Micro-hotplates—A platform for micro-solid oxide fuel cells

Special high temperature micro-hotplates were investigated for their potential use as a technology platform for miniaturized solid oxide fuel cells (SOFCs). To evaluate the compatibility of these hotplates with typical SOFC materials and processing techniques, spray pyrolysis was used for the deposition of an SOFC cathode material (La_0.6Sr_0.4Co_0.2Fe_0.8O₃, LSCF) onto the micro-hotplate. The resulting microstructures and the electrical conductivity of the thin film (thickness ~500 nm) were characterized. Post-deposition annealing in external furnaces as well as using the integrated heater of the micro-hotplate confirmed that these micro-hotplates are suitable for a maximum operation temperature of 800 °C and a long-term operation at 600 °C. Very fast heating and cooling rates of several 100 °C min⁻¹ were achieved using the micro-hotplate as a heater, allowing fast processing and aging tests. Bending of the micro-hotplate was found to be critical to the integrity of the thin film, which coats the micro-hotplate. Bending might be reduced using other membrane materials.