LATTICE EXPANSION IN EUBA2CU3OY IRRADIATED WITH ENERGETIC IONS

We report an irradiation effect on the c-axis lattice parameter in EuB a2Cu3Oy oxide superconductors when irradiated with ions of energy rang ing from 0.85 to 200 MeV. For the irradiation with low energy (0.85-2 MeV) ions, the defect production and the resultant c-axis lattice expa nsion were dominated by elastic collisions. On the other hand, for irr adiation with high energy (120-200 MeV) ions, the change in the c-axis lattice parameter was found to be much greater than expected from the elastic displacement of target atoms. For high energy ion irradiation we could observe an excessive increase of the c-axis lattice paramete r reflecting additional production of defects which can be attributed to the electronic excitation. The large increase in the c-axis lattice parameter due to high energy ion irradiation should be taken into acc ount for the study on the interaction between vortices and irradiation -induced defects.