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-i on and electronic conductor LaSr3Fe3-xCoxO10 with 0 less than or equal to x less than or equal to 1.5 have been investigated. LaSr3Fe3-xCoxO10 has a p erovskite-related intergrowth structure belonging to the n = 3 member of th e Ruddlesden-Popper series and the tetragonal cell parameters and volume de crease with increasing Co content. The LaSr3Fe3-xCoxO10 +/- delta samples h ave excess (delta approximate to 0.1) oxygen at room temperature, but signi ficant amount of oxygen vacancies (0.3 less than or equal to delta less tha n or equal to 0.7) at high temperatures (900 degreesC). The LaSr3Fe3-xCoxO1 0 samples are semiconducting with the total conductivity increasing with in creasing Co content. However, above a transition temperature T > T-t approx imate to 400 degreesC, the conductivity decreases with increasing temperatu re due to the loss of oxygen. The oxygen permeation flux across the LaSr3Fe 3-xCoxO10 membranes at high temperatures (800 degreesC less than or equal t o T less than or equal to 950 degreesC) increases with increasing Co conten t and the flux values are stable with time in the oxygen partial pressure r ange 10(-4) less than or equal to pO(2) less than or equal to 0.21 atm. (C) 2001 Elsevier Science B.V. All rights reserved.