As-Sintered Manganese-Stabilized Zirconia Ceramics with Excellent Electrical Conductivity

As promising electrolyte materials in intermediate-temperature solid oxide fuel cells (IT-SOFCs), Sc-stabilized ZrO${}_2$ (ScSZ) and Y-stabilized ZrO${}_2$ (YSZ) electrolytes continue to be plagued by high cost and low intermediate conductivity. To mitigate these problems, Mn has been chosen as a new stabilization element for the synthesis of Mn-stabilized ZrO${}_2$ ceramics (MnSZ) through solid state sintering. Microstructures and electrical properties of micron-crystalline ${\mathrm{Zr}}_{1-x}{\mathrm{Mn}}_x$O${}_{2-\delta }$ (x = 0.15, 0.20 and 0.25) ceramics electrolytes for IT-SOFCs have been systematically evaluated. Within the applied doping content, Mn${}^{2+}$ ions can enter the ZrO${}_2$ crystal lattice, leading to the formation of single cubic phase samples. Electrical conductivity measurements in the temperature range between 400 °C and 1000 °C show a sharp increase in conductivity due to Mn doping. The highest conductivity is obtained from the Zr${}_{0.75}$Mn${}_{0.25}$O${}_{2-\delta }$ samples, being 0.0144 S/cm at 600 °C and 0.182 S/cm at 1000 °C. The electrical conductivity at 600 °C is twice higher than that of the YSZ and two orders of magnitude higher than that of the ScSZ. These properties can fulfill the conductivity requirement (∼1 $\times {10}^{-2}$ S/cm) for the electrolyte. Therefore, based on this study, we propose that Mn stabilized ZrO${}_2$ is a promising candidate as a solid electrolyte for IT-SOFCs.