Crystallographically engineered BaTiO₃ single crystals for high-performance piezoelectrics

Dielectric and piezoelectric properties of BaTiO₃ single crystals polarized along the 〈001〉 crystallographic axes were investigated as a function of temperature and dc bias. Electromechanical coupling (k₃₃)≃85% and piezoelectric coefficients (d₃₃)≃500 pC/N, better or comparable to those of lead-based Pb(Zr,Ti)O₃ (PZT), were found from 〈001〉-oriented orthorhombic crystals at 0°C, as a result of crystallographic engineering. A rhombohedral BaTiO₃ crystal polarized along 〈001〉 also exhibited enhanced piezoelectric performance, i.e., k₃₃≃79% and d₃₃≃400pC/N at -90°C, superior to PZTs at the same temperature. It was found that the crystal structure determined the (in)stability of the engineered domain state in BaTiO₃ single crystals. Rhombohedral (3m) crystals at -100°C exhibited a stable domain configuration, whereas depoling occurred in crystals in the adjacent orthorhombic phase upon removal of the E field.