Acoustic losses in quartz and their links with InfraRed measurements

The performances of quartz resonators and sensors are often limited by various defects existing in the crystal, whatever the origin of the quartz is (natural or cultured). So, before manufacturing high-quality quartz devices, it is essential to perform a systematic study of the as-grown material which will allow a prediction of the behaviour of the device. Among point defects, the most common is the OH related growth defect. It is Infrared active and it can be modified by treatments such as thermal annealing, sweeping or irradiation. Kats carried out a classical study of hydrogen in both natural and synthetic quartz. Particularly, thea author pointed out 4 stretching-mode infrared bands "growth-defects" including hydrogen, increasing with crystal growth-rate and decreasing when the sample is irradiated. After Kats, several authors (Lias, Chakraborty, Paterson, Bahadur...) worked on different methods to determine the OH content. Finally, numerous researchers (Fraser and Dodd in 1966, Rudd and Hougthon in 1966, Sawyer in 1972 and 1983, Toyo in 1976...) have shown that the electrical quality factor "Q" is closely dependant on the hydrogen content in quartz. As this Q-factor does not depend only on the material quality, it has been necessary to define the resonator as nearly as possible to an ideal device, ideally designed and manufactured. To avoid these difficulties also linked to the measurement principle of the spectrometer ("double beam" or "with Fourier transform"), we present here new measurements on SC-cut resonators working on their 10 MHz 3rd overtone. They are built in GEMMA quartz samples following a very precise manufacturing process. Furthermore, they have been extracted from various generations of cultured quartz and have also been submitted to different treatments.