Effect of BaO2 and fine Gd2BaCuO7−δ addition on the superconducting properties of air-processed GdBa2Cu3O7−δ

Single-domain GdBa2Cu3O7−δ (Gd123) bulk superconductors were fabricated in air and studied with different BaO2 contents and Gd2BaCuO7−δ (Gd211) initial particle sizes. The experiments showed that BaO2 addition effectively suppressed the Gd/Ba substitution and therefore enhanced superconducting properties such as Jc and Birr. An optimum addition amount is Gd123:BaO2 = 1:0.1 molar. By employing fine Gd211, Jc at low magnetic fields is further enhanced. At B = 0 and 77 K, Jc reached 86 000 A cm−2, which is a record high Jc value for melt-processed Gd123 bulk samples in air.