Synthesis and Structural Properties of Bismuth Doped Cobalt Nanoferrites Prepared by Sol-Gel Combustion Method

A series of Bismuth doped Cobalt nanoferrites of chemical composition CoBixFe2-xO4 (where x = 0.00, 0.05, 0.10, 0.15, 0.20 & 0.25) were prepared by sol-gel combustion method and calcinated at 600℃. The structural and morphological studies were carried out by using X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive Spectroscopy (EDS) and Fourier Transform Infrared (FT-IR) spectra showing the single phase spinal structure. The X-ray diffraction (XRD) analysis confirmed a single phase fcc crystal. The crystallite size of all the compositions was calculated using Debye-Scherrer equation and found in the range of 17 to 26 nm. The lattice parameters were found to be decreased as Bi3+ ion doping increases. The surface morphology was studied by Scanning Electron Microscope (SEM) and particle size was confirmed by Transmission Electron Microscopy (TEM). The EDS plots revealed existence of no extra peaks other than constituents of the taken up composition. The Fourier Transform Infrared (FT-IR) studies were made in the frequency range 350 - 900 cm-1 and observed two strong absorption peaks. The frequency band is found at 596 cm-1 where as the lower frequency band at 393 cm-1. It is clearly noticed that the two prominent absorption bands were slightly shifted towards higher frequency side with the increase of Bi3+ ion concentration.

Structural and Magnetic Properties of Cr-Co Nanoferrite Particles

Nano-crystalline CrxCoFe2–xO4 (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) ferrites were synthesized by sol-gel method. The X-ray diffraction patterns of all the samples provide information about the existence of single phase spinel structure. The SEM and TEM micrographs show the uniform particle distribution and SAED pattern represents the polycrystalline nature of the resultant ferrite nano-particles. High purity of the sample is confirmed by energy dispersive X-ray analysis. The FTIR spectra show two strong absorption bands in the range of 600 - 400 cm–1, which confirm the presence of M-O stretching band in ferrites. The magnetic properties of the synthesized samples were investigated by using vibrating sample magnetometer at room temperature. According to VSM reports the main magnetic parameters like saturation magnetization (Ms), coercivity (Hc) were found to decrease with the substitution of Cr3+ content. Possible mechanisms which are responsible for the results are scrutinized minutely in this paper.

乙酰胺-尿素-NaBr熔体中Gd-Co合金膜的电沉积研究

利用循环伏安法和恒电位电解法探讨了 3 5 3K时乙酰胺 尿素 (2 6.7% ,质量分数 ) NaBr(12 .0 % ,质量分数 )熔体体系中Gd Co合金膜的电化学制备。研究了沉积时的电流密度、时间、温度以及Gd(Ⅲ ) /Co(Ⅱ )浓度比对沉积膜质量的影响。结果表明 ,在乙酰胺 尿素 (2 6.7% ) NaBr(12 .0 % )熔体中 ,控制恰当的体系组成和沉积条件 ,均可得到表面均匀、附着力强、有金属光泽的灰黑色非晶态Gd Co合金膜 ,其中Gd的质量分数可达 4.92 %～ 85 .89% ,所得到的沉积膜通过SEM ,EDS和XRD进行了分析。

Gd-Co二元非晶及晶态合金的磁性和大磁热效应

通过熔体快淬制备了Gd59Co41、Gd56Co44非晶条带,并对Gd56Co44非晶条带进行588K、10min的晶化处理。利用X射线衍射仪(XRD)分析了合金的结构,通过综合物性测量系统(PPMS)研究了合金的磁性及磁热效应。结果表明,Gd59Co41和Gd56Co44非晶条带的初始晶化温度分别为523和544K;Gd56Co44非晶条带晶化处理后获得了Ho4Co3型六方单相。非晶态和晶态合金在居里温度附近都发生铁磁到顺磁的二级相变。随着Gd/Co比例的降低,Gd59Co41和Gd56Co44非晶合金的居里温度(TC)从198K提高到217K;晶化处理后Gd56Co44合金的居里温度为218K,与非晶态合金相比变化甚微。在ΔH=5T时,Gd59Co41和Gd56Co44非晶合金的最大磁熵变(-ΔSM)和制冷能力(RC)分别为7.7J/kg·K、525J/kg和6.6J/kg·K、544J/kg;而Gd56Co44晶态合金的最大磁熵变(-ΔSM)和制冷能力(RC)分别为5.6J/kg·K和528J/kg。大的磁熵变和制冷能力,几乎可以忽略的矫顽力和热滞/磁滞效应,表明Gd-Co二元非晶和晶态系列合金是200K温区附近一类具有潜在应用价值的磁制冷工质。

Microstructure and magnetic properties of electrodeposited Gd-Co alloy films

Gd-Co alloy films were synthesized by potentiostatic electrolysis on Cu substrates in urea-acetamide-NaBr-KBr melt at 353 K. The electroreduction of Co^2＋ and Gd^3＋ was investigated by cyclic voltammetry. The reduction of Co^2＋ is an irreversible process. Gd^3＋ cannot be reduced alone, but it can be inductively co-deposited with Co^2＋. Both the Gd content and microstructure of the prepared Gd-Co alloy films can be controlled by the deposited potential. The content of Gd was analyzed using an inductively coupled plasma emission spectrometer （ICPES）, and the microstructure was observed by scanning electron micrograph （SEM）. The films were crystallized by heat-treatment at 823 K for 30 s in Ar atmosphere, and then were investigated by XRD. The hysteresis loops of the Gd-Co alloy films were measured by a vibrating sample magnetometer （VSM）. The experimental results reveal that the deposited Gd-Co alloy films are amorphous, while the annealing causes the samples to change from amorphous to polycrystalline, thus enhancing their magnetocrystalline anisotropy and coercivity. Moreover, the magnetic properties of the Gd-Co alloy films depend strongly on the Gd content.

Al的添加对Gd-Co合金的影响

用X射线衍射、扫描电镜和磁性测量等方法研究了Al的添加对Gd-Co合金的影响。研究结果表明:在一定范围内掺杂Al导致GdCo2、GdCo5和Gd2Co17晶格常数增大,但仍保持各自的晶体结构;Al的添加使GdCo5和Gd2Co17的居里温度降低,但是对于GdCo2却是先增后减。该结论为寻找新的磁性材料提供了有价值的参考。

Effect of Al Addition on the Glass-Forming Ability and Magnetic Properties of a Gd-Co Binary Amorphous Alloy

The glass-forming ability （CFA） and magnetic properties of the Cd50 Co50-based amorphous alloy with AI addition substitution for Co are investigated. It is found that the CFA and magneto-caloric effect of the Gd50Co45Al5 amorphous alloy are better than Cd50Co50 amorphous alloy. The maximum magnetic entropy change （-△ Sm^peak） and the magnetic refrigerant capacity- of the amorphous alloy under a field of 5 T are about 6.64 J·kg^-1 K^-1 and 764 J·kg^-1, respectively. The field dependence of magnetic entropy change meets the one predicted by the mean field theory, which is investigated for a better understanding of the magneto-caloric behaviors of the Gdso Co45Al5 amorphous alloy.

Sm^(3+)induced structural phase transition,spectral,morphological,magnetic,dielectric and impedance properties of Ni_(0.1)Cu_(0.9)Sm_(x)Fe_(2-x)O_(4) nanoferrites

In the present study,rare earth samarium(Sm^(3+))substituted Ni-Cu spinel ferrites with the composition of Ni_(0.1)Cu_(0.9)Sm_(x)Fe_(2-x)O_(4)(0≤x≤0.05 in steps of 0.01)were synthesized by using the citrate induced sol-gel auto combustion technique.These ferrites'structural,optical,magnetic,and dielectric studies were carried out using X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),field emission scanning electron microscopy(FESEM),ultraviolet-visible(UV-vis),a vibrational sample magnetometer(VSM),and an LCR meter.The pure Ni-Cu ferrite exhibits a tetragonal structure owing to the presence of the John Tellar ion(Cu^(2+)).XRD patterns confirm that the tetragonal structure gradually transforms into the cubic spinel structure with samarium substitution.The nano-scale structures of these ferrites were confirmed by the average crystallite size(10.11-20.99 nm)derived from the X-ray diffraction patterns,and grain size(42.60-83.36 nm)assessed from FESEM photographs.The existence of elements according to their chemical composition was verified by using energy dispersive X-ray(EDX)spectra.The absorption bands(v_(1) and v_(2))detected in FTIR transmission spectra below the wavenumber of 600 cm^(-1)reveal the stretching vibrations of M-O bonds in the spinel structure at tetrahedral and octahedral locations.The band gap ene rgy obtained from UV absorption reveals the semiconducting nature of the samples.The high saturation magnetization(M_(s))is noticed at 15 K temperature for x=0.02 composition as 32.98 emu/g,while at 300 K for x=0.01composition as 27.61 emu/g.The suggested cation distribution is in good agreement with observed and predicted magnetic moment values at 300 K.The expected behavior of ferrites reveals the observed dielectric constant,loss tangent,and ac-conductivity values in the frequency range of 20 Hz-20 MHz.Cole-Cole plots confirm that the impedance contribution is attributed to grain boundaries.

Y^(3+) substituting-adjusted mechanical,dielectric,and impedance properties of cobalt copper zinc nanoferrites for high frequency applications

Upgrading mechanical-dielectric features of ferrites through rare-earth yttrium(Y^(3+))doping provides feasibility to evolving high-frequency electronic devices.This paper reports the mechanical and dielectric properties of Co_(0.5)Cu_(0.25)Zn_(0.25)Y_(x)Fe_(2-x)O_(4)ferrite nanoparticles labeled as CCZYF#0,CCZYF#1,CCZYF#2,CCZYF#3,CCZYF#4 and CCZYF#5 for x=0.0.0.02,0.04,0.06,0.08,and 0.1,respectively.The frequency and temperature dependence of dielectric parameters and co nductivity of all CCZYF nanoferrites are well discussed.The nanoferrite CCZYF#5 has the highest dielectric constant(enhancing ratio 170%)and the highest conductivity(enhancing ratio 7125.81%)compared with the undoped sample.Nyquist plots of all CCZYF nano ferrites manifest two arcs;the main reasons for the dielectric process are the grain boundaries and bulk grains.All impedance parameters were determined,which showed the effective role of Y^(3+)ions on their values.The nanoferrite CCZYF#5 has the highest grain boundaries capacitance(with enhancing ratio of 59.40%)and the highest grains capacitance(with enhancing ratio of 22.53%)with a relaxation time decrement efficiency of 62.51%.An ultrasonic flaw detector was utilized to determine the elastic moduli of all CCZYF nanoferrites.The nanoferrite CCZYF#5 has the highest longitudinal modulus(with enhancing ratio of 20.95%),the highest shear modulus(with enhancing ratio of48.72%),highest Young's modulus(with enhancing ratio of 88.47%),the highest bulk modulus(with enhancing ratio 13.27%)and the highest micro hardness(with enhancing ratio 77.77%).Hence,Y3+tuned Co-Cu-Zn nanoferrites possess new opportunities for high-frequency and storage applications.

电磁吸波材料研究进展

阐述了常见的吸波材料种类及其特点,吸波材料的研究现状,重点介绍了纳米铁氧体吸波材料及其制备方法。笔者采用柠檬酸盐sol-gel法制得了均匀包覆铁氧体的空心微珠为基的复合材料,其吸波性能良好。最后指出吸波材料的发展趋势为纳米化、多元化和多介质化。

掺杂Co^(2+)和Sm^(3+)对纳米ZnFe_2O_4铁氧体的电磁损耗性质的影响

采用NaHCO3与FeCl3?6H2O,ZnSO4?7H2O,Co(NO3)2?6H2O和Sm(NO3)3?6H2O进行室温固相反应制得碱式碳酸盐和氢氧化铁混合前驱物,先微波加热,再热分解分别制得复合氧化物ZnFe2O4,Co0.5Zn0.5Fe2O4和Co0.5Zn0.5Fe1.95-Sm0.05O4.由激光粒度分析仪、XRD和SEM表征:获得了颗粒分布均匀、平均粒度为62nm左右的立方晶系尖晶石结构的纳米铁氧体粉体.并测试样品的相对介电常数和相对磁导率,研究了它们的电磁损耗特性.结果表明:在ZnFe2O4中,掺入Co2+,Sm3+元素可以在100～1800MHz测试频率范围内不同程度提高材料的电磁损耗特性.

Doping effect of rare-earth(lanthanum, neodymium and gadolinium) ions on structural,optical, dielectric and magnetic properties of copper nanoferrites

Copper and rare earth-doped(RE = La, Gd, Nd) CuFe1.85RE0.15O4nano ferrites were prepared using the so nochemical method. The effective doping of rare-earth(La3+, Nd3+, Gd3+) ions with copper nanoferrites was confirmed by X-ray diffraction. The tetrahedral and octahedral sites of the nano ferrites were identified through the Fourier transform infrared spectra. The doping of rare-earth elements enhances the optical bandgap energy of the nanoferrites that are observed through Ultraviolet-DRS spectra. The oxidation state of the elements Cu 2 p, La 3 d, Nd 3 d, Gd 3 d, Fe 2 p and O 1 s was analyzed. Scanning electron microscopy images indicate a spherical morphology with agglomeration to some elongate. The values of dielectric constant and conductivity decrease considerably due to doping rare-earth ions in copper nanoferrites. Low saturation magnetization and high coercivity values of rare earth-doped copper nanoferrites are observed from the typical hysteresis curves.

核壳结构纳米铁氧体复合材料的制备及其光催化活性的研究进展

综述了近十年来,核壳结构纳米铁氧体复合材料的制备及其光催化性能影响因素方面的研究成果,主要阐述了几种常见的核壳结构纳米铁氧体材料及其制备方法,探讨了壳层结构、厚度和热处理温度等因素对纳米铁氧体复合材料光催化性能的影响及相关机理,并对下一步的研究工作进行了展望。

Unique structural and magnetic traits of Nd3+-substituted Co-Zn nanoferrites

Because of the technological potential of magnetic spinel nanoferrites, we prepared neodymium ion(Nd3+)-substituted cobalt-zinc ferrites(CZFs) with the form Co0.5 Zn0.5 NdxFe2 exO4(0.03≤x≤0.05) via a hydrothermal method. The as-prepared samples were thoroughly characterized using various analytical techniques. XRD, FTIR and FESEM analyses confirm the formation of a cubic spinel phase of the CZFNPs(CZF nanoparticles). A decrease in the lattice parameter due to the substitution of Fe3+by Nd3+in the lattice structures is manifested in the XRD refinement data. The magnetic properties of the proposed CZFNPs were evaluated in terms of the saturation magnetization, remanence, coercivity, squareness ratio and magnetic moment. These CZFNPs exhibit superparamagnetic behaviors at room temperature.Moreover, the Nd3+inclusion does not significantly affect the measured magnetizations and coercivities of the CZFNPs. Samples containing 0.01 and 0.03 Nd3+exhibit lower saturation magnetizations than that of the pristine product. The squareness ratios much less than 0.53 are ascribed to surface spin disordering. The unique magnetic traits of the synthesized CZFNPs are primarily attributed to the substitution of Fe3+ions, with smaller ionic radii, by Nd3+ions, with larger ionic radii. The proposed CZFNPs may be useful for diverse magneto-optic applications.

Preparation and Characterization of MMT Doped PVA/SA Polymer Composites

Blends of PVA/SA polymer doped with Montmorillonite were prepared by solution casting technique. Doping of nanoparticles to the polymer matrix does affect the structural and conducting properties. To analyze such changes, these films were subjected to X-ray diffraction, FT-IR spectroscopy, UV-visible absorbance and impedance analysis. Microstructural parameters were computed using in-house program employing X-ray data. Electrical conductivity of these polymer composites was derived using obtained impedance values to understand the conducting property. The results thus obtained are reported in this work.

Traversing the advantageous role of samarium doped spinel nanoferrites for photocatalytic removal of organic pollutants

The present work reportes the pertinence of samarium(Sm) doped spinel nanoferrites as magnetically recoverable photocatalyst for the removal of organic pollutants from wastewater.Thus,a series of Sm substituted spinel nano ferrites,MSm_(x)Fe_(2-x)O_(4)(M=Ni,Co;x=0,0.02,0.06,0.1) we re synthesized via sol-gel methodology.The effect of Sm doping on the structural,morphological,optical and magnetic properties of pristine nanoferrites was investigated systematically.Further,the fabricated samples were explored as photocatalysts for the oxidative degradation of antibiotics(ofloxacin and norfloxacin) and dyes(methyl orange and safranin O).The Sm doped nanoferrites exhibit astonishing catalytic efficacy that can be attributed to higher surface area,octahedral site preference of Sm ions and reduced band gap.The synthesized nanoferrites display excellent recyclability which enables them to be utilized as potential photocatalysts for wastewater treatment.

Magnetic and Electrical Properties of Gd Doped Ni-Cu-Zn-Fe₂O₄

Ni0.5Cu0.25Zn0.25GdxFe2-xO4 (x = 0.0, 0.025, 0.05, 0.075, 0.1) ferrites were synthesized using an oxalic-based precursor method. The TC for all the Ni0.5Cu0.25Zn0.25GdxFe2-xO4 (x = 0.0, 0.025, 0.05, 0.075, 0.1) samples was measured by using one of the double coil susceptibility setup. In all the samples it is observed that, at a certain temperature, susceptibility falls to zero indicating the Curie temperature (TC) and ferrimagnetic samples are converted into paramagnetic sample at that temperature. The electrical properties were investigated for these samples. Dielectric properties and ρdc properties were observed to decrease with the increase in the frequency for all the Gd doped ferrite samples.

Ion Beam Analysis and Electric Properties of GdBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7-δ</SUB>Added with Nanosized Ferrites ZnFe<SUB>2</SUB>O<SUB>4</SUB>and CoFe<SUB>2</SUB>O<SUB>4</SUB>

In this study, superconducting samples of type GdBa2Cu3O7-δ added with x wt% (0 ≤ x ≤ 0.4) nanoferrites ZnFe2O4 and CoFe2O4 were prepared by the conventional solid-state reaction technique. The prepared samples were characterized using X-ray powder diffraction (XRD) in order to determine the volume fraction and lattice parameters. The elemental contents of the prepared samples were determined using particle induced X-ray emission (PIXE). In addition, the oxygen-content of these samples was obtained using non-Rutherford backscattering spectroscopy (RBS) at 3 MeV proton beam. It is found that the Oxygen-content of GdBa2Cu3O7-δ phase remains practically constant for low additions of both nanoferrites but it increases with high additions. The electrical resistivity of the prepared samples was measured by the conventional four-probe technique from room temperature down to the zero superconducting transition temperature (T0). An increase in the superconducting transition temperature Tc and the critical current density Jc is observed as x varies from 0.0 to 0.06 wt% of (ZnFe2O4)xGdBa2Cu3O7-δ, followed by a systematic decrease with increasing x. On the other hand, the Tc values for (CoFe2O4)xGdBa2Cu3O7-δ show a systematic decrease with x for both high and low additions while Jc is enhanced up to x = 0.01 wt% and decrease with further increase in x.

The Effect of Mg²⁺Substitution with Li¹⁺on Structural and Optical Properties of Zn_0.5Li_2xMg_0.5-xFe₂O₄Nanoparticles

Nanoferrite materials had been synthesized to produce new alternate substance for reducing the rare or high cost of industrial materials. In this work, the Zn0.5Mg0.5-xLi2xFe2O4 nanoferrite (x = 0.00, 0.10, 0.20, 0.30 and 0.40) was prepared by co-precipitation approach. Structural and optical properties were investigated for the Zn0.5Mg0.5-xLi2xFe2O4 series by X-ray diffraction (XRD), Fourier transforms infrared (FTIR) and ultraviolet-visible (UV-Vis) spectroscopies. The XRD data showed that all samples of Zn0.5Mg0.5-xLi2xFe2O4 series possess a cubic spinel with a space group (Fd-3m) structure and crystallite size decreased from 116 to 96 nm with a doping ratio. Lattice parameter founded to increases with Li1+ ratio that result in the larger ionic radius of the Li1+ cation. FTIR result verified the formation of spinel structure by appearance of the absorption bands around 420, 580 cm-1. The energy band gap computed for Zn0.5Mg0.5-xLi2xFe2O4 samples and it founded in the range of 3.28 - 3.12eV.

Magnetic,dielectric and electrical modulus of Ce^(3+) doped cobalt-magnesium ferrite nanoparticles

In this work,the magnetic,dielectric properties and electric modulus of Ce^(3+) substituted cobaltmagnesium(Co_(0.7)Mg_(0.3)Ce_(x)Fe_(2-x)O_4)(labeled as CMCF) ferrite nanoparticles were investigated in detail.Saturation magnetization decreases from 50.05 to 34.87 emu/g for further substituting Ce^(3+) ions.Meanwhile,coercivity increases from 738.22 Gs for the CMCFO sample to 912.10 Gs for the CMCF2 sample,then decreases monotonically to 762.1 Gs for the CMCF5 sample.The cerium content and particle size play important roles in controlling the magnetization and coercivity of the CMCF nanoparticles.All CMCF nanoferrites are suitable for microwave applications since their high-frequency response ranges from 7.72 to 11.07 GHz.The CMCF nanoferrites' dielectric parameter dispersion exhibits normal behavior.The pristine Co-Mg nanoferrite only has ε' value of 28.25,but the nanoferrite MCMF2 has ε' value of365.03,with an enhancing ratio of 1192%.The conduction mechanism of the MCMF nanoferrites was determined by fitting the σ_(ac) results via the Jonscher power law.At 653 K,large polaron tunnelling is thought to be responsible for this conduction process,which is followed by electron barrier hopping at higher temperatures.Cole-Cole diagrams at different temperatures,assuring the contributions of the grains and their boundaries at lower temperatures(653 K) and only the grains at higher temperatures.Based on our results,the CMCF nanoferrites hold magnetic and semiconducting nature,which can be used in magnetic devices and dielectrics in lower-frequencies or conductors in higher-frequencies.