Preparation of YBa₂Cu₃O_7−x by thermal decomposition of coprecipitated oxalates

Abstract

Yttrium, barium and copper oxalates are coprecipitated quantitatively from metal acetate solutions with oxalic acid in water-acetone mixtures. The particle-size distribution of the precipitate can be controlled by the precipitation conditions. Thermal decomposition of the coprecipitate leads to single-phase YBa₂Cu₃O_7-x. Despite the intermediate formation of BaCO₃, the minimal reaction temperature (770 °C) is clearly lower than that for the solid-state reaction. Results of differential thermal analysis and isothermal thermogravimetry are discussed. The products are characterized by X-ray diffraction and infrared spectroscopy.