Mechanochemistry of fluoride solids: from mechanical activation to mechanically stimulated synthesis

F anion transport in nanocrystalline SmF3 and in mechanosynthesized, vacancy-rich Sm1—x BaxF3—x

Nanostructured materials can show considerably different properties as compared to their coarse-grained counterparts. Especially prepared by high-energy ball milling they are to be characterized by a large fraction of point defects in the bulk and structurally disordered interfacial regions. Here, we explored how the overall conductivity of SmF3 can be enhanced by mechanical treatment and to which degree aliovalent substitution is able to further enhance anion transport. For this purpose nanocrystalline (hexagonal) SmF3 was prepared by high-energy ball milling; mechanosynthesis helped us to replace Sm3+ in SmF3 by Ba2+ and to create vacancies in the F anion sublattice. We observed a remarkable increase in total (direct current) conductivity when going from nano-SmF3 to Sm1−x Ba x F3−x for x = 0.1. Electrical modulus spectroscopy was used to further characterize the corresponding increase in electrical relaxation frequencies.