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Study of Order‐Disorder in Rock‐Salt‐Related Structures by Infrared Spectroscopy
Author(s) -
MOORE RAYMOND K.,
WHITE WILLIAM B.
Publication year - 1970
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1970.tb12041.x
Subject(s) - tetragonal crystal system , raman spectroscopy , infrared spectroscopy , infrared , chemistry , spectral line , crystal structure , polarization (electrochemistry) , crystallography , optics , physics , organic chemistry , astronomy
Infrared spectra were determined for a series of oxides related by ordering and distortion to the rock‐salt structure. The expected spectrum of the tetragonal 1:1 ordering (space group D 4h 19 ) contains 5 ir‐active and 8 Raman‐active bands. For the trigonally distorted structure (space group D 3d 5 ) factor group calculations yield 4 ir and 2 Raman modes. The expected additional structure appears in the spectra of the tetragonal materials but is broadened and washed out by the long‐range polarization field. The spectra of the trigonal materials contain twice the predicted number of modes. The broadened bands of the 6‐coordinated structures are compared with the sharp spectra of 4‐coordinated γ‐LiAlO 2 .