SOLUTION COMBUSTION SYNTHESIS OF A GREY (Co)CeO2 PIGMENT FOR PORCELAIN STONEWARE

Reference	Presenter	Authors (Institution)	Abstract
16-003	Sergio Mestre	Mestre, S.(Universitat Jaume I); Palacios, M.D.(Universitat Jaume I); Sanz, V.(Universitat Jaume I); González-Dávila, J.M.(Universitat Jaume I);	Solution combustion synthesis (SCS) is an emerging wet-chemical technology which allows the generation of chemically and thermally stable mixed oxides applying low temperatures and very short soaking times. The fast kinetics also allows the research of alternative combinations of host matrix and chromophore, which are difficult to synthesize by the slow diffusion mechanisms of the solid-solid reactions characteristic of the traditional ceramic method. The solid solutions between CoO and CeO2 synthesized by SCS have been investigated as ceramic pigments for porcelain stoneware. The raw materials for the pigment were cobalt nitrate and ammonium cerium nitrate, and glycine was the fuel. The aqueous solution of the precursors was inserted in a furnace stabilized at 500 ºC. After 20 minutes, the furnace was cooled down, and a fluffy dark grey powder was obtained. A composition interval up to 30 mol% CoO - 70 mol% CeO2 was investigated. All the pigments were constituted by a cerianite-type phase, without detecting secondary phases related to cobalt oxide. Accordingly, the solid solution had been formed, but the crystallinity of the product was lower for the higher contents of cobalt. The microstructure was a very porous powder, constituted by submicronic grains. The colouring power was tested in an industrial composition of porcelain stoneware. No defects, like bubbles or pinholes were detected in the fired specimens, a fact that points to a good stability of the pigment against the reaction with the vitreous phase generated during firing. The specimens showed a grey colour, which reduced its luminosity as the proportion of cobalt increased. In addition, the green shade increased a little and there was a change from a yellowish shade to a bluish one. Acknowledgements: authors thanks Universitat Jaume I for its support (Project no.P11B2015-04).
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