부산대학교 도서관

The fabrication of RE Ba 2 Cu 3 O 7- δ ( RE BCO, RE = rare earth elements) bulks in single grain form and their flux pinning depend strongly on the initial conditions of the RE 2 BaCuO 5 ( RE 211) phase used as precursor. We recently demonstrated a novel method of employing high-energy ultrasonication to create fine RE 211 particles ( RE 211 Ultra ) with irregular shapes along with sharp edges and damaged surfaces. The developed method is convenient, free of contaminants, and low cost as compared to other methods currently utilized. Integrating these RE 211 Ultra in the top-seeded melt growth (MG) method, we improved the initial peritectic growth reactivity and thus, the superconducting properties of YBCO and GdBCO bulk single grains. Melt growth experiments were carried out on different RE BCO ( RE = Y and Gd) systems with the addition of 30 mol% of RE 211 Ultra . The RE 211 Ultra particles boosted the initial peritectic reaction i.e., growth rate during the MG process due to their sharp edges, and damaged surfaces in their nanometer size. The left-back fine-sized RE 211 particles increased the interfacial defects and hence, the flux pinning. In the present work, we summarize the effect of ultrasonication of RE 211 particles, their impact on peritectic reaction and improvement of superconducting properties of various REBCO bulks. Employing RE 211 Ultra powders for infiltration growth (IG) processing, we enabled a good control of the RE 211-phase content and particle size in the final bulk YBCO single grains. The field-dependence properties of MG and IG-processed of YBCO superconductors are significantly improved without any additional chemical addition/doping.