Conversion of 45° rotated X-cut KNbO3 plates to Y-cut plates by compression

Potassium niobate (KNbO₃) single crystals with a pseudo-cubic structure exhibit very high piezoelectric coupling factors for thickness-extensional modes and surface acoustic waves, k_t and k_SAW. To obtain a better understanding of domain-behavior with a stress, conversion of high-k_t 45° rotated X-cut plates of KNbO₃ to high-k_SAW Y-cut plates was attempted by applying a compressive force obliquely to the major surface of the plates. The X-ray diffraction analysis indicated that 90% of the 45° rotated X-cut plate were converted. The admittance response of the resulting plate was very close to that of a single-domain Y-cut plate. The domain evolution during application of a stress was observed and video-recorded using a developed system consisting of a polarizing microscope equipped with a stress application tool and a video camera. This observation showed that the conversion was occurred by a pressure of 6.6 MPa.