John L. Bradley

Tetragonal tungsten bronze type phases (Sr1-xBax)0.6Ti0.2Nb0.8O3-δ: Material characterisation and performance as SOFC anodes

The oxide material Sr0.2Ba0.4Ti0.2Nb0.8O3 was investigated for application as a potential anode material in solid oxide fuel cells (SOFCs). Impedance spectroscopy in air and DC conductivity measurements under varying oxygen partial pressure revealed high electronic conductivity of 10 S cm−1 [p(O2)=10−20 atm and 930°C]. Additionally these anode materials were tested in SOFC single cells. AC-impedance measurements under operation showed a Warburg type behaviour, which indicated a diffusion limited process. This diffusion limitation is most likely due to either low oxide ion conduction of the anode or due to a reaction layer formed during sintering of the anode onto the electrolyte at the relatively high temperatures of above 1250°C. Reactivity tests between YSZ electrolyte material and the Sr0.2Ba0.4Ti0.2Nb0.8O3 anode up to 1300°C showed the formation of t-ZrO2.