Synthesis and Crystal Structure of Fluoride K2(Ta0.9I0.1)F7 with the Micro-Isomorphic Substitution in the Ta Cationic Position

Crystallography Reports - Fluoride crystals K2(Ta0.9I0.1)F7 (sp. gr. Р21/c) complementary to the K2TaF7 and K2NbF7 fluoride family have been obtained by hydrothermal synthesis. Their...     

Synthesis and Crystal Structure of New Indium Iodate (K<Subscript>0.6</Subscript>Na<Subscript>0.4</Subscript>Ba)In[IO<Subscript>3</Subscript>]<Subscript>6</Subscript>

Crystals of new indium iodate (K_0.6Na_0.4Ba)In[IO₃]₆ were prepared by the hydrothermal synthesis. The unit-cell parameters are a = 11.3984(3) Å, с = 11.3817(3) Å, sp. gr. R3?. The chemical formula of the compound was derived from the structure determination and refinement with anisotropic displacement parameters to R = 0.0284. In the structure the InO₆ octahedra share vertices with six umbrella-like [IO₃]–groups typical of iodates and form isolated 3?-symmetric charged \(\rm{In[IO_{3}]_6^{3-}}\) clusters. Large Ba, K, and Na cations occupy a common site on a threefold axis due to the isomorphous substitution and compensate the charge of the clusters. The new structure extends the family of the recently discovered alkali-metal and barium iodates containing Ti and Zr atoms in octahedral sites. The iodate K₂Ge[IO₃]₆ containing Ge atoms in the centers of octahedra is the parent compound of this structural family.     

Single-Crystal Synthesis and Structures of Rb-Boroleucite Rb(BSi2)O6 and Boropollucite Cs(BSi2)O6 at 293 and 120 K

Crystallography Reports - The structures of Rb-boroleucite Rb1.0(B0.333Si0.667)3O6 and boropollucite Cs0.87(B0.290Si0.710)3O6 were studied using single crystals, which were prepared under...     

Crystal-Chemical Approach to the Determination of Oxo-Centered Complexes in Divalent Lead Silicates

Crystallography Reports - The crystal-chemical analysis of seven structures of synthetic and natural lead silicates with formulas Pb2SiO4, Pb11Si3O17, Pb3Si2O7,...     

Synthesis and crystal structure of BaFe[PO<Subscript>4</Subscript>](OH), a new orthophosphate with a mixed framework related to alumosilicates of the nepheline group

A new orthophosphate BaFe[PO₄](OH) is obtained by hydrothermal synthesis. The unit cell parameters are as follows: a = 9.711(6), b = 8.991(5), and c = 4.912(2) Å; space group P2₁2₁2₁. The structure has no features in common with the structures of three Ba-Fe phosphates studied. At the same time, the mixed framework, which is composed of five-vertex polyhedra of Fe and P-tetrahedra, exhibits a similarity to the frameworks of a number of alumosilicates belonging to the group of nepheline (nepheline NaAlSiO₄, kalsilite KAlSiO₄, and RbAlSiO₄), as well as the beryllonite NaBePO₄ beryllophosphate and H₃O · ZnPO₄ zin-cophosphate. All the frameworks contain six-membered rings which consist of alternating tetrahedra of different kinds with compensating cations at the ring centers. The topology of the new framework is most closely related to that of nepheline. Structures of this type are of interest as potential ion exchangers and ion-conducting materials.     

A new nonlinear optical borate, Na0.5Pb2[B5O9](OH)1.5 · 0.5H2O, from the orthorhombic hilgardite family

A new polar representative of the hilgardite structural family, Na_0.5Pb₂[B₅O₉](OH)_1.5 · 0.5H₂O (space group Pnn2), is synthesized under hydrothermal conditions. The crystal structure of the compound synthesized is similar to the structure of the previously studied polar compound Na_0.5Pb₂[B₅O₉]Cl(OH)_0.5 and is intermediate between the latter compound and the centrosymmetric hydrate Pb₂[B₅O₉](OH) · 0.5H₂O. The additional peak revealed in the electron density in the vicinity of the Pb(1) atom is attributed to the stereochemically active lone electron pair of this atom. The lone electron pair is oriented toward the two most distant oxygen atoms involved in the Pb(1) coordination environment, namely, O(7) and O(2), which are located in a boron-oxygen framework layer in the ac plane, not toward the (00_z) channel occupied by water molecules. The nonequivalence in the stereochemical activity of two lead atoms [Pb(1) > Pb(2)] is similar to that observed in the nonlinear optical borate Pb₂[B₄O₅(OH)₄](OH)₂ · H₂O related to BiB₃O₆.     

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 Ln[B6O9(OH)3] borates (Ln = Sm-Lu): Structure, properties, and structural relation to cationic Li4[B7O12]Cl conductors (Li-Boracites)

Crystals of new rare earth borates of the composition Ln[B₆O₉ (OH)₃] (Ln = Sm-Lu), sp. gr. R3c are synthesized under hydrothermal conditions. Their crystal structures are determined on single crystals with Ln = Ho, Gd without preliminary determination of their chemical formulas. The polar anionic framework of the crystals consists of BO₃ triangles and BO₄ tetrahedra and has wide channels along the threefold axis of the structure, which are similar to the channels along the a, b, and c axes in cubic Li₄[B₇O₁₂]Cl boracite with Li conductivity. Rare earth atoms are arranged in the structure over the cubic F pseudolattice, whereas the analogous positions in Li boracites are filled with Cl anions. The squared optical nonlinearity of the new crystals is comparable with the nonlinearity of quartz, whereas the electrical conductivity in borates at 300°C exceeds 10⁻⁶ S/cm. __________ Translated from Kristallografiya, Vol. 49, No. 4, 2004, pp. 681–691. Original Russian Text Copyright ? 2004 by Belokoneva, Ivanova, Stefanovich, Dimitrova, Kurazhkovskaya.