Broad-band dielectric spectroscopy of Ba
2NaNb
5O
15 single crystal |
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| Authors: | E Buixaderas V Porokhonskyy A Paskhin M Savinov J Petzelt |
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| Institution: | (1) Institute of Physics, ASCR, Na Slovance 2, 182 21 Prague 8, Czech Republic, CZ |
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| Abstract: | Barium sodium niobate (BNN) single crystals are studied by IR spectroscopy, time-domain THz transmission spectroscopy, HF
coaxial wave-guide technique and LF dielectric spectroscopy to cover the frequency range 102-1014 Hz in a wide temperature interval. The dielectric response parallel and perpendicular to the polar c-axis is discussed. The ferroelectric transition at T
c
= 830 K is driven by a relaxational soft mode coupled with another central-mode type relaxation which both gradually disappear
on cooling in the ferroelectric phase. Below T
i
the parameters of the expected IR active amplitudon were estimated. The low-temperature permittivity increase on cooling
for the
field direction has been explained by an incipient proper ferroelectric-ferroelastic transition driven by an IR and Raman
active B2-symmetry soft mode.
Received 24 August 2002 Published online 19 December 2002
RID="a"
ID="a"e-mail: buixader@fzu.cz |
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| Keywords: | PACS 63 20 -e Phonons in crystal lattices – 64 70 Rh Commensurate-incommensurate transitions – 77 80 Bh Phase transitions and Curie point – 77 84 -s Dielectric piezoelectric ferroelectric and antiferroelectric materials |
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