Thermal Stability Behaviour of Scandia Stabilised Zirconia

Solid Oxide Fuel Cells (SOFCs) are emerging as an advanced and efficient energy conversion technology that could be a solution to some of the environmental issues. SOFCs are able to produce clean electricity and heat from hydrogen energy. Due to their high ionic conductivity in the intermediate temperature range of 600 °C to 800 °C, scandia stabilized zirconia is a very promising electrolyte material for SOFCs. However, the long term damage caused by cyclic heating and cooling during the stages of start-up and shut down of SOFC will greatly affect the performance of the fuel cell. The structural damages will result in poor mechanical properties which directly influence the durability of the ceramic electrolyte. Therefore, it is essential to investigate the thermal degradation behavior of various zirconia ceramic systems. In this work, the thermal degradation behavior of the zirconia ceramics are investigated by adopting thermal cycling test at two different heating rates (10°C/min and 20°C/min) to examine the durability of the zirconia electrolyte, in particular the structure degradation caused in thermal cycling. Ordered array of convex meniscus were observed on the surface of the undoped zirconia ceramics and the grain growth was suppressed during thermal cycling. The effect of thermal cycling on the mechanical stability of zirconia based ceramics were affected by the addition of 1 wt% MnO2 which showed a reduction in the hardness and fracture toughness.