Synthesis and characterization of oxyanion (phosphate, sulfate) doped Ba$_2$Sc$_2$$_-$$_y$Ga$_y$O$_5$

Abstract

In this paper we examine the effect of partial substitution of Ga for Sc in the oxyanion (phosphate, sulfate) containing perovskites, Ba2Sc$_2$$_-$$_x$P$_x$O$_5$$_+$$_x$ and Ba$_2$S$_c$$_2$$_-$$_x$S$_x$O$_5$$_+$3$_x$$_/$$_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 Ba$_2$S$_c$Ga$_0$$_.$$_8$P$_0$$_.$$_2$O$_5$$_.$$_2$ and Ba$_2$S$_c$Ga$_0$$_.$$_8$S$_0$$_.$$_2$O$_5$$_.$$_3$ for phosphate and sulfate doping respectively. While the Ga doping was shown to significantly improve the stability of the systems towards CO$_2$ containing atmospheres, conductivity measurements showed a reduction in the conductivity with increasing Ga content