Cu-Zn Ferrites Research Articles

Study of electrical properties of Cu-Zn ferrite with Si additive

Study of electrical properties of Cu-Zn ferrite with Si additive

Effect of Spacer Layer Thickness on the Magnetic Properties of $({\hbox {SnO}}_{2}/{\hbox {Cu–Zn}}\ {\hbox {Ferrite}})_{\rm n}$ Multilayers

Multilayers (ML) of SnO2 and Cu-Zn Ferrite were deposited by rf-sputtering. The effect of spacer layer (SnO2) thickness on the structural and magnetic properties of ML were studied. The disorder and strain in the system is found to increase with increasing spacer layer thickness. The interlayer coupling is found to decrease with increasing SnO2 layer thickness. The FMR intensity, magnetization and the exchange coupling strength initially increases then decreases with increasing SnO2 thickness. This behavior may be attributed to the oscillation in the exchange coupling across the non magnetic layer due to quantum interference of the electron waves reflected from the interfaces. The ML exhibit uniaxial anisotropy and the ML are found to be more homogeneous when the film normal is at an angle of 40° with the applied field. Decreasing magnetic moment and increasing resonance field at low temperatures indicated the presence of antiferromagnetic interactions in these ML.

Thermoelectric Power of Cu-Zn Ferrites

A series of Cu-Zn mixed ferrites with composition formula Cu1–xZnxFe2O4 is prepared by the double sintering ceramic technique. Thermoelectric power studies are performed over a temperature range of 300 to 800 k by a deferential method. The results showed a negative value for the Seebeck coefficient S for all samples, and all compositions exhibited an n-type semiconductors behavior in the measured range of temperature. The values of charge carrier concentration n and the Fermi energy were determined. The values of n were found to decrease as temperature increased, while Fermi energy directed to more negative values when Zn content is increased. On the basis of these results a mechanism for the conduction in Cu-Zn ferrites is suggested and the properties of the mention compounds were determined.

Synthesis, Structural and Physical Properties of Cu<sub>1–x</sub>Zn<sub>x</sub>Fe<sub>2</sub>O<sub>4</sub> Ferrites

Zn substituted Cu-Zn ferrites with a composition Cu1-xZnxFe2O4 have been synthesized by standard double sintering ceramic method and characterized by X-ray diffraction. The single-phase cubic spinel structure of all the samples has been confirmed from X-ray diffraction analyses. The lattice constant is found to increase linearly with the manganese content obeying Vegard’s law. This increase in lattice parameter is explained in terms of the sizes of component ions. It is well known that density plays a key role in controlling the properties of polycrystalline ferrites. The X-ray and bulk densities of the Cu-Zn ferrite is significantly decreased whereas porosity increased with increasing Zn concentration, thereby giving an impression that zinc might be helping in the densification of the materials. SEM micrographs exhibit a decrease in grain size with increasing Zn content. The real part of initial permeability, μ′ increase with increasing Zn contents upto x = 0.5 after that it decreases with higher Zn content.

The Influence of Si Additive on Structural and Microstructural Properties of Cu-Zn Ferrite System

Mixed Cu-Zn ferrites (for x = 0.66 to 0.99) are prepared by the double sintering ceramic method. Locally available low cost Fe2O3 with 0.5wt% of Si additive is used for this purpose which reduced the process price markedly and improves the properties of the ferrite produced. The chemical phase analysis carried out by X-ray powder diffraction method confirms the major phase of Cu-Zn ferrite structure. Lattice parameters, X-ray density and mass density along with porosity have been investigated to study the effect of composition. Lattice parameters shows a decreasing trend with increasing Cu content, x. whereas, both X-ray density and mass density increases with increasing x, which in turn decreases the porosity due to successive presence of Si in Fe2O3. This decrease in porosity along with chemical homogeneities, distribution of phases and grain formation were also observed from Scanning electron micrographs at different magnifications.

Electrical properties of low temperature sintered copper and titanium-codoped copper zinc ferrites

The effects of Cu and Ti substitution on the sintering behavior, substitution mechanism, resistivity and dielectric properties of CuZn ferrites were investigated. Codoped Cu 2+ and Ti 4+ can effectively reduce the densification temperature of copper zinc ferrite to below 900 °C and improve the resistivity and dielectric properties. The copper and titanium-codoped CuZn ferrites and NiCuZn ferrites exhibited excellent compatibilities in physical and chemical matching during cofiring. Therefore, the copper and titanium-codoped CuZn ferrites can be a good candidate material for an effective intermediate nonmagnetic layer for NiCuZn ferrites in preparing a multilayer chip inductor with a high rated current.

Low-Temperature Sintering and Electromagnetic Properties Evaluation of (Ni/Mn)CuZn Ferrite

Low temperature sintering (Ni/Mn)CuZn ferrite was employed at most cases due to its co-firability with Ag (below 960 °C).The purpose of this study is to fabricate (Ni/Mn)CuZn ferrite sintered body with high-strength and high-frequency magnetic properties. Following is the procedure: firstly, (Ni/Mn)CuZn ferrite powder was synthesized under CO2 atmosphere at 500 °C from the mixed doxalate synthesized by co-precipitation method; then a small amount of boric acid [H3BO3] was added to the powder, and the (Ni/Mn)CuZn ferrite powder compact was prepared with Newton press and CIP methods; finally, (Ni/Mn)CuZn ferrite sintered body was fabricated by sintering at 900 °C under CO2 atmosphere. By this method, NiCuZn and MnCuZn ferrite sintered bodies with 0.5 mass% boric acid were obtained, the strength are 430 and 530 MPa respectively. The effect of various Mn addition on NiCuZn electromagnetic properties were studied.

Improvement of the magnetic and electric properties of Cu-Zn ferrites

Polycrystalline Cu-Zn ferrites substituted with different rare-earth ions (R = La, Nd, Sm, and Gd) are investigated. The initial permeability and homogeneity increased for samples with R = Nd, Sm, and Gd relative to the unsubstituted one (US). On the other hand, the magnetization and energy loss are decreased for all substituted samples. The electrical resistivity increased only for samples with R = La and Nd relative to US.

流動層磁気アシスト比重分離法に関する基礎的研究

Feasibility study of magnetic separation of sample powders with small difference in their specific gravity, which was ineffective, was carried out by magnetic separation by focusing on the difference in their magnetic properties. An apparatus to separate the ferromagnetic particles from the mixed powder with small difference in its specific gravity was made. To investigate the relation between the sizes of the particles and separation efficiency, systematical examination of the separation ratio was done while changing the sizes of the ferromagnetic and paramagnetic particles. Successful separation of dry powders with small difference in their gravities was achieved in a magnetic field by using this apparatus. With a sample composed of a mixture of Cu-Zn ferrite and Al2O3 with the grain size of 45 μm, the separation efficiency of the Al2O3 was close to 100%. As the size of particles of the mixed powers became smaller, its separation efficiency decreased, which could be attributed to the aggregation/flocculation of each particle.

Improvement of the Magnetic and Electrical Properties of Cu-Zn Ferrites

Polycrystalline Cu-Zn ferrites substituted with different rare-earth ions (R = La, Nd, Sm, and Gd) are investigated. The initial permeability and homogeneity increased for samples with R = Nd, Sm, and Gd relative to the unsubstituted one (US). On the other hand, the magnetization and energy loss are decreased for all substituted samples. The electrical resistivity increased only for samples with R = La and Nd relative to US.

磁性材料 低温焼結ＮｉＣｕＺｎフェライト材料の開発と積層型チップフェライトの高性能化に関する研究

The incessant demand for higher density circuits in electronics has required the continued miniaturization of all components. As a solution, surface mount technology (SMT) was developed resulting in densification of component mounting. Therefore, efforts have been made to produce electronic components in surface mount device (SMD) form. Since the inductor had to be wound with wire, it was difficult to reduce the size of the chip without any deterioration of magnetic properties. Thick-film printing process and low temperature sintering NiCuZn ferrites due to its co-firability with Ag (below 900°C) were developed for multilayer chip inductors in 1980. It is known that NiZn ferrite has high resistance, and that CuZn ferrite is a low-fire composition, therefore NiCuZn ferrite was studied to combine both properties. Over the past decades a considerable number of studies have been made on the interface between Ag-conductor and ferrite, Ag-diffusion with specially reference to the micro/nano structure and electromagnetic properties of NiCuZn ferrite. Therefore, it was known that the controlling stress by the internal Ag-conductor and CuO1-x/Ag on ferrites grain boundary is most important key point for high performance multilayer chip ferrites as well as the chemical composition of ferrite.

磁性材料 低温焼結フェライトの線膨張係数の制御

A one-chip type transformer is produced as an MHD (Multilayer-Hybrid-Circuit-Device) using a multilayer technology and it contributes to miniaturize of a DC/DC converter. In order to get high efficiency of this transformer, it is needed to reduce the residual magnetic flux neighborhoods of internal electrode. Therefore, the internal electrode is needed to cover with nonmagnetic oxide completely in MHD. However, the discrepancy of thermal expansion coefficient between these materials produces internal stress which causes a degradation of magnetic properties and internal cracks in the worst case. Many studies were reported about internal stress effect comes from the internal Ag electrode to produce high performance multilayer chip inductor. In this paper, a study about the thermal expansion coefficient of ferrites was performed to reduce the thermal expansion coefficient discrepancy between NiCuZn ferrite and CuZn ferrite. It was found that the thermal expansion coefficient was able to control by ferrite compositions and degree of raw materials mixing. And it was thought that the thermal expansion coefficient was affected by ferrite compositions as well as thermal vibration which was caused from imperfect match at the interface between a spinet structure and a residual unreacted oxide materials in sintered ferrite body.

Effect of Sm substitution on the magnetic and electrical properties of Cu-Zn ferrite

Samples of the chemical formula Cu0.5Zn0.5Fe2−x SmxO4 where x = 0.0, 0.02, 0.04, 0.06, 0.08 and 0.1 are studied. X-rays analysis indicated that all investigated samples are formed in a single cubic phase. The lattice parameter is found to increase relative to x = 0.0 except x = 0.02. The grain size is decreased for all samples relative to unsubstituted one except that with x = 0.02. It is noticed that the sample with x = 0.02 has the highest values of initial permeability, magnetization and Curie temperature, Tc. The homogeneity of the samples, the coercive field as well as Tc are found to decrease while the electrical resistivity increases with increasing Sm content.

Magnetic Properties of Cu–Zn Ferrites Doped with Rare Earth Oxides

Samples of Cu-Zn ferrites doped with different rare earth ions (La, Sm, Nd, Gd, and Dy) are investigated. X-ray diffraction patterns indicated the presence of a single spinel phase. The lattice parameter is found to be nearly independent of the doped rare earth ion type. The density is measured and the porosity is calculated for each sample. The magnetization is measured on toroidal samples using the induction method. The initial permeability μ i is measured as a function of temperature at a constant frequency of 10 kHz and the Curie temperature T C is determined. The variations of magnetization, relative permeability and the initial permeability as a function of the effective magnetic moment of the doped rare earth ion are discussed.

Magnetic ordering in Cu-Zn ferrite

The variation of magnetization with temperature of the ZnxCu1−xFe2O4 system has been obtained between 300 K and the Neel temperature at a constant magnetic field of 5.57×105 A m−1 for x=0 to 0.8. The observations indicate the existence of a Yafet-Kittel (Y-K) type of magnetic ordering in the mixed ferrites. A molecular field analysis of the Y-K spin-ordering using a three-sublattice model is shown to explain the experimental data satisfactorily. For the sake of verification, Neel temperatures of Cu-Zn ferrites were also determined from Mossbauer studies.

Time Decrease of Magnetic Permeability in Some Mixed Ferrites

The time decrease of the magnetic permeability after demagnetization, or disaccomodation, was measured for Mn-Zn, Ni-Zn, Cu-Zn and Mg-Zn ceramic ferrites. Considerable disaccomodation was observed with samples containing Fe 2 O 3 over the stoichiometric composition. In the case of Mg-Zn ferrites, the disaccomodation is remarkable on both sides of the stoichiometric composition, where it is fairly small. For the specimens sintered in air, the disaccomodation is larger for higher electrical-conductive specimens, while such a correlation to the conductivity disappeared after the specimens were annealed in the nitrogen atmosphere. A single crystal of Ni-Zn ferrite, which is supposed to contain a very small amount of vacancies, also shows a very small disaccomodation. The activation energy determined from the disaccomodation measurements is about 0.5–0.8 eV for Mg-Zn ferrites. It is suggested that the displacement of either vacancies or interstitial ions may possibly be a main origin of the phenomenon.