Electrical and Mechanical Characterization of Coated Conductors Lap Joints

Electrical and mechanical characterizations of YBCO coated conductors diffusion joints obtained in a 2 mm wide, Cu stabilizer free commercial tape provided by Superpower Inc. were reported. Two conductor pieces were overlapped for a length of 20 mm and kept in contact under a pressure as high as 80 MPa. A face-to-face approach was used, with or without an additional Ag tape insert. The joint was realized by Ag diffusion at a temperature of 200 and 400??C in N₂ and O₂ atmosphere, respectively. The resistivity of the joint was measured at 77 K in N₂ bath. The mechanical properties of the joint were characterized by means of single-lap tensile test operated at room temperature at a rate of 0.5 mm/min. The best results were obtained by high temperature joining in O₂ atmosphere. The resistivity of the joints was as low as 3.1 ?? 10^-12 ?? m². This value is almost halved if an Ag insert is used. The mechanical properties of the joints are strongly dependent on the use of an Ag insert, since maximum load as high as 60 N can be applied if no additional insert is used. This value enhances to about 100 N when an Ag insert is employed. However, the joint obtained at low temperature in N₂ atmosphere is also interesting since the joint resistivity was slightly increased to 4.7 ?? 10^-12 ?? m² and a maximum load as high as 50 N was obtained indicating that diffusion joints can be safely handled. These results are promising in perspective of oxygen free diffusion joints in Cu stabilized coated conductors.