Roles of humidity and heat treatment temperatures on YBa2Cu3O7−x coated conductors by trifluoroacetic acid-metal organic deposition process
(School of Advanced Materials Science and Engineering, Sungkyunkwan University, Jangan, Suwon,
Gyeonggi, 440-746, Korea)
Gyeonggi, 440-746, Korea)
Abstract: YBa2Cu3O7−x(YBCO) films were fabricated on an LAO substrate using the trifluoroacetic acid-metal organic deposition (TFA-MOD) method and the effects of the humidity and heat treatment temperatures on the microstructure, degree of texture and critical properties of the films were evaluated. In order to understand the combined effects of the humidity and the calcining and firing temperatures on critical properties, heat-treatment was performed at various temperatures with the other processing variables fixed. The films were calcined at 400−430 ℃ and fired at 750−800 ℃ in a 0−12.1% humidified Ar-O2 atmosphere. The texture was determined by pole-figure analysis. The amount of the BaF2 phase was effectively reduced and a sharp and strong biaxial texture was formed under a humidified atmosphere, which led to increased critical properties. In addition, the microstructure varied significantly with firing temperature but changed little with calcining temperature. The highest IC of 40 A/cm-width, which corresponds to JC value of 1.8 MA/cm2, was obtained for the films fired at 775 ℃ (in 12.1% humidity) after calcining at 400−430 ℃. It is likely that the highest IC value is due to the formation of a more pure YBCO phase, c-axis grains, and a denser microstructure.
Key words: humidity; metal organic deposition; pole-figure; trifluoroacetates; YBa2Cu3O7−x coated conductor