Oxygen Deficient YBa2Cu3O7-δ: Two Superconducting Phases

A set of ox y gen deÙcient pow der and gran ular samples of Y Ba 2 C u3 O7 À £ ceramics w as studied by means of thermogra vi metric and magneticall y mo dulated microw ave absorption metho ds.Esp eciall y the last metho d has turned out to be a powerf ul metho d, w hich w as used to determine the dependence of critical temp erature T c on the oxygen parameter £ .U sing these metho ds it has been show n that the remo ving of oxygen evo kes the inhomogeneou s oxygen distributi on in the samples and a change in carrier concentration till to the loss of sup erconducti ng prop erties.A sup erconducti ng phase w ith T c = 60 K , w hich occurs in oxygen deÙcient Y Ba 2 Cu3 O 7À £ sample, is an unstable phase.