A new investigation of dielectric relaxation processes in smoky quartz crystals

Abstract

Dielectric loss measurements on smoky quartz crystals over a wide frequency and temperature range (200 Hz-2.5 MHz and 20.4–160°K) showed, besides the well-known relaxation process at low temperatures, also a new relaxation mechanism, which becomes dominant above 100°K. There are strong arguments that both processes are due to the same type of colour centres. The rate theory in its simplest form cannot be held. The experiments are discussed with the help of Sussmann's theory of intermediate states including tunnelling processes.

The deviations of the tan σ curves from the theoretical Debye curve, due to a spread in relaxation times, were studied. At low temperature there appeared to be a uniform relation between the measured mean value τ and the experimentally determined spread τH/τL, defined by the Fröhlich distribution function g(τ) ∝ τ-1 for τL < τ < τH. The upper limit τH has, at constant temperature, a nearly constant value for various samples. The lower limit τL, however, varies by more than a factor 10. At high temperature only a very small spread in τ values was found.