O. V. Dimitrova

Potassium bromo-borate K3[B6O10]Br—A new nonlinear optical material

A new polar hexaborate, K3[B6O10]Br (space group R3m), is synthesized under hydrothermal conditions. The radical anion is composed of macallisterite hexaborate blocks 6[3Δ + 3T] formed by boron triangles and boron tetrahedra. The blocks are joined together through vertices into a [B6O10]∞∞∞2− zeolite-like framework of a new type. Large K+ cations and Br− anions are located in extended channels that are aligned parallel to rhombohedral translations of the crystal lattice. The structure of the sublattice formed by large ions consists of BrK6 bromo-centered octahedra, which are linked together through vertices into a hexagonally distorted perovskite framework. The perovskite framework is inserted into the boron-oxygen framework so that these two frameworks do not intersect. The nonlinear optical properties of powdered samples of the K3[B6O10]Br compound are investigated using the second harmonic generation method. It is found that the K3[B6O10]Br compound exhibits a high nonlinear optical activity that exceeds the activities of the majority of borate compounds and is characteristic of haloid borates of the hilgardite family.

Crystal structures of two new Ba borates pentaborate, Ba2[B5O9]Cl-0.5H2O and Ba2[B5O8(OH)2](OH)

Abstract Two new Ba borates Ba 2 [B 5 O 9 ]Cl·0.5H 2 O ( I ) and Ba 2 [B 5 O 8 (OH) 2 ](OH) ( II ) were synthesized in the hydrothermal systems ACl (A 2 CO 3 )–BaO–B 2 O 3 –H 2 O, where A=Li, Na, K, Rb, Cs, NH 4 cations ( T =550 K, P =100–150 bar, 20–25 days). The crystal structures of I and II were established by X-ray single crystal diffraction; I : space group Pnn 2; a =11.716(2), b =11.574(2), c =6.700(1)A, V =908.5(2) A 3 , R hkl =0.057 for 831 Fo >4 σ ( Fo ); II : space group P 2 1 / c ; a =6.713(2), b =16.480(5), c =8.387(3) A, β =106.80(3)°, V =888.2(4) A 3 , R hkl =0.092 for 857 Fo ⩾4 σ ( Fo ). The topology of the borate framework of phase I is the same as compared with that revealed in the orthorhombic structure of Ca 2 B 5 O 9 Br that is an orthorhombic modification of natural hilgardite. The pentaborate framework [B 5 O 9 ] 3− is formed by three crystallographically independent BO 4 tetrahedra and by two BO 3 triangles. II is a sheet borate: its pentaborate [B 5 O 8 (OH) 2 ] 3− sheets are characterized by the same ratio between BO 4 tetrahedra and BO 3 triangles as compared with the pentaborate framework in I and in all natural hilgardites.

Acentric polyborate, Li3[B8O12(OH)3], with a new type of anionic layer and Li atoms in the cavities.

Single crystals of Li3[B8O12(OH)3] were synthesized under hydrothermal conditions using a complex initial composition that included SiO2. The crystal structure is acentric, space group P62c, with a = 8.9301(2) Å and c = 15.9962(4) Å, and Z = 4. New double three-membered rings of hexaborate blocks and monoborate triangles are connected into a polyborate anionic layer. Although the new structure is similar to double ring silicate Na3Y[Si6O15], detailed comparison of the anionic groups demonstrates principal differences between silicates and borates. Sodium silicate was proposed as an intrinsic fast ion conductor, and for the new borate Li ionic conductivity is very probable, as Li atoms in it are in positions similar to the Na atoms in the silicate.

The crystal structures of two new Ba borates: pentaborate hydrate, Ba[B5O8(OH)]·H2O, and decaborate, LiBa2[B10O16(OH)3]

Abstract Two new Ba borates, Ba[B 5 O 8 (OH)]H 2 O ( I ) and LiBa 2 [B 10 O 16 (OH) 3 ] ( II ), were synthesized in the hydrothermal systems Cs 2 CO 3 –BaO–B 2 O 3 –H 2 O ( T =550 K, P =100 bar, 20 days). The crystal structures of I and II were established from X-ray single crystal diffraction; I , space group P-1 , a =6.785(5), b =6.831(5), c =10.629(6) A, α =100.07(4), β =91.98(6), γ =119.46(7)°, V =417.01(58) A 3 , R hkl =0.069 for 1328 Fo >4 σ ( Fo ); II , space group P-1 , a =6.732(1), b =11.369(2), c =11.581(2) A, α =119.31(3), β =90.11(3), γ =73.08(3)°, V =728.87(42) A 3 , R hkl =0.048 for 1166 Fo ≥4 σ ( Fo ). The topology of the borate sheet of phase I is practically the same as that in the monoclinic structure of biringuccite, Na 2 [B 5 O 8 (OH)]·H 2 O. The gaps between the sheets in synthetic Ba-biringuccite contain Ba atoms and water molecules. Phase II is characterized by a new boron sheet, formed by five crystallographically independent BO 4 tetrahedra and by five BO 3 triangles.

New hilgardite-group polyborate Pb2[B5O9]Br with high optical nonlinearity

New anhydrous lead borate Pb2[B5O9]Br (sp. gr. Pnn2) was synthesized by the hydrothermal method. The second harmonic generation from polycrystalline samples of Pb2[B5O9]Br is characterized by a higher signal than that observed in powdered LiB3O5. The crystal structure of the new hilgardite-group compound was refined by the Rietveld method. Analysis of the known orthorhombic polar varieties of hilgardites, including the new compound, showed that their boron-oxygen frameworks are occupied by the Pb2+, Ca2+, Eu2+, and Ba2+ cations; the Cl−, Br−, and OH− anions; and water molecules in combinations determined by their sizes.

New isoformula iodates In(IO3)3 and Sm(IO3)3 with different crystal structures: Specific structural features of I5+ compounds

AbstractNew iodates, namely, In(IO3)3 (space group R

Layer structure of (NH4)CoPO4

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Structure and nonlinear optical properties of the family of lead and barium nonaborates with a zeolite-like framework

) and Sm(IO3)3 (space group P21/a), are synthesized under hydrothermal conditions. The original crystal structure of the In(IO3)3 compound is determined without prior knowledge of the chemical formula. The Sm(IO3)3 compound is isostructural to the Gd(IO3)3 compound. The [IO4]3- tetrahedra with three short I-O bonds have an umbrella coordination, which is characteristic of pentavalent iodine, and form anionic radicals, such as a ring radical in the In(IO3)3 iodate, a triple helix in the isoformula compound Fe(IO3)3, a complex chain in the Sm(IO3)3 iodate, and a linear triortho group in the Sm(IO3)3·H2O compound. All radicals contain triortho groups. The structural differences are determined by different ionic radii and shapes of the coordination polyhedra of the cations (indium and iron octahedra and an eight-vertex samarium polyhedron).