GaPO4: an interesting crystal for vibrating inertial sensors

New experimental results on Gallium Orthophosphate (GaPO₄) vibrating beams are presented: a quality factor (Q) of 700 000 has been measured for a one millimeter width beam at about 10 kHz, as well as Q of 130 000 for a 150 ¿m beam width at 110 kHz. At this frequency range, such high quality factors are obtained for the first time on GaPO₄ flexure mode beams. Frequency temperature dependence of 10 to 20 ppm/K has been also measured, depending on the beam orientation, in accordance with the theoretical predictions. The GaPO₄ is a quartz homeotype piezoelectric single crystal, well-known for its temperature stability (up to 970°C) and its higher electromechanical coupling coefficients than the quartz. These new results confirm the potentiality of GaPO₄ in the field of vibrating inertial sensors: for Vibrating Beam Accelerometer (VBA) an improvement of the bias stability -i.e frequency stability - by a factor 10 is expected on the basis of the measured higher quality factor and lower frequency temperature dependence than the quartz.