SUPERCONDUCTIVITY IN THE LA2CUO4-ND2CUO4 SYSTEM AFTER TREATMENT UNDEROXIDIZING CONDITIONS

Two kinds of solid solutions exist in the La2CuO4-Nd2CuO4 system with, respectively, the T/O and T' type structures characteristics of La2Cu O4 and Nd2CuO4. When synthesized at atmospheric pressure in air, i.e., under P approximate to 20 kPa oxygen pressure, both solid solutions e xhibit semiconducting properties. A treatment under oxidizing conditio ns either under oxygen pressure or anodic polarization of La2-xNdxCuO4 compounds causes the insertion of some oxygen species into the T/O st ructure and the formation of a mixed valence Cu(III)/Cu(II). The resis tivity of the corresponding compounds is drastically decreased, and a bulk superconducting behavior is induced at low temperature in the com positional range 0 less than or equal to x less than or equal to 0.60. For a fixed concentration of excess oxygen, the critical temperature decreases with increasing amount of neodymium. (C) 1995 Academic Press , Inc.