Preparation and Sinterability of Mn-Zn Ferrite Powders by Sol-Gel Method

Mn-Zn spinel ferrites were synthesized by sol-gel method. Effects of calcined temperature on structure and particle size of MnZnFe2O4 were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD patterns indicate that the ultra fine Mn-Zn ferrite exhibits a spinel crystal structure. SEM images show that the powder fired at 900℃for 2 h has an average diameter of 60 ~ 90 nm. The particle size becomes larger with the increasing of calcined temperature and the distribution of particle becomes even more homogeneous. Sintering behaviors of synthesized ferrite powders depend on the powder characteristics and high temperatures have induced the good crystallization of particles.

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 ...

Preparation, Microstructure and Magnetic Properties of NiZn Ferrite Thin Films by Spin Spray Plating

NiZn ferrite thin fihns were performed on glass substrates of 85 ℃ by spin spray plating method. X-ray diffraction patterns of the films show that the samples have a cubic spinel structure with no extra lines corresponding to any other phases between 75 ℃ and 85 ℃. As the pH value of oxidizing solution increases to 8.3, the saturation magnetization increases to 3.13 × 10^5 A/m and resistivity to 127 m Ω ·cm. Film deposited at pH 7.8 has a smooth surface and definite columnar structure. The large wavy flakes were observed at pH 8.3. The high real part of complex permeability μ′ up to 36.1 and the imaginary part μ″ up to 53.2 were observed at 0.5 GHz by short microstrip line perturbation method. The μ″ of thin film has values higher than 20 at the frequencies between 0.5 GHz and 2 GHz, the film is a promising anti-noise material for high frequency applications,

Effects of Heating Processing on Microstructure and Magnetic Properties of Mn-Zn Ferrites Prepared via Chemical Co-precipitation

The fine powders of Mn-Zn ferrites with uniform size were prepared via chemical co- precipitation method. X-ray diffraction analysis （XRD）, scanning electron microscopy （SEM）, vibrating sample magnetometer （VSM）, frequency dependence of permeability and metallographical microscope were used to investigate the crystal structure, surface topography and magnetic properties of the powders and the sintering samples. The experimental results demonstrate that the precursor powders have formed a pure phase cubic spinel MnxZn1-xfe2O4 while in the reactor and show definite magnetism, which can solve the difficult issue in washing process effectively. When calcined beneath 450 ℃, the powders have intact crystal form and the crystallite size is less than 20 nm. Comparison tests of sintering temperatures show that 1 300 ℃ is the ideal sintering temperature for Mn-Zn ferrites prepared by using the chemical co-precipitation.

Perpendicularly oriented barium ferrite thin films with low microwave loss,prepared by pulsed laser deposition

Barium ferrite（Ba M） thin films are deposited on platinum coated silicon wafers by pulsed laser deposition（PLD）.The effects of deposition substrate temperature on the microstructure,magnetic and microwave properties of Ba M thin films are investigated in detail.It is found that microstructure,magnetic and microwave properties of Ba M thin film are very sensitive to deposition substrate temperature,and excellent Ba M thin film is obtained when deposition temperature is 910℃ and oxygen pressure is 300 m Torr（1 Torr = 1.3332×102Pa）.X-ray diffraction patterns and atomic force microscopy images show that the best thin film has perpendicular orientation and hexagonal morphology,and the crystallographic alignment degree can be calculated to be 0.94.Hysteresis loops reveal that the squareness ratio（Mr/Ms） is as high as 0.93,the saturated magnetization is 4004 Gs（1 Gs = 104T）,and the anisotropy field is 16.5 kOe（1 Oe = 79.5775 A·m-1）.Ferromagnetic resonance measurements reveal that the gyromagnetic ratio is 2.8 GHz/kOe,and the ferromagnetic resonance linewith is108 Oe at 50 GHz,which means that this thin film has low microwave loss.These properties make the Ba M thin films have potential applications in microwave devices.

Study of NiCuZn ferrite powders and films prepared by sol gel method

This paper reports that a series of NiCuZn ferrite powders and films are prepared by using sol-gel method. The effects of raw material composition and the calcinate temperature on magnetic properties of them are investigated. The NiCuZn ferrite powders are prepared by the self-propagating high-temperature synthesis method and subsequently heated at 700 ℃-1000 ℃. The results show that NiCuZn ferrite powders with single spinel phase can be formed after heat-treating at 750 ℃. Powders obtained from Ni0.4Cu0.2Zn0.4Fel.904 gel have better magnetic properties than those from gels with other composition. After heat-treating at 900 ℃for 3 h, coercivity Hc and saturation magnetization Ms are 9.70e （i Oe = 80 A/m） and 72.4 emu/g, respectively. Different from the powders, NiCuZn films produced on Si （100） from the Ni0.4Cuo.2Zno.4Fe204 gel formed at room temperature possess high properties. When heat-treating condition is around 600 ℃for 6 rain, samples with low Hc and high Ms will be obtained. The minimal Hc is 16.70e and Ms is about 300 emu/cm3. In comparison with the films prepared through long-time heat treating, the films prepared through short heat-treating time exhibits better soft magnetic properties.

Texture and self-biased property of an oriented M-type barium ferrite thick film by tape casting

In this paper, the oriented M-type barium ferrite （BaM） thick films with different thicknesses are prepared by tape casting. It is found that the crystallographic alignment degree （f）, the pore and the squareness ratio （Mr/Ms） are not affected by the thickness of the film. XRD and SEM results show that the thick film has hexagonal morphology with a crystal texture of c-axis grains perpendicular to film plane. The hysteresis curve indicates that the BaM thick film exhibits a self-biased property with a remanent magnetization of 3.30 T, a squareness ratio （Mr/Ms） of 0.81, and a coercivity of 0.40 T. The results show that the BaM thick film has potential for use in self-biasing microwave devices, and also proves that the tape casting technique is capable of fabricating high-quality barium ferrite films, thus providing a unique opportunity to realize the large area production of thick film.

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 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.

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.

Influnce of Stoichiometry and Molar Ratio of Barium Ferrite Thin Film Synthesized by Sol-gel on Alumina Substrate

Amorphous gels were processed with a varying Fe/Ba ratio of 11/5, 28/2, 10.5/1 in water and Solvent. Iron and barium nitrites with specific molar ratio was solved in water and slovent at 60°C for 3 hours until! a dark brown solution was prepared . The sols were introduced to substrate dropwise and spinning with 2000 rpm in 3 min was applied ; the work was repeated for 10 times and the samples were dried and sintered . The TGA analysis was used to identify the heating rate of the samples; at temperature of 1150°c for one hour the final phase was attained . the thickness , uniformity , morphology and the composition were examined by SEM and XRD. The study shows that the fabrication barium ferrite film of the molar ratio of Fe/Ba = 10.5/1 is much more suitable than other ratios .

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.

Structural and Magnetic Studies of CTAC-assisted NiZn Ferrite Films within 0.1-3.5 GHz

Spinel NiZn ferrite thin films were prepared on glass substrates by spray plating method. Adding cetyltrimethylammoniumchloride （CTAC）, adsorptive energy of substrate surface increased, and smooth surface and uniform columnar film structures were observed. The optimum reaction temperature up to 85℃ and pH up to 7.5 were obtained. As the solution pH value increases from 6.5 to 7.5, the film saturation magnetization increases to 36.1 and the imaginary part μ″ up to 53.2 for NiZn ferrite film at 500 MHz were achieved, and higher magnetic resonance at 508 MHz was observed. As the ferrite plate thickness is 50 μm, the attenuating characteristics for reflection loss ≤-0.8 dB can be obtained in the wide frequency ranging from 0.5 to 2.7 GHz. Theμ″ of thin film has values higher than 20 at the frequencies between 0.5 and 2 GHz, and the thin film can be applied as shielding material in GHz range.

Magnetic Properties of Nanometer-Scale NiZnCu Ferrite Thin Films Fabricated by Spray-Spin-Heating-Coating Method

A new nanometer-scale ferrite thin film with excellent high-frequency characteristics has been developed by the spray-spin-heating-coating method. The effects of the ion synthesis mechanism, chemical stoichiometry, fabrication method, and doping content on the magnetic properties and microstructure of the thin films have been analyzed. The films formed between 75℃ and 90℃ by spray-spin-heating-coating methods was discovered with fine grain size of about 21 nm, high saturation magnetization (4πMs) of about 6.5 kGs, coercivity of about 9.8 Oe, as well as initial permeability of about 14.0. These films can be widely used in radio-frequency integrated circuit devices.

Effect of Nd Doping on Nanosized Mn-Zn Ferrite

Nanosized Mn-Zn ferrite doped with Nd (Mn_ 0.6Zn_ 0.4Nd_xFe_ 2-xO_4) were fabricated by hydrothermal precipitation route and studied by XRD, TEM, DSC and VSM. The effects of Nd doping on manganese zinc ferrites were discussed. The results show that the samples with a small amount of Nd doping are spinel crystal structure and uniformly nanosized particles with little aggregation. DSC analysis of Mn_ 0.6Zn_ 0.4Fe_2O_4 and Mn_ 0.6Zn_ 0.4Nd_ 0.06Fe_ 1.94O_4 samples both present two exothermic peaks ascribed to the redistribution of Mn 2+, Zn 2+ and Fe 3+ ions in the two sub-lattices (tetrahedral (A) and octahedral (B) sites), and the oxidation of Mn 2+-ions at higher temperatures respectively. The saturation magnetization (M_s) for Mn_ 0.6Zn_ 0.4Nd_xFe_ 2-xO_4 ferrites increase with (x) up to 0.06 and decrease for higher concentrations. And supermagnetic behavior was observed at 25 ℃ in the M-H loops of Mn_ 0.6Zn_ 0.4Fe_2O_4 and Mn_ 0.6Zn_ 0.4Nd_ 0.06Fe_ 1.94O_4 samples for their extremely small sizes.

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.

Effects of Cu and Co Substitution on the Properties of NiZn Ferrite Thin Films

Cu- and Co-substituted NiZn ferrite thin films, Ni0.4-xZn0.6CuxFe2O4 and Ni0.5Zn0.5CoxFe2-xO4 （0≤x≤0.2）, are synthesized by sol-gel process. The crystallographic and magnetic properties of Cu- and Co-substituted NiZn ferrite thin films have been investigated. The lattice parameter decreases with Cu substitution and increases with Co substitution. The saturation magnetization decreases and the coereivity increases with the increase of Cu substitution. Moreover, the saturation magnetization gradually increases with the increase of Co substitution when x≤0.10, but decreases when x〉0.10. Meanwhile, the coereivity initially decreases with the increase of Co substitution when x≤0.10, but increases when x〉0.10.

Effect of Sintering Temperature on Microwave Absorbing Behaviour of Mn-Zn Ferrite

The microwave absorbing behaviour of Mn-Zn ferrite sintered at 1100,1200,1300,1400 and 1500℃ has been investigated.The phase constitution of the ferrite was analyzed by X-ray diffraction.The results show that the ferrite sintered at 1 500℃ has better microwave absorbing prop- erty than those prepared at other temperatures,due to the increase of turbulent loss generated by the formation of excessive Fe^(2+) in deoxidizing of Fe_2O_3 at high temperatures.

Remanence Enhancement Effect in Ni_(0.7)Zn_(0.3)Fe_2O_4/Co_(0.8)Fe_(2.2)O_4 Ferrite Multilayer Film

Ni0.7Zn0.3Fe2O4/Co0.8Fe2.2O4（NZFO/CFO） multilayer films are fabricated on Si（lO0） substrates by the chemical solution deposition method. The mierostructure and magnetic properties are systematically investigated. The results of field-emission scanning electronic microscopy show that the grain size of the NZFO/CFO multilayer film is quite uniform and the thickness is about 30Ohm. The remanence enhancement effect of the NZFO/CFO multilayer film can be mainly attributed to the exchange coupling interaction between NZFO and CFO ferrite films, which is in favor of the design and fabrication of modern electronic devices.

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).