Formation, Structure, and Material Properties From the Reaction Product of M(OCHMe 2 ) 4 (M=Ti, Zr) and HOAc
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Todd M. Alam+, Timothy J. Boyle, Catherine D. Buchheit, Robert W. Schwartz, and Joseph W. Ziller-+, Sandia National Laboratories, The Advanced Materials Laboratory, Albuquerque, NM, +Dept. of Chem., U. of N.M., Albuquerque, NM, !Dept. of Chem. U.C.-Irvine, Irvine, CA.
ABSTRACT In attempt to ultimately control the characteristics of the PZT films, we have decided to investigate some of the basic chemistry associated with these solutions. Frequently, these solutions have been generated from Group IV metal alkoxides in acetic acid (HOAc). Therefore, studies of the simple reactivity between M(OCHMe 2 )4 (M = Ti, Zr) and HOAc have been undertaken. These reactions were monitored by 1H, 13C, 170 NMR, FT-IR, TGA/DTA, and single crystal X-ray studies. Films were produced from spin-coat deposition of crystalline material (from the titanium reaction) in toluene and aged solutions as well.
INTRODUCTION Precursor solutions for sol-gel PZT thin films have been generated from mixed-metal alkoxides in acetic acid (HOAc). 1 ,2 Due to the difficulty in identifying the pertinent precursors in a ternary system, we have investigated the simple reactivity between "M(OCHMe 2 )4" (M = Ti, Zr) and n HOAc, where n = 1 or 2. The time of formation of the products (i.e., aging effects), the identity of pertinent precursors formed in these reactions, and the differences in the films produced by these solutions are the main points of interest of this investigation. These reactions have been monitored by 1H, 13C, and 170 NMR. Products were identified by NMR, FT-IR, TGA/DTA, elemental analysis, and single crystal X-ray studies, when possible. Densification properties and thickness of the films were investigated using ellipsometry. These experiments have been combined to produce a fundamental understanding of the process for formation of the initial precursors.
RESULTS AND DISCUSSION Solid state X-ray. X-ray crystallographic studies were undertaken of the reaction product from Eq. 1. This compound was formed under an inert atmosphere over an extended period of time. The HOAc + Ti(OCHMe 2 )4
-
neat
- Ti 6 (OCHMe 2)12 (OAc) 40 4 +
....
Eq. 1
product formed is Ti 6 (OCHMe 2 )12 (OAc) 4 0 4 , 1 (Figure 1 is a ball stick representaticn of the crystalline complex isolated). The structure of this compound is consistent with the complex found previously. 3 From a reaction stoichiometry of 1 to 2 Ti(OCHMe 2 )4 to HOAc (Eq. 2), another compound of similar geometrical arrangement was isolated. It is Ti 6 (OCHMe2)8(OAc) 8 0 4 , 2. 35 Mat. Res. Soc. Symp. Proc. Vol. 346. 01994 Materials Research Society
Figure 2 is a ball stick representation of 2. The yields of these products have not been determinec HOAc + Ti(OCHMe2) 4
Ti 6 (OCHMe 2 )8 (OAc) 8 0 4 +
neat
....
Eq. 2
as of yet; however, based on the initial stoichiometry and collected data, other minor products should exist. Both the 1 to I and 1 to 2 stoichiometries of [Zr(OCHMe 2 )4 *HOCHMe 2] 2 and HOAc reaction products are being determined. Infra red. 4 The FT-IR spectra 4 a obtained for th
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