Influence of Morphology and Texture of CeO 2 on YBa 2 Cu 3 O 7 (YBCO) Growth and BaCeO 3 Formation in Solution‐Derived Synthesis

When working with chemical solution deposition techniques, one of the main issues for optimal performance of CeO 2 buffer layers in coated conductors is the insufficient chemical stability of the CeO 2 layer during YBa 2 Cu 3 O 7 (YBCO) thermal processing. This work focusses on the morphology and nanostructure in thin CeO 2 films prepared by means of a novel aqueous synthesis route and incorporated into a Ni–W/La 2 Zr 2 O 7 /CeO 2 /YBa 2 Cu 3 O 7 ‐coated conductor. Optimization of precursor chemistry and thermal processing led to a reduction in barium cerate formation. In a new precursor design, iminodiacetic acid was used as a stabilizing ligand, which resulted in an improved morphology of the buffer layer. A shelf life of more than 6 months was established by using a metal‐to‐ligand ratio of 1 to 5. During thermal processing, a combination of a slow calcination ramp with a high sintering ramp, short sintering dwell time and a low oxygen partial pressure during the synthesis resulted in a root mean square roughness below 3 nm for AFM analysis, a [111] to [002] ratio of 1 to 90 in X‐ray diffraction and well‐defined patterns in reflection high‐energy electron diffraction (RHEED) analysis of the CeO 2 surface. Trifluoroacetate‐YBCO was deposited on top of the CeO 2 buffer layer. Cross‐section analysis with a focussed ion beam allowed us to correlate the morphology and nanostructure of the CeO 2 buffer layer with the formation of BaCeO 3 and the appearance of voids and secondary phases throughout the YBa 2 Cu 3 O 7 layer.