Three-dimensional mapping of diffuse scattering in Pb(Zn_1∕3Nb_2∕3)O₃-xPbTiO₃

High energy (67 keV) x-ray diffuse scattering measurements were performed on single crystals of Pb(Zn_1∕3Nb_2∕3)O₃-xPbTiO₃ (PZN-xPT), to map out the diffuse scattering distribution in all three dimensions around a large number of Bragg peaks simultaneously. For x=0,4.5%, and 8%, the results are very similar, indicating same type of correlations of polarizations in these compounds. Our results show that the diffuse scattering intensity consists of six ⟨110⟩ rod-type intensities around reciprocal lattice points. A simple model is suggested where {110} type planar correlations of the in-plane ⟨11̅ 0⟩ type polarizations in real space contribute to the ⟨110⟩ rod-type diffuse intensities in the reciprocal space. The planar correlations of polarizations are likely a result from condensations of soft ⟨11̅ 0⟩ polarized optic phonon modes.