Enhancement of flux pinning in GdBa2Cu3O7−y bulks prepared by nanoparticle-powder-assisted method

Abstract

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.