The impact of Ba substitution on high-temperature transport in lanthanum-strontium ferrite

Abstract

Effect of barium content on structural, thermal, and transport properties of oxides La0.49Sr0.5–x Ba x FeO3–δ (х = 0, 0.25, 0.50) was studied with the emphasis on their potential use for electrodes and oxygen transport membranes. Barium substitution for strontium was found to enhance symmetry of crystalline lattice, facilitate the oxygen release on heating, and favor the increasing thermal expansion of La0.49Sr0.5–x Ba x FeO3–δ . Analysis of electrical conductivity depending on the partial oxygen pressure allowed to separate the contributions of oxygen ions, electrons, and holes in high-temperature electrical transport in order to trace barium effect on conductivity components. Electron conductivity of n-type and its activation energy does not reveal sensitivity to barium concentration in oxides. Oxygen ion conductivity is shown to decrease with increasing barium content in La0.49Sr0.5–x Ba x FeO3–δ while respective activation energy increases from 0.70 to 0.79 eV. About four times decrease of p-type electron conductivity at invariable activation energy was detected as a result of the substitution degree increase from x = 0 to x = 0.5. Possible mechanisms of barium influence on properties of oxides are discussed.