Greatly enhanced flux pinning properties of fluorine-free metal–organic decomposition YBCO films by co-addition of halogens (Cl, Br) and metals (Zr, Sn, Hf)

Additive-free YBCO films, as well as those with halogen ( X ) added, metal ( M ) added and ( X , M ) co-added, have been prepared by the fluorine-free metal–organic decomposition method on SrTiO 3 (100) single crystalline substrates, where X = Cl, Br and M = Zr, Sn, Hf. It was revealed that the addition of both Cl and Br to the starting solution resulted in the generation of oxyhalide, Ba 2 Cu 3 O 4 X 2 , in the YBCO films, and that the oxyhalide was found to promote the bi-axial orientation of the YBCO crystals. By adding a decent amount of Cl or Br, highly textured YBCO films with high J c were reproducibly obtained, even when an impurity metal, M , was co-added, while the addition of M without X did not greatly improve J c owing to the poor bi-axial orientation of the YBCO crystals. Our results suggest that the addition of Br more effectively enhances J c than the addition of Cl. The pinning force density at 40 K in 4.8 T reached ∼55 GN m −3 with the co-addition of (Br, M ). This value is much larger than that of the pure YBCO film, reaching ∼17 GN m −3 .