Structure peculiarities of YBa2Cu3O7-y

By means of grain abnormal growth during isothermal recrystallization of ceramic monocrystals YBa2Cu3O7-y with transverse size up to 2 mm and up to 0.5 mm thick are produced. Homogeneous deformation S does not describe actual atomic displacements; provided tetragonal lattice was deformed only in this way, atoms would not be in finite positions corresponding to rhombic lattice. It is shown that macroscopic non-distorted surface of interface can exist, since rhombic phase formed is actually heterogeneous and consists of lamellas, which are twinned as to each other and provide four orientation states. In total reciprocal lattice the symmetry of initial tetragonal phase is preserved. 5 refs.; 3 figs