A novel method for the synthesis of perovskite-type mixed metal oxides by the inverse microemulsion technique

Nanoparticles of lanthanum-nickel, lanthanum-copper and barium-lead oxalates with the metal molar ratios of 11, 21 and 11, respectively, have been successfully synthesized in inverse microemulsions. These metal oxalate particles of about 20 nm diameter were readily calcined into single-phase perovskite-type LaNiO₃, La₂CuO₄ and BaPbO₃. The calcination temperatures for these metal oxalates were generally 100–250°C lower than those for the metal oxalates prepared by the conventional aqueous solution precipitation method. The substantial reduction in the calcination temperatures is attributed to the formation of uniform, near-spherical nanoparticles of the metal oxalate precursors obtained by the unique inverse microemulsion technique.