Freeze-cast yttria-stabilized zirconia pore networks: Effects of alcohol additives

Freeze casting yttria-stabilized zirconia (YSZ) can be useful in making electrodes for solid oxide fuel cells (SOFCs) by introducing hierarchical porosity to increase triple-phase boundary (TPB) area while maintaining adequate fuel flow. Here, in this work, the influence of alcohol additives on pore structure of aqueous YSZ freeze-cast samples was investigated. Slurries with ethanol, iso-propyl alcohol, or methanol as additives were compared to a control sample. Pore characteristics along sample lengths were measured using X-ray computed tomography reconstructions. The control sample showed significant changes in pore size along sample length, whereas pore size of the alcohol additive samples remained similar, indicating that freezing rates of the additive samples remained constant during solidification. Finally, ice lens formation and interactions between alcohols and slurry functional additives (dispersant, surfactant, and binder) resulted in complex pore structures which show promise in increasing SOFC TPB area.