Central peaks, acoustic modes, and the dynamics of polar nanoregions inPb[(Zn1∕3Nb2∕3)xTi1−x]O3single crystals studied by Brillouin spectroscopy (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.
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.
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.
Journal of Physics: Condensed Matter, 2010
Oriented {100}-, {110}-, and {111}-cuts of Pb 0.78 Ba 0.22 Sc 0.5 Ta 0.5 O 3 single crystals have been studied by means of the acoustic emission (AE) method during their thermal cycling in the temperature range of 300-600 K. For all crystal orientations pronounced AE signals have been detected near 490 K, which corresponds to the intermediate temperature T *. However, the highest AE count rate has been detected from {110}-oriented cuts, revealing strong anisotropic coupling between the existing polar species that at T * merge into larger regions of polarization (PNRs). The temperature's hysteresis is revealed to be 15 K, indicating that the transformation processes at T * can be considered as local Martensitic-like ferroelectric transitions inside PNRs. The interplay between PNRs and ultrahigh local strains of perovskite-type relaxor ferroelectrics is discussed.
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.
MRS Proceedings, 2006
ABSTRACTRelaxors (PZN, in particular) is an important class of self-assembled nanostructure composite ferroelectric oxides (or perovskite) materials. The interesting features associated with the nanoregions/nanodomains required to describe these relaxors give rise to the most relevant device related characteristics and peculiar physical properties in these materials. In addition, they possess astronomical property coefficients by themselves or when modified with lead titanate (PT) forming solid solution. In the past, we conducted temperature dependent Raman scattering studies on solid solution (1−x)PZN−xPT relaxors single crystals with varying composition; x = 0.02, 0.085, and 0.11. These studies were performed to obtain relevant information about lattice/phonon dynamics for matching the application criteria such as electromechanical actuators. We showed that the sharp structural phase transition occurs at or near 460 K which is a first-order transition by fitting two spectroscopic ...
Broadband micro-Brillouin scattering spectroscopy of Pb(B 1/3B′ 2/3)O 3-based relaxor ferroelectrics
Current Applied Physics, 2011
The colossal piezoelectric effect of relaxor-based ferroelectrics has attracted much attention due to the technological importance of the conversion between electric and mechanical energies. The mechanism of the significant field effect on piezoelectric properties in this disordered system has become one of the current topics in pure and applied physics. The important key factor in the understanding of relaxors is polar nanoregions (PNRs) which appear at temperatures far above the dielectric maximum or Curie temperature. PNRs play a dominant role in the formation of unique characteristics of relaxors and are regarded to be caused by spatial and dynamic heterogeneity. However, a detailed microscopic picture of their evolution depending on temperature or electric field is still the subject of controversy. The elastic and dynamical properties of the Pb(B1/3B′2/3)O3-type relaxor-based ferroelectrics and their solid solutions with pure ferroelectrics have recently been studied extensively by the broadband micro-Brillouin scattering spectroscopy (BMBS) to clarify the role of PNRs. This paper reviews the recent progress in the understanding of fast dynamics of PNRs of typical relaxor-based ferroelectrics of (1−x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 and (1−x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 in the gigahertz frequency range achieved by using BMBS.