[en] The intercalation of alkyl monoamines in the protonic oxide HNb₃O₈ x H₂O is quantitative for the amines NH₂C/sub n/H/sub 2n+1/ with n ranging from 1 to 9. The intercalated oxide NH₃CH₃Nb₃O₈ is anhydrous at room temperature whereas monohydrates NH₃C/sub n/H/sub 2n+1/NbO₃ x H₈O₂ are the stable form at room temperature; these latter oxides can be dehydrated into the oxides NH₃C/sub n/H/sub 2n+1/Nb₃O₈ without any destruction of the structure, their zeolithic character is observed. The structural evolution of these compounds is interpreted in terms of a transversal orientation of the amine chains with respect to the [Nb₃O₈]^- layers and compared to the one of the N₃HC/sub n/H/sub 2n+1/TiNbO₅ oxides. (author)

[en] The molybdenum (IV) diphosphate crystallizes in the Pa3 space group with a = 7.944(1) A. The refinement of the atomic parameters with 55 reflections leads to R = 0.048 and R ω = 0.056. The tridimensional framework is built up from Mo0₆ octahedra sharing their corners with P₂0₇ groups. These polyhedra are in mixed layers which exhibit pentagonal windows. 20 refs

[en] The lamellar oxide HK₂Ti₅NbO₁₄ x H₂O can be topotactically dehydrated to K₄Ti₁₀Nb₂O₂₇. Electron diffraction and X-ray diffraction studies of this phase lead to a monoclinic cell with the parameters a = 17.005, b = 3.78, c = 9.01 A and β 92.14⁰. Diffusion streaks on the electron diffraction patterns indicate disorder whereas the existence of two sets of lattices on the same crystal give evidence of the topotactic character of the reaction. A structural model is proposed for K₄Ti₁₀Nb₂O₂₇, which corresponds to the intergrowth of K₃TiNbO₁₄ layers with the K₂Ti₆O₁₃ tunnel structure. The possibility of formation of various intergrowths such as (KTi₅NbO₁₃)/sub n/ (HK₂Ti₅NbO₁₄)/sub n/' is suggested

[en] A new monophosphate of tetravalent vanadium was isolated and its structure has been determined from a single crystal X-ray diffraction study. It crystallizes in the space group P2₁/c with a=5.187(1), b=7.959(2), c=17.187(2)A. The framework is very similar to that observed for Ag(VO)₂(PO₄)₂ and can be described from V₄O₂₀ octahedral units sharing their corners with monophosphates group. This framework delimits tunnels running along a where the cadmium ions are located. In fact, this phosphate belongs to a structural series A(VO)₂(PO₄)₂ with A=Ba, Pb, Ag, Cd and derives from the barium phase by a strong distortion of the framework changing the coordination of a part of vanadium atoms from pyramidal to octahedral. The structural evolution of these phosphates is discussed; the amazing flexibility of the coordination of the interpolated A cations is emphasized

[en] The structure of a new tetravalent phosphate has been determined by single crystal X-ray diffractometry. Although it presents a structure close to that of LiVPO₅, this oxide exhibits a different symmetry. Monoclinic cell parameters are given. The host lattice [VPO₅]_∞ is described as [VO₃]∞] octahedral chains linked together through PO₄ tetrahedra. The geometry of the octahedral chains is intermediate between that of hexagonal tungsten bronze and ReO₃-type structure

[en] K_0.75MoNbP₃O₁₂, M_r=503.009, orthorhombic, Pbcm, a=8.8518 (5), b=9.1453 (11), c=12.5174 (11) A, V=1013.3 (3) A³, Z=4, D_x=3.300 Mg m^-3, λ(Mo Kα)=0.71073 A, μ=3.13 mm^-1, F(000)=953, T=294 K, R=0.029, wR=0.033 for 1235 observed reflections. This compound is isostructural with KMo₂P₃O₁₂-type oxides. Its framework is built up from MoO₆ octahedra and PO₄ tetrahedra which delimit tunnels running along b. Different from KMo₂P₃O₁₂, the tunnels are partly occupied by the potassium ions which are distributed at random. (orig.)

[en] Niobium(IV) niobium(V) phosphate, M_r=470.73, trigonal, Ranti 3c, a=8.6974(7), c=22.123(2) A, V=1449.3(3) A³, Z=6, D_x=3.24 Mg m^-3, λ(Mo Kα)=0.71073 A, μ=2.824 mm^-1, T=294 K, F(000)=223, R=0.0347 and wR=0.03706 for 435 observed reflections. The niobium has a mixed valence (IV)-(V). The framework is built up from NbO₆ octahedra sharing corners with PO₄ tetrahedra and belongs to the empty Nasicon-type structure. (orig.)

[en] Nonaniobium phosphorus pentacosaoxide, PNb₉O₂₅, M_r=1267.11, tetragonal, I4/m, a=15.639 (2), c=3.8317 (4) A, V=937.1 (3) A³, Z=2, D_x=4.49 Mg m^-2, λ(MoKα)=0.71073 A, μ(MoKα)=5.27 mm^-1, F(000)=584, T=294 K, 316 reflections with I>3σ(I), R=0.033, wR=0.031. The framework is composed of ReO₃-type 3x3x∞ columns. Each column shares edges with the four neighboring columns and corners with the PO₄ tetrahedra. (orig.)

[en] Mo₄P₃, M_r=476.68, orthorhombic, Pnma, a = 12.4316(11), b = 3.1581(6), c = 20.4468(30) A, V = 802.7(3) A³, Z = 8, D_m not measured, D_x = 7.89 Mg m^-3, λ(Mo Kα) = 0.71069 A, μ_MoKα = 12.9 mm^-1, F(000) = 1704, T = 293 K, 1476 reflections, R = 0.032, wR = 0.039. Lattice built up from MoP₆ and MoP₅ polyhedra. Mo-P distances range from 2.375 to 3.002 A. (orig.)

[en] K₂Mo₃AlP₈O₂₈, M_r=544.39, triclinic, Panti 1, a=4.8171 (8), b=7.133 (2), c=7.998 (2) A, α=90.53 (2), β=92.95 (2), γ=105.18 (2)deg, V=264.8 (2) A³, Z=0.5, D_x=3.41 Mg m^-3, λ(Mo Kα)=0.71073 A, μ=2.568 mm^-1, T=294 K, F(000)=260.50, R=0.061, wR=0.068 for 856 observed reflections. The host lattice of this phase is built up from MoO₆ and AlO₆ octahedra sharing corners with PO₄ tetrahedra and belongs to the Na_0.5MoP₂O₇-type structure. The tunnels are fully occupied by K⁺ ions and one kind of octahedral site is only occupied by molybdenum, whereas molybdenum and aluminium are distributed at random over the second kind of site. (orig.)