Investigations of several langasite cuts by high temperature in situ characterizations of surface acoustic waves delay lines

In this paper, we investigate the thermal frequency behavior of the surface acoustic waves (0°, 138.5°, 26.7°), (0°, 22°, 31°) and surface transverse waves (STW) (0°, 22°, 90°) langasite (LGS) cuts by RF characterization means performed on delay lines up to 900 °C. Above 700 °C, results are altered by degradation phenomena of the Pt electrodes. We observed a strong impact of the operating frequency on the thermal frequency shifting of devices. Around the 434 MHz-ISM band, the (0°, 22°, 90°) STW cut offers similar thermal behavior as the one of the wellknown (0°,138.5°, 26.7°) Rayleigh cut. Moreover, associated to the (0°, 22°, 31°) cut, the STW one could allow for differential measurements on one unique substrate.