Rare earth metal ferrites-based heterojunctions have garnered significant attention in recent years due to their exceptional photocatalytic properties and potential applications in water treatment and energy conversio...Rare earth metal ferrites-based heterojunctions have garnered significant attention in recent years due to their exceptional photocatalytic properties and potential applications in water treatment and energy conversion.The incorporation of rare earth metal ferrites into heterojunction photocatalytic systems enhances light absorption,charge separation and photocatalytic efficiency.This review comprehensively discusses some common types of rare earth metal ferrites such as LaFeO_(3),GdFeO_(3),SmFeO_(3),PrFeO_(3)and CeFeO_(3)and their properties as photocatalysts.The photocatalytic pollutants removal and energy conversion mechanisms are discussed in detail and various types of heterojunctions reported in literature based on rare earth metal ferrites and their synthetic routes are also explored.The recent key findings and advances in the heterojunctions based on these rare earth metal ferrites for the pollutants removal and energy conversion applications are summarized.Despite notable progress in enhancing photocatalytic efficiency and stability,several challenges remain.Current research highlights improvements in material synthesis and performance,but issues such as high production costs,scalable synthesis and limited long-term stability persist.Future directions should focus on exploring uncharted applications,novel material combinations and enhancing the practical implementation of these heterojunctions to fully exploit their potential in environmental and energy technologies.展开更多
Rare earth(RE)doped ferrites with the chemical formula Cu_(0.3)Zn_(0.3)Mg_(0.4)T_(x)Fe_(2-x)O_(4)(x=0,0.1;T=La,Ce,Sr)were synthesized by chemical co-precipitation method.The structural,optical,electrical and humidity ...Rare earth(RE)doped ferrites with the chemical formula Cu_(0.3)Zn_(0.3)Mg_(0.4)T_(x)Fe_(2-x)O_(4)(x=0,0.1;T=La,Ce,Sr)were synthesized by chemical co-precipitation method.The structural,optical,electrical and humidity sensing properties of Cu-Mg-Zn ferrites with rare earth element doping were investigated.Single-phase cubic spinel structure was confirmed via X-ray diffraction(XRD),and the crystal size ranges fro m 22.12 to 63.17 nm according to the Scherrer formula and from 25.66 to 67.46 nm according to the Williamson-Hall method.Po rous structure and elemental characterization of the samples were investigated by scanning electron microscopy(SEM).The optic band gap varies between 2.21 and 2.49 eV.Electrical measurements were conducted in the frequency range of 1 Hz-20 MHz and temperature range of 25-400℃.It has been determined that the dielectric results are consistent with the Maxwell-Wagner method and exhibit a non-Debye relaxation model,as observed from the Nyquist plots.At a minimum frequency value of 1 Hz,the dielectric constants for pure,Ce,Sr,and La samples are 9×10^(4),5×10^(4),1×10^(8),and 2×10^(5) at 25℃,and 1.85×10^(8),1.34×10^(8),1.15×10^(10),and 4.4×10^(8)at 400℃.In the same order,for the maximum frequency value of 20 MHz,the dielectric constants at 25℃are 169,166,3799,and 60,while at 400℃they are 734,624,12108,and 774.The La doped sample's low dielectric loss makes it suitable for high-frequency applications.Humidity measurements were performed at room temperature and in the 5%-95%relative humidity range.The humidity properties of the samples were investigated through humidity mapping,sensitivity,hysteresis,and long-term stability tests.Compared to other samples,the results indicate that Ce exhibits better humidity performance with 99%sensitivity and the highest repeatability(91.2%).These results show that Ce-doped ferrite can be used as a low-cost,high-performance humidity sensor.展开更多
W-type barium-nickel ferrite(BaNi_(2)Fe_(16)O_(27))is a highly promising material for electromagnetic wave(EMW)absorption be-cause of its magnetic loss capability for EMW,low cost,large-scale production potential,high...W-type barium-nickel ferrite(BaNi_(2)Fe_(16)O_(27))is a highly promising material for electromagnetic wave(EMW)absorption be-cause of its magnetic loss capability for EMW,low cost,large-scale production potential,high-temperature resistance,and excellent chemical stability.However,the poor dielectric loss of magnetic ferrites hampers their utilization,hindering enhancement in their EMW-absorption performance.Developing efficient strategies that improve the EMW-absorption performance of ferrite is highly desired but re-mains challenging.Here,an efficient strategy substituting Ba^(2+)with rare earth La^(3+)in W-type ferrite was proposed for the preparation of novel La-substituted ferrites(Ba_(1-x)LaxNi_(2)Fe_(15.4)O_(27)).The influences of La^(3+)substitution on ferrites’EMW-absorption performance and the dissipative mechanism toward EMW were systematically explored and discussed.La^(3+)efficiently induced lattice defects,enhanced defect-induced polarization,and slightly reduced the ferrites’bandgap,enhancing the dielectric properties of the ferrites.La^(3+)also enhanced the ferromagnetic resonance loss and strengthened magnetic properties.These effects considerably improved the EMW-absorption perform-ance of Ba_(1-x)LaxNi_(2)Fe_(15.4)O_(27)compared with pure W-type ferrites.When x=0.2,the best EMW-absorption performance was achieved with a minimum reflection loss of-55.6 dB and effective absorption bandwidth(EAB)of 3.44 GHz.展开更多
Copper-zinc-nickel(Cu-Zn-Ni)ferrite nanoparticles are used for wastewater treatment technology.However,low degradation efficiency and stability are two main issues that make them unsuitable for actual production needs...Copper-zinc-nickel(Cu-Zn-Ni)ferrite nanoparticles are used for wastewater treatment technology.However,low degradation efficiency and stability are two main issues that make them unsuitable for actual production needs.In this paper,the citrate-nitrate auto-combustion method was applied for the formation of Cu_(0.5)Zn_(0.25)Ni_(0.25)La_(x)Fe_(2-x)O_(4);(0≤x≤0.1;step 0.02)(CZNL)nanoferrites.Although the substitution process entails the replacement of a small ion with a larger one,the lattice constant and crystallite size does not exhibit a consistent incremental pattern.This behavior is justified and discussed.The size of all the CZNL ferrite nanoparticles is in the range of 8-12 nm,and the lattice constant is in the range of 8.6230 to 8.4865 nm.The morphological analysis conducted using field emission-scanning electron microscopy(FE-SEM)reveals that the CZNL exhibits agglomerated spherical morphology.The energy dispersive X-ray spectrameter(EDAX)analysis was employed to confirm the elemental composition of CZNL nanoferrites.Since the process entails the substitution of Fe^(3+)magnetic ions with nonmagnetic ions La^(3+),the magnetic parameters of CZNL nanoferrites show a general decreasing trend as predicted.At 20 K,saturation magnetization Ms shows an overall drop in its values from 59.302 emu/g at x=0.0-41.295 emu/g at x=0.1,the smallest value of 37.87 emu/g is recorded at x=0.06.the highest coercivity(H_(c)=125.9 Oe)and remanence(M_(r)=13.32 emu/g)are recorded for x=0.08 and x=0.04 nanoferrite,respectvely.The band gap of all the CZNL nanoferrites was determined using the Kubelka-Munk function and Tauc plot for direct permitted transitions.La doping modifies the band gap(within 1.86-1.75 eV),increases light absorption,induces efficient e/h separation and charge migration to Cu_(0.5)Zn_(0.25)Ni_(0.25)La_(x)Fe_(2-x)O_(4)surfaces.The nanoferrite Cu_(0.5)Zn_(0.25)Ni_(0.25)La_(0.06)Fe_(1.94)O_(4)achieves a degradation efficiency of 97.3%for methylene blue(MB)dye removal after just 60 min.After five recycling processes,the nanocatalyst Cu_(0.5)Zn_(0.25)Ni_(0.25)La_(0.06)Fe_(1.94)O_(4)is degraded by 95.83%,resulting in a negligible1.51%decrease in photocatalytic activity efficiency.The new Cu_(0.5)Zn_(0.25)Ni_(0.25)La_(0.06)Fe_(1.94)O_(4)has exceptional photocatalytic activity and remarkable stability,making it a promising candidate for applications in wastewater treatment.展开更多
Nanoferrites of the CoMn_(x)Fe_(2-x)O_(4) series(x=0.00,0.05,0.10,0.15,0.20)were synthesized in this study using the sol-gel auto-combustion approach.The lattice constants were computed within the range of 8.312-8.406...Nanoferrites of the CoMn_(x)Fe_(2-x)O_(4) series(x=0.00,0.05,0.10,0.15,0.20)were synthesized in this study using the sol-gel auto-combustion approach.The lattice constants were computed within the range of 8.312-8.406Å,while crystallite sizes were estimated to range between 55.20 and 31.40 nm using the Scherrer method.The different functional groups were found to correlate with various ab-sorption bands using Fourier transform infrared(FTIR)spectroscopy.Five active modes were identified by Raman spectroscopy,reveal-ing vibration modes of O2-ions at tetrahedral and octahedral locations.The ferromagnetic hysteresis loop was observed in all the synthes-ized samples,which can be explained by Neel’s model.The results showed that AC conductivity decreased with increasing Mn^(2+)content at the Fe^(2+)site,while the dielectric constant and dielectric loss increased with increasing frequency.Furthermore,the saturation magnetiz-ation(Ms),remnant magnetization(M_(r)),and coercivity(H_(c))all showed declining trends with the increase in Mn^(2+)doping.Finally,the CoMn_(0.20)Fe_(1.8)O_(4) samples showed Ms and M_(r) values ranging from 73.12 to 66.84 emu/g and from 37.77 to 51.89 emu/g,respectively,while Hc values ranged from 1939 to 1312 Oe,after which coercivity increased.Thus,the CoMn_(0.20)Fe_(1.8)O_(4) sample can be considered a prom-ising candidate for magnetic applications.展开更多
The intrinsic high magnetocrystalline anisotropy equivalent field can help the hexaferrites break through Snoek’s limit and increase the resonance frequency.This is advantageous for microwave absorption applications ...The intrinsic high magnetocrystalline anisotropy equivalent field can help the hexaferrites break through Snoek’s limit and increase the resonance frequency.This is advantageous for microwave absorption applications in the mid to low-frequency range of gigahertz.In this study,we prepared Z-type Ba_(3)Co_(1.6−x)Zn_(x)Cu_(0.4)Fe_(24)O_(41)hexaferrites using the sol-gel auto-combustion method.By changing the ratio of Co and Zn ions,the magnetocrystalline anisotropy of ferrite is further ma-nipulated,resulting in significant changes in their magnetic resonance frequency and intensity.Ba_(3)Zn_(1.6)Cu_(0.4)Fe_(24)O_(41)with high-frequency resonance achieved the lowest reflectivity of−72.18 dB at 15.56 GHz,while Ba_(3)Co_(1.5)Zn_(0.1)Cu_(0.4)Fe_(24)O_(41)with stronger loss obtained the widest bandwidth of 4.93 GHz(6.14-11.07).Additionally,we investigated surface wave suppression properties previously overlooked.Ba_(3)Co_(1.5)Zn_(0.1)Cu_(0.4)Fe_(24)O_(41)can achieve a larger attenuation at low frequency under low thickness,which has an excellent effect on reducing backscattering.This work provides a useful reference for the preparation and application of high-performance magnetic-loss materials.展开更多
Spinel cubic ferrites have huge applications in me mory and high frequency devices.For the improvement of these modern devices,the magnetic coercivity,permeability,and dielectric properties of a ferrite are the import...Spinel cubic ferrites have huge applications in me mory and high frequency devices.For the improvement of these modern devices,the magnetic coercivity,permeability,and dielectric properties of a ferrite are the important issues.This article focuses on improving the magnetic coercivity,magnetic permeability,and dielectric properties of Co_(0.2)Zn_(0.3)Ni_(0.5)Eu_(x)Fe_(2-x)O_(4) ferrites,where x=0.00,0.06,and 0.10.The X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),field emission scanning electron microscopy(FESEM),energy dispersive X-ray(EDX),vibrating sample magnetometer(VSM),and an impedance analyzer were used to characterize the structural,magnetic,and dielectric properties of the samples.The XRD patterns indicate the formation of spinel cubic structure of the samples with a secondary peak(EuFeO_(3))for Eu doped samples.The densities and porosities of the samples follow an inverse trend,where the doped samples’lattice parameters are increased with the increment of rare earth Eu concentration.The FTIR analysis also proves the spinel cubic phase of the samples.The average grain size of the ferrites is obtained via FESEM images,and it is increased from 121 to 198 nm.VSM analysis confirms that doping of the Eu content also changes other hysteresis loop properties of Co_(0.2)Zn_(0.3)Ni_(0.5)Eu_(x)Fe_(2-x)O_(4) ferrites.Particularly,the coercivity of the Eu doped samples is greater than that of the mother alloy(x=0.00).The EDX study shows that there is no impurity contamination in the ferrites.The permeability and dielectric measurements show an improved quality factor of the Eu-doped samples with low magnetic and dielectric losses.Frequency dependent resistivity and impedance analysis also show the improved nature.From the observed properties of the samples,all the investigated ferrites might be strong candidates for potential applications in memory devices,magnetic sensors,and high frequency applications.展开更多
Nanoparticles anchored on the perovskite surface have gained considerable attention for their wide-ranging applications in heterogeneous catalysis and energy conversion due to their robust and integrated structural co...Nanoparticles anchored on the perovskite surface have gained considerable attention for their wide-ranging applications in heterogeneous catalysis and energy conversion due to their robust and integrated structural configuration.Herein,we employ controlled Co doping to effectively enhance the nanoparticle exsolution process in layered perovskite ferrites materials.CoFe alloy nanoparticles with ultra-high-density are exsolved on the(PrBa)_(0.95)(Fe_(0.8)Co_(0.1)Nb_(0.1))2O_(5+δ)(PBFCN_(0.1))surface under reducing atmosphere,providing significant amounts of reaction sites and good durability for hydrocarbon catalysis.Under a reducing atmosphere,cobalt facilitates the reduction of iron cations within PBFCN_(0.1),leading to the formation of CoFe alloy nanoparticles.This formation is accompanied by a cation exchange process,wherein,with the increase in temperature,partial cobalt ions are substituted by iron.Meanwhile,Co doping significantly enhance the electrical conductivity due to the stronger covalency of the Cosingle bondO bond compared with Fesingle bondO bond.A single cell with the configuration of PBFCN_(0.1)-Sm_(0.2)Ce_(0.8)O_(1.9)(SDC)|SDC|Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3−δ)(BSCF)-SDC achieves an extremely low polarization resistance of 0.0163Ωcm^(2)and a high peak power density of 740 mW cm^(−2)at 800℃.The cell also shows stable operation for 120 h in H_(2)with a constant current density of 285 mA cm^(−2).Furthermore,employing wet C_(2)H_(6)as fuel,the cell demonstrates remarkable performance,achieving peak power densities of 455 mW cm^(−2)at 800℃and 320 mW cm^(−2)at 750℃,marking improvements of 36%and 70%over the cell with(PrBa)_(0.95)(Fe_(0.9)Nb_(0.1))_(2)O_(5+δ)(PBFN)-SDC at these respective temperatures.This discovery emphasizes how temperature influences alloy nanoparticles exsolution within doped layered perovskite ferrites materials,paving the way for the development of high-performance ceramic fuel cell anodes.展开更多
Lanthanum doped nickel-cobalt nano ferrites with chemical formula Ni_(0.5)Co_(0.5)LaxFe_(2-x)O_(4)(x=0.05,0,10,0.15 and 0,20) were prepared using a simple sol-gel auto combustion method.The basic structural properties...Lanthanum doped nickel-cobalt nano ferrites with chemical formula Ni_(0.5)Co_(0.5)LaxFe_(2-x)O_(4)(x=0.05,0,10,0.15 and 0,20) were prepared using a simple sol-gel auto combustion method.The basic structural properties were determined by X-ray diffraction method and the formation of single phased spinel ferrite was confirmed.The crystalline size decreased from 25 to 11 nm and lattice parameter a increases with increase of La doping.The surface morphology of these ferrites was observed by field-emission scanning electron microscopy(FESEM) and agglomerated irregular grains are observed with increase of the rare earth element La doping.Energy-dispersive X-ray spectroscopy(EDX) result confirms the presence of the required elements.The Fourier transform infrared spectroscopy(FTIR) spectrum indicates the formation of the spinel ferrite structure with M-O bonds.Optical direct band measurements from ultraviolet-visible spectroscopy(UV-Vis) spectroscopy indicate that the direct band gap decreases from 1.39 to 1.19 eV for x=0.05 to x=0.15,then increases to 1.28 eV for x=0.20.The room temperature magnetic properties of these ferrites were studied by a vibrating sample magnetometer(VSM).The enhanced saturation magnetization of 49.73 emu/g is observed for x=0.10 and then saturation magnetizations are gradually decreased for x=0.15 and x=0.20.Interestingly the remanent magnetization and coercivity also follow the same trend.展开更多
Perovskite-type rare-earth ferrites(REFeO_(3))are promising materials for absorbing electromagnetic(EM)wave pollution.However,insufficient dielectric loss and poor impedance matching are key factors that limit the bro...Perovskite-type rare-earth ferrites(REFeO_(3))are promising materials for absorbing electromagnetic(EM)wave pollution.However,insufficient dielectric loss and poor impedance matching are key factors that limit the broader implementation of REFeO_(3).Herein,a series of multicomponent perovskite-type ferrites with strong EM wave absorption capabilities was prepared.Through the synergistic effect of chemical constitution regulation and entropy regulation,optimization of the dielectric loss and impedance matching is achieved by strengthening the structural defect mechanism,thus further adjusting the EM wave absorption performance.Compared with(LaGdSmNdBa)FeO_(3)(HE-1)and(LaGdPrSmNdBa)FeO_(3)(HE-2),(LaGdBa)FeO_(3)(ME-1)and(LaGdSmBa)FeO_(3)(ME-2)exhibit favorable performance,with optimal minimum reflection loss(RL_(min))of-56.35 dB(at 11.12 GHz)and-63.25 dB(at 7.22 GHz)and effective absorption bandwidth(EAB)of 4.46 and 4.72 GHz,respectively.This multicomponent design provides a new strategy for the development of EM wave absorption materials.展开更多
In current research work,Dy3+substituted Mg0.5Cu0.25Co0.25Fe2-xDyxO4(0.0≤x≤0.04 with the step interval of 0.01)soft ferrites were synthesized by the sol-gel auto combustion method.The prepared samples were character...In current research work,Dy3+substituted Mg0.5Cu0.25Co0.25Fe2-xDyxO4(0.0≤x≤0.04 with the step interval of 0.01)soft ferrites were synthesized by the sol-gel auto combustion method.The prepared samples were characterized by the techniques using X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS),Fourier transform infrared(FTIR)spectroscopy,curre nt-voltage(Ⅰ-Ⅴ)measurement,LCR meter,vibrating sample magnetometer(VSM)and Raman.XRD data reveal that the average crystallite size is 49.71 nm and the lattice constant is 0.83703 nm for sample x=0.03.The non-uniform grain growth was demonstrated by micrographs and impurity-free elemental composition was observed from EDX analysis.The DC resistivity has an increasing and decreasing trend in ferromagnetic and paramagnetic regions with an increase in temperature.Moreover,the high resistivity is observed with the order of 1010Ω·cm,and the activation energy is 0.944 eV for samples x=0.03.The dielectric parameters including dielectric constant,dielectric losses,and impedance gradually decrease with the increase in frequency from 8 Hz to 8 MHz.The minimum dielectric loss at high frequency is found for sample x=0.03.The coercivity(Hc)and saturation magnetization(Ms)are found in the ranges of 520.82-544.02 Oe and 20.5841-21.1473 emu/g,respectively.These observations confirm that dysprosium(x=0.03)doped MCC-soft ferrites may be applicable in transformer cores,microwave absorbance,and telecommunication devices.展开更多
Spinel ferrites exhibit exceptional magnetic properties,making them a distinctive class of magnetic materials.The sol-gel technique was utilized for the synthesis of spinel ferrites with the chemical formula Co_(0.6)S...Spinel ferrites exhibit exceptional magnetic properties,making them a distinctive class of magnetic materials.The sol-gel technique was utilized for the synthesis of spinel ferrites with the chemical formula Co_(0.6)Sr_(0.4)Ce_(x)Fe_(2-x)O_(4). Following that,a comprehensive X-ray diffraction analysis unveiled the crystalline cubic structure of the synthesized materials.Through the utilization of the M-H loop approach,the ferromagnetic attributes of ferrites were assessed,and the assimilation of rare earth elements led to substantial enhancements in saturation magnetization,remanence,and coercivity.Spinel ferrites with a high concentration of rare earth elements have improved direct current resistivity and activation energy.The logarithm of a material's resistance increased from 5.29 to 8.12 Ω·cm as cerium is added.With a change in the amount of cerium,the activation energy goes up from 0.19 to 0.29.By changing the frequency from 5.5 to 9.5 GHz,the dielectric characteristics were determined.As the frequency goes up,the dielectric constant goes down.Spinel ferrites that have been made better in every way can be used in high-frequency applications.展开更多
Preparation of electromagnetic(EM)wave-absorbing composites by interface engineering has been the main strategy to obtain high-performance absorbers.However,the conventional strategy is tedious and time-consuming,whic...Preparation of electromagnetic(EM)wave-absorbing composites by interface engineering has been the main strategy to obtain high-performance absorbers.However,the conventional strategy is tedious and time-consuming,which hinders the scalable synthesis of stable EM wave-absorbing composites.Herein,interface engineering by a redox reaction between transition metal elements in Co-based spinel ferrites was employed to create EM wave-absorbing composites to solve the above problem.Among serial M Co_(2)O_(4)(M=Ni,Cu,and Zn)spinel ferrites,redox reactions during synthesis only occurred between Cu and Co elements,thus leading to the presence of multiple crystal phases on final samples.With the aid of increased polyethylene glycol(PEG)molecular weight(MW),more heterogenous interfaces between CuO and CuCo_(2)O_(4)phases as well as induced crystal defects were generated.Under synergetic interface engineering by means of PEG-assisted redox reaction,interfacial polarization,and defect-induced polarization loss were markedly enhanced on a CuCo_(2)O_(4)-based sample that was prepared with PEG MW of 100 K.The effective absorption bandwidth of the corresponding sample could reach 6.48 GHz(11.52–18 GHz)with a thickness of 2.28 mm.In short,this work provides a novel strategy for designing EM wave absorbing composites by interface engineering through redox reaction instead of the conventional composition coupling process.展开更多
In this study, a series of Gd^(3+)-doped mixed Ni-Cu-Zn ferrites with composition of Zn_(0.5)Ni_(0.3)Cu_(0.2)Fe_(2-x)Gd_(x)O_(4)(x = 0, 0.025, 0.05, 0.075, 0.1) was prepared using self-ignition sol-gel method. The pre...In this study, a series of Gd^(3+)-doped mixed Ni-Cu-Zn ferrites with composition of Zn_(0.5)Ni_(0.3)Cu_(0.2)Fe_(2-x)Gd_(x)O_(4)(x = 0, 0.025, 0.05, 0.075, 0.1) was prepared using self-ignition sol-gel method. The prepared nanoparticles with an average size ranging from 22 to 26 nm show a single-phase cubic structure belonging to the spinel matrix. A rise in the Gd^(3+)concentration leads to an increase in crystallite size and lattice parameter. In Fourier transform infrared spectra, two main absorption bands belonging to the spinel structure are observed. The high-frequency bands(v_(1)) represent the tetrahedral complex, while the lowfrequency bands(v_(2)) signify the octahedral complex. The optical bandgap of the nanoferrites is found within the range of 2.91 to 2.41 eV, depending on their size. The magnetic characteristics of the material,such as saturation magnetization and coercivity are significantly altered with the concentration of Gd^(3+)in the solution. Using Rhodamine B(RhB) as a model organic pollutant, an in-depth investigation of the photocatalytic activity of the compounds was carried out. The present outcomes show that adding an adequate amount of Gd^(3+)significantly enhances the number of hydroxyl radicals produced by the ferrite,in turn, increasing the photocatalytic activity of the material. Mechanism elucidated by scavenger studies reveals that ·OH and holes are the primary reactive radicals responsible for the degradation process.Prepared photocatalysts show an insignificant performance loss in five consecutive cycles. Thus, it is concluded that these photocatalysts are highly suitable for the remediation of dye-contaminated wastewater.展开更多
In recent years,increased discharge of toxic effluents into water bodies has severely harmed ecosystems and human well-being.Various techniques are employed to remove contaminants,among which photocatalysis have prove...In recent years,increased discharge of toxic effluents into water bodies has severely harmed ecosystems and human well-being.Various techniques are employed to remove contaminants,among which photocatalysis have proven to be the most environment friendly and effective technique.This review focuses on MgFe_(2)O_(4),an exceptional photocatalyst owing to their small band gap,spherical shape,magnetic respon-sivity,stability,reusability,cost-effectiveness and small crystallite size.We have covered comprehensive comparison of research studies from the past decade to assess.Magnesium ferrite’s photocatalytic potential in pure,doped,and composite forms.Along with synthesis methods,degradation mechanisms,and shortcomings explained in detail.Furthermore,we have highlighted the enhanced photocatalytic capability of doped MgFe_(2)O_(4)and their nanocomposites towards the various organic contaminants upon visible light irradiation under a comparatively short period of time.Factors like cation distribution,dosage,pH,as well as methods for recovery and reuse are discussed to aid in production of more efficient photocatalysts.There has been a lack of information on the techniques that can be used to overcome the various shortcomings of MgFe_(2)O_(4)ferrite.Hence,we have accentuated on bringing forth such advanced techniques that would aid in driving the researchers’attention towards the practical and industrial application of the hybrid MgFe_(2)O_(4)nanoparticles.Lastly,the research gaps and industrial need of MgFe_(2)O_(4)ferrite-based materials were addressed to offer a concise view.展开更多
The La-Co substituted Sr1–xLaxFe12–xCoxO19 (x=0–0.5) ferrites with appropriate Bi2O3 additive were prepared by conventional sintering method and microwave sintering method at low sintering temperatures compatible w...The La-Co substituted Sr1–xLaxFe12–xCoxO19 (x=0–0.5) ferrites with appropriate Bi2O3 additive were prepared by conventional sintering method and microwave sintering method at low sintering temperatures compatible with LTCC (low temperature co-fired ceramics) systems, and their sintering behavior was chiefly investigated, including the crystal structure, saturation magnetizationMs, magnetic anisotropy fieldHa, intrinsic coercivityHci, and Curie temperatureTC. Experiment results clearly showed that the pure M-type crystal phase was successfully obtained when the La-Co substitution amountx did not exceed 0.3. However, the single M-type phase structure transformed to multiphase structure with further increased x, where the M-type phase coexisted with the non-magnetic phase such asα-Fe2O3 phase, La2O3 phase, and LaCoO3 phase. Appropriate La-Co substitution improved theMs (>62 emu/g),Ha (>1400 kA/m), andHci (>320 kA/m) for the ferrites withx varying from 0.1 to 0.3, but theTC decreased with increasing substitution amount. More-over, the microwave sintered ferrites could provide largerHci and similarMs compared with the conventional sintered ferrites.展开更多
A series of Cu-substituted Ni_(0.5-x)Cu_xZn_(0.5)Fe_2O_4(x=0.12,0.16,0.20,0.24 and 0.28) spinel ferrites were prepared by conventional ceramic method to investigate the effects of Cu compositional variation on the str...A series of Cu-substituted Ni_(0.5-x)Cu_xZn_(0.5)Fe_2O_4(x=0.12,0.16,0.20,0.24 and 0.28) spinel ferrites were prepared by conventional ceramic method to investigate the effects of Cu compositional variation on the structure and dielectric properties.XRD patterns demonstrate that all the samples are crystallized in single-phase cubic spinel structure and the lattice constant increases with increasing Cu content.White grains observed by SEM are Cu-rich phase.The dielectric constant versus frequency curve displays a normal dielectric behavior of spinel ferrites.While the frequency dependence of dielectric loss tangent is found to be abnormal,exhibiting a peak at certain frequency for all Cu-substituted Ni-Zn ferrites.A maximum of the resistivity is observed at x=0.2 due to the decrease of hopping electrons between Fe^(2+) and Fe^(3+) in per unit volume,which is in contrast with the Cu content dependence of dielectric constant and dielectric loss.展开更多
To improve the performance of Ni-Zn ferrites for power field use,the influence of MnO2 additive on the properties of Ni-Zn ferrites was investigated by the conventional powder metallurgy.The results show that MnO2 doe...To improve the performance of Ni-Zn ferrites for power field use,the influence of MnO2 additive on the properties of Ni-Zn ferrites was investigated by the conventional powder metallurgy.The results show that MnO2 does not form a visible second phase in the doping mass fraction range of（0-2.0%）.The average grain size,sintering density and real permeability gradually decrease with the increase of the MnO2 content.And the DC resistivity continuously increases with the increase of MnO2 content.The saturation magnetization（magnetic moment in unit mass） first increases slightly when mass fraction of MnO2 is less than 0.4% MnO2,and then gradually decreases with increasing the MnO2 mass fraction due to the exchange interaction of the cations.When the excitation frequency is less than 1 MHz,the power loss（Pcv） continuously increases with increasing the MnO2 content due to the decrease of average grain size.However,when the excitation frequency exceeds 1 MHz,eddy current loss gradually becomes the predominant contribution to Pcv.And the sample with a higher resistivity favors a lower Pcv,except for the sample with 2.0% MnO2.The sample without additive has the best Pcv when worked at frequencies less than 1 MHz;and the sample with 1.6% MnO2 additive has the best Pcv when worked at frequencies higher than 1 MHz.展开更多
Sulfur in transportation fuels is a major source of air pollution. New strategies for the desulfurization of fuels have been explored to meet the urgent need to produce cleaner gasoline. Adsorptive desulfurization（AD...Sulfur in transportation fuels is a major source of air pollution. New strategies for the desulfurization of fuels have been explored to meet the urgent need to produce cleaner gasoline. Adsorptive desulfurization（ADS） is one of the most promising complementary and alternative methods. Herein,nanocrystalline ferrite adsorbents were synthesized from metal nitrates and urea using a microwave assisted combustion method. A series of ADS experiments were performed using a fixed‐bed reactor to evaluate the ADS reactivity over the ferrites, which was found to have the order MgFe2O4〉NiFe2O4〉CuZnFe2O4〉ZnFe2O4〉CoFe2O4. This effect is explained by the fact that the low degree of alloying of Mg‐Fe and the doped Mg increased the interaction between Fe and S compounds,leading to a significant improvement in the desulfurization capability of the adsorbent.Additionally, Mg can dramatically promote the decomposition of thiophene. X‐ray diffraction and Mosbauer spectroscopy were used to characterize the fresh, regenerated, and sulfided adsorbents.Although the ferrite adsorbents were partially sulfided to bimetallic sulfides during the adsorption process, they were successfully regenerated after calcining at 500 °C in air.展开更多
The La-Zn substituted SrM-type ferrites with the composition of Sr1-xLaxFe12-xZnxO19 （x=0-0.4） were prepared by self-propagating high-temperature synthesis （SHS）. The single SrM phase was detected by XRD in the as...The La-Zn substituted SrM-type ferrites with the composition of Sr1-xLaxFe12-xZnxO19 （x=0-0.4） were prepared by self-propagating high-temperature synthesis （SHS）. The single SrM phase was detected by XRD in the as-received samples by controlling the Fe contents in the reagents. The substitution of La^3＋and Zn^2＋ obviously increased the magnetic properties of the as-prepared samples. The maximum improvements of Br, Hcb and （BH）m were 14.4%, 15.3% and 30.7%, respectively compared with that of the samples without La-Zn substitution. Microstructure observation by SEM showed that the SHS method benefited forming the better particle features and achieving the higher Hcj in comparison with the traditional firing method.展开更多
文摘Rare earth metal ferrites-based heterojunctions have garnered significant attention in recent years due to their exceptional photocatalytic properties and potential applications in water treatment and energy conversion.The incorporation of rare earth metal ferrites into heterojunction photocatalytic systems enhances light absorption,charge separation and photocatalytic efficiency.This review comprehensively discusses some common types of rare earth metal ferrites such as LaFeO_(3),GdFeO_(3),SmFeO_(3),PrFeO_(3)and CeFeO_(3)and their properties as photocatalysts.The photocatalytic pollutants removal and energy conversion mechanisms are discussed in detail and various types of heterojunctions reported in literature based on rare earth metal ferrites and their synthetic routes are also explored.The recent key findings and advances in the heterojunctions based on these rare earth metal ferrites for the pollutants removal and energy conversion applications are summarized.Despite notable progress in enhancing photocatalytic efficiency and stability,several challenges remain.Current research highlights improvements in material synthesis and performance,but issues such as high production costs,scalable synthesis and limited long-term stability persist.Future directions should focus on exploring uncharted applications,novel material combinations and enhancing the practical implementation of these heterojunctions to fully exploit their potential in environmental and energy technologies.
基金supported by the Ondokuz Mayis University Project Number PYO.MUH.1901.21.001。
文摘Rare earth(RE)doped ferrites with the chemical formula Cu_(0.3)Zn_(0.3)Mg_(0.4)T_(x)Fe_(2-x)O_(4)(x=0,0.1;T=La,Ce,Sr)were synthesized by chemical co-precipitation method.The structural,optical,electrical and humidity sensing properties of Cu-Mg-Zn ferrites with rare earth element doping were investigated.Single-phase cubic spinel structure was confirmed via X-ray diffraction(XRD),and the crystal size ranges fro m 22.12 to 63.17 nm according to the Scherrer formula and from 25.66 to 67.46 nm according to the Williamson-Hall method.Po rous structure and elemental characterization of the samples were investigated by scanning electron microscopy(SEM).The optic band gap varies between 2.21 and 2.49 eV.Electrical measurements were conducted in the frequency range of 1 Hz-20 MHz and temperature range of 25-400℃.It has been determined that the dielectric results are consistent with the Maxwell-Wagner method and exhibit a non-Debye relaxation model,as observed from the Nyquist plots.At a minimum frequency value of 1 Hz,the dielectric constants for pure,Ce,Sr,and La samples are 9×10^(4),5×10^(4),1×10^(8),and 2×10^(5) at 25℃,and 1.85×10^(8),1.34×10^(8),1.15×10^(10),and 4.4×10^(8)at 400℃.In the same order,for the maximum frequency value of 20 MHz,the dielectric constants at 25℃are 169,166,3799,and 60,while at 400℃they are 734,624,12108,and 774.The La doped sample's low dielectric loss makes it suitable for high-frequency applications.Humidity measurements were performed at room temperature and in the 5%-95%relative humidity range.The humidity properties of the samples were investigated through humidity mapping,sensitivity,hysteresis,and long-term stability tests.Compared to other samples,the results indicate that Ce exhibits better humidity performance with 99%sensitivity and the highest repeatability(91.2%).These results show that Ce-doped ferrite can be used as a low-cost,high-performance humidity sensor.
基金financially supported by the National Key R&D Program of China(No.2021YFB3502500)the Natur-al Science Foundation of Shandong Province,China(No.2022HYYQ-014)+5 种基金the“20 Clauses about Colleges and Uni-versities(new)”(Independent Training of Innovation Team)Program of Jinan,China(No.2021GXRC036)the Provin-cial Key Research and Development Program of Shandong,China(No.2021ZLGX01)the National Natural Science Foundation of China(No.22375115)the Joint Laboratory project of Electromagnetic Structure Technology(No.637-2022-70-F-037)the Discipline Construction Expenditure for Distinguished Young Scholars of Shandong University,China(No.31370089963141)the Qilu Young Scholar Program of Shandong University,China(No.31370082163127).
文摘W-type barium-nickel ferrite(BaNi_(2)Fe_(16)O_(27))is a highly promising material for electromagnetic wave(EMW)absorption be-cause of its magnetic loss capability for EMW,low cost,large-scale production potential,high-temperature resistance,and excellent chemical stability.However,the poor dielectric loss of magnetic ferrites hampers their utilization,hindering enhancement in their EMW-absorption performance.Developing efficient strategies that improve the EMW-absorption performance of ferrite is highly desired but re-mains challenging.Here,an efficient strategy substituting Ba^(2+)with rare earth La^(3+)in W-type ferrite was proposed for the preparation of novel La-substituted ferrites(Ba_(1-x)LaxNi_(2)Fe_(15.4)O_(27)).The influences of La^(3+)substitution on ferrites’EMW-absorption performance and the dissipative mechanism toward EMW were systematically explored and discussed.La^(3+)efficiently induced lattice defects,enhanced defect-induced polarization,and slightly reduced the ferrites’bandgap,enhancing the dielectric properties of the ferrites.La^(3+)also enhanced the ferromagnetic resonance loss and strengthened magnetic properties.These effects considerably improved the EMW-absorption perform-ance of Ba_(1-x)LaxNi_(2)Fe_(15.4)O_(27)compared with pure W-type ferrites.When x=0.2,the best EMW-absorption performance was achieved with a minimum reflection loss of-55.6 dB and effective absorption bandwidth(EAB)of 3.44 GHz.
文摘Copper-zinc-nickel(Cu-Zn-Ni)ferrite nanoparticles are used for wastewater treatment technology.However,low degradation efficiency and stability are two main issues that make them unsuitable for actual production needs.In this paper,the citrate-nitrate auto-combustion method was applied for the formation of Cu_(0.5)Zn_(0.25)Ni_(0.25)La_(x)Fe_(2-x)O_(4);(0≤x≤0.1;step 0.02)(CZNL)nanoferrites.Although the substitution process entails the replacement of a small ion with a larger one,the lattice constant and crystallite size does not exhibit a consistent incremental pattern.This behavior is justified and discussed.The size of all the CZNL ferrite nanoparticles is in the range of 8-12 nm,and the lattice constant is in the range of 8.6230 to 8.4865 nm.The morphological analysis conducted using field emission-scanning electron microscopy(FE-SEM)reveals that the CZNL exhibits agglomerated spherical morphology.The energy dispersive X-ray spectrameter(EDAX)analysis was employed to confirm the elemental composition of CZNL nanoferrites.Since the process entails the substitution of Fe^(3+)magnetic ions with nonmagnetic ions La^(3+),the magnetic parameters of CZNL nanoferrites show a general decreasing trend as predicted.At 20 K,saturation magnetization Ms shows an overall drop in its values from 59.302 emu/g at x=0.0-41.295 emu/g at x=0.1,the smallest value of 37.87 emu/g is recorded at x=0.06.the highest coercivity(H_(c)=125.9 Oe)and remanence(M_(r)=13.32 emu/g)are recorded for x=0.08 and x=0.04 nanoferrite,respectvely.The band gap of all the CZNL nanoferrites was determined using the Kubelka-Munk function and Tauc plot for direct permitted transitions.La doping modifies the band gap(within 1.86-1.75 eV),increases light absorption,induces efficient e/h separation and charge migration to Cu_(0.5)Zn_(0.25)Ni_(0.25)La_(x)Fe_(2-x)O_(4)surfaces.The nanoferrite Cu_(0.5)Zn_(0.25)Ni_(0.25)La_(0.06)Fe_(1.94)O_(4)achieves a degradation efficiency of 97.3%for methylene blue(MB)dye removal after just 60 min.After five recycling processes,the nanocatalyst Cu_(0.5)Zn_(0.25)Ni_(0.25)La_(0.06)Fe_(1.94)O_(4)is degraded by 95.83%,resulting in a negligible1.51%decrease in photocatalytic activity efficiency.The new Cu_(0.5)Zn_(0.25)Ni_(0.25)La_(0.06)Fe_(1.94)O_(4)has exceptional photocatalytic activity and remarkable stability,making it a promising candidate for applications in wastewater treatment.
文摘Nanoferrites of the CoMn_(x)Fe_(2-x)O_(4) series(x=0.00,0.05,0.10,0.15,0.20)were synthesized in this study using the sol-gel auto-combustion approach.The lattice constants were computed within the range of 8.312-8.406Å,while crystallite sizes were estimated to range between 55.20 and 31.40 nm using the Scherrer method.The different functional groups were found to correlate with various ab-sorption bands using Fourier transform infrared(FTIR)spectroscopy.Five active modes were identified by Raman spectroscopy,reveal-ing vibration modes of O2-ions at tetrahedral and octahedral locations.The ferromagnetic hysteresis loop was observed in all the synthes-ized samples,which can be explained by Neel’s model.The results showed that AC conductivity decreased with increasing Mn^(2+)content at the Fe^(2+)site,while the dielectric constant and dielectric loss increased with increasing frequency.Furthermore,the saturation magnetiz-ation(Ms),remnant magnetization(M_(r)),and coercivity(H_(c))all showed declining trends with the increase in Mn^(2+)doping.Finally,the CoMn_(0.20)Fe_(1.8)O_(4) samples showed Ms and M_(r) values ranging from 73.12 to 66.84 emu/g and from 37.77 to 51.89 emu/g,respectively,while Hc values ranged from 1939 to 1312 Oe,after which coercivity increased.Thus,the CoMn_(0.20)Fe_(1.8)O_(4) sample can be considered a prom-ising candidate for magnetic applications.
基金supported by the National Natural Science Foundation of China(No.62371222)the Defense Industrial Technology Development Program(No.JCKY2023605C002)thePriority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)and the Opening Project of Science and Technology on Reliability Physics and Application Technology of Electronic Component Laboratory(No.ZHD202305).
文摘The intrinsic high magnetocrystalline anisotropy equivalent field can help the hexaferrites break through Snoek’s limit and increase the resonance frequency.This is advantageous for microwave absorption applications in the mid to low-frequency range of gigahertz.In this study,we prepared Z-type Ba_(3)Co_(1.6−x)Zn_(x)Cu_(0.4)Fe_(24)O_(41)hexaferrites using the sol-gel auto-combustion method.By changing the ratio of Co and Zn ions,the magnetocrystalline anisotropy of ferrite is further ma-nipulated,resulting in significant changes in their magnetic resonance frequency and intensity.Ba_(3)Zn_(1.6)Cu_(0.4)Fe_(24)O_(41)with high-frequency resonance achieved the lowest reflectivity of−72.18 dB at 15.56 GHz,while Ba_(3)Co_(1.5)Zn_(0.1)Cu_(0.4)Fe_(24)O_(41)with stronger loss obtained the widest bandwidth of 4.93 GHz(6.14-11.07).Additionally,we investigated surface wave suppression properties previously overlooked.Ba_(3)Co_(1.5)Zn_(0.1)Cu_(0.4)Fe_(24)O_(41)can achieve a larger attenuation at low frequency under low thickness,which has an excellent effect on reducing backscattering.This work provides a useful reference for the preparation and application of high-performance magnetic-loss materials.
基金supported by the Research and Innovation Centre,Khulna University(KURC ID-47/2020)。
文摘Spinel cubic ferrites have huge applications in me mory and high frequency devices.For the improvement of these modern devices,the magnetic coercivity,permeability,and dielectric properties of a ferrite are the important issues.This article focuses on improving the magnetic coercivity,magnetic permeability,and dielectric properties of Co_(0.2)Zn_(0.3)Ni_(0.5)Eu_(x)Fe_(2-x)O_(4) ferrites,where x=0.00,0.06,and 0.10.The X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),field emission scanning electron microscopy(FESEM),energy dispersive X-ray(EDX),vibrating sample magnetometer(VSM),and an impedance analyzer were used to characterize the structural,magnetic,and dielectric properties of the samples.The XRD patterns indicate the formation of spinel cubic structure of the samples with a secondary peak(EuFeO_(3))for Eu doped samples.The densities and porosities of the samples follow an inverse trend,where the doped samples’lattice parameters are increased with the increment of rare earth Eu concentration.The FTIR analysis also proves the spinel cubic phase of the samples.The average grain size of the ferrites is obtained via FESEM images,and it is increased from 121 to 198 nm.VSM analysis confirms that doping of the Eu content also changes other hysteresis loop properties of Co_(0.2)Zn_(0.3)Ni_(0.5)Eu_(x)Fe_(2-x)O_(4) ferrites.Particularly,the coercivity of the Eu doped samples is greater than that of the mother alloy(x=0.00).The EDX study shows that there is no impurity contamination in the ferrites.The permeability and dielectric measurements show an improved quality factor of the Eu-doped samples with low magnetic and dielectric losses.Frequency dependent resistivity and impedance analysis also show the improved nature.From the observed properties of the samples,all the investigated ferrites might be strong candidates for potential applications in memory devices,magnetic sensors,and high frequency applications.
基金supported by National Natural Science Foundation of China Project (Grant No. 52374133, 52262034)the Guangdong Basic and Applied Basic Research Committee Foundation (Grant No. KCXST20221021111601003)Shenzhen Science and Technology Innovation Commission Foundation (Grant No. KCXST20221021111601003)
文摘Nanoparticles anchored on the perovskite surface have gained considerable attention for their wide-ranging applications in heterogeneous catalysis and energy conversion due to their robust and integrated structural configuration.Herein,we employ controlled Co doping to effectively enhance the nanoparticle exsolution process in layered perovskite ferrites materials.CoFe alloy nanoparticles with ultra-high-density are exsolved on the(PrBa)_(0.95)(Fe_(0.8)Co_(0.1)Nb_(0.1))2O_(5+δ)(PBFCN_(0.1))surface under reducing atmosphere,providing significant amounts of reaction sites and good durability for hydrocarbon catalysis.Under a reducing atmosphere,cobalt facilitates the reduction of iron cations within PBFCN_(0.1),leading to the formation of CoFe alloy nanoparticles.This formation is accompanied by a cation exchange process,wherein,with the increase in temperature,partial cobalt ions are substituted by iron.Meanwhile,Co doping significantly enhance the electrical conductivity due to the stronger covalency of the Cosingle bondO bond compared with Fesingle bondO bond.A single cell with the configuration of PBFCN_(0.1)-Sm_(0.2)Ce_(0.8)O_(1.9)(SDC)|SDC|Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3−δ)(BSCF)-SDC achieves an extremely low polarization resistance of 0.0163Ωcm^(2)and a high peak power density of 740 mW cm^(−2)at 800℃.The cell also shows stable operation for 120 h in H_(2)with a constant current density of 285 mA cm^(−2).Furthermore,employing wet C_(2)H_(6)as fuel,the cell demonstrates remarkable performance,achieving peak power densities of 455 mW cm^(−2)at 800℃and 320 mW cm^(−2)at 750℃,marking improvements of 36%and 70%over the cell with(PrBa)_(0.95)(Fe_(0.9)Nb_(0.1))_(2)O_(5+δ)(PBFN)-SDC at these respective temperatures.This discovery emphasizes how temperature influences alloy nanoparticles exsolution within doped layered perovskite ferrites materials,paving the way for the development of high-performance ceramic fuel cell anodes.
文摘Lanthanum doped nickel-cobalt nano ferrites with chemical formula Ni_(0.5)Co_(0.5)LaxFe_(2-x)O_(4)(x=0.05,0,10,0.15 and 0,20) were prepared using a simple sol-gel auto combustion method.The basic structural properties were determined by X-ray diffraction method and the formation of single phased spinel ferrite was confirmed.The crystalline size decreased from 25 to 11 nm and lattice parameter a increases with increase of La doping.The surface morphology of these ferrites was observed by field-emission scanning electron microscopy(FESEM) and agglomerated irregular grains are observed with increase of the rare earth element La doping.Energy-dispersive X-ray spectroscopy(EDX) result confirms the presence of the required elements.The Fourier transform infrared spectroscopy(FTIR) spectrum indicates the formation of the spinel ferrite structure with M-O bonds.Optical direct band measurements from ultraviolet-visible spectroscopy(UV-Vis) spectroscopy indicate that the direct band gap decreases from 1.39 to 1.19 eV for x=0.05 to x=0.15,then increases to 1.28 eV for x=0.20.The room temperature magnetic properties of these ferrites were studied by a vibrating sample magnetometer(VSM).The enhanced saturation magnetization of 49.73 emu/g is observed for x=0.10 and then saturation magnetizations are gradually decreased for x=0.15 and x=0.20.Interestingly the remanent magnetization and coercivity also follow the same trend.
基金Project supported by the National Key Research and Development Program of China(2022YFB3504302)the Young Elite Scientists Sponsorship Program by CAST(YESS20210336)+1 种基金the Fujian Provincial Natural Fund Project(2021J05101)the XIREM Autonomously Deployment Project(2023GG03)。
文摘Perovskite-type rare-earth ferrites(REFeO_(3))are promising materials for absorbing electromagnetic(EM)wave pollution.However,insufficient dielectric loss and poor impedance matching are key factors that limit the broader implementation of REFeO_(3).Herein,a series of multicomponent perovskite-type ferrites with strong EM wave absorption capabilities was prepared.Through the synergistic effect of chemical constitution regulation and entropy regulation,optimization of the dielectric loss and impedance matching is achieved by strengthening the structural defect mechanism,thus further adjusting the EM wave absorption performance.Compared with(LaGdSmNdBa)FeO_(3)(HE-1)and(LaGdPrSmNdBa)FeO_(3)(HE-2),(LaGdBa)FeO_(3)(ME-1)and(LaGdSmBa)FeO_(3)(ME-2)exhibit favorable performance,with optimal minimum reflection loss(RL_(min))of-56.35 dB(at 11.12 GHz)and-63.25 dB(at 7.22 GHz)and effective absorption bandwidth(EAB)of 4.46 and 4.72 GHz,respectively.This multicomponent design provides a new strategy for the development of EM wave absorption materials.
文摘In current research work,Dy3+substituted Mg0.5Cu0.25Co0.25Fe2-xDyxO4(0.0≤x≤0.04 with the step interval of 0.01)soft ferrites were synthesized by the sol-gel auto combustion method.The prepared samples were characterized by the techniques using X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS),Fourier transform infrared(FTIR)spectroscopy,curre nt-voltage(Ⅰ-Ⅴ)measurement,LCR meter,vibrating sample magnetometer(VSM)and Raman.XRD data reveal that the average crystallite size is 49.71 nm and the lattice constant is 0.83703 nm for sample x=0.03.The non-uniform grain growth was demonstrated by micrographs and impurity-free elemental composition was observed from EDX analysis.The DC resistivity has an increasing and decreasing trend in ferromagnetic and paramagnetic regions with an increase in temperature.Moreover,the high resistivity is observed with the order of 1010Ω·cm,and the activation energy is 0.944 eV for samples x=0.03.The dielectric parameters including dielectric constant,dielectric losses,and impedance gradually decrease with the increase in frequency from 8 Hz to 8 MHz.The minimum dielectric loss at high frequency is found for sample x=0.03.The coercivity(Hc)and saturation magnetization(Ms)are found in the ranges of 520.82-544.02 Oe and 20.5841-21.1473 emu/g,respectively.These observations confirm that dysprosium(x=0.03)doped MCC-soft ferrites may be applicable in transformer cores,microwave absorbance,and telecommunication devices.
基金the Deanship of Scientific Research at King Khalid University for funding this work through the large group research project under grant number (RGP2/82/44)。
文摘Spinel ferrites exhibit exceptional magnetic properties,making them a distinctive class of magnetic materials.The sol-gel technique was utilized for the synthesis of spinel ferrites with the chemical formula Co_(0.6)Sr_(0.4)Ce_(x)Fe_(2-x)O_(4). Following that,a comprehensive X-ray diffraction analysis unveiled the crystalline cubic structure of the synthesized materials.Through the utilization of the M-H loop approach,the ferromagnetic attributes of ferrites were assessed,and the assimilation of rare earth elements led to substantial enhancements in saturation magnetization,remanence,and coercivity.Spinel ferrites with a high concentration of rare earth elements have improved direct current resistivity and activation energy.The logarithm of a material's resistance increased from 5.29 to 8.12 Ω·cm as cerium is added.With a change in the amount of cerium,the activation energy goes up from 0.19 to 0.29.By changing the frequency from 5.5 to 9.5 GHz,the dielectric characteristics were determined.As the frequency goes up,the dielectric constant goes down.Spinel ferrites that have been made better in every way can be used in high-frequency applications.
基金supported by the National Natural Science Foundation of China(No.22372074)the Yunnan Fundamental Research Projects(No.202101AV070008)+2 种基金the Major Basic Research Project of Science and Technology of Yunnan(No.202302AG050007)Yunnan Innovation Team of Graphene Mechanism Research and Application Industrialization(No.202305AS350017)Graphene Application and Engineering Research Center of Education Department of Yunnan Providence(No.KKPP202351001).
文摘Preparation of electromagnetic(EM)wave-absorbing composites by interface engineering has been the main strategy to obtain high-performance absorbers.However,the conventional strategy is tedious and time-consuming,which hinders the scalable synthesis of stable EM wave-absorbing composites.Herein,interface engineering by a redox reaction between transition metal elements in Co-based spinel ferrites was employed to create EM wave-absorbing composites to solve the above problem.Among serial M Co_(2)O_(4)(M=Ni,Cu,and Zn)spinel ferrites,redox reactions during synthesis only occurred between Cu and Co elements,thus leading to the presence of multiple crystal phases on final samples.With the aid of increased polyethylene glycol(PEG)molecular weight(MW),more heterogenous interfaces between CuO and CuCo_(2)O_(4)phases as well as induced crystal defects were generated.Under synergetic interface engineering by means of PEG-assisted redox reaction,interfacial polarization,and defect-induced polarization loss were markedly enhanced on a CuCo_(2)O_(4)-based sample that was prepared with PEG MW of 100 K.The effective absorption bandwidth of the corresponding sample could reach 6.48 GHz(11.52–18 GHz)with a thickness of 2.28 mm.In short,this work provides a novel strategy for designing EM wave absorbing composites by interface engineering through redox reaction instead of the conventional composition coupling process.
文摘In this study, a series of Gd^(3+)-doped mixed Ni-Cu-Zn ferrites with composition of Zn_(0.5)Ni_(0.3)Cu_(0.2)Fe_(2-x)Gd_(x)O_(4)(x = 0, 0.025, 0.05, 0.075, 0.1) was prepared using self-ignition sol-gel method. The prepared nanoparticles with an average size ranging from 22 to 26 nm show a single-phase cubic structure belonging to the spinel matrix. A rise in the Gd^(3+)concentration leads to an increase in crystallite size and lattice parameter. In Fourier transform infrared spectra, two main absorption bands belonging to the spinel structure are observed. The high-frequency bands(v_(1)) represent the tetrahedral complex, while the lowfrequency bands(v_(2)) signify the octahedral complex. The optical bandgap of the nanoferrites is found within the range of 2.91 to 2.41 eV, depending on their size. The magnetic characteristics of the material,such as saturation magnetization and coercivity are significantly altered with the concentration of Gd^(3+)in the solution. Using Rhodamine B(RhB) as a model organic pollutant, an in-depth investigation of the photocatalytic activity of the compounds was carried out. The present outcomes show that adding an adequate amount of Gd^(3+)significantly enhances the number of hydroxyl radicals produced by the ferrite,in turn, increasing the photocatalytic activity of the material. Mechanism elucidated by scavenger studies reveals that ·OH and holes are the primary reactive radicals responsible for the degradation process.Prepared photocatalysts show an insignificant performance loss in five consecutive cycles. Thus, it is concluded that these photocatalysts are highly suitable for the remediation of dye-contaminated wastewater.
文摘In recent years,increased discharge of toxic effluents into water bodies has severely harmed ecosystems and human well-being.Various techniques are employed to remove contaminants,among which photocatalysis have proven to be the most environment friendly and effective technique.This review focuses on MgFe_(2)O_(4),an exceptional photocatalyst owing to their small band gap,spherical shape,magnetic respon-sivity,stability,reusability,cost-effectiveness and small crystallite size.We have covered comprehensive comparison of research studies from the past decade to assess.Magnesium ferrite’s photocatalytic potential in pure,doped,and composite forms.Along with synthesis methods,degradation mechanisms,and shortcomings explained in detail.Furthermore,we have highlighted the enhanced photocatalytic capability of doped MgFe_(2)O_(4)and their nanocomposites towards the various organic contaminants upon visible light irradiation under a comparatively short period of time.Factors like cation distribution,dosage,pH,as well as methods for recovery and reuse are discussed to aid in production of more efficient photocatalysts.There has been a lack of information on the techniques that can be used to overcome the various shortcomings of MgFe_(2)O_(4)ferrite.Hence,we have accentuated on bringing forth such advanced techniques that would aid in driving the researchers’attention towards the practical and industrial application of the hybrid MgFe_(2)O_(4)nanoparticles.Lastly,the research gaps and industrial need of MgFe_(2)O_(4)ferrite-based materials were addressed to offer a concise view.
基金supported by the National Public Welfare Fund Industry Research(201410026)Scientific Research Foundation of Education Office of Sichuan Province(13Z198)the Young and Middle-aged Academic Leaders of Scientific Research Funds of Chengdu University of Information Technology(J201222)
文摘The La-Co substituted Sr1–xLaxFe12–xCoxO19 (x=0–0.5) ferrites with appropriate Bi2O3 additive were prepared by conventional sintering method and microwave sintering method at low sintering temperatures compatible with LTCC (low temperature co-fired ceramics) systems, and their sintering behavior was chiefly investigated, including the crystal structure, saturation magnetizationMs, magnetic anisotropy fieldHa, intrinsic coercivityHci, and Curie temperatureTC. Experiment results clearly showed that the pure M-type crystal phase was successfully obtained when the La-Co substitution amountx did not exceed 0.3. However, the single M-type phase structure transformed to multiphase structure with further increased x, where the M-type phase coexisted with the non-magnetic phase such asα-Fe2O3 phase, La2O3 phase, and LaCoO3 phase. Appropriate La-Co substitution improved theMs (>62 emu/g),Ha (>1400 kA/m), andHci (>320 kA/m) for the ferrites withx varying from 0.1 to 0.3, but theTC decreased with increasing substitution amount. More-over, the microwave sintered ferrites could provide largerHci and similarMs compared with the conventional sintered ferrites.
基金Project(M26012)supported by the Foundation of National Laboratory of Solid State Microstructures,China
文摘A series of Cu-substituted Ni_(0.5-x)Cu_xZn_(0.5)Fe_2O_4(x=0.12,0.16,0.20,0.24 and 0.28) spinel ferrites were prepared by conventional ceramic method to investigate the effects of Cu compositional variation on the structure and dielectric properties.XRD patterns demonstrate that all the samples are crystallized in single-phase cubic spinel structure and the lattice constant increases with increasing Cu content.White grains observed by SEM are Cu-rich phase.The dielectric constant versus frequency curve displays a normal dielectric behavior of spinel ferrites.While the frequency dependence of dielectric loss tangent is found to be abnormal,exhibiting a peak at certain frequency for all Cu-substituted Ni-Zn ferrites.A maximum of the resistivity is observed at x=0.2 due to the decrease of hopping electrons between Fe^(2+) and Fe^(3+) in per unit volume,which is in contrast with the Cu content dependence of dielectric constant and dielectric loss.
基金Projects(50702011,60721001)supported by the National Natural Science Foundation of China
文摘To improve the performance of Ni-Zn ferrites for power field use,the influence of MnO2 additive on the properties of Ni-Zn ferrites was investigated by the conventional powder metallurgy.The results show that MnO2 does not form a visible second phase in the doping mass fraction range of（0-2.0%）.The average grain size,sintering density and real permeability gradually decrease with the increase of the MnO2 content.And the DC resistivity continuously increases with the increase of MnO2 content.The saturation magnetization（magnetic moment in unit mass） first increases slightly when mass fraction of MnO2 is less than 0.4% MnO2,and then gradually decreases with increasing the MnO2 mass fraction due to the exchange interaction of the cations.When the excitation frequency is less than 1 MHz,the power loss（Pcv） continuously increases with increasing the MnO2 content due to the decrease of average grain size.However,when the excitation frequency exceeds 1 MHz,eddy current loss gradually becomes the predominant contribution to Pcv.And the sample with a higher resistivity favors a lower Pcv,except for the sample with 2.0% MnO2.The sample without additive has the best Pcv when worked at frequencies less than 1 MHz;and the sample with 1.6% MnO2 additive has the best Pcv when worked at frequencies higher than 1 MHz.
基金supported by the National Natural Science Foundation of China(2137303821403026+2 种基金and 21476232)the China Postdoctoral Science Foundation(2015T80255 and 2014M551068)the China-Egypt Scientific-Technologic Exchange Project(21311140474)~~
文摘Sulfur in transportation fuels is a major source of air pollution. New strategies for the desulfurization of fuels have been explored to meet the urgent need to produce cleaner gasoline. Adsorptive desulfurization（ADS） is one of the most promising complementary and alternative methods. Herein,nanocrystalline ferrite adsorbents were synthesized from metal nitrates and urea using a microwave assisted combustion method. A series of ADS experiments were performed using a fixed‐bed reactor to evaluate the ADS reactivity over the ferrites, which was found to have the order MgFe2O4〉NiFe2O4〉CuZnFe2O4〉ZnFe2O4〉CoFe2O4. This effect is explained by the fact that the low degree of alloying of Mg‐Fe and the doped Mg increased the interaction between Fe and S compounds,leading to a significant improvement in the desulfurization capability of the adsorbent.Additionally, Mg can dramatically promote the decomposition of thiophene. X‐ray diffraction and Mosbauer spectroscopy were used to characterize the fresh, regenerated, and sulfided adsorbents.Although the ferrite adsorbents were partially sulfided to bimetallic sulfides during the adsorption process, they were successfully regenerated after calcining at 500 °C in air.
基金Project supported by the Key Project for Science and Technology of Zhejiang Province
文摘The La-Zn substituted SrM-type ferrites with the composition of Sr1-xLaxFe12-xZnxO19 （x=0-0.4） were prepared by self-propagating high-temperature synthesis （SHS）. The single SrM phase was detected by XRD in the as-received samples by controlling the Fe contents in the reagents. The substitution of La^3＋and Zn^2＋ obviously increased the magnetic properties of the as-prepared samples. The maximum improvements of Br, Hcb and （BH）m were 14.4%, 15.3% and 30.7%, respectively compared with that of the samples without La-Zn substitution. Microstructure observation by SEM showed that the SHS method benefited forming the better particle features and achieving the higher Hcj in comparison with the traditional firing method.
