Refinement of Nd-422 particles in Nd-Ba-Cu-O bulk superconductor

We have investigated the effect of oxygen partial pressure, the initial composition, and the addition of CeO/sub 2/ and/or Pt on the grain growth of Nd/sub 4/Ba/sub 2/Cu/sub 2/O/sub 10/ (Nd-422) in the Ba-Cu-O liquid. Logarithmic plots of the mean diameter of Nd-422 under various oxygen levels as a function of the holding time showed the power law behavior with the slope of 1/3, which suggested that the grain growth of Nd-422 could be explained in terms of the Ostwald ripening theory. A reduction of oxygen partial pressure, the shift of the initial composition toward Ba-rich direction, and a combined addition of Pt and CeO/sub 2/ could suppress the coarsening of Nd-422. Furthermore, a combination of these techniques was found to be effective in refining the Nd-422 in the Nd-123 matrix, which led to an enhancement of J/sub c/ values.