Compositional Tuning of the Aurivillius Phase Material Bi5Ti3−2xFe1+xNbxO15 (0 ≤ x ≤ 0.4) Grown by Chemical Solution Deposition and its Influence on the Structural, Magnetic, and Optical Properties of the Material

A series of Aurivillius phase materials,Bi
₅
Ti
_3-2x
Fe
_1+x
NbxO
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
_3-2x
Fe
_1+x
NbxO
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 levelon the Bi
₅
Ti
_2.8
Fe
_1.1
Nb
_0.1
O
₁₅
material being a single-phase multiferroic.