Relaxor ferroelectrics are characterized by a number of unique properties, many of which are strongly related to the scales inside. The elationship between the crystal coherence length and electrical response of Pb[(Mg1/3Nb2/3)1−xTix]O3 near the morphotropic phase boundary have been precisely investigated using a single crystal with a Ti composition gradient at room temperature by synchrotron x-ray scattering. The crystal coherence length (ξ) determined from the widths of Bragg scattering varies by over two orders of magnitude in a 10 mol% range (ξ = 70 nm - > 10 μm) of the Ti composition. It is shown that there is a strong negative correlation between the low-frequency electrical response and the crystal coherence length at the sub-μm scale [1]. The study of 0.91Pb(Zn1/3Nb2/3)O3-0.09PbTiO3 near Tc = 455 K shows that the heterophase fluctuation with a size of ξ ~ 200 nm is expected to correlate to the low-frequency dielectric dispersion and contribute to the phase transition as a precursor phenomenon of the first-order phase transition [2]. Nanometer scale structures, a deviation from average structures discussed above, can contribute to the high-frequency response. The structures can be observed as a diffuse x-ray scattering around the Bragg position and the intensity shows similar temperature dependence to that of high-frequency dielectric response [2].
References
[1] D. Shimizu, K. O. et al., Phys. Rev. B 92, 174121 (2015).
[2] K. Ohwada et al., Phys. Rev. B 90, 104109 (2014), Phys. Rev. B 83, 224115 (2011).