Thermomechanical single domain formation of YBa2Cu3O7-x superconducting crystals at decreased oxygen pressure

Peculiarities of the thermomechanical untwinning processes (single domain formation) in YBa2Cu3O7-x single crystals and the influence of such factors as the state of the initial domain structure, the oxygen content (the composition of the gas environment) and temperature, have been investigated. A new procedure of the single domain formation is suggested, which ensures the transformer of a rhombic crystal into the tetragonal one at 560-600 deg C in the reducing atmosphere (argon). After that uniaxial pressure along [010] is applied to the crystal and the oxidizing environment is created (oxygen flow), transforming the crystal back into the rhombic form but without twinning. 10 refs., 2 figs