MOD Buffer/YBCO Approach to Fabricate Low-Cost Second Generation HTS Wires

摘要

The metal organic deposition (MOD) of buffer layers on RABiTS substrates is considered a potential, low-cost approach to manufacturing high performance Second Generation (2G) high temperature superconducting (HTS) wires. The typical architecture used by American Superconductor in their 2G HTS wire consists of a Ni-W (5 at.%) substrate with a reactively sputtered ${rm Y}_{2}{rm O}_{3}$ seed layer, YSZ barrier layer and a ${rm CeO}_{2}$ cap layer. This architecture supports critical currents of over 300 A/cm-width (77 K, self-field) with 0.8 $mu{rm m}$ YBCO films deposited by the TFA-MOD process. The main challenge in the development of the MOD buffers is to match or exceed the performance of the standard vacuum deposited buffer architecture. We have recently shown that the texture and properties of ${rm MOD-La}_{2}{rm Zr}_{2}{rm O}_{7}$ (LZO) barrier layers can be improved by inserting a thin sputtered ${rm Y}_{2}{rm O}_{3}$ seed layer and prepared MOD deposited LZO layers followed by MOD or RF sputtered ${rm CeO}_{2}$ cap layers that support MOD-YBCO films with ${rm I}_{rm c}$''s of 200 and 255 A/cm-width, respectively. Detailed X-ray and microstructural characterizations indicated that ${rm MOD-CeO}_{2}$ cap reacted completely with MOD YBCO to form ${rm BaCeO}_{3}$. However, sputtered ${rm CeO}_{2}$ cap/MOD YBCO interface remains clean. By further optimizing the coating conditions and reducing the heat-treatment temperatures, we have dem-onstrated an ${rm I}_{rm c}$ of 336 A/cm with improved LZO layers and sputtered ${rm CeO}_{2}$ cap and exceeded the performance of that of standard vacuum deposited buffers.