In the system BaFe 1− x Ru x O 3− y three phases, separated by immiscibility gaps, are present: an Fe-rich phase ( x = 0-0.75) with hexagonal BaTiO 3 structure (6H; sequence (hcc) 2), a Ru-rich phase ( x = 0.9) of hexagonal 4H type (sequence (hc) 2), and the pure Ru compound BaRuO 3 with rhombohedral 9R structure (sequence (hhc) 3). By vibrational spectroscopic investigations in the 6H phase a transition from n-type semiconduction (Fe-rich oxygen-deficient compounds) to good, metal-like conduction (Ru-rich compounds with complete oxygen lattice) can be detected. The 4H and 9R stacking polytypes are good, metal-like conductors.