The O non-stoichiometry in this material was studied by using thermogravimetry techniques, between 300 and 700C, under O partial pressures ranging from 10-4 to 1atm. It was found that the departure from stoichiometry could be split into 2 parts; one of which reflected a residual O content. The other part depended upon the temperature and O pressure and was related to the formation of O interstitials, whose concentration depended upon the reciprocal of the sixth root of the O partial pressure.

Dependence of Oxygen Stoichiometry and Critical Temperature of Bi2Sr2CaCu2O8 on Oxygen Partial Pressure Between 300 and 700C. F.Jean, J.F.Marucco, G.Collin, M.Andrieux, N.Blanchard: Superconductor Science and Technology, 2000, 13[8], 1167-9