Superconductivity in the La2CuO4-Nd2CuO4 system after treatment under oxidizing conditions

Two kinds of solid solutions exist in the La2CuO4-Nd2CuO4 system with, respectively, the T/O and T' type structures characteristics of La2CuO4 and Nd2CuO4. When synthesized at atmospheric pressure air, i.e., under P ∼ 20 kPa oxygen pressure, both solid solutions exhibit semiconducting properties. A treatment under oxidizing conditions either under oxygen pressure or anodic polarization of La2-xNdxCuO4 compounds causes the insertion of some oxygen species into the T/O structure and the formation of a mixed valence Cu(III)/Cu(II). The resistivity of the corresponding compounds is drastically decreased, and a bulk superconducting behavior is induced at low temperature in the compositional range 0 ≤ x ≤ 0.60. For a fixed concentration of excess oxygen, the critical temperature decreases with increasing amount of neodymium