Structure and orientation of Al$_2$O$_3$ fibers used in YBa$_{2}$Cu$_{3}$O$_{y}$ sputtering

The internal structure and orientation of thin (150–300 $\mu$m) flexible Al$_2$O$_3$ fibers used as substrates for third-generation high-temperature superconducting wires are studied by different methods. It is shown that using scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy, and X-ray diffraction, one can reliably determine the position of the (1$\bar1$02) plane, on which good YBa$_{2}$Cu$_{3}$O$_{y}$ films can be grown.