Pure mode axis and the electromechanical coupling coefficients of the 0.67Pb(Mg1/3Nb2/3) O3-0.33PbTiO3 single crystal

Abstract

Pure mode axes of the 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 (PMN-0.33PT) single crystals are investigated by slowness surfaces method. It is found only the Z-axis is a pure mode axis. The piezoelectricically stiffened Christoffel equation of the PMN-0.33PT crystal is solved in the rotating coordinate system. All of the single acoustic modes of thickness vibration are obtained. For the pure longitudinal mode of Z-cut crystal, the electromechanical coupling coefficient is up to 0.82. However, it is only 0.34 for the pure shear modes of X-cut or Y-cut crystal. It is along the pure mode axis that the maximum electromechanical coupling coefficients can be achieved.