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 LiNbO
₃
, 6deg Y-X LiNbO
₃
, Y-Z LiNbO
₃
and X-112deg YLiTaO
₃
, 36deg Y-X LiTaO
₃
respectively. The results accord with Sadao measure's results in the materials integration.