Fabrication of IBAD-MgO and PLD-CeO₂ Layers for YBCO Coated Conductors

MgO thin films with different textures are fabricated by the ion beam assisted (IBAD) method on the Y₂O₃/Al₂O₃ buffered C276 tape. Then a CeO₂ layer is directly grown on the IBAD-MgO film by the pulsed laser deposition (PLD) method. Effects of IBAD-MgO texture, substrate temperature and thickness on the grain alignment of the CeO₂ layer are investigated. Film characterization is performed by x-ray diffraction and atomic force microscopy. It is found that the orientation and texture degree of the CeO₂ layer are very sensitive to the IBAD-MgO texture. By optimizing the IBAD-MgO texture, CeO₂ has pure (002) orientation and excellent biaxial texture deposited in a broad substrate temperature range. In addition, the PLD-CeO₂ layer has a thickness effect. Under the optimized experimental condition, the PLD-CeO₂ layer has a high in-plane texture of Δφ=2.9° and a smooth surface with an rms surface roughness of less than 2 nm. The critical current density J_c of a 0.4-μm-thick YBCO film deposited on the CeO₂ layer is 6.25×10⁶ A/cm² at 77 K and a self-field.