ISSN:
0044-2313
Keywords:
Chromium niobate
;
chemical transport reactions
;
block structure
;
high resolution electron microscopy
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Description / Table of Contents:
Contributions to the Investigation of Inorganic Non-Stoichiometric Compounds. XLIII. Preparation and Electron Microscopic Investigation of (Cr, Nb)12O29Transport experiments in the system Cr/Nb/O yielded the compound (Cr, Nb)12O29 as crystalline green needles. The lattice parameters of the monoclinic cell are a = 31.162(8) Å, b = 3.8324(6) Å, c = 20.579(6) Å, β = 113.22(3)°. (Cr, Nb)12O29 is isotypic with monoclinic Nb12O29 as shown by Guinier diagrams and high resolution transmission electron microscopy. Characteristic structural building elements are [3 × 4]-blocks which are columnar sections from the ReO3 structure. In the real structure one finds numerous defects. Under the influence of the electron beam we observed reversible changes of contrast which indicates that the positions of the M-particles (M = Cr, Nb) have shifted.
Notes:
Grüne, nadelförmige Kristalle von monoklinem (Cr, Nb)12O29 entstanden bei Transportexperimenten im System Cr/Nb/O. Die Gitterparameter a = 31,162(8) Å, b = 3,8324(6) Å, c = 20,579(6) Å, β = 113,22(3)° aus Guinieraufnahmen zeigen ebenso wie Strukturabbildungen mit der hochauflösenden Durchstrahlungselektronenmikroskopie Isotypie zu monoklinem Nb12O29. Auf den Aufnahmen erkennt man als charakteristisches Bauelement [3 × 4]-Blöcke, säulenförmige Ausschnitte aus der ReO3-Struktur, sowie zahlreiche Baufehler. Reversible Veränderungen des Kontrastes unter der Einwirkung des Elektronenstrahls lassen auf Änderungen der M-Positionen (M = Cr, Nb) schließen.
Additional Material:
11 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/zaac.19946200515
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