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)

Abstract

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 SrTiO3(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, Ba2Cu3O4X2, 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 Jc were reproducibly obtained, even when an impurity metal, M, was co-added, while the addition of M without X did not greatly improve Jc owing to the poor bi-axial orientation of the YBCO crystals. Our results suggest that the addition of Br more effectively enhances Jc 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.