Synthesis, crystal chemistry, and electrical, oxygen permeation, and magnetic properties of LaSr3GaFe2 − xCoxO10 − δ (0 ≤ x ≤ 2 and 0 ≤ δ ≤ 2)
Abstract
The crystal chemistry and electrical, oxygen permeation, and magnetic properties of the n
= 3 member of the Ruddlesden–Popper (R–P) series of phases LaSr3GaFe2 −
xCoxO10 −
δ, with 0 ≤
x
≤ 2 and 0 ≤
δ
≤ 2, have been investigated. While the orthorhombic cell parameters a and b and the unit cell volume decrease, the c parameter increases with increasing Co content. Conductivity measurements show that the samples exhibit a thermally activated process, with 0.17 ≤Ea
≤ 0.35 eV. The oxygen permeation flux values (jO2
≈ 1 × 10−9 mol s−1 cm−2) at 900 °C across 1.5 mm thick LaSr3GaFe2 −
xCoxO10 −
δ
membranes are two orders of magnitude lower than those observed previously with other n
= 2 and 3 R–P phases (tetragonal) due to the orthorhombic distortion and negligible oxygen vacancy concentration gradient across the membrane. The reduction of the LaSr3GaFe2 −
xCoxO10 −
δ phases in a mixture of 90% Ar and 10% H2 leads to the formation of LaSr3GaFe2 −
xCoxO9 −
x/2 phases containing Co2+ and with orthorhombic symmetry.