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Raman Scattering Study of Relaxor Ferroelectric Pb(Sc1/2Nb1/2)O3 Crystals
Kohei Suzuki,SeijiKojima,Muhtar Ahart,Yonghong Bing,Zuo-Guang Ye 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.8
The effects of B-site ordering and vacancies were studied in the relaxor ferroelectric Pb(Sc1/2Nb1/2)O3 (PSN) family by using Raman scattering spectroscopy. Differences with Raman spectra and the depolarization ratios were clearly observed among B-site disordered PSN (PSN-D),B-site ordered with lead/oxygen vacancies PSN (PSN-OV ), and 0.7Pb(Sc1/2Nb1/2)O3-0.3PbTiO3(PSN-30PT) single crystals. The temperature dependence of the depolarization ratio of PSN-30PT was also studied to clarify the ferroelectric phase transitions and the polarization fluctuations in the polar nanoregions.
Ko, Jae-Hyeon,Kim, Tae Hyun,Kojima, Seiji,Bokov, Alexei A,Ye, Zuo-Guang IOP Pub 2010 Journal of Physics, Condensed Matter Vol.22 No.48
<P>A Brillouin spectroscopic investigation was carried out on PMN–55%PT single crystals, which are known to have no chemically ordered regions and undergo a well-defined structural phase transition at <I>T</I><SUB>C</SUB> ∼ 521 K. The longitudinal and transverse sound velocities probed on a right-angle scattering geometry exhibited a remarkable softening and increasing hypersonic damping on approaching <I>T</I><SUB>C</SUB> from <I>T</I><SUB>B</SUB> ∼ 610 K that was characterized by the deviation of the dielectric permittivity from the high-temperature Curie–Weiss behavior. The acoustic anomalies of the longitudinal acoustic mode at the backward scattering were more substantial than those observed at the right-angle scattering, which could be understood in the framework of normal acoustic dispersion considering the difference in the acoustic frequency. The softening of the transverse sound velocity was more significant than that of the longitudinal one upon cooling toward <I>T</I><SUB>C</SUB>, suggesting that this acoustic anomaly may be related to the local rhombohedral transformation, occurring in polar nano-regions (PNRs). The observed acoustic behaviors combined with the central peak dynamics clearly indicated the existence of dynamic polar nano-regions in PMN–55%PT where there are no chemically ordered regions, and seem to suggest that the order parameter fluctuations due to two kinds of coupling contribute to the acoustic anomalies in the temperature range of <I>T</I><SUB>C</SUB> ∼ <I>T</I><SUB>B</SUB>: electrostrictive coupling between the acoustic waves and the dynamic PNRs, and linear coupling between the acoustic waves and the precursor polar clusters, i.e., the ordering unit responsible for the order–disorder-type slowing down behavior probed by the central peak. </P>
고재현,Anwar Hushur,Bryan C. Sih,Do Han Kim,Jong Pil Kim,Min-Su Jang,Seiji Kojima,Zuo-Guang Ye 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV
Elastic properties of bismuth layered perovskite compounds, LaxBi4..xTi3O12 (LBT-x) and SrBi2Ta2O9 (SBT), were examined at room temperature by Brillouin scattering. Elastic stiness coecients, c33 and c44, dened in the pseudotetragonal symmetry, were obtained. The longitudinal sound velocities propagating along the c axis, were 3985 m/s and 3118 m/s for the pure bismuth titanate (BTO) and SBT, respectively. The sound velocity of SBT is very slow and is believed to be related with the weak interlayer bonding of this layer-structure compound. A simple linear chain model showed that the dierence in the sound velocity between BTO and SBT is mainly due to the dierence in the c axis lattice constant. The sound velocity of LBT-x increased slightly with the increase of x, while c33 seems to be insensitive to x.