10:15 〜 10:30
▲ [20a-W833-4] Electric Field Effect of Relaxor Ferroelectric 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 Single Crystals Studied by Micro-Brillouin Scattering
キーワード：Brillouin scattering,nanodomain, macrodomain,polarization switching
The relaxor ferroelectric single crystals (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT) with the ABO3-type perovskite structure have been studied last several decades due to its excellent piezoelectric and electromechanical responses. From the technological point of view, the PMN-xPT single crystals with composition near the morphotropic phase boundary (MPB) are very interesting. Under dc electric field, they demonstrate a great variety of physical properties that will give the new insights into further applications. In the present study, the acoustic properties of PMN-30PT (x = 0.30) single crystals under the dc electric field along the [001] direction were investigated by using broadband Brillouin scattering. Under 0.5 kV/cm, the frequency shift of the longitudinal acoustic (LA) mode exhibits splitting below ~351 K. This is due to the coexistence of the ferroelectric macrodomain with the high-frequency LA mode and the nanodomain state with the low-frequency LA mode owing to the pinning of domain walls by the random field. Under 1.0 kV/cm, the LA mode splitting disappears by the complete switching of nanodomain to the single/macrodomain state. In the ferroelectric phase of the zero field cooling crystal, a discontinuous transition of the LA velocity from a nonequilibrium nanodomain state (A) to an intermediate state (B) of coexisting nano- and macrodomains states was observed at 1.05 kV/cm. At 2.6 kV/cm, the state (B) changes into the equilibrium state (C). Similar behaviors were observed in the dielectric measurements. At 0.5 kV/cm, the Monoclinic (M) phase coexists with Tetragonal (T) phase. At 1.0 kV/cm, the M phase disappears and the T phase becomes stable. The critical end point (CEP) was observed at 1.2 kV/cm and at 398 K. At CEP the polarization rotation energy is decreased significantly. Our results suggest that at the CEP, the transition from multidomain to a single domain state may be the origin of the maximum electric responses in the PMN-30PT single crystal near the MPB composition.