Nmr Spectroscopic Investigations of Pbtio 3 Sol-Gel Processing
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NMR SPECTROSCOPIC INVESTIGATIONS OF PbTiOa SOL-GEL PROCESSING* S.D. RAMAMURTHI' AND D.A. PAYNE" 505 King Ave., Columbus, OH 43201 of Material Science and Engineering, University of Illinois at Urbana-Champaign, 105 S. Goodwin Ave., Urbana, IL 61801.
""Department Battelle, ABSTRACT
Lead titanate gels were prepared by sol-gel processing from lead1 acetate and titanium isopropoxide in methoxyethanol. In the present study, H, and 3 1 C FTNMR spectroscopic and mass spectrometric techniques were used to identify the structures of lead and titanium precursors formed by refluxing lead acetate and titanium isopropoxide in methoxyethanol, respectively. Lead acetate was found to be partially alkoxylated, whereas, the titanium precursor was identified as a dimer with complete alkoxy group exchange. Similar procedures were applied to identify the lead titanium complex formed from lead and titanium precursors. INTRODUCTION Interest in the properties of ferroelectric materials has lead to the development of new chemical routes for the preparation of materials in a variety of forms, including, monoliths, films, fibers, and powders'. One of these chemical.methods is sol-gel processing, which normally involves hydrolysis and condensation of metal alkoxides in an alcoholic media. As polymerization proceeds, the viscosity of the solution increases and the solution eventually gels. The sol-gel process generally offers advantages over conventional methods of ceramic processing by providing homogeneity, purity, stoichiometric control, and low temperature processing2. Lead titanate in particular has been synthesized from lead acetate and titanium isopropoxide in methoxyethanollb,3. The procedure used can be summarized by the following equations: Pb(OOCHS) 2 .3H 20 + CH3OCH 2CH20H .ewh;; -•i _> X (Lead Precursor) Dehydrate
Ti(OiPr) 4 + CH 3OCH 2CH 2OH
Ref ux
Distill
> Y (Titanium precursor)
CH 3 OCH 2 CH 2 0H
X + Y ------------------- > Z (Lead titanium Precursor) Reflux, Distill
Z + xH20 '
CH3 OCH 2CH 2 0H
-------------.--
> PbTiO 3
(1)
(2)
(3)
(4)
This research was carried out at the University of Illinois at UrbanaChampaign, IL. Mat. Res. Soc. Symp. Proc. Vol. 180. ©1990 Materials Research Society
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Limited studies using FTIR and Raman spectroscopic techniques 4 have attempted to identify lead titanate precursors (X, Y, and Z) and hydrolysis/condensation products in situ. These studies have provided only a limited understanding of the system due to the presence of overlapping and unresolved peaks in the spectra. Other studies3, 5 have primarily studied the by-products of reactions 1 through 4. In the present study, however, the X, Y, and Z precursors were isolated and characterized by FTNMR and mass spectrometric methods'.
EXPERIMENTAL PROCEDURE Lead and titanium precursor solutions were prepared by methods originally reported by Budd et al.lb. Lead (X), titanium (Y), and lead titanium precursor (Z) precursors were isolated by removing the volatiles under reduced pressure at 1 torr from their 1 molar solutions in m
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