Physical properties of non-stoichiometric oxides

An important example of oxide materials exhibiting oxygen non-stoichiometry are the high temperature superconductors (HTSC). In this family of materials the variation of the oxygen content modifies the defect structure and the carrier concentration, causing phase transitions and structural distortions with the consequent change in their physical properties. In some systems, a continuous variation of the physical properties as a function of the oxygen content is observed, while in others, small changes of the oxygen content strongly modify the superconducting behavior of these materials. In this paper, we review an analysis of the influence of the oxygen content on the physical properties of three HTSC materials: the electron doped Nd–Ce–Cu–O superconductor, the R–Ba–Cu–O (R=Nd, Gd, Pr) 123 compounds and the (Hg, Re)-1201 material.