YBCO coated conductors prepared by chemical solution deposition: A TEM study

Abstract

Recently large attention has been devoted to chemical solution deposition (CSD) as a promising method for fabricating low-cost YBCO coated conductors. We present an extensive transmission electron microscopy (TEM) cross-section analysis of CSD grown La 2Zr 2O 7 (LZO) buffer layers on flexible Ni–5at%W substrates. The high performance of these chemical solution derived buffer layers was confirmed by a YBCO critical current density J c of 0.84 MA/cm 2 achieved for a coated conductor sample with a layer sequence Ni–5at%W/LZO (CSD)/CeO 2 (CSD)/YBCO, where the YBCO film was deposited by pulsed laser deposition (PLD). TEM sample preparation was carried out by conventional mechanical polishing and ion milling techniques. TEM bright-field images of the LZO films and nickel substrates were acquired under two-beam conditions. The layer thicknesses and nanovoid size were determined for the LZO buffer layers. Moreover, the interfaces between the different layers were investigated and identified. Electron diffraction patterns were obtained in order to determine the microscopic texture of the samples. Despite the presence of nanovoids in the LZO buffer layers, they act as efficient Ni diffusion barriers.