Cation diffusion in La 1− xSr xFeO 3− δ, x = 0 and 0.1 measured by SIMS

Abstract

Cation tracer diffusion coefficients in La 1− x Sr x FeO 3− 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 Y 3+and Cr 3+as tracer ions. B-site impurity (represented by Cr) diffusion was found to be faster than A-site impurity (represented by Y) diffusion for LaFeO 3 in the whole temperature interval investigated and for La 0.9Sr 0.1FeO 3 at temperatures less than 1273 K. The obtained activation energies for bulk diffusion in La 0.9Sr 0.1FeO 3− 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 LaFeO 3. 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.