Pristine BiFeO3 Research Articles

Facilitated Photocatalytic Degradation of Rhodamine B over One-Step Synthesized Honeycomb-Like BiFeO3/g-C3N4 Catalyst.

In the present work, a facile one-step methodology was used to synthesize honeycomb-like BiFeO3/g-C3N4 composites, where the well-dispersed BiFeO3 strongly interacted with the hg-C3N4. The 10BiFeO3/hg-C3N4 could completely degrade RhB under visible light illumination within 60 min. The degradation rate constant was remarkably improved and approximately three times and seven times that of pristine hg-C3N4 and BiFeO3, respectively. This is ascribed to the following factors: (1) the unique honeycomb-like morphology facilitates the diffusion of the reactants and effectively improves the utilization of light energy by multiple reflections of light; (2) the charged dye molecules can be tightly bound to the spontaneous polarized BiFeO3 surface to form the Stern layer; (3) the Z-scheme heterojunction and the ferroelectric synergistically promoted the efficient separation and migration of the photogenerated charges. This method can synchronously tune the micro-nano structure, surface property, and internal field construction for g-C3N4-based photocatalysts, exhibiting outstanding potential in environmental purification.

Effects of 120 MeV Ag9+ swift heavy ion irradiation on the structural, optical and electrical properties of pristine and Ni doped BiFeO3 thin films grown by pulsed laser deposition

In this work, the effects of swift heavy ion (SHI) irradiation on the structure, morphology, optical and electrical properties of pristine and Ni-doped BiFeO3 thin films have been explored. The thin films with composition of BiFe1-xNixO3 (x = 0, 0.01, 0.03 and 0.05) were deposited on the n-type single crystal Si(100) substrates through pulsed laser deposition technique. Further, irradiation on the thin films was performed with 120 MeV Ag9+ ions at different ion fluences, i.e., 1 × 1013, 5 × 1013 and 1 × 1014 ions/cm2. To investigate the effects of SHI irradiation on the aforementioned properties, all the films have been characterized by various analytical techniques, such as X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, UV-visible diffuse reflectance spectroscopy and two-probe resistivity setup. The effects of the irradiation on the crystal structure and phase of the thin films were analyzed by the XRD and Raman measurements, and it has been observed that irradiation tends to amorphize the thin films. A decrease in the band gap has been observed for the irradiated thin films with the increase of ion fluence. The current-voltage plots of all the unirradiated and irradiated thin films demonstrate the rectifying diode type characteristics.

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.

Heterostructured BiFeO3@CdS nanofibers with enhanced piezoelectric response for efficient piezocatalytic degradation of organic pollutants

Piezocatalysis converting mechanical energy into chemical energy is deemed as an emerging technology for degradation of organic pollutants in water or air. In this work, BiFeO3@CdS nanofibers with heterostructure and enhanced piezoelectric response were prepared for efficient piezocatalytic degradation of organics in water. The optimal BiFeO3@CdS-10% achieved nearly complete removal of bisphenol A (BPA) within 60 min with the degradation rate constant of 0.098 min−1, which was 9.4 and 4.9 times higher than that of pristine BiFeO3 and CdS, respectively. The excellent piezocatalytic activity of the composite can be attributed to the construction of heterojunction and the enhanced piezoelectric response from the synergistic effect of the two piezoelectric components, which can accelerate the internal transfer of free carriers. It gives an insight into the feasible construction of efficient piezocatalysts and opens up a new way for BiFeO3-based piezoelectric materials to be utilized in purification of wastewater.

Electron density distribution influencing the electrical and magnetic properties of polycrystalline Bi0.9Sm0.1FeO3 ceramics

Abstract This article reports the structural properties that influence the electrical and magnetic behaviours of polycrystalline Bi1−x Sm x FeO3 (x = 0, 0.1) ceramics. The samples are synthesized by a two-step solid state reaction. X-ray diffraction patterns expose two characteristic peaks corresponding to (104) and (110) planes around 31°. Bi1−x Sm x FeO3 (x = 0, 0.1) samples crystalize primarily in the R3c phase along with the traces of secondary phases. The Rietveld refinement analysis reveals that the tilt angle of Bi0.9Sm0.1FeO3 reduces due to the twisting of FeO6 octahedra compared to pristine BiFeO3. The electron density distribution and type of bonding are analyzed using the maximum entropy method. The microstructural analysis reveals that the Bi0.9Sm0.1FeO3 sample has a reduced average particle size compared to pristine BiFeO3. The influence of samarium ions in the bismuth site deviates the canting angle of the modulated spiral spin arrangement and the charge density distribution of the Bi0.9Sm0.1FeO3 sample as a result, the electrical and magnetic behaviours are improved compared with bare BiFeO3.

Significantly improved photocatalytic activity of the SnO2/BiFeO3 heterojunction for pollutant degradation and mechanism

Herein, motivated with narrow/wide-bandgap heterojunction materials as one of the perfect solutions, we separately synthesized BiFeO3 (BFO) and SnO2 nanoparticles; then coupled them in various weight percentages to obtain nanocomposites with efficient contacts for visible light 2,4-DCP and RhB degradation and effectively reduced charge recombination. The material of interest, i.e., with six weight percentage coupling of SnO2 (i.e., 6SO/94BFO), endorsed superior photoactivity for 2,4-DCP and RhB degradation. In addition, under the visible light irradiation, this photocatalyst degraded 87.2% of RhB and 65.1% of 2,4-DCP in 2h, which compared to pristine BiFeO3 nanoparticles are about 2.6- and 2.7-times enhancements, respectively. The photoluminescence spectroscopy and mechanism model showed a substantial interface between BiFeO3 and SnO2 and unfeasible electron-holes recombination. The electrons and holes are entirely utilized to produce superoxides and •OH radicals, respectively, predicting enhanced visible-light photodegradation. Overall, this work offers novel narrow/wide-bandgap heterojunction nanocomposites as feasible aspirants for pollution control and effective visible light photodegradation of chlorinated compounds.

Effect of (Zn, Mn) co-doping on the structure and ferroelectric properties of BiFeO3 thin films

BiFe1-2xZnxMnxO3 (BFZMO, with x = 0–0.05) thin films were synthesized via sol–gel method. Effects of (Zn, Mn) co-doping on the structure, ferroelectric, dielectric, and optical properties of BiFeO3 (BFO) films were investigated. BFZMO thin films exhibit rhombohedral structure. Scanning electron microscopy (SEM) images indicate that co-doping leads to a decrease in grain size and number of defects. Leakage current density (4.60 × 10−6 A/cm2) of BFZMO film with x = 0.02 was found to be two orders of magnitude lower than that of pristine BFO film. Owing to decreased leakage current density, saturated P–E curves were obtained. Maximum double remnant polarization of 413.2 μC/cm2 was observed for BFZMO thin film with x = 0.02, while that for the BFO film was found to be 199.68 μC/cm2. The reason for improved ferroelectric properties is partial substitution of Fe ions with Zn and Mn ions, which resulted in a reduction in the effect of oxygen vacancy defects. In addition, co-doping was found to decrease optical bandgap of BFO film, opening several possible routes for novel applications of these (Zn, Mn) co-doped BFO thin films.

Training the Polarization in Integrated La0.15 Bi0.85 FeO3 -Based Devices.

The functionalities of BiFeO3 -based magnetoelectric multiferroic heterostructures rely on the controlled manipulation of their ferroelectric domains and of the corresponding net in-plane polarization, as this aspect guides the voltage-controlled magnetic switching. Chemical substitution has emerged as a key to push the energy dissipation of the BiFeO3 into the attojoule range but appears to result in a disordered domain configuration. Using non-invasive optical second-harmonic generation on heavily La-substituted BiFeO3 films, it is shown that a weak net in-plane polarization remains imprinted in the pristine films despite the apparent domain disorder. It is found that this ingrained net in-plane polarization can be trained with out-of-plane electric fields compatible with applications. Operando studies on capacitor heterostructures treated in this way show the full restoration of the domain configuration of pristine BiFeO3 along with a giant net in-plane polarization enhancement. Thus, the experiments reveal a surprising robustness of the net in-plane polarization of BiFeO3 against chemical modification, an important criterion in ongoing attempts to integrate magnetoelectric materials into energy-efficient devices.

Synthesis of spinel Tin ferrite decorated on Bismuth ferrite nanostructures for synergetic photocatalytic, superior drug delivery, and antibacterial efficiencies

The present study shows that the sono-chemically synthesis of SnFe2O4/BiFeO3 nanocomposites for the photocatalytic performance. The crystal structure of SnFe2O4/BiFeO3 nanocomposites evaluated using XRD analysis. The micrograph images displays the support of SnFe2O4 on BiFeO3. The optical status were examined using UV-Vis spectroscopy and the narrower band gap (1.67 eV) was determined for SnFe2O4/BiFeO3 nanocomposites. The photocatalytic amount of SnFe2O4/BiFeO3 nanocomposites was higher than the pristine SnFe2O4 or BiFeO3 nanoparticles. The photocatalytic degradation was mainly performed by OH· radical. The malachite green dye was completely degraded (100%) by using the SnFe2O4-BiFeO3 nanocomposites in 60 min under visible light irradiation. The antibacterial activity of SnFe2O4/BiFeO3 nanocomposites was conducted against Escherichia coli and Bacillus subtilis bacteria. The doxorubicin as an anticancer drug was loaded on SnFe2O4/BiFeO3 nanocomposites. The cell viability of the human liver cancer cell was performed by using doxorubicin/SnFe2O4/BiFeO3/folic acid. The potential properties shows that the usage of SnFe2O4/BiFeO3 nanocomposites in environmental treatment, antibacterial, and drug delivery applications.

Visible Light Photocatalytic Degradation of Sunset Yellow Dye and Industrial Textile Wastewater Using Pd-BiFeO3 Composite

Herein, pristine BiFeO3 and Pd-incorporated BiFeO3 (Pd-BiFeO3) composite were synthesized using hydrothermal synthesis method. The physiochemical and optical properties of the synthesized materials were investigated using numerous techniques. The Pd-BiFeO3 composite significantly enhanced the photocatalytic degradation of sunset yellow (SSY) dye in comparison with the pristine BiFeO3 under visible light irradiation. The enhanced photoactivity was credited to the improved photogenerated charge carrier separation, which was in accordance with the photoelectrochemical measurements. Moreover, the Pd-BiFeO3 composite can be recycled for seven consecutive runs without sufficient loss of photocatalytic activity. Radical trapping studies suggested that the hydroxyl radical (•OH), hydrogen peroxide (H2O2) and hole (h+) were the key reactive oxidizing species. A possible photocatalytic enhancement mechanism of Pd-BiFeO3 composite was stated. Finally, for the first time, the Pd-BiFeO3 composite was also applied towards the effective degradation of industrial textile wastewater.

Photoconductivity and Photovoltaic Studies on Polycrystalline Bi1−xM′xFe1−yM″yO3−δ (M′ = K+ and Cs+; M″ = Ti4+; x = y = 0 and 0.1) Thin Films

The recent surge of interest in using all-inorganic materials like CsPbI3 for photovoltaic devices has brought significant interest in exploring the properties of BiFeO3 (BFO) by substituting Cs+ and K+ at the Bi3+ site. The aim of the present work is to study the parameters like controlling the lattice and surface oxygen vacancy (VO) defects which can significantly improve the photovoltaic device performances. Monovalent substituted and aliovalent co-substituted Bi1−xM'xFe1−yM"yO3−δ (M′ = K+ and Cs+; M" = Ti4+; x = y = 0 and 0.1) are grown on fluorine-doped tin oxide (FTO)/glass substrates by metal-organic chemical solution deposition method. Photoconductivity and photovoltaic properties of these films are studied in FTO/Bi1−xM'xFe1−yM"yO3−δ/Au capacitor configuration. Aliovalent substitution (for M' = K+ and Cs+, BK10FO and BCs10FO, respectively) at Bi3+ sites create VO in BFO thin films. Further, grain size reduction from 100 nm to 30 nm also results in the creation of surface VO defects. Tauc plot shows a reduction in the bandgap (Eg) values from 2.32 eV to 2.26 eV due to the formation of mid-bandgap VO defect states. Consequently, ferroelectric properties also get diminished. Aliovalent K+-Ti4+ co-substitution in BFO thin films brings back the Eg values to 2.3 eV, i.e., similar to pristine BFO thin films suggesting suppression of VO. This results in the revival of ferroelectric nature in aliovalent co-substituted thin films. Photoconductivity studies show two order enhancement in conductivity for BK10FO thin film devices compared to pure BFO. This enhancement is attributed to the mid-bandgap VO defect states due to aliovalent substitution. On the other hand, photoconductivity observed in BCs10FO devices is comparable with pristine BFO devices. Contrary to this, aliovalent co-substituted thin films show a decreasing trend of photoconductivity compared to M'+ substituted BFO suggesting that VO defects get suppressed due to charge compensation. Photoconductivity and photovoltaic device studies show similar behavior. BK10FO devices exhibit short circuit current density (JSC) ~0.45 µA/cm2, which is larger than that observed in BFO devices (JSC ~0.3 µA/cm2). But, BCs10FO devices show lesser JSC 0.07 µA/cm2. Open circuit voltage (VOC) observed in BFO devices is around 3 V which decreases to 0.1 V and 0.06 V for BK10FO and BCs10FO devices, respectively. This decrease in VOC is attributed to the reduction of the ferroelectric nature of the films. BFO, BK10FO, and BCs10FO devices show photovoltaic switching upon poling the films. Co-substituted thin films show a reduction in the JSC and betterment in the VOC compared to the monovalent substituted BFO thin films. This happens due to the suppression of VO defects by partial charge compensation in aliovalent co-substituted BFO films. This study explicitly brings out the role of VO on the photovoltaic and photoconductivity properties of BFO thin films.

Tourmaline Modified BiFeO3 Based MEMS Sensor with Temperature-Dependent Dual Selectivity for Detecting Acetone and Hydrogen Sulfide

In recent years, design and synthesis of heterostructured nanomaterials with high gas-sensing performance for detection of flammable and toxic gases has attracted much research interest. In this paper, pristine and tourmaline-modified BiFeO3(BFO) nanomaterials were successfully synthesized via a sol-gel method. The BiFeO3 modified with tourmaline could remarkably enhance the gas response and exhibit some novel properties. The tourmaline/BiFeO3 3wt% (tourmaline/BiFeO3 composite with the 3wt% tourmaline) MEMS sensor exhibited temperature-dependent dual selectivity to CO at 150 °C and H2S at 225 °C. The tourmaline/BiFeO3 3wt% based MEMS sensor response toward 0.77 ppm of acetone (C3H6O) is 4.3 at 150 °C and toward 0.75 ppm of hydrogen sulfide (H2S) reaches 11.6 at 225 °C. Furthermore, the sensor possessed good repeatability and antihumidity interference. The dramatically improved sensing performance could be ascribed to the spontaneous polarity of tourmaline, the electron transfer was modulated by the heterojunction in the interface between the BiFeO3 and tourmaline nanostructure. The easy fabrication and good gas sensing performances make our sensors highly attractive for ultrasensitive C3H6O and H2S gas detection with less power consumption. Figure 1

Insight into the influence of noble metal decorated on BiFeO3 for 2,4-dichlorophenol and real herbicide wastewater treatment under visible light

The exploitation of effective and environmental benign techniques for treating agricultural runoff recalcitrant herbicides is an on-going challenge. In this regard, any feasible photocatalytic technology in the visible light region so as to adopt the abundant and clean sunlight serves as an indispensable task. Herein, different noble metal cocatalysts (NM = Au, Ag and Pt) decorated on BiFeO3 (NM-BiFeO3) composites were synthesized using a facile two-steps hydrothermal process, and characterized by physicochemical approaches to identify their structural, photoelectrochemical and optical traits. The Pt-BiFeO3 composites displayed prodigious visible light photodegradation of 2,4-dichlorophenol (2,4-DCP) (100 %), much higher than those Au-BiFeO3 (92.4 %), Ag-BiFeO3 (83.2 %), commercial TiO2 (67.5 %) and pristine BiFeO3 (64.1 %) in 240 min. The Pt cocatalyst was more effective than other NMs owing to its higher work function and height of Schottky barrier, which can be greatly delayed the recombination of charge carriers. Photoluminescence and photoelectrochemical measurements have also been taken to validate this conclusion. Based on these, the possible mechanism for photodegradation of 2,4-DCP over NM-BiFeO3 was postulated. The Pt-BiFeO3 can be recyclable for photodegradation of 2,4-DCP along with a minimal Pto ions leakage even after seven consecutive runs. The degraded intermediates of 2,4-DCP were also detected to propose degradation pathways. Moreover, according to the radical-capturing and terephthalic acid-photoluminescence tests, the core stimulus in the photocatalytic reaction were determined. The Pt-BiFeO3 had demonstrated its excellent catalytic ability in the real herbicide wastewater treatment. Toxicity assay of treated herbicide wastewater also showed minimal effects on the growth of wild algae.

Enhanced magnetoelectric coupling in dysprosium-doped BiFeO3 on the formation of nanocomposite with SrFe12O19

Nanocomposites (NCs) containing strontium hexaferrite (SrFe12O19, SFO) and dysprosium-substituted bismuth ferrite (Bi0.9Dy0.1FeO3, BDFO) with composition x SrFe12O19 - (1-x) Bi0.9Dy0.1FeO3, with x = 0.1, 0.2, and 0.3, have been synthesized using the sol-gel route and their structural, magnetic, dielectric and magnetoelectric properties have been investigated. Formation of pure crystalline x SFO - (1-x) BDFO NCs is confirmed by XRD measurements. Magnetization and dielectric constant (εr) of the pristine BiFeO3 (BFO) have been found to increase on Dy-substitution. In the nanocomposite samples, magnetization increases, but dielectric constant decreases with increasing SFO content. Variation of capacitance of the NC samples in the presence of magnetic field up to 150 kOe indicates a substantial enhancement of the magnetoelectric (ME) coupling coefficient of BFO in the nanocomposites. ME coupling tends to improve with higher SFO content in the NCs.

Enhanced photoelectrochemical performance in BiFeO3/g-C3N4 p–n heterojunction photocathodes with ferroelectric polarization

Ferroelectric has been considered as a promising material in the photoelectrochemical (PEC) water splitting area. Here, we design the hybrid ferroelectric–semiconductor heterostructure photocathode for enhanced PEC performance; BiFeO3 (BFO) is used for ferroelectric while two dimensional material g-C3N4 for the semiconductor. The optimized BFO/g-C3N4 heterojunction photocathode shows a 2.4 times enhancement in the photocurrent density than the pristine BFO sample. The improvement in the PEC performance is ascribed to the type II heterojunction formed between BFO and g-C3N4, resulting in the enhanced separation of the photogenerated charge carriers. More importantly, the PEC performance can be further improved by positive polarization of the BFO/g-C3N4 heterojunction photocathode. Our ferroelectric–semiconductor heterojunction material may be a promising solution for achieving highly efficient PEC systems.

Chemical pressure induced near-complete suppression of spin-wave excitations in Bi0.9A0.1FeO2.95 (A = Ba, Ca)

We have probed the changes in the phonon and magnon modes of BiFeO3 on substitution of Ba and Ca at the A-site using infrared reflectance spectroscopy. The systematic hardening of the phonon modes in the doped samples is seen to correlate well with the volume reduction of the unit cell observed from the Rietveld measurements. This is attributed to the generation of chemical pressure in these samples on account of substitution of the dopants. In addition, a near-complete suppression accompanied by a complete lifting of the degeneracy of the magnon modes as compared to the pristine BiFeO3 is detected for the Ca-doped samples. These results suggest that aliovalent doping at A-site affects the crystal field of FeO6 octahedra of BiFeO3, which eventually modifies its magnetic nature. These doping-induced modifications are mainly responsible for the improved magnetic and magnetoelectric properties of the Ca-doped BiFeO3 samples.

Phase transition and optical properties of samarium-doped BiFeO3 nanoparticles

Multiferroics are the materials having ferroelectric and magnetic properties simultaneously and can be tuned by controlling electric and magnetic field for the desired applications. Pure and samarium-doped bismuth ferrite nanoparticles Bi1−xSmxFeO3 (BSFO x = 0, 0.05, 0.10, 0.15, 0.20) with varied doping concentrations have been synthesized using sol–gel technique. The effect of doping on structural, morphological, elemental composition and optical properties were analyzed using various characterization techniques. X-ray diffraction (XRD) analysis of Bi1−xSmxFeO3 samples show the compressive lattice distortion and structural phase transformation from rhombohedral to orthorhombic phase. The Rietveld refinement shows that the crystalline structure of pristine BiFeO3 (BFO) is typical rhombohedral structure with R3c space group. Scanning electron micrograph (SEM) reveals that with increasing Sm concentration the grain size decreases up to ~ 30 nm. XRD and SEM analysis confirmed the synthesized samples having pure phase formation and nanocrystalline nature. Ultraviolet–Visible (UV–Vis) spectra of the samples show that the enhanced visible light absorption would be a promising material for photocatalytic application. The findings of X-ray photoelectron spectroscopy (XPS) verify the effective Sm doping in BFO samples.

Enhanced Magnetic Properties of Co-Doped BiFeO3 Thin Films via Structural Progression.

Co3+ doping in BiFeO3 is expected to be an effective method for improving its magnetic properties. In this work, pristine BiFeO3 (BFO) and doped BiFe1-xCoxO3 (BFCxO, x = 0.01, 0.03, 0.05, 0.07 and 0.10) composite thin films were successfully synthesized by a sol–gel technique. XRD and Raman spectra indicate that the Co3+ ions are substituted for the Fe3+ ion sites in the BFO rhombohedral lattice. Raman vibration of oxygen octahedron is obviously weakened due to the lattice distortion induced by the size mismatch between two B-site cations (Fe3+ and Co3+ ions), which has an impact on the magnetic properties of BFCxO. SEM images reveal a denser agglomeration in Co-doped samples. TEM results indicate that the average size of grains is reduced due to the Co3+ substitution. XPS measurements illustrate that the replacement of Fe3+ with Co3+ effectively suppresses the generation of oxygen defects and increases the concentration of Fe3+ ions at the B-site of perovskite lattice. Vibrating sample magnetometer (VSM) measurements show that the remanent magnetization (Mr) of BFC0.07O (3.6 emu/cm3) and the saturation magnetization (Ms) of BFC0.10O (48.84 emu/cm3) thin film both increase by approximately two times at room temperature, compared with that of the pure BFO counterpart.

Polarization-enhanced bulk photovoltaic effect of BiFeO3 epitaxial film under standard solar illumination

In this Letter, we report the polarization-enhanced bulk photovoltaic effect (BPV) in pristine BiFeO3 (BFO) epitaxial film under standard 1 sun AM 1.5 G illumination. High-quality epitaxial BFO films are grown on (001)-oriented niobium doped-SrTiO3 substrates by pulsed laser deposition. The best BFO film based photovoltaic device achieves a power conversion efficiency of 0.0062% under standard illumination. Besides, it is found that the number of bipolar pulses plays a key role in improving the short-circuit current density and open-circuit voltage. These results are beneficial for further understanding of physical origin of the photovoltaic properties in ferroelectric oxides.

The effect of gradient conductivity of doped BiFeO3 as filler on the surface insulation performance of epoxy composite

In this paper, we studied the effect of filler conductivity on the surface insulation of composites. We proposed using different valence element doping as a strategy to prepare filler with gradient conductivity. The pristine BiFeO3 (BFO), Bi0.95Ca0.05FeO3, and Bi0.95Sm0.05FeO3 nanoparticles were prepared to fill into epoxy resin. The Rietveld refinement of the x-ray diffraction patterns was performed to investigate the transition of the lattice structure. According to the Kubelka–Munk function, the energy bandgap was calculated to verify the regulation of the BFO conductivity. Subsequently, we measured the flashover voltage of the composites with three types of BFO in ambient and vacuum atmosphere, respectively. We found the vacuum flashover is more sensitive to filler conductivity, and BFO with higher conductivity as filler is more conducive to surface insulation, whether in the air or vacuum. Finally, the optimal BFO bandgap of 2.1819 eV is determined for enhancing surface insulation of composites. Our research supplies a novel method for constructing high insulation composites for more wide applications and provides a scientific basis on flashover mechanism from the perspective of filler characteristics.