Irradiation effect on the electrical properties of corundum and quartz single crystals

Abstract

The radiation effects in corundum and quartz crystals have been assessed at temperatures from 25 to 450°C and gamma doses from 10⁴ to 10⁹ rad. The radiation effects on the conductivity and dielectric losses of the crystals have been shown to be nonlinear, with extrema and inflections. The conductivity of corundum is characterized by three-step kinetics, with pronounced carrier generation in the range 100–200°C and restoration of parameters at 400°C in crystals irradiated to high doses. Both corundum and quartz crystals have extrema tanδ(t) in at different gamma doses. The peaks (200–250 and 50–150°C) grow with increasing frequency, without shifting to higher temperatures. The peaks seem to be due to different mechanisms of dielectric losses. The dose dependences of tanδ and σ have been compared up to 5 × 10⁹ rad and have been shown to correlate with one another. The extrema have been interpreted in terms of the Vul model. We have analyzed the possible origins of the loss maxima and have evaluated the activation energies for ionic polarization and conduction in the materials studied. We assume that the dielectric losses in the irradiated crystals are determined by conduction and polarization.