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 (k(33))similar to 85% and piezoelectric coefficients (d(33))similar to 500 pC/N, better or compar able to those of lead-based Pb(Zr, Ti)O-3 (PZT), were found from < 001 >-or iented orthorhombic crystals at 0 degrees C, as a result of crystallographi c engineering. A rhombohedral BaTiO3 crystal polarized along < 001 > also e xhibited enhanced piezoelectric performance, i.e., k(33)similar to 79% and d(33)similar to 400 pC/N at -90 degrees C, superior to PZTs at the same tem perature. It was found that the crystal structure determined the (in)stabil ity of the engineered domain state in BaTiO3 single crystals. Rhombohedral (3m) crystals at -100 degrees C exhibited a stable domain configuration, wh ereas depoling occurred in crystals in the adjacent orthorhombic phase upon removal of the E field. (C) 1999 American Institute of Physics. [S0021-897 9(99)04517-X].