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Temperature-dependent photo-response in multiferroic BiFeO 3 revealed by transmission measurements
摘要： We studied the light-induced effects in BiFeO3 single crystals as a function of temperature by means of optical spectroscopy. Here, we report the observation of several light-induced absorption features, which are discussed in terms of the photostriction effect and are interpreted in terms of excitons. The temperature dependence of their energy position suggests a possible coupling between the excitons and the lattice vibrations. Moreover, there are hints for anomalies in the temperature evolution of the excitonic features, which might be related to the temperature-induced magnetic phase transitions in BiFeO3. Our findings suggest a coupling between light-induced excitons and the lattice and spin degrees of freedom, which might be relevant for the observed ultrafast photostriction effect in multiferroic BiFeO3.
关键词： multiferroic,excitons,optical spectroscopy,BiFeO3,photostriction
更新于2025-11-25 10:30:42
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Photocatalytic and Photo-Fenton Catalytic Degradation Activities of Z-Scheme Ag2S/BiFeO3 Heterojunction Composites under Visible-Light Irradiation
摘要： Z-scheme Ag2S/BiFeO3 heterojunction composites were successfully prepared through a precipitation method. The morphology and microstructure characterization demonstrate that Ag2S nanoparticles (30–50 nm) are well-decorated on the surfaces of polyhedral BiFeO3 particles (500–800 nm) to form Ag2S/BiFeO3 heterojunctions. The photocatalytic and photo-Fenton catalytic activities of the as-derived Ag2S/BiFeO3 heterojunction composites were evaluated by the degradation of methyl orange (MO) under visible-light irradiation. The photocatalytic result indicates that the Ag2S/BiFeO3 composites exhibit much improved photocatalytic activities when compared with bare Ag2S and BiFeO3. The optimum composite sample was observed to be 15% Ag2S/BiFeO3 with an Ag2S mass fraction of 15%. Furthermore, the addition of H2O2 can further enhance the dye degradation efficiency, which is due to the synergistic effects of photo- and Fenton catalysis. The results of photoelectrochemical and photoluminescence measurements suggest a greater separation of the photoexcited electron/hole pairs in the Ag2S/BiFeO3 composites. According to the active species trapping experiments, the photocatalytic and photo-Fenton catalytic mechanisms of the Ag2S/BiFeO3 composites were proposed and discussed.
关键词： polyhedral BiFeO3 particles,photo-Fenton catalysis,Ag2S nanoparticles,photocatalysis,Z-scheme Ag2S/BiFeO3 heterojunction
更新于2025-11-19 16:46:39
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Facile Synthesis and Enhanced Visible-Light Photocatalytic Activity of Novel p-Ag3PO4/n-BiFeO3 Heterojunction Composites for Dye Degradation
摘要： In this work, Ag3PO4 microparticles were decorated onto the surface of BiFeO3 microcuboids through a precipitation method to obtain p-Ag3PO4/n-BiFeO3 heterojunction composites. The composites were employed for the degradation of acid orange 7 (AO7) under visible-light irradiation. It is found that the composites exhibit much higher photocatalytic efficiency than bare BiFeO3. Meanwhile, the intrinsical visible-light-driven photocatalytic activity of Ag3PO4/BiFeO3 composites was further confirmed by the degradation of phenol. In addition, the photo-Fenton-like catalysis property of the composite was also evaluated. The photocurrent analysis indicates that the combination of BiFeO3 with Ag3PO4 leads to the inhibition of recombination of photoinduced electrons and holes. The obvious enhancement in the photocatalytic activity of the composite is mainly ascribed to the efficient photogenerated charge separation and interfacial charge migration caused by the formation of Ag3PO4/BiFeO3 p-n heterojunctions.
关键词： BiFeO3,Photocatalysis,Heterojunction,Ag3PO4
更新于2025-11-19 16:46:39
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Enhanced breakdown strength and energy storage density in a new BiFeO3-based ternary lead-free relaxor ferroelectric ceramic
摘要： A new ternary lead-free relaxor ferroelectric ceramic of (0.67-x)BiFeO3-0.33(Ba0.8Sr0.2)TiO3-xLa(Mg2/3Nb1/3)O3+y wt.% MnO2+z wt.% BaCu(B2O5) (BF-BST-xLMN+y wt.% MnO2+z wt.% BCB) was prepared by a solid-state reaction method. The substitution of LMN for BF was believed to induce a typical dielectric relaxation behavior owing to the increased random fields. After co-doping MnO2 and BCB, a significant decrease in the conductivity and grain size was simultaneously realized, resulting in obviously enhanced dielectric breakdown strength and energy-storage performances at room temperature. A high recoverable energy storage density W~3.38 J/cm3 and an acceptable energy storage efficiency η~59% were achieved in the composition with x=0.06, y=0.1 and z=2 under a measuring electric field of 23 kV/mm. In addition, the energy-storage performance is quite stable against both frequency (0.1 Hz-100 Hz) and temperature (30-170 oC), suggesting that BF-BST-xLMN+y wt.% MnO2+z wt.% BCB lead-free relaxor ferroelectric ceramics might be a promising dielectric material for high-power pulsed capacitors.
关键词： Lead-free ceramics,Relaxor ferroelectrics,Energy storage,BiFeO3,BDS
更新于2025-11-14 17:28:48
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High electrostrain with high Curie temperature in BiFeO3-BaTiO3-based ceramics
摘要： Here, we report a high unipolar electrostrain (0.45%) with a high Curie temperature (TC = 410 °C) in lead-free (1-x)(0.67BiFeO3–0.33BaTiO3)-xSr0.8La0.1□0.1TiO2.95 (□ represents the A-site vacancy) piezoceramics with x = 0.02. Sr0.8La0.1□0.1TiO2.95 was introduced to construct a relaxor ferroelectric state. The obtained unipolar strain was thermally stable, and the variation from room temperature to 100 °C was only 10%. Systematic electromechanical and Raman spectra measurements revealed a composition driven phase transition from classical ferroelectric to relaxor ferroelectric phases and distorted internal stress field. This work provides a novel strategy to obtain high electrostrain in high temperature piezoceramics.
关键词： Electrostrain,BiFeO3-based ceramics,High TC,Vacancy
更新于2025-11-14 17:28:48
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Enhanced visible-light-driven photocatalytic activity of BiFeO3 via electric-field control of spontaneous polarization
摘要： Well-polarized BiFeO3 nanoparticles have been successfully prepared by a facile electrical poling method with the assist of a soluble organic-inorganic composite film. From XRD, TEM and SEM studies, no significant change in the crystal structure or morphology was detected after the electrical poling process. The visible-light driven photocatalytic process of poled BiFeO3 nanoparticles was accelerated by 2 times compared to unpoled BiFeO3. By combining time-resolved photoluminescence (PL), photoinduced silver deposition testing and photoelectrochemical measurements, it can be revealed that the enhanced photocatalytic performance of poled samples can be properly attributed to the promoted separation and prolonged lifetime of the photogenerated carriers caused by the ferroelectric polarization. These findings may offer a new route to promote the photocatalytic or photoelectric performances of BiFeO3 for advanced applications by adjusting the ferroelectric polarization.
关键词： BiFeO3 nanoparticles,Organic-inorganic composite film,Ferroelectric polarization,Electrical poling technology,Photocatalytic activity
更新于2025-11-14 15:24:45
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Tuning Ferroelectric, Dielectric, and Magnetic Properties of BiFeO <sub/>3</sub> Ceramics by Ca and Pb Co-Doping
摘要： Effects of Ca/Pb co-doping on structure, ferroelectric, dielectric, and magnetic properties of BiFeO3 ceramics are investigated. A structure transition from a rhombohedral phase (space group R3c) to a cubic phase (space group Pm3m) with the increment of Ca/Pb concentration is revealed by X-ray diffraction and Raman spectra. In order to compensate the valence change caused by Ca2+ dopant, Pb ions present tetravalent state under the existence of Ca ions. The room-temperature ferroelectric behavior depends upon Ca/Pb co-doping and the structural transition in BiFeO3 ceramics. Meanwhile, the variation of the dielectric loss tangent in the frequency range of 102–107 Hz and the leakage current at room temperature illustrate that Ca/Pb co-doping increases resistivity and reduces leakage current. Compared with that of Sr/Pb co-doping, the co-doping of Ca/Pb has improved the leakage current by two orders of magnitude, besides further increasing the ferroelectric polarization and dielectric properties under the same co-doping concentration. In addition, enhanced ferromagnetism is observed with the increase of Ca/Pb content, which can be attributed to the effective suppression of spiral cycloidal spin structure and spin canting resulting from the structural transition.
关键词： BiFeO3,ferroelectricity,co-doping,dielectricity,ceramics,magnetism
更新于2025-09-23 15:23:52
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Ferroelectric enhanced photoelectrochemical water splitting in BiFeO3/TiO2 composite photoanode
摘要： A facile sol-gel methodology was used to synthesize single-phase BiFeO3 (BFO) film on TiO2 photoanode to improve photoelectrochemical (PEC) water-splitting efficiency. The BFO films with controllable thickness induced a considerable ferroelectric polarization under bias voltage, which effectively tuned the electric band bending of BFO/TiO2. The photocurrent density of the as-prepared BFO-5/TiO2 could reach up to 11.25 mA/cm2, which is over 20 times higher than that of bare TiO2. Moreover, the positively poled BFO-5/TiO2 photoanode yielded a photocurrent density of 28.75 mA/cm2 at 1.5 V vs.SCE under AM 1.5G illumination. This work suggests that BFO/TiO2 with combined ferroelectric and semiconducting features could be a promising solution to improve PEC performance by concurrently promoting the light absorption and charge-separation and transportation properties.
关键词： BiFeO3,Ferroelectric polarization,Photoanode,Water-splitting
更新于2025-09-23 15:23:52
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Combined experimental and theoretical investigation on modulation of multiferroic properties in BiFeO3 ceramics induced by Dy and transition metals co-doping
摘要： Multiferroic Dy and transition metals (Cr, Mn, Ni) co-doped BiFeO3 ceramics were successfully synthesized by a solid-state method, and the influence on the magnetic and ferroelectric properties were investigated. Compared with Bi0.95Dy0.05Fe0.95Mn0.05O3, Bi0.95Dy0.05Fe0.95Cr0.05O3 and Bi0.95Dy0.05Fe0.95Ni0.05O3 ceramics can significantly improve the magnetic properties. The significant enhancement of magnetic properties should be related to the local ferromagnetic coupling from Cr ions (Ni ions) and Fe ions, which have already been proved by first-principles calculations. Meanwhile, both experimental and theoretical studies reveal the Dy substitution can effectively enhance the ferroelectric properties of BiFeO3. Leakage current and conduction mechanism analyses reveal that the improved ferroelectric properties are mainly attributed to the reduced oxygen vacancies.
关键词： Magnetic property,Ferroelectric property,BiFeO3,Substitution
更新于2025-09-23 15:23:52
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Néel transition in the multiferroic BiFeO <sub/>3</sub> -0.25PbTiO <sub/>3</sub> nanoparticles with anomalous size effect
摘要： The role of size reduction on the structural parameters, antiferromagnetic transition temperature (TN), and spin reorientation transition temperature of BiFeO3-0.25PbTiO3 (BF-0.25PT) has been studied. Rietveld analysis using high resolution synchrotron x-ray powder diffraction data confirms that the space group of BF-0.25PT solid solutions is monoclinic Cc and not rhombohedral R3c for both bulk and nanocrystalline powders. This settles a longstanding controversy about the structure of these solid solutions toward the BiFeO3 rich end of the morphotropic phase boundary in the BiFeO3-xPbTiO3 system. Using magnetization and neutron powder diffraction data, we show that the Néel transition temperature (TN) of BF-0.25PT increases from 445 K for bulk to 480 K for 150 nm particle size. This is in marked contrast to the scaling theories of phase transitions in finite size systems. We also show that the spin reorientation transition occurring below TN in bulk monoclinic compositions like BF-0.25PT is suppressed in the nanocrystalline samples of ～150 nm particle size. Based on Rietveld refined structural parameters, we show that the asymmetry and non-linearity of the Fe-O-Fe superexchange pathways grow with decreasing particle size and that they exhibit a strong correlation with TN. We believe that the substantially enhanced Dzyaloshinskii-Moriya interaction with decreasing particle size as a result of asymmetric and non-collinear Fe-O-Fe superexchange pathways may be the key factor in raising the TN on decreasing the particle size. These observations present a new facet of type-I multiferroic materials, where superexchange pathways are intimately dependent on the ferroelectric distortion.
关键词： multiferroic,antiferromagnetic transition,BiFeO3-PbTiO3,size effect,Dzyaloshinskii-Moriya interaction,Néel transition,nanoparticles
更新于2025-09-23 15:23:52