Acoustic properties of (Pb0.9La0.1)(Zr0.65Ti0.35)O3 relaxor ferroelectric ceramics studied by Brillouin scattering

Journal of Applied Physics

et al. 2008

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of which the spontaneous polarization is directed along the polar c axis. Large acoustic anisotropy between the two elastic constants C 11 and C 33 have been observed from all samples. C 33 exhibits a significant softening on approaching the diffuse phase transition temperature from high-temperature side while C 11 does not show any substantial change in the same temperature range. This softening is accompanied by substantial growth of hypersonic damping, appearance and growth of central peak ͑CP͒, and slowing down of the relevant dynamics of CP represented by the reducing half width. All these results indicate that the lattice motions along the c axis couple strongly to the one-component order parameter of the polar nanoregions ͑PNRs͒ or precursor polar clusters which form and grow below a certain temperature in the paraelectric phase. The inverse dielectric constant measured along the c axis of SBN61 and KNSBN:Cu can be described by two linear regions divided by a crossover temperature at which the change in the magnitude of dipole moments and the strength of the dipole couplings are expected due to the formation of PNRs. C 33 of SBN61 becomes continuously softened upon cooling even when the temperature crosses the Burns temperature T B at which PNRs begin to appear. It may suggest that additional relaxation process other than that of PNRs may exist at high temperatures above T B and couple to the longitudinal acoustic waves propagating along the polar axis. Recent observation of a single-particle relaxation at high temperatures and its transformation into a collective relaxation of PNRs by dielectric spectroscopy ͓Belous et al., J. Appl. Phys. 102, 014111 ͑2007͔͒ might be related to the anomalous acoustic behavior of SBN61 observed above T B .

Section: Acoustic Behavior Of Sbn61 Above T Bsupporting

confidence: 88%

Section: A Acoustic Anisotropymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Acoustic anisotropy in uniaxial tungsten bronze ferroelectric single crystals studied by Brillouin light scattering

Lushnikov

Journal of Applied Physics

et al. 2008

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“…The correlation between T B and the anomaly in B of LA phonon has also been observed in Pb͑Mg 1/3 Ta 2/3 ͒O 3 and lanthanum lead zirconate titanate relaxors. 17,18 After reaching a maximum, significant softening in B begins to occur at ϳ570 and ϳ510 K for LA and TA modes, respectively. The softening of B of both modes is accompanied by the increase of acoustic damping represented by the phonon linewidth.…”

mentioning

confidence: 99%

Correlation between the dynamics of polar nanoregions and temperature evolution of central peaks in Pb[(Zn1∕3Nb2∕3)0.91Ti0.09]O3 ferroelectric relaxors

Applied Physics Letters

Kojima

2007

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Acoustic properties of Pb͓͑Zn 1/3 Nb 2/3 ͒ 0.91 Ti 0.09 ͔O 3 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 T B ϳ 730 K. Upon cooling, acoustic properties exhibited significant changes at about 550 K 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 T B , 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.

“…For comparison, ⌬ and FWHM of PMN measured on cooling are also plotted in the same figure. ⌬ of PZN-4.5%PT, which corresponds to the elastic stiffness coefficient c 11 , measured on cooling exhibits a broad minimum near ϳ395 K. This behavior has also been observed in other typical relaxor crystals. [11][12][13][19][20][21][22] The interactions of the PNRs inherently present in relaxors with the strain induced by the acoustic wave through the electrostrictive coupling are believed to be responsible for the softening of the Brillouin shift as the temperature decreases from high temperature to the diffuse phase transition point. 23 The quadratic coupling between the polarization and deformation usually accompanies order parameter fluctuations, which are responsible for the growth of acoustic damping on cooling.…”

mentioning

confidence: 99%

Hysteresis in acoustic properties of ferroelectric relaxor Pb[(Zn1∕3Nb2∕3)0.955Ti0.045]O3 single crystals studied by Brillouin and dielectric spectroscopies

Journal of Applied Physics

Kojima

et al. 2006

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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.