Twins and twin boundaries in YBCO and In- and Sb-doped YBCO high-Tc ceramic superconductors were observed by means of transmission electron microscopy. The orientation of the twins was determined from the electron diffraction pattern using a voltage of 160kV. Using the conventional extinction method, images of twins could be revealed with better contrast, so that they might be observed more clearly. Based upon the transmission electron microscopic observations, a model for twin formation in the perovskite structure was proposed. The energy for twin boundary formation was estimated to be roughly 44.0mJ/m2.

Twin Formation due to Irradiation of Energetic Electron Beam in High-Temperature Superconductors of In- and Sb-Doped YBCO. G.J.Shen, C.C.Lam, J.C.Chow, S.T.Tang: Physica C, 1993, 214[3-4], 426-34