Polar and chemical order in relation with morphotropic phase boundaries and relaxor behaviour in bulk and nanostructured PSN-PT

We have recently evidenced the existence of a complex path of polarisation rotation via two monoclinic phases in the giant-piezoelectric materials PSN–PT that is similar to the PMN–PT system. In this article we have presented the state of knowledge on the PSN–PT system and have given new results showing the close connection between the local inhomogeneous chemical order of Sc/Nb/Ti cations and the stability of different ferroelectric phases. The notion of morphotropic phase boundaries is discussed in relation with the gradual appearance of long-range polar order with increasing Ti content in PSN–PT. Comparison with the films and nanopowders/ceramics has also been made.