THE USE OF PHASE-DIAGRAMS FOR THE ENGINEERING OF FLUX-PINNING CENTERSIN BI2SR2CACU2O8 CERAMICS

From considerations of the phase equilibrium diagram of the system Bi2 O3-PbO-SrO-CaO-CuO, different annealing procedures were developed to p recipitate various second phases in high-temperature superconducting B i2Sr2CaCu2O8 ceramics with different chemical compositions. In each ca se, the precipitation results in an increase of the intragranular crit ical current density of the samples which is believed to express impro ved pinning properties of the superconducting ceramics, in particular an increased pinning energy, which reduces the probability for thermal ly activated depinning.