Valence state of cobalt atoms and crystal structure of YBa2Cu3-xCoxO6+delta solid solution

The crystal structure of YBa2Cu3-xCoxO6+delta solid solutions, where x = 0. 2, 0.4, 0.6, and 0.8, was studied by powder neutron diffraction. The charge d states of the cations were calculated using the interatomic distances obt ained in neutron diffraction measurements. It is shown that cobalt ill the Cu1 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 cha nges to 4+, the environment changes to tetrahedral, and copper in the Cu2 p osition is partly substituted. Cobalt in the Cu2 positions has valence 2+ a nd does not change the square pyramidal arrangement of oxygen ions surround ing this position.