Aqueous Synthesis of Nb and Ti Containing Oxides
D. A. Payne,* D. L. West, in collaboration with W. G. Klemperer and K. A. Marek in the Department of Chemistry
U.S. Department of Energy, DE-FG02-96ER45439 (In cooperation with the Materials Research Laboratory)

We are developing two synthetic routes to complex Nb and Ti containing oxides. The first (citrate gel) exploits the well-known complexing ability of carboxylic acids and the second (sequential precipitation) exploits the colloidal nature of freshly precipitated hydrous niobia and titania. Both procedures are carried out in the open air and involve no extremely air- or moisture-sensitive precursors. Currently, we are optimizing both routes with respect to properties of the synthesized product, required raw materials and process steps, and minimization/control or waste generation and process by-products.

Chemical Processing and Characterization of Ta2O5-TiO2
D. A. Payne,* S. Hemjinda
Nippon Steel Foundation

Thin films of TiO2-modified Ta2O5 were deposited on silicon substrates by sol-gel processing. Stable hydrolyzed solutions were prepared. With addition of dilute HCL, precipitation was avoided in solutions with Rw ratios greater than 1. Additions of Ti(ISP)4 not only improved the solution stability and promoted gelation, but also the onset of the crystallization temperature. The refractive index of Ta2O5-TiO2 films was determined to be dependent on Ti-content. Dense crack-free films with thicknesses ranging from 500-1000 A were successfully integrated on silicon. XRD data indicate the formation of a low-temperature orthorhombic Ta2O5 phase.

Self-assembly of Shape Invariant Nanoobjects
P. V. Braun,* E. Rogozhina, C. Heitzman
University of Illinois

In this work, we are attempting to synthesize hollow or nonspherical inorganic nanoobjects. Our first goal is the synthesis of hollow nanospheres. To accomplish this, we are using micellar objects as templates for the formation of silica nanospheres. Through the use of appropriate chemically modified organosilicon compounds, we believe we can prevent the aggregation of individual nanospheres into larger objects and also tailor the chemistry of their surfaces. To date, we have synthesized a series of modified organosilicons and are currently investigating their self-assembly with cationic and anionic surfactants.

Unique Microstructures in Ferroelectric Perovskites by Reaction Sintering
D. A. Payne,* D. L. West, P. Han
U.S. Department of Energy, DE-FG02-96ER45439 (In cooperation with the Materials Research Laboratory)

Reaction sintering involves reacting and densifying two or more solid phases without the usual intermediate comminution of the reacted single-phase material. In this work, we intend to produce ceramic monoliths with tailored microstructures by reaction sintering chemically prepared oxide mixtures and 'seed' particles of carefully controlled composition and morphology.