Crystallographic orientation dependence of piezoelectric and dielectric properties of BNT-based thin films

To attain a deep understanding of piezoelectric and dielectric properties dependence of crystallographic orientation, the rhombohedral 0.90(Bi0.5Na0.5)TiO3-0.10(Bi0.5K0.5)TiO3 (abbreviated as BNT-BKT) single-crystal films with three primary orientations of (100), (110), (111) were obtained by sol-gel method. Crystallographic structure measurement by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) revealed that the BNT-BKT films display a pure perovskite phase and a good epitaxial relationship. Crystallographic orientation dependence of piezoelectric and dielectric properties of the BNT-BKT thin films was investigated. The superior piezoelectric properties in (100)-oriented epitaxial thin films are mainly derived from the intrinsic piezoelectric activities based on the crystallographic orientation and corresponding ferroelectric domain structure analysis. It is also important to note that the Curie temperature (Tc) and dielectric permittivity in piezoelectric films were also affected by the crystallographic orientation.