Monoclinic morphotropic phase and grain size-induced polarization rotation in Pb(Mg1/3Nb2/3)O3-PbTiO3

A detailed Rietveld analysis of x-ray data, collected at room temperature, was done on ceramics with controlled grain size between 100 nm and 4 mu m for (PbMg1/3Nb2/3O3)0.80-(PbTiO3)0.20 (PMN-PT20), i.e., a compound at the border of the so-called morphotropic phase boundary. With size reduction the polarization rotates within the monoclinic plane from M-B, i.e., P-x=P-y > P-z to M-A, i.e., P-x=P-y < P-z, and finally reaches a rhombohedral phase, i.e., P-x=P-y=P-z, below a critical value of similar to 200 nm without diminishing the amplitude of the polarization. This study provides an easy way to tailor the direction of polarization of these materials. (c) 2006 American Institute of Physics.