Quantitative domain engineering for realizing d₃₆ piezoelectric coefficient in tetragonal ceramics

Piezoelectric devices based on d₃₆ mode are remarkably stable that depolarization rarely occurs in d₃₆ face shear mode, because d₃₆ mode is completely different from d₁₅ thickness shear mode, where the applied electric field is perpendicular to poling direction and depolarization is ineluctable due to 90° dipole rotation. However, piezoelectric ceramics conventionally possess three piezoelectric coefficients (i.e., d₃₃, d₃₁, and d₁₅), while d₃₆ only exists in single crystals of specific point groups and cut directions. In this work, we propose a method to realize d₃₆ piezoelectric coefficient in tetragonal piezoelectric ceramics by mechanical and electric domain engineering. This method is successfully applied in bismuth scandium-lead titanate (abbreviated as BS-PT) high-temperature piezoelectric ceramics with a resultant d₃₆ up to 160 pC/N, which broadens the application of BS-PT ceramics, such as face shear actuator, energy harvester, transducer, etc. We find that domain engineering by transversal electric poling is preferred compared with the transversal mechanical poling, due to the simpler process, higher reliability, and higher resultant d₃₆ piezoelectric coefficient. By combining the Diffraction-Plane-Transformation (DPT) model with the domain engineering via transversal electric poling, we demonstrate a quantitative domain engineering method for the first time, which could be used for optimizing the piezoelectric properties by precise design of the domain structures in piezoelectric materials.