Cation self-diffusion in LaFeO3 measured by the solid state reaction method

Cation diffusion in LaFeO3 has been studied using the solid state reaction between sintered bodies of La2O3 and Fe2O3 at 950–1350 °C in air or O2–N2 mixtures. LaFeO3 was the only product formed. The growth was parabolic and demonstrated to take place predominantly by diffusion of Fe3+ through the LaFeO3 layer. The self-diffusion coefficient of Fe3+ was accordingly calculated from the parabolic rate constant, and at constant activity of La2O3, aLa2O3 = 1, it shows Arrhenius-type behaviour with activation energy 320 ± 20 kJ/mol. It appeared to be independent of the surrounding pO2, but this was ascribed to lack of equilibrium with the atmosphere during growth of the LaFeO3 layer. Correspondingly, the product LaFeO3 is probably stoichiometric, and differences between our diffusivity and activation energy and those in the literature are discussed in view of this.