Oxygen nonstoichiometry and transport properties of strontium substituted lanthanum ferrite

This study presents an investigation of the properties of (La_0.6Sr_0.4)_0.99FeO_3-δ (LSF40) covering thermomechanical properties, oxygen nonstoichiometry and electronic and ionic conductivity. Finally, oxygen permeation experiments have been carried out and the oxygen flux has been determined as a function of temperature and driving force.The electrical conductivity was measured using a 4 probe method. It is shown that the electrical conductivity is a function of the charge carrier concentration only. The electron hole mobility is found to decrease with increasing charge carrier concentration in agreement with recent literature.Values of the chemical diffusion coefficient, D_Chem, and the surface exchange coefficient, k_Ex, have been determined using electrical conductivity relaxation. At D_Chem is determined to be with an activation energy of . The surface exchange coefficient is found to decrease with decreasing oxygen partial pressure.Oxygen permeation experiments were carried out. The flux through a membrane placed between air and wet hydrogen/nitrogen was (corresponding to an equivalent electrical current density of ). The oxygen permeation measurements are successfully interpreted based on the oxygen nonstoichiometry data and the determined transport parameters.