Composition dependence of local piezoelectric nonlinearity in (0.3)Pb(Ni0.33Nb0.67)O3-(0.7)Pb(ZrxTi1-x)O3 films

The composition dependence of dielectric and piezoelectric nonlinearities were characterized in epitaxially grown (0.3) Pb(Ni0.33Nb0.67)O-3-(0.7)Pb(ZrxTi1-x)O-3 thin films deposited on SrTiO3. Tetragonal, morphotropic phase boundary (MPB) and rhombohedral films were prepared by changing the Zr/Ti ratio. The relative dielectric permittivity epsilon(r) and the converse piezoelectric coefficient d(33,f) were found to follow the Rayleigh law. The local piezoelectric nonlinearity map showed the formation of micron-sized clusters of higher nonlinear activity for the MPB and rhombohedral compositions. The ratios of the irreversible to the reversible Rayleigh constants alpha(epsilon)/epsilon(init) and the spatially averaged alpha(d)/d(33,init) ratio were larger for the rhombohedral and MPB compositions compared to the tetragonal composition. The larger dielectric and piezoelectric nonlinearities observed for the rhombohedral sample are interpreted in terms of a higher domain wall mobility due to a smaller ferroelectric distortion and superior crystal quality. (C) 2011 American Institute of Physics. [doi:10.1063/1.3622312]