Properties of at cut gallium phosphate resonators

Gallium phosphate is a quartz analogue that possesses more intense piezoele ctric properties. We report here a study performed to determine more accura tely the properties of resonators made using crystal orientations situated near the main cut presenting a zero temperature coefficient at room tempera ture. Recent crystals having a much improved quality were used to cut plano -convexe resonators with five orientations situated in a range of nearly tw o degrees around the previously determined angular position of this cut. Th e temperature coefficients of the resonance frequencies of the electrically excited shear modes and the electrical properties of the resonators were d etermined. The vibration modes were studied using synchrotron radiation X-r ay topography. For all the studied cuts, parabolic thermal variations of th e resonance frequencies were observed. The temperature of the extremum vari es somewhat with the rank of the mode and also, but slowly, with the cut an gle. On the whole a very good thermal stability is obtained for the resonat ors. Q factors higher than those previously measured were obtained together with, as predicted, very interesting values of the equivalent electrical s cheme. The observed vibration modes are generally close to those computed u sing the Tiersten theory. They present several very interesting properties but display several particularities, such as often possessing a second shea r component with a noticeable amplitude, which make them somewhat different from the mode of the corresponding quartz resonators.