Structural Evolution and Multiferroics in Sr‐Doped Bi₇Fe_1.5Co_1.5Ti₃O₂₁ Ceramics

Abstract

The ceramics with the composition of Sr x Bi 7x Fe 1.5 Co 1.5 Ti 3 O 21d (0 ≤ x ≤ 1, SBFCT) were prepared by a citratenitrate combustion method, and the phase evolution with an increasing Sr content was investigated. Pure Aurivillius phase SBFCT with a layer number of n = 6 was obtained when x ≤ 0.25, and then the structure collapsed to 5 layers for x = 0.50, then alternating 4 and 5 layers for x = 0.75, and finally 4 layers for x = 1.00. Meanwhile, secondary phase Sr 1m Bi m Fe 1i Co i O 3c appeared when x > 0.25, which is antiferromagnetic (AFM) and with low resistivity. Enhanced ferromagnetic and ferroelectric properties were observed from single phase SBFCTs at the room temperature, and the ferromagnetic transition temperature (T c ) increases with the Sr doping level x in the single phase range. The remnant magnetization (2M r ) is 2.27 emu/g and the remnant polarization (2P r ) is 2.89 lC/cm 2 at an applied electric field of 100 kV/cm for the x = 0.25 sample.X. Tan-contributing editor Manuscript No. 35940.

Structure Evolution and Multiferroic Properties in Cobalt Doped Bi4NdTi3Fe1-xCoxO15-Bi3NdTi2Fe1-xCoxO12-δ Intergrowth Aurivillius Compounds

“…The HAADF results indicate that increasing Co doping level makes the BNTFC- x compound experiencing a structure evolution from 4-layered structure to 3-layered structure. This intergrowth phenomenon has also been reported in Sr x Bi 7- x Fe 1.5 Co 1.5 Ti 3 O 21- δ , which undergoes a phase evolution from 6-layers to 4-layers when the concentration of A-site doped strontium increases from 0 to 114.…”

“…The fraction of the Bi 12 TiO 20 phase increases with the Co concentration in the samples with x  < 0.5, and keeps at about 15% for x  ≥ 0.5. The impurity phase (Bi 12 TiO 20 ) is induced by the element loss during the structure evolution process, similar to the situation in Sr x Bi 7- x Fe 1.5 Co 1.5 Ti 3 O 21- δ system14. According to the results of XRD patterns and HAADF images, the BNTFC- x compounds undergo a structure evolution with a two-phase modulated superlattice when the concentration of Co changes.…”

“…The overall chemical composition is thus Bi 2 A n −1 B n O 3 n +3 , where many different cations can be incorporated on the A and B sites within the perovskite-like layers11. The series of Aurivillius phase compounds are well known for their excellent ferroelectric properties with very low fatigue12, and offer great potential for tailoring specific properties by varying different ionic compositions or even number of layers81314. By doping with magnetic cations, the bismuth-based Aurivillius phase compounds were found to have a room temperature ferromagnetic order besides the natural ferroelectricity, indicating their multiferroic potential89151617.…”

On Structure, Optical Properties and Photodegradated Ability of Aurivillius‐Type Bi3TiNbO9 Nanoparticles

“…The highly anisotropic crystal structure induces a strong polar response, which is the origin for its ferroelectric property. So far, Aurivillius materials have been developed in rich applications such as photoelectricity, electronic, electromechanical field; especially the tunable microwave devices and systems based on Aurivillius materials have been widely reported …”

Extended Near-Infrared Photoactivity of Bi6Fe1.9Co0.1Ti3O18 by Upconversion Nanoparticles

“…Recently, layered bismuth-based Bi 4 Bi n −3 Fe n −3− x Co x Ti 3 O 3 n +3 (BFCTO) Aurivillius compounds, which are formed by perovskite-type (Bi n −1 Fe n −3− x Co x Ti 3 O 3 n +1 ) 2− blocks sandwiched between fluorite-type (Bi 2 O 2 ) 2+ slabs, where n is the number of perovskite units per half-cell [18,19,20,21], proved to be apotential single-phase multiferroic material with ferroelectricity and ferromagnetism [22]. Moreover, the internal electric field and ferromagnetism could enable the photocatalysts recyclable in viscous solution, which is important but extremely difficult due to their size and high viscosity [23].…”