Experimental study of SAW propagation on gallium orthophosphate

Gallium orthophosphate (GaPO₄) is a piezoelectric crystal with the same class of symmetry as quartz. The interest in GaPO ₄ is due to a higher electromechanical coupling factor and the possibility of using the crystal at high temperatures. Theoretical and experimental studies have already proved the existence of temperature-compensated cuts for bulk wave resonators. However for SAW propagation, only theoretical computations predict the existence of temperature-compensated cuts analogous to the (ST,X) cut of quartz. In this paper, experimental measurements on SAW propagation are performed on a Z-cut GaPO₄ crystal exhibiting a flat surface of about 1 cm². Various propagation directions are investigated including orientations for which a shear horizontal surface skimming bulk wave can be generated. Experimental measurements on SAW velocity and temperature behavior are compared to theoretical models based on available material constants of GaPO₄