Practical methods to determine hydrogen and hydroxyl contents in quartz crystals

Before manufacturing quartz crystal resonators, it is essential to perform a systematic study of the material which allows a prediction of the behavio ur of the resonator. Furthermore, we know that some treatments like sweepin g appear as a mean for clearly improving the performance. Unfortunately, up to now, there is no valid method to obtain the hydrogen content which is t he major impurity in quartz crystals, sometimes qualified as a poison. The major difficulty lies in the fact that this element is found in several for ms. It is just well known that the strength of absorption by hydroxyls in t he 3 mum infrared region is frequency dependent. Some sharp bands, attribut ed to specific impurities like Al-OH or M/OH (where M = K, Li or Na), are s uperimposed on a broad absorption band. Furthermore, the [1900-2000] nm abs orption band has been attributed to the presence of hydrogen in the molecul ar form H2O. In this paper we present a review of different methods usually employed to tentatively qualify the Ii content. We discuss a few of them w hen they are applied to different kinds of samples issued from synthetic as well as natural quartz and submitted to different combinations of treatmen ts such as sweeping out or into, gamma irradiation, high temperature anneal ings.