We investigated the effect of oxygen partial pressure pO 2 during melt-and-solidification heat treatment on the superconducting properties of grain oriented Bi-2212 thick films. T c and c-axis parameter decreased with increasing pO 2 , indicating the samples were in the over-doped state. The heat treatment temperature which gave highest J c increased with increasing pO 2 . This was explained by the increase of the solidification temperature of Bi-2212 with pO 2 . Both the resistive J c and intergrain J c estimated from the dc magnetization increased with increasing pO 2 when the samples were melt-solidified under an optimum condition for each pO 2 . Amplitude dependence of ac susceptibility suggested that the coupling of Bi-2212 grains was improved with increasing pO 2 . Irreversibility field B irr below ϳ60 K was also enhanced with increasing pO 2 . Low temperature annealing under high pO 2 after the melt-solidification also increased the oxygen content in Bi-2212 and hence B irr . However, the annealing did not change the amplitude dependence of ac susceptibility, and transport J c at 4.2 K was almost independent of the annealing. The results indicate that the increase of J c at 4.2 K with increasing pO 2 during melt-solidification is primarily attributed to the improvement of the grain couplings.
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