Hysteresis in acoustic properties of ferroelectric relaxor Pb[(Zn1/3Nb2/3)0.955Ti0.045]O3 single crystals studied by Brillouin and dielectric spectroscopies (original) (raw)
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Journal of Applied Physics, 2006
Acoustic and dielectric properties of Pb͓͑Zn 1/3 Nb 2/3 ͒ 1−x Ti x ͔O 3 ͑PZN-xPT͒ single crystals with x = 0.045 have been studied by the high-resolution micro-Brillouin scattering and dielectric spectroscopy in a wide temperature range. The softening of the Brillouin shift and the increase of dielectric relaxation time upon cooling indicated the formation of polar nanoregions ͑PNRs͒ and the slowing down of their dynamics. In contrast to the acoustic properties of typical model relaxors such as lead magnesioniobate, the change in the Brillouin shift near its minimum became sharper on heating compared to the change on cooling, pointing to the clear existence of hysteresis in the dynamics of the diffuse phase transition in PZN-4.5%PT. Since the number of PNRs will increase upon cooling, it may be expected that the kinetics of the phase transition would become slower, the lower the transition temperature resulting in the more sluggish, broad feature of the Brillouin shift observed during cooling. This result may indicate that the number and size of polar nanoregions, which are dependent on temperature, play an important role in the development of the mesoscopic ferroelectric order in PZN-4.5%PT.
2013
The precursor dynamics of ferroelectric phase transitions in relaxor-based ferroelectric (1 − x) Pb(Zn 1/3 Nb 2/3)O 3-xPbTiO 3 single crystals, with x = 0.07, 0.10, and 0.12, were investigated using inelastic light scattering from a longitudinal acoustic phonon. An acoustic anomaly in a broad temperature range, which is characteristic of relaxor ferroelectrics, was observed. We describe the anomalies in the paraelectric phase by assuming local piezoelectric coupling inside polar nanoregions, which are surrounded by a nonpolar matrix. On the basis of local piezoelectric coupling, a relaxation time τ and a dynamic characteristic length L of the order-parameter (polarization) fluctuations were determined to be in the order of 10 −13 s and 10 −9 m, respectively. The τ and L values increase sharply upon cooling from high temperatures but more gradually below the intermediate temperature T * (=493 − 510 K). This result implies that the local polarization fluctuations grow rapidly upon cooling down to above T * and the growth rate decreases below T *. The inflexion point of this growth process in the paraelectric phase is related to the characteristic properties of relaxor-based solid solutions.
Journal of Applied Physics, 2016
The thermal hysteresis has been studied by Brillouin scattering in the relaxor ferroelectric (1 À x)Pb(Zn 1/3 Nb 2/3)O 3-xPbTiO 3 with x ¼ 0.055 (i.e., below the morphotropic phase boundary composition x $ 0.08). On heating from room temperature, the first order rhombohedral to tetragonal phase transition occurs at T R-T ¼ 397 K, then the first order tetragonal to cubic transition occurs at T T-C ¼ 425 K. However, on cooling from high temperature, only the diffusive phase transition was observed around T C-R ¼ 401 K. Such anomalous thermal hysteresis is attributed to the metastable nonequilibrium states induced by supercooling due to quenching of nano-domains by the random electric fields of the B-site charge disorder. V
Physical Review B, 2008
Temperature dependence of acoustic behaviors and quasielastic central peaks ͑CPs͒ of Pb͓͑Zn 1/3 Nb 2/3 ͒ x Ti 1−x ͔O 3 ͑PZN-xPT͒ single crystals with x = 4.5% and 9% have been investigated in a temperature range of 300-900 K by using the Brillouin light scattering. The temperature dependence of the C 11 elastic constant of both crystals showed a deviation from normal lattice anharmonicity at the Burns temperature ͑T B ͒ of about 730 K upon cooling, indicating the onset of the electrostrictive coupling between the polar nanoregions ͑PNRs͒ and the longitudinal acoustic ͑LA͒ waves. Upon further cooling, depolarized CP began to appear at a certain temperature ͑T d ͒ located in 500-550 K, which was accompanied by substantial softening of the C 44 elastic constant below this temperature suggesting anisotropic electrostrictive coupling between PNRs and the two acoustic waves. In addition, the onset of significant increase in the acoustic damping of both acoustic waves at T d could be seen from the temperature dependence of the linewidth of Brillouin doublets. These results suggested that electrostrictive coupling of the strain to the square of the local polarization of PNRs and the resultant order-parameter fluctuations are enhanced not at T B but at a much lower temperature of T d , which may be ascribed to a local structural transformation occurring in PNRs at T d. This suggestion is consistent with recent studies on PZN-xPT single crystals reporting the appearance of strong acoustic emission signals ͓M. Roth et al., Phys. Rev. Lett. 98, 265701 ͑2007͔͒ and substantial changes in the Raman spectrum ͓O. Svitelskiy, Phys. Rev. B 72, 172106 ͑2005͔͒ at almost the same temperature. From the comparison of the present results to those of two typical relaxors, Pb͑Mg 1/3 Nb 2/3 ͒O 3 and Pb͑Mg 1/3 Ta 2/3 ͒O 3 , it was suggested that the existence of an intermediate characteristic temperature T d below T B may be considered as a more common characteristic in the temperature evolution of PNRs of relaxor ferroelectrics.
Ferroelectrics Letters Section, 2001
Polarization-electric field (P-E) hysteresis loops and domain structures have been measured as a function of temperature in relaxor-based ferroelectric single crystal (PbZn,/3Nb2/303)0.9~j(PbTi03)o.o~s (PZN-8.5%PT). In order of increasing temperature, PZN-8.5%PT undergoes successive phase transitions: rhombohedra1 phase (below-375 K) + coexistence of rhombohedral and tetragonal phases (between-375 and-390 K)-f tetragonal phase (between-390 and-420 K)-+ coexistence of tetragonal and cubic phases (between-420 and-460 K)-+ cubic phase (above-460 K). Phase coexistence suggests an inhomogeneous distribution of Ti4+ concentration in the PZN-8.5%PT crystal.
Journal of Applied Physics, 2012
Phase transition behaviors of [001]-oriented Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) single crystals were studied under unpoled and [001]-poled conditions by Brillouin light scattering and dielectric spectroscopies. The unpoled crystal showed a diffused elastic anomaly accompanied by substantial dielectric dispersion, which were associated with the temperature evolution of polar nanoregions represented by the excitation of strong central peaks. The poled crystal exhibited two-step changes in both dielectric and elastic properties, which were attributed to the successive phase transitions from rhombohedral to tetragonal, and then from tetragonal to cubic phase upon heating. The high-temperature tetragonal-cubic phase transition remained diffused with dielectric dispersion due to local random fields inherent in relaxors. The transverse acoustic mode disappeared at the rhombohedral-tetragonal phase transition indicating a clear symmetry change.
Applied Physics Letters, 2007
Acoustic properties of Pb[(Zn1∕3Nb2∕3)0.91Ti0.09]O3 have been investigated in a wide temperature range. The sound velocity of acoustic phonons showed a deviation from its high-temperature linear behavior at the Burns temperature TB∼730K. Upon cooling, acoustic properties exhibited significant changes at about 550K in polarization state and width of the central peak in addition to changes in frequency and damping of acoustic phonons. This finding suggests that, besides TB, another intermediate characteristic temperature exists in the evolution of relaxor dynamics, which might be related to the formation of long-lived polar nanoregions and associated local strain fields.