NiCuZn Ferrite Powders Research Articles

Synthesis of NiCuZn ferrite nanoparticles from metallic nitrate solutions using the microwave direct denitration method and evaluation of its properties

NiCuZn ferrite nanoparticles having the chemical composition Ni0.5Cu0.1Zn0.4Fe2O4 were synthesized by the microwave direct denitration (MDD) method from a mixture of metal nitrate hydrate solutions. A single-phase of NiCuZn ferrite powder with an average particle diameter of about 30 nm could be obtained using this method at reaction temperatures higher than 900 °C. This diameter was less than one-fifth of that obtained by the conventional solid-state reaction (SSR) method. Therefore, the NiCuZn ferrite synthesized by MDD method had a higher sinterability than the SSR method. It was categorized as a soft ferromagnetic material and its saturation magnetization was three times more than of the SSR. Its coercivity was about half of that by the SSR method. For the NiCuZn ferrite sintered with Bi2O3 additive, the saturation magnetization obtained from the MDD method was about 80% of that of the SSR method, while the coercivity was almost identical.

NiCuZn Ferrite Cores by Gelcasting: Processing and Properties

We used gelcasting, a pressure-less processing technology for fabricating ceramic parts, to make NiCuZn ferrite cores, which are traditionally made by a process that requires high hydrostatic pressure. A commercial NiCuZn ferrite powder was mixed with water, dispersant, and organic monomers to form a slurry, and then cast it into a mold of toroid shape followed by sintering at 900 °C, 950 °C, and 1000 °C for two hours. The sintered core mass density was found to increase with sintering temperature. The magnetic properties of the cores, i.e., complex permeability and core-loss density, were measured. We found that the real part of the permeability increased with sintering temperature from about 44 at 900 °C to 78 at 1000 °C. The core-loss density data at 5 MHz showed that the cores sintered at 950 °C had the lowest core-loss density; approximately 50% lower than that of a commercial NiZn ferrite (4F1) core. Since gelcasting does not require pressure and is scalable and low cost, it has the potential to make magnetic cores with intricate shapes and sizes for desired coupling of magnetic fluxes to improve efficiency and power-density of power electronics converters.

Microwave sintering versus conventional sintering of NiCuZn ferrites. Part I: Densification evolution

This work reports the recent study on the microwave sintering (MS) versus conventional sintering (CS) of NiCuZn ferrites, with particular interests in the densification evolution. NiCuZn ferrite powders were synthesized through the solid state reaction route. Densification behaviors of ferrite samples under the two types of thermal sources were monitored in real-time. Meanwhile, the influences of additives (1wt% BSZ glass or 1wt% Bi2O3) on the densifications were also investigated. Both constant heating rate (CHR) and master sintering curve (MSC) models were used to evaluate the sintering activation energy (Q). Results demonstrated that the microwave-enhanced diffusion mainly occurs at the intermediate sintering stage. The Q-value estimated by MSC method agreed well with that from CHR method. With the influence of microwave electromagnetic field, the activation energy of NiCuZn ferrites was decreased by roughly 100–150kJ/mol. In addition, doping a small amount of additives could improve densification degree and reduce the minimal energy to activate diffusion mechanisms.

Synthesis of NiCuZn-ferrite powders by means of mechanochemical treatment

NiCuZn-ferrite powders were synthesized by mechanochemical treatments using NiCO3⋅2Ni(OH)2⋅4H2O, CuO, ZnO and Fe2O3 as raw materials. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and vibrating sample magnetometer (VSM) were employed to evaluate the morphologies and structures of samples. The results indicated that the mechanochemical treatment produced several structural and chemical effects on reactants of the powder mixtures, and single phase Ni0.45Cu0.05Zn0.5Fe2O4 could be obtained after annealed at 700°C for 2h. In comparison with the traditional firing method, the mechanochemical method benefited achieving the lower Ms and μi, which indicated that the sample had better magnetic properties.

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 °C∼1000 °C. The results show that NiCuZn ferrite powders with single spinel phase can be formed after heat-treating at 750 °C. Powders obtained from Ni0.4Cu0.2Zn0.4Fe1.9O4 gel have better magnetic properties than those from gels with other composition. After heat-treating at 900 °C for 3 h, coercivity Hc and saturation magnetization Ms are 9.7 Oe (1 Oe = 80 A/m) and 72.4 emu/g, respectively. Different from the powders, NiCuZn films produced on Si (100) from the Ni0.4Cu0.2Zn0.4Fe2O4 gel formed at room temperature possess high properties. When heat-treating condition is around 600 °C for 6 min, samples with low Hc and high Ms will be obtained. The minimal Hc is 16.7 Oe 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.

Evaluation of the Electromagnetic Characteristics on Ag/NiCuZn Ferrite Sintered Bodies

Recently, the surface mounting devices (SMD) have been rapidly developed for miniaturisation of electronic applications such as cellular phones, cameras, computers, etc. Low temperature sintering NiCuZn and MnCuZn ferrite was employed at most cases due to its co-firability with Ag (below 960OC).The purpose of this study is to fabricate NiCuZn and MnCuZn ferrite sintered body with high-strength and high-frequency magnetic properties. Following is the procedure: firstly, NiCuZn and MnCuZn ferrite powder were synthesized under CO2 atmosphere at 500 OC from the mixed doxalate synthesized by liquid phase deposition method; then a small amount of boric acid [H3BO3] was added to the powder, and the NiCuZn and MnCuZn ferrite powder compact were prepared with Newton press and CIP methods; finally, NiCuZn and MnCuZn ferrite sintered body was fabricated by sintering at 900 OC under CO2 atmosphere. The effect of boric acid additives on growth of particle and sintering temperature were discussed. The high frequency magnetic properties and density as well as bending strength of the NiCuZn and MnCuZn sintered magnet with various adding of H3BO3 as well as at various sintered temperatures were evaluated by using Impedance analyzer, TMA (Thermo Mechanical Analyzer), TEM (Transmission Electronic Microscopy) and 3-point bending test. From the evaluated results, the most suitable producing conditions were determined and NiCuZn ferrite with wider scope of high frequency and high bending strength were obtained.

Synthesis and electromagnetic properties of PZTS–NCZF composites

In order to adjust the initial permeability and the dielectric constant for suppressing electromagnetic interference (EMI), a series of the composites with Pb 0.95Sr 0.05(Zr 0.52Ti 0.48)O 3 (PZTS) powders and NiCuZn ferrite (NCZF) powders as raw materials were synthesized by a solid-state reaction method. The effects of different PZTS content on the sintering behaviors, phase composition, microstructures and electromagnetic properties of the composites co-fired at 900 °C were investigated. The acquired ferroelectric–ferromagnetic composites are of perovskite phase and spinel phase, exhibiting both capacitance and inductance properties and excellent frequency stability due to the mutual effects of magnetization of NCZF phase and the polarization of PZTS phase. As PZTS content increased, the initial permeability and the saturation magnetism (B m) decreased gradually, the coercive force (Hcb) and the quality factor (Q) increased, the resonance frequency shifts toward a higher frequency. Simultaneously, the dielectric constant evidently increased with PZTS content when x varied from 0 to 50 wt%. A maximum Q-factor (50), a maximum dielectric constant (80), a higher DC resistivity (4.96 × 10 10 Ω m), a higher ferromagnetic resonance frequency (over 1.8 GHz) and a relatively higher initial permeability (5–7) were obtained for the composite with 50 wt% PZTS.

Microwave-Hydrothermal synthesis of BaTiO 3 + NiCuZnFe 2O 4 nanocomposites

The nano-sized BaTiO 3 and NiCuZn ferrite powders were synthesized using Microwave-Hydrothermal (M-H) system at 160 °C/45 min. The ferroelectric and ferrite phases were confirmed by the XRD and surface morphologies were studied by SEM and TEM. The size of the powders that were synthesized using M-H system was found to be 40–60 nm. The xBaTiO 3 + (1 − x)NiCuZnFe 2O 4 nano-composites were prepared at different weight percentages. The room temperature hysteresis loops were taken on the present composite samples in the field of 5 kOe. The value of coercivity and saturation magnetization was found to be increasing with the decrease of BaTiO 3 content in the composites. The frequency variation dielectric constant ( ɛ), dissipation factor ( D), initial permeability ( μ i) and quality factor ( Q) were studied at room temperature in the frequency range of 1 kHz–1 MHz region. From these studies it was observed that the present composites were useful for the fabrication of Multilayer Chip Inductors (MLCI).

Characterization of nanocrystalline NiCuZn ferrite powders synthesized by sol–gel auto-combustion method

The ferrite compositions Ni0.8−xCu0.2ZnxFe2O4 with x = 0.5, 0.55 and 0.6, were synthesized through nitrate–citrate gel auto-combustion method. The autocatalytic nature of the combustion process has been studied by thermal analysis (DTA and TG) of the dried gels. The powders were calcined at 700 °C/2 h and then pressed ferrite parts were sintered at 900 °C/4 h. The ferrite was characterized with respect to phase identification, crystallite size and lattice parameter determination using X-ray diffraction. As-burnt powders showed the presence of crystalline cubic spinel ferrite with about 19–22 nm crystallite sizes. The densification characteristic of the powder was investigated using TMA. The sintered ferrite was characterized for permeability, saturation magnetization, relative loss and ac resistivity measurements. The permeability and magnetization were found to increase and magnetic loss, ac resistivity were decreased with Zn substitution for Ni. The powder is suitable for the application in multilayer chip inductor due to its low temperature sinterability, good magnetic properties and low loss at high frequency.

A New Low-Temperature Sintering Method for NiCuZn Ferrite

Low temperature sintering NiCuZn ferrite was employed at most cases due to its co-firability with Ag (below 960°C). The purpose of this study is to fabricate NiCuZn ferrite sintered body with high-strength and high-frequency magnetic properties. Following is the procedure: firstly, NiCuZn ferrite powder was synthesized under CO2 atmosphere at 500°C from the mixed doxalate synthesized by liquid phase deposition method; then a small amount of boric acid [H3BO3] was added to the powder, and the NiCuZn ferrite powder compact was prepared with Newton press and CIP methods; finally, NiCuZn ferrite sintered body was fabricated by sintering at 900°C under CO2 atmosphere. By this method, NiCuZn ferrite sintered body with 0.5 mass% boric acid was obtained, which was additive with strength 340 MPa, high frequency applied scope below 20MHz and initial permeability 38.

Low-temperature sintering method for NiCuZn ferrite and effect of Mn addition on electromagnetic properties

Low temperature sintering NiCuZn ferrite was employed at most cases due to its co-firability with Ag (below 960 °C). The NiCuZn ferrite sintered body with high-strength and high-frequency magnetic properties was fabricated. Firstly, NiCuZn ferrite powder was synthesized under CO 2 atmosphere at 500 °C from the mixed doxalate synthesized by liquid phase precipitation method. Then a small amount of boric acid (H 3BO 3) was added to the powder, and the NiCuZn ferrite powder compact was prepared with Newton press and CIP methods. Finally, NiCuZn ferrite sintered body was fabricated by sintering at 900 °C under CO 2 atmosphere. The minimum sintering temperature (800 °C) was determined by the study of high temperature shrinkage. By this method, NiCuZn ferrite sintered body with 0.5% (mass fraction) boric acid was obtained, which has the bending strength of 340 MPa. The effect of various Mn addition on electromagnetic properties were studied.

ＮｉＣｕＺｎフェライト焼結体の低温作製とその材料特性評価

NiCuZn ferrite has been widely applied to multilayer chip inductors in recent years. While fabricating the multilayer structure of ferrite and metal alternatively, it is requested to simultaneously sinter in low temperature for the internal conductor Ag (Melting point 960°C) and ferrite materials. The purpose of this study is to fabricate the NiCuZn ferrite sintered body with high-strength and high-frequency magnetic property. The procedures are as follows: firstly, the NiCuZn ferrite powder was synthesized under a CO2 atmosphere at 500°C from the mixed doxalate which was synthesized by liquid phase deposition method from mixed metal chloride and ammonium oxalate; subsequently, a small amount of boric acid [H3BO3] was added to the powder, and then the NiCuZn ferrite powder compact was formed with Newton press and CIP methods; finally, the NiCuZn ferrite sintered body was fabricated by sintering at 900°C under a CO2 atmosphere. Through the experiments of high temperature shrinkage, evaluation of mechanical strength and magnetic property, NiCuZn ferrite fabricated by this study can present good characters on high frequency and high mechanical strength when the sintering temperature and boric acid additive are 900°C and 0.5 mass%, respectively.

Combustion synthesis and characterization of NiCuZn ferrite powders

In this paper, the feasibility of synthesizing NiCuZn ferrite powders by combustion synthesis (CS) reaction is demonstrated through igniting the mixtures of iron, iron oxide, copper oxide, zinc oxide and copper carbonate under different oxygen pressure values. The ferrite powders produced directly from the CS reaction and after annealing at 800 °C for 2 h are characterized by XRD, SEM, XPS and VSM. The results show that the spinel phase in the combustion products increases with the decrease of the diluent content and the increase of the oxygen pressure. Heating the as-synthesized ferrite at 800 °C for 2 h affords pure crystalline NiCuZn ferrite, which possesses better magnetic properties. XPS studies confirm that copper ions in the as-synthesized ferrite are present in the different ionic states of the A- and B-sites, while copper ion is divalent in the B-sites only for the annealed products.

Preparation of NiCuZn ferrite nanoparticles from chemical co-precipitation method and the magnetic properties after sintering

NiCuZn ferrite nanoparticles with composition of Ni x Cu y Zn 1− x− y Fe 2O 4 (where x=0.15–0.5 and y=0–0.35) were prepared by the chemical co-precipitation method at various reaction temperatures with a final pH value of 12. From the analysis of X-ray diffraction patterns, the nanocrystalline NiCuZn ferrite particles could be obtained at pH=12 and reaction temperature between 30 and 90 °C with the reaction time of 6 h. The particle size ranges from 2 to 60 nm by observation of transmission electron microscopy. Uniform size of cubic crystalline particles with particle size of about 30 nm were obtained at reaction temperature of 70 °C. The ferrite powders were compressed and sintered at various temperatures between 800 and 1000 °C for 2 h. According to experimental results, the NiCuZn ferrite powders with high Cu content could be sintered at about 800 °C. The density of the sintered Ni 0.18Cu 0.31Zn 0.51Fe 2O 4 ferrite was 5.01 g/cm 3 after sintering at 900 °C. The initial permeability μ of this sintered sample is about 390 at frequency of 1 MHz. Its H c value is about 0.7 Oe and B s≅3100 G. We found that Cu substitution for Ni in NiZn ferrite would enhance the densification of the ferrite and subsequently increases the μ value as well as B s value, and decreases the H c value of the sintered ferrite.

Preparation of NiCuZn ferrite nanoparticles from chemical co-precipitation method and the magnetic properties after sintering

NiCuZn ferrite nanoparticles with composition of Ni x Cu y Zn 1− x − y Fe 2 O 4 (where x =0.15–0.5 and y =0–0.35) were prepared by the chemical co-precipitation method at various reaction temperatures with a final pH value of 12. From the analysis of X-ray diffraction patterns, the nanocrystalline NiCuZn ferrite particles could be obtained at pH=12 and reaction temperature between 30 and 90 °C with the reaction time of 6 h. The particle size ranges from 2 to 60 nm by observation of transmission electron microscopy. Uniform size of cubic crystalline particles with particle size of about 30 nm were obtained at reaction temperature of 70 °C. The ferrite powders were compressed and sintered at various temperatures between 800 and 1000 °C for 2 h. According to experimental results, the NiCuZn ferrite powders with high Cu content could be sintered at about 800 °C. The density of the sintered Ni 0.18 Cu 0.31 Zn 0.51 Fe 2 O 4 ferrite was 5.01 g/cm 3 after sintering at 900 °C. The initial permeability μ of this sintered sample is about 390 at frequency of 1 MHz. Its H c value is about 0.7 Oe and B s ≅3100 G. We found that Cu substitution for Ni in NiZn ferrite would enhance the densification of the ferrite and subsequently increases the μ value as well as B s value, and decreases the H c value of the sintered ferrite.

Preparation and electromagnetic properties of low-temperature sintered ferroelectric–ferrite composite ceramics

For the purpose of multilayer chip EMI filters, the new ferroelectric–ferrite composite ceramics were prepared by mixing PMZNT relaxor ferroelectric powder with composition of 0.85Pb(Mg1/3Nb2/3)O3–0.1Pb(Ni1/3Nb2/3)O3–0.05PbTiO3 and NiCuZn ferrite powder with composition of (Ni0.20Cu0.20Zn0.60)O(Fe2O3)0.97 at low sintering temperatures. A small amount of Bi2O3 was added to low sintering temperature. Consequently, the dense composite ceramics were obtained at relative low sintering temperatures, which were lower than 940°C. The X-ray diffractometer (XRD) identifications showed that the sintered ceramics retained the presence of distinct ferroelectric and ferrite phases. The sintering studies and scanning electron microscope (SEM) observations revealed that the co-existed two phases affect the sintering behavior and grain growth of components. The electromagnetic properties, such as dielectric constant and initial permeability, change continuously between those of two components. Thus, the low-temperature sintered ferroelectric–ferrite composite ceramics with tunable electromagnetic properties were prepared by adjusting the relative content of two components. These materials can be used for multilayer chip EMI filters with various properties.

The influence of Mn dopant on the electromagnetic properties of NiCuZn ferrite

In this paper, a citrate precursor method was used to prepare nano-sized NiCuZn ferrite powders with a composition of (Ni 0.15Cu 0.2Zn 0.65O)(Fe 2− x Mn x O 3+0.5 x ) 0.99, ( x = 0–0.04). Because of excellent sintering activity, the nanocrystals can be sintered below 900 °C without the addition of sintering aids. The effect of Mn dopant on the microstructures and the initial permeability was investigated. The results show that the introduction of Mn into NiCuZn ferrite has a great influence on its electromagnetic properties. The initial permeability of NiCuZn ferrite increases greatly with a small amount of Mn addition firstly, and then further increase of Mn content leads to a decrease in the initial permeability. By changing the content of Mn addition, the useful frequency dependence of initial permeability could be adjusted in a range of frequency from several hundreds of kilohertzs to several megahertzs.

Synthesis of nanocrystilline ferrites by sol–gel combustion process: the influence of pH value of solution

The dried nitrate–citrate gels exhibit auto-catalytic combustion behavior, which can be used to synthesize the nanocrystalline ferrite powders. In this study, NiCuZn ferrite nanocrystalline powders with composition of (Ni 0.25Cu 0.25Zn 0.5)O(Fe 2O 3) 0.98 were synthesized by a sol–gel auto-catalytic combustion process. The influences of pH value of the precursor solution on the gel morphology, combustion behavior and crystallite size of synthesized powders were investigated with the help of scanning electron microscopy observation, thermal analysis, infrared (IR) spectra and X-ray diffraction technique. The experiments showed that the pH value of the mixed precursor solutions has a significant influence on the morphology of dried gels. The high porous precursors with network structure can be formed at high pH values after the solutions were dried at 135°C. With increasing pH value, the combustion rate is increased significantly. The as-burnt powders become uniform in size and the crystallites size is increased from 26 to 48 nm with pH value increasing from 2 to 7. The combustion reaction mechanisms were put forward with the help of IR spectra and differential thermal analysis techniques.

Synthesis of nanocrystalline NiCuZn ferrite powders by sol–gel auto-combustion method

A nitrate–citrate gel was prepared from metal nitrates and citric acid by sol–gel process, in order to synthesize Ni 0.25Cu 0.25Zn 0.50Fe 2O 4 ferrite. The thermal decomposition process was investigated by DTA-TG, IR and XRD techniques. The results revealed that the nitrate–citrate gel exhibits self-propagating combustion behavior. After combustion, the gel directly transformed into single-phase, nano-sized NiCuZn ferrite particles with spinel crystal structure. The synthesized powder can be densified at a temperature lower than 900°C. The sintered body possesses fine-grained microstructure, good frequency stability and high-quality factor compared to the sample prepared by conventional ceramic route.

Preparation and characterization of NiCuZn ferrite nanocrystalline powders by auto-combustion of nitrate–citrate gels

A novel nitrate–citrate gel process was used to synthesize NiCuZn ferrite powders. The thermal decomposition and combustion process of nitrate–citrate gels were investigated by using DTA-TG, IR spectra and XRD techniques. The results revealed that the nitrate–citrate gels exhibit self-propagating behavior after ignition in air at room temperature. NiCuZn ferrite powders with a particle size of 20–50 nm were directly formed after combustion. The ratio of metal nitrates to citric acid in the starting solution affects the combustion process, and then determines the particle size of the as-synthesized powder. The magnetic structure of powders was characterized using Mössbauer spectroscopy.