Effect of Interfacial Resistance on AC Loss as a Function of Applied AC Field in YBCO Filamentary Conductors

While continuous stabilization in filamentary Y-Ba-Cu-O (YBCO) coated conductors can generate additional heating due to coupling loss, a balance between low ac loss and conductor stability can be found through the introduction of interfacial resistance between the stabilizer and the filaments. The impact of interfacial resistance with respect to ac loss as a function of field was studied for YBCO filaments with a continuous silver cap layer. Starting with uncoated YBCO filaments on standard ion beam assisted deposition (IBAD) templates, an interfacial resistance between filaments was introduced through the exposure of filaments to air at room temperature and followed by the deposition of a continuous, 3 mum thick silver cap layer. The interfacial resistance between silver and the YBCO was controlled by oxygen annealing at different temperatures between 200degC and 450degC. Measurements of the ac loss as a function of applied perpendicular field and frequency and the interfacial resistance revealed a correlation between the coupling loss and the oxygen annealing temperature, where the coupling loss was lowest at an oxygen annealing temperature of 200degC.