This paper reviews the recent progress in the understanding of the dynamics of Pb(B_(1/2)B0_(1/2))O_(3)-type relaxor ferroelectrics using of broadband micro-Brillouin scattering spectroscopy,which covers a large frequ...This paper reviews the recent progress in the understanding of the dynamics of Pb(B_(1/2)B0_(1/2))O_(3)-type relaxor ferroelectrics using of broadband micro-Brillouin scattering spectroscopy,which covers a large frequency range from 1 to 1000 GHz by a tandem multi-pass FabryPerot interferometer.In contrast to Pb(B_(1/3)B0_(2/3))O_(3)-type relaxors,there is no frustration on the B-site of perovskite structure and the degree of order of B-site cations depends on heat treatment.Remarkable softening of sound velocity and an intense central peak are observed above the Curie temperature TC owing to the polarization°uctuations in polar nanoregions(PNRs).Unlike the Pb(B_(1/3)B0_(2/3))O_(3)relaxors,Pb(B_(1/2)B'_(1/2))O_(3)does not undergoes a typical diffuse phase transition without lead vacancies on A-site which enhances randomfields.For the(1-x)Pb(B_(1/2)B'_(1/2))O_(3-x)PbTiO_(3)solid solutions,the long range polar order increases as the PbTiO_(3)content increases.Nevertheless,a central peak owing to dynamic PNRs still remains even for the composition near the MPB,and a critical slowing down is clearly observed in the vicinity of TC.展开更多
Room-temperature Raman scattering and x-ray difraction measurements together with first principles calculations were employed to invetigate the behavior of disordered Pb(In_(1/2)Nb_(1/2))O_(3)(PIN)under pressure up to...Room-temperature Raman scattering and x-ray difraction measurements together with first principles calculations were employed to invetigate the behavior of disordered Pb(In_(1/2)Nb_(1/2))O_(3)(PIN)under pressure up to 50GPa.Raman spectra show broad bands but a peak near the 380cm^(-1) increases its intensity with pressure.The linewidth of the band at 550cm^(-1) also increases with pressure,while two of the Raman peaks merge above 6GPa.Above 16 GPa,we observe additional splitting of the band at 50cm^(-1).The pressure evolution of the diffraction patterns for PIN shows obvious Bragg peaks splitting above 16GPa;consistent with a symmetry lowering transition.The transition at 0.5 GPa is identified as a pseudo-cubic to orthorhombic(Pbam)structural change whereas the transition at 16GPa is istructure and associated with changes in linear compresibility and octahedral titling,and the transition at 30 GPa is associated to an orthorhombic to monoclinic change.First-principles calculations indicate that the Pbam structure is ground state with antiferrodisdortion consistent with experiment.展开更多
文摘This paper reviews the recent progress in the understanding of the dynamics of Pb(B_(1/2)B0_(1/2))O_(3)-type relaxor ferroelectrics using of broadband micro-Brillouin scattering spectroscopy,which covers a large frequency range from 1 to 1000 GHz by a tandem multi-pass FabryPerot interferometer.In contrast to Pb(B_(1/3)B0_(2/3))O_(3)-type relaxors,there is no frustration on the B-site of perovskite structure and the degree of order of B-site cations depends on heat treatment.Remarkable softening of sound velocity and an intense central peak are observed above the Curie temperature TC owing to the polarization°uctuations in polar nanoregions(PNRs).Unlike the Pb(B_(1/3)B0_(2/3))O_(3)relaxors,Pb(B_(1/2)B'_(1/2))O_(3)does not undergoes a typical diffuse phase transition without lead vacancies on A-site which enhances randomfields.For the(1-x)Pb(B_(1/2)B'_(1/2))O_(3-x)PbTiO_(3)solid solutions,the long range polar order increases as the PbTiO_(3)content increases.Nevertheless,a central peak owing to dynamic PNRs still remains even for the composition near the MPB,and a critical slowing down is clearly observed in the vicinity of TC.
基金sponsored by the Carnegie/Department of Energy Alliance Center(CDAC,DE-FC03-03NA00144)Use of the Advanced Photon Source was supported by the U.S.Department of Energy under Contract No.DE-AC02-06CH11357+1 种基金HPCAT operations are supported by CIW,CDAC,UNLV,and LLNL through funding from DOENNSA and DOE-BES,with partial instrumentation funding by NSF.M.A.acknowledges ONR grants N00014-14-1-0561.S.P.acknowledges ONR grants N00014-12-1-1034The computations were possible,thanks to the Arkansas High Performance Computer Center at University of Arkansas.S.P.also appreciates Russian Foundation for Basic Research Grant No.14-02-90438_Ucr_a.
文摘Room-temperature Raman scattering and x-ray difraction measurements together with first principles calculations were employed to invetigate the behavior of disordered Pb(In_(1/2)Nb_(1/2))O_(3)(PIN)under pressure up to 50GPa.Raman spectra show broad bands but a peak near the 380cm^(-1) increases its intensity with pressure.The linewidth of the band at 550cm^(-1) also increases with pressure,while two of the Raman peaks merge above 6GPa.Above 16 GPa,we observe additional splitting of the band at 50cm^(-1).The pressure evolution of the diffraction patterns for PIN shows obvious Bragg peaks splitting above 16GPa;consistent with a symmetry lowering transition.The transition at 0.5 GPa is identified as a pseudo-cubic to orthorhombic(Pbam)structural change whereas the transition at 16GPa is istructure and associated with changes in linear compresibility and octahedral titling,and the transition at 30 GPa is associated to an orthorhombic to monoclinic change.First-principles calculations indicate that the Pbam structure is ground state with antiferrodisdortion consistent with experiment.
