Effect of varying Sr2+:La3+ ratio on the structure and electrical properties of SrLaAlO4 layered perovskite

Layered perovskite Sr 1.1 La 0.9 AlO 4-δ with the Ruddlesden-Popper structure was synthesized by the combustion method (glycine-nitrate soft-chemistry technique) and investigated as potential oxide-ion conductor for intermediate-temperature devices for electrochemical applications. X-ray diffraction analysis confirmed the formation of single-phase material with tetragonal symmetry (space group I4/mmm). The introduction of Sr 2+ cation in the position of La 3+ leads to the creation of oxygen vacancies and a significant increase in oxide-ion conductivity. At 600 °C, the conductivity increased by factors of 110 compared to the parent sample SrLaAlO 4 and reaches 2.8 · 10 −4 S cm −1 ; the activation energy decreased from 1.51 eV for SrLaAlO 4 compound to 0.81 eV for the Sr 2+ -substituted phase, as a result of the best balance between structural parameters (unit cell volume and free cell volume). The studied phase was stable over a wide range of P O 2 (10 −20 –0.68 atm) at 400–900 °C and in CO 2 -containing atmosphere (50% CO 2 :50% air). The present result endorses that the RP compounds based on aluminates are low-cost promising candidates for electrochemical devices.