Visualisation of environmental degradation in ceramic superconductors using digital speckle photography

Differences in the environmental stability of Bi-2212 textured materials before and after annealing have been evaluated using digital speckle photography. This technique is able to provide information about the 2D evolution of the degradation processes by means of correlation coefficient reductions. The results indicate a faster degradation for as-grown samples. DSP detects this difference in very short times and allows determining the evolution of the process at any instant. The optical results were confirmed by analysing the differences in the samples microstructure and phase compositions by SEM-EDX, XRD and DRIFT techniques. All these techniques show that, in this material, environmental degradation process is associated with the chemical decomposition of the (Sr,Ca)CuO2 phase.