= 2.3 to 3.2, y = 1.2 to 2.0, z = 0.3 to 0.9) demonstrated that above ca. 46% of B-site magnetic cations, the m = 5 structure first rearranges into a mixed-phase material based on m = 5 and sixlayered (m = 6) structures and eventually evolves into an m = 6 phase with 54% magnetic cations at the B-site. It is postulated that increasing the number of perovskite layers by forming the m = 6 structure facilitates the accommodation of additional magnetic cations at a lower average manganese oxidation state (+3.3) compared with an equivalent m = 5 stoichiometry (+4.0). While the minor out-of-plane ferroelectric response decreases as expected with increasing structural reorganization towards the m = 6 phase, the predominant in-plane piezoresponse remains unaffected by magnetic cation substitution. This work shows that higher-layered Aurivillius homologues can be synthesized using aliovalent substitution, without requiring epitaxial growth or kinetically constrained methods.