Competing antiferroelectric and ferroelectric interactions in NaNbO{sub 3}: Neutron diffraction and theoretical studies
- Solid State Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)
Neutron diffraction studies using powder samples have been used to understand the complex sequence of low temperature phase transitions of NaNbO{sub 3} in the temperature range from 12 to 350 K. Detailed Rietveld analysis of the diffraction data reveals that the antiferroelectric to ferroelectric phase transition occurs on cooling around 73 K, while the reverse ferroelectric to antiferroelectric transition occurs on heating at 245 K. However, the former transformation is not complete until it reaches 12 K and there is unambiguous evidence for the presence of the ferroelectric R3c phase coexisting with an antiferroelectic phase (Pbcm) over a wide range of temperatures. The coexisting phases and reported anomalous smearing of the dielectric response akin to dipole glasses and relaxors observed in the same temperature range are consistent with competing ferroelectric and antiferroelectric interactions in NaNbO{sub 3}. We have carried out theoretical lattice dynamical calculations which reveal that the free energies of the antiferroelectric Pbcm and ferroelectric R3c phases are nearly identical over a wide range of temperature. The small energy difference between the two phases is of interest as it explains the observed coexistence of these phases over a wide range of temperature. The computed double well depths and energy barriers from paraelectric Pm3m to antiferroelectric Pbcm and ferroelectric R3c phases in NaNbO{sub 3} are also quite similar, although the ferroelectric R3c phase has a slightly lower energy.
- OSTI ID:
- 20946383
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 76, Issue 2; Other Information: DOI: 10.1103/PhysRevB.76.024110; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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