Earticle

CeO2 has been widely used for single buffer layer of coated conductor because of superior chemical and structural compatibility with ReBa2Cu3O7-δ(Re=Y, Nd, Sm, Gd, Dy, Ho, etc.). But, the surface of CeO2 layer showed cracks because of the large difference in thermal expansion coefficient between metal substrate and deposited CeO2 layer, when thickness of CeO2 layer exceeds 100 nm on the biaxially textured Ni-3%W substrate. The deposition rate has been limited to be less than 6 Å/sec in order to get a good epitaxy. In this research, we deposited CeO2 single buffer layers on biaxially textured Ni-3%W substrate with 2-step process such as thin nucleation layer(>10 nm) with low deposition rate(3 Å/sec) and thick homo epitaxial layer(>240 nm) with high deposition rate(30 Å/sec). Effect of deposition temperature on degree of texture development was tested. Thick homo epitaxial CeO2 layer with good texture without crack was obtained at 600 oC, which has Δφ value of 6.2 o, Δω value of 4.3 o and average surface roughness(Ra) of 7.2 nm within 10 ㎛ × 10 ㎛ area. This result shows the possibility of preparing advanced Ni substrate with simplified architecture of single CeO2 layer for low cost coated conductor.

Simplification of the buffer architecture in the fabrication of coated conductors is required because the deposition of multi-layers leads to a longer production time and a higher cost of coated conductors. In this study, a single layered buffer deposition of CeO2 for low cost coated conductors has been tried using thennal evaporation technique. 100nm-thick CeO2 layers deposited by thermal evaporation were found to act as a diffusion layer. 0.4㎛-thick SmBCO superconducting layers were deposited by thermal co-evaporation on the CeO2 buffered Ni-W substrate. Critical current of 55.4 A/cm2 was obtained for the SmBCO coated conductors.