Sweeping investigations on as grown Al-Li+ andAl-OH- centers in natural crystalline quartz

摘要

In the present work, we have used near infrared absorption in thenregion 3100-3700 cm-1 to study a variety of optically clearnsamples of natural quartz crystals of Brazilian and Arkansas origins.nThe crystals used were hydrogen-rich and hydrogen-lean withnapproximately equal and also of varying aluminum concentrations. Thenalkali-H concentration in hydrogen-rich samples was much higher thannthat in the hydrogen-lean samples. The crystals were investigated inntheir as-received (unswept or Li-swept), Na- and H-swept conditions. Thenvery narrow variation in the strength of grown-in Al-Li+ncenters in all samples of natural quartz suggests that the Al-OH-n centers in these crystals become stable only after a certainnmaximum Al-Li+ concentration. This concentration appears tonbe independent of the origin of the growth and reflects a characteristicnfeature of the growth mechanism of natural quartz crystals