grown from flux in the BaB2O4-Na2O system have been studied. The β-BaB2O4 compound was examined by X-ray powder diffraction analysis. The appearance of scattering centers in the crystals correlates with the high content of sodium whose critical concentration is about 0.021 wt %. The effective distribution coefficient of sodium is 2.5–4.4 × 10−3. The conditions for constitutional supercooling at the crystallization front are considered.

Phase equilibria in the Ba2Na3[B3O6]2F-BaF2 system

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.

Growth and structure of barium sodium orthoborate NaBaBO3 crystals

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.

Synthesis of scandium orthoborate powders

Two polymorphs of scandium orthoborate, ScBO3, are synthesized by adding aqueous ammonia to aqueous solutions of scandium nitrate and boric acids and calcining the resulting precipitates. Dehydration of the precipitates reaches completion below 300°C, and further heating leads to highly exothermic crystallization near 750°C. The synthesized ScBO3 powders consist of submicron-sized particles.

Change of symmetry and rotation of thermal field as a new method of control of heat and mass transfer in crystal growth (by example of β-BaB2O4)

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.

Search for compounds of the NaBaR(BO3)2 family (R = La, Nd, Gd, and Yb) and the new NaBaYb(BO3)2 orthoborate

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