Effect of Annealing on HTS Tapes with a Cerium Oxide Layer Inserted between the REBaCuO and Silver Layers

Abstract

This paper presents extensive electrical, microstructural and chemical characterizations of HTS coated conductor samples in which an oxide layer (CeOx) has been added between the superconductor (GdBaCuO) and the silver (Ag) layers, in an attempt to increase the interfacial resistance between these two conductive layers. This increase of interfacial resistance is required to realize the current flow diverter (CFD) architecture in HTS tapes. All samples in this paper have been characterized before and after performing an annealing in oxygen atmosphere. The purpose of the annealing was to reduce the interfacial resistance generated by the CeOx layer, in order to achieve a proper value for the CFD architecture. Samples with different thicknesses of CeOx, namely 0, 10, 35 and 100 nm, have been produced and characterized. The critical current and the critical temperature have been measured to determine the quality of the superconducting layers, while cross-section transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) have been used to monitor the impact of the annealing. The results show a clear degradation of the superconducting layer for samples with a thick layer (≥ 35 nm) of CeOx after annealing at 450 oC. According to the EDS results, a reduction of the amount of barium is observed in the superconducting layer, which could explain the observed reduction of the critical current.