In1.08Gd0.92Ge2O7: a new member of the thortveitite family

Indium gadolinium digermanium heptaoxide, In_1.08Gd_0.92Ge₂­O₇, with a thortveitite‐type structure, has been prepared as a polycrystalline powder material by a high‐temperature solid‐state reaction. As in the mineral thortveitite, the crystal structure belongs to the monoclinic system, with space group C2/m (No. 12). The precise structural parameters were obtained by applying the Rietveld method of refinement to the X‐ray powder diffraction data. This layered structure presents, on one side, a honeycomb‐like arrangement of the unique octahedral site, which is occupied randomly by In and Gd atoms, and, on the other side, sheets of isolated Ge₂O₇ diortho‐groups made up of double tetrahedra sharing a common vertex and displaying C_2h point symmetry. This compound showed a remarkable photoluminescence effect when it was irradiated with the X‐ray beam during the X‐ray diffraction measurements, and with the α beam during the Rutherford back‐scattering spectrometry experiments employed to analyze the chemical stoichiometry.     

Crystal structure of a new gallium tellurite: Ga2Te4O11

Ga₂Te₄O₁₁ crystallises with triclinic symmetry (space group P1) and unit cell parameters: a = 5.125(1) Å, b = 6.559(1) Å, c = 8.173(2) Å, α = 75.06(2), β = 89.25(2), γ = 69.62(2), Z = 1. Its crystal structure has been refined by a full matrix least-squares process to R₁ = 0.023 and wR₂ = 0.060 values, on the basis of 2931 independent single crystal X-ray reflections. It can be described as a three-dimensional polyhedral network of independent Te₂O₆ groups of TeO₃ trigonal pyramids and TeO₄ disphenoids sharing corners, and infinite (Te₂O₅)_∞ quasi-linear chains of the same corner-sharing TeO₃ and TeO₄ units, linked one to the other via common corner or common edge by GaO₄ and GaO₅ polyhedra. The stereochemical activity of the lone pair of each Te atom has been analysed and a comparison is made with all the known other M₂Te₄O₁₁ crystal structures.     

Crystal structure of a new vanadate variety in the lomonosovite group: Na5Ti2O2[Si2O7](VO4)

The title compound has been prepared by a flux crystallisation method and its crystal structure was determined by single crystal X-ray diffraction: space group P, a=5.309(1), b=7.133(1), c=14.746(2) Å, α=99.05(1), β=95.97(1), γ=90.08(1)°, wR₂=0.073, R=0.028. The structure may be described as built by seidozerite modules of composition Na₂Ti₂O₂Si₂O₇ — brucite-type layers of [TiO₆] and [NaO₆] octahedra embedded between layers of [TiO₆] octahedra, [Si₂O₇] groups and [NaO₈] polyhedra. These almost centrosymmetrical triple-layers alternate along the c-axis with polar double-layer-modules of composition Na₃VO₄ formed by isolated [VO₄]³⁻ anions and six- and four-coordinate Na cations. The crystal structure is discussed in context with minerals of the lomonosovite group. The thermal decomposition behaviour suggests a decay to the single modular components Na₂Ti₂O₂Si₂O₇ and Na₃VO₄.     

Crystal structure of [Al4(OH)6(H2O)12][Al(H2O)6]2Br12: a new polyaluminum compound

A vertex-shared tetrahedral [Al(4)(OH)(6)(H(2)O)(12)](6+) (Al(4)) and a disordered [Al(H(2)O)(6)](3+) (Al(1)) that coexist in a 1:2 ratio within each unit cell were observed in the structure of [Al(4)(OH)(6)(H(2)O)(12)][Al(H(2)O)(6)](2)Br(12), which crystallized in a cubic Fd3m space group from a spontaneously hydrolyzed solution of AlBr(3). The former is composed of four AlO(6) octahedra that are connected to each other by sharing three vertexes of each octahedron and form a large regular tetrahedron with ideal T(d) symmetry. The central Al(3+) ion of the latter is coordinated by 6 disordered OH(2) molecules, that form a core-shell structure with ideal D(3d) symmetry.     

Crystal structure of sodium potassium zinc diphosphate NaKZnP2O7

Single crystals of NaKZnP₂O₇ were grown, and their crystal structure was determined by X-ray diffraction (space group P2₁/n, a = 12.585(5) Å, b = 7.277(5) Å, c = 7.428(5) Å, β = 90.00(5)°, Z = 4, 1916 F(hkl), R ₁ = 0.0461). The structure contains a 3D tetrahedral zinc phosphate framework with a system of intersecting channels running along the b and c axes. The sodium and potassium atoms are coordinated to six and seven oxygen atoms, respectively, and reside inside these channels; the potassium cations, which are larger than the sodium cations, are located at channel intersections.     

Crystal structure of the pyrovanadate K4V2O7

The crystal structure of anhydrous K₄V₂O₇ (I) is determined by powder X-ray diffraction. The compound crystallizes in the monoclinic system (a = 10.222(1) Å, b = 6.2309(8) Å, c = 7.282(1) Å, β = 101.31(1)°, space group C2/m, Z = 2). The structure contains layers of isolated V₂O₇ pyrovanadate groups separated by layers of potassium cations. The hydration and dehydration of I are studied by thermal analysis and high-temperature X-ray diffraction. The dehydration is accompanied by decomposition of the starting crystal hydrate to give intermediate compounds. Anhydrous compound I undergoes a reversible phase transition at 740°C. The high-temperature phase is assumed to have a hexagonal unit cell (a = 6.169(4) Å, c = 15.72(1) Å, Z = 2).     

Yttrium pyrogermanate,Y2Ge2O7

The structure of diyttrium digermanate, Y₂Ge₂O₇, has been determined in the tetragonal space group P4₃2₁2. It contains one Y, one Ge (both site symmetry 1 on general position 8b) and four O atoms [one on special position 4a (site symmetry ..2) and the remaining three on general positions 8b]. The basic units of the structure are isolated Ge₂O₇ groups, sharing one common O atom and displaying a Ge—O—Ge angle of 134.9 (3)°, and infinite helical chains of pentagonal YO₇ dipyramids, parallel to the 4₃ screw axis. The crystal investigated here represents the left‐handed form of the tetragonal R₂Ge₂O₇ compounds (R = Eu³⁺, Tb³⁺, Er³⁺, Tm³⁺ and Lu³⁺).     

Crystal structure of zinc-tetrametaphosphate octahydrate: Zn2P4O12 · 8 H2O

Crystal structure of zinc tetrametaphosphate octahydrate: Zn₂P₄O₁₂ · 8 H₂O has been solved using 1888 X-ray reflections with a final R value: 0.031. This salt is triclinic, P1 , with Z = 1 and the following unit cell dimensions: a = 8.610(5), b = 7.137(5), c = 7.108(5) Å, α = 96.09(5), β = 105.99(5), γ = 100.49(5)°. This salt is the third example of an hydrated tetrametaphosphate of a bivalent cation. The two zinc atoms are octahedrally coordinated. A complete hydrogen bond scheme is given.     

基于Al6Ge2O13还原制备Ge纳米粒子及其光致发光性能研究

以3-三氯锗丙酸和硝酸铝为原料，通过共沉淀法合成了Al₆Ge₂O₁₃陶瓷粉体，并利用TG-DSC、FTIR、XRD等研究了其形成过程。采用选择还原技术对Al₆Ge₂O₁₃进行还原处理，还原产物观察到发光峰位于564、611、681、730和774 nm的室温光致发光现象。比较不同温度下还原的样品，发现550 ℃保温3 h还原制备的样品发光强度最强，通过XRD、XPS和Raman光谱研究表明样品在可见和近红外光区的发光是源于平均粒径为1.98 nm且未能形成完整晶格的Ge纳米粒子团簇。     

Crystal structure of a new lithium indium borate Li3InB2O6

Single crystals of synthetic Li₃InB₂O₆ were obtained by heating a mixture of Li₂CO₃, In₂O₃ and B₂O₃; its formula was determined by the resolution of the structure from X-ray diffraction data. The compound is monoclinic, space group P2₁/n; the unit cell parameters are a=5.168(5) Å, b=8.899(9) Å, c=10.099(10) Å, β=91.112(17)°; Z=4. The crystal structure was solved from 669 reflections until R=0.0249; it exhibits a three-dimensional framework of vertex-sharing InO₅ trigonal bipyramids and BO₃ triangles, which isolates Li ions in channels. This structure is characterized by unusual oxygenated environments of In cations and of one of the three Li cations, which are forming more or less regular trigonal bipyramids. This compound melts incongruently at 827 °C; the powder may be obtained by annealing at 750 °C a mixture of Li₂CO₃, In₂O₃ and B₂O₃.     

Structural investigations and luminescence of In2Ge2O7 and In2Si2O7

The crystal structures of the ordinary pressure forms of indium digermanate In₂Ge₂O₇ and disilicate In₂Si₂O₇ have been studied from X-ray powder diffraction data by Rietveld refinement. They are closely related to that of the thortveitite which crystallizes in the monoclinic system with the space group C2/m and Z = 2. They show luminescence properties below 160 K and 200 K respectively. The luminescence is discussed in terms of crystal structure and compared to that of some other luminescent indium oxides.