Radiation-induced conductivity in quartz crystals

Following room-temperature irradiation of quartz crystals by x rays or γ rays, a transient enhancement of electrical conductivity is observed which decays over a period of several hours. This enhanced conductivity is produced by alkali ions (M+) which are liberated during the irradiation. By freezing in this transient conductivity of synthetic crystals to temperatures below 270 K, the activation energy E/sub m/ for migration of free alkali ions along c-axis channels of the crystal is shown to be 0.14 +- 0.01 eV. The activation energy for the annealing process is approx.0.5 eV, showing that annealing is not controlled by E/sub m/. Results on natural crystals following irradiation are quite different from those of the synthetics; the differences are explained in terms of the presence of shallow traps for free M+ ions in natural crystals. Finally, the transient conductivity is compared with other transient phenomena following irradiation, viz., the frequency change and internal friction of quartz-controlled oscillators