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

Abstract

We have studied Bi-2212 microcrystals aged at ambient conditions for 40 days. Combined x-ray absorption near edge structure and x-ray fluorescence measurements with micrometer space resolution show both an increase of Cu$^{+}$ with respect to Cu$^{2+}$ and an enrichment in Cu vs Bi and Sr cation content near the sample edges in the b-axis direction. A parallel study on an electrically contacted sample has indirectly detected the O loss, observing both a resistivity increase and an increase in sample thickness near the edges. We conclude that the O out-diffusion along the b-axis is accompanied by Cu cation migration in the same direction.