(499b) Sintering Behaviour of in-Situ Doped Nanoparticles by Flame Spray Pyrolysis for Fuel Cell Applications | AIChE

(499b) Sintering Behaviour of in-Situ Doped Nanoparticles by Flame Spray Pyrolysis for Fuel Cell Applications


Halim, S. C. - Presenter, Swiss Federal Institute of Technology (ETH Zurich)
Jud, E. - Presenter, MIT, Department of Materials Science

Ceramic oxygen ion conductors play a key role in solid oxide fuel cells (SOFC) with high power output. Ceria-based electrolytes are considered to be very promising due to their high ionic conductivity in comparison to the commonly used electrolyte material yttria-stabilized zirconia (YSZ). Small amounts of transition metal oxides have shown to be very effective sintering aids for Ce0.8Gd0.2O1.9 (CGO20) and Ce0.9Gd0.1O1.95 (CGO10) [1-4]. Adding as few as 1 mol% of cobalt oxide resulted in much lower sintering temperatures (900°C), higher shrinkage rates, and grain sizes in the final sintered product in the sub-micron range (~120 nm). Several investigations indicated that the necessary and sufficient dopant concentration lies below the reported 2 mol%. It was argued that improved homogeneity of the dopant phase by using a more suitable doping process would reduce the necessary concentration while maintaining the same sintering effect. In order to test this hypothesis, we used an alternative one-step preparation route to Cobalt oxide doped CGO. Flame spray pyrolysis (FSP) has been established as a reliable production process for mixed oxide nanoparticles of high phase homogeneity [5,6]. The continuous high temperature gas process uses suitable organic derivatives of the desired metals as homogeneous mixtures. The precursors are directly sprayed into a flame where they are rapidly converted into the corresponding mixed oxides. Here, we report on the successful pilot-scale preparation of CGO10 and in-situ cobalt oxide doped CGO10 powders by flame spray pyrolysis. We show that cobalt oxide as a dopant is already effective at concentrations as low as 0.1 mol%. At a dopant concentration of 1 mol%, the maximum sintering temperature is lowered by 250°C if compared to undoped CGO10 [7]. The results are further discussed in terms of materials preparation and application.

References: [1] C. Kleinlogel and L.J. Gauckler, Solid State Ionics, 135 567 (2000), [2] C. Kleinlogel and L.J. Gauckler, Adv. Mater., 13 1081 (2001), [3] G.S. Lewis, A. Atkinson, B.C.H. Steele, vol. 2, pp. 773 in Fourth European Solid Oxide Fuel Cell Forum. Edited by U. Bossel, 2000, [4] G.S. Lewis, A. Atkinson, B.C.H. Steele, J. Drennan, Solid State Ionics, 152 567 (2002), [5] L. Maedler, W.J. Stark, S.E. Pratsinis, J. Mat. Res., 17 1356 (2002), [6] W.J. Stark, M. Maciejewski, L. Mädler, S.E. Pratsinis, and A. Baiker, J. Catal. 220 (1) 35-43 (2003); W.J. Stark, L. Maedler, S.E. Pratsinis, Flame Made Metal Oxides WO 2004/005184 (2002), [7] E. Jud, S.C. Halim, W.J. Stark, L.J. Gauckler, J. Am. Ceram. Soc., accepted 2006.