Effect of Oxygen Content in Atmospheres of Heat Treatment on the Properties of YBCO Thin films

YBa2Cu3O7-x (YBCO) films were prepared on single-crystal LaAlO3 (100) substrate using a low-fluorine sol-gel method. The effect of the oxygen content in the atmospheres of heat treatment at 725 °C on the critical current density (Jc) of the obtained YBCO films was investigated. Results show that all the films heat-treated in the oxygen content range of 100∼1700 µL/L exhibit good biaxial-texture characteristics. However, high-Jc YBCO films are not obtained at the oxygen contents of 100 and 200 µL/L due to the lower density of the surfaces. With increasing the oxygen content, the film surface becomes dense gradually. When the oxygen content is 300 µL/L, the surface of the film is very dense and Jc reaches 4.3 MA/cm2. Furthermore, many copper-rich second phases grow up on the surfaces with further increasing oxygen content up to 800 and 1700 µL/L, which is a dominant reason for the decline in Jc of the films.