Ultrasound effect on the defect formation and Ni diffusion in YBa2Cu3O7-x ceramics

Positron annihilation technique, X-ray structural analysis and radioactive tracers have been used to study ultrasound treatment of YBa2Cu3O7-x ceramics for its effect on the processes of defect formation and Ni diffusion. The ultrasound treatment results in the ordering of anion sublattice of YBa2Cu3O7-x. The oxygen ordering in the basal plane causes redistribution of the electron density over an elementary cell. Electron density redistribution stimulated by ultrasound contributes to the change of the elementary cell parameters. The effects mentioned above lead to the acoustic stimulation of diffusion processes in ceramics, the diffusion coefficient of Ni being increased by a factor of 10 in the temperature range 200 to 4000C. (author)