Ionic transport, a characteristic feature of superionic conductors, is
analyzed microscopically for the RBa(2)Cu(3)O(7-delta) (R=rare earth)
high-temperature superconductors. The electronic correlation effects
are considered to be responsible for the formation of a local double-w
ell potential for apical oxygen, which, in turn, results in a decrease
of the activation energy for interstitial chain oxygen defects.