The Effects of Gd-Free Impurity Phase on the Aging Behavior for the Microwave Surface Resistance of Ag-coated GdBa2Cu3O7−δ at Cryogenic Temperatures

다국어 초록 (Multilingual Abstract)

High-TC GdBa2Cu3O7−δ (GdBCO) superconductor has been popular for making superconductive tapes that have much potentialfor various fields of large-scale applications. We investigated aging effects on the microwave surface resistance (RS) of Ag-coatedGdBCO layer on Hastelloy substrate, so called GdBCO coated conductors (CCs), and Ag-coated GdBCO films on LaAlO3(LAO) single-crystal substrates at cryogenic temperatures and compared them with each other. Unlike the RS of Ag-coatedGdBCO films showing significant degradation in 4 weeks, no significant aging effects were found in our Ag-coated GdBCOCCs aged 85 weeks. The reactive co-evaporation deposition and reaction (RCE-DR) method was used for preparing the AgcoatedGdBCO CCs. Such durability of the Ag-coated GdBCO CCs in terms of the RS could be explained by existence of aprotective impurity phase, i.e., Gd-free Ba–Cu–O phase as confirmed by transmission electron microscopy study combined withthe energy-dispersive X-ray spectroscopy measurements. Although the scope of this study is limited to the Ag-coated GdBCOCCs prepared by using the RCE-DR method, our results suggest that a solution for preventing the aging effects on transportproperties of other kinds of Ag-coated GdBCO CCs could be realized by means of an artificially-grown protective impurity layer.
Graphical AbstractKeywords Aging effect · GdBa2Cu3O7−δ · Surface resistance · Coated conductor · Film* Sang Young [e-mail] author

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