Degradation of thin films of YBa2Cu3O7 by annealing in air and in vacuum

Heating-Induced Performance Degradation of REBa2Cu3O7–x Coated Conductors: An Oxygen Out-Diffusion Scenario with Two Activation Energies

“…In recent years, high-performance RE Ba 2 Cu 3 O 7– x ( RE BCO, where RE = rare earth element) coated conductors (CCs) have become more and more widespread on the market, opening the possibility to employ them routinely in different domains as high-field magnets (in particular for Tokamak fusion energy reactors, nuclear magnetic resonance devices, and high-energy particle colliders), electric-power generation (superconducting motors), and electric-power distribution (superconducting grids). − All these applications typically require to heat the CC above room temperature, for example, when soldering the current leads, when realizing a joint, or when impregnating a coil. − Increasing the temperature of RE BCO CCs can lead to modifications of their superconducting properties. In particular, a reduction of the critical current has been reported when heating the CC at temperatures as low as ∼150 °C. − Short-lasting overheating in the 200 °C range due to uncontrolled quenches at cryogenic temperatures was observed to degrade the critical current, too . The origin of this phenomenon has been qualitatively ascribed to elemental oxygen out-diffusion processes that modify the stoichiometry of the superconducting layer.…”

Composite Heat Sink Material for Superconducting Tape in Fault Current Limiter Applications

“…A use of higher E max up to 150 V m −1 could considerably reduce the required superconductor length with a significant saving impact on overall costs. The ability of the CC tape to withstand higher electric field predominately depends on amount of generated heat, which can rapidly (typically in 50 ms) overheat the tape to more than 250 • C. Such high temperatures may permanently degrade the superconductor [11], and in the worst case, the HTS cannot retrieve its superconducting state after the fault. Therefore, the thermal stability of commercial CC tapes is an important issue.…”

Thermal Cycling of (RE)BCO-Based Superconducting Tapes Joined by Lead-Free Solders

“…The highest temperature that the SCTs experienced in this study during reflow was 245 °C, which was only slightly above the maximum value of 240 °C recommended by the SuperPower company [ 37 ]. According to [ 38 ], 0.6 μm thick YBCO (which is (RE)BCO with (RE) = yttrium) coated film heated for 30 min at 250 °C undergoes 10% increase of its resistance at room temperature due to oxygen diffusion out of the epitaxial film, while the change of critical current density was negligible. Therefore, we expect that the heating of SCTs (from any manufacturer) to 245 °C for tens of seconds should not cause significant (RE)BCO degradation.…”

“…Thus, soldered joints were prepared, each 13 cm long, with 3 cm of face-to-face overlap in the middle [ 12 ], with a joint area of 120 mm 2 or 180 mm 2 for 4 mm or 6 mm wide tapes, respectively ( Figure S2 ). In the whole course of joint preparation, attention was always paid to (1) minimize the time the (RE)BCO layer experiences temperatures above 200 °C, which is the onset of the (RE)BCO degradation ([ 17 , 38 ]) and (2) the joints would experience minimum mechanical load, such as bending or tension.…”