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Sol-gel synthesis of ferroelectric lithium tantalate ceramics: FTIR investigation of the molecular modification of tantalum ethoxide

Published online by Cambridge University Press:  31 January 2011

Pradeep P. Phulé
Pradeep P. Phulé
Affiliation:
Department of Materials Science and Engineering, 848 Benedum Hall, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
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Abstract

Several sol-gel syntheses make use of “additives” in the sol-preparation step. These additives can react with metal alkoxides causing important structural changes. In order to demonstrate the nature of the reactions involved in the molecular modification process, a model system based on Ta(OC2H5)5, acetic acid and acetylacetone (as modifiers), was studied using FTIR spectroscopy. At room temperature, both modifiers react with the ethoxide to cause formation of new organotantalum precursors. The acetic acid modification was observed from the characteristic symmetric and asymmetric vibrations of the COO groups. The average difference in wave numbers (δv = vasymm – vsymm) between the two of 140 cm−1, observed for different ratios of ac/Ta, signifies a bridging nature of the acetate group. For ac/Ta ≥ 1, formation of ethyl acetate, probably as a result of the reaction between ethanol and excess acetic acid, was also observed using FTIR. Results of the acetylacetone modification showed the enol form of acetylacetone which has its v(C–O) and v(C–C) vibrations centered around 1625 cm−1, split into two bands at 1581 and 1518 cm−1, respectively, indicative of chelation of the acetylacetanate ligand to Ta. In the case of acetylacetone modification, the formation of ethanol was confirmed by FTIR analysis of the liquid fraction distilled at ∼80 °C.

Type
Articles
Information
Journal of Materials Research , Volume 8 , Issue 2 , February 1993 , pp. 334 - 338
Copyright
Copyright © Materials Research Society 1993

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