Sweeping and irradiation effects on hydroxyl defects in crystallinenatural quartz

摘要

A study of electrodiffusion (sweeping) and irradiation effects onnhydroxyl defects has been carried out on good quality optically clearnnatural quartz crystals. The crystals were of Arkansas and Braziliannorigin which are used as starting material in hydrothermal synthesis ofnhigh purity cultured quartz crystals. In particular, various OH-n related point defects have been monitored using infrarednabsorption measurements in the 3100-3700 cm-1 range. Ournestimates from sweeping and irradiation results show that the Brazilianncrystal had a much higher concentration of hydrogen than the Arkansasncrystal. We have therefore designated the Brazilian crystal asn“high-H” and Arkansas stone as “low-H” quartz.nHigh- and low-H samples of natural quartz in three different conditions,nunswept, Na-swept, and H-swept, were subjected to a sequence of low- andnroom-temperature irradiations that separate proton and alkali motion.nIrradiation at 77 K reduces the strength of almost all the IR bandsnexcept the short-bond Al-OH- center. Warm up to roomntemperature results in significant recovery (85-95%). Al-OH-ncenters in natural quartz were found to exhibit irradiationncharacteristics similar to those of cultured quartz. For similarnradiation doses (2 Mrad) the prominent bands, Li and H dependent at 3476ncm-1 (designated as Li-n3a) and Na and H dependent at 3451 cmn-1 (designated as Na-n2a) showed a larger decay at 300nK-irradiation than at 77 K. The prominent H-dependent OH-nband at 3468 cm-1 (designated as H-n2a) did not show anyndepletion of peaks after 300 K-irradiation while the 77 K-irradiationnreduced their strength to about 10% of the as-H-swept strength. Thenresults have been discussed in terms of protons and alkali ions motionnto shallow and deep traps and compared with cultured quartz