Harmonic analysis of AC magnetic susceptibility of YBCO/Ag produced by chemical amorphous citrate route

The dependence of AC magnetic susceptibility on temperature and magnetic field amplitude of YBCO/Ag superconductors produced by a modified citrate route is studied. Superconducting powders have been prepared with nine different heat treatments, sintered and characterized structurally and magnetically. X-rays analysis, scanning electron microscopy and scanning Auger microscopy show the compositional purity and homogeneity, the size of the grains, and the way silver is dispersed in the sample. AC susceptibility is interpreted in terms of a critical-state model providing a quantitative estimate of the critical current density and qualitative insight on the flux dynamic inside the samples.