Phase diagram of the relaxor ferroelectric (formula presented)

Recently, a new orthorhombic phase has been discovered in the ferroelectric system (formula presented) for (formula presented) after the application of an electric field. In the present work, synchrotron x-ray measurements have been extended to higher concentrations (formula presented) but, surprisingly, for (formula presented) only a tetragonal phase was found down to 20 K. The orthorhombic phase thus exists only in a narrow concentration range with near-vertical phase boundaries on both sides. This orthorhombic symmetry (formula presented) type) is in contrast to the monoclinic (formula presented)-type symmetry recently identified at low temperatures in the (formula presented) (PZT) system over a triangle-shaped region of the phase diagram in the range (formula presented) To further characterize this relaxor-type system, neutron inelastic scattering measurements have also been performed on a crystal of (formula presented) The anomalous soft-phonon behavior (“waterfall” effect) previously observed for (formula presented) and 8% is clearly observed for the 15% crystal, which indicates that the presence of polar nanoregions extends to large values of x.