Compositional changes in irradiated dielectric crystal

Abstract

We have studied the sodium migration in β″-alumina systems irradiated by heavy energetic ions. The phenomenon has been discussed in terms of transport equations which include three main process: radiation enhanced diffusion, electric field assisted migration and preferential sputtering of the alkali element. We have developed a theoretical model which describes the process relating the diffusion constant, the sodium mobility and the electric field function to the characteristic effects of the radiation. The numerical solutions of this model indicate a Na⁺ compositional profile strongly dependent on the form of the electric field function. A comparison with experimental results suggested and additional step in the procedure, which includes a subsequent bombardment of the sample with protons. This step simulates the acquisition of the profile by nuclear reaction techniques and adequately describes the experimental results.

Key Words:

• ion irradiation
• diffusion
• electric field assisted migration
• preferential sputtering