Sol-Gel Deposition of Electronic Ceramic Films
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SOL-GEL DEPOSITION OF ELECTRONIC CERAMIC FILMS. J.M. BELL*, B. BEN-NISSAN*, M. ANAST*, B.O. WEST**, L. SPICCIA**, J. CULLEN**, I. WATKINS*** and D. deVILLIERS**, G. JOHNSTON**** *University of Technology, Sydney, P.O. Box 123, Broadway, NSW, 2007 Australia "**Department of Chemistry, Monash University, Clayton, Victoria, 3168, Australia ***Department of Chemistry, Monash University; and Silicon Technologies Australia, 22 Sophia Street, Crows Nest, NSW, 2065, Australia ***Defence Science and Technology Organisation, P.O. Box 50, Ascot Vale, Victoria, 3032, Australia. ABSTRACT We describe a dip-coating method of depositing thin electronic ceramic coatings on various substrates from sol-gel solutions. The solutions we use are alkoxide-based, although the specific formulations depend on the system being deposited. We are working with two electronic ceramic systems: barium titanate on glass, and alumina, and yttrium barium copper oxide on alumina. We discuss methods used to reduce and remove processing defects such as crazing, cracking and pin-holing. We are also studying the effects of varying the processing conditions (dipping, hydrolysis and firng) on the electronic properties of the films. Initial results on BaTiO 3 indicate that it is better to deposit thin films (-0.-1 - 0.2pim) and build up the coating thickness by repeated dipping. INTRODUCTION Deposition of electronic ceramic films, and in particular optical thin films from sol-gel solutions, has been successfully used for many systems 1,in particular cadmium stannate C3 and indium tin oxide 4.5. We are using alkoxide based sol-gel solutions to deposit various other electronic ceramics in thin film form. Currently we are studying thin films of barium titanate (BaTiO 3) and the high Tc superconductors YBa 2Cu 3 0 7 (referred to as 123). There have already been many publications in this rapidly growing field on the deposition of the superconductors using sol-gel methods. Two current reviews covering this work into early 1988 6.7 include the use of alkoxide based solutions. In several of the reports spin coating is used as the deposition technique, while numerous groups have reported superconductor preparation using aqueous solution techniques. We are using alkoxide based solutions and a dip-coating deposition method in our work as this has proved very successful for other systems 1 The principal advantages of the sol-gel processing technique for thin films is the same as for bulk materials - a possible lowering of the sintering temperature required to form the ceramic with a desired crystal structure. This can be particularly beneficial in ceramic coatings as interactions with substrates can be a major problem, particularly with the high Tc superconductors 8. Dip-coating also provides the possibility of large scale processing and good film homogeneity over large areas FILM PREPARATION There are two main aspects to the film deposition technique we are using: preparation of appropriate solutions; and deposition of the film, including the conditions during dipping,
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