Flux pinning by cation vacancies in Bi 2(Sr,Ca) 3Cu 2O 8+d

We present improved flux pinning in cation nonstoichiometric Bi ₂(Sr,Ca) ₃Cu ₂O _8+d having cation vacancies introduced by the solid solution. A cation deficiency on any one of the three cation sublattices substantially increases the intragranular critical current density as measured by magnetic hysteresis. Although no thermal history effect is observed for the cation stoichiometric composition, reduced temperature annealing greatly enhances flux pinning in the cation deficient compositions. The cation vacancies and/or their clusters may be responsible for flux pinning in this compound.