A strategy for improving sinterability and electrical properties of gadolinium-doped ceria electrolyte using calcium oxide additive

In this study, Gd and Ca co-doped ceria electrolytes with the compositions of Ce0.8Gd0.2–xCaxO2–δ (x = 0–0.08) were prepared by a novel gel-casting method. The effects of the addition of Ca on the phase compositions, sintering behavior, and electrical properties of samples were investigated. According to the scanning electron microscope results and relative density measurement results, it is found that the addition of particular quantity of CaO can promote the sintering densification with a uniform grain growth. When the sintering temperature is 1400 °C, the sample with 6 mol% addition of Ca has the highest relative density, which reaches 98.5% of the theoretical density. The electrical properties testing results confirm that the electrical conductivity of the samples can be improved significantly by doping appropriate CaO content. The maximum conductivity of 0.082 S/cm can be obtained at 800 °C in the Ce0.8Gd0.12-Ca0.06O1.87 sample. It suggests that CaO can be used as an effective sintering aid and a co-dopant on the optimization of electrical properties for ceria-based electrolytes.