Structure Evolution in the PbO-ZrO2-TiO2 Sol-Gel System: Part I - Characterization of Prehydrolyzed Precursors

In this investigation, several spectroscopic and analytical techniques were used to determine the chemical compositions and structures of the lead, zirconium, titanium, and Pb-(Zr, Ti) alkoxides involved in the sol-gel synthesis of PZT thin films. These techniques included H-1, C-13, and Pb-207 NMR; FT-IR; gas chromatography; Karl Fischer titration; and number-average molecular weights (M-n) determined by cryoscopy. It was found that the titanium precursor had a M-n of 548 and a formula of [Ti(OCH2CH2OCH3)(4)](1.6); the zirconium precursor had a M-n 1015 and a formula of [Zr(OCH2CH2OCH3)(4)](2.6); and the lead precursor had a formula Pb-6(OOCCH3)(5)(OCH2CH2OCH3)(7)center dot 4 H2O and a molecular weight of 2131 (M-n = 2113). It was observed that residual water from the incomplete dehydration of lead acetate trihydrate coupled with released water due to the esterification of acetic acid caused M-O-M (M = Pb, Zr, Ti) bonds in the Pb-(Zr,Ti) alkoxide. Two possible isomeric structures of the Pb-(Zr, Ti) alkoxide have been proposed. They are both cyclic and have a formula of Pb2M'M '' O-2(OR)(8)(ROH)(2), (M'M '' = Zr and/or Ti) and a molecular weight of 1336 (M-n = 1386).