ELECTROCHEMICAL OXIDATION OF LANTHANUM CUPRATES - SUPERCONDUCTIVITY VERSUS THERMAL-TREATMENT IN LA2CUO4+DELTA

Room-temperature electrochemical oxidation of La2CU04 at the limiting value of 0. 1 5 electrons per formula unit yields bulk superconducting materials with T(c) values that depend on the applied potentials and the drying temperature. Superconducting fractions and structural param eters are also strongly dependent on moderate thermal treatments follo wing the synthesis. We propose a reorganization of the charge carriers with temperature, involving charge transfer between Cu and intercalat ed oxygen atoms, to explain the analytical data obtained for various s amples with different thermal treatments. Other cuprates also show the ability to intercalate oxygen. Thus, electrochemical oxidation of LA2 -xSrxCaCu2O6-delta yields the oxygen stoichiometric phase that, althou gh not superconducting, presents magnetic properties different from it s precursor without a notable change in its structure.