These symmetry-lowering distortions are quite usual where two cations of very different size occupy the two different octahedral sites of the 6H-structure. In our case, the distortion of the octahedra as the Fe (III) increases, and therefore the oxygen content decreases, could be at the origin of the observed transition phase from hexagonal to orthorhombic. Furthermore, following the above reasoning, we can establish that the hexagonal phase is stable if the Fe2 site is mostly occupied by Fe (IV), i.e., in the compositional range between BaFeO3 to near BaFeO2.83. For lower oxygen contents, the orthorhombic phase is stabilized.