Demonstration of high current density YBCO coated conductors on RE2O3-buffered Ni substrates with two new alternative architectures

In continuation of our effort to develop single buffer layer architectures for YBCO (YBa 2 Cu 3 O 7-y ) coated tape conductors, we have studied RE 2 O 3 (RE = Y, and rare earths) as candidate materials. Three types of crystal structures including the preferred cubic phase are known for the rare earth oxides. High quality simple cubic RE 2 O 3 buffer layers were grown epitaxially on {100} textured Ni substrates using both reactive evaporation and sol-gel processing. Detailed X-ray studies have shown that the Y 2 O 3 , Eu 2 O 3 , Gd 2 O 3 , and Yb 2 O 3 were grown with a single epitaxial orientation. SEM micrographs indicated that both e-beam and sol-gel grown films were dense, continuous and crack free. High J c YBCO films were grown on RE 2 O 3 -buffered Ni substrates with sputtered cap layers. Two new alternative buffer layer architectures were developed. A high J c of 1.8 MA/cm 2 at 77 K and self-field was obtained on YBCO films with a layer sequence of YBCO (pulsed laser deposition)/Yb 2 O 3 (sputtered)/Y 2 O 3 (e-beam)/Ni. Also, a high J c of over 1 MA/cm 2 at 77 K and self-field was obtained on YBCO films with a layer sequence of YBCO (ex-situ BaF 2 process)/CeO 2 (sputtered)/YSZ (sputtered)/RE 2 O 3 (sol-gel or e-beam)/Ni. The performance of sol-gel grown buffers approached the quality of e-beam grown buffers.