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We report on the in situ preparation of Y Ba2Cu3O7−δ films uniformly deposited over large areas,>20 × 20 cm2, at 690 °C by thermal co-evaporation onto Ni–5 at.% W biaxially textured tapes buffered with e-beam evaporated CeO2. Typically, the thickness of the YBCO and CeO2 layers was 0.9 and 0.1 µm, respectively. Deposition rates were 0.2 and 2.5 nm s−1, respectively. X-ray diffraction θ–2θ Bragg–Brentano and pole figure measurements, and Nomarsky optical and SEM microscopy analysis show good biaxial texture of both layers, sharp interfaces and the absence of cracks. Midpoint critical temperatures, Tc, fall reproducibly in the 87–88 K range with transition widths ΔTc = 1 K. Remarkably high transport critical current densities, Jc, in the 2.0–2.5 MA cm−2 range are achieved at 77 K in 1 cm long samples. The above deposition route appears to be promising for the development of long-length YBCO coated conductors thanks to the relatively low deposition temperature, the high degree of uniformity over large areas and the simple single buffer layer architecture.

Anomalous voltage peaks have been observed below the critical current in dc transport measurements of superconducting YBCO coated conductors for specific contact arrangements. Using a simple concentrated constant-equivalent circuit, it is predicted that current redistributions due to non-homogeneities in the sample may explain the observed effect.

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