Effects of Melting Diffusion and Annealing in Oxygen on Superconducting Characteristics of GdBCO Coated Conductors: Preliminary Results

This study examined the superconducting properties of GdBCO coated conductor tapes before and after melting diffusion and subsequent annealing in oxygen. Such investigation is necessary in order to determine the optimal parameters of these processes for the future development of a superconducting joint between coated conductors. The melting diffusion process under a reduced oxygen partial pressure (P_O2) at 850 °C for 60 s enabled the maintenance of the c-axis orientation of Gd123 with few secondary phases such as CuO and BaCuO₂, resulting from partially melted GdBCO. To restore the oxygen lost during the melting diffusion process, an additional oxygenation annealing process was conducted. The critical current of the GdBCO CC tape oxygenation annealed at 600 °C for 50 h and then at 500 °C for 200 h sequentially was 108 A, indicating that the superconducting properties were considerably recovered. Based on the optimal joining parameters obtained in this study, future studies on the superconducting joint of the GdBCO CC will be carried out.