Effect of chemical etching of copper stabilization layer on the performance and microstructure of REBa2Cu3O7-x coated conductors

Abstract

The etching of metallic layers is a critical step in the preparation of superconducting joints and in the study of the degradation mechanism of the superconducting performance of REBa₂Cu₃O_7-x (REBCO) coated conductors (CCs). The copper stabilization layer and the silver cap layer need to be completely removed from the specified area and retain excellent superconductivity and microstructure. Since REBCO CCs are sensitive to most inorganic solutions, the etching conditions can severely affect the performance and microstructure when using a wet etching process. We have systematically investigated the effects of ferric chloride (FeCl₃) solutions on the crystal structure, microscopic morphology, critical current (I_c) and n-values of REBCO CCs when etching copper stabilization layers, and have obtained etching parameters that hardly degrade I_c of CCs. However, when the etching conditions were varied, we found a significant degradation of I_c and investigated the underlying causes of this degradation. Scanning electron microscopy (SEM), Raman spectroscopy and X-ray diffraction (XRD) analyses showed that the main cause of the superconducting performance degradation is the delamination of the superconducting layer and the increase of oxygen defects in the lattice.