Properties of the plane and plano-convex resonators using berlinite, gallium phosphate and langasite

In a first part, a comparison of the main piezo-electric properties of the new piezo-electric materials of crystal class 32 is made using computed and experimental results concerning the Y rotated cuts and particularly the thermally compensated cuts. The most important facts observed are the increase of the coupling coefficient from quartz, to berlinite, langasite and gallium phosphate and the outstanding thermal stabilities of the AT cuts of berlinite and of gallium phosphate. New determinations of the angular positions of the compensated cuts of gallium phosphate and doped langasite are reported. In the second part, the comparison is refined in considering the energy trapping properties of resonators using these materials. Computed and experimental results concerning the trapped modes of plane resonators are compared. They indicate that oscillators and filters having more than 4 times the shifts or the bandwidths achievable with quartz can be obtained using the new materials. Extremely high Q factors and the ability to withstand large excitation levels were observed for langasite plano-convex resonators. We conclude that these materials have an unique set of complementary properties well adapted to an extremely broad range of filtering and frequency generation applications