DIELECTRIC AND IONIC PROCESSES IN SODIUM TRISILICATE GLASS

A study of the dielectric permittivity and loss of sodium trisilicate glass over a frequency range 12 Hz to 100 kHz and temperature range 77 K to 435 K shows that its conductivity increases non-linearly with frequency and does not merge into a single line of the log conductivity-log frequency plot. This confirms that its dielectric loss is not superposed on a frequency-, and temperature-independent background value. Sodium trisilicate glass shows a second dipolar relaxation peak at 163 K and this relaxation process decreases the magnitude of its loss to a much lower value than inferred earlier. Its value is expected to further decrease to near zero at temperatures below 77 K. At relatively high temperatures, the dielectric properties of the glass are determined by space charge effects, dc conductivity and a dipolar relaxation process which can be analyzed either in terms of dielectric susceptibility, as done by Cole, or in terms of electrical modulus, as done by Johari. The procedure suggested by Cole is direct and seems more elegant than that suggested by Johari.