EVALUATION OF CHEMICAL EXPANSION EFFECTS IN Gd_0.1Ce_0.9O_1.95 USING MODULATED DILATOMETRY

Understanding and evaluating the correlation between the thermal, chemical and mechanical properties of SOFC building blocks materials is an industrial and scientific challenge. The structure of SOFC, where the various components are clamped together (anode/electrolyte/cathode) at a certain temperature, results in the development of stress between the materials while subjected to heating or cooling. This stems from the difference in thermal expansion coefficient (CTE) of the different materials. The strain above can result in asymmetric deformation of the SOFC components. Since SOFC operates at different environments (high PO₂/ Low PO₂) chemical expansion effects must be considered as well.

Modulated Dilatometry, presented here, is used for the evaluation of chemical expansion effects on total thermal expansion coefficient (CTE). Gd doped Ceria (GDC), one of the most promising electrolyte materials for intermediate temperatures SOFC due to its high ion conductivity at relatively low temperature exhibits chemical expansion upon SOFC operation conditions. The origin of chemical expansion is directly connected to oxygen vacancy formation upon changes in temperature and oxygen activity. The contribution of both the expansion upon reduction of Ce and contraction upon oxygen vacancy formation can be separated based on kinetic considerations and skin effect process using modulated dilatometry.