Abstract
The purpose of this paper is to present the reaction of a cuprate La1.8Pr0.2CuO4 with CaH2 which yields La1.8Pr0.2CuO3.5, a new oxygen-vacancy-ordered arrangement of cooperatively-distorted Cu2O3 planes containing 4-coordinate Cu+ sites. This new compound has been characterized by X-ray diffraction, electron paramagnetic resonance (EPR) and DSC.The X-ray powder diffraction data have revealed that this cuprate is crystallized with the so-called “pseudo-S” type structure, showing a monoclinic symmetry and space group A2/m. Concerning the EPR measurements, they have shown the presence of Cu2+ cation and a hyperfine structure suggesting a pronounced hybridization of the copper–oxygen bond. Finally, X-ray diffraction has demonstrated that the obtained La1.8Pr0.2CuO3.5, heated in oxygen at 420 °C, turns topotactically into La1.8Pr0.2CuO4 with a T′-type structure (I4/mmm).