COMPOSITIONAL CHANGES IN IRRADIATED DIELECTRIC CRYSTAL

We have studied the sodium migration in beta''-alumina systems irradia ted by heavy energetic ions. The phenomenon has been discussed in term s of transport equations which include three main process: radiation e nhanced diffusion, electric field assisted migration and preferential sputtering of the alkali element. We have developed a theoretical mode l which describes the process relating the diffusion constant the sodi um mobility and the electric field function to the characteristic effe cts of the radiation. The numerical solutions of this model indicate a Na+ compositional profile strongly dependent on the form of the elect ric held function. A comparison with experimental results suggested an d additional step in the procedure, which includes a subsequent bombar dment of the sample with protons. This step simulates the acquisition of the profile by nuclear reaction techniques and adequately describes the experimental results.