Influence of iso-valent 'Sm' double substitution on the ionic conductivity of La0.9Sr0.1Al0.9Mg0.1O3-δ ceramic system

The La0.9Sr0.1Al0.9Mg0.1O3-delta is considered as a promising perovskite to be used as electrolyte in Solid Oxide Fuel Cell due to good ionic conductivity (similar to 10(-3) S/cm) with high transference number similar to 0.99. The oxide ionic conductivity can be altered with the critical triangle area which is affected by size and nature of substituent. In the lack of comprehensive study on influence of double-substitution, we have synthesized substituted systems A '' xLa0.9-xSr0.1Al0.9Mg0.1O3-delta with x = 0.01, 0.03 and 0.05, here A '' = Ba (aliovalent) and Sm (isovalent) having R (3) over barc symmetry. The electrical conductivity data is analyzed using Rice - Roth's free-ion like model for ionic conduction and hopping transport mechanism (Arrhenius model). The defect chemistry suggests that Ba substituted compositions have concentration dependent oxygen content. Whereas, Sm substituted compositions have concentration independent oxygen content. This is verified using thermogravimetric analysis in N-2 and O-2 atmospheres. Our results also revealed that the aliovalent substitution of Ba effectively increases the ionic conductivity with high transference number, while isovalent substitution of Sm increases the electronic contribution to the total conductivity.