X-RAY IMAGING AND OPTICS Evidence of Ion Diffusion at Room Temperature in Microcrystals of the

Single crystals of the Bi2Sr2CaCu2O8+δ (Bi-2212) high-Tc superconductor can be grown in samples whose length ( ≥ 500 µm) is much greater than both their width and their thickness (whiskers). These kinds of samples have recently attracted remarkable interest from the point of view of both basic and applied physics. In fact, they have proved to be suitable systems for the study of the excess conductivity above Tc and of the transport properties along the c axis because of their high quality and small sizes [1]. Bi-2212 whiskers undergo a significant increase in the in-plane resistivity when aged at room temperature, most likely because of the oxygen loss [2]. Variations in the O non-stoichiometry of Bi-2212 whiskers must be accompanied by a change of the Cu oxidation state t