Combinatorial discovery of a lead-free morphotropic phase boundary in a thin-film piezoelectric perovskite

We report on the discovery of a lead-free morphotropic phase boundary (MPB) in Sm doped BiFeO3 with a simple perovskite structure using the combinatorial thin film strategy. The boundary is a rhombohedral to pseudo-orthorhombic structural transition which exhibits a ferroelectric to antiferroelectric transition at approximately Bi0.86Sm0.14FeO3 with dielectric constant and out-of-plane piezoelectric coefficient comparable to those of epitaxial (001) oriented PbZr0.52Ti0.48O3 (PZT) thin films at the MPB. The discovered composition may be a strong candidate of a Pb-free piezoelectric replacement of PZT.