摘要
It has been confirmed that YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub> superconducting phase is an orthorhombic one belonging to the space group Pmmm with lattice constants a=3. 893A, b=3.820A and c=11.688A. There are many twin domains in this superconducting material studied with a TEM in this work. The reason for the formation of this twin domain structure and the characteristics of phase transformation have also been discussed.
