Chemical stability of SrCe0.95Yb0.05O3−α in hydrogen atmosphere at elevated temperatures

The influence of water vapor pressure, P(H2O), on chemical stability of SrCe0.95Yb0.05O3−α under hydrogen atmosphere was investigated using XRD and Raman spectroscopy. From an XRD study, a second phase assigned to Sr2CeO4 was observed under strongly reducing conditions such as dry H2 with P(H2O)=4.6×10 Pa [P(O2)=3.1×10−15 Pa] at 1273 K. From Raman spectroscopy, it was found that treated specimens under hydrogen atmosphere exhibited additional Raman bands, which may be assigned to the second phase. The relative intensity of the additional Raman band at 460 cm−1 drastically increased with decreasing P(H2O) in the region P(H2O)<7.0×102 Pa (2 °C sat.), whereas it was quite low in the region P(H2O)>7.0×102 Pa [P(O2)>3.0×10−14 Pa] at 1273 K. The perovskite phase proved to be stable against hydrogen with an increase in P(H2O) or a decrease in temperature.