Improved Superconductivity and Structural Mechanism Analysis of Y0.55Gd0.45Ba2Cu3O7-x/SrTiO3/Y0.55Gd0.45Ba2Cu3O7-x Tri-layer

REBa2Cu3O7-a (REBCO) coated conductors has great potential in the field of energy transmission and device applications. However, one of the main obstacles is the limitation of critical current and critical current density of REBCO coated conductors, which restricts its wide application in the above fields. Herein a method to improve the thickness effect based on sandwich structure and SrTiO3 (STO) interlayer has been proposed. The sandwich structural coated conductor displayed better superconductivity. Compared with single-step and multi-step Y0.55Gd0.45Ba2Cu3O7-x (YGdBCO) film, the critical current of YGdBCO/STO/YGdBCO increased by 52.4% and 25.3%, respectively. Meanwhile, the micro-mechanism of current transport in the superconducting film has been investigated and discussed in detail. The segregation and diffusion of elements in the superconducting film and the metallic parts formed within the STO interlayer connected the top and bottom layers and provided channels for current transport. Thickness effect was significantly improved through this method under the mechanism discussed, which should help to improve the large-scale application of REBCO coated conductors.