Assessing boron doped Ba₂In_1.8Si_0.2O_5.1 as a potential electrolyte for use in ceramic electrolyte fuel cells

Doped perovskite oxides have been widely studied in recent years as potential proton conducting electrolytes for electrochemical devices. One such system, Ba₂In₂O₅ transforms from an orthorhombic phase at room temperature to a cubic perovskite phase at high temperature, which results in a dramatic increase in ionic conductivity. In this paper, we report the incorporation of Boron (B) and Silicon (Si) at the Indium (In) cation site (Ba₂In_2-x-yB_xSi_yO_5+y/2) to stabilize the highly conducting cubic phase at room temperature, as well as lower the sintering temperature required. X-ray powder diffraction data of the synthesized powders sintered at 1250 ​°C reveal successful incorporation of Si and B at the In site with maximum solubility of 10 ​mol% for both, and conductivity measurements show an enhancement upon dopant incorporation. Further enhancement in conductivity was observed in measurements performed under wet N_2(g) atmosphere which is attributed to a protonic contribution to the overall ionic conductivity. In summary, the ionic conductivity of all the doped samples was shown to be at least an order of magnitude higher than that of undoped Ba₂In₂O₅ with the best performance observed for the Ba₂In_1.7B_0.1Si_0.2O_5.1 composition.