Synthesis And Electrical Conductivity Of SrCe_1-xYb_xO(3-α) Ceramic

High-temperature protonic conductors have potential applications in fuel cells, gas sensors, membrane separators and membrane reactors, etc. Until now, many studies have focused on the synthesis and conduction properties of SrCe₀.95Yb₀.05O₃-a ceramic, but the relation between the dopant content, x, and the electric properties of SrCe₁-xYb_xO₃-a ceramic has not been investigated.In the present study, a series of proton-conducting perovskite-type oxide ceramics, SrCe₁-xYb_xO₃-a (x = 0.05, 0.10, 0.15, 0.20), were prepared by high-temperature solid state reaction. X-ray powder diffraction patterns show that the ceramics are of a single orthorhombic phase of perovskite-type SrCeO3. Using the ceramics as solid electrolytes and porous platinum as electrodes, the measurements of conductivities and ionic transport numbers of the ceramic samples were performed by using ac impedence spectroscopy and gas concentration cell methods in the temperature range of 600 1000 ℃ under the different atmospheres, respectively. We also measured the performance of hydrogen-air fuel cells based on the ceramic samples, and systematically studied the relation between the performance of fuel cells, the dopant content x and the ionic conductivity of ceramic samples.The main results are as follows:(1) the experimental atmosphere remarkably influenced the conductivity. In dry air, the samples are a mixed conductor of oxide-ion and hole (the oxide-ionic transport numbers of 0.03 0.19). In wet hydrogen, the protonic transport number is unity and the samples are almost pure protonic conductors from 600℃ to 800℃, but in the temperature range of 900 1000 ℃, the samples exhibited a mixed conduction of proton and electron (the protonic transport number > 0.88). In wet air, the samples are a mixed conductor of oxide-ion, the proton and hole.(2) The dopant content x in the samples remarkably influenced the conduction properties. SrCe₀.9Yb₀.1O₃-a has the highest ionic conductivity among the samples.(3) The dopant content x in the samples also remarkably influenced the hydrogen-air fuel cells based on the ceramic samples. The fuel cells had stable discharging performances. Among the fuel cells, the one based on SrCe₀.9Yb₀.1O₃-a exhibited the largest short-circuit density and power density, this is correlated with the highest ionic conductivity of the sample.