Nd1+x Ba2-x Cu3O7-d Single Crystals Flux-grown at Various Undercoolings and Their Superconducting Properties

To identify the relationship between the flux pinning properties and the process conditions in the Nd1+x Ba2-x CU3O7-d (Ndl23SS) superconductors, single crystals were flux-grown in 1%O2-Ar atmosphere using an isothermal crystallization procedure at various undercoolings (∆T) from 10 to 35 °C The flux was composed of 20 mol% NdBa2Cu3O7-d (Ndl23) and 80 mol% Ba3gCu5O8 (035). For ∆T ≤ 25 °C, flux-grown Ndl23 single crystals exhibited aspect ratio w/t smaller than 1, where w and t correspond to the lengths along the a- (or b-) and c-axis respectively, transition temperature T c ≈ 95 K with transition width ≈ 1 K, the peak field (B pk) ≈ 2 – 3 T and the irreversibility field (B in) much higher than the experimental limit 7 T. In contrast, for ∆T ≥ 30 °C, Ndl23 single crystals exhibited a slight increase in w/t, a slight decrease in T c with broader transition width, and a reduction in B pk and B in.