3,5 GeV xenon ion irradiation effects in the superconducting oxide YBa2Cu3O7δ(δ≤0.1): A HREM investigation

Polycrystalline sinters of YBa2Cu3O7-δ (δ≤0.1) superconductor have been irradiated by 3.5 GeV Xe ions and investigated by high resolution electron microscopy (HREM). Discontinuous tracks due to the high energy density deposited into electronic excitation and ionization have been characterized. They exhibit a dotted microstructure, similarly to that previously described for magnetic insulators. Such tracks seem to act as centers of nucleation and growth of defects through the Cu and BaO layers, perpendicularly to the c axis, leading either to local contrast modulations with a doubling of the ''a'' parameter or to the amorphization of the slices when a critical density of defects is exceeded. The appearance of these amorphous layers should be responsible for the rapid Tc decrease for fluences higher than 3x1012 Xe/cm2. (orig.)