8YSZ – Carbonate composite electrolyte-conductivity enhancement

Abstract

A composite electrolyte based on 8YSZ and Li/Na carbonate eutectic is prepared and characterized according to requirement of electrolytes. The powdered eutectic is mixed with 8YSZ powder in two different proportions. Sintered samples have been characterized by XRD, SEM and impedance spectroscopy. Fractured micrographs of the compositions show distinctly different morphology of the carbonate phase due the quantity of the carbonate phase addition. Impedance spectroscopy provides separate conductivities of the carbonate phase, YSZ phase, inter-phase boundary and that of the electrolyte-electrode interface. Equivalent circuits of the transport phenomena have been proposed. The conductivity of the carbonate phase is significantly higher than that of the YSZ phase and accordingly the overall conductivity of the composite electrolyte increases with increasing quantity of the carbonate phase. At 600 °C the composite with 20 wt% carbonate phase shows the conductivity of 1.6 × 10−3 S-cm−1 compared to 1.78 × 10−4 S-cm−1for pure 8YSZ.