Synthesis, Structure and Electrical Properties of Mo‐doped CeO 2 –Materials for SOFCs

In this paper, we report the synthesis, structure and electrical conductivity of Mo‐doped compounds with a nominal chemical formula of Ce 1– x Mo x O 2+δ ( x  = 0.05, 0.07, 0.1) (CMO). The formation of fluorite‐like structure with a small amount of Ce 8 Mo 12 O 49 impurity (JCPDS Card No. 31‐0330) was confirmed using a powder X‐ray diffraction (PXRD). The fluoride‐type structure was retained under wet H 2 and CH 4 atmospheres at 700 and 800 °C, while diffraction peaks due to metal Mo were observed in dry H 2 under the same condition. AC impedance measurements showed that the total conductivity increases with increasing Mo content in CMO, and among the investigated samples, Ce 0.9 Mo 0.1 O 2+δ exhibited the highest electrical conductivity with a value of 2.8 × 10 –4 and 5.08 × 10 –2 S cm –1 at 550 °C in air and wet H 2 , respectively. The electrical conductivity was found to be nearly the same, especially at high temperatures, in air, O 2 and N 2 . Chemical compatibility of Ce 0.9 Mo 0.1 O 2+δ with 10 mol‐% Y 2 O 3 stabilised ZrO 2 (YSZ) and Ce 0.9 Gd 0.1 O 1.95 (CGO) oxide ion electrolytes in wet H 2 was evaluated at 800–1,000 °C, using PXRD and EDX analyses. PXRD showed that CMO was found to react with YSZ electrolyte at 1,000 °C. The area specific polarisation resistance (ASPR) of Ce 0.9 Mo 0.1 O 2+δ on YSZ was found to be 8.58 ohm cm 2 at 800 °C in wet H 2 .