TEM OBSERVATION OF NEUTRON-INDUCED COLLISION CASCADES IN BI-2212 SINGLE-CRYSTALS

Several high-quality single crystals of the superconductor Bi2Sr2CaCu2 O8 (Bi-2212) were exposed to three different neutron fluences in the c entral irradiation facility of the Triga Mark II reactor in Vienna in the form of pre-prepared and pre-characterized transmission electron m icroscopy (TEM) samples as well as in full crystalline form. We find t hat the radiation damage produced in Bi-2212 is very similar to that f ound previously in YBa2Cu3O7-delta (Y-123) single crystals. The diamet er of the amorphous cascade volume is 3.5 nm, the inwardly directed st rain field is of approximately the same size, the density of cascades is 3.7 x 10(22) m(-3) per 10(22) neutrons m(-2) (E > 0.1 MeV) and thei r concentration scales linearly with neutron fluence. Based on these r esults and in view of the similar displacement cross-sections of the c onstituents of other high temperature superconductors, we conclude tha t the neutron-induced defects in high-T-c materials will generally hav e a diameter (including the strain field) of 5-7 nm. (C) 1998 Elsevier Science B.V.