ELECTROCHEMICAL INTERCALATION OF OXYGEN IN LANTHANUM COPPER-OXIDE AT AMBIENT-TEMPERATURE

The electrochemical intercalation of La2CuO4 at ambient temperature ha s been investigated. Galvanostatic and potential step experiments show that the oxygen atoms intercalated on oxidation are completely remove d on reduction. The voltage composition profiles observed on oxidation and reduction, however, are very different and equilibrium is not att ained. In particular the results obtained on reduction show clear evid ence for a nucleation controlled phase separation. Samples prepared el ectrochemically show superconducting transitions with onset temperatur es of approximately 30 K and approximately 42K depending on the oxygen content, in agreement with previous results. The electrochemical and T(c) data are discussed in relation to the proposed ambient temperatur e phase diagram of La2CuO4+x.