TRANSMISSION ELECTRON MICROSCOPY STUDY OF TWIN DOMAIN STRUCTURES IN YBa2Cu3O7−x SUPERCONDUCTOR
The study of the twin domain structure of YBa2Cu3O7−x superconductor synthesized by coprecipitation method has been carried out by using the transmission electron microscopy. It was found that the twin domain boundary was parallel to the (110) lattice planes. The twin domain is designated as a 90° one. The same twin structure exhibited different characteristics of spot splitting in its selected area eletron diffraction patterns (SADP) when it was irradiated in different incidence directions. The experimental results were satisfactorily consistent with the theoretical calculation. The mechanism of the formation of 90° twin domain has also been discussed. The phase transformation from tetragonal to orthorhombic taking place in YBa2Cu3O7−x ceramics during cooling is considered to be of the “Martensite”.