Effect of post-annealing in low oxidizing atmosphere on the properties of CeO2 buffer layer for coated conductors

CeO2-x thin films have been fabricated by chemical solution deposition (CSD) technique on bi-axial textured Ni5W substrates. The effect of post-annealing in moderate oxidizing atmosphere on the structure and texture of the film has been studied by varying temperature and CO2 concentration during the post-annealing process. The results show that the structure and texture stability of the CeO2-x film is heavily dependent on the post-annealing temperature. A high post-annealing temperature could lead to the change of cerium valence and even oxidation of Ni5W substrate. In addition, an excess amount of CO2 could cause the degeneration of texture degree and surface flatness of CeO2-x film because of the increase of oxygen vacancy defects and the production of carbonates. Except effective removal of residual carbon in films, therefore, the production of both the oxygen vacancy concentration and carbonates should be greatly controlled to improve the texture degree and surface flatness of CeO2-x films by adjusting the concentration of oxidizing gas and the heat-treatment temperature during the post-annealing process or the YBCO deposition process. Moreover, the CeO2-x film post-annealed at 700 °C in the mixture atmosphere with 1% CO2 show sharper texture and smoother surface because of the existence of small amount of oxygen vacancy and carbonates compared with the as-prepared sample.