Properties of AT cut gallium phosphate resonators

Gallium orthophosphate is a quartz-homeotypic piezoelectric crystal that presents simultaneously a much larger coupling coefficient (k² is nearly four times that of quartz) and a large thermal stability of its properties. Previous experiments and calculations have shown that the main singly rotated compensated cut (the equivalent of the AT cut of quartz) is situated near Y-15° 45´. It was also shown that the devices made using this material should present several advantages over quartz for filter or oscillator applications. Several new determinations of the material constants were made in recent years. They allow to predict more accurately the properties of devices. More recently several new advances in crystal growth have led to an important increase in the size of the crystals and of the crystalline quality. In order to precise determine the properties of devices made with orientations near the AT cut, new investigations were made. In this contribution we report the most important features observed during these experiments