Strain-engineered orthorhombic-rhombohedral phase boundary in epitaxial bismuth ferrite films

Strain-engineered phase boundaries in epitaxial bismuth ferrite films has been investigated via thermodynamics analysis in good agreement with both experimental and first principle studies, and a novel orthorhombic-rhombohedral (OR) phase boundary is found to exist under tensile misfit strain. In contrast to more widely studied tetragonal-rhombohedral phase boundary in bismuth ferrite where enhanced piezoelectric response is largely attributed to extrinsic mechanism, the OR phase boundary is found to show enhanced intrinsic piezoelectric response, and the change of the polarization slope at phase boundary is found to be the key to the enhancement. Difference between strain-engineered phase boundaries and classical morphotropic phase boundary in lead zirconate titanate is also noticed.