Conducting properties and structure of nonstoichiometric orthorhombic phase of YBa2Cu3O7?x obtained by high-temperature vacuum annealing

Neutron and x-ray diffraction studies are carried out which show when the orthorhombic phase of YBa₂Cu₃O_7−x (x≈0.02) is heat treated at temperatures of 430–550 K under tunnel high-vacuum pumping, a partial emission of oxygen from the O(1) positions (with coordinates 0;0;0.1578) and O(4) positions (with coordinates 0;1/2;0) occurs with no change in the symmetry or in the unit cell parameters. The temperature dependence of the electrical resistivity in the temperature interval 77–300 K shows a semiconducting character. Pis’ma Zh. Tekh. Fiz. 24, 90–95 (September 12, 1998)