The x-ray-induced ‘‘blue’’ emission from commercially available, high-quality synthetic quartz has been studied between 80 and 300 K. Three overlapping bands, each having a different quenching temperature, have been experimentally resolved in the as-grown crystals. These bands peak at 440, 425, and 380 nm; their half-widths are 0.64, 0.75, and 0.92 eV; and they thermally quench in the 120–160, 170–210, and 220–270 K regions, respectively. An intense electron irradiation at room temperature or an electrodiffusion (sweep) in a hydrogen atmosphere eliminates the band at 380 nm. Our results suggest that the 380-nm band arises from recombination of an electron with a hole trapped adjacent to an alkali-compensated aluminum ion (i.e., an Al–M+ center). The origins of the bands at 440 and 425 nm remain unknown. As an application of these results, a screening test is described which could assist quality control during selection of quartz bars for use in precision frequency control devices.
Thermally stimulated luminescence from one natural and two synthetic samples of alpha-quartz has been investigated in the range from room temperature to 400 °C. Comparisons were made between unswept samples and others, taken from adjacent positions in the original stones, that were swept in a hydrogen atmosphere. Three sets of thermally stimulated luminescence (TSL) data were obtained from each sample, corresponding to initial electron irradiation at 77 K, at ice-bath temperature, and a double irradiation at ice bath plus 77 K. Electron spin resonance and infrared absorption data also were obtained from the same samples. A number of TSL peaks were found in the 60–130 °C region and they have been tentatively associated with hydrogen in the crystal. More intense peaks were found in the 200–300 °C region, but only in unswept samples after an ice-bath or ice-bath plus 77-K irradiation. These latter peaks are attributed to electron-hole recombination at [AlO4]0 centers as a result of electron release from alkali-associated electron traps.
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