An Infrared Study of Metal Isopropoxide Precursors for SrTiO 3

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AN INFRARED STUDY OF METAL ISOPROPOXIDE PRECURSORS FOR SrTi0 3 * R. E. Riman**, D. M. Haaland and C.J.M. and A. Bleier***

Northrup,

Jr.t,

***Massachusetts Institute of Technology, Cambridge, Oak Ridge National Laboratories **Massachusetts Institute of Technology, Cambridge, tSandia National Laboratories, Albuquerque, NM

and H. K. Bowen**

MA; Presently at MA

ABSTRACT A Sr/Ti bimetallic isopropoxide complex was synthesized by The complex served as a precursor to the production two methods. Infrared of homogeneous SrTiO3 powders via alkoxide hydrolysis. spectra were obtained for Sr(OPri) 2 , Ti(OPri) 4 , and the product of In addition, the IR spectra of the solutions of the syntheses. each of the alkoxides were followed as hydrolysis reactions proceeded. Detailed analysis of the spectral features support the The new Sr/Ti existence of a 1:1 Sr/Ti bimetallic alkoxide. compound exhibits characteristic absorption bands at (1017, 993, 972, 961 cm-l), (844, 838, 827 cm-I) and (620, 596, and 572 cm-). A band at 819 cm-I might also be associated with the new Sr/Ti bimetallic alkoxide. The infrared spectra suggest that the isopropoxide ligands in the bimetallic alkoxide are in at least three This information offers insight into separate local environments. possible structures for the complex.

INTRODUCTION Uniform and densely packed SrTiO3 powder with a narrow size distribution of equiaxed, pure, homogeneous and unagglomerated particles may produce optimized SrTiO3 microstructures at a reduced processing temperature [1]. This goal has been achieved in the production of TiO2 compacts We believe by packing and sintering alkoxide based TiO2 powder [2]. that SrTiO3 powder can be synthesized using the general synthesis route pioneered by Mazdiyasni, et al. with the formation of BaTiO3 [3,4]. In this paper we describe several methods of double alkoxide synthesis and present infrared spectral evidence for the formation of a Sr/Ti bimetallic complex which hydrolyzes to form homogeneous SrTiO3 [l,3]. In addition, the feasibility of monitoring the complex under different solution environments and studying hydrolysis reactions is examined.

BACKGROUND to describe titanate formation from Smith, et al.[3] were the first a double alkoxide precursor using 1:1 solutions of Sr(OPri) 2 and titanium t Infrared characterization of Sr(OPr') 2 , tertiary amyloxide, Ti(OAm ) 4 [3]. t Ti(OAm ) 4 and the mixture of the two alkoxides suggested that the mixture

*A portion of this work was performed at Sandia National Laboratories supported by the U.S. Department of Energy under contract number DE-ACO4-76DP00789. The M.I.T. work is supported by an industry consortium. Mat. Res. Soc. Symp. Proc. Vol. 32 (1984)

Published by Elsevier Science Publishing Co.,

Inc.

234

possessed unique spectral features which arise from the bimetallic alkoxide. Bimetallic complexation appears to describe the assemblage of hydrolysis products obtained by Suwa, et al. [6] when different ratios of Turevskaya, Ba(OPri)i:Ti(OPri) 4 were prepared in isopropanol solution