DEFECTS DYNAMICS IN AS-GROWN AND ELECTRODIFFUSED QUARTZ - AN INTERPRETATION OF THE PREDOSE EFFECT

In the thermally stimulated luminescence (TSL) of quartz there is always a glow peak at T=100°C, whose sensitivity (response to a unit irradiation dose) increases after repeated irradiations followed by heating. This phenomenon, known as predose, has been studied in synthetic quartzes, both as grown and deprived of alkali ions, this latter process being obtained by electrodiffusion ("sweeping out"). Evidence is given that only unswept or partially swept quartzes show the predose effect. Through the study of the combined effects of irradiation and thermal annealing, following two different procedures, a relation between the formation of Al-OH- centers and the 100°C TSL intensity is established. We propose that the enhancement of luminescence happens through the modification of oxygen hole centers from precursors containing hydrogen to peroxy radicals (e.g., O-2 ions) which are responsible for the luminescence. The H+ ions, made available in such a process, are responsible for the Al-OH - centers formation.