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Vibrational study of the paraelectric superionic phase transition in ammonium hydrogenselenates, NH 4 HSeO 4 and ND 4 DSeO 4
Author(s) -
Pasquier B.,
Le Calvé N.,
Rozycki A.,
Novak A.
Publication year - 1990
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.1250210802
Subject(s) - phase (matter) , ion , raman spectroscopy , hydrogen bond , ammonium , crystallography , chemistry , phase transition , atmospheric temperature range , infrared spectroscopy , dielectric , materials science , molecule , condensed matter physics , physics , thermodynamics , organic chemistry , optoelectronics , optics
Abstract Raman and infrared spectra of the room‐temperature ‘paraelectric’ (II) and high‐temperature (I) superionic phases of NH 4 HSeO 4 and ND 4 DSeO 4 were investigated at different temperatures in the range 300–450 K. A new intermediate phase I′ is identified on cooling phase I. A complete assignment of the bands of phase II is given and the spectroscopic manifestations of the structural disorder due to both the statistical distribution of OH … O protons and orientational disorder of ammonium ions were studied. In the superionic phase I infinite (HSeO 4 − ) n chains are broken and open dimers appear to be formed. There is increasing orientational disorder of both ammonium and HSeO 4 − ions resulting in a plastic state. Hydrogen bonding in various phases is discussed.