Syntheses And Crystal Structrues Of Novel Borate Materials

The continuously development of laser technology puts forward all kinds of new request of optical materials. It requirs high quality of crystals. Besides improving the quality of the present optical crystals through doping, the investigation of the relations between compositions, structures, and properties of optical crystals as well as exploratory syntheses of new types of optical crystal has always been a hot topic.Four novel borates have been prepared by solid-state reactions and hydrothermal reactions, including PbBiBO₄, NaSrB₅O₉, Pb[B₅O₈(OH)]·1.5H₂O and Na₃CaB₅O₁₀. Single-crystal X-ray intensity data were collected on an automated Rigaku AFC7R four-circle diffractometer using monochromatized Mo Kαradiation. The crystal structures were solved by the SHELX-97 software, and physical properties of these compounds were investigated.PbBiBO₄, has been prepared by solid-state reaction at temperature below 800°C. The single-crystal X-ray structural analysis showed that PbBiBO₄ crystallizes in the monoclinic space group P21/n with a = 7.473(1) A, b = 7.517(1) A, c = 7.609(1) A,β= 91.48(1)°, Z = 4. It represents a new structure type in which distorted BiO6 octahedra are connected to each other in corner- and edge-sharing manner to form two-dimensional ²)∞[BiO₄]^5- layers that are bridged by B atoms of BO 3 triangles giving rise to a three-dimensional ³_∞[BiBO₄]^2- framework, with channels parallel to the [010] direction accommodating the pyramidally coordinated Pb2+ cations.NaSrB₅O₉, has been prepared by solid-state reaction at temperature below 800°C. The single-crystal X-ray structural analysis showed that NaSrB₅O₉ crystallizes in the monoclinic space group P21/c with a = 6.499(2) A, b = 13.979(2) A, c = 8.045(2) A,β= 106.92(2)°, V = 699.2(3) A3, Z = 4. NaSrB₅O₉ is a layered compound containing double ring B5O11 building units composed of two BO₄ tetrahedra and three BO3 triangles. Each B5O11 unit is connected to four other equivalent units through exocyclic oxygen atoms to form a two-dimensional∞2 [B₅O₉]3- layer. Symmetry-center related layers are stacked along the b-axis and held together by Na+ and Sr2+ cations via electrostatic interactions.Pb[B₅O₈(OH)] A1.5H₂O, have been prepared by hydrothermal reactions at 170°C. Single-crystal X-ray structural analyses showed that Pb[B₅O₈(OH)] A1.5H₂O crystallizes in a triclinic space group P 1 with a = 6.656(2) A, b = 6.714(2) A, c = 10.701(2) A,α= 99.07(2)°,β= 93.67(2)°,γ= 118.87(1)°, Z = 2. Pb[B₅O₈(OH)] A1.5H₂O is a layered compound containing double ring [B₅O₈(OH)]2- building units that share exocyclic oxygen atoms to form a two-dimensional layer. Symmetry-center related layers are stacked along the c-axis and held together by interlayer Pb²⁺ ions and water molecules via electrostatic and hydrogen bonding interactions. The IR spectra further confirmed the existence of BO3, BO₄, OH groups as well as guest water molecules in Pb[B₅O₈(OH)] A1.5H₂O.Na₃CaB₅O₁₀, has been prepared by solid-state reaction at temperature below 750°C. The single-crystal X-ray structural analysis showed that it crystallizes in the triclinic space group P 1 with a = 7.4403(6) A, b = 9.7530(10) A, c = 12.9289(9) A,α= 90.972(7)°,β= 90.073(7)°,γ= 109.656(6)°, Z = 4. It has a superstructure, with the cell volume being two times of that reported previously. The crystal structure consists of discrete [B5O10]5- anions separated by six-coordinate Ca²⁺ as well as five-, six- and seven-coordinate Na⁺ cations. The IR spectrum further confirms the presence of both BO3 and BO₄ groups.