Sol-gel synthesis of mesoporous CaCu{sub 3}Ti{sub 4}O{sub 12} thin films and their gas sensing response

• Published in: Journal of solid state chemistry 2010-06, Vol.183 (6)
• Main Authors: Parra, R., Savu, R., Ramajo, L.A., Ponce, M.A., Varela, J.A., Castro, M.S., Bueno, P.R., Joanni, E., Centro de Tecnologia da Informacao Renato Archer, Rodovia Dom Pedro I
• Format: Article
• Language: English
• Subjects: ACETIC ACID; ALKALINE EARTH METAL COMPOUNDS; ANNEALING; ATMOSPHERIC PRESSURE; CALCIUM COMPOUNDS; CARBOXYLIC ACIDS; COHERENT SCATTERING; COPPER COMPOUNDS; DEPOSITION; DIFFRACTION; ELECTRON MICROSCOPY; ELEMENTS; HEAT TREATMENTS; MICROSCOPY; MONOCARBOXYLIC ACIDS; NANOSCIENCE AND NANOTECHNOLOGY; NANOSTRUCTURES; NONMETALS; ORGANIC ACIDS; ORGANIC COMPOUNDS; OXYGEN; OXYGEN COMPOUNDS; SCANNING ELECTRON MICROSCOPY; SCATTERING; SEMIMETALS; SENSORS; SILICON; SOL-GEL PROCESS; SPIN-ON COATING; SURFACE COATING; TEMPERATURE RANGE; TEMPERATURE RANGE 0400-1000 K; THIN FILMS; TITANATES; TITANIUM COMPOUNDS; TRANSITION ELEMENT COMPOUNDS; X-RAY DIFFRACTION
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2010.03.033

A new sol-gel synthesis procedure of stable calcium copper titanate (CaCu{sub 3}Ti{sub 4}O{sub 12}-CCTO) precursor sols for the fabrication of porous films was developed. The composition of the sol was selected in order to avoid the precipitation of undesired phases; ethanol was used as solvent, acetic acid as modifier and poly(ethyleneglycol) as a linker agent. Films deposited by spin-coating onto oxidized silicon substrates were annealed at 700 {sup o}C. The main phase present in the samples, as detected by X-ray diffraction and Raman spectroscopy, was CaCu{sub 3}Ti{sub 4}O{sub 12}. Scanning electron microscopy analysis showed that mesoporous structures, with thicknesses between 200 and 400 nm, were developed as a result of the processing conditions. The films were tested regarding their sensibility towards oxygen and nitrogen at atmospheric pressure using working temperatures from 200 to 290 {sup o}C. The samples exhibited n-type conductivity, high sensitivity and short response times. These characteristics indicate that CCTO mesoporous structures obtained by sol-gel are suitable for application in gas sensing. - Graphical abstract: A sol-gel synthesis procedure toward stable CaCu{sub 3}Ti{sub 4}O{sub 12}-precursor sols avoiding the precipitation of undesired compounds is proposed. Films deposited by spin-coating onto oxidized silicon substrates were annealed at 700 {sup o}C. The thickness varied between 200 and 400 nm depending on sol composition. The films, tested as gas sensors for O{sub 2}, showed n-type conductivity, good sensitivity and short response times.