Effects of Ce^(3+) doping on the structure and magnetic properties of Mn-Zn ferrite fibers

Ce3+-doped Mn-Zn ferrite fibers were successfully prepared by the organic gel-thermal decomposition method from metal salts and citric acid. The composition,structure,and magnetic properties of these ferrite fibers were characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM),and vibrating sample magnetometer (VSM). The results show that Mn0.2Zn0.8Fe2-xCexO4 (x = 0-0.04) fibers are featured with an average grain size of 11.6-12.7 nm,with diameters ranging between 1.0 to 3.5 μm and a high aspect ratio (length/diameter). The Ce3+ ion doping has not resulted in crystal structural changes of the Mn-Zn ferrite phase and all the as-prepared ferrite fibers have a simple spinel phase structure,although this influences the morphologies of Mn0.2Zn0.8Fe2-xCexO4 ferrite fibers possibly owing to the lattice dis-tortion and internal-stress. Both the lattice constant and grain size increase slightly with the increase of the Ce3+ ion doping content. The soft magnetic properties of Mn-Zn ferrite fibers can be improved by a small amount of Ce3+ ion doping with an increase of the saturated magnetization and a decrease of the coercivity.

Magnetic properties and microstructures of SnO_2 doped Mn-Zn ferrites

The effects of additive SnO2 (0.4wt.%), with and without SiO2 (0.02wt.%) and/or CaO (0.04wt.%), on the microstructure and magnetic properties of Mn-Zn ferrites were reported. The results reveal that SnO2 on its own increases the initial permeability (μi) slightly, but SnO2 with SiO2 and/or CaO decreases the values of μi. However, ferrites with SnO2 additions have reduced power losses. The separate contributions of hysteresis loss and eddy current loss to the total power loss show that SnO2 (with or without SiO2 and/or CaO) doping increases the hysteresis loss slightly, but SnO2 doping alone reduces the eddy current loss significantly (～14%). The additions of SiO2 or CaO further decrease the eddy current loss, and by interaction of SnO2-CaO-SiO2, the eddy current loss is reduced by more than 20%. These magnetic and microstructural effects were discussed in terms of the additive-impurity interaction, the existence of grain boundary phases, and the effective bulk and grain boundary resistivities of the ferrites.

Preparation and Magnetic Properties of Mn-Zn Ferrites by the Co-precipitation Method

Mn-Zn ferrites （Mn1-xZnxFe2O4） with different compositions were prepared by the coprecipitation method, and the influences of such synthesis conditions as pH value, composition and volume ratio （R） of the mixed solution and NH4HCO3 solution on their microstructures and magnetic properties were discussed. The samples were characterized by X-ray diffraction （XRD） and magnetization measurement instrument. Lattice parameters and average crystalline size of the synthesized materials were calculated from the corresponding XRD patterns with the related software Jade.5. For samples of different pH values, only one phase was found when pH values were 7.0, 8.0 and 9.0. The sample with pH value of 7.0 exhibited the highest saturation magnetic induction, the lowest coercive force, and crystallized best. For samples of different R values with pH value of 7.0, only one phase was observed in all samples, and the sample with R value of 2.3 exhibited the highest saturation magnetic induction and the lowest coercive force. The composition has mainly afected the magnetic properties, and the saturation magnetic induction increases with the increase of the content of Zn （x）, but decreases when x is beyond 0.6. The trend of coercive force is on the contrary. However, no magnetism is exhibited when the x value is up to 0.8.

Magnetic Hysteresis and Complex Initial Permeability of Cr³⁺Substituted Mn-Zn Ferrites

The impact of Cr3+ ion on the magnetic properties of Mn0.50Zn0.50CrxFe2-xO4 (with x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) has been studied. Ferrite samples were synthesized by combustion method and sintered at various temperatures (1250°C, 1300°C and 1350°C). The structural properties were investigated by means of X-ray diffraction patterns and indicated that the samples possess single phase cubic spinel structure. The lattice parameter decreases with the increase in Cr3+ content, as the ionic radius of Cr3+ ion is smaller than that of Fe3+. The average grain size (D), bulk density (ρB) and initial permeability (μi’ )decreases with increase in Cr3+ content whereas porosity follows its opposite trend. The ρB was found to increase with increase in Cr3+ content as the sintering temperature (Ts) is increased from 1250°C to 1350°C. The Ts affects the densification, grain growth and (μi’ ) of the samples. The (μi’ ) strongly depends on average grain size, density and intragranular porosity. The B-H loops of the compositions were measured at room temperature. The saturation magnetization (Ms), coercivity (Hc) and hysteresis losses were studied as a function of Cr3+ content. The Ms was found to decrease with the increase of Cr3+ content, which is attributed to the dilution of A-B interaction.

Influence of Processing Parameters on the Magnetic Properties of Mn-Zn Ferrites

Pure MnO2, ZnO and Fe2O3 were used to prepare a Mn-Zn Ferrite sample of the nominal composition Mn0.64Zn0.29Fe2.07O4. These oxides were mixed firstly for 1hr, and then were milled for 20 and for 40 hrs. The as-mixed and the milled powders were examined by XRD and ME spectroscopy. The investigated samples were further mixed with PVA, granulated, cold pressed and sintered at different temperatures (1000, 1300 and 1400 oC) for 2 hrs and were then reinvestigated again. The magnetic properties of all samples before and after sintering were characterized using VSM at a field of 15 k Oe. When the powder oxides were milled for 20 hrs, detectable diffusion reaction was observed where the centers of all XRD peaks (due to Fe2O3 and MnO2) shifted to higher 2? angles, suggesting that Zn2+ cations had diffused through Fe3+ and/or Mn4+ lattices. The observed increase in the width of the XRD peaks can be attributed to the refinement of the powders by milling. Milling of the powder for 40 hrs resulted in the formation of spinel phase of (Zn, Fe), but MnO2 was disappeared probably due to the formation of amorphous structure. Sintering at 1000, 1300, and 1400 oC resulted in the formation of different spinel (Mn-Zn) ferrites. The ME measurements followed the gradual formation the manganese zinc ferrite until complete formation which observed in the sample that milled for 40 hrs followed by sintering at 1300 oC for two hrs. However, it can be concluded that, the processing conditions of such sample represent are the best conditions for obtaining a soft manganese zinc ferrite (single phase).

Characterization and Electromagnetic Studies on NiZn and NiCuZn Ferrites Prepared by Microwave Sintering Technique

The low-temperature sintered NiZn and NiCuZn ferrites with the composition of Ni0.40Zn0.60Fe2O4 and Ni0.35Cu0.05Zn0.60 Fe2O4 were respectively synthesized by the microwave sintering method. These powders were calcined, compacted and sintered at 950℃ for 30 min. X-ray diffraction (XRD) patterns of the samples indicate the formation of single-phase cubic spinel structure. The grain size was estimated from SEM images which increase with CuO addition. The X-ray density is higher than the bulk density in both the ferrites. The temperature variation of the initial permeability of these samples was carried out from 30℃ to 250℃. The NiCuZn ferrite had higher initial permeability than that of the NiZn ferrite, which could be attributed to the microstructure. Saturation magnetization increases from 40 emug/g (NiZn) to 47 emug/g (NiCuZn). The dielectric constant and dielectric loss tangent of NiZn and NiCuZn ferrite samples decreases with increase in frequency exhibiting normal ferrimagnetic behavior. The NiCuZn ferrite had better electro- magnetic properties than the NiZn ferrite.

Effect of V2O5-CaCO3-Nb2O5 Contents on Properties of Low Power Loss Mn-Zn Ferrites

Effect of the content of dopants in the manganese-zinc ferrites on the low power loss is studied by measuring magnetic properties and observing the grain boundary structures. The Mn0.738Zn0.206Fe2.066O4 composition powders were prepared by using conventional ceramic powder processing technique. The microstructure of grain boundary was observed by scanning electron microscope （SEM）. It has been found that power loss is greatly dependent upon the content of the additives.

Sintering process and grain growth of Mn-Zn ferrite nanoparticles

The density, microstructure and magnetic properties of non-doped Mn-Zn ferrite nanoparticles sintered compacts were investigated. The compacts of non-doped Mn-Zn ferrite nanoparticles were sintered by segmented-sintering process at lower sintering temperature. The density of sintered samples was measured by Archimedes method, and the phase composition and microstructure were examined by XRD and SEM. The sintered Mn-Zn ferrite magnetic measurements were carried out with Vibrating Sample. The results show that the density of sintered compacts increases with the rising of sintering temperature, achieving 4.8245 g·cm-3 when sintered at 900 ℃, which is the optimal density of Mn-Zn functional ferrite needed and from the fractured surface of sintered samples, it can be seen that the grain grows well with small grain size and homogeneous distribution.

Modification Mechanism of Bi_2O_3 on Low-temperature Sintering Ni-Zn-Cu Ferrite

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Magnetic properties of samarium and gadolinium co-doping Mn-Zn ferrites obtained by sol-gel auto-combustion method

Mn-Zn ferrites doped with different contents of Sm^（3＋） and Gd^（3＋） ions were prepared by sol-gel auto-combustion method and characterized by Fourier transform infrared spectroscopy（FTIR）, thermogravimetric analysis（TG）, X-ray diffraction（XRD）, scanning electron microscopy（SEM） and vibrating sample magnetometer（VSM）. When samples were calcined in a relatively low temperature below 1100 °C, secondary phases（α-Fe_2O_3） could be identified. Therefore, in order to acquire pure and better crystallinity, the suitable calcining temperature of powders was selected at 1200 °C. It was also found that all the samples consisting of ferrite phases of typical spinel cubic structure and average crystallite sizes between 31.5 and 38.2 nm were obtained after calcining at 1200 oC for 4 h. The lattice parameters increased almost linearly with increasing Sm content. A dense microstructure was obtained after sintering at 1250 °C for 4 h. Through the analysis of magnetic properties, hysteresis loops for all the samples were narrow with low values of coercivity and retentivity, indicating the paramagnetic nature of these samples. And saturation magnetization Ms strongly depended on the type of additive to reach a maximum of 47.99 emu/g for x=0.015, which showed a great promise for hyperthermia applications.

软磁Mn-Zn铁氧体纳米晶的低温自蔓延合成及表征

采用低温自蔓延方法合成了Mn Zn铁氧体纳米晶 ,对其进行了X射线衍射 (XRD) ,X射线能谱 (EDS) ,电子自旋共振波谱 (ESR)和透射电镜 (TEM)等测试 .研究结果表明 :铁氧体化学式为 (MnZn) 0 .5Fe2 O4 ;铁氧体结晶状况良好 ;铁氧体的g值为 9.95 6 0 ;铁氧体纳米晶粒径较均匀 ,为 10～ 2 0nm ,与Scherrer公式计算所得晶粒尺寸 (16 .9nm)相符 ;合成铁氧体的g值远大于自由电子的g值 (ge=2 .0 0 2 3) ,初步推断是Mn2 + ,Fe3+ 的 3d5半充满价电子层结构和它们在尖晶石型晶胞 (MnZn) 0 .5Fe2 O4 中的磁矩偶合作用所致 .

软磁Mn-Zn铁氧体纳米晶的低温自蔓延合成及表征

采用低温自蔓延方法合成了Mn-Zn铁氧体纳米晶,EDS测试结果表明该纳米晶的化学式为(MnZn)_(0.5)Fe_2O_4。由ESR谱图求得其g值为9.9560,远大于自由电子的g值(g_e=2.0023),这主要由Mn^(2+),Fe^(3+)的3d^5半充满价电子层结构和它们在尖晶石型晶胞(MnZn)_(0.5)Fe_2O_4中的磁矩偶合作用所致;XRD测试结果显示该Mn-Zn铁氧体纳米晶结晶良好。TEM测试结果表明该Mn-Zn铁氧体纳米晶粒径较均匀,晶粒粒径为10～20 nm,与由Scherrer公式算得的晶粒尺寸16.9 nm较吻合。

基于改进酸再生机组喷嘴设计提高铁红比表面积研究

某冷轧酸再生机组负责处理酸洗线废酸和供给再生酸,废酸经由脱硅系统、焙烧炉系统等工艺环节处理,生产出再生盐酸供给酸洗线使用,同时产出高附加值的副产品铁红,铁红一般指Fe_(2)O_(3)。Fe_(2)O_(3)是一种无机化合物,为红棕色粉末。软磁铁氧体材料用Fe_(2)O_(3),化学纯度高,颗粒细而均匀,呈球状布局,SBET(比表面积),通常在3.0 m^(2)/g,比表面积也是衡量铁红的一项重要理化指标,本文针对铁红比表面积进行研究,研究一种可以通过改善喷枪雾化效果,达到提高铁红比表面积的喷嘴。

原料粉体粒径对NiCuZn软磁铁氧体微观结构和磁性能的影响

通过改变二次球磨时间(1~6 h)调控原料粉体粒径,采用固相烧结法制备NiCuZn软磁铁氧体,研究了原料粉体粒径对软磁铁氧体微观结构和磁性能的影响。结果表明:粉体粒径随着二次球磨时间的延长而减小,尺寸分布逐渐集中;制备的软磁铁氧体晶粒尺寸的均匀性先变好后变差,晶界先变清晰后变模糊;随着粉体粒径的减小,NiCuZn软磁铁氧体的起始磁导率、饱和磁感应强度、相对密度及电阻率均先增大后减小,功率损耗先减小后增大;当二次球磨时间为3 h时,粉体粒径主要集中在2.5~3.5μm,平均粒径为3.237μm,烧结制备的软磁铁氧体的晶界较为清晰,晶粒尺寸均匀,起始磁导率、饱和磁感应强度最大,分别为1385 H·m^(-1)和360 mT,功率损耗最小,为284 kW·m^(-3)。

不同铁粉对宽温高导MnZn铁氧体直流叠加性能的影响

以进口和国内4种不同铁粉为原料,通过传统陶瓷工艺制备宽温高导高直流叠加MnZn铁氧体。通过XRF分析4种铁粉成分差异,研究不同铁粉配方的铁氧体宽温直流叠加特性,通过SEM对铁氧体内部进行微区分析。结果表明:日本铁粉杂质含量低、纯度高,制备的铁氧体性能最佳;韩国和中国台湾铁粉有害杂质元素含量偏高,不利于制备宽温高导高直流叠加性能的铁氧体;湖南涟钢铁粉有害杂质元素略高于日本铁粉,调整主配方Fe_(2)O_(3)及添加剂CaCO_(3)、SiO_(2)用量后,涟钢铁粉制备的铁氧体性能在-40℃时起始磁导率μi≥3200、增量磁导率μ△≥2900;25℃时μi≥4100、μ△≥3600;85℃时μi≥4500、μ△≥2400。

软磁材料锰锌铁氧体共沉粉料的研制

本文研究了碳酸盐—氢氧化物法共同沉淀Ｆｅ２＋、Ｍｎ２＋、Ｚｎ２＋时，反应最终ｐＨ值、沉淀温度、加料方式、加料速度及搅拌强度等因素对恒定共沉粉Ｆｅ２Ｏ３、ＭｎＯ及ＺｎＯｍｏｌ％组成、粒度和颗粒形状的影响，并进一步考查了共沉粉组成与软磁材料性能的关系。在研究基础上确定生产高频低功耗锰锌铁氧体材料Ｈ７２４（ＰＣ４０）和高磁导率锰锌铁氧体材料Ｈ５Ｃ２（μｉ＝１００００±３０％）共沉粉合成的最宜条件。

Bi掺杂对Ni-Zn-Cu铁氧体的烧结与磁性能的影响

低温烧结软磁铁氧体是表面组装元件（ＳＭＤ）中的一类关键材料。本文对Ｂｉ掺杂的低温烧结Ｎｉ－Ｚｎ－Ｃｕ铁氧体从烧结性质、结构与相组成、显微形貌、磁结构和磁性质（磁导率、品质因数及频谱）方面进行了研究，在此基础上分析了Ｂｉ掺杂对材料形成过程和磁化机制的影响，发现Ｂｉ对材料磁性能的改进所起的作用主要产生于它对材料显微结构（晶粒、晶界和气孔）的调制。

微乳液法制备几种纳米软磁铁氧体粉体及磁性能研究

采用水/Triton X-100/环己烷/正己醇微乳体系制备了尖晶石型NiFe2O4、Ni0.5Zn0.5Fe2O4、MnFe2O4、Mn0.5Zn0.5Fe2O4纳米粉体,利用X射线衍射（XRD）、透射电子显微镜（TEM）、Zeta电位仪、振动样品磁强计（VSM）等对纳米粉体的结构和磁性能进行表征。研究结果表明：微乳液法制备的纳米软磁铁氧体晶粒结构完整、粒径细小且分布均匀（粒径范围在30-80 nm）,合适的煅烧温度为500℃;在室温下对制备的几种软磁铁氧体进行磁性能测定发现,与其他制备方法相比,采用微乳液法制备的纳米软磁铁氧体的比饱和磁化强度较高,比剩余磁化强度、矫顽力较低,软磁性性能较佳。

“直接-共沉法”生产低功耗锰锌软磁铁氧体粉料

成功地进行了年产 5 0 0t高性能锰锌软磁铁氧体粉料的“直接 共沉法”工业性试验。以铁屑、软锰矿、氧化锌烟灰为原料 ,经浸出、初步净化、深度净化、配液和共沉淀、干燥、预烧等加工过程制取了低功耗锰锌软磁铁氧体粉料。铁、锰、锌的总回收率 ( % )分别为 :Fe 93 .2 7;Mn 93 .3 5 ;Zn 84.0 1。共沉粉杂质元素含量低 ,特别是硅的含量小于 0 .0 0 5 0 %。以共沉粉大批量制备的软磁铁氧体粉料的磁性能全部达到PC3 0标准 ,部分符合PC40要求。“直接 共沉法”生产铁氧体粉料具有产品质量较高 ,生产成本低 ,无环境污染 。

尖晶石型软磁铁氧体纳米材料的制备研究进展

介绍了软磁铁氧体纳米材料的特性,综述了近年来具有尖晶石结构的软磁铁氧体纳米材料的制备方法。其中包括:化学共沉淀法,水热法,溶胶-凝胶法,喷雾热解法,微乳液法,相转化法,超临界法,冲击波合成法,微波场下湿法合成,爆炸法,高能球磨法,自蔓延高温合成法等。详细介绍了各种制备方法的特点,研究进展及其发展趋势。