Ultrahigh Ferroelectric and Piezoelectric Properties in BiFeO3-BaTiO3 Epitaxial Films Near Morphotropic Phase Boundary

Significantly Enhanced Electrostrain in Oriented Epitaxial Self-Assembled Aurivillius-Type Piezoelectric Films via Regulating Polarization Vectors

High-temperature piezoelectric films with excellent piezoelectric and ferroelectric properties lay the foundation for the development of high-temperature piezo-MEMS devices. However, due to the poor piezoelectricity and strong anisotropy, it remains a challenge to obtain high quality Aurivillius-type high-temperature piezoelectric films with high performance, which impedes their practical implements. Here, a feasible polarization vector regulation strategy associated with oriented epitaxial self-assembled nanostructures for enhancing electrostrain is proposed. Guided by lattice matching relation, non-c-axis oriented epitaxial self-assembled Aurivillius-type calcium bismuth niobate (CaBi₂Nb₂O₉, CBN) high-temperature piezoelectric films were successfully prepared on different oriented Nb-STO substrates. By the lattice matching relationship, hysteresis measurement, and piezoresponse force microscopy analysis, it is confirmed that the polarization vectors transform from a two-dimensional plane to a three-dimensional space, and the out-of-plane polarization switching is enhanced. A platform for more possible polarization vectors is provided in the self-assembled (013)CBN film. More importantly, enhanced ferroelectric (P_r ∼ 13.4 μC/cm²) and large strain (∼0.24%) were obtained in the (013)CBN film, which promotes the great application prospect of CBN piezoelectric films in high-temperature MEMS devices.