Oxide ionic conductivity of doped lanthanum chromite thin film interconnectors

Abstract

Lanthanum chromites doped with alkaline earth metals are candidate materials for SOFC interconnectors. The oxide ionic conductivity of the material is important in estimating the oxygen permeability through the interconnector. The oxide ionic conductivity ( σ i ) of lanthanum chromites was measured using the electron quasi-blocking method under various oxygen partial pressures. Dense lanthanum chromite films deposited on crystal yttria stabilized zirconia (YSZ) plates by laser ablation were used as specimens. Under high oxygen partial pressure ( P O 2 = 1 −10 −3 atm ), σ i ; increased proportional to the 1 2 power of P O 2 , while under low oxygen partial pressure ( P O 2 < 10 −4 atm) σ i increased as P O 2 decreased. These results indicate that the ionic conduction of lanthanum chromites is controlled by more than two mechanisms. Since the dependence of σ i on P O 2 under the low oxygen pressure is consistent with that of the oxygen vacancy concentration of lanthanum chromites, the ionic conduction at this range of P O 2 is interpreted to be controlled by the oxygen vacancy diffusion.