Enhancement of flux pinning in GdBa_2Cu_3O_(7-y) bulks prepared by nanoparticle-powder-assisted method

摘要

High quality GdBa2Cu3O7-y(Gd123) textured bulks with Nd2BaCuO5(Nd211) nanoparticle precipitations have been fabricated by a nanoparticle-powders-assisted MTG(melt-textured-growth) technique.The high density nanoscale flux pinning sites were introduced into Gd123 by mixing Nd211 nanoparticle powders(about 20-50 nm) with Gd123 nano-precursors before the MTG process.Microstructural analyses reveal that a large number of Nd211 nanoparticles with a size around 50-150 nm were inserted in the Gd123 matrix,forming a kind of superconducting nanocomposites.The critical current density at 77 K is systematically increased and the flux pinning behavior is significantly improved.The scaling behavior of the flux pinning force shows a magnetic field dependent feature with a peak located at hp≈0.4.This may be the fingerprint of melt-textured 123 compounds,which cannot be interpreted by the simple superposition of different types of elementary pinning sources.