Pure Bismuth Ferrite Research Articles

Significant enhancement of piezoelectric photocatalytic activity in Mn-doped BiFeO3

Ultrasonic vibration and light irradiation can be used together to slow down the rapid recombination of light-induced charges during the catalytic process. One way to enhance the catalytic performance is by introducing different elements into the structure. In this study, pure bismuth ferrite (BiFeO3) and manganese (Mn)-doped bismuth ferrite (BFMO) nanomaterials were successfully synthesized by electrostatic spinning. These materials were then tested for their ability to degrade rhodamine B (RhB). The best-performing material was BiFe0.85Mn0.15O3, which achieved almost complete removal of RhB within 100 min. The degradation rate of this material was 3.3 times higher than that of pristine BiFeO3. This enhanced catalytic activity can be attributed to the wider range of light absorption and the synergistic enhancement of the piezoelectric response, which promotes the movement of free carriers. In addition, the synthesized catalysts have good stability and reusability, with little metal leaching after multiple uses. Free radical scavenging experiments tests showed that ·OH and holes are the main active species in the catalytic process. This work paves a new approach for creating highly efficient piezoelectric catalysts and expands the application of BiFeO3-based materials for wastewater purification.

Visible light-induced photocatalytic degradation of methylene blue dye using pure phase bismuth ferrite nanoparticles

The degradation of organic dyes in wastewater has become a significant environmental issue, requiring the development of degradation technologies that are both effective and environmentally friendly. The present study employed the sol-gel approach to synthesize nanoparticles of phase pure bismuth ferrite (BiFeO3). The nanoparticles were assessed for their ability to efficiently degrade methylene blue (MB) dye, especially under visible light irradiation. The X-ray diffractogram (XRD) confirmed the formation of BiFeO3 nanoparticles, with an average crystallite size of 48 nm. The material's band gap, with a value of 1.84 eV, demonstrates its capacity to effectively absorb light, including wavelengths within the visible spectrum. Scanning electron microscopy (SEM) was used to identify porous aggregated particles. Both Raman and Fourier transform infrared spectroscopy (FTIR) confirm the successful synthesis of pure BiFeO3 in the desired phase. The BiFeO3 photocatalyst exhibited a significant surface area and isotherms of type IV, a characteristic typically observed in mesoporous materials, as determined by the Brunauer-Emmett-Teller (BET) analysis. The efficacy of BiFeO3 nanoparticles in facilitating the decomposition of MB in a water-based solution was evaluated by visible light photocatalysis. An efficiency degradation of 98.49 % was recorded for MB within 2 h.

Crystal structure and magnetic properties ferrites Ba-Fe-O, Bi-Fe-O, synthesized in NGO “Physics-Sun”

Alloys based on Ba-Fe-O have been synthesized in a large solar furnace NGO “Physics-Sun”. The obtained barium hex ferrite with magnetic characteristics suitable for solving technical problems for the manufacture of protective coatings. The experimentally observed increase in the specific magnetization of BiFe0.75Ni0.25O3 with respect to the data obtained in nominally pure bismuth ferrite is associated both with the suppression of the cycloidal spin structure due to the partial substitution of nickel cations for iron cations and with the establishment of ferromagnetic exchange interaction between neighboring Fe3+ and Ni3+ ions. The results of ab initio (LSDA + U approximation of the DFT method) calculations of the band structure suggest that in the ground state BiFe0.75Ni0.25O3 is a semiconductor with a band gap of 1.94 eV.

Defects characteristic investigation of bismuth ferrite nanocrystallites through positron annihilation and supportive methods

Phase pure bismuth ferrite (BFO) nanocrystallites were synthesized by sol-gel method. The variation in the time of calcination at 600 °C is used as the parameter to vary the sizes of the nanocrystallites. X-ray diffraction and electron microscopic studies revealed the formation of BFO nanocrystallites of well-defined sizes and morphology. The elemental stoichiometric compositions of the samples were verified using energy dispersive analysis of X-rays and further by X-ray photoelectron spectroscopy. The UV–visible diffuse reflectance spectra showed strong absorption at the wavelength ∼556 nm (2.23 eV) for BFO nanocrystallites of dimensions 20 nm. For nanocrystallites of sizes smaller than this limit, the band gap energies showed remarkable increase due to the onset of quantum confinement effects. The band gap energies showed increase at larger crystallites sizes as well, indicating defects formation due to oxygen deficiencies. Positron annihilation spectroscopy is used to characterize and monitor the defects. The formation of Bi3+-O2- divacancies significantly altered the positron annihilation characteristics at larger crystallite sizes.

Structural and magnetic quantification of rhombohedral – Orthorhombic phase transition in gadolinium substituted bismuth ferrite

Room-temperature X-ray diffraction (XRD), and High-resolution transmission microscopy (HR-TEM) were used to investigate the structural properties of multiferroic Bi1-xGdxFeO3 perovskites, (x = 0.00, 0.05, 0.10, 0.15, 0.20, 0.25 and 0.30). The system under investigation was synthesized through a citric acid-based auto-combustion technique. XRD analysis revealed that the pure bismuth ferrite and the gadolinium substituted bismuth ferrite up to x = 0.10 samples composed of a polycrystalline rhombohedral structure (space group R3c (161)), the samples with Gd concentration between x = 0.15 and x = 0.25 show coexistence of rhombohedral and orthorhombic phases. At the same time, Bi0.7Gd0.3FeO3 crystallizes in a pure orthorhombic structure (space group Pbnm (62)). The crystallographic parameters and the ratio of the two competed phases were estimated using Rietveld refinement of XRD data. Williamson-Hall model based on the refined XRD data was used to estimate the average crystallite length and the induced lattice strain. Furthermore, TEM and HR-TEM images coincident with the XRD results. Bi1-xGdxFeO3 nanoparticles display coupling interactions between weak ferromagnetism and canted antiferromagnets at room temperature. The magnetic properties were estimated by analyzing the M(H) hysteresis loops collected using a vibrating sample magnetometer (VSM). This study can sustain new strategies for tailoring new smart materials with different fascinating properties.

Photodegradation of methyl orange based on manganese-substituted bismuth ferrite nanoparticles

Herein, a microwave-assisted approach for the synthesis of manganese (II) (Mn2+)-doped bismuth ferrite (BMFO) nanoparticles is presented. Various techniques were used to examine the structure, morphology and electrical characteristics of the as-synthesized BMFO nanoparticles. X-ray diffraction and Raman analysis revealed a rhombohedral distorted perovskite structure with space group R3c. The crystallite size of BMFO was found to be 18.77 nm. Scanning electron microscopy studies of the BMFO nanoparticles showed the highly agglomerated nature of the particles. The ultraviolet diffuse reflectance spectrum of BMFO revealed a bandgap of 1.56 eV, which was smaller than the bandgap of pure bismuth ferrite (2.41 eV). The methyl orange (MO) dye degradation behavior of the synthesized BMFO was examined for a dye sample solution in the presence of solar radiation. After 120 min, irradiation resulted in 81.08% photodegradation of the MO dye. Kinetic studies demonstrated a pseudo-first-order rate mechanism for the photodegradation of the MO dye. The corresponding coefficient of determination R 2 and t 1/2 were 0.92864 and 63.0 min, respectively. Finally, a methodology for the degradation of MO dye using BMFO is proposed.

The Effect of Bi2O3 and Fe2O3 Impurity Phases in BiFeO3 Perovskite Materials on Some Electrical Properties in the Low-Frequency Field

Pure bismuth ferrite (BFO) and BFO with impurity phases (Bi2O3 or Fe2O3) were synthesized by the hydrothermal method. Complex dielectric permittivity (ε) and electrical conductivity (σ) were determined by complex impedance measurements at different frequencies (200 Hz–2 MHz) and temperatures (25–290) °C. The conductivity spectrum of samples, σ(f), complies with Jonscher’s universal law and the presence of impurity phases leads to a decrease in the static conductivity (σDC); this result is correlated with the increased thermal activation energy of the conduction in impure samples compared to the pure BFO sample. The conduction mechanism in BFO and the effect of impurity phases on σ and ε were analyzed considering the variable range hopping model (VRH). Based on the VRH model, the hopping length (Rh), hopping energy (Wh) and the density of states at the Fermi level (N(EF)) were determined for the first time, for these samples. In addition, from ε(T) dependence, a transition in the electronic structure of samples from a semiconductor-like to a conductor-like behavior was highlighted around 465–490 K for all samples. The results obtained are useful to explain the conduction mechanisms from samples of BFO type, offering the possibility to develop a great variety of electrical devices with novel functions.

Modulating light absorption and multiferroic properties of BiFeO3-based ferroelectric films by the introduction of ZnO layer

Pure bismuth ferrite (BiFeO3, BFO) and ZnO thin films, as well as BFO/ZnO and ZnO/BFO composite thin films were successfully deposited by a sol-gel process on Pt/Ti/SiO2/Si and FTO/glass substrates, respectively. The chemical composition, surface morphology, optical properties, and multiferroicity were systematically investigated. X-ray diffraction and electron microscopy measurements were used to determine the crystalline phase and to analyze the surface morphology. Evidently, the absorption edges of both BFO/ZnO and ZnO/BFO films show a redshift, broadening the absorption range. The leakage current density decreases with the introduction of ZnO, and the ferroelectricity was significantly improved of the bilayers. Thereinto, BFO/ZnO and ZnO/BFO show the highest saturate polarization (2P s) of 46.7 μc cm−2 and the maximum remanent polarization (2P r) of 18.5 μc cm−2, respectively. Meanwhile, the magnetization measurement revealed that both BFO/ZnO and ZnO/BFO exhibiting an enhanced magnetization, especially, BFO/ZnO displays the highest saturation magnetization (2M s, 68.87 emu cm−3) and remanent magnetization (2M r, 4.87 emu cm−3).

Influence of sintering temperature on structural, morphological and optical properties of nanocrystalline bismuth ferrite thin films via sol-gel processing

Nanocrystalline thin films of pure bismuth ferrite were synthesized by sol-gel deposition technique on the corning glass substrate. The influence of sintering temperature on microstructure, morphology, and optical parameters has been systematicallystudied. Optimization of sintering temperature for single-phase nanocrystalline bismuth ferrite fabrication was carried out and found to be at 550 °C. X-ray diffraction confirms the presenceof distortedrhombohedral perovskite structure of bismuth ferrite oriented along (hkl) plane of (101).Surface morphology and Root mean square (RMS) surface roughness of the thin films prepared were determined from the micrographs of atomic force microscopy (AFM).Several optical constants viz. bandgap energy, extinction coefficient,Urbach energy, has been determined using Ultraviolet-Visible spectroscopy of the thin films within the range 200 -800 nm. With the increase in sintering temperature, there is a decrease in the optical bandgap of the material which would be essential for the wide range of applications in thin-film solar cells along with optoelectronic devices.

A correlation of lattice distortion with the magnetic properties of calcium doped bismuth ferrite thin films

In this work, Bi1−x Ca x FeO3 (for x = 0.00–0.30) single-phase thin films were developed on clean glass substrates via simple spray pyrolysis technique. The microscopic crystal structure and magnetic characteristics of the Ca modified thin films were investigated. X-ray diffraction study confirms the hexagonal structure with the space group R3c for all the prepared thin film samples. The crystallite sizes and lattice strains were computed by using the Williamson–Hall plot. The morphology of the samples was viewed by field emission scanning electron microscopy which shows that the average size of grains systematically decreases with the addition of Ca atom at Bi site. The compositions of samples were confirmed by using energy dispersive spectroscopy. The structural phase transition and the position of different Raman modes were observed by using the Raman spectroscopy technique. The elementary compositions, different oxidation states, and the effect of oxygen vacancies of the elements were observed by x-ray photoelectron spectroscopy. The magnetic field (H) dependence of magnetization (M) (i.e. M–H hysteresis loops) of the pure bismuth ferrite (BFO) and Ca doped BFO thin film samples conducted at room temperature using a vibrating sample magnetometer with an applied magnetic field of ±30 kOe and confirmed that the value of magnetization significantly increases with Ca addition at Bi-site in BFO atom. The maximum value saturation magnetization of 3.8176 emu g−1 and remanent magnetization of 0.1408 emu g−1 obtained for the 25% Ca doped BFO thin films.

Study of effect of Dy substitution on structural, dielectric, impedance and magnetic properties of bismuth ferrite

This communication mainly reports the synthesis and characterization of dysprosium (Dy)-doped bismuth ferrite [i.e., Bi(Fe0.95Dy0.05)O3 (referred as BFDO5)] compound. A conventional high-temperature solid-state reaction technique has been utilized for synthesizing the material at a temperature of 800 °C. The structural study of the prepared sample, carried out using X-ray diffraction data, reveals the creation of a single-phase compound having an orthorhombic crystal structure. The average crystallite size, obtained from the measurement of high-intensity X-ray diffraction peaks of the BFDO5 material, was found to be 38 nm. The purity of the prepared compound and concentration of its constituent elements were confirmed by energy dispersive X-ray spectroscopy (EDXS) data. The field effect scanning electron microscope (FESEM) image clearly shows the surface morphology and regular distribution of the composite grains over its surface. Detailed analysis of the dielectric and impedance data, measured in a broad range of frequency (1–1000 kHz) and temperature (25–500 °C), has shown a significant improvement in the dielectric and electrical properties of the prepared material. The electrical polarization measurement, done by P–E hysteresis loop tracer, shows the existence and enhancement of ferroelectric property of the material. Room temperature measurement of its magnetization was carried out by using vibrating sample magnetometer that shows a significant enhancement in a remnant magnetization as compared to pure bismuth ferrite.

Increased Low‐Temperature Magnetization and Spin‐Reorientational Transition in the Polar Phase of (Ca, Mn)‐Doped Bismuth Ferrites

Solid‐state synthesis and an investigation of the crystal/magnetic structure and magnetic properties of the Bi1−xCaxFe0.6Mn0.4O3+δ [x = 0.1, 0.15; δ = 0.02(2)] multiferroics have been conducted to explore an approach to designing ferroelectric materials with the enhanced magnetization attributed to the ferromagnetic superexchange involving the Mn 3d states. It is shown that the (Ca, Mn)‐doped samples maintain the polar R3c structure characteristic of the pure bismuth ferrite. For both these compounds, an antiferromagnetic (AFM) G‐type ordering of the Fe/Mn magnetic moments along the hexagonal c‐axis is revealed at room temperature. The reorientation of the magnetic moments from the c‐ to a‐axis occurs as temperature decreases. Being consistent with the competing character of the superexchange between Mn3+, Mn4+, and Fe3+ ions, the coexistence of AFM long‐range‐ordered and superparamagnetic phases underlying the appearance of a significant magnetization in the low‐temperature range is observed.

Magnetic and dielectric characterization of xBiFeO3:(1-x)SrFe12O19 multiferroic composites

Multiferroic composites xBiFeO3:(1-x) SrFe12O19 (0.5 ≤ x ≤ 1, Δx = 0.1) were produced by mixing powders of BiFeO3 and SrFe12O19 obtained by high energy ball milling assisted with heat treatment. To study their multiferroic properties, the ferromagnetic, dielectric and magnetodielectric behavior was evaluated for each composite. The composites were produced using powders of BiFeO3 and SrFe12O19 that were mixed, pressed at 800 MPa, and sintered at 700 °C for 4 h. XRD analysis confirms the presence of both ferroic phases, BiFeO3 and SrFe12O19, and small amounts of the secondary phase, Bi2Fe4O9 (mullite). The quantity of this secondary phase increases with the concentration of strontium hexaferrite. The remanent magnetization values are 17.9 emu/g and 2.54 emu/g for x = 0.5 and x = 0.9, respectively. The coercive field does not change with the composition; it exhibits a nearly constant value of 5.5 kOe for all the samples containing strontium hexaferrite. The addition of strontium hexaferrite produces diminution of the relative permittivity (ξr) and dielectric losses (tan δ). At 5 MHz, the composite with x = 0.9 shows the highest relative permittivity (16.78), and a diminution of dielectric loses of 43.88% due to the higher resistivity of the strontium hexaferrite. The magnetodielectric measurements showed an increase in the relative permittivity of the composites due to a reduction of the resistivity in agreement with the Maxwell-Wagner behavior when a magnetic field was applied. This study show evidence for magnetoresistive behavior by pure bismuth ferrite at room temperature, which has not been previously reported.

Structural Effect of Doping of Calcium Ion on Bismuth Ferrite Thin Films

Structural properties of pure bismuth ferrite and calcium modified Bi(1-x)CaxFeO3 (x = 0.05, 0.10, 0.15, 0.20 and 0.30) thin films were successfully synthesized on pre cleaned glass substrates by using a simple spray pyrolysis method. The samples were prepared at 450°C and sintered at temperature 550°C for 2h in air atmosphere. The structure and morphology of the samples were studied by X-ray diffraction (XRD). The reitveld refinement of X-ray diffraction predicts the distorted rhombohedral perovskite structure with space group R3c.

BiFeO3-synthesis, characterization and its photocatalytic activity towards doxorubicin degradation from water

Pure bismuth ferrite was successfully obtained through the thermolysis of new bismuth ferrioxalate coordination compound, namely BiFe(C2O4)3·3H2O. The synthesized precursor was characterized by chemical analysis, infrared spectroscopy and thermal analysis. The bismuth ferrite obtained after a heating treatment of the precursor for at 450–800 °C/1 h was investigated by X-ray diffraction, FE-SEM, TEM and HRTEM. The obtained pure bismuth ferrite nanoparticles (480 °C) was tested as photocatalyst towards the degradation of doxorubicin (DOX), a well-known anti-cancer drug commonly used for the treatment of various cancer types, which has been detected in hospital effluent water. The comparative results of DOX degradation through photolysis and photocatalysis under UV irradiation showed a great photocatalytic activity of bismuth ferrite towards DOX degradation and mineralization from water. The kinetics aspects were discussed based on the first-order kinetics model that fitted the best the experimental photocatalysis results.

X-Ray Diffraction and Mössbauer Studies of the Structural Features of BiFe1 ‒ xZnxO3 Multiferroics

The structure of ceramic BiFe1‒xZnxO3 multiferroic samples is investigated using the X-ray diffraction method and Mossbauer spectroscopy. X-ray diffraction analysis of the samples indicates the existence of the Bi12(Bi0.5Fe0.5)O19.5 impurity phase. High-temperature heating of the samples generates additional phases. The parameters of the Mossbauer spectra depend on the zinc concentration. In this case, for pure bismuth ferrite, the spectrum is a superposition between two Zeeman sextets and two paramagnetic doublets arising from two nonequivalent magnetic and electrical positions occupied by iron ions at the crystallattice sites of a sample. The replacement of iron ions with zinc ions substantially affects the spectrum parameters. This is probably related to changes in the spin-cycloid structure typical of multiferroics, the destruction of which stimulates the appearance of significant magnetoelectric interactions.

Fast synthesis of rare-earth (Pr3+, Sm3+, Eu3+ and Gd3+) doped bismuth ferrite powders with enhanced magnetic properties

Rare-earth (Pr3+, Sm3+, Eu3+ and Gd3+) doped bismuth ferrite powders were synthesized for the first time by solution combustion method, which is a fast soft chemistry route for obtaining oxide powders. The materials were investigated by X-ray diffraction, Raman spectroscopy, as well as scanning and transmission electron microscopy. A distortion from rhombohedral R3c symmetry, specific to pure bismuth ferrite, to orthorhombic symmetry was observed for all doped samples. The SEM analysis of pure and doped bismuth ferrite powders showed the formation of sintered grains, with faceted cuboids-shaped particles with different size and lower average dimension in the case of doped samples. Magnetic properties were analyzed using SQUID magnetometry, M–H hysteresis loops being measured at 10K and 300K. All studied pure and doped bismuth ferrite samples presented high susceptibility values for high magnetic fields indicating strong antiferromagnetic interactions, whereas the behavior at low magnetic field demonstrates the existence of ferromagnetic coupling.Compared to BiFeO3, Bi0.9RE0.1FeO3 (RE=Pr, Sm, Eu and Gd) powders exhibit higher susceptibility, remanence and coercivity values, Bi0.9Eu0.1FeO3 sample displaying the highest remanence and coercivity at room temperature.

Chemical solution deposition derived (001)-oriented epitaxial BiFeO3 thin films with robust ferroelectric properties using stoichiometric precursors (invited)

Phase pure bismuth ferrite (BiFeO3) thin films with (001)-oriented epitaxial structure are realized on lanthanum strontium manganite (La0.67Sr0.33MnO3) buffered (001)-SrTiO3 substrates by chemical solution deposition. The annealing process is optimized such that a stoichiometric precursor can be used to accurately control the Bi:Fe ratio. Ferroelectric, dielectric, and resistive switching behaviours are investigated for 40 nm, 70 nm, and 150 nm BFO thin films. While the thinnest film (40 nm) shows very leaky loops, square and fully saturated polarization hysteresis loops are shown for the thicker films. The highest remanent polarization (2Pr = 100 μC/cm2) and relative dielectric constant (εr = 613) are obtained in the 150 nm BFO thin film. High cycle fatigue tests show that the thick films are resistant to polarization fatigue. Piezoresponse force microscopy results show that the domain structure varies with thickness. Resistive switching and polarization mediated diode effects are also observed. These robust properties suggest that chemical solution deposition derived BiFeO3 thin films can offer a viable low cost alternative.

Sono-synthesis of bismuth ferrite nanoparticles with high photocatalytic activity in degradation of Rhodamine B under solar light irradiation

In this work, pure bismuth ferrite (BiFeO3) as a visible-light photocatalyst has successfully synthesized via ultrasonic method in a short time and low temperature. The product was characterized by different techniques. Then, the degradation of Rhodamine B (RhB) was investigated under sunlight irradiation by bismuth ferrites synthesized with ultrasound. The RhB in solution was completely degraded in 35min under applied conditions in acidic medium. The nanocatalyst did not exhibit significant loss of activity even after four cycles of successive uses. The total organic carbon (TOC) measurements displayed a complete mineralization in 90min. To determine the mechanism of photocatalytic degradation of RhB, different methods were used. Based on the results, two possible competitive photodegradation pathways proposed: chromophores cleavage and N-deethylation. The hole as a reactive species had a key role in the degradation process. The BiFeO3 (BFO) nanoparticles synthesized with ultrasound exhibited higher crystallization, smaller crystallite size and a higher photocatalytic activity than the sample synthesized with sol–gel method in stricter conditions.

Optical and photoluminescence properties of BiFeO3 thin films grown on ITO‐coated glass substrates by chemical solution deposition

AbstractThe optical and photoluminescence properties of the pure bismuth ferrite (BiFeO3) thin films deposited on ITO‐coated glass substrates by chemical solution deposition methods were investigated. The optical bandgap of obtained BiFeO3 thin films annealed at 500 and 600 °C were confirmed to be 2.75 and 2.71 eV, respectively. The dependence of bandgap on annealing was discussed in terms of coarsening grain sizes as well as the existence of amorphous phases in the films. Furthermore, the evident photoluminescence of BiFeO3 thin films is observed. The near‐band‐edge emission located at 455.4 and 457.9 nm were identified for BiFeO3 thin films annealed at 500 and 600 °C, respectively, while the identical defect emission at 468.7 and 492.3 nm were confirmed for both BiFeO3 thin films, which were tentatively attributed to the defect states related with Bi3+ level and oxygen deficiencies inside the bandgap. However, more investigations are needed to classify the origin of BiFeO3 thin‐film emission for further application.