Reactive sputtering deposition and electrochemical characterisation of thin solid electrolyte membranes for solid oxide fuel cells
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- Wanzenberg, E., Tietz, F., de Haart, L.G.J. et al. Ionics (2002) 8: 142. doi:10.1007/BF02377765
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Solid oxide fuel cells directly convert the chemical energy of a fuel into electricity. To enhance the efficiency of the fuel cells, the thickness of the gastight solid electrolyte membranes should be as thin as possible.
Y2O3-stabilised ZrO2 (YSZ) electrolyte films were prepared by reactive sputtering deposition using Zr/Y targets in Ar/O2 atmospheres. The films were 5 – 8 μm thin and were deposited onto anode substrates made of a NiO/YSZ composite. After deposition of a cathode with the composition La0.65Sr0.35MnO3 the electrochemical properties of such a fuel cell were tested under operating conditions at temperatures between 600 °C and 850 °C. Current-voltage curves were recorded and impedance measurements were performed to calculate apparent activation energies from the fitted resistance data. The conductivity of the YSZ films varied between 4.6·10−6 S/cm and 2.2·10−5 S/cm at 400 °C and the fuel cell gave a reasonable power density of 0.4 W/cm2 at 0.7 V and 790 °C using H2 with 3 % H2O as fuel gas. The gas compositions were varied to distinguish the electrochemical processes of the anode and cathode in the impedance spectra.