Promotion of Epitaxial Growth and Enhanced <italic>J</italic>c by Coaddition of Br and Metals (Zr, Sn, Hf) to the Fluorine-Free MOD Processed YBCO Films

Abstract

Coaddition of Br and metals (M), where M = Zr, Sn, Hf, was attempted for YBCO films prepared by the fluorine-free metal-organic decomposition method. It was revealed that Br-addition, which subsequently forms textured Ba 2 Cu 3 O 4 Br 2 oxybromides in the film, promotes the biaxial alignment of the YBCO crystals. Although M-addition did not improve Jc owing to the serious degradation of crystallinity, (Br, M)-coaddition was found to largely enhance flux pinning properties by the suppression of the random crystal growth. The pinning force density at 40 K in 4.8 T reached ~62 GN/m 3 for (Br, M)-coadded YBCO films. This value is more than three times large compared to that of additive-free YBCO films.