Electrical transport properties of In-doped Ce1-xInxO2-δ (x=0.1; 0.2)

We report the synthesis and electrical conductivity of fluorite-type Ce1-xInxO2-delta (x = 0.1; 0.2) in air, dry Ar, N-2 and H-2 in the temperature range of 300-800 degrees C. We have employed a new CO2 capture technique to prepare the "metastable" fluorite-related structure Ce1-xInxO2-delta from the corresponding In-doped Ba-containing perovskite of the nominal chemical formula BaCe1-xInxO2-delta at 800 degrees C. The amount of CO2 gained per ceramic gram was found to be consistent with the formation of BaCO3, confirming the complete leaching of Ba in BaCe1-xInxO3-delta. The CO2 capture efficiency was found to be in the range of 90-99% at 800 degrees C, which is significantly higher than those of well-known low-temperature CO2 absorbing materials, including Li2O, Li6Zr2O7, Li1.8Na0.2ZrO3 and LiNaZrO3. Powder X-ray diffraction (PXRD) and energy dispersive X-ray analysis (EDAX) confirmed the perovskite into fluorite structural transformation reaction. The AC impedance study showed a clear intercept to the real axis at the low-frequency over the investigated temperatures in all the atmospheres, indicating a non-blocking nature of electrode (Pt) and electrolyte interface. The constant phase element (CPE) value was found to be in the order of 10(-10) F in air, N-2 and Ar for high-frequency part of the semicircle due to bulk contribution, and about two orders of magnitude lower values were observed for the low-frequency semicircle which may correspond to grain-boundary effect. The 20 mol% In-doped CeO2 exhibits a total electrical conductivity of about 4 10(-6) S/cm at 600 degrees C in Ar, while in H-2 an about four orders of magnitude higher electrical conductivity of 3 10(-2) S/cm was observed. The activation energy for electrical conductivity was found to be 1.36 eV in Ar, 1.43 eV in N-2, 1.34 eV in H-2, and 1.1 eV in air for Ce0.8In0.2O1.9.