| Lead magnesium niobate-lead titanate(1-x)PbMg1/3Nb2/3O3- xPbTiO3(PMNT)system,a solid solution of relaxor(PMN)and ferroelectric(PT),has attracted much attention in the past because of their excellent piezoelectric properties and potential applications in various fields.Despite significant efforts,the nature of the relaxor behavior and the theory of the phase transition have yet to be elucidated.Light scattering is well known as a powerful technique for investigating the dynamical processes caused by phonons,charge carriers, and spins.In this dissertation,Raman spectroscopy was employed to illustrate the importance of light scattering in application.In this paper, Raman scattering was used to study the structural characters of ralaxor PMNT single crystal.First of all,ferroelectric relaxor 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 single crystal in a wide temperature range from -196 to 374℃were studied by using Raman scattering techniques.The change of the Raman spectral revealed the existence of two structural phase transitions.The first phase transition,from the rhombohedral to tetragonal phase,occurs at 34℃,corresponding to the disappearing of the soft A1 mode and the mergence of the photoluminescence spectra.The second one,the tetragonal-cubic phase transition,appeared at 144℃,which is verified by the vanishing mode of 780 cm-1in VH polarization and can be explained by the changing of the Nb-O-Mg bond length.Furthermore,several high order Raman modes were observed at rhombohedral phase,which interpreted why the Raman spectra at different polarizations did not differ qualitatively at rhombohedral phase.Finally,electric-field-induced domain switching of a single crystal 0.67Pb(Mg1/3Nb2/3)O3—0.33PbTiO3 were studied by polarized Raman scattering technology.
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