Titanium centers structure in natural quartz

Optically and Thermally Stimulated Luminescence in quartz depends on intrinsic and extrinsic point defects. While Al and Ge centers have been intensely studied, few studies are available for Ti centers, for which only the influence on ESR dating is known. From the literature, Ti can create three types of centers, depending on the related trapped alkali ion. The most common in quartz are the Ti-H and the Ti-Li centers. We previously observed that Ti is present as Ti4+ in a five and six-folding coordination, this difference may be due to the effects of the sample pre-treatment. In this project, we want to analyze quartz samples, the primary goal is to infer the titanium coordination in natural quarts; EXAFS measurements will also probe structural information of these extrinsic defects.