Spectroscopical Investigation of Order-disorder in Some Compounds with Scheelite Structure
Open Access
- 1 June 1974
- journal article
- Published by Walter de Gruyter GmbH in Zeitschrift für Naturforschung B
- Vol. 29 (5-6) , 340-346
- https://doi.org/10.1515/znb-1974-5-609
Abstract
Infrared and Raman spectra have been measured of scheelites with formula ALnW8O8, ALnMo2O8 (A = Li, Na, K; Ln = La, Y), Y2MWO8 M = Ge, Si), Y2GeMoO8 and the zircon Y2SiMoO8 in order to get information about the crystallographic order. The A+ and Ln3+ ions in the scheelites ALnW2O8 and ALnMo2O8 are probably ordered in layers Ln-Ln-A-A perpendicular to the c-axis. The order is short-range only. The degree of order decreases in the sequence K, Na, Li. The compounds Y2MWO8 and Y2GeMoO8 are not ordered, whereas the Si4+ and Mo6+ ions in Y2SiMoO8 are ordered in alternate layers perpendicular to the c-axis. The use of vibrational spectra for the determination of crystallographic order is discussed.Keywords
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