Effect of the composition on the superconducting properties of IBAD-MgO SmBCO coated conductors with superconducting film directly deposited on epi-MgO layer

Abstract Sm 1+ x Ba 2− x Cu 3+ y O 7− δ (SmBCO) films were directly deposited on the epi-MgO/IBAD-MgO/Y 2 O 3 /Al 2 O 3 /Hastelloy template by co-evaporation using the evaporation using drum in dual chambers (EDDC) system without the buffer layer in order to investigate the effect of the composition ratios on superconducting property, microstructure and texture of SmBCO film. The films with gradient composition ratios of Sm:Ba:Cu were deposited using a shield with an opening which was placed between the substrate and the boats. The highest I c of 52 A (corresponding to J c  = 1.6 MA/cm 2 and a thickness of 800 nm) was observed at 77 K in self field at a composition x  = 0.01–0.05 and y  = −0.23 to −0.46. When the composition ratio is outside this range, the I c value rapidly decreased. The superconducting critical current was highly dependent on the composition ratio. As the composition ratio is farther away from that of the highest I c , the SmBCO (1 0 3) peak intensity increased and the amount of a -axis oriented parts increased. A dense microstructure with round-shape grains was observed in the region showing the highest I c . The optimum composition ratio can be found by analyzing films deposited with variable deposition rates of each depositing element.