The Effect of the CeO2 Buffer Layer Thickness on the Jc of YBa2Cu3O7 Films Prepared on CeO2/YSZ/CeO2 Buffered Ni-electroplated Cu Tapes

Abstract

We investigated the effect of the CeO2 buffer layer thickness on YBCO films prepared on CeO2/YSZ/CeO2-buffered Ni-electroplated Cu tapes. The thickness of the CeO2 layer was found to be critical. The thickness of the CeO2 seed layer was varied to be from 80 to 300 nm and the thickness of the CeO2 cap layer was varied to be from 40 to 80 nm. To avoid the formation of cracks, we found that the thicknesses of the CeO2 seed layer and CeO2 cap layer must be less than 80 nm and 40 nm, respectively. Detailed SEM and AFM observations indicated a possible relation between the cause of crack formations and the thermal expansion coefficient differences of the films and the substrate. A smooth, continuous and crack-free surface was obtained on CeO2 (40 nm)/YSZ/CeO2 (80 nm) Ni-electroplated Cu tape. The YBCO films prepared on the CeO2/YSZ/CeO2-buffered Ni-electroplated Cu tapes revealed a transport Jc exceeding 3.6 MA/cm2 at 77 K in a self-field.