Improved Flux Pinning Properties of Bi-Based Superconductors by Dilute RE-Doping

Flux pinning properties of lead doped Bi2212 single crystals and Bi2223 sintered bulks were improved by low level light rare earth (LRE) doping to the Sr-site. The dilute LRE doping effects were prominent below ~30 K for Bi(Pb)2212 single crystals and below ~60 K for Bi(Pb)2223 sintered bulks. These results suggest that effective point-defect-type pinning sites were successfully introduced by small amount of LRE-doping. The improvement of flux pinning properties by dilute LRE-doping was the most remarkable when the carrier doping state was nearly optimal and the LRE doping level was ~0.5% for Sr-site.