Microstructural homogeneity and electromagnetic connectivity of YBa2Cu3O7-delta grown on rolling-assisted biaxially textured coated conductor substrates

摘要

The electromagnetic connectivity and microstructure of three YBa2Cu3O7-delta (YBCO) films grown on biaxially textured substrates were investigated by magneto optic (MO) imaging and scanning electron microscopy (SEM). The films were deposited by pulsed laser deposition (PLD) on yttria-stabilized zirconia (YSZ) and CeO2-buffered, biaxially textured Ni tapes. The transport critical current density (J(c)) values of the films were 0.3, 0.6 and 0.7 MA/cm(2) (77 K, 0 T). MO imaging revealed clearly granular electromagnetic behavior in the lowest J(c) and one of the higher J(c) samples, but considerably better connectivity in the sample with a J(c) value of 0.6 MA/cm(2). High resolution SEM showed a dense and rather featureless microstructure in the YBCO of the most highly electromagnetically connected sample, whereas pores and/or second phase particles cluttered the YBCO layers of the granular samples. Thus, the granular behavior in these samples appears to be caused by pores and second phase particles that locally obstruct the superconducting current in the YBCO layer. Control of these types of defects clearly is important for raising the J(c) value. (C) 2000 Elsevier Science B.V. All rights reserved. [References: 20]