On the grain boundary diffusion of Co in NiO bicrystals

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Abstract
Grain-boundary diffusion of cobalt has been studied in ⟨001⟩ and ⟨011⟩ symmetrical tilt NiO bicrystals. No preferential intergranular diffusion was observed despite the fact that the diffusion parameters (temperature and time) were optimized from published data obtained on polycrystalline NiO samples. The origin of this contradictory result is discussed in terms of experimental protocol, analysis technique, impurity content and origin of the material. Taking into account the sensitivity and the resolution of the electron microprobe analysis technique, we show that the intergranular diffusion coefficient D' is less than 103D, where D is the lattice diffusion coefficient, and is not of the order of 105D as previously published.