The Effect of TiO2 Addition on the Electrical Properties of Ce0.8Sm0.2O2−δ Electrolyte Material for SOFCs

Abstract

Sm and Ti co-doped ceria-based mixed ion-electronic conductor with the compositions of Sm0.2Ce0.8−xTixO2−δ (x = 0–0.15) are prepared by a gel-casting process. The effects of addition of Ti on the phase compositions, the sintering behavior, and the electrochemical properties of sample are investigated. The article tentatively discusses the relation of conductivity with Po2 by defect principles. Results show that the single-phase fluorite structure can be formed only at 500 °C, the addition of certain quantity TiO2 can promote the sintering densification with a uniform grain growth. When the sintering temperature is 1350 °C, the sample with 10% addition of Ti has the highest relative density, it reaches 98.94% of the theoretical density, which is much higher than the one prepared by the solid state method. The conductivity of samples decreases while the conductive activation energy increases by adding TiO2. Besides, it should not be neglected that the conductivity of samples in H2 is much higher than in air, which attributes to the reduction of Ti and Ce ions in reducing atmosphere. Overall, above test and analysis results suggest that TiO2 could be used only as an effective sintering aid but cannot as co-dopant on the optimization of electrical properties for ceria-based electrolytes.