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Inelastic light scattering studies of diffuse phase transition in ferroelectric Sr 1.9 Ca 0.1 NaNb 5 O 15 thin films
Author(s) -
Liu W. C.,
Zhou W.,
Sooryakumar R.,
Mak C. L.
Publication year - 2012
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.3018
Subject(s) - ferroelectricity , curie temperature , raman spectroscopy , relaxation (psychology) , dielectric , atmospheric temperature range , brillouin scattering , condensed matter physics , raman scattering , materials science , phase transition , analytical chemistry (journal) , full width at half maximum , permittivity , brillouin zone , nuclear magnetic resonance , phase (matter) , chemistry , optics , physics , thermodynamics , ferromagnetism , optoelectronics , psychology , social psychology , organic chemistry , chromatography , optical fiber
The dynamic behavior of highly oriented ferroelectric Sr 1.9 Ca 0.1 NaNb 5 O 15 thin films has been investigated by Brillouin light scattering over a wide temperature range between 25 and 450 °C. The temperature variations of the full‐width at half‐maximum (FWHM) of the central peak (CP) are found to exhibit marked changes around the Curie temperature ( T c = 246 °C). The CP reveals a relaxational mode behavior, which is attributed to thermally activated fast relaxation of polar nanoregions (PNRs). The width of the CP decreases steadily upon cooling from ∼400 °C to T c and shows little subsequent change within the ferroelectric state, indicating an increase of the number of PNRs and a slowing down of their dynamics. By using a modified superparaelectric model, the activation energy ( H 0 ) of the relaxation processes and the Burns temperature ( T B ) are determined to be 2939 and 385 °C, respectively. The evidence for this diffuse phase transition provided by Brillouin scattering is in agreement with results obtained from the temperature‐dependent dielectric permittivity, refractive index, and Raman spectra. Copyright © 2011 John Wiley & Sons, Ltd.