Relation between interfacial adhesion and hardness of electrode materials in electrolyte supported solid oxide cells

Solid oxide cells (SOCs) need to be robust to withstand high thermo-mechanical stress inside the stacks at temperatures longer than 800 °C during operation. To determine this robustness of SOCs, it is necessary to investigate key mechanical properties of the electrolyte and electrodes as well as the interfacial adhesion within the membrane electrode assembly (MEA). Without adequate adhesion between the electrolyte and the electrodes, the cell performance might degrade, leading to reduced stack performance. In the present study, the key mechanical properties such as hardness and elastic modulus of the gadolinium doped ceria oxide (GDC) barrier layer along with the nickel oxide (NiO) and GDC based fuel electrode (NiO/GDC) as well as the air electrode composed of lanthanum strontium cobalt ferrite (LSCF) and GDC (LSCF/GDC) were determined by means of micro-indentation tests. Subsequently, the interfacial adhesion strength between the GDC barrier layer and the 3 mol % yttria stabilized zirconia (3YSZ) electrolyte as well as the interfacial adhesion strengths between the electrode composites and the 3YSZ electrolyte in ultrathin SOCs (140–150 μm) were evaluated by scratch tests. It was observed that the GDC barrier layer had ∼80 % higher interfacial adhesion strength with the 3YSZ electrolyte than the electrode composites. Additionally, a relation was found that with the increase of hardness of the electrode materials, the interfacial adhesion between the electrode materials and electrolyte increases. The obtained results might contribute to the further optimization of the manufacturing process and long-term operations of SOCs.