A series of Aurivillius phase materials, Bi5Ti 3 - 2x Fe 1 + x NbxO15 ( [Formula: see text], 0.1, 0.2, 0.3, and 0.4), was fabricated by chemical solution deposition. The effects of aliovalent substitution for the successful inclusion of Fe 3+ and Nb 5+ by replacing Ti 4+ were explored as a potential mechanism for increasing magnetic ion content within the material. The structural, optical, piezoelectric, and magnetic properties of the materials were investigated. It was found that a limit of x = 0.1 was achieved before the appearance of secondary phases as determined by the X-ray diffraction. Absorption in the visible region increased with increasing values of x corresponding to the transition from the valence band to the conduction band of the Fe- [Formula: see text] energy level. Piezoresponse force microscopy measurements demonstrated that the lateral piezoelectric response increased with increasing values of x . Magnetic measurements of Bi5Ti2.8Fe1.1Nb0.1O15 exhibited a weak ferromagnetic response at 2, 150, and 300 K of 2.2, 1.6, and 1.5 emu/cm3 with Hc of ∼ 40 , 36, and 34 Oe, respectively. The remanent magnetization MR of this sample was found to be higher than the range of reported values for the Bi5Ti3Fe1O15 parent phase. Elemental analysis of this sample by energy-dispersive X-ray analysis did not provide any evidence for the presence of iron-rich secondary phases. However, it is noted that a series of measurements at varying sample volumes and instrument resolutions is still required in order to put a defined confidence level on the Bi5Ti2.8Fe1.1Nb0.1O15 material being a single-phase multiferroic.