AbstractThe evolution from a partially oriented granular microstructure to a dense epitaxial one in CeO₂ buffer layers deposited by metallorganic decomposition (MOD) on single crystal Y-stabilised ZrO₂ (YSZ) substrates, has been investigated. CeO₂ buffer layers were investigated using X-ray diffraction (XRD), atomic force microscopy (AFM), reflection high energy electron diffraction (RHEED), transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). Reducing atmospheric conditions inhibit grain growth resulting in a nanometric granular microstructure with a high concentration of C impurities decorating grain boundaries and porosity. Oxidation and elimination of C species promotes grain growth resulting in a dense epitaxial film, as well as stabilizes otherwise energetically prohibitive polar (001) planes. Trifluoracetate (TFA) derived MOD YBa₂Cu₃O₇ (YBCO) films deposited on optimized CeO₂ buffers exhibit a sharp interface while the undesired reaction giving BaCeO₃ is minimized. J_c values of 1.5 MA/cm₂ and 14 MA/cm₂ at 77K and 5K, respectively, are achieved.