We propose to study by total neutron scattering the structures of some complex oxide materials prepared by new hydrothermal routes in order to construct structural models consistent with other structural studies. The materials are fluorites and pyrochlores with useful properties such as oxide-ion conduction, redox catalysis and magnetism, which must be explained by a full structural study. Detailed structural models which include the possibility of local disorder are also needed to rationalise the synthesis methods used to allow some predictability in future synthesis. This follows from our recent, published work using GEM to study the structures of disordered materials.