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1.
The crystal structure of BaNd2Ti3O10 has been determined by electron diffraction and high-resolution electron microscopy. The unit cell is monoclinic with P21/m as the most probable space group and not orthorhombic as previously found by X-ray diffraction. However, the structure has an orthorhomic pseudosymmetry, but due to the small Nd3+ cations the octahedra are titled and the structure is monoclinic. The cell dimensions based on X-ray data are: am = 7.7310 ± 0.0006 Å; bm = 7.6661 ± 0.0007 Å; cm = 14.210 ± 0.002 Å; βm = 97.82 ± 0.01°.  相似文献   

2.
The phase equilibria in the system Na4P2O7Mg2P2O7 were studied by means of DTA, hot stage microscopy and X-ray diffraction analysis. There is one intermediate compound in the system which melts congruently at 832°C of chemical composition Na7Mg4.5(P2O7)4. It crystallizes in the triclinic system with unit cell constants: a = 10.882(1), b = 9.734(1), c = 6.372(1) Å; α = 112.49(1), β = 99.63(1), γ = 107.40(1)°.  相似文献   

3.
The crystal structure of the orthorhombic disodium nonatitanate, Na2Ti9O19, has been determined on the basis of 1-MV high-resolution structure images, in which each site of the titanium and sodium atoms is clearly resolved. The crystal has an orthorhombic symmetry with lattice parameters a = 12.2, b = 3.78, and c = 30.1 Å. The space group of the crystal is either Ccmm or Cc2m. The crystal structure of the orthorhombic nonatitanate is closely related to that of the monoclinic nonatitanate reported previously in which the structure contains sodium titanium dioxide bronze-type units connected by bridging TiO6 octahedra. The orthorhombic crystal can be described in terms of a unit-cell twinning of the monoclinic crystal. It is shown that migrations of sodium ions occur by electron beam irradiation.  相似文献   

4.
Four definite compounds exist in the Sm2O3Ga2O3 binary phase diagram, namely: Sm3GaO6, Sm4Ga2O9, SmGaO3, and Sm3Ga5O12. The 31 compound is orthorhombic (space group Pnna - Z.4) with the cell parameters: a = 11.400Å, b = 5.515Å, c = 9.07Å and belongs to the oxysel family. Sm3GaO6 and SmGaO3 melt incongruently at 1715 and 1565°C; Sm4Ga2O9 and Sm3Ga5O12 have a congruent melting point at 1710 and 1655°C. With regard to the Gd2O3Ga2O3 system three definite compounds have been identified: Gd3GaO6, Gd4Ga2O9, and Gd3Ga5O12. Only the garnet melts congruently at 1740°C with the following composition: Gd3.12Ga4.88O12. Gd3GaO6, and Gd4Ga2O9 melt incongruently at 1760 and 1700°C. GdGaO3 is only obtained by melt overheating which may yield an equilibrium or a metastable phase diagram.  相似文献   

5.
A new compound of sodium nonatitanate, Na2Ti9O19, has been prepared by the hydrothermal reactions of titanium dioxide gel with sodium hydroxide aqueous solution. The crystal has a C-centered monoclinic lattice with the unit-cell dimensions a = 12.2, b = 3.78, c = 15.3Å, and β = 98.0°. It is expected that the structure consists of a framework different from those in tri-, hexa-, hepta-, and octatianates.  相似文献   

6.
The synthesis of a new calcium ferrite CaFe4O6 has been carried out at 1125°C under a controlled atmosphere of H2H2O. The existence of this compound modifies a part of the diagram FeCaO. The crystal structures of the ferrites CaFe2+nO4+n (n = 1, 2, 3) have been resolved on a series of single crystals; these ferrites crystallize in the orthorhombic system, space group Cmcm, with the average parameters a = 3.04 Å, b = 10 Å, c = 10 + 2.65 nÅ. The three structures derive from each other through an intergrowth process, in the direction of the c axis, with CaFe2O4 blocks between the FeO blocks. The coordination of the iron atoms is slightly changed by the nature of the neighboring blocks during stacking.  相似文献   

7.
Ba6Ti17O40, Ba4Ti13O30, BaTi4O9, and Ba2Ti9O20 are the only compounds which were found to have a stability range in the subsolidus of the BaTiO3TiO2 system. BaTi2O5 and BaTi5O11, reported in other studies, apparently are not stable. The compound reported as Ba2Ti5O12 appears to have been mistaken for Ba6Ti17O40. X-Ray diffraction powder data are given for this phase which is monoclinic with a = 9.890, b = 17.117, c = 18.933 Å and β=98°42.6′. The phase formulated previously as BaTi3O7 is shown to be Ba4Ti13O30 based on structural and density considerations, phase equilibria, and single crystal and powder X-ray diffraction data. This compound is orthorhombic with a = 17.072, b = 9.862, and c = 14.059 Å, probable space group, Cmca. An idealized structure for this phase is proposed. Ba2Ti9O20 decomposes above 1300°C in the solid state to BaTi4O9 plus rutile. Single crystals were grown using BaF2 as a mineralizer.  相似文献   

8.
Compounds Ce2TiO5, Ce2Ti2O7, and Ce4Ti9O24 were prepared by heating appropriate mixtures of solids containing Ce4+ and Ti3+ or Ti which were placed in a platinum-silica-ampoule combination at T = 1250°C (3d) under vacuum. The new compounds were characterized by powder patterns. We obtained Ce2TiO5 which is isotypic to La2TiO5 and crystallizes in the Y2TiO5-type (space group Pnma) with a = 10.877(6) Å, b = 3.893(1) Å, c = 11.389(8) Å, Z = 4. Ce2Ti2O7 is isotypic to La2Ti2O7 and crystallizes in the monoclinic Ca2Nb2O7 type (space group P 21) with a = 7.776(6) Å, b = 5.515(4) Å, c = 12.999(6) Å, β = 98.36(5), Z = 4. The compound Ce4Ti9O24 crystallizes orthorhombic with a = 14.082(4) Å, b = 35.419(8) Å, c = 14.516(4) Å, Z = 16. The new cerium titanate Ce4Ti9O24 is isotypic to Nd4Ti9O24 (space group Fddd (No. 70)) which represents a novel type of structure.  相似文献   

9.
The crystal structures of (Ti1?xScx)2O3, x = 0.0038, 0.0109, and 0.0413, and of (Ti0.99Al0.01)2O3, have been determined from X-ray diffraction data collected from single crystals using an automated diffractometer, and have been refined to weighted residuals of 25–34. Cell constants have also been determined for x = 0.0005, 0.0019, and 0.0232. The compounds are rhombohedral, space group R3c, and are isomorphous with α-Al2O3. The hexagonal cell dimensions range from a = 5.1573(2)Å, c = 13.613(1)Å for (Ti0.9995Sc0.0005)2O3 to a = 5.1659(4)Å, c = 13.644(1)Å for (Ti0.9587Sc0.0413)2O3, and a = 5.1526(2)Å, c = 13.609(1)Å for (Ti0.99Al0.01)2O3. Sc and Al substitution cause similar increases in the short near-neighbor metal-metal distance across the shared octahedral face; for Sc doping the increase is from 2.578(1) Å in pure Ti2O3 to 2.597(1) Å in (Ti0.9587Sc0.0413)2O3. By contrast, changes in the metal-metal distance across the shared octahedral edge appear to be governed by ionic size effects. The distance increases from 2.994(1) Å in Ti2O3 to 3.000(1) Å in (Ti0.9587Sc0.0413)2O3 and decreases to 2.991(1) Å in (Ti0.99Al0.01)2O3.  相似文献   

10.
The formula of a new compound isolated in the LaOsO system has been established by means of crystal structure determination. There are two La3Os2O10 units in a face-centered monoclinic unit cell (S.G. C2m); a = 7.911(2) Å, b = 7.963(2) Å, c = 6.966(2)Å, β = 115.76(2)°;. For 1082 intensities, collected on an automated single-crystal diffractometer, the final R value was 0.025 after absorption corrections. The structure consists of isolated Os2O10 clusters composed of two edge-shared OsO6 octahedra. These dimeric units are connected together by two types of La3+ ions in eightfold coordination. In view of the OsOs distance inside the pair (2.462 Å), La3Os2O10 provides an example of metal-metal bonding involving a transition metal in a half-integral formal oxidation state of 5.5.  相似文献   

11.
The preparation, single crystal growth, and crystallographic properties of a close-packed, eight-layer, hexagonal (a = 5.803 Å, c = 19.076 Å) modification having the stoichiometry Ba8Nb6Li2O24 and of a close-packed, ten-layer, hexagonal (a = 5.760 Å, c = 23.742 Å) phase with Ba10W6Li4O30 stoichiometry are discussed. The isostructural Ba8Ta6Li4O24 form of the eight-layer phase was also prepared (a = 5.802 Å, c = 19.085 Å). Proposed crystal structures involve the pairing of lithium and metal (Nb, Ta, or W) octahedra to yield face-sharing units. The relationship of this phenomenon to other known close-packed phases containing Li is demonstrated. An investigation of the Ba8Nb6Li2O24Ba10W6Li4O30 system is reported.A tetragonal bronze phase homogeneity region was delimited at 1200°C in the BaONb2O5Li2O system. A new orthorhombic phase (a = 10.197 Å, b = 14.882 Å, c = 7.942 Å) was prepared with the stoichiometry Ba4Li2Nb10O30.  相似文献   

12.
The phase relations in the Yb2O3Ga2O3CoO system at 1300 and 1200°C, the Yb2O3Ga2O3NiO system at 1300 and 1200°C, the Yb2O3Ga2O3CuO system at 1000°C and the Yb2O3Ga2O3ZnO system at 1350 and 1200°C, the Yb2O3Cr2O3CoO system at 1300 and 1200°C, the Yb2O3Cr2O3NiO system at 1300 and 1200°C, the Yb2O3Cr2O3CuO system at 1000°C, and the Yb2O3Cr2O3ZnO system at 1300 and 1200°C were determined in air by means of a classical quenching method. YbGaCoO4 (a = 3.4165(1) and c = 25.081(2) Å), YbGaCuO4 (a = 3.4601(4) and c = 24.172(6) Å), and YbGaZnO4 (a = 3.4153(5) and c = 25.093(7) Å), which are isostructural with YbFe2O4 (space group: R3m, a = 3.455(1) and c = 25.109(2) Å, were obtained as stable phases. In the Yb2O3Ga2O3NiO system and the Yb2O3Cr2O3MO system (M: Co, Ni, Cu, and Zn), no ternary stable phases existed.  相似文献   

13.
Single crystals of the title compounds have been grown by the Czochralski technique. Pb4P2O9 crystallizes in the space group P21c with the parameters a = 9.4812 Å, b = 7.1303 Å, c = 14.390 Å, β = 104.51° and Pb8P2O13 in C2m with a = 10.641 Å, b = 10.206Å c = 14.342 Å, β = 98.34°.  相似文献   

14.
The LiPO3CeP3O9 and NaPO3CeP3O9 systems have been investigated for the first time by DTA, X-ray diffraction, and infrared spectroscopy. Each system forms a single 1:1 compound. LiCe(PO3)4 melts in a peritectic reaction at 980°C. NaCe(PO3)4 melts incongruently, too, at 865°C. These compounds have a monoclinic unit cell with the parameters: a = 16.415(6), b = 7,042(6), c = 9.772(7)Å; β = 126.03(5)°; Z = 4; space group C2c for LiCe (PO3)4; and a = 9.981(4), b = 13.129(6), c = 7.226(5) Å, β = 89.93(4)°, Z = 4, space group P21n for NaCe(PO3)4. It is established that both compounds are mixed polyphosphates with chain structure of the type |MIIMIIIII (PO3)4|MII: alkali metal, MIIIII: rare earth.  相似文献   

15.
The phase relations in the In2O3Fe2O3CuO system at 1000°C, the In2O3Ga2O3CuO system at 1000°C, the In2O3Fe2O3CoO system at 1300°C, and the In2O3Ga2O3CoO system at 1300°C were determined by means of a classical quenching method. InFeCuO4 (a = 3.3743(4) Å, c = 24.841(5) Å), InGaCuO4 (a = 3.3497(2) Å, c = 24.822(3) Å), and InGaCoO4 (a = 3.3091(2) Å, c = 25.859(4) Å) having the YbFe2O4 crystal structure, In2Fe2CuO7 (a = 3.3515(2) Å, c = 28.871(3) Å), In2Ga2CuO7 (a = 3.3319(1) Å, c = 28.697(2) Å), and In2FeGaCuO7 (a = 3.3421(2) Å, c = 28.817(3) Å) having the Yb2Fe3O7 crystal structure, and In3Fe3CuO10 (a = 3.3432(3) Å, c = 61.806(6) Å) having the Yb3Fe4O10 crystal structure were found as the stable ternary phases. There is a continuous series of solid solutions between InFeCoO4 and Fe2CoO4 which have the spinel structure at 1300°C. The crystal chemical roles of Fe3+ and Ga3+ in the present ternary systems were qualitatively compared.  相似文献   

16.
Single crystals of Pb2P2O7 have been grown by the Czochralski technique. They have the triclinic space group P1 with cell dimensions a = 6.9627 Å, b = 6.9754Å, c = 12.764 Å, α = 96.78°, β = 91.16°, γ = 89.68°. There are four molecules per unit cell. Dielectric properties for this compound have been measured and are discussed.  相似文献   

17.
The title compound has been prepared by reaction of (C5H5)2Cr with oxindole (indole with CO in place of CH2 at the 2-position). Red single crystals belong to space group P21/c with a = 10.107(4) Å, b = 22.496(7) Å, c = 9.210(3) Å, β = 93.26(3)°, V = 2091(2), and Z = 2. The centrosymmetric molecule has a CrCr distance of 2.495(4) Å. The mean CrO and CrN distances for the bonds to bridging oxindolate anions are 2.024(7) and 2.065(8) Å, respectively. There is an oxindole molecule bound at each end with a CrO axial bond of length 2.341(8) Å and a hydrogen bond from the oxindole NH group to an equatorial oxygen atom of length 2.83(1) Å. The significance of this compound with respect to CrCr bonding is discussed.  相似文献   

18.
The crystal structure of dibarium triferrite Ba2Fe6O11 has been solved by direct methods, using intensity data collected by means of an automated diffractometer (MoKα radiation) and corrected for absorption. It crystallizes in the orthorhombic space group Pnnm: a = 23.024(10)Å, b = 5.181(3) Å, c = 8.900(4) Å, Z = 4. Program MULTAN was successfully used for locating Ba2+ and most of the Fe3+ ions. The structure was further refined by conventional Fourier and least-squares methods (full-matrix program) to a final R value of 0.045 for 1448 observed reflections. Fe3+ ions occur in both octahedral (FeO mean distance: 2.02 Å) and tetrahedral (FeO mean distance: 1.865 Å) coordination. Two types of Ba2+ ions are found, with six and seven neighboring oxygen atoms. The structure consists of sheets of edge-shared FeO6 octahedra which are connected by means of corner-shared tetrahedra.  相似文献   

19.
Nb2Zr6O17 is orthorhombic, space group Ima2, with a = 40.91, b = 4.93, c = 5.27 Å. The asymmetric structural unit contains one octahedron, three sevenfold coordinated ions, and one square antiprism, and its relations to the fluorite and ZrO2 structures are discussed. Variations in compositions can be accounted for by increasing or decreasing the number of sevenfold coordinated ions in the structure.  相似文献   

20.
A continuous series of Ta2O5Nb2O5 solid solutions was obtained by anodically dissolving calculated amounts of tantalum and niobium in a saturated solution of NH4Cl in methanol (at room temperature), evaporation of the solvent, and thermal decomposition of the product at temperatures not exceeding 750–800°C. X-ray diffraction analysis showed that at all Ta:Nb ratios the product was isomorphic with β-Ta2O5 (γ-Nb2O5); all reflections could be indexed in an orthorhombic cell, with a increasing linearly from 6.170 to 6.192 Å and c decreasing linearly from 3.935 to 3.885 Å as Ta was substituted for Nb. The changes in parameter b as a function of composition were less pronounced and its values were between 3.657 and 3.662 Å. The method may be used for the preparation of various mixed oxides that are difficult to prepare by other techniques.  相似文献   

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