Synthesis and characterization of oxyanion (phosphate, sulphate) doped Ba2Sc2−yGayO5

In this paper we examine the effect of partial substitution of Ga for Sc in the oxyanion (phosphate, sulphate) containing perovskites, Ba2Sc2−xPxO5+x and Ba2Sc2−xSxO5+3x/2 with the samples analysed through a combination of X-ray diffraction, TGA, Raman spectroscopy and conductivity measurements. The results demonstrate that in both cases, Ga can be incorporated in place of Sc up to 40%. In order to accommodate the increasing Ga content, a reduction in the oxyanion content is required. Thus for the highest Ga content sample achieved, only 10% oxyanion incorporation was achieved giving endmember compositions of Ba2ScGa0.8P0.2O5.2 and Ba2ScGa0.8S0.2O5.3 for phosphate and sulphate doping respectively. While the Ga doping was shown to significantly improve the stability of the systems towards CO2 containing atmospheres, conductivity measurements showed a reduction in the conductivity with increasing Ga content.