High coupling, zero TCD SH wave on LGX

This paper reports predicted and measured properties of the pure shear horizontal (SH) mode for the LGX family of crystals, which includes langasite (LGS), langanite (LGN), and langatate (LGT). Our results show high electromechanical coupling and zero temperature coefficient of delay (TCD) along LGX Euler angles (0°, θ, 90°), θ between 10° and 25°, with penetration depths which are comparable to SAW devices. In particular along LGT (0°, 13.5°, 90°), experimental results are disclosed with resonators and delay line structures which verify the high electromechanical coupling (0.8%), about 10 times stronger than the 36° Y rotated quartz SH orientation, and zero TCD around 140 *C. The penetration depth of 7 wavelengths is about eight times shallower than 36° Y quartz. The phase velocity of 2660 m/s is within 0.2% of the calculated value, which is about 55% below the phase velocity of 36° Y quartz, thus leading to smaller Surface Transverse Wave (STW) devices. With such positive predicted and measured coupling and propagation characteristics, these orientations suggest the fabrication of high coupling, zero TCD, and smaller STW devices for liquid sensor, filtering, and frequency control applications.