MELT PROCESSING FOR STRONG FLUX-PINNING IN RE-BA-CU-O (RE ND,SM,EU,GD) SUPERCONDUCTORS

Factors affecting a characteristic flux pinning in light rare earth (R E)-Ba-Cu-O (RE: Nd, Sm, Eu, Gd) superconductors fabricated by the oxyg en-controlled-melt-growth (OCMG) process have been investigated throug h a comparative study. At 77K and for the applied field parallel to th e c-axis of the sample (H//c), the flux pinning of all OCMG-processed REBa(2)Cu(3)O(y) (RE 123) samples studied was very sensitive to the ox ygen partial pressure (P-O2) controlled during the melt growth and thu s, with lowering P-O2, the peak field (B-pk) in the M-H loops shifted to a high field and the irreversibility line (IL) shifted to a high H- T region. For a Nd123 sample, as the oxygen annealing temperature incr eased above 300 degrees C, both B-pk and IL were systematically depres sed. However, B-pk for all systems was insensitive to the amount of th e second phase (Nd4Ba2Cu2O10 (Nd422) and RE(2)BaCuO(5) (RE211) for the other) inclusion in the superconducting RE123 matrix, supporting that the characteristic flux pinning is due to the superconducting matrix.