Effect of strontium on Nd doped Ba1−xSrxCe0.65Zr0.25Nd0.1O3−δ proton conductor as an electrolyte for solid oxide fuel cells

This paper investigated the Sr doping effect on the microstructure, chemical stability, and conductivity of Ba1-x Sr x Ce0.65Zr0.25Nd0.1O3-δ (0 ⩽ x ⩽ 0.2) electrolyte prepared by sol-gel method. The lattice constants and unit cell volumes were found to decrease as Sr atomic percentage increased in accordance with the Vegard law, confirming the formation of solid solution. Incorporation of Sr into the composition resulted in smaller grains besides suppressing the formation of secondary phases of SrCeO3. Among the synthesized samples BaCe0.65Zr0.25Nd0.1O3-δ pellet with orthorhombic structure showed highest conductivity with a value of 2.08 × 10-3 S/cm(dry air) and 2.12 × 10-3 S/cm (wet air with 3% relative humidity) at 500 °C due to its smaller lattice volume, larger grain size, and lower activation energy that led to excessive increase in conductivity. Ba0.8Sr0.2Ce0.65Zr0.25Nd0.1O3-δ recorded lower conductivity with a value of 4.62 × 10-4 S/cm (dry air) and 4.83 × 10-4 S/cm (wet air with 3% relative humidity) at 500 °C than Sr undoped but exhibited better chemical stability when exposed to air and H2O atmospheres. Comparisons with the literature showed the importance of the synthesis method on the properties of the powders. Hence this composition can be a promising electrolyte if all the values such as sintering temperature, Sr dopant concentration, and time are proportionally controlled.