Ultrarotuntersuchungen über den Einbau von H in natürlichem Quarz

Abstract

AbstractThe IR absorption spectra of various quartz crystals have been investigated; besides the vibrations due to the SiO2‐lattice, there are bands in the 7000, 5000, 3000 and 900 cm−1 regions which are due to lattice imperfections. Variations in intensity of several powers of ten have been observed from one crystal to another and occasionally within the same crystal. The half‐width of the bands is strongly temperature dependent. H‐D‐exchange experiments (from which a self‐diffusion coefficient of approx. 10−7 cm2/sec at 950 °C has been obtained) show, that several bands in the 3000 cm−1 region are due to OH vibrations. Further experiments indicate that all bands observed here, other than those of the SiO2‐structure, are related to H‐containing defects. Annealing at temperatures above 650 °C causes permanent changes in the IR‐spectrum, which are apparently related to positional exchanges. On electrolysis, H from atmospheric H2O can enter and replace the alkali ions, which have been deposited on the cathode. The behaviour of quartz defects after different irradiation treatment has been studied. From the IR spectrum the H‐concentration can be evaluated; values of about 1018 H/cm3 are frequently found for clear quartz crystals, while all natural smoky quartzes as yet examined show a low H content (approx. 1017 H/cm3). Different types of H‐defects which might be responsible for the appearance of the bands are discussed. H2O molecules in considerable amounts are apparent only in milky quartzes and in d‐l‐ twinned quartzes with lamellae (these include most of the amethysts).