Improved Conductivity of Spark Plasma Sintered Ho-Substituted BaZrO₃ Electrolyte Ceramics for IT-SOFCs

The effect of spark plasma sintering (SPS) on Ho-substituted BaZrO3 electrolyte ceramics was investigated to enhance the electrical conductivity for intermediate temperature solid oxide fuel cells (IT-SOFCs). The cubic crystal system with Pm3̅m space group symmetry, unit cell parameters, and bond length were revealed through the Rietveld refined X-ray diffraction (XRD) pattern. The microstructure of BaZr0.9Ho0.1O3−δ (BZH10) and BaZr0.8Ho0.2O3−δ (BZH20) SPS samples was found to be highly dense and exhibits the mixed inter/trans granular fracture mode through FESEM analysis. The average grain size and relative density of SPS at 1600 °C for 20 min of Ho-substituted BaZrO3 ceramics were found to decrease with the increase of Ho-substitution in BaZrO3 ceramics. The electrical impedance spectroscopic (EIS) analysis was performed under air and 3% humidified O2 atmosphere as a function of probing temperature from 250 to 800 °C. Thus, the total electrical conductivity of SPS BZH20 sample was estimated to be 4.91 × 10–2 S-cm–1 at 700 °C under 3% humidified O2 atmosphere, which is the highest-class conductivity among all reported trivalent cation substituted BaZrO3 ceramics followed by spark plasma sintering.