Roles of humidity and heat treatment temperatures on YBa 2Cu 3O 7− x coated conductors by trifluoroacetic acid-metal organic deposition process

Abstract

YBa 2Cu 3O 7− 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 °C in a 0–12.1% humidified Ar-O 2 atmosphere. The texture was determined by pole-figure analysis. The amount of the BaF 2 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 I C of 40 A/cm-width, which corresponds to J C value of 1.8 MA/cm 2, was obtained for the films fired at 775 (in 12.1% humidity) after calcining at 400–430 °C. It is likely that °C the highest I C value is due to the formation of a more pure YBCO phase, c-axis grains, and a denser microstructure.