SYNTHESIS OF FINE-PARTICLE TITANATES BY THE PYROLYSIS OF OXALATE PRECURSORS

Fine-particle MTiO3, Where M = Ca, Sr, Ba or Pb, were prepared by the pyrolysis of MTiO(C2O4)2 . 4H2O in the presence of a redox mixture containing NH4NO3 and oxalic acid dihydrazide at 350-degrees-C. The redox mixture, having a low ignition temperature, not only pyrolyses the oxalate precursor but also produces large quantities of gases, which results in a fine, foamy oxide product. The exothermicity of the redox reaction provides the heat required for the decomposition of the oxalate, and the gases evolved create the foamy nature of the product and help to dissipate the heat, which inhibits the sintering of MTiO3. Metal titanate powders obtained by the pyrolysis of the oxalates are of submicrometre size and have a high surface area (18-42 m2g-1). The sintered BaTiO3 and PbTiO3 showed spontaneous polarization of 12 and 26 muC cm-2, respectively, for a field strength of 120 kV cm-1.