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Joint techniques are important to manufacture long superconducting tapes. It has been reported that GdBa 2 Cu 3 Oy (GdBCO) coated conductors have higher critical current and critical temperature than YBCO. However, it was reported that the joint resistance of GdBCO was found higher than that of YBCO. In this paper, the elemental distribution maps were investigated to examine the cause of joint resistance. Electron microscopy analysis of GdBCO showed the reduction of oxygen in GdBCO layer. This oxygen reduction may cause degradation of superconducting properties and increase of Ag-GdBCO interfacial resistance, which may have led higher joint resistance in Ag/GdBCO.