Fused filament fabrication and characterisation of 3- and 8-YSZ-based SOFC electrolytes

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The present work reports the fabrication via FFF-3D printing of 3- and 8-YSZ electrolytes, which are considered the current state-of-the-art of electrolyte materials for high temperature fuel cells (i.e., SOFCs), using filaments with ceramic loadings in the 65 to 75 wt % range. Filaments, green bodies and sintered specimens have been produced and fully characterised using thermal, structural, morphological, rheological and electrochemical techniques. The 3D printed electrolytes exhibit chemical stability under the debinding and sintering conditions, without significant microstructural changes when compared to conventional press and sinter processing and very high relative densities, compatible with SOFC operation, i.e. >95%. The conductivity of the 3D printed electrolytes was 0.05 and ≈0.1 S/cm at 1000 °C, for 3- and 8-YSZ respectively, which is very close to the values typically reported for conventionally processed zirconia electrolytes. These results confirm the potential application of FFF-3D printing technology towards the production of a new generation of electrochemical devices for energy production, such as SOFCs, with larger volumetric and surface energy densities and without their current geometrical limitations.