Oxygen permeation modelling of perovskites

A point defect model was used to describe the oxygen nonstoichiometry of the perovskites La0.75Sr0.25CrO3, La0.9Sr0.1FeO3, La0.9Sr0.1CoO3 and La0.8Sr0.2MnO3 as a function of the oxygen partial pressure. Form the oxygen vacancy concentration predicte by the point defect model, the ionic conductivity was calculated assuming a vacancy diffusion mechanism. The ionic conductivity was combined with the Wagner model for the oxidation of metals to yield an analytical expression for the oxygen permeation current density as a function of the oxygen partial pressure gradient. A linear boundary condition was used to show the effect of a limiting oxygen exchange rate at the surface

Mechanical Properties of Magnesia‐Doped Lanthanum Chromite versus Temperature

Magnesia‐doped lanthanum chromite is a potential material for use in solid oxide fuel cells as an interconnector due to its resistance to oxidation and reduction. The strength and toughness of La(CrMg)O were measured from 25° to 1000C in the as‐fired reduced state and after oxidation. The as‐fired samples showed a peak in toughness of approximately 3.9 MPa.m at 125C which decreased to approximately 1.4 MPa.m at 600C and 2.8 MPa.m at room temperature. This peak in toughness is hypothesized to be due to the rhombohedral‐to‐orthorhombic phase transition by a toughening mechanism that is currently being investigated. The strength was also affected by the phase transition for both the as‐fired reduced and the oxidized samples