Precursor dynamics in the ferroelectric phase transition of barium titanate single crystals studied by Brillouin light scattering

Abstract

The acoustic anomalies and precursor dynamics of high-quality barium titanate single crystals were investigated by Brillouin light scattering and the birefringence measurements in the paraelectric phase above the cubic-totetragonal ferroelectric phase transition temperature (T c ). Two elastic stiffness coefficients C 11 and C 44 , the related sound velocities, and their absorption coefficients were determined from T c to 400 • C for the first time. The longitudinal acoustic (LA) mode showed a substantial softening over a wide temperature range above T c which was accompanied by a remarkable increase in the acoustic damping as well as growth of central peaks. The broad central peak (CP) exhibited a two-mode and one-mode behavior in the paraelectric and ferroelectric phase, respectively, which was consistent with recent far-infrared reflectivity measurements and first-principle-based calculations [Ponomareva et al., Phys. Rev. B 77, 012102 (2008)]. The acoustic anomalies and CP behavior were correlated with the anomalous birefringence, piezoelectric effect, and the deviation of the Curie-Weiss law observed from the same crystal. This strongly indicates similarity between the dynamics of polar clusters in typical ferroelectrics and the dynamics of polar nanoregions in relaxors, consistent with recent acoustic emission measurements [Dul'kin et al., Appl. Phys. Lett. 97, 032903 (2010)]. The relaxation times estimated from the central peak and the LA mode anomalies exhibited similar temperature dependences with comparable orders of magnitude, indicating that the polarization fluctuations due to the precursor polar clusters couples to the LA mode through density fluctuations. All these anomalies share common microscopic origin, correlated Ti off-centered motions forming polar clusters having local symmetry breaking in the paraelectric phase. The existence of the polar clusters were directly evidenced by the temperature evolution of the precise birefringence map. The narrow central peak within ±5 GHz proposed before was not confirmed to exist in the present study.

Effect of cobalt doping on the dielectric response of Ba0.95Pb0.05TiO3 ceramics

“…9 Deviation degree ΔTcm from the Curie-Weiss law at the frequency of 100 kHz obtained for BT, BPT, BPTC(0.1 %) and BPTC(1 %) ceramics despite the fact that the remnant polarization is not measurable [37]. Brillouin light scattering studies [38,39] showed anomalous changes of acoustic phonons accompanied by the appearance of quasielastic central peak on approaching Tc in the paraelectric phase. Moreover, many theoretical works based on the first-principle calculations and polarizability model [40][41][42] have been done to explain the deviation from Curie-Weiss behavior due to the complex dynamics of the transition.…”

Development of nanoscale polarization fluctuations in relaxor-based (1-x)Pb(Zn1/3Nb2/Tsukada1, Hidaka2, Kojima3 et al. 2013Phys. Rev. BSelf Cite252250View full textAdd to dashboardCite

“…We note that τ in KF-substituted BaTiO 3 , determined in the same way, obeys the critical slowing down, i.e., τ becomes larger and larger toward T C . [31][32][33] The differences in τ between PZN-xPT and KF-substituted BaTiO 3 should reflect the different growing processes of their PNRs, as discussed in Sec. III B.…”

“…5,19,20,[31][32][33]39 From the macroscopic point of view, the difference between them is the appearance of inflexion points in ν B , , ε , and ε . For example, Fig.…”

“…However, ferroelectric materials with disorder, e.g., relaxor ferroelectrics and barium titanate-(BaTiO 3 -) based ferroelectrics show the anomaly in a much wider temperature range. [17][18][19][20]22,[31][32][33] We attribute the anomaly to a piezoelectric coupling inside the noncentrosymmetric disordered regions. Because the local structure inside the PNRs is noncentrosymmetric, 3,12,13 even though the matrix around the PNR is centrosymmetric, the polarization fluctuation can couple linearly with the strain fluctuation.…”

Thermal hysteresis of local instabilities in paraelectric phase of PbZr0.96Sn0.04 O3 single crystals

“…The temperature evolution of this interdependence of the structural and polar soft mode could be responsible for non-classical dependences reported earlier. 22 Similar mechanism can be applicable to PZS. The question remains as to why both in the case of ferroelectric and antiferroelectric transitions this thermal hysteresis takes place.…”