Insertion of water into rare earth oxocuprates (Ln)Ba2Cu3O7-delta

The solid state reaction of LnBa(2)Cu(3)O(7-delta) bulk material with water vapour corresponds to a quantitative topotactic reaction of the solid with H2O to a maximum stoichiometry of LnBa(2)Cu(3)O(7-delta)(H2O)(1). The reaction proceeds in a temperature window which depends upon the oxygen content (delta) of the starting phase and is correlated with a structural transition via intermediate states. Although the integral copper oxidation state is not affected by the water intercalation, electronic and transport properties are strongly influenced. The insertion of water into these defect perovskites has to be described as a topotactic acid/base process.