Abstract:
A series of Aurivillius phase materials, Bi 5 Ti 3−2x Fe 1+x Nb x O 15 ( x=0 , 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- eg energy level. Piezoresponse force microscopy measurements demonstrated that the lateral piezoelectric response increased with increasing values of x . Magnetic measurements of Bi 5 Ti 2.8 Fe 1.1 Nb 0.1 O 15 exhibited a weak ferromagnetic response at 2, 150, and 300 K of 2.2, 1.6, and 1.5 emu/cm 3 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 Bi 5 Ti 3 Fe 1 O 15 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 Bi 5 Ti 2.8 Fe 1.1 Nb 0.1 O 15 material being a single-phase multiferroic.
