Control of oxygen stoichiometry in Nd2CuO4-x via solid state electrochemical techniques

Recently, Tokura et al., have discovered an n-type superconductor, Nd2-xCexCuO4-y. This phase is structurally interesting since the copper atoms are coordinated by four oxygen atoms in a square planar configuration without any apical oxygen atoms above or below the CuO2 plane. On doping Ce into Nd2CuO4 a reduction in the electronic resistance is observed. However, superconductivity is not observed unless the material has been made oxygen deficient, by annealing in a reducing atmosphere. A decrease in resistivity was also observed in undoped Nd2CuO4-x on quenching from 1423 K in air down to room temperature, which produced an oxygen deficiency of y≅0.04. In order to ascertain the nature and role of these oxygen vacancies, we have begun a programme of work to investigate the electrochemical control of oxygen stoichiometry and superconductivity in Nd2CuO4-x. The work outlined here concerns the direct reduction of undoped bulk polycrystalline Nd2CuO4 material by solid-state electrochemical techniques using the oxide ion conductor yttria stabilized zirconia 10Y2O3.90ZrO2 (YSZ). (orig.)