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Photodegradation of methylene blue by mechanosynthesized BiFeO <sub/>3</sub> submicron particles
摘要： In this paper, the photocatalytic activity of bismuth ferrite particles synthesized by high-energy ball milling is evaluated by considering the degradation of methylene blue solutions. Once chemical routes are extensively used to produce these kind of photocatalytic reactors, this mechanochemical route has the advantage of large-scale and low-cost production. The structural, microstructural and optical properties of bismuth ferrite powders are investigated and the photocatalytic efficiency is experimentally proved. The results show a degradation of 95% of the methylene blue dye, which became complete after the addition of the H2O2 oxidizing agent and 15 min of illumination.
关键词： photodegradation,bismuth ferrite,Photocatalysis
更新于2025-10-22 19:40:53
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Electrode Dependence of Local Electrical Properties of Chemical-Solution-Deposition-Derived BiFeO <sub/>3</sub> Thin Films
摘要： The nanoscale electrical properties of chemical solution deposition(CSD)-derived BiFeO3 grown on pulsed laser ablated La0.67Sr0.33MnO3//SrTiO3 (001) thin film heterostructures are investigated using a host of scanning probe microscopy techniques, including electrostatic force microscopy(EFM), scanning Kelvin probe microscopy(SKPM), piezoresponse force microscopy (PFM), and conductive AFM(CAFM). EFM and SKPM confirm the p-type nature of the CSD derived BFO thin films as well as charge accumulation at the film surface after electrical bias. For BiFeO3 films of a fixed thickness (~35 nm), the local current-voltage (I-V) behavior obtained by CAFM is strongly dependent on the La0.67Sr0.33MnO3 bottom electrode thickness. BiFeO3 films on a 20 nm thick La0.67Sr0.33MnO3 demonstrate the typical switchable diode behavior governed by polarization orientation. However, when the thickness of La0.67Sr0.33MnO3 is reduced to less than 5 nm, the BiFeO3 films show only forward diode behaviors regardless of polarization orientation, when the applied bias is up to ±4 V. Higher sweep bias (i.e. ±8V) breaks down the diode, following which the BiFeO3 film shows strong resistive switching. The interface band structure for the ultra-thin LSMO case, which is very sensitive to accumulation/depletion of carriers at the BFO-LSMO interface, is suggested as the trigger for this resistive switching.
关键词： chemical solution deposition,ferroelectric,electrical properties,ultrathin lanthanum strontium manganite,p-type bismuth ferrite thin films
更新于2025-09-23 15:23:52
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Orientation Dependence of Elastic and Piezoelectric Properties in Rhombohedral BiFeO3
摘要： Through a coordinate transformation approach, crystal orientation dependences of elastic and piezoelectric properties at room temperature have been investigated in a three-dimensional space for rhombohedral bismuth ferrite (BiFeO3). Elastic constants (stiffnesses) c11', c12', c13' and piezoelectric constants d15', d31', d33' along arbitrary orientations were obtained based on crystalline asymmetry characteristics of 3m point group BiFeO3. Parameters along specific orientations obtaining the largest values were presented. The max c11' = 213 × 10^9 N/m^2 could be achieved in planes with φ = 0° and 90°. The max c12' = c13' = 132.2 × 10^9 N/m^2 could be achieved along directions at θ = 13° and θ = 77° inside three mirror planes, respectively. The max d15' = 27.6 × 10^{-12} C/N and the max d31' = 12.67 × 10^{-12} C/N could be both obtained along directions at θ = 69° inside mirror planes. The max d33' = 18 × 10^{-12} C/N could be obtained at θ = 0°, along the spontaneous polarization axis. By adopting optimal directions, the elastic and piezoelectric parameters of BiFeO3 could be significantly enhanced which shows applications for the growth of BeFeO3 films with preferred orientations and enhanced properties.
关键词： piezoelectricity,coordinate transformation,orientation dependence,bismuth ferrite,elasticity
更新于2025-09-23 15:22:29
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Synthesis of hollow spheres of BiFeO3 from nitrate solutions with tartaric acid: Morphology and magnetic properties
摘要： Single-phase powders of bismuth ferrite have been synthesized for the first time by ultrasonic spray pyrolysis from nitrate solution in the presence of tartaric acid. The produced powders consist of hollow spherical agglomerates with a mean diameter of ~1 μm. The influence of tartaric acid concentration on the synthesis temperature and morphology of hollow spheres was established. The agglomerate shells have open and closed pores. The mean values of the shell thickness and the ratios of closed and open pores were estimated and their dependence on the concentration of tartaric acid was found. It was shown that the magnetic properties are determined not only by the size of nanoparticles composing the agglomerates, but also by the morphology of hollow sphere shells.
关键词： hollow spheres,morphology,magnetic properties,multiferroics,bismuth ferrite
更新于2025-09-23 15:21:21
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AC Impedance Spectroscopy, Conductivity and Optical Studies of Sr doped Bismuth Ferrite Nanocomposites
摘要： Effect of Sr doping on the structural, optical, dielectric, impedance properties of citrate combustion reaction route prepared Bi1-xSrxFeO3 (BSFO) nanocomposite has been investigated. The study of Fourier Transform Infrared Spectroscopy confirms the formation of perovskite structure of the Sr doped bismuth ferrite samples. SEM analysis shows decrease in grain size with increasing Sr concentration in BSFO nanocomposite. UV–visible absorption spectra in the spectral range 1.0–3.5 eV showed two doubly degenerate d–d transitions and two charge transfer transitions and optical band gap is found to decrease from 2.14 to 2.05 eV with increasing Sr concentration. Studies of frequency and temperature dependences of dielectric permittivity, impedance and electric modulus of the materials in broad frequency (20 Hz- 1 MHz) and temperature (30o C – 500oC) ranges using a complex impedance spectroscopy technique have provided interesting information on the contribution of the microstructure in these parameters. It has been observed that dielectric constant and dielectric losses decreases as the doping of Sr increased from x=0.1 to x=0.3 and attained a maximum value for BSFO (x = 0.1) sample. Impedance analysis indicates the presence of grain (bulk) and grain boundary resistive contributions which are found to increase with the increased Sr content. The ac conductivity of the samples is found to be frequency and temperature dependent and also vary with extent of Sr doping in BFO. Charge transport through short as well as long range conduction contributions has been indicated in different temperature regions of conductivity studies.
关键词： dielectric response,complex impedance spectroscopy,microstructure,Bismuth ferrite
更新于2025-09-23 15:21:01
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Nd-Cr co-doped BiFeO3 thin films for photovoltaic devices with enhanced photovoltaic performance
摘要： BiFeO3 films and Nd-Cr co-doped BiFeO3 films were prepared by sol-gel method followed by spinning process on fluorine-doped tin oxide glass substrates. By testing the ultraviolet-visible absorption spectra, it was found that Nd-Cr co-doping will increase the light absorption rate of the film and reduce the optical band gap. The reduced bandgap can facilitate the transport of carriers. After Nd-Cr co-doping, the leakage current of the film is effectively reduced, which is near four orders of magnitude lower than the leakage current density of the pristine BiFeO3 film. The reduction of leakage current will enhance the ferroelectric polarization. The enhancement of ferroelectric polarization is more favorable for the separation of photogenerated carriers. Compared with the pristine BiFeO3 film, the short circuit photocurrent density, open circuit photovoltage and power conversion efficiency of Nd-Cr co-doped BiFeO3 film are all clearly improved. The Nd-Cr co-doped BiFeO3 films exhibited largely enhanced photovoltaic property, which favored the practical application of BiFeO3-based films in photovoltaic devices.
关键词： Element doping,Thin films,Ferroelectric property,Photovoltaic property,Bismuth ferrite,Leakage current
更新于2025-09-23 15:19:57
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Response surface optimization of hydrothermal synthesis of Bismuth ferrite nanoparticles under supercritical water conditions: Application for photocatalytic degradation of Tetracycline
摘要： Ultra?ne bismuth ferrite (BiFeO3) powders have been successfully synthesized through supercritical water hydrothermal technique, in a batch type reactor. A Box–Behnken three-level experimental design was used to optimize the process variables a?ecting the BiFeO3 e?ciency includes pH of starting solution (1.5–12.5), reaction time (1–2 h), and reaction temperature (450–550 ℃). The samples were characterized via X–ray powder di?raction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The model was validated by analysis of variance (ANOVA) and conducting an experiment at optimal design conditions (temperature of 522 ℃, pH of 3.25 and 1.3 h). The maximum BiFeO3 production e?ciency which obtained at optimum condition was about 45%. The attained results showed good correlation between the predicted model and experimental data (Model P-Value = 0.0052). The present work con?rmed that the supercritical water hydrothermal method is a suitable way to produce BiFeO3 nanoparticles with a mean grain size of 60 nm and narrow size distribution. Moreover, the optical property of the product was investigated by Ultraviolet-visible di?use re?ectance spectroscopy (DRS). The attained nanostructures showed a narrow band gap of 1.96 eV, indicating that BiFeO3 powders can be applied as a novel visible-light-responsive photocatalyst for degradation of tetracycline (TC). Photocatalytic experiments revealed that using BiFeO3 nanoparticles, TC degradation e?ciency of 80.3% and 87.5% could be reached under UV and visible light radiations, respectively. Furthermore, it was found the degradation of TC follows the pseudo-second-order kinetics by BiFeO3.
关键词： Tetracycline,Bismuth ferrite nanoparticles,Photocatalyst,Supercritical water,Hydrothermal synthesis
更新于2025-09-23 15:19:57
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Dielectric and thermal behavior of 0.75BiFeO3-0.25BaTiO3 filled ethylene vinyl acetate Composites
摘要： Bismuth ferrite-Barium Titanate (BFO-BT) filled ethylene-vinyl acetate copolymer (EVA) composites have been processed by solution casting technique followed by compression molding. The effects of BFO-BT on structural, thermal and dielectric behaviour of the composites have been investigated using X-ray diffraction, field emission scanning electron microscopy, thermal analysis (DSC, TGA) and impedance analyser. As analysed by XRD and DSC analyses, with increase in BFO-BT content the crystallinity of EVA matrix decreases. BFO-BT has great effect on higher thermal stability of the composites. EVA/ BFO-BT composites exhibit significantly enhanced relative dielectric permittivity (εr =182) near the percolation limit of about 30 phr BFO-BT loading at 25° C and 1kHz frequency. With 30 phr BFO-BT loading, the dielectric loss of the composite shows only an approximately 2-fold increase i.e., from 0.04 to 0.091. The capacitance and resistance of grains is found from the exploratory Nyquist plots with the assistance of an electrical circuit. A cautious examination of the experimental complex impedance plots and model fitted plots is contemplated which fulfilled the precision of the information tentatively. With enhanced dielectric properties and thermal stability, the BFO-BT filled EVA composite system can be used for solar cells and energy saving devices.
关键词： Composites,Nyquist plots,Dielectric,Conductivity,Ethylene Vinyl Acetate,Bismuth Ferrite-Barium Titanate
更新于2025-09-12 10:27:22
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Oxygen‐vacancy‐controlled magnetic properties with magnetic pole inversion in BiFeO <sub/>3</sub> ‐based multiferroics
摘要： Oxygen vacancies which are generally present in ferrite oxide may significantly affect their magnetic properties. A comprehensive understanding of the relationship between oxygen vacancies and magnetism is of great importance. In this work, we report an oxygen vacancy concentration dependence of magnetism in a single‐phase multiferroic BiFeO3 (BFO)‐based system. The BiFeO3‐DyFeO3 (BDFO) solid solution is synthesized with controlled oxygen vacancies and is characterized by X‐ray powder diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), and AC impedance spectroscopy. The magnetic properties, especially magnetic pole inversion, are found to be highly dependent on oxygen vacancy concentration. The oxygen vacancies generate a Weiss molecular field on the Dy3+ ions in the magnetic field range of 570‐1000 Oe depending on the oxygen vacancy concentration, and result in a residual net magnetization by breaking the balance between the two nearly antiparallel spin lattices of Fe3+ ions. This work demonstrates an effective way to control oxygen vacancies and thereby the magnetic properties and sheds light on the relationship between oxygen vacancies and magnetism in BFO‐based multiferroics.
关键词： oxygen vacancies,bismuth ferrite BiFeO3,magnetic pole inversion
更新于2025-09-11 14:15:04
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Structural, bulk permittivity and impedance spectra of electronic material: Bi(Fe0.5La0.5)O3
摘要： In the present paper, fabrication and characterization (structural, electrical and ferroelectric properties) of a lead-free lanthanum (La) modified bismuth ferrite electroceramic having composition Bi(Fe0.5La0.5)O3 (BFLO) using various experimental techniques have been reported. BFLO has been synthesized by means of a high-temperature inter-diffusion of oxides method. This investigation mainly aims to correlate the phase formation and physical properties while the Fe-site of bismuth ferrite has partially been replaced by La. The surface micrograph shows the formation of the high dense ceramic sample. Analysis of data of various complex spectroscopies related to modulus and impedance exhibits the relaxation mechanism in this sample is of non-Debye type. The combined effect of grains and grain boundaries has been depicted from the Nyquist plot through the least-squares fitting of suitable circuit model along with the experimental data. The remnant polarization and coercive field decreases as temperature rises which was discerned from the ferroelectric loop obtained at different temperatures. The existence of ferroelectric nature in the sample was postulated from the polarization versus electric field plot.
关键词： Ferroelectric properties,Non-Debye relaxation,Lanthanum modification,Bismuth ferrite,Electroceramic
更新于2025-09-10 09:29:36