Mn-stabilized zirconia ceramics: Phase transformation and mixed ionic-electronic conductivity

Cubic-phased Mn-stabilized zirconia (Zr1−xMnxO2−δ) was fabricated by a co-precipitation calcination method and sintering at 1400°C in Ar. Within the solid solubility of Mn in the ZrO2 matrix, substitution solid solutions were gained without any other second phase. Bivalency Mn ions play an important part in the grain growth, densification, and phase stabilization mechanism. The intragrain, intergrain, and total conductivities were measured by AC impedance and four-probe DC methods. Electrical conductivity of Mn-stabilized ZrO2 ceramics increased with both increasing temperature and Mn concentration. Zr0.8Mn0.2O2−δ ceramic with the cubic structure possessed the highest conductivity of 0.2 and 4.15 S/m at 600°C and 1000°C, respectively. The activation energy decreased with increasing the Mn concentration, which was most likely due to the intergrain electronic conductivity. The single-cubic-phased structure, high electrical properties and low activation energy render this system potentially useful as electrode or electrolyte materials.