Effects of heat treatment and film thickness on microstructure and critical properties of YBCO film processed by TFA-MOD

We fabricated YBCO film on an LAO substrate using the TFA-MOD method and evaluated the effects of the heat treatment temperature and film thickness on the microstructure, degree of texture, and critical properties. The calcining and firing processes were performed in the temperature ranges of 370-460 degrees C and 750-800 degrees C, respectively. We found that the phase purity, grain size and orientation, and degree of texture varied with the calcining and firing temperatures. The films fired at 775 degrees C after calcining at 400-430 degrees C showed the highest critical temperature (T-C-onset) of 89.5 K and critical current (I-C) of 40 A/cm-width, which corresponds to a critical current density (J(C)) of 1.8 MA/cm(2). According to the XRD, pole-figure, SEM images, and Raman analysis, these highest critical properties are probably due to the formation of a purer YBCO phase and stronger biaxial texture. In the multi-coated films, the I-C value increased from 39 to 169 A/cm-width as the number of coatings increased from one to four, while the corresponding J(C) was measured to be in the range of 0.8-1.2 MA/cm(2). Both the I-C and J(C) decreased when a further coating was applied due to the degradation of the microstructure. (c) 2006 Elsevier B.V. All rights reserved.