Valence state of cobalt atoms and crystal structure of YBa2Cu3−x-CoxO6+δ solid solution

The crystal structure of YBa2Cu3−xCoxO6+δ solid solutions, where x = 0.2, 0.4, 0.6, and 0.8, was studied by powder neutron diffraction. The charged states of the cations were calculated using the interatomic distances obtained in neutron diffraction measurements. It is shown that cobalt in the Cul position has valence 3+ and octahedral environment for x = 0.2 and 0.4. As x increases, the valence of some cobalt ions in the above positions changes to 4+, the environment changes to tetrahedral, and copper in the Cu2 position is partly substituted. Cobalt in the Cu2 positions has valence 2+ and does not change the square pyramidal arrangement of oxygen ions surrounding this position.