Propagation properties of Love wave-type surface-acoustic wave on alpha-quartz

As a piezoelectric substrate for surface acoustic wave devices, the LST cut quartz has good temperature characteristics and low propagation loss. However, as the thickness of the metal electrodes on the substrate surface is increased, propagation loss also increases. Further, the electromechanical coupling coefficient is small. In this paper, a cut angle of the quartz substrate is sought that has excellent temperature stability, low propagation loss, and a large electromechanical coupling coefficient in the present of metal electrode films. For the rotated Y-cut substrate in the neighborhood of the LST cut, the propagating surface acoustic wave (SAW) merle changes from the leaky surface wave to the Love wave-type surface acoustic wave for which. no propagation loss occurs in theory while the electromechanical coupling coefficient increased to 0.5 percent at the maximum if gold is used for the electrodes and the propagation direction of the SAW is shifted from the X axis. This is shown by simulation. By experiment, it is shown that the second-order temperature coefficient is on the same order as that of the ST-cut quartz substrate.