Study on the fabrication and the characteristics of $Sm_1Ba_2Cu_3O_{7-δ}$ high Tc superconducting films

Abstract

The growth properties and field dependent critical current densities of $Sm_{1+x}Ba{2-x}Cu_3O{7-\delta}$(SBCO) films on biaxially textured Ni tapes with $CeO_2/YSZ/CeO_2$ buffer layers were investigated.The window of substrate temperature($T_s$) for c-axis normal growth in 5mTorr of oxygen pressure were wider than $150^\circ C$. The upper limit of $T_s$-window was much higher than that of $Y_1Ba_2Cu_3O_{7-\delta}$(YBCO) films. Around the low limit of $T_s$, SBCO films grew in [103] normal textures. The zero field critical currents ($J_c$) were slightly smaller than those of YBCO films, while in high field regions critical current densities are much higher and the estimated pinning energies were less dependent on external fields than that of YBCO.

We observed that a $Sm_1Ba_2Cu_3O_{7-\delta}(SBCO) film grown on a YSZ substrate with arbitrarily oriented crystal was textured in a single crystalline orientation, while there seems to be no noticeable relation between the crystalline orientations of the film and the substrate. The SBCO[103] axis was close to the surface normal axis. On the other hand, we could not grow an YBCO film on the same substrate, which implies the growth of SBCO film is more stable than YBCO film on that substrate. The qualities of SBCO films grown at substrate temperatures across a wide range of $680^\circ C$ ~ $750^\circ C$ were similar. The critical current density of this SBCO film was smaller than that of SBCO film on a RABiTS-Ni tape, which is several times smaller than that of the YBCO film of coated conductor.

The transport properties of $Sm_1BA_2Cu_3O_{7-\delta}$ films, which were grown on the bi-crystalline $SrTiO_3$ substrates of $24^\circ$, $30^\circ$, $36.8^\circ$ and $45^\circ$ misorientation angles, were investigated by the measurements of the Ⅰ-Ⅴ curves at 77K under various magnetic fields. When the voltages were high enough, the Ⅰ-Ⅴ curves became straight. The resistances estimated from the slopes were almost independ...