Low-temperature phase transitions in barium sodium niobate

Filipic, C. and Kutnjak, Z. and Lortz, R. and Torres-Pardo, A. and Dawber, M. and Scott, J. F. (2007) Low-temperature phase transitions in barium sodium niobate. Journal of Physics Condensed Matter, 19. p. 236206. DOI https://doi.org/10.1088/0953-8984/19/23/236206

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We present dielectric and specific heat data on barium sodium niobate (Ba2Na1−xNb5O15) from 4 to 460 K with an emphasis on the low-temperature incommensurate phase transitions. This material is ferroelectric below Tc(x) = ca 830 K, and the reciprocal dielectric constant extrapolates to zero near this temperature throughout the low-temperature phases, which involve distortions within the non-polar plane and do not affect significantly the ferroelectric properties. The transition from orthorhombic to incommensurate near 113 K has highly frequency-dispersive dynamics, reminiscent of those in relaxors, and an activation energy of 0.42 eV. The 'lock-in' transition near 30 K to a tetragonal structure with an enlarged unit cell has been controversial, with studies in Japan (1996, 1997) and the Czech Republic (2004) not finding the P4nc phase predicted by Schneck (1982) and measured directly via spallation neutron scattering by Scott et al (1990); our new studies show that this transition is limited by kinetics and requires very slow cooling for detection.

Item Type: Article
Uncontrolled Keywords: 2007 AREP IA54 2007 P
Subjects: 03 - Mineral Sciences
Divisions: 03 - Mineral Sciences
Journal or Publication Title: Journal of Physics Condensed Matter
Volume: 19
Page Range: p. 236206
Identification Number: https://doi.org/10.1088/0953-8984/19/23/236206
Depositing User: Sarah Humbert
Date Deposited: 16 Feb 2009 13:02
Last Modified: 23 Jul 2013 10:07
URI: http://eprints.esc.cam.ac.uk/id/eprint/292

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