Neutron scattering study of the relaxor ferroelectric (1-x)Pb(Zn_1/3Nb_2/3)O₃-xPbTiO₃

Neutron elastic diffuse scattering experiments performed on Pb(Zn_1/3Nb_2/3)O₃ (PZN) and on its solid solution with PbTiO₃(PT), known as PZN-xPT, with x = 4.5 and 9% around many reflections show that diffuse scattering is observed around reflections with mixed indices in the transverse and diagonal directions only. From the width of the diffuse scattering peak a correlation length is extracted. In PZN, we have reported that the diffuse scattering is more extended in the transverse than in the diagonal directions [D. La-Orauttapong, J. Toulouse, J. L. Robertson, and Z.-G. Ye, Phys. Rev. B 64, 212101 (2001)]. In the present work, the results show that the addition of PT leads to a broadening of the diffuse scattering along the diagonal, relative to the transverse directions, indicating a change in the orientation of the polar regions. Also, with the addition of PT, the polar nanoregions condense at a higher temperature above the transition than in pure PZN (>40 K), due to stronger correlations between the polar regions. Neutron inelastic scattering measurements have also been performed on PZN-xPT. The results show the broadening of the transverse acoustic phonon mode at a small momentum transfer q upon cooling. We attribute this broadening to the appearance of the polar nanoregions.