Order-disorder nature of ferroelectric BaTi2O5

Abstract

Ferroelectric single crystals of BaTi 2 O 5 have been studied in detail by Raman and high-resolution micro-Brillouin scattering with a focus on the central component of the relaxation mode over a wide temperature range ͑20-600°C͒. A relaxation mode has been clearly observed in these single crystals. The temperature dependences of the relaxation time and integrated intensity of the relaxation mode are well reproduced by the extended semiclassical tunneling model. The ferroelectric phase transition shows, at least near the vicinity of T c , an order-disorder nature. Our results indicate that the spontaneous polarization mainly resulted from the dynamic disorder of the Ti ions in the octahedra along the polar b axis of BaTi 2 O 5 .

Ferroelectric phase transition of stoichiometric lithium tantalate studied by Raman, Brillouin, and neutron scattering

“…Such CP was reported on Raman scattering studies of several classical pure and mixed perovskite compounds such as KNbO 3 , BaTiO 3 , and KTa 1−x Nb x O 3 , 37,38 and also on Brillouin scattering of the new ferroelectric BaTi 2 O 5 , which shows a typical critical slowing down of an order-disorder phase transition. 43,44 Such a CP has a Lorentzian-like shape centered at the zerofrequency shift that is a typical feature of a Debye relaxation.…”

Preparation of ferroelectric BaTi2O5 thin films on Pt(111)/Ti/SiO2/Si substrates by pulsed laser deposition

“…Fig. 2 shows the Raman spectra of the films prepared at [15,16] were clearly observed. Except for the band of Si (521 cm −1 ) from the substrate, almost all the bands of the films were in good agreement with those of the BaTi 2 O 5 target, and no characteristic bands of other BaO-TiO 2 compounds, e.g., BaTiO 3 (515 cm −1 ) and Ba 6 Ti 17 O 40 (630 cm −1 ), were identified.…”

High-resolution temperature-dependent Brillouin scattering studies of ferroelectricK3Nb3O6(BMączka1, Hanuza2, Kojima3 2008Phys. Rev. B

“…In this case, clear anomalies in intensity and decrease in the FWHM should be observed when the phase transition temperature is approached from below. 19,34,35 Weak anomaly in intensity near T 3 for the EЉ-symmetry CP, the observed temperature dependence of the FWHM of the EЉ-symmetry CP near T 4 and T 3 , as well as the temperature dependence of the FWHM of the broad Fig. 7͒ could be explained as arising from the polarization fluctuations ͑see discussion below͒.…”

“…Such phenomena may also appear in the absence of any phase transitions and are often observed in superionic conductors. [14][15][16][17] Relaxation modes may give rise to a quasielastic light scattering, i.e., the so-called central peaks ͑CPs͒, [14][15][16][17][18][19] and analysis of the observed CPs may provide an evidence that a studied material exhibits superionic properties. It will be shown in the present paper that KNBO shows the presence of very clear CPs.…”