Size-driven relaxation and polar states in PbMg1/3Nb2/3O3-based system -: art. no. 174115

Nanocrystalline powders and ceramics with controlled grain size from 15 to 3000 nm of PbMg1/3Nb2/3O3(PMN) and (PMN)(0.65)-(PbTiO3)(0.35) (PMN-PT35) have been synthesized using the ball milling method. Dielectric experiments have revealed in PMN a disappearance of relaxation below approximate to 30 nm grain size and combined x-ray and Raman experiments the vanishing of correlations between polar nanoregions (PNRs). A similar study in morphotropic compound PMN-PT35 has shown the appearance of a relaxor state below approximate to 200 nm, associated to a destruction of the ferroelectric domains state towards PNRs in a paraelectric matrix. These phenomena are discussed in connection with pressure experiments from the literature and on the basis of polar states destabilization by both elastic and electric random fields changes associated with the size reduction.