Oxide ion conductors are researched as electrolytes in solid oxide fuel cells. Yttria-stabilized zirconia is the currently used electrolyte in SOFCs, leading to high operating temperatures of 800-1000 °C, precluding their wider use. Ba3MoNbO8.5 adopts a novel structure, a hybrid of the 9R perovskite polytype and the palmierite structure. It is a pure oxide ion conductor with sigma= 2.2 × 10-3 S cm-1 at 600 °C. Our research on new oxide ion conductors, based in part on using neutron scattering and computational modelling, has resulted in new insight into the structure-dynamics-property relationships in some of the leading fluorite, apatite and melilite-type ionic conductors. We request 5 days of IRIS and 2 days of MERLIN beam time to carry out the first inelastic/quasi-elastic neutron scattering experiments on the new hexagonal perovskite based oxide ion conductor Ba3MoNbO8.5.