Papers by Author: Maria Teresa Colomer

Abstract: Yttria stabilized zirconia (YSZ) is the most common electrolyte in solid oxide fuel cells (SOFC). The planar configuration is widely used for designing single cells, in which a thick cathode layer can be used as the supporting electrolyte film. The manufacture of the semi-cell formed by anode and electrolyte has been widely studied and there are many works dealing with its colloidal processing. However, the semi-cell formed by cathode and electrolyte has received much lower attention. This work deals with the manufacture of a semi-cell consisting of YSZ as electrolyte and strontium-doped lanthanum manganite (LSM) as a cathode through a colloidal processing route. The colloidal behavior of diluted suspensions of YSZ and the rheology of their concentrated suspensions were studied as a function of deflocculant content, mixing time by using ultrasounds probe and ageing time. The colloidal stability of aqueous suspensions of LSM was studied by measuring the zeta potential as a function of pH and deflocculant content. These concentrated suspensions were used to obtain thick self-sustained substrates by casting methods. The YSZ electrolyte and LSM cathode were prepared by tape casting in water medium.

Abstract: Colloidal sol-gel is a common method used for the preparation of stable and homogeneous sols and thin films. The nanoparticulate sols can be easily deposited by EPD, which is a versatile technique for producing denser and thicker coatings than those produced by other techniques like dipping. A complete characterization of the sols, such as colloidal stability and electrophoretic mobility, which can be determined through zeta potential measurements, as well as the influence of deflocculants in the surface properties, is needed before using electrophoretic deposition. In this work, we have prepared sols of TiO₂ with an alkoxide:water molar ratio of 50:1 and Eu (III) doped-TiO₂ (2 mole % Eu (III)) using as precursors titanium (IV) isopropoxide and europium (III) acetate hydrate, respectively. The stability of the particulate sols was studied in terms of conductivity, zeta potential and viscosity evolution. Anatase stable sols, after peptization and without the use of any additive, were deposited on stainless steel substrates by electrophoretic deposition under both constant current and constant voltage conditions. Using different intensities and deposition times we have obtained thin films with different features (thicknesses and morphology) and different optical properties. The presence of europium (III) increases particle size, viscosity and peptization time and decreases the band gap of TiO₂.