Stability of Ni–yttria stabilized zirconia anodes based on Ni-impregnation

Sintering of Ni is a key stability issue for Ni–YSZ anodes, and especially infiltration based electrodes. The potential of MgO, Al2O3, TiO2, CeO2 and Ce0.90Gd0.10O1.95 (CGO10) as sintering inhibitors was investigated for infiltrated Ni based anode structures. The structures were prepared from tape cast porous YSZ layers that were impregnated with Ni to form an electronic percolating phase. The Ni–YSZ structure was subsequently impregnated with the inhibitor candidate, and the stability of the structure was evaluated from conductivity measurements. Lower conductivity degradation rates were observed for samples infiltrated with the inhibitor candidates, and the best inhibitor effect was seen with higher loadings of CGO10, and CeO2 showed similar potential. The degradation in conductivity was not visibly reflected in the microstructure as Ni coarsening in any of the cases. An adverse effect of MgO, TiO2 and Al2O3 was reduced conductivity, possibly due to reaction with Ni and the formation of higher resistive phases. The Ni-infiltrated anodes were shown to have better initial electrochemical performance at 650 °C than conventionally produced Ni–YSZ anodes, but still very poor stability, and further improvement of the inhibitor approach is necessary before applying the Ni-infiltrated anodes in SOFCs.