Electromechanical coupling factor of KNbO3 single crystal

This paper is concerned with the electromechanical coupling factors for bulk waves in KNbO₃ crystal. The dependence of coupling factors on the orientation of vibrators for various types of vibration modes has been calculated. As a result, it has been found that most of these coupling factors are very large at certain orientations of vibrators. Especially, the maximum coupling factor of the thickness-extensional mode excited with a perpendicular field, k_t , is as high as 69% for the rotated X-cut by an angle 49.5° about,the Y-axis, while that of the thickness-shear mode, k_s, is 88% for the X-cut. These large values were proved by some experiments. It has also been found that the coupling factor of the width-extensional mode of a thin finite-width plate with electrodes on its edges, k´_ww, is 82% for the rotated Z-cut by an angle 43.5° about the Y-axis