Cation tracer diffusion in La1−xSrxFeO3−δ, (x = 0 or 0.1) at 1173 to 1373K was investigated by means of secondary ion mass spectrometry for both A-site and B-site diffusion; using Y3+and Cr3+ as tracer ions. The B-site impurity (represented by Cr) diffusion was found to be faster than A-site impurity (represented by Y) diffusion for LaFeO3 over the entire temperature range, and for La0.9Sr0.1FeO3 at temperatures less than 1273K. The activation energies for bulk diffusion in La0.9Sr0.1FeO3−δ were 168kJ/mol for Y, and 150kJ/mol for Cr. These values were significantly lower than those reported for diffusion couple experiments. The large difference in the activation energies was explained in terms of the difference in cation vacancy populations between the 2 experimental techniques. The diffusion coefficients were also clearly affected by a first-order phase transition, at about 1263K, in pure LaFeO3. The grain boundary diffusion coefficients were some 5 orders of magnitude higher than the bulk diffusion coefficients; with an activation energy of 128kJ/mol.

Cation Diffusion in La1−xSrxFeO3−δ, x = 0 and 0.1 Measured by SIMS. I.Wærnhus, N.Sakai, H.Yokokawa, T.Grande, M.A.Einarsrud, K.Wiik: Solid State Ionics, 2007, 178[13-14], 907-14