Mobility and ordering of the oxygen ions in semiconducting and insulating YBa2Cu3O6+x

Elastic energy loss experiments were made in order to investigate the O mobility and reordering in the CuOx planes of YBa2Cu3O6+x at the lowest values of x. The height of a dissipation peak with an activation energy of 0.11 eV, attributed to jumps of isolated oxygens, has been shown to decrease both after severe degassing treatments in vacuum and after several months of room temperature ageing. The apparent inconsistency between the high mobility of free O and the slow reordering kinetics is discussed. The repulsive Coulomb interaction between the isolated O ions is proposed to have a major influence on their aggregation probability, and consequently on the fraction of free O at equilibrium and on the time necessary for reaching it.