Measurement of piezoelectric material's surface acoustic wave electromechanical coupling cofficient by delay lines

The surface acoustic wave electromechanical coupling coefficient K_s ² of piezoelectric material expresses the energy exchange efficiency of surface acoustic wave and electrical field. It is also a significant parameter for development of piezoelectric material and surface acoustic wave devices design and fabrication. Two kinds pattern of double delay lines were designed. The first is a surface acoustic wave double delay lines with free surface, in order to calculate V_f. The second is a surface acoustic wave double delay lines with metallized surface, in order to calculate V_m. Both of the delay lines were fabricated on the same wafer, then sampling some devices for delay time measurement by Agilent E5062A vector network analyzer. The average of V_f and V_m were calculated respectively. The K_s ² was calculated using above-mentioned formula. The test and calculation were completed with 128deg Y-X LiNbO₃, 6deg Y-X LiNbO₃, Y-Z LiNbO₃ and X-112deg YLiTaO₃, 36deg Y-X LiTaO₃ respectively. The results accord with Sadao measure's results in the materials integration.