Observation of rotation of polarization in thin films of Pb(Sc1/2Nb1/2)O3-PbTiO3 via a monoclinic phase

Using a simple methodology based on the classical Bragg-Brentano X-ray geometry we have evidenced at room temperature a pseudo-cubic phase and a monoclinic (Pm) phase in thin films of PbSc1/2Nb1/2O3 (PSN) and (PbSc1/2Nb1/2O3)(0.57)-(PbTiO3)(0.43) (PSN-PT) respectively, the latter compound corresponding to a morphotropic phase boundary (MPB) composition. Depending on the substrate and the thickness, different domains configuration are obtained. Competition between epitaxial and thermal stress induces a complex structural evolution with temperature which is different from that of ceramic samples. Indeed PSN films transform from a pseudo-cubic (triclinic) phase towards a cubic phase whereas in PSN-PT, a succession of transformations from a pure Pm phase toward a tetragonal (possibly non polar) phase is observed, a cubic phase never being reached up to 950 K.