Crystallography of phase transition of YBa2Cu3O7−δ

Abstract
A space‐group theoretical approach has been applied to the high Tc superconducting oxide YBa2Cu3O7−δ (δ∼0.3) to explain the occurrence of coherent domain boundaries. This method quantitatively accounts for the transmission electron microscopy (TEM) observations of {110} twin boundaries in the room‐temperature orthorhombic phase. The possible nature of the relaxation of these twin boundaries and the atomic arrangement at these boundaries are briefly discussed.