Dynamical properties of relaxor ferroelectric 0.93Pb͑Zn 1/3 Nb 2/3 ͒O 3 -0.07PbTiO 3 single crystals have been studied by the broadband inelastic light scattering from gigahertz to terahertz frequency range. The longitudinal-and transverse-acoustic ͑LA and TA͒ phonon frequencies deviate below the Burns temperature T B = 736 K from a linear temperature dependence above T B , indicating the existence of polarization relaxations induced by the polar nanoregions ͑PNRs͒. On further cooling, a central peak ͑CP͒ which originates from the relaxations in the PNRs is observed clearly below 600 K Ͻ T B . The CP width decreases markedly down to T ‫ء‬ = 499 K and the change in the CP width becomes mild below T ‫ء‬ . The slower ͑ϳ10 −12 s͒ and faster ͑ϳ10 −13 s͒ relaxation times determined by the CP show good agreement with the relaxation times determined by TA and LA phonons, respectively. 180°and non-180°͑71°and 109°͒ polarization flippings are allowed in the PNRs with the polar rhombohedral symmetry. Considering the piezoelectric coupling in a PNR, it is suggested that 180°flipping is related to the relaxation observed in LA phonon, while non-180°flipping is related to that in TA phonon.

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The enhancement of functionality of perovskite ferroelectrics by local structure is one of current interests. By the Li-doping to KTa1−xNbxO3 (KTN), the large piezoelectric and electro-optic effects were reported. In order to give new insights into the mechanism of doping, the microscopic origin of the Fano resonance induced by the local structure was investigated in 5%Li-doped KTN single crystals by Raman scattering. The coupling between the continuum states and the transverse optical phonon near 196 cm−1 (Slater mode) caused a Fano resonance. In the vicinity of the cubic-tetragonal phase transition temperature, TC-T = 31 °C, the almost disappearance of the Fano resonance and the remarkable change of the central peak (CP) intensity were observed upon heating. The local symmetry of the polar nanoregions (PNRs), which was responsible for the symmetry breaking in the cubic phase, was determined to E(x, y) symmetry by the angular dependence of Raman scattering. The electric field induced the significant change in the intensity of both CP and Fano resonance. From these experimental results, it is concluded that the origin of the Fano resonance in Li-doped KTN crystals is the coupling between polarization fluctuations of PNRs and the Slater mode, both belong to the E(x, y) symmetry.