It was noted that O atoms, interstitially dissolved in the matrix, played an important role in superconductivity since they moves easily in the lattice. They also contributed to hole creation in the CuO2 planes. Here, Bi2Sr2CaCu2O8+y samples containing various amounts of interstitial O were analyzed by means of anelastic spectroscopy. The measurements were performed by using a torsion pendulum operating at a frequency of about 40Hz. Complex relaxation structures were observed and were attributed to the shift of the O interstitial atoms in BiO chains.

Interstitial Oxygen Mobility in Superconducting Samples of Bi2Sr2CaCu2O8+y. J.M.A.Gimenez, C.R.Grandini, D.I.dos Santos: Superconducting Science and Technology, 2006, 19[8], 813-6