Collective stacking faults and their effect on flux pinning in powdermelting processed Y0.6Ho0.4Ba2Cu3Oysuperconductors

Abstract

We have fabricated the highly textured Y0.6Ho0.4Ba2Cu3Oybulk superconductors by a powder melting process (PMP) method and investigatedthe microstructure and flux pinning characteristics. The microstructuralobservations show that there are many collective `stair like' stacking faultsin our sample, which is quite different from other melt-processedYBa2Cu3Oy. The formation of these stacking faults is discussed. It isfound that the density of stacking faults is dramatically reduced when thesample is annealed at high temperature. After annealing, the critical currentdensity and irreversibility line are significantly decreased in H∥cand H∥ab at various temperatures. These results clearly indicatethat these stacking faults are very effective pinning centres in the PMP YBCOsuperconductors over a wide temperature and field range. The effect ofstacking faults on the flux pining is sensitive to temperature and magneticfield. Also, the influences of stacking faults on the relaxation rate, theapparent pinning potential and the anisotropy of critical current are brieflystudied.