The CaTiO3 based perovskites exhibit mixed oxide-ion and electronic conductivity and have potential for use in ceramic membrane reactors. To bring the membranes closer to utilization it is necessary to increase the oxide-ion conductivity. The ion conduction is mainly governed by the concentration and mobility of oxygen vacancies, and it is thus of crucial importance to gain insight to the structural properties of the materials. The goal of the proposed experiment is to gain insight to details of the structure with respect to oxygen coordination and vacancy ordering in a series of Ca(Ti,FeMn)O3 perovskites with different stoichiometry from neutron scattering experiments using the pair distribution function (PDF) method. The results will be combined with already obtained in-situ synchrotron X-ray diffraction data.