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

Sm1+xBa2−xCu3+yO7−δ (SmBCO) films were directly deposited on the epi-MgO/IBAD-MgO/Y2O3/Al2O3/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 Ic of 52 A (corresponding to Jc = 1.6 MA/cm2 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 Ic 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 Ic, 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 Ic. The optimum composition ratio can be found by analyzing films deposited with variable deposition rates of each depositing element.

► SmBCO films with gradient composition were deposited on the epi-MgO/IBAD-MgO template.
► The composition dependence of Ic was found to be dependent on the composition ratio.
► The composition ratio affects the amount of a-axis orientation.
► High Ic values were observed at the region with dense microstructure.