Modifications induced by sweeping and observed in quartz crystals according to their α₃₅₀₀-value

Abstract
In order to check what sweeping can induce in quartz material, two particular blocks have been studied. These crystals were chosen according to their α₃₅₀₀ infrared value, and so classified as standard quartz or HQ quartz. The different techniques, infrared spectroscopy, ICP chemical analysis, X-ray topography and etching have been used on the same samples before and after sweeping. The chemical analysis results show an effective migration of alkalis. This migration is different from a sample to the other but it remains sometimes very weak in both cases. The decrease of the number of the etch-pits and the length of the etch-channels has been verified in the swept part of the crystal comparably to the unswept part of the same crystal ; the initial quality of the material appears to be an important parameter. X-ray topography shows that there is no modification by sweeping in the partition of the dislocations within both the crystals. Infrared spectroscopy reveals that the homogeneity of the crystals can be modified by sweeping. The measurements lead to some unexpected results which indicate that the sweeping cannot be considered as a routine process.