Langasite, langanite, and langatate resonators: recent results

Materials in the langasite family are of current interest for both bulk-wave and surface-wave devices. Plano-convex Y-cut bulk-wave resonators have been built and tested on overtones 1-9 using LGS (langasite, La/sub 3/Ga/sub 5/SiO/sub 14/), LGN (langanite, La/sub 3/Ga/sub 5.5/Nb/sub 0.5/O/sub 14/), and LGT (langatate, La/sub 3/Ga/sub 5.5/Ta/sub 0.5/O/sub 14/). Frequencies and motional inductances are compared with calculated values, with good agreement except for the motional inductance of LGT. For all 3 materials, frequency variation is an essentially parabolic function of temperature. For LGN and LGT, reported values of the Q-frequency product are significantly above the classical limit for AT-cut quartz.