BiFeO3 Samples Research Articles

Photoelectroreduction CO2 to Ethanol Over BiFeO3 with Synergistic Effect of Self‐Polarization and External Electric Field

The exploitation of semiconductor self‐polarization is an effective mean of improving the efficiency of electron utilization. In this work, the synthesis of BiFeO3 (BFO) samples with varying photoelectric properties is achieved by modulating the concentration of KOH. The experimental results reveal that BFO‐4 (4 m KOH) has excellent carrier efficiency. Interestingly enough, the ethanol yield of up to 7.05 μmol cm−2 h−1 in the photoelectrocatalytic process, which is 1.4 times than that of single electrocatalysis. Based on the characterization data, the external electric field forms a multi‐electric field coupling in the BFO (external electric field can enhance the self‐polarization electric field), which enhances charge separation efficiency and facilitates surface reactions, and the CO2 reduction performance is improved. Finally, the free energy in the key step of CC coupling on the surface of BiFeO3 is calculated by DFT. This study offers a valuable reference for the application of ferroelectric materials in the photoelectrocatalytic reduction of CO2 and the design of catalysts for C2+ products.

Hydrothermal Synthesis, Phase Analysis, and Magneto-Electronic Characterizations of Lead-Free Ferroelectric BM2+(Zn, Ca, Mg)T-BFO System.

In this study, lead-free BiM2+(Zn, Ca, Mg)Ti-BiFeO3 ceramics are fabricated under eco-friendly hydrothermal reaction conditions at 250 °C. XRD patterns show that all the synthesized compounds exhibit a phase coexistence of monoclinic and tetragonal perovskite-type structures with a morphotropic phase boundary at x = 0.4, with minimum impurity. The calculated average crystallite/grain size of the samples was close to 50 nm at full width at half-maximum of the main peak. The corresponding bonds of the constituent elements were observed by FTIR analysis, which further supports the formation of the local structure. EDS analyses detect all of the elements, their quantities, and compositional homogeneity. SEM data show agglomerated and nearly spherical morphology with an average particle size of about 128 nm. All synthesized ceramic powders revealed thermal stability with trivial mass loss up to investigated high temperatures (1000 οC). The dielectric constant reached its maximum at 38.7 MHz and finally remained constant after 80 MHz for all nanoceramics. Because of the complementary impact of different compositions, the most effective piezoelectric characteristics of d33 = 136 pCN-1, Pr = 8.6 pCN-1 cm-2, and kp = 11% at 30 °C were attained at x = 0.4 content for 0.4BiCaTi-0.6BiFeO3 ceramic. The measured magnetic hysteresis data (M-H curve) showed a weak ferromagnetic nature with the highest moment of ∼0.23 emu/g for 0.4BiCaTi-0.6BiFeO3, and other samples exhibited negligible ferromagnetic to diamagnetic transition. The optical response study shows that the 0.4BiMgTi-0.6BiFeO3 sample yielded the maximal transmittance (50%), whereas the 0.4BiCaTi-0.6BiFeO3 compound exhibited the highest refractive index. The calculated large band gap shows a high insulating or dielectric nature. Our findings demonstrate that the BiM2+Ti-BiFeO3 system, which was fabricated using a low-temperature hydrothermal technique, is an excellent lead-free piezoelectric and multiferroic nanoceramic.

In situ study on enhanced plastic deformability of Lanthanum-doped Bismuth ferrite processed by flash sintering

BiFeO3 is a promising multiferroic material for versatile device applications due to its co-existence of magnetic (i.e., antiferromagnetic) and ferroelectric ordering at room temperature. While its functional properties have been extensively investigated, the exploration of its mechanical behavior was limited mostly to the thin-film form of BiFeO3. In this work, we conducted in situ micropillar compression experiments to investigate the deformation behavior of La-doped BiFeO3 (La-BFO) samples processed by both conventional and flash sintering methods. The conventionally sintered La-BFO exhibited limited deformability at room temperature and 450 °C. In contrast, the deformability of the flash-sintered La-BFO specimens was substantially improved by nearly 100% at both testing temperatures. Detailed post-mortem studies suggest that preexisting dislocations and wide anti-phase boundaries introduced during flash sintering can toughen flash-sintered La-BFO by easing dislocation migration and ferroelastic domain switching. This study provides a fresh perspective to design an advanced multifunctional system with improved mechanical properties.

Visible-light-induced photodegradation of ofloxacin antibiotic by facile assembled BiFeO3/Bi-modified g-C3N4 heterojunctions

The design and assembly of photocatalytic heterojunctions with high visible-light-response have been considered an effective method for successful photocarrier separation, avoiding recombination, and thus boosting the photoactivities of the semiconductors to remove contaminants quickly and efficiently. In this research, we fabricated BiFeO3 (BiFO) nanoparticles and 5 wt% Bi-modified g-C3N4 (BiCN) separately; and then combined them in different percentages (BiFO wt% = 5–40 %) to achieve efficient and novel nanocomposite heterojunctions for visible-light-induced ofloxacin (OFL) degradation and successfully reduced charge recombination. Different description tests (XRD, FESEM, TEM, EDX, DRS, EIS, PL, N2 adsorption-desorption isotherms, and VSM). Unsurprisingly, BiFO/BiCN (20 wt% BiFO) hybrids endorsed superb photocatalytic activity for OFL degradation. Under visible-light irradiation, 20 wt% BiFO/BiCN photocatalyst degraded 95.5 % of OFL in 1.5 h, which compared to bare BiCN and BiFeO3 samples were approximately 3.2- and 4.5-times improvements. This achievement is ascribed to the boosted visible-light harvesting and the great separation of photoinduced e−/h+ pairs as a result of the creation of direct Z-system heterojunction between BiCN and BiFO semiconductors. According to the trapping experiments, •O2−, •OH, and h+ act to different extents as key reactive species in OFL photodegradation. The photocatalytic degradation of 90.7 % was still reached at the end of the fifth photodegradation round (only 5 % reduction), demonstrating the high durability of synthesized BiFO/BCN heterojunction. This work presented significant insights and solutions for photocatalytically degrading antibiotic-contaminated wastewater.

Impact of (Sm, Sr) Co-Doping at Bi-Site on the Structural, Optical, Multiferroic and Dielectric Properties of Bismuth Ferrite Nanocomposites

A series of samarium (Sm) and strontium (Sr) co-doped BiFeO3 (BFO) and pure BiFeO3 (BFO) nanocomposites were synthesized by thesol-gel auto-combustion method. The X-ray diffraction pattern of the synthesized Sr:Sm BFO nanocomposites shows a rhombohedralperovskite structure. The morphological studies revealed that synthesized Sr:Sm BFO and pure BFO exhibit a regular arrangement ofgrains. The diffuse reflectance spectra (DRS) exhibit the doping of Sr:Sm BFO reduces the optical band gap values of BFO from 2.02 eVto 1.69 eV. It was observed that the prepared Sr:Sm BFO and undoped BFO samples show G-type antiferromagnetic behaviour and thevalues of saturation magnetization (Ms) increased by increasing the Sr:Sm BFO doping concentrations at the A site of BFO lattice. Themagnitude of the dielectric constant (εr) and dielectric loss (tan δ) were increased gradually with applied frequency and by increasingdoping concentration in the BFO matrix. The significant enhancement in the dielectric parameters with increasing Sm and Sr concentrations in BFO results in improved ferromagnetic properties that could be considered a promising candidate for some advanced device applications.

A comparative study on physico-chemical, optical, magnetic and ferroelectric properties of undoped BiFeO3 and Ni-doped BiFeO3 nanoparticles

Undoped BiFeO3 and Ni-doped BiFeO3 nanostructures were synthesised via colloidal gel, followed by a combustion reaction at a processing temperature of 500 °C, for testing their multiferrioic properties. Powder X-ray diffraction studies reveal the rhombohedral perovskite crystal structure for the synthesized pure BiFeO3, whereas Ni-doped BiFeO3 sample shows the formation of the rhombohedral perovskite structure along with the heterogeneous phase contains Fe2O3 and Bi2Fe4O9. The energy band gap (Eg) of Ni-doped BiFeO3 was found to be reduced (1.87 eV) compared to the Eg value (2.02 eV) of undoped BiFeO3, as confirmed by the Tauc plot. The synthesized compounds were tested for their vibrational bands by FT-IR analysis, and strong absorption bands were found at 555 cm−1, which attribute the vibration bonds of Bi-O and Fe-O. The aggregated particles with irregular morphology appeared in the TEM images of the undoped BiFeO3 and the presence of Ni-doped incorporation of BiFeO3. The ferromagnetic and ferroelectric behaviour of the synthesized undoped and Ni-doped BiFeO3materials was noticed in the magnetization vs. magnetic field (M−H) loops and polarization–electric field (P-E) at room temperature. The areas of the hysteresis loop, coercive force, magnetic saturation, saturation polarization, remanent magnetization, and polarization of Ni-doped BiFeO3 were decreased compared to undoped BiFeO3. The investigated Ni-doped BiFeO3 results were elucidated to assess the soft magnetic nature of device applications.

Synthesis of Na0.02Bi0.98FeO3-δ through the standardized preparation of BiFeO3

This research describes the synthesis of the ferroelectric perovskite Na0.02Bi0.98FeO3-δ using a low-cost solid-state method starting from a bismuth ferrite BiFeO3 structure in order to obtain a material with improved properties for photovoltaic applications. The synthesized materials were characterized by X-ray Diffraction (XRD) technique to determine the effective synthesis conditions for six undoped BiFeO3 samples obtained at different calcination temperatures and quantified by Rietveld® refinement of diffraction patterns, finding homogeneous phase formation at 810 °C under laboratory conditions. The effective synthesis temperature allowed obtaining a stable perovskite-type material, doped with Na+ and its structural characterization by XRD showed a structural modification in the unit cell with respect to BiFeO3 due to the incorporation of sodium cation. The binding energies determined by X-ray photoelectron spectroscopy (XPS) confirmed the formation of the main crystalline phase and the insertion of Na+ cations inside perovskite structure. The morphological characterization by scanning electron microscopy (SEM) of the synthesized material showed the formation of two stable morphologies: Bi2Fe4O9 and Na0.02Bi0.98FeO3-δ as the predominant phase. The optical characterization by Raman spectroscopy allowed identifying variations in the vibration modes of the perovskite doped with respect to undoped bismuth ferrite. The variation of the optical bandgap was determined using the Tauc’s equation and the electrical characterization by solid state electrochemical impedance spectroscopy (SS-EIS) demonstrated an increase in electrical conductivity, at room temperature, by the Na+ doped perovskite, proving an optimal behavior for its potential uses as a semiconductor. The results indicate that the current methodology is promising for the low-cost production of Na0.02Bi0.98FeO3-δ type perovskites for photovoltaic applications.

Effect of Gd and Ce Doped BiFeO3 for Photocatalytic Activity

In this current research work deals with the synthesis, characterization and photocatalytic activity of gadolinium (Gd) and cerium (Ce) doped bismuth ferrite oxide BiFeO3 (BFO). All the samples BFO, BGF-1, BGCF-1, BGCF-2 and BGCF-3 were synthesized by sol-gel method. The structural analysis carried out by X-ray diffraction (XRD), surface morphology examined by field emission scanning electron microscopy (FE-SEM) with EDAX and transmission electron microscopy (TEM), the magnetic properties investigated using vibration sample magnetometer (VSM) and their photocatalytic activity was evaluated by Rhodamine B (RhB) dye under visible light irradiation. The results found that the Gd (0.1 wt.%) and Ce doped (0.1 wt.%) BFO showed better photocatalytic activity as compared to BFO and other samples. HIGHLIGHTS An approach rare earth materials Gd & Ce doping in BiFeO3 Photocatalytic activites and Degradation constants well explained with graphs Gd (0.1 wt%) and Ce (0.1 wt%) doped BiFeO3 showed less photodegradation time than pure BiFeO3 & other doping concentrations Bi9Gd0.1Fe0.9Ce0.1O3 has enhanced photocatalytic degradation for Rhodamine B Degradation of Rhodamine B for the sample BFO is about 50 % and for Gd (0.1 wt%) and Ce (0.1 wt%) doped BiFeO3 is very high that is almost 90 % GRAPHICAL ABSTRACT

Synthesis and optical characterization of Sr and Ti doped BiFeO3 multiferroics

Abstract In this work, Sr and Ti doped BiFeO3 (bismuth ferrite) compositions with dopant x = 0.00 and x = 0.10 have been synthesized by conventional solid-state-reaction method. X-ray diffraction patterns of the pure and Sr and Ti modified BiFeO3 samples with x = 0.10 have shown single phase formation. Rietveld refinement of X-ray diffraction data for both the samples has revealed Rhombohedral structural symmetry with R3c space group. Fourier-transform infrared spectroscopy spectra, recorded in the range 1000–400 cm−1 show shift in the position of a broad hump at higher wave number side with x which may be attributed to the stretching of Bi–O and Fe–O bonds due to doping. UV–visible spectra (ultraviolet-visible spectroscopy) in the range 300–800 nm have revealed a slight increase in the band gap with substitution.

Investigation on structural, magnetic and optical properties of Sm–Co Co-substituted BiFeO3 samples

Abstract Sol–gel derived Sm–Co co-substituted BiFeO3 ceramics (Bi1–x SmFe1–x Co x O3 with x = 0.0, 0.01, 0.02 and 0.03; named as BFO, BSFCO-1, BSFCO-2 and BSFCO-3, respectively) were investigated for structural, vibrational, magnetic and optical properties. Distorted perovskite rhombohedral structure with R3c crystal symmetry has been established in X-ray diffraction (XRD) patterns analysis by Rietveld refinement and detailed structural parameters like lattice constants, unit cell volume, bond angles, bond length etc. have been evaluated. Raman spectra further confirmed typical rhombohedral structure of BiFeO3 by exhibiting 13 clear Raman active phonon (9E + 4A) modes along with second order modes in the wave number range 50–1500 cm−1. Fourier Transform Infrared (FTIR) spectra showed the presence of Fe–O and Bi–O bands and the calculated Fe–O bond length was in good agreement with that obtained from Rietveld analysis. Room temperature magnetization versus magnetic field (M–H) measurement using Vibrating Sample Magnetometer (VSM) showed enhancement of ferromagnetic ordering parameters with increasing Sm–Co content in BiFeO3 samples. The maximum magnetization values increased from 0.237 emu g−1 for BFO sample to 1.167 emu g−1 for BSFCO-3 sample along with increase in remnant magnetization values. The optical property of Bi1–x SmFe1–x Co x O3 samples was investigated by estimating the energy band gap using UV–Visible spectroscopy. The calculated values of energy band gap were varied in the range 2.46 eV–1.81 eV indicating tuning of energy band gap with Sm–Co co-substitution in BiFeO3 sample.

Comparative studies by X-ray diffraction, Raman, vibrating sample magnetometer and Mössbauer spectroscopy of pure, Sr doped and Sr, Co co-doped BiFeO3 ceramic synthesized via tartaric acid-assisted technique

Pure BiFeO3 (BFO), Sr-doped Bi0.97Sr0.03FeO3 (BSFO) and Sr, Co co-doped Bi0.97Sr0.03Fe0.8Co0.2O3 (BSFCO) samples have been prepared via a tartaric acid-assisted sol-gel technique. Investigation of the structure, lattice dynamics, magnetization and hyperfine interaction have been performed through X–ray diffraction (XRD), transmission electron microscope (TEM), Raman spectroscopy (RS), vibrating sample magnetometer (VSM) and Mössbauer spectroscopy (MS). The TEM images show that the particle sizes <D> of BFO, BSFO and BSFCO are respectively 11.4, 12.1 and 8.8 nm. The XRD analysis reflects a structural phase transition from rhombohedral R3c structure in case of BFO and BSFO samples to two phase coexistence (rhombohedral R3c and trigonal R–3m:R) in case of BSFCO sample. This structural phase transition has been strongly confirmed by the alterations in the vibration modes observed in Raman spectra (expansion, shift, merge, and reduced intensity). Second order vibration modes, corresponding to the two-phonon scattering in the range 650–1000 cm−1, have been recorded for all samples. Investigation of magnetic properties reveals that pure and Sr doped samples possess considerably high magnetic saturations (Ms = 5.61 and 5.79 emu/g respectively). Additionally, BSFCO sample shows enhancement in Ms (Ms rises to 8.26 emu/g). Suppression of spiral spin structure caused by the small nano-size has been assumed. The destruction of the spiral spin has been also suggested through M össbauer studies. The hyperfine parameters reveal that only Fe3+ is observed in two different nonequivalent trigonal distorted octahedral environments. The outcome of this work suggests the potentiality of Sr, Co co-doping to improve the structure and ferromagnetism of BiFeO3 ceramic making it feasible to be employed in enormous applications.

EFFECT OF CHELATING AGENTS, SINTERED TEMPERATURE AND HEAT TREATMENT DURATION ON THE STRUCTURAL AND ELECTRICAL PROPERTIES OF BiFeO3

&#x0D; &#x0D; &#x0D; A multiferroics BiFeO3 (BFO) samples are prepared by co-precipitation and sol-gel methods. Various combinations of chelating agent, sintering temperature and heat treatment durations tried to prepare single phase BiFeO3 samples. Sol-gel method is found more suitable to synthesize phase pure BiFeO3 samples. The samples were characterized by XRD, SEM, EDX, Electrical resistivity and optical reflectivity measurements. The distorted rhombohedral perovskite structure R3c has been confirmed. The grain size and lattice constant of the samples are also calculated using XRD patterns. The resistivity of the samples is measured at room temperature. The resistivity is found to increase on changing the chelating agent from Tartaric acid to Tartaric acid plus Ethylene glycol. The resistivity reveals the semi conductivity behavior of the BFO samples. The measurement of infrared reflectivity of BFO samples at room temperature reveals optical phonons. The resonant frequency of the phonon modes is determined and reported.&#x0D; &#x0D; &#x0D;

The role of samarium (Sm) dopant on structural, magnetic and ferroelectric properties of BiFeO3 for magnetic data storage

We report the role of novel samarium (Sm3+) doping on the structural, thermal, magnetic, and ferroelectric properties of BiFeO3. Polycrystalline Sm-doped BiFeO3 samples were synthesized using a conventional solid-state reaction route. Bi1-xSmxFeO3 (x = 0.02–0.08) samples crystallize in rhombohedral structure (R3c). With the increase of Sm3+ content, the decrease in crystal size is attributed to the change in lattice parameters, since the ionic radius of Sm3+ (0.95 Å) is smaller than that of Bi+3 (1.03 Å). A clear magnetic transition temperature (TN) peak was obtained by DSC measurements. With the increase of Sm3+ content, the peak temperature gradually decreased. Sm-doped BiFeO3 samples exhibit ferromagnetic and antiferromagnetic behaviors. Magnetism is strongly influenced by the substitution of Sm3+ ions in BiFeO3, and thus the magnetism of the synthesized samples is greatly changed compared to that of pure BiFeO3. Bi1-xSmxFeO3 (x = 0.02–0.06) samples have weak pointed hysteresis loops. While the BSFO-0.08 sample exhibit unsaturated rounded hysteresis loops possibly due to the large electrical leakage. Overall, we observed enhanced magnetic and ferroelectric properties by varying the Sm3+ content in BiFeO3. Therefore, the Sm3+ doping in BiFeO3 makes it a very prospective material for applications in spintronic devices, data storage devices, and sensors.

Study of the optical properties of BiFeO3 under different heat treatment temperatures

It is known that the optical absorption property of a material is linked to its crystal structure. Therefore, it can be modified or displaced when the material is subjected to thermal treatments, generating displacements of the unit cell, atomic positions and bond angles of its atoms. In this work, the analysis of three samples of BiFeO3 powders subjected to different heat treatment temperatures was carried out to study their optical properties by analyzing the crystal structure, diffuse reflectance, Raman scattering spectroscopy, density of state and band structure. In the results, the pure phase and the hexagonal structure of the samples were identified, showing an increase in the angles between the Fe-O-Fe atoms when the material is thermally treated. The band gap (Egexperimental) of the BiFeO3 samples without and with treatment temperature showed direct and indirect transitions according to the Tauc equation, these values were 2.36, 2.11 and 2.19 eV for direct band gaps and 2.10, 1.58 and 1.85 eV for indirect band gaps. In the Raman scattering spectroscopy analysis, overtones were observed in the samples when a green laser with a wavelength of 532nm (2.33 eV) was applied. In the density of states, the maximum valence band formed by the O(2p) state and the minimum of the conduction band formed by the hybridization of the Fe(3d) and O(2p) states were identified. In the electronic band structure, indirect band gap values (Egtheoretical) of 2.274, 2.216 (500 °C) and 2.217 eV (600 °C) were found for the samples without and with heat treatment. It is concluded that BiFeO3 absorbs visible light and that its band gap can decrease by increasing the bond angle of Fe-O-Fe atoms when the sample is subjected to heat treatment. These results demonstrate the semiconductor property of BiFeO3 and can be applied to solar cells, batteries, hydrogen production, among other applications.

Raman study of BiFeO3 nanostructures using different excitation wavelengths: Effects of crystallite size on vibrational modes

Bismuth ferrite (BiFeO3) is a perovskite metal oxide well known because of its multifunctional properties. In this study, we report Raman analysis of BiFeO3 nanostructures synthesized using the sol–gel method at different annealing conditions. The synthesis was conducted at two different annealing temperatures of 500 °C and 600 °C, and three different annealing rates of 2, 5, and 10 °C/min. The crystallite sizes and particle sizes were evaluated for the obtained nanostructures using X-ray diffraction and scanning electron microscopy. Raman scattering study was conducted for the prepared BiFeO3 samples at different excitation wavelengths in the visible and near-infrared region (457 nm, 532 nm, 633 nm, and 785 nm). The variations in the features of the Raman modes with different excitation wavelengths and annealing conditions were examined in detail. Resonant Raman scattering was observed when the excitation energy was comparable to or greater than the bandgaps of the BiFeO3 nanostructures, where the intensities of the A1-3, E-3, and E-4 vibrational modes increased. The variations in the relative intensities and areas of the A1-2 and A1-1 modes with the crystallite size were correlated with the occurrence of size-dependent magnetic properties in BiFeO3.

Chelating Agents Assisted Rapid Synthesis of High Purity BiFeO3: Remarkable Optical, Electrical, and Magnetic Characteristics

In this study, we presented two reliable methods, the sol–gel and autocombustion, to synthesis a high purity BiFeO3 single phase with low calcination time using glycine as chelating agent. The glycine-autocombustion method produced a high purity BiFeO3 phase using either low or high concentrations of the reactants (Bi(NO3)3 + Fe(NO3)3), while the glycine-sol–gel method delivered a high purity BiFeO3 phase using low concentrations of reactants. In the case of using tartaric acid and urea as chelating agents, mixtures of BiFeO3 and Bi25FeO40 phases were formed. The morphology, size, and porosity of the particles were obviously changed by varying the synthesis method and chelating agents. The high purity BiFeO3 samples exhibit a visible light band gap of 2.05 eV with long absorption tail extending to the infrared region, suggesting the suitability of the synthesized powders in the solar photocatalytic applications. A weak hysteresis ferromagnetic loop was observed for BiFeO3 (glycine method) and BiFeO3/Bi25FeO40 (urea method) with large contribution from the paramagnetic behavior. On contrast, robust ferromagnetic loops were found for BiFeO3/Bi25FeO40 sample synthesized by tartaric acid with saturation magnetization reaching to 2.5 emu/g. Remarkably, the pure single phase BiFeO3 powders synthesized by sol–gel and auto-combustion methods using glycine possess room temperature dielectric constant values of 622 and 845 respectively at a frequency of 42 Hz. In the case of BiFeO3 powders prepared by using tartaric acid, the dielectric constant exhibits values of 401 and 1118 for sol–gel and auto-combustion assisted samples, at the same frequency, respectively. At low frequency, the values of the real part of the complex permittivity tend to be zero which confirms a negligibly small contribution of the electrode effect.

Behavioral remodeling of perovskite BiFeO3 by Ag-doping strategies for enhanced and ppb level acetone sensing performance: An advanced enlightenment for selectivity and sensing mechanism

Improvement of the catalytic reactions on the sensing surface or modulation of charge carriers of the sensing material are the most favorable ways to enhance sensing performance for a chemi-resistive sensor. Incorporation of noble metals can enhance the sensing features of chemi-resistive type sensors by synergistic effect of chemical (catalytic effect) or electronic (tuning of charge carrier concentration) sensitization. In this view, the present study performs a behavioral remodeling of sol-gel synthesized BiFeO3 (BFO) chemi-resistive sensor by low-cost Ag-doping strategies to enhance its acetone sensing performance with removal of irreversibility. The Ag-doped BFO (Bi0.9Ag0.1FeO3) sensor can selectively detect acetone vapor (Rcross = RAcetone/RXylene: 17; RAcetone/RHexane: 08; RAcetone/RToluene: 05; RAcetone/RMethanol: 2.5; RAcetone/REthanol: 2.2) operating at 350°C. Ag-BFO sample shows an enhancement (1.8-fold) in response (R∼22) value with 5-fold faster response time (τres∼8s) for 50 ppm acetone exposure compared to pristine BFO (R∼12, τres∼45s). Excellent repeatability over 09 loop character with high degree of long-term stability for 300 days and ppb level detection (500 ppb) favorable to biomarker recognition for critical diseases confirms the commercial viability of Ag-doped BFO sample. The ion-dipole (highest interaction energy, Ei-d = -1.02 × 10−19 J for acetone)/dipole-dipole coupling, the ferroelectric nature of BiFeO3 and sensitization effect (by metallic Ag-phase) has paved the path for revealing the selectivity and sensing mechanism for the prepared prototype in an innovative way.

Structural, dielectric, magnetic, and ferroelectric properties of bismuth ferrite (BiFeO3) synthesized by a solvothermal process using hexamethylenetetramine (HMTA) as precipitating agent

Multiferroic BiFeO3 (BFO) has been synthesized by the solvothermal technique for 4 h at 180 °C using Hexamethylenetetramine (HMTA) as a precipitating agent. Optimizations on HMTA concentration were performed to attain BFO in a narrow possible time using the solvothermal method. The effect of HMTA concentration on structural properties was investigated by XRD, FE-SEM, FT-IR, and Raman techniques. Moreover, the magnetic, ferroelectric, dielectric, and optical properties were studied by VSM, Ferroelectric analyser, Dielectric spectrometer, and UV–Vis–NIR spectrometer, respectively. The XRD data has unveiled the significant role of HMTA, as a precipitating agent, in obtaining the pure phase BFO at a particular concentration. A high concentration of HMTA (6 M) is found to be more favourable for producing pure phase BFO within the short reaction time of 4 h without any impurity phase formations. The FE-SEM images have shown the formation of granular structures that are inhomogeneously distributed throughout the powdered BFO with porosities. In addition, the magnetic measurements confirmed that the BFO synthesized with varying HMTA concentration exhibits a reasonable week ferromagnetic behaviour. However, the pure BFO powder synthesized at 6 M HMTA shows high magnetization value (0.72 emu/g) compared to the other samples synthesized at low concentrations of HMTA. Further, the dielectric measurements of all the synthesized BFO samples have shown a decrease in dielectric loss with an increase in frequency. Whereas the dielectric behaviour exhibited by the pure BFO synthesized at 6 M HMTA has shown a high dielectric constant value with moderate dielectric loss. A ferroelectric analyser studies the ferroelectric behaviour of BFO powder. The study revealed that pure phase BFO synthesized with 6 M HMTA exhibits a high value of remanent polarization with unsaturated P-E loops due to the high leakage current in the sample. The UV–Vis data shows that the BFO samples exhibited an excellent optical absorption in the visible range with narrow optical band gaps. Therefore, all the characterizations related to magnetic, structural, dielectric, ferroelectric, and optical properties of synthesized pure BFO have proven the significance of precipitating agent HMTA in the solvothermal synthesis method. Based on our findings, the synthesized pure phase BFO can be an excellent semiconducting photocatalyst for multiferroic based photocatalysis applications.

Chemical Solution Deposition of Single‐Phase BiFeO3 Thin Films on Transparent Substrates

The production of high‐quality BiFeO3 thin films on cost‐effective transparent electrodes for visible light harvesting applications and devices remains a challenge. Here, the production of single‐phase nanostructured BiFeO3 thin films via chemical solution deposition (CSD) on transparent conductive fluorine‐doped tin oxide FTO glass substrates is reported. It is shown that BiFeO3 is of high purity using a variety of analytical tools and that the as‐obtained BiFeO3 thin films have a single‐grain single‐domain structure exhibiting ferroelectric switching under poling. The BiFeO3 samples show visible light absorption with a bandgap of 2.7 eV under all processing conditions. By changing the annealing atmosphere, it was possible to modify the photocurrent produced, which were (at 1.23 VNHE) 0.07 (O2‐annealed), 0.02 (air‐annealed), and 0.01 mA cm−2 (Ar‐annealed). This indicates a change in the mobile carriers available. The results show that it is possible to produce single‐phase BiFeO3 on a transparent conductive electrode system with controllable photoconductivity.

Structural phase transition, phase purity, inter-/intra-grain electrical parameters and local energy barrier profile as a function of aliovalent and isovalent substitution in BiFeO3

The presence of space charges deteriorates the electrical properties of multiferroics and limits their use in commercial devices. However, identification of the conduction mechanisms and their origin is a very challenging task. In this study electrical and dielectric responses of pure and substituted BiFeO3 samples are studied in detail by intentionally controlling the formation of oxygen vacancies and space charges via a variety of isovalent and aliovalent substitutions. Polydispersive inter- and intra-grain hopping mechanisms are traced as a function of substitution to highlight finer details associated with their origin. Additionally, for quantification purposes, equivalent circuit analysis of Nyquist and Cole-Cole plots is carried out to extract intra/inter grain parameters, such as resistivity and permittivity, and to establish the polydispersive nature of the conduction mechanisms. With the consideration of all observed conductivity processes and their activation energies, an overall schematic energy barrier diagram is plotted. Equivalent circuit analysis is also utilized for the estimation of grain and grain boundary capacitance and resistance values. Results obtained after dielectric analysis, Cole-Cole and Nyquist plots are confirmed based on sample compositions and discussed in terms of the ionic radii mismatch and valence state of the substituents and indicate that both parameters play an effective role in controlling the mechanisms associated with the oxygen content in the sample.