Cation diffusion in La1−xSrxFeO3−δ, x = 0 and 0.1 measured by SIMS

Cation tracer diffusion coefficients in La1−xSrxFeO3−δ, (x = 0 and 0.1) at temperatures ranging from 1173 to 1373 K have been investigated by secondary ion mass spectrometry (SIMS) for both A-site and B-site diffusion applying Y3+and Cr3+as tracer ions. B-site impurity (represented by Cr) diffusion was found to be faster than A-site impurity (represented by Y) diffusion for LaFeO3 in the whole temperature interval investigated and for La0.9Sr0.1FeO3 at temperatures less than 1273 K. The obtained activation energies for bulk diffusion in La0.9Sr0.1FeO3−δ were 168 ± 24 kJ/mol for the Y tracer and 150 ± 30 kJ/mol for the Cr tracer, which are significantly lower than activation energies reported from diffusion couple experiments. The large variation in reported activation energies can be explained in terms of the difference in cation vacancy populations between the two experimental techniques. The diffusion coefficients were also clearly affected by a first order phase transition at approx. 1263 K in pure LaFeO3. The obtained grain boundary diffusion coefficients were about five order of magnitude higher than the bulk diffusion coefficients, with an activation energy of 128 ± 28 kJ/mol.