In situ hydration study of the novel ionic conductor Ba7MoNb4O20

Oxide-ion and proton-conducting materials attract considerable interest thanks to their application as electrolytes in solid-oxide fuel cells (SOFCs). We have recently identified remarkable oxide ion and proton conductivity in Ba7MoNb4O20, a 7H hexagonal perovskite derivative. Ba7MoNb4O20 presents a complex structure, with positional oxygen disorder along palmierite-like layers leading to mixed coordination of the Mo/Nb cations. Via neutron diffraction measurements under controlled temperature and atmosphere, we aim to investigate in more detail the structural features of Ba7MoNb4O20 and study the hydration process in situ, in order to locate the possible proton sites and the ionic migration pathways within the crystal lattice. This study will help to understand the mechanism of oxide-ion and proton diffusion in this fascinating novel conductor.