EBSD Characterization of Specific Microstructures in RE-BCO Superconductors

Using the electron backscatter diffraction (EBSD) technique, we analyze in this contribution the microstructure of YBa₂Cu₃O_x (YBCO) thick films with embedded a-axis oriented grains. The YBCO films were prepared by liquid phase epitaxy in air using NdGaO₃ substrates. Using this technique, a/c-grain boundaries (GBs) with a well-defined facet of the YBCO film characterized by a single crystalline nature are obtained. This type of GB is very important for the basic physics of GBs in high-T_c superconductor materials, and will contribute to a better understanding of GBs also in bulk materials. The application of EBSD to the analysis of a/c-GBs in YBCO requires a high Kikuchi pattern quality (i.e., image quality) to enable a proper distinction of the orientation, as the a-axis corresponds to about one-third of the c-axis, which can cause a misinterpretation of the resulting data. Having solved this problem, the EBSD-based determination of the GB misorientation angles directly proof the specific grain orientation achieved in the film growth.