Domain wall structures on the etched surfaces of the solid solutions of Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-xPT; x=8%, 20%) were investigated by atomic force microscopy (AFM). Ferroelectric and ferroelastic domain wall structures were observed. In the rhombohedral phase, a zigzag domain wall structure was found. We showed that all of the ferroelastic domain wall structures observed in the tetragonal and rhombohedral phases can be explained by the Sapriel theory, and concluded that no ferroelectric charged domain wall exists in the PZN-PT crystal without an external field. The symmetry of PZN-8%PT at room temperature is rhombohedral.
Light scattering experiment has been performed in a single crystal of 0.89Pb(Zn1∕3Nb2∕3)O3–0.11PbTiO3. The central peak (CP) spectra have been well detected with high resolution over the wide frequency region up to 150GHz. The distribution is discovered in the relaxation time associated with the CP. Moreover, it is found that the maximum relaxation time indicates the dynamical slowing down near the temperature Tm at which the low-frequency dielectric constant has a maximum. This finding strongly suggests that the physical origin of the CP is “polar nanoregions.”
It was proposed that large dielectric constants in Pb(Zn1/3Nb2/3)O3–xPbTiO3 (PZN–xPT) crystals are mainly due to the fluctuation of polarization along the spherical direction (perpendicular to the spontaneous polarization) near the morphotropic phase boundary (MPB), named transversal instability [M. Iwata and Y. Ishibashi: in Ferroelectric Thin Films, ed. M. Okuyama and Y. Ishibashi (Springer, 2005) Part III, p. 127]. The dielectric anisotropy in the MPB region of PZN–xPT was investigated to clarify the origin of the large dielectric constant in perovskite-type relaxors. It was found that the dielectric constant perpendicular to the spontaneous polarization indicating transversal instability markedly increases as it approaches MPB. The dielectric anisotropy and large dielectric constant near the MPB were discussed in terms of the phenomenological theory.
We derive an improved prescription for the merging of matrix elements with parton showers, extending the CKKW approach. A flavour-dependent phase space separation criterion is proposed. We show that this new method preserves the logarithmic accuracy of the shower, and that the original proposal can be derived from it. One of the main requirements for the method is a truncated shower algorithm. We outline the corresponding Monte Carlo procedures and apply the new prescription to QCD jet production in e + e − collisions and Drell-Yan lepton pair production. Explicit colour information from matrix elements obtained through colour sampling is incorporated in the merging and the influence of different prescriptions to assign colours in the large N C limit is studied. We assess the systematic uncertainties of the new method.
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