Preparation of the c-oriented Nd-Ba-Cu-O/Ag melt-growth sample in air

The growth mechanism of air-processed c-oriented large grain Nd-Ba-Cu-O/Ag superconductor prepared with the hot-seeding technique was studied. We prepared NdBCO by adding 10-30 mol% Nd210 (or 25 wt% Nd422) and 0-10 wt% Ag. Small amounts of CeO₂ have been added to refine the non-superconducting Nd422 inclusions. The melt-texture growth was performed in air with an Ag-free NdBCO seed at an elevated temperature. A c-oriented grain of 20 mm diameter has been obtained, which contained some sub-grains and residual liquid phase. It is found that the residual liquid phases lead to the disintegration of the Nd210-added bulks after melt-growth. The Nd422 size in Nd210-added samples was much smaller than that in Nd422-added samples. The results show that T_c may be depressed with the addition of Ag. However, after a high-temperature Ar heat treatment, the T_c and J_c (H, T) of the Ag-added samples reach 91 K and 2.0 × 10⁴ A cm^-2 at 77 K without external field. These values are higher than those of the Ag-free samples with Nd210 addition.