Silver-doped Y–Ba–Cu–O bulk superconductors fabricated by seeded infiltration andgrowth

Abstract

Silver-doped Y–Ba–Cu–O (YBCO) bulk superconductors have been fabricatedsuccessfully in the form of large, single grains by a seeded infiltration andgrowth (IG) technique. A uniform distribution of silver in the superconductingYBa2Cu3O7−δ (Y-123) phase matrix was achieved by addingAg2O to boththe Y2BaCuO5 (Y-211) pre-form and a liquid source precursor pellet. Although Ag can also bedispersed well in Ag-doped YBCO fabricated by the top-seeded-melt-growth(TSMG) technique, bulk samples prepared by the IG technique typically exhibitsignificantly lower porosity due to the absence of the formation of oxygen duringthe peritectic decomposition process within the Y-211 pre-form. This yieldssamples with potentially enhanced current-carrying ability. The density of voidsin bulk samples can be decreased further by adding metallic Ag, rather thanAg2O, to the Y-211 pre-form in the IG process. The distribution of Y-211 in the Y-123matrix in samples fabricated by both IG and TSMG is rather inhomogeneous. Asa result, the superconducting properties of individual small samples cut fromlarge parent grains are similar for samples fabricated by both IG and TSMG.