Transmission electron microscopy studies of a CeO2/Gd2Zr2O7 buffer layer on an Ni-based alloy for YBCO coated conductor

A 0.5 mum thick Gd2Zr2O7 layer was deposited by the ion-beam-assisted deposition (IBAD) method on an Ni-based alloy (Hastelloy), and subsequently a 3 mum thick CeO2, layer was coated by the pulsed-laser deposition (PLD) method. The in-plane alignment (Deltaphi) of the Gd2Zr2O7 layer and the CeO2 layer were 25degrees and 4.9degrees, respectively. TEM cross-sectional and plan-view specimens of the CeO2/Gd2Zr2O7 multilayer were prepared for detailed microstructural characterization. It was observed that the Gd2Zr2O7 layer has a columnar texture perpendicular to the Hastelloy tape surface. The columnar texture was composed of fine grains well aligned in the <001> direction. Therefore the boundaries of columns could not be observed clearly. In the CeO2 layer, the nucleation process of CeO2 grains on the Gd2Zr2O7 surface was strongly affected by both the orientation relationships and the microstructures of the Gd2Zr2O7 layer. As the CeO2 grains grew from the Gd2Zr2O7 surface, the in-plane alignment improved dramatically. The boundaries of CeO2 grains could be observed clearly and were identified as small angle tilt grain boundaries. (C) 2004 Elsevier B.V. All rights reserved.