Effect of OH− on the low-frequency dielectric constant of vitreous silica

The 1000-Hz 300°K dielectric constant, εs, of 24 kinds of commercially available vitreous silica has been measured to an accuracy of 0.01% and a precision of about 1 part in 300 000 by the method of substitution (two-fluid technique). The observed dielectric constant ranges from 3.8073 to 3.8304. These results are correlated with hydroxyl ion content and other imperfections. It is found that εs=3.8073+2.72×10−22 N where N is the hydroxyl concentration in ions/cm3, and observed deviations from this rule are attributed to metallic impurities and inclusions. From the results it appears that 3.8073 closely approximates the low-frequency dielectric constant of pure vitreous silica.