Synthesis and characterization of proton conducting oxyanion doped Ba _2Sc_2O_5

摘要

In this paper we report the successful synthesis of the cubic oxyanion containing perovskites, Ba_2Sc_(2-x)P_xO _(5+x) (x = 0.4, 0.5), with the samples analysed through a combination of X-ray diffraction, NMR, TGA, Raman spectroscopy and conductivity measurements. Conductivity measurements indicate a p-type contribution to the conductivity in oxidizing conditions at elevated temperatures, with evidence for proton conduction in wet atmospheres. For the latter, bulk conductivities of 5.9 × 10~(-3) and 1.3 × 10~(-3) S cm~(-1) at 500 °C were obtained for x = 0.4 and 0.5 respectively, comparable to other perovskite proton conductors, while the stability towards CO_2 containing atmospheres was improved compared to BaCeO_3 based systems. Related Si doped systems have also been prepared, although in this case small Ba_2SiO_4 impurities are observed. We also provide evidence to suggest that "undoped" Ba_2Sc_2O_5 contains carbonate groups, which accounts for its thermal instability. This journal is