Sol-gel deposition of oxide-ion conducting thin films ; and, Liquid precursors to hafnium and tantalum carbides

Abstract

I. The deposition of thin films of the BiMeVOx oxygen ion conducting ceramics was studied. The sol-gel precursor solution included a soluble form of bismuth acetate, a vanadium alkoxide, and the acetate or alkoxide of the dopant metal (Me). Copper-doped films were spincoated onto nonporous quartz substrates and pyrolyzed. These were initally defect-free, but became agglomerated on heating at higher temperatures. The use of a number of different additive compounds was tried, but did not greatly improve the behavior of the films on quartz substrates. These films, when deposited onto platinum-coated substrates, remained defect-free to all temperatures. Niobium-doped films remained defect-free on quartz substrates at all heating temperatures. The reasons for these behaviors are examined. Copper-doped films were deposited defect-free onto porous alumina substrates. The structure of a single-molecule bismuth-vanadium precursor in the sol-gel solution is suggested. II. Liquid precursors to refractory transition metal carbides were produced via both organometallic and metal alkoxide starting materials. These precusors were pyrolyzed under inert atmosphere and found to convert to the metal carbide, plus excess carbon, between 1100 °C and 1500 °C. The use of Grignard reagents to functionalize (chloromethyl)silylterminated carbosilane dendrimers was investigated briefly. The syntheses were plagued by long reaction times and low purities, contrary to the behavior expected for the (chloromethyl)silyl group. Reasons for this behavior are discussed.