On the La₂CuO₄-Nd₂CuO₄ system: Influence of oxygen pressure on the phase diagram, oxygen stoichiometry and transport properties of the T/O and T′ type solid solutions

Abstract

Two types of solid solutions exist in the La₂CuO₄-Nd₂CuO₄ system, with respectively the T/O and T′ type structure of La₂CuO₄ and Nd₂CuO₄. When synthesized in air at high temperature and normal pressure, both solid solutions exhibit semi-conducting properties. A treatment under oxygen pressure causes a slight change in the unit cell parameters of the T/O type solid solution, a significant shift of its upper limit towards higher neodynium contents and a small increase of the average oxidation state of copper. All these modifications result from the insertion of some oxygen species in the T/O type-structure and induce a superconducting behaviour.

Key Words:

• Oxygen pressure
• copper oxides
• superconductivity