Synthesis and evaluation of dysprosia doped zirconia electrolytes for microtubular solid oxide fuel cells

This study aims to investigate the synthesis, characterization, and electrochemical performance of dysprosia (Dy₂O₃)-stabilized zirconia (DySZ) as an electrolyte material for microtubular solid oxide fuel cells (SOFCs). The primary objective is to assess the effects of dysprosia doping on the stabilization of the cubic zirconia (ZrO₂) phase and its impact on ionic conductivity and cell performance. In this regard, (Dy₂O₃)_x(ZrO₂)_1-x powders are synthesized using modified sol-gel method for 0.08 ≤ x ≤ 0.12. X-ray diffraction (XRD) measurements reveal that the stabilization of the face-centered-cubic (fcc) ZrO₂ is observed at all doping ratios studied after calcining at 1200 °C, resulting in Dy₂O₃ stabilized zirconia. The lattice parameter increases with Dy doping, consistent with the substitution of smaller Zr⁴⁺ cations by larger Dy³⁺ cations. The electrochemical performance tests indicate that the cell efficiency decreases with increasing dysprosia content beyond 8 mol %. A peak power density of 0.238 W/cm² is measured from 8 mol % Dy₂O₃-stabilized zirconia (8DySZ) electrolyte, whereas 12 mol % Dy₂O₃-stabilized zirconia (12DySZ) electrolyte achieves a lower power density of 0.166 W/cm² under identical conditions. This decline is attributed to the diminishing ionic conductivity with the dopant amount, which compromises the efficiency of the DySZ electrolyte. The impedance analysis further corroborates these findings, showing a rise in both ohmic and charge transfer resistances with increasing dysprosia content. Microstructural investigations are also carried out and the results are evaluated. Overall, this research highlights the potential of 8DySZ as a promising alternative to traditional yttria-stabilized zirconia (YSZ) electrolytes in SOFCs.