The influence of sol gel precursors and substrate type in the spin coating of CeO2 thin films.

CeO2 has been considered as an important material in view of potential applications in fuel cells, opto-electronic devices, high temperature applications and buffer layers for the deposition of ceramic superconductors. Among the chemical based processes for preparation of ceramic materials, sot gel techniques are very useful for obtaining bulk materials, thin films and fibers. The advantages of the sot gel method include low process temperatures, control of purity of reagents, the possibility to produce homogeneously mixed precursor powders on atomic scale with controlled stoichiometry and the potential for continuous operation. Our paper deals specifically with the aspects related to the composition and the degree of polymerisation in the gels. Crystalline CeO2 thin films with thicknesses ranging from 0,04 to I mum were obtained both on polycrystalline alumina, NiCuZn alloys and oriented Ni-Fe alloy flexible substrates by spin coating using aqueous and alcoholic solutions (ethanol, isopropanol, butanol) based on Ce(NO3)(3).6H(2)O and Ce(CH3COO)(3).nH(2)O in which HNO3 or citric acid were used as polymerisation catalysts with ethylene glycol. The deposition was followed by subsequent thermal treatment typically at 500 degreesC. The phase composition, crystallographic microstructure of the gels and films were characterised by XRD, SEM and TG-DTA.