Synthesis of the defect perovskite series LaCu0₃–δ with copper valence varying from 2+ to 3+

Abstract

MANY important questions about the origin of superconductivity in the high-temperature copper oxide superconductors could be addressed by the study of a copper oxide compound exhibiting a wide range of oxygen stoichiometry while maintaining the basic perovskite structure. A number of compounds are known in which copper occurs formally as Cu³⁺ (refs 1, 2), but most are structurally unrelated to the superconductors, so that a direct comparison of their chemical and physical properties is not appropriate. Here we report the synthesis, structure and preliminary characterization of a new oxygen-deficient perovskite series, LaCuO_3–δ. Although superconductivity has not been observed in this system, its oxygen stoichiometry range, 0.0 < δ < 0.5, is the widest yet found in a copper oxide compound, allowing the formal copper valence to be varied from 2+ to 3+. This series may thus serve as a model system with which to address such questions as the nature of the Cu/O hole states in the superconductors, and the way in which magnetic and transport properties vary with carrier concentration.