Growth of thick chemical solution derived pyrochlore La2Zr2O7 buffer layers for YBa2Cu3O7−x coated conductors

The preparation of several 100 nm thick La2Zr2O7 (LZO) buffer layers on biaxially textured Ni-5 at.%W substrates using chemical solution deposition is studied. This oxide material is currently of great interest for the fabrication of YBa2Cu3O7−x (YBCO) coated conductors. Buffer layers for these coated conductors are required to have thicknesses greater than 100 nm in order to guarantee a sufficient barrier function against metal diffusion from the substrate. In this work, single LZO buffer layers with thicknesses exceeding 200 nm have been prepared. Detailed investigations were carried out in order to study the texture development with increasing thickness as well as the microstructure of these layers. Independent of the thickness, high quality buffer layers showing a distinct biaxial texture up to the surface, smooth surfaces, and a sufficient barrier function against Ni diffusion from the substrate have been reproducibly obtained. The high performance of these chemical solution derived LZO buffer layers was confirmed by a YBCO critical current density Jc of 1.0 MA/cm2 (77 K, 0 T) achieved for a coated conductor sample with a layer sequence YBCO/CeO2/LZO(CSD)/Ni-5 at.%W where CeO2 and YBCO were deposited by pulsed laser deposition.