The role of precursor segregation in the formation of perovskite phase PbTiO3 from lead(II) glycolate and phenoxyglycolate compounds

It has been shown previously that perovskite phase PbTiO3 materials can be formed at low temperatures (300-400 degrees C) by thermolysis of the product of the reaction between Pb(O(2)CCMe(2)OH)(2) and either (acac)(2)Ti(OPri)(2) or Ti(OPri)(4) in pyridine. We believe that the key to this reaction is the formation of the stoichiometrically controlled ''single-source'' intermediate, Pb(O(2)CCMe(2)O)(2)Ti(acac)(2) or Pb(O(2)CCMe(2)O)(2)Ti(OR)(2), by elimination of alcohol from the hydroxyl protons of the hydrocycarbolic ligands and the alkoxide ligands on titanium. To test this hypothesis, lead phenoxyacetate, Pb(O2C CH(2)OPh)(2), and lead phenoxyisobutyrate were synthesized, where the hydroxyl protons were replaced by a phenyl group to prevent reaction with titanium alkoxide ligands. The new compounds Pb(O(2)CCR(2)OPh)(2), where R = H or Me were characterized in the solid state by single-crystal X-ray diffraction. It was shown that the phenoxyglycolates do not react with titanium alkoxide compounds. A comparison of the crystallization behaviour of the thermolysis products of the reactions between Pb(O(2)CCR(2)OX)(2), where R = H or Me and X = H or Ph, and either (acac)(2)Ti(OPri)(2) or Ti(Opr(i))(4) in pyridine was conducted. Where a direct comparison could be made, the single-source precursors provided evidence for more complete conversion to perovskite phase PbTiO3 compared to non-single-source precursors. However, some of the experiments were complicated by the different solubilities of the reagents, making interpretation of the results ambiguous.