In Series 4 (Bi6TixFeyMnzO18 (x = 2.3 to 2.8, y = 1.52 to 2.00, z = 0.68 to 0.75)), the concentration of Ti was further reduced. The compositions were selected based on a compositional survey of 55 individual Aurivillius phase grains from a previous study of a mixed m phase B6TFMO sample. This series explores aliovalent substitution of Ti by both Mn and Ti, allowing