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  • Inorganic Chemistry  (3)
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  • 1
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparation and Structure of LaTa7O19. X-Ray and Electronmicroscopic InvestigationsIn the system La2O3/Ta2O5 a new ternary compound LaTa7O19 could be prepared by chemical transport in a temperature gradient T2 → T1 (1120 → 1020°C; Cl2 was added). LaTa7O19 is hexagonal, space group P6 with the lattice constants a = 6.236 and c = 19.995 Å. In the structure double layers of pentagonal TaO7-bipyramids are recognizable perpendicular to [001]-direction. They alternate with a single layer consisting of La—O and Ta—O coordination polyhedra. Images of the structure were made with high resolution transmission electron microscopy along the [001]-direction. Despite the length of the axis the computer simulation based on the multi-slice method agreed well with the experimental images.
    Notes: Im System La2O3/Ta2O5 erhielten wir die neue ternäre Verbindung LaTa7O19 durch chemischen Transport im Temperaturgefälle T2 → T1 (1120 → 1020°C; Zusatz von Cl2). LaTa7O19 kristallisiert hexagonal in der Raumgruppe P6 mit den Gitterkonstanten a = 6,236 und c = 19,995 Å. In der Struktur erkennt man senkrecht zu [001] Doppelschichten von pentagonalen TaO7-Bipyramiden, die jeweils durch eine Einzelschicht aus La—O- und Ta—O-Koordinationspolyedern getrennt sind. Mit der hochauflösenden Durchstrahlungselektronenmikroskopie konnten Abbildungen der Struktur in [001]-Richtung erhalten werden. Trotz der Länge dieser Achse stimmte die rechnerische Simulation auf der Grundlage der „Multi-Slice-Methode“ mit den experimentellen Abbildungen gut überein.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparation and Structure of LaTa3O9. X-Ray and Electronmicroscopic InvestigationsIn the system La2O3/Ta2O5 a new ternary compound LaTa3O9 could be prepared by chemical transport in a temperature gradient T2 → T1 (1100 → 1040°C; Cl2 was added). LaTa3O9 is orthorhombic, space group Pnma-D2h16 with the lattice constants a = 6.595, b = 7.664, and c = 12.481 Å. In the structure ribbons of pentagonal TaO7-bipyramids are recognizable parallel to the a-direction. These ribbons are connected with each other in the (010) plane by TaO6-octahedra. The tunnels formed in this way are occupied by La atoms. High resolution transmission electron microscopy images of the structure were made along the [010] direction. They were interpreted by using images calculated on the basis of the multi-slice method.
    Notes: Durch chemischen Transport im Temperaturgefälle T2 → T1 (1100 → 1040°C; P(Cl2; 20°C) = 1 atm) wurde die neue ternäre Verbindung LaTa3O9 erhalten, die orthorhombisch in der Raumgruppe Pnma-D2h16 mit den Gitterkonstanten a = 6,595, b = 7,664, und c = 12,481 Å kristallisiert. In der Struktur erkennt man in a-Richtung verlaufende Bänder aus kantenverknüpften pentagonalen TaO7-Bipyramiden; die Bänder sind miteinander in der (010)-Ebene durch TaO6-Oktaeder verbunden. In den dadurch entstehenden Kanälen befinden sich die La-Teilchen. Mit der hochauflösenden Durchstrahlungselektronenmikroskopie konnten Abbildungen der Struktur in [010]-Richtung erhalten werden. Obwohl die Kanäle die La-Teilchen enthalten, erscheinen sie auf den experimentellen Aufnahmen hell und sind dadurch gut erkennbar. Zur Interpretation dienten Abbildungen, die eine rechnerische Simulation auf der Grundlage der „Multi-Slice-Methode“ liefert.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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