Temperature-stable orientations in LGS and LGN piezoelectric crystals for surface acoustic waves

The temperature characteristics of surface acoustic waves (SAW) propagating in LGS and LGN crystals are numerically analyzed. The optimal orientations that correspond to the zero value of the first-order temperature coefficient of delay (TCD) for SAW propagating in these crystals are considered. The second-order TCD for SAW is calculated for a wide range of operating temperatures. It is shown that the temperature dependences of the material constants of LGS and LGN crystals are strongly nonlinear. The characteristics of SAW propagating in a structure that consists of an isotropic layer overlying an LGS or LGN piezoelectric crystal are numerically calculated. It is shown that, in the presence of a thin aluminum layer of a certain thickness on the crystal surface, in some cases it is possible to extend the operating temperature range within which the TCD for SAW is equal to zero.