Properties of morphotropic phase boundary Pb(Mg1/3Nb2/3)O3-PbTiO3 films with submicron range thickness on Si based substrates

Abstract

The electrical properties of (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 films with composition in the morphotropic phase boundary region around x=0.35, submicron thickness and columnar microstructure, prepared on Si based substrates by chemical solution deposition are presented and discussed in relation to the properties of coarse and fine grained ceramics. The films show relaxor characteristics that are proposed to result from a grain size effect on the kinetics of the relaxor to ferroelectric transition. The transition is slowed down for grain sizes in the submicron range, and as a consequence intermediate polar domain configurations with typical length scales in the submicron- and nanoscales are stabilised. A high saturation polarisation can be attained under field, but fast polarisation relaxation occurs after its removal, and negligible remnant values are obtained. At the same time, they also show spontaneous piezoelectricity and pyroelectricity. Self polarisation is thus present, which indicates the existence of an internal electric field that is most probably a substrate effect. Films would be then in a phase instability, at an intermediate state between the relaxor and ferroelectric ones, and under a bias electric field, which would explain the very high spontaneous pyroelectric response found.