Effect of the Heat Treatment Applied During the Welding Process on Superconducting Properties of the Welded YBCO Samples

Two Y123 samples labeled as Y1 and Y2 were welded using a Y123 solder reagent labeled as YA. Y1 and Y2 samples were produced by the top-seeded melt growth method in Y123 + 30 wt.% Y211 composition, and YA was produced by melt powder melt growth method in Y123 + 30 wt.% Y211 + 20 wt.% Ag
₂
O composition. Artificial grain boundaries were created with the solder reagent, and a pressure source was used during the welding process to obtain larger bulk superconducting samples. The welded sample was cut horizontally into three slices, which were named WY1, WY2, and WYA from top to down. Some superconducting properties, such as superconducting transition temperature (
T_c
) and critical current density (
J_c
), of the welded samples were investigated before and after the welding process. Good quality welds were obtained mechanically, and the
T_c
values determined from the resistivity measurements are around 92 K for all specimens, indicating that the welding has no negative effect on
T_c
. The calculated
J_c
values are 13.71, 12.08, and 9.97 kA/cm
²
for Y1, Y2, and YA specimens cut from the samples before the welding process, respectively, whereas the
J_c
values are 2.33, 21.13, and 14.42 kA/cm
²
for WY1, WY2, and WYA specimens cut from the welded sample after the welding process, respectively. It was observed that the welding process enhanced the superconducting properties of the welding region. After the welding process, the superconducting properties of the high-quality samples oriented in the
c
-axis decreased less than those samples that do not have a preferential orientation or grain structure.