A Study of Excess Conductivity for Hollow TSMG YBCO Welded With Solder Material Produced by Different Methods

Two groups of Y123 +
x
% (
x
= 20, 25, 30) Y211 samples were produced by the top-seeded melt-growth (TSMG) method. One group was welded with TSMG Y123 +
x
% (
x
= 20, 25, 30) Y211 + 20%Ag
₂
O solder materials, while the other group was welded with melt powder melt-growth Y123 +
x
% (
x
= 20, 25, 30) Y211 + 20%Ag
₂
O solder materials. A thin slice of solder material containing the same amount of Y211 additive was placed between two TSMG YBCO samples with the same Y211 additive ratio, with the
c
axes in the same direction, and the welding process was performed using a weight on the stacked samples. All welded samples were drilled with the water jet method to make them hollow. The characteristic peaks belonging to YBCO superconducting specimens cut from the welding region were determined. The resistivity measurements were performed with the standard four-probe method at temperatures between 40 and 300 K. The welding region exhibits a homogeneous structure and the current is not interrupted while passing through this region. Therefore, the Ag
₂
O-added solder material facilitated the integration of TSMG YBCO stacks and a good mechanical and electrical welding process was performed. Excess conductivity analysis was carried out to examine the effect of the production method of the solder material on the conductivity properties in the welding region. The critical exponents of the mean field region and short-wave fluctuation region are in agreement with the theoretical values, which shows that the water jet drilling method does not have a negative effect on excess conductivity. In addition, large coherence length (
$\xi c(0$
)) values lead to a decrease in anisotropy and the development of superconducting properties. The results of the research allow more effective use of this type of welded superconducting materials in technology.