Influence of Oxygen Partial Pressure on the Synthesis of Ba2YCu3O7 from a Novel Oxalate Precursor

An oxalate precursor precipitate is prepared by reacting carbonate, hydroxide, and/or oxides with oxalic acid in a heated aqueous solution. By this approach, there are no extraneous anions or cations introduced by the starting salts or created during the reaction since the products are only water and carbon dioxide. Specific solubility differences may be compensated by recycling the filtrate. The thermal conversion of the resulting coarse crystalline precipitate to the desired oxide product is studied by thermoanalytical techniques and X-ray diffraction. The oxygen content and, hence, the defect structure of the product depend upon the partial pressure of oxygen and the temperature. Consequently, the kinetics of the final stage of the reaction, eq 1, are influenced by the value of x.