Chemical reactions and thermal expansion mismatch between electrodes and electrolyte may reduce the long term stability of SOFC-single cells and can cause undesirable thermomechanical stresses. In solid electrolyte cells the formation of MnA1204 was detected between the air electrode (La0.sCao.sMnO3) and the electrolyte (YSZ/AI203) in a 5 gm diffusion zone within the electrolyte. The electronically conducting spinel MnA1204 is thought to be the main factor for delamination of the air electrode under anodic current (electrolysis). The performance and long term stability of the air electrode/electrolyte interface can be improved for electrolysis conditions by an additional intermediate YSZ-layer made by sol-gel technique. The mismatch in thermal expansion between the electrode materials and the electrolyte have been eliminated via optimized doping and by adding small amounts of a silicate-based substituent with a very low thermal expansion coefficient for the cathode and anode, respectively.
|Publication status||Published - 1997|