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 ca n 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 (a cac)(2)Ti(OPri)(2) or Ti(OPri)(4) in pyridine. We believe that the key to this reaction is the formation of the stoichiometrically controlle d ''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 hydroxy l protons of the hydrocycarbolic ligands and the alkoxide ligands on t itanium. 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 tita nium 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-r ay diffraction. It was shown that the phenoxyglycolates do not react w ith titanium alkoxide compounds. A comparison of the crystallization b ehaviour of the thermolysis products of the reactions between Pb(O(2)C CR(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 c omparison could be made, the single-source precursors provided evidenc e for more complete conversion to perovskite phase PbTiO3 compared to non-single-source precursors. However, some of the experiments were co mplicated by the different solubilities of the reagents, making interp retation of the results ambiguous.