The influence of BaCuO 2 addition in Gd–Ba–Cu–O single-grain superconductors fabricated in air

High quality Gd–Ba–Cu–O single-grain bulks with different BaCuO 2−δ adding contents were grown in air via a hot-seeding melt process. At 77 K, all samples show a well-developed secondary peak effect with high J c values, which are comparable to that of OCMG-processed Ga–Ba–Cu–O samples. The BaCuO 2−δ addition can effectively suppress the Gd–Ba substitution and therefore enhance the superconducting properties. For the sample with a composition of Gd123:BaCuO 2−δ = 1:0.3 in a molar ratio, the J c ( B = 0) and J c,peak ( B = 1.3 T) reach 6.45 × 10 4 A cm −2 and 6.04 × 10 4 A cm −2 , respectively, which are the record high J c values at 77 K for Gd–Ba–Cu–O samples melt processed in air.