The successful integration of high temperature electrochemical devices in the future energy economy based on renewable sources strongly depends on the development of new materials, such as good ceramic electronic conductors. Recently we measured very high electronic conductivity in a perovskite system developed in our group (La0.4Sr0.4GaxTi1-xO3-x/2-δ, x<0.15), as part of the SUPERGEN XIV ¿ ¿Delivery of Sustainable Hydrogen¿ project.We would like to make use of the high resolution of neutron powder diffraction in order to address three key aspects regarding the structure of these materials: to identify slight distortions of the cubic lattice that are not visible via X-ray diffraction; to acquire accurate information regarding the oxygen sub-lattice; to find weather there is any cation-vacancy ordering on the A-site of the perovskite lattice.