Flux pinning enhancement by room temperature plastic deformation on Hg-based ceramic superconductors

We report on the superconducting properties of plastically deformed Hg0.82R e0.18Ba2Ca2Cu3O8+delta (T-c = 133 K) ceramics. The critical temperature, lo w field susceptibility, and irreversible magnetization have been carefully analyzed as a function of the plastic strain. It is shown that plastic defo rmation does not alter T-c, but results in a marked decrease of the screene d sample volume; this is likely related to the reduction of the Brain size by cracking. After correcting for this effect, the irreversible magnetizati on indicates an enhancement of flux pinning due to the deformation-induced defects - mainly dislocations; relaxation measurements confirm this result. (C) 1999 Elsevier Science B.V. All rights reserved.