TOPICAL DAY - Ionic diffusion mechanisms investigated through lattice and vibrational dynamics, the cases of the oxide-ion conductor Nd2NiO4+d, and BaZrO3-based proton conductors

Orateur : A. PERRICHON (Chalmers University of Technology, Göteborg, Sweden)

Materials showing high ionic conductivity in the intermediate temperature range (T = 100 – 500 °C), to be used as electrolytes in solid oxide fuel cells (SOFC), have been heavily studied over the past decade. However, understanding ion conduction mechanisms on the atomic scale remains a fundamental problem, especially in a temperature regime where lattice dynamics are expected to play a major role on the diffusion process. Through examples on our work on the oxide-ion conducting material, Nd2NiO4+d,[1–2] and the proton conducting oxides, BaZr0.5In0.5O3H0.5[3] and Ba2In2O5(H2O)x,[4–5], all derived from the well-studied perovskite structure, we emphasize the insights that can be obtained by studying both the lattice (coherent) and vibrational (incoherent) dynamics using inelastic neutron scattering (INS) and by ab initio molecular dynamics simulations (AIMD). In particular we discuss the non-trivial relationships between local structures, single-particle and lattice-assisted dynamical motions, and diffusion events. Furthermore, we show the advantages that can be obtained using ‘unconventional’ techniques, such as the study of incoherent inelastic scattering on a single-crystal of Nd2NiO4.25 using IN8, and the post analyzes of the AIMD trajectories with the positional recurrence map code (PRM) that we developed.

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