Enhancement of local piezoresponse in samarium and manganese co-doped bismuth ferrite ceramics

Field-induced polarization switching and electromechanical mechanisms in lead-free multiferroic BiFeO3 materials are essential for applications in nanoscale logic and magnetoelectric-controlled devices. This work highlights enhanced ferroelectric polarization switching and electromechanical strain behaviors in (Sm, Mn) co-doped (Bi0.95Sm0.05)(Fe1-xMnx)O3 ceramics with increasing Mn substitution. The Mn L-edge and oxygen K-edge synchrotron X-ray absorption spectra confirm a Mn3+→Mn4+ valence shift and reduced O 2p–Fe 3d and O 2p–Bi 6sp orbital hybridizations in the Mn-doped specimens. High-resolution transmission electron microscopy (TEM) confirms larger polar nano-regions (PNRs) and oxygen octahedral tilt in the Mn-doped specimens. Out-of-plane piezoresponse force microscopy (OP-PFM) shows improved local ferroelectric polarization and electromechanical response within grains by the Mn substitution. The enhanced ferroelectricity and piezoelectricity may originate from collective effects, including fewer oxygen vacancies, reduced covalent bonding, larger oxygen octahedral tilt and PNRs, caused by the Sm and Mn co-substitution.