Effect of mechanical and electrical biasing fields on thickness mode langasite resonators

Piezoelectric resonators are critical devices for the modern electronics industry. For many applications, these resonators are influenced by biasing fields, with mechanical and electrical biasing fields among the most important ones. The reason the character of a resonator changes under a biasing field is primarily due to the inherent nonlinear material properties of the piezoelectric material. Among commonly used piezoelectric materials for resonators, langasite single crystals are very new and promising. They combine many of the advantages of quartz and lithium niobate—having high electromechanical coupling, as well as good frequency-temperature characteristics. Thus, langasite is a potential material to substitute for current applications dominated by quartz. In this dissertation, the influence of mechanical and electrical biasing fields on resonators made of langasite is investigated systematically. The nonlinear theory of electroelasticity for large deformations and strong fields is first presented. Based on this theory, the force-frequency effect and electroelastic effect of langasite resonators are discussed analytically and numerically. A new experimental method to determine the third-order elastic constants of langasite single crystals through the force-frequency effect is then discussed. Results from experimental measurements of the electroelastic effect for langasite resonators are also presented for several langasite resonator samples. The results of this research are expected to be fundamentally important to the piezoelectric resonator research community