Local structure and dynamics of ferroelectric solids

Details of local atomic structure and dynamics play a significant role in determining the ferroelectric properties, even though ferro electricity is a highly collective phenomenon. They are most important in disordered ferroelectrics, the relaxor ferroelectrics in particular. In this chapter we discuss how neutron scattering measurements enable us to see directly the local structure and dynamics and facilitate the understanding of their role through the static and dynamic atomic pair-density function (PDF) analysis. The PDF provides direct information on the local atomic structure, even when the structure is disordered, and complements the conventional crystallographic approaches. Recent advances in the pulsed neutron sources and in spectrometers have made this technique particularly powerful for studies of disordered ferroelectric solids. We focus on the role of Pb2+ ions in mixed ferroelectrics and the atomistic dynamic mechanism of relaxor ferroelectrics.