Premium
A Raman spectroscopic study of a single crystal of sodium ammonium selenate dihydrate, NaNH 4 SeO 4 ·2H 2 O over the temperature range 293–89 K
Author(s) -
Fawcett V.,
Long D. A.,
Sankaranarayanan V. N.
Publication year - 1975
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1250030208
Subject(s) - raman spectroscopy , phase transition , atmospheric temperature range , chemistry , ferroelectricity , single crystal , selenate , ion , crystallography , crystal (programming language) , soft modes , analytical chemistry (journal) , dielectric , materials science , inorganic chemistry , selenium , condensed matter physics , programming language , physics , optoelectronics , organic chemistry , meteorology , computer science , optics , chromatography
The Raman spectra of single crystals of NaNH 4 SeO 4 ·2H 2 O in various orientations are reported for the temperature range 293–89 K. NaNH 4 SeO 4 ·2H 2 O undergoes a transition at 180 K from a paraelectric phase to a ferroelectric phase. The changes in the Raman spectra as the crystal is cooled support the evidence from magnetic resonance studies that the transition is of a displacive type with an associated overdamped soft mode. Ordering of the NH 4 +ions but not of the complete crystal occurs at the transition temperature.