Structured porous Ni- and Co-YSZ cermets fabricated from directionally solidified eutectic composites

• Published in: Journal of the European Ceramic Society Vol. 25; no. 8; pp. 1455 - 1462
• Main Authors: Laguna-Bercero, M.A., Larrea, A., Peña, J.I., Merino, R.I., Orera, V.M.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Oxford Elsevier Ltd 2005; Elsevier
• Subjects: Applied sciences; Building materials. Ceramics. Glasses; Ceramic industries; Cermets, ceramic and refractory composites; Chemical industry and chemicals; Composites; Directionally solidified eutectics; Electrical conductivity; Electrotechnical and electronic ceramics; Exact sciences and technology; Fuel cells; Technical ceramics; Composites; Electrical conductivity; Directionally solidified eutectics; Fuel cells; Ceramic matrix composite; Directional solidification; Porous material; Oxide ceramics; Composite material; Optical microscopy; Zirconium oxide; Manufacturing; Electroceramics; Cobalt oxide; Scanning electron microscopy; Electrical properties; Stabilized zirconia; Experimental study; X ray diffraction; Cermet; Yttrium oxide; Structured matrix; Microstructure; Laser assisted process; Nickel oxide
• ISSN: 0955-2219; 1873-619X
• DOI: 10.1016/j.jeurceramsoc.2005.01.025

NiO-YSZ and CoO-YSZ eutectic rods were produced by directional solidification using the laser floating zone method (LFZ). This technique produces highly structured material consisting of alternate lamellae of transition metal oxide and zirconia with variable interlamellar spacing depending on growth conditions. We have chosen conditions for interlamellar spacing of about 1 μm. The microstructure is homogeneous and mechanically stable during thermochemical reduction. Complete reduction of the transition metal oxide produces a lamellar porous cermet with porous metallic lamellae alternated with the YSZ phase. The thermal expansion coefficients of the cermets are those of the YSZ skeleton. Reaction kinetics at different temperatures during the reduction process were studied by gravimetric methods. The reduction process within the complete temperature range studied for NiO-YSZ, and at high temperatures for CoO-YSZ seems to be controlled by the O 2− diffusion through the YSZ phase. The amount of Ni 2+ and Co 2+ ions dissolved in the YSZ phase is 2 and 5 mol%. Resistivity values for the cermets along the solidification axis are 50 μΩ cm for Co-YSZ and 130 μΩ cm for Ni-YSZ. These materials are porous, ionic and electronic conductors and could be used as textured anodes for solid-oxide fuel cells (SOFC).