Synthesis, crystal chemistry, and oxygen permeation properties of LaSr3Fe3−xCoxO10 (0≤x≤1.5)

The crystal chemistry and oxygen permeation properties of the mixed oxide-ion and electronic conductor LaSr3Fe3−xCoxO10 with 0≤x≤1.5 have been investigated. LaSr3Fe3−xCoxO10 has a perovskite-related intergrowth structure belonging to the n=3 member of the Ruddlesden–Popper series and the tetragonal cell parameters and volume decrease with increasing Co content. The LaSr3Fe3−xCoxO10±δ samples have excess (δ≈0.1) oxygen at room temperature, but significant amount of oxygen vacancies (0.3≤δ≤0.7) at high temperatures (900°C). The LaSr3Fe3−xCoxO10 samples are semiconducting with the total conductivity increasing with increasing Co content. However, above a transition temperature T>Tt≈400°C, the conductivity decreases with increasing temperature due to the loss of oxygen. The oxygen permeation flux across the LaSr3Fe3−xCoxO10 membranes at high temperatures (800°C≤T≤950°C) increases with increasing Co content and the flux values are stable with time in the oxygen partial pressure range 10−4≤pO2≤0.21 atm.