The visualization of current-limiting defects inYBa2Cu3O7 films on ion-beam assisted deposition buffer layers of yttrium-stabilizedZrO2 and Gd2Zr2O7

Abstract

For the production of high-current-carrying, long-length superconducting wires or tapes, itis necessary to use biaxially textured metallic substrates or buffer layers. Thoughbeing highly textured, the deposited superconducting film exhibits a complexdefect structure which (locally) suppresses the critical current and alternatescharacteristically the magnetic flux distribution seen in magneto-optical imaging.In this paper, we report on pulsed laser deposited YBaCuO films on biaxially textured yttrium-stabilizedZrO2 (YSZ)and Gd2Zr2O7 (GZO) buffers which were grown by ion beam assisted deposition (IBAD) on polycrystallinesubstrates. The current-limiting defect structure turns out to resemble closely acombination of a dense distribution of pinhole-like induced growth distortions and a finegrain boundary network. The current suppression is caused on the one hand by the densepacking of pinhole-like defects. On the other hand, we observe a substantial currentanisotropy being related to the surface morphology of the buffer layers and the direction ofthe IBAD-beam.