Soldering of MT-YBCO: method to produce superconductive junctions

Abstract

A method of soldering of melt-textured YBa2Cu3O7-d -based (MT-YBCO) superconductive blocks using a TmBaCu3O7-d (Tm123) powder has been suggested. The method excludes stages of slow cooling during soldering and preparation of auxiliary layers. To estimate the critical current density (jc) through the obtained junction, we have drilled rings from single-domained MT-YBCO blocks, cut into two pieces along the diameters and soldered using a Tm123 powder. The critical current density, jc, (estimated using vibrating sample magnetometer) through the soldered ring was 34 kA/cm^2 in 0 T field at 77 K, which turned out to be even higher by a factor of approximately 1.5 than that through the single-domained material. The increase in jc through the soldered ring has been observed up to the 2.5 T field, while in the higher fields some decrease of jc took place. As a result of the field mapping of the trapped magnetic flux in soldered ring using a Hall probe, we obtained a regular truncated cone and the maximal level of trapped field for the ring 8 and 4 mm in outer and inner diameters was about 80 mT.