Evidence of ion diffusion at room temperature in microcrystals of the Bi2Sr2CaCu2O8+delta superconductor

Bi2Sr2CaCu2O8+delta (Bi-2212) whiskers undergo a significant increase in the in-plane resistivity when aged at room temperature, most likely because of the oxygen loss. Variations in the O non-stoichiometry of Bi-2212 whiskers must be accompanied by a change of the Cu oxidation state to guarantee the electrostatic neutrality. To verify whether the variation of the local Cu oxidation state, induced by O diffusion, is accompanied by a cation migration or not, we have combined micro-XANES and micro-XRF experiments at ID22. Also the c-axis value has been monitored by micro-XRD. Laboratory AFM study support ID22 data.