Observation of carboxylic groups in the lattice of sintered Ba2YCu3O7−y high-Tc superconductors

Abstract

This study reports for the first time the experimental evidence that stable carboxylic groups are present in the lattice of sintered ${\mathrm{Ba}}_2\mathrm{Y}{\mathrm{Cu}}_3{\mathrm{O}}_{7-y}$ superconducting oxides. The carboxylic groups likely originated in the incomplete calcination of the BaC${\mathrm{O}}_3$ precursor powder and they could be responsible for the oxygen over-stoichiometry observed in these materials. Further experimental investigations are required concerning in particular the sites of carboxylic groups in the Ba-Y-Cu-O lattice and their effects on the tetragonal-orthorhombic instability.