We have investigated the effect of high-temperature annealing on the superconducting transition and the flux pinning properties of Nd123 melt-textured in 1% O2-Ar. After the high-temperature annealing, a decrease in Jc was observed in most samples even though no appreciable change was observed in Tc. TEM observations and EDX analysis show that the spatial variation of the Nd/Ba ratio almost disappears after high-temperature annealing. Therefore, the observed change in Jc-B properties can be understood by a reduction in the field-induced pinning due to homogenization of Nd/Ba substitution regions. These results strongly support the idea that the secondary peak effect and high pinning performance in Nd123 can be ascribed to the presence of Nd/Ba spatial variation.
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