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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 622 (1996), S. 589-592 
    ISSN: 0044-2313
    Keywords: ternary aluminium germanides ; yttrium ; rare earth ; crystal structure ; band calculations ; electron localization ; superconductivity ; zintl-compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Y2AlGe3 - a Superconductive Metallic Zintl CompoundY2AlGe3 was prepared by heating the elements (950°C) and investigated by means of single-crystal X-ray methods. The compound crystallizes in a new structure (Pnma; a = 6.785(1) Å, b = 4.189(1) Å, c = 17.676(2) Å; Z = 4) with a three-dimensional framework of Al and Ge atoms and with Y in the cavities. The Al atoms are surrounded tetrahedrally by Ge atoms, which are arranged in the form of planar (Ge2-)∞ chains and isolated from each other respectively. Although Y2AlGe3 is a metallic conductor and no valence compound, it achieves the structural requirements of Zintl's concept. This picture is supported by electrondensity and ELF calculations, which reveals covalent Al—Ge and Ge—Ge bondings, therefore Y2AlGe3 is interpreted as a metallic Zintl-Compound, down-playing the metallic propertys. Y2AlGe3 becomes superconductively at 4.5 K. Isotypic compounds are found for Ln2AlGe3 with Ln = Dy, Ho, Er, and Tm (For lattice constants see “Inhaltsübersicht”).
    Notes: Y2AlGe3 wurde durch Erhitzen der Elemente auf 950°C dargestellt und röntgenographisch mit Einkristallmethoden untersucht. Die Verbindung kristallisiert in einer neuen Struktur (Pnma; a = 6,785(1) Å, b = 4,189(1) Å, c = 17,676(2) Å; Z = 4) mit einem dreidimensionalen Gerüst aus Al- und Ge-Atomen, in dessen Lücken sich die Y-Atome befinden. Al ist tetraedrisch von Ge-Atomen umgeben, die ihrerseits ebene (Ge2-)∞-Ketten bilden bzw. voneinander isoliert vorliegen. Trotz nicht valenzmäßiger Zusammensetzung gemäß Y3+ Y3+ Al3+ (Ge2)4- Ge4- und metallischer Leitfähigkeit weist Y2AlGe3 die Strukturmerkmale einer Zintl-Verbindung auf. Diese Interpretation wird gestützt durch Berechnungen der Elektronendichte und Elektronenlokalisierungsfunktion (ELF), die kovalente Ge—Ge- und Al—Ge-Bindungen zeigen. Die Verbindung wird demnach als metallische Zintl-Verbindung angesehen. Y2AlGe3 wird bei 4,5 K supraleitend. Isotyp kristallisieren die Verbindungen Ln2AlGe3 (Ln = Dy—Tm) mit den Gitterkonstanten: Dy2AlGe3: a = 6,785(3) Å, b = 4,171(1) Å, c = 17,665(7) Å Ho2AlGe3: a = 6,753(2) Å, b = 4,158(1) Å, c = 17,580(4) Å Er2AlGe3: a = 6,732(1) Å, b = 4,147(3) Å, c = 17,517(3) Å Tm2AlGe3: a = 6,706(3) Å, b = 4,061(5) Å, c = 17,550(9) Å.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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