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

Abstract

The La0.9-xSr0.1Al0.9Mg0.1O3-δ is considered as a promising perovskite to be used as electrolyte in Solid Oxide Fuel Cell due to good ionic conductivity (~10−3 S/cm) with high transference number ~ 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-δ with x = 0.01, 0.03 and 0.05, here A″ = Ba (aliovalent) and Sm (isovalent) having R3‾c 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 N2 and O2 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. © 2019 Elsevier B.V.