成分优化对软磁MnZn铁氧体的影响规律

采用“化学溶胶—喷雾干燥—煅烧”方法制备Mn_(0.5−y)Zn_(0.5)Fe_(2+y)O_(4)(y=0,0.01,0.03,0.05,0.07,0.09)软磁MnZn铁氧体,利用X射线衍射(XRD)、红外光谱(FTIR)、拉曼光谱(Raman)、X射线光电子能谱(XPS)、扫描电镜(SEM)、透射电镜(TEM)和超导量子干涉磁测量系统等检测方法对其进行表征。研究结果表明:当y=0~0.07时,样品均只含有MnZn铁氧体单相;而当y=0.09时,将析出α-Fe_(2)O_(3)杂质相,此现象得到了XRD和Raman光谱结果验证。随着Fe含量的增加,平均晶粒度先减小再增大,当y=0.03时,平均晶粒度最小。样品中的Fe呈+3价,Zn呈+2价,而Mn则存在+2、+3和+4这3种价态,其中,当y=0.09时,样品中Fe^(3+)位于MnZn铁氧体和α-Fe_(2)O_(3)中的环境不同,其Fe2p_(3/2)峰存在结合能分别为710.09、711.16和713.71 eV的3个子峰。样品中Mn^(2+)的含量先增加再减少,在y=0.07时最大。所有样品均呈细小颗粒组成的空心球壳形貌,几乎不存在非空心球壳粉末形貌,且元素均匀化分布。当y=0~0.09时,比饱和磁化强度(M_(s))为41.15~54.58 A·m^(2)/kg,剩磁(M_(r))为0.91~6.50 mA/m,矫顽力(H_(c))为2242.4~8917.6 A/m,矩形比(M_(r)/M_(s))为0.02~0.12。其中,当Fe过量时,M_(s)呈先增大再减小的趋势;当y=0.07时,MnZn铁氧体的综合特性最优。

Direct Preparation of the Nanocrystalline MnZn Ferrites by Using Oxalate as Precipitant

Oxalate was generally used as a precipitant for synthesis of MnZn ferrites during the co-precipitation process. However, the MnZn ferrite couldn’t be directly obtained and a calcination process was needed. In this research, we reported a direct preparation of the MnZn ferrite nanoparticles by using co-precipitation method, together with refluxing process. XRD measurements proved that crystallite size of the obtained samples increased with an increase in pH value of the co-precipitation solution, and that the crystallite size of about 25 nm was obtained for the sample at a pH of 13. This sample showed the maximum Ms of 58.6 emu/g, which was about one times larger than that of 12 (pH value). Calcination to the obtained samples result in an enlargement in their crystal size and an improvement in their magnetic properties with an increase in temperatures. The samples calcinated in CO2 + H2 atmosphere presented good stability, and the maximum Ms value of 188.2 emu/g was obtained for the 1100。C-heated sample. Unfortunately, precipitation of some Fe2O3 at 800。C suggested poor stability of the nanocrystalline MnZn ferrite in N2 atmosphere.

Determination of impurity elements in MnZn ferrites by inductively coupled plasma mass spectrometry

An inductively coupled plasma mass spectrometry(ICP-MS) method was developed for the determination of Na, Mg, Al,K, Ca, Ti, Cr, Co, Ni, Cu, Ga, As, Mo, Ag, Cd and Pb in MnZn ferrites. The sample was digested by HNO3+HCl with microwave digestion followed by dilution with ultrapure water, then the above 16 impurity elements in the solution were analyzed directly by ICP-MS. The impurity elements were introduced by the helium gas or hydrogen gas into the octopole reaction system(ORS) to eliminate the polyatomic interferences caused by the high salty matrixes. The matrix effect was minimized through matrix matching,and Be, Y and Rh were used as internal standard elements. The working parameters of the instrument were optimized. The results show that the method has good precision and high accuracy. The detection limits for the investigated elements are in the range of0.9-37.5 ng/L, the relative standard deviation of each element is within 1.1%-4.8%, and the recovery of each element is 90%-108%.

MnZn铁氧体材料温度特性研究概要

MnZn铁氧体材料是一种品类多、应用广、用量大的软磁材料,材料的温度特性决定了其工作温度范围,因此必须严格控制其温度特性。MnZn铁氧体材料的温度特性主要取决于材料的居里温度和二峰温度,即晶体结构中亚晶格A、B位上磁性离子间超交换作用的强弱、磁晶各向异性常数K1的补偿作用。本文主要介绍了主配方、制备工艺和掺杂对于居里温度和二峰温度的影响,提出了基于居里温度和二峰温度的经验计算公式快速确定主配方的方法,指出了Co2+过补偿与Fe2+含量的关联性。

Effects of Hyperfine and Dopant Cation Interactions on theDC-Electrical Conductivity of MnZn Ferrites

Samples of undoped, and CuO, CaO, Al2O3 as well as V2O5 doped MnZn ferrite were prepared using standard ceramic method. The X-ray diffraction results for the base and doped ferrite samples show a single phase with spinel cubic structure. The Mossbauer spectrum of the base sample indicates line broadening and overlapping due to relaxation of magnetic dipoles. The temperature dependence of DC-electrical conductivity has been discussed on the basis of electronic conduction (electron hopping) and ionic conduction mechanism.

Synthesis of MnZn Ferrite Nanoscale Particles by Hydrothermal Method

Hydrothermal method was used to synthesize nanoscale particles of MnZn ferrites. The crystallites were characterized by XRD, TEM and SEM. The effects of the reaction time, temperature and additives on the product were investigated. Crystallization process would be carried out above 160 ℃ for 5 h or more, higher temperature can reduce the reaction time. Additives were used to remove impurities such as Fe 2O 3, ZnMnO 3.10～15 nm pure slightly agglomerated MnZn ferrite crystallites with a narrow grain size distribution were obtained.

Study on sintering process and characteristic of nanosized soft magnetic MnZn ferrite powders

The effect of sintering process (especially the sintering temperature) on the magnetic property and microstructure of sintered sample of nanosized soft magnetic MnZn ferrite powder was investigated. The sintered sample of MnZn ferrite was prepared by both traditional pressing and cool isostatic pressing on MnZn ferrite nanoparticals. The sintering process of which was segmented. The density, microstructure and phase composition of sintered sample were analyzed by Archimedes′law, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The grain growth and densification in sintering process of MnZn ferrite were investigated. The magnetic property was measured by vibrating sample magnetometer (VSM) and Nim2000 magnetic material testing system. The results show that the better sintering temperature is 850 ℃, at which the better magnetic property and microstructure of sintered compact were obtained.

Microstructure and magnetic performance of Ni-substituted high density MnZn ferrite

The effects of NiO on microstructure and magnetic properties of Mn-Zn ferrite with a nominal composition of Zn_(0.32)Mn_(0.60-x)Ni_(x)Fe_(2.08)O_(4)were investigated.The calcined powder of Mn-Zn ferrite was characterized by X-ray diffraction(XRD),the fracture surface of Mn-Zn ferrite was checked by scanning electronic microscope(SEM),and then the magnetic properties were measured.As a result,the substitution of Ni can cause the crystal lattice constant of MnZn ferrite to decline,and the grain size to decrease,therefore improve the magnetic performance of MnZn ferrite whose density exceeds 5.0 g·cm^(-3).

Determination of trace impurity elements in MnZn ferrite powder by direct current glow discharge mass spectrometry

An analytical method for the determination of 26 impurity elements （such as Li, Be, Na, Mg, Al, Si, P, S, K, Ca, Sc, Ti, V, Cr, Co, Ni, Ga, Ge, Y, Nb, Mo, Ag, Cd, Sb, W and Pb） in MnZn ferrite powder by direct current glow discharge mass spectrometry （GD-MS） was established. MnZn ferrite powder was mixed with copper powder, used as a conductor, and pressed. The effects of MnZn ferrite powder preparation conditions and glow discharge parameters for the sensitivity and stability of signal analysis were investigated. By determining the choice of isotope and the application of the mass resolutions of 4000 （MR, medium resolution） and 10000 （HR, high resolution）, mass spectral interference was eliminated. The contents of impurity elements in MnZn ferrite powder was calculated by subtraction after normalizing the total signal of Mn, Zn, Fe, O and Cu. The results showed that the detection limit of 26 kinds of impurity elements was between 0.002 and 0.57 μg/g, and the relative standard deviation （RSD） was between 3.33% and 32.35%. The accuracy of this method was verified by the ICP-MS. The method was simple and practical, which is applied to the determination of impurity elements in MnZn ferrite powder.

Effect of additive on synthesis of MnZn ferrite nanocrystal by hydrothermal crystallization

The effect of additive RCOONa on the formation of MnZn ferrite homogeneous coprecipitation precursor was studied in this paper. The action of additive in the MnZn ferrite hydrothermal crystallization process was investigated according to crystal field theory and crystal growth unit theory. And the growth unit formation process was presented and its structure was illustrated. The results show that the precursor of MnZn ferrite is a colloidal mixture composed of Zn(OH) 2, Fe(OH) 2, Mn(OH) 2, MnO(OH) , MnO 2· x H 2O and so on, and dissolves in solution in the form of hydroxyl coordination tetrahedron and octahedron such as Zn(OH) 2- 4, Fe(OH) 2- 4, Fe(OH) 4- 6,Fe(OH) - 4, Fe(OH) 3- 6,Mn(OH) 2- 4,Mn(OH) 3- 6 etc., and the growth unit is formed by combination of the coordination polyhedra subsequently in the hydrothermal precess. The additive is beneficial to the formation of homogeneous precursor and has dispersive effect on the aggregation of the crystal growth unit by forming associate with hydrogen bond, which is beneficial to the synthesis of the pure product with a tiny size and a narrow size distribution.

Effects of La^(3+) doping on MnZn ferrite nanoscale particles synthesized by hydrothermal method

MnZn ferrite nanoscale particles were synthesized by hydrothermal method. The effects of amount of addition La3+ on the products were discussed. The product was characterized by X-ray diffraction （XRD） and transmission electron microscope （TEM）. The results show that the sample with 0.2% La3+（mass fraction） or without La3+ has only spinel phase, but the sample with mass fraction of La3+ exceeding 0.4% posses second phase besides the spinel one; and the nano-MnZn ferrites change from cube to hexagon when the mass fractions of La3+ is up to （1.2%.） TEM image of the sample with 1.2% La3+ indicates that the homogeneous hexagonal crystal is obtained and the particles are larger than those of undoped; the addition of La3+ has great influence on the crystallization of hydrothermal process and can change the shape of particles and improve their growth. The saturation magnetization of the sample with 1.2% La3+ (2.64 A·m2·kg-1) is lower than that of undoped (17.54 (A·m2·kg-1)) and it behaves superparamagnetically.

Effect of inner oxidant on self-propagating high-temperature synthesis of MnZn-ferrite powder

Using KClO3 as an inner oxidant, MnZn-ferrite powder was synthesized by a self-propagating high-temperature synthesis (SHS) process in normal air atmosphere. The effects of the inner oxidant on combustion temperature, combustion velocity, microstructure and the phase of the product were investigated by XRD and SEM,respectively. The results show that a highly ferritized powder can be obtained as well as the highest combustion temperature and the highest combustion velocity when the inner oxidant content m equals 54(k-16).

Nb_(2)O_(5)添加对高导MnZn铁氧体磁性能的影响

采用传统氧化物陶瓷工艺法制备高磁导率MnZn软磁铁氧体材料,研究了Nb_(2)O_(5)添加对铁氧体材料晶相和显微结构、相对损耗因数tanδ/μi、饱和磁感应强度Bs、磁导率以及磁谱特性的影响。研究结果表明,Nb_(2)O_(5)添加能够细化铁氧体的晶粒大小,适量添加能够改善材料的显微结构,提高磁性能;而过量添加Nb_(2)O_(5),则会使材料晶粒尺寸迅速减小,导致显微结构恶化,最终降低材料的磁性能。由此确定出适宜的Nb_(2)O_(5)添加量为0.01~0.02 wt%。

Preparation and properties of nanosize MnZn ferrite from δ-FeOOH

Ferrous ion was transformed into feroxyhyte (δ-FeOOH) by oxidation. Then, manganese sulfate and zinc sulfate in some ratio were added to the feroxyhyte solution. The co-precipitation was boiling reflux conditions sometime under constant stirring. The nanosize MnZn ferrite powder was formed. The mechanism of preparation of the nanosize MnZn ferrite was discussed, and the formation of feroxyhyte which was playing a key role during the process was mentioned. The properties of powder was tested by means of X-ray diffraction, transmission electron microscopy and vibrating sample magnetometer. The results show that the samples of spherical particles about 20 nm, which have characteristics of ferrimagnetism, has larger saturation magnetization, but the remanent magnetization and coercivity are comparatively smaller. The spinel MnZn ferrite nanosize powder was successfully prepared from δ-FeOOH at low temperature, with low-carbon steel and peroxide as main material.

ZrO_(2)-Nb_(2)O_(5)复合添加对MnZn铁氧体结构和磁性能的影响

针对开关电源高频小型化需求,采用固相反应制备分子式为(Mn_(0.766)Zn_(0.105)Fe_(0.129))Fe_(2)O_(4)的MnZn铁氧体材料,通过对铁氧体微结构的表征及磁性能的测试,研究了ZrO_(2)和Nb_(2)O_(5)复合添加对MnZn铁氧体显微结构、烧结密度d、初始磁导率μ_(i)、饱和磁通密度B_(s)、剩余磁通密度B_(r)、矫顽力H_(c)以及功耗P_(cv)特性的影响。结果表明,ZrO_(2)和Nb_(2)O_(5)复合添加有利于促进晶粒均匀化和致密化,从而提高了材料烧结密度,能显著降低材料的剩余磁通密度和矫顽力,实现材料的高起始磁导率以及高频低损耗。当ZrO_(2)和Nb_(2)O_(5)复合添加质量比为4∶6时,MnZn铁氧体的μi达到最大值(931),且在高频激励下材料的功率损耗达到最低133 kW/m^(3)(100℃,1000 kHz,50 mT)。

Studies on the Relation between the Composition of Thermal Sensitive MnZn Ferrite and Curie Temperature

Thermal sensitive MnZn ferrite is a kind of soft magnetic ferrite material with lower Curie temperature (Tc) and can be used to make many kinds of magnetic thermal sensitive sensors with high sensitivity. In this paper, the relation between the composition of thermal sensitive ferrite and TC was studied. It was found that TC changes linearly with ZnO extent when the content of Fe2O3 is fixed. Based on lots of experiments, an experimential formula to determine was given out.

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。

MnZn功率铁氧体的研究进展及发展趋势

介绍了宽温超低损耗、高频低损耗和高温高饱和磁感应强度(Bs)MnZn功率铁氧体材料的研究现状,以及添加剂的种类和制备方法的研究,世界上主要软磁铁氧体公司近几年的最新产品情况,指出了MnZn功率铁氧体的发展趋势。从目前的发展状况来看,应用在中低频的功率MnZn铁氧体材料不但要求在较宽的温度范围内具有较低的损耗,同时要求具有高的起始磁导率和饱和磁感应强度。而对于高频功率MnZn铁氧体材料则继续向高频低损耗发展。

Ti取代对MnZn功率铁氧体微结构及磁性能的影响

采用氧化物陶瓷工艺制备了MnZn功率铁氧体,研究了Ti4+取代Mn2+对MnZn功率铁氧体微结构及磁性能的影响,由于Ti4+是非磁性离子,它对磁性离子Mn2+的取代,必将对材料的微结构、磁性能以及居里温度产生影响。结果表明,Ti4+取代Mn2+可提高MnZn铁氧体居里温度,适量的Ti4+取代,有利于提高致密度和起始磁导率,并降低磁损耗。为了得到优良的电磁性能,适宜的Ti4+取代量为0.5mol%。

Zn^(2+)对MnZn铁氧体结构、磁性能和磁热效应的影响

采用溶胶-凝胶自燃烧法制备了不同Zn2+含量的纳米MnZn铁氧体微粒,并通过XRD、VSM、TEM等方法研究了Zn2+含量对MnZn铁氧体结构、磁性能及在外磁场作用下磁热效应的影响。结果表明,Zn2+含量对MnZn铁氧体的结构与性能有重要的影响,其中成分为Mn0.8Zn0.2Fe2O4的铁氧体微粒,具有最高的饱和磁化强度和磁热效应,10mg的该样品在频率为60kHz的外磁场诱导下,20min内使得1ml去离子水升温了32℃,显示出优良的磁热性能。同时,通过调节Zn2+含量实现了MnZn铁氧体发热量的可调性。随着Zn2+含量的增加,Mn1-xZnxFe2O4的矫顽力Hc和剩余磁化强度Br不断减小,而饱和磁化强度Ms先增大后减小,在x=0.2处达到最大值,约为44.6(A.m2)/kg。