Soft Acoustic Mode in the Ferroelectric Phase Transition of Hexagonal Barium Titanate

1995 ◽  
Vol 74 (11) ◽  
pp. 2126-2129 ◽  
Author(s):  
M. Yamaguchi ◽  
K. Inoue ◽  
T. Yagi ◽  
Y. Akishige
Keyword(s):  
Phase Transition ◽  
Barium Titanate ◽  
Ferroelectric Phase Transition ◽  
Ferroelectric Phase ◽  
Acoustic Mode

Uniaxial mechanical stresses and their influence on the parameters of the ferroelectric phase transition in pressure-treated barium titanate

2017 ◽  
Vol 508 (1) ◽  
pp. 161-166 ◽  
Author(s):  
A. M. Pugachev ◽  
I. V. Zaytseva ◽  
A. S. Krylov ◽  
V. K. Malinovsky ◽  
N. V. Surovtsev ◽  
...  
Keyword(s):  
Phase Transition ◽  
Barium Titanate ◽  
Ferroelectric Phase Transition ◽  
Ferroelectric Phase ◽  
Mechanical Stresses

Soft-phonon Dynamics in the Isotopically Induced Ferroelectric Phase Transition of Strontium Titanate

2002 ◽  
Vol 718 ◽  
Author(s):  
Toshirou Yagi ◽  
Masaru Kasahara ◽  
Yuhji Tsujimi ◽  
Hiroki Hasebe ◽  
Masashi Yamaguchi ◽  
...  
Keyword(s):  
Phase Transition ◽  
Ferroelectric Phase Transition ◽  
Ferroelectric Phase ◽  
Brillouin Scattering ◽  
Spectral Component ◽  
Local Symmetry ◽  
Central Peak ◽  
Anomalous Behavior ◽  
Acoustic Mode ◽  
Coupling Mechanism

Abtract:The ferroelectric phase transition of SrTi18O3 (STO8), where the quantum paraelectricity is reduced by the exchange of oxygen atoms 16O for its isotope 18O, has been studied by both Brillouin scattering and Raman scattering. The Brillouin spectra of the c44 and c66 modes in the paraelectric-tetragonal phase show anomalous behavior in the temperature region several degrees above TC accompanied by a central peak. The characteristic shape of the central peak indicates a coupling mechanism between the acoustic mode and an overdamped soft polar mode. Though the ferroelectric soft A2u mode is Raman inactive in the paraelectric phase, it has been observed in the x(yz)-x geometry indicating a local symmetry breaking above TC. Existence of the ferroelectric micro region in the temperature range far above TC is confirmed by the broad spectral component. The soft mode dynamics is concluded in the phase transition of STO18. The doublet spectrum is observed without any of considerable change by the isotope exchange.

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