NiCuZn Ferrites Research Articles

Ag and Cu Precipitaion in Multi-Layer Chip Inductors Prepared with V2O5-Doped NiCuZn Ferrites

The purpose of this study is to investigate the effect of <TEX>$V_2$</TEX><TEX>$O_{5}$</TEX> addition on the Ag and Cu precipitation in the NiCuZn ferrite layers of 7.7<TEX>${\times}$</TEX>4.5<TEX>${\times}$</TEX>1.0 mm sized multi-layer chip inductors prepared by the screen printing method using 0∼0.5 wt% <TEX>$V_2$</TEX><TEX>$O_{5}$</TEX> -doped ferrite pastes. With increasing the <TEX>$V_2$</TEX><TEX>$O_{5}$</TEX> content and sintering temperature, Ag and Cu oxide coprecipitated more and more at the polished surface of ferrite layers during re-annealing at <TEX>$840^{\circ}C$</TEX>. It was thought that during the sintering process, V dissolved in the NiCuZn ferrite lattice and the Ag-Cu liquid phase of low melting point was formed in the ferrite layers due to the Cu segregation from the ferrite lattice and Ag diffusion from the internal electrode. During re-annealing at <TEX>$840^{\circ}C$</TEX>, the Ag-Cu liquid phase came out the polished surface of ferrite layers, and was decomposed into the isolated Ag particles and the Cu oxide phase during the cooling process.

A Study on the Effect of Low-loss Additives on the Property of NiCuZn Ferrite

The electromagnetic properties and microstructures of the ferrites based on ( )() were investigated by changing the amount of additive SnOand CaO and the sintering temperatures. Addition of caused pores in the specimen. There was no variation of grain size by changing the amount of additives. Total loss was reduced when ( ) () composition was sintered at rather than . Addition of CaO was useful to reduce the total loss because it increased the sintering density. The lowest total loss was obtained when 0.06 wt% and 0.4 wt% CaO were added at the same time.

Magnetic and electrical properties of low-temperature sintered Mn-doped NiCuZn ferrites

Mn-doped NiCuZn ferrites with compositions of (Ni 0.25− x Mn x Cu 0.25Zn 0.5)O(Fe 2O 3) 0.98 (where x=0.02, 0.04, 0.06, 0.08, 0.10) were prepared by usual ceramic method. Initial permeability ( μ i ′ and μ i ″), DC resistivity ( ρ DC), dielectric constant ( ε′) and dielectric loss tangent (tan δ) were measured as a function of frequency and temperature. With increasing MnO 2 content, the resonant frequency and the Curie temperature decrease, whereas the μ i ′ increases first and decreases after it takes a maximum at MnO 2 content of 0.06. The ε′ and tan δ show a decrease with the increase of frequency for all the samples and the dielectric dispersion is enhanced with increasing MnO 2 content. On increasing temperature, the ε′ and tan δ are increased significantly, especially for samples with higher MnO 2 content. The ρ DC and conduction activation energy decrease with the increase of MnO 2 content. The possible mechanism for the influence of MnO 2 on the electromagnetic properties was discussed.

CuO 대신 Cu 미분말 치환이 NiCuZn Ferrite에 미치는 영향에 관한 연구

Cu 금속 미분말은 확산속도가 CuO 보다 CuO 보다 빠르고 소결시 입자성장을 촉진시키기 때문에 기본조성 (N <TEX>$i_{0.204}$</TEX>C <TEX>$u_{0.204}$</TEX>Z <TEX>$n_{0.612}$</TEX> <TEX>$O_{1.02}$</TEX>)F <TEX>$e_{1.98}$</TEX> <TEX>$O_{2.98}$</TEX>에 들어가는 CuO대신 Cu/CuO의 비를 변화시켜 가면서 Cu가 ferrite에 미치는 영향을 조사하였다. Cu를 CuO 대신 치환함으로써 90<TEX>$0^{\circ}C$</TEX>에서 완전한 Spinel구조를 가짐을 XRD pattern을 통하여 확인하였고, Cu/CuO 비가 60%일 때가 투자율 1100, Ms 87 emu/g의 최적조건을 얻었다. Cu는 소결시 확산속도를 증가시켜 입자성장에 영향을 주었으며, CuO대신 Cu의 치환은 저온에서 투자율이 개선됨을 확인하고 소결온도를 3<TEX>$0^{\circ}C$</TEX>이상 낮출 수 있었다. 소결이 끝난 후에는 CuO와 같은 거동을 하는 것으로 확인되었다. Diffusion speed of Cu metal fine particle is fast better than CuO, so it will promote grain growth in sintering. In this paper, the influence on substituting Cu fine particle for CuO of NiCuZn ferrite with basic composition (N <TEX>$i_{0.204}$</TEX>C <TEX>$u_{0.204}$</TEX>Z <TEX>$n_{0.612}$</TEX> <TEX>$O_{1.02}$</TEX>)F <TEX>$e_{1.98}$</TEX> <TEX>$O_{2.98}$</TEX> has been investigated with varying Cu/CuO ratio. The perfect spinel structure of sintered specimen at 90<TEX>$0^{\circ}C$</TEX> was confirmed by the analysis of XRD patterns. The best condition was obtained when the ratio of Cu/CuO was 60%, and the permeability was 1100 and Ms was 87 emu/g in this condition. Cu has influenced on grain growth in sintering, substituting Cu fine particle for CuO could lower sintering temperature over the 3<TEX>$0^{\circ}C$</TEX>. After sintering, substituting Cu performed as good as CuO.s CuO.s CuO.

High Mn content NiCuZn ferrite for multiplayer chip inductor application

The effect of Mn substitution on the magnetic properties and microstructure of the (Ni 0.2Cu 0.2Zn 0.6) 1.03(Fe 2O 3) 0.97+0.97 xMnO 2 ( x=0.1–0.5) ferrite sintered at 890 °C were investigated. Mn content increases the initial permeability, but Mn≥0.4 results in the formation of a second phase. The temperature coefficient of initial permeability is strongly affected by the Mn content. When x≥0.3, the temperature coefficient of initial permeability increases quickly. The ferrite can be used in multi-layer chip inductor.

Effect of Mn substitution on the magnetic properties of MgCuZn ferrites

A series of Mn substituted MgCuZn ferrites (Mg 0.2Cu 0.2Zn 0.6O) (Fe 2− x Mn x O 3) 0.97 with x=0.00,0.01,0.03,0.05,0.07 were prepared with nanosized precursor powders synthesized by a sol–gel auto-combustion method. All the ceramic samples can be sintered at low temperature (930°C) (below the melt point of Ag (961°C)). The effect of Mn content on microstructures and magnetic properties were investigated. Experiment shows that low temperature sintered MgCuZn ferrites doped with Mn possess higher initial permeability and better grain structure than that of low temperature sintered NiCuZn ferrites prepared by the same method. Therefor, Mn doped MgCuZn ferrites should be ideal materials for high inductance multilayer chip inductor. It is thought that the variation of initial permeability of MgCuZn ferrites with the Mn substitution was attributed to the decrease of magnetostriction constant.

The development and analysis of property–composition diagrams on gel-derived stoichiometric NiCuZn ferrite

Nineteen basic powders were produced for the development of ternary property–composition diagrams. The diagrams are useful for material selection for applications under specific conditions. Analysis of the diagrams and dilatometric data indicated the existence of a critical region of CuO content at 12–20 mol%. Powders of CuO content within the critical region showed the best properties. The diagrams showed that high NiO content was associated with the deterioration of the electromagnetic properties. It was felt likely that NiO is a densification retardant during sintering, whereas CuO improved densification and hence reduced the sintering temperature via small degree of spinel dissociation. High ZnO content was necessary to give ferrites with good properties. Good electromagnetic properties in the ferrites were attributed to low NiO, moderate CuO and high ZnO contents.

Electromagnetic properties of gel-derived NiCuZn ferrites

NiCuZn ferrites could be sintered at a relatively low temperature as compared to other ferrites, because their spinel crystals will be dissociated when the CuO content is relatively high. The dissociation occurs at temperatures around 900°C and facilitates the densification, causes the suitable ferrites to be used for multilayer application with silver as the internal conductor. Initial increase in CuO content causes a decrease in the dissociation temperature and is beneficial benefit to the electromagnetic properties as a result of grain growth and better densification. CuO content exceeds the critical value when it brings in unwanted electromagnetic properties of the ferrite products. The range of critical CuO content was determined to be 12–20 mol%.

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.

Interface and ionic interdiffusion in cofired ferroelectric/ferrite multilayer composites

Recently, the surface mount technology (SMT) has been rapidly developed for miniaturization of electric devices such as multilayer ceramic capacitor (MLCC) and multilayer chip inductor (MLCI). The trend of electronics has been for an increasingly compact design. Some characterizations of cofired devices such as ceramic-filled glass electronic package, and varistorcapacitor cofired multilayer device have been reported [1, 2]. Multilayer chip LC filter, which is combined with several capacitors and inductors by the production process of multilayer chip components, is a type of advanced surface mount devices (SMD). Lead based relaxor ferroelectrics, such as Pb(Mg1/3Nb2/3)O3, Pb(Ni1/3Nb2/3)O3 and Pb(Zn1/3Nb2/3)O3, are being widely used as MLCC due to their high dielectric constant and low sintering temperature [3–5]. And NiCuZn ferrite, which has excellent magnetic permeability and can be densified at low temperature, is an important material using for producing low temperature sintered MLCI [6–8]. They are promising materials for the multilayer chip LC filters. The key issue of manufacturing the multilayer chip LC filters is cofiring the capacitor and inductors together at low temperature. The interfacial interactions such as chemical reaction, ionic interdiffusion, are important for the production of devices. In the present study, the multilayer components were prepared by cofiring Pb(Ni1/3Nb2/3)O3-PbTiO3 (abbreviated as PNNT) ferroelectrics and NiCuZn ferrite. The cofiring interface and ionic interdiffusion between constituents were investigated. According to the diffusioncouple model, the interfacial diffusion coefficient for Pb2+, Nb5+, Ni2+, and Fe3+ had been estimated. The specimens were prepared by the conventional oxide-mixing technique. 99% pure reagent-grade PbO, NiO, Nb2O5, TiO2, Fe2O3, CuO, and ZnO oxides were weighed in the appropriate proportions and used as starting materials. Fe2O3, NiO, CuO and ZnO powders, according to the composition (Ni0.8Cu0.1Zn0.1)Fe2O4, were calcined at 720 ◦C for 4 h to fabricate NiCuZn ferrite. The dielectric material, according to the composition 0.8 Pb(Ni1/3Nb2/3)O3-0.2PbTiO3 with little amount of CuO and ZnO, were calcined at 800 ◦C for 4 h. The calcined mixtures were ground by ball milling for 12 h to a proper surface area. The ground powders were dried and added to PVA for the disk bodies. Firstly, ferroelectic and ferrite disks were separately prepared and sintered at 850–950 ◦C for 2 h, in order to measure characteristics such as phase structure and sintered densities. Secondly, the mixed calcined powders of ferroelectric and ferrite were laminated into a mold and compressed into a plate with the diameter of 12 mm, which was sintered at 950 ◦C for 2 h. The sintered densities were measured by the Archimedes method. The phase structure for the specimens were identified using X-ray diffractometer (XRD). For lead-based ferroelectrics, perovskite phase and pyrochlore phase always coexist. The relative amounts of perovskite and pyrochlore phases were determined by measuring the major X-ray peak intensities for perovskite and pyrochlore phases, i.e. (110) and (222), respectively. The percentage of perovskite phase was calculated by the following equation [9]:

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.

Low temperature sintering of NiCuZn ferrite and its electrical, magnetic and elastic properties

Low temperature sintering of NiCuZn ferrite and its electrical, magnetic and elastic properties

Microwave Sintering Study of NiCuZn Ferrite Ceramics and Devices

Studies on the sintering behavior, including densification and grain growth of NiCuZn ferrite ceramics were carried out in a microwave field of 2.45 GHz. Compared to conventional sintering, the shrinkage curves of a NiCuZn ferrite system processed by microwave sintering were observed to have shifted towards approximately 100°C lower temperatures. From the analysis of shrinkage data, it was found that the effective activation energy for diffusion under the microwave sintering was lower than those controlled under conventional sintering. In addition, pressed toroidal inductors and multilayer chip inductors (MLCI) have also been sintered by the microwave processing. Although heating rate of the microwave sintering was faster than that of the conventional sintering, the microwave sintered samples were found to be without any visible cracks. The total sintering time was reduced significantly in comparison with the conventional sintering. In both the sintered toroidals and MLCI samples, comparable magnetic properties were obtained.

Liquid phase sintering of NiCuZn ferrite and its magnetic properties

The influence of glass additives on the densification, microstructural evolution and magnetic properties of NiCuZn ferrites were investigated. Two glass systems including PbO·SiO2 and PbO·B2O3 were used to reduce the sintering temperature of a NiCuZn ferrite. The PbO·SiO2 glass system was shown to be an effective additive to obstruct the grain boundary movement and prevent the abnormal grain growth. In addition, it significantly lowers the sintering temperature of the ferrite. Ferrites sintered with PbO·SiO2 have higher resistivity, higher Q and higher Hc compared with those of PbO·B2O3 systems. These results also indicated that the ratio of modifier to glass-former did not significantly change the densification behavior, microstructural evolution and magnetic properties of the NiCuZn ferrite.

Effects of MnO 2 on the electromagnetic properties of NiCuZn ferrites prepared by sol-gel auto-combustion

Mn-doped NiCuZn ferrites with compositions of (Ni 0.2Cu 0.2Zn 0.6)O(Fe 2− x ,Mn x O 3) 0.98 ( x=0, 0.02, 0.04, 0.06) were prepared by a novel sol–gel auto-combustion process. The synthesized nano-sized ferrite powders can be sintered at 900°C, and the sintered ferrites are characterized by fine-grained microstructural feature and high permeability. Mn content in formulations largely affects the grain size and main electromagnetic properties of sintered NiCuZn ferrites. With increasing Mn content, the initial permeability is significantly increased, while the electrical resistivity and quality factor are decreased. The dielectric constant and dissipation factor are also affected by the incorporation of MnO 2. The possible mechanism for the influence of MnO 2 on the electromagnetic properties was discussed.

Magnetic properties of NiCuZn ferrites with addition of tungsten trioxide

The effect of WO 3 addition on the properties of NiCuZn ferrite, (Ni 0.2Cu 0.2Zn 0.6O) 1.02(Fe 2O 3) 0.98, has been investigated in this study. The enhanced electrical and magnetic properties obtained from WO 3 addition into NiCuZn ferrites were also shown in this study. Q-factor at 10 MHz of NiCuZn ferrites increased at higher electrical resistivity, but no significant change in initial permeability. The resonance frequency of those NiCuZn ferrites was shifted to a higher range, which means relaxation time was also decreased over 0.6 wt% of WO 3 content.

磁性材料 ＭｇＣｕＺｎフェライトの低温焼結化

In 1980, multilayer chip inductors were developed by thick film and co-firing technologies using low temperature sintered NiCuZn ferrites and Ag. The NiCuZn ferrites have been known as the only ones that can be sintered below the melting point of Ag, and have been used as the material of multilayer ferrite chip components. Since NiCuZn ferrites have a large magnetostriction, these ferrites are comparatively sensitive against stress, and therefore magnetic properties are easily deteriorated or changed by the stress. In this study, therefore, MgCuZn ferrites are chosen as a useful material for the multilayer ferrite chip components, because the magnetostriction (λ ?? ) of these ferrites is normally less than that of NiCuZn ferrites. MgCuZn ferrites, however, is generally sintered over 1000°C, so the investigations to sinter MgCuZn ferrites at the low temperature were performed.

磁性材料 低温焼結ＭｇＣｕＺｎフェライトの電磁気特性

It was reported that electromagnetic properties of the multilayer chip ferrite components are influenced by the internal stresses and the diffusion of Ag buried in ferrite. As the magnetostriction of MgCuZn ferrites is lower than that of NiCuZn ferrites, it was expected that the multilayer chip inductor using MgCuZn ferrite would obtain higher magnetic properties than that using NiCuZn ferrite. Therefore MgCuZn ferrites with the low sintering temperature have been developed as the materials for the multilayer chip ferrite components. Under a compressive stress, the change in permeability of low temperature sintering MgCuZn ferrite was lower than that of low temperature sintering NiCuZn ferrite. Moreover, one might expected that the multilayer chip inductor using low temperature sintering MgCuZn ferrite would show a higher inductance than the chip using low temperature sintering NiCuZn ferrite. It is thought that low temperature sintering MgCuZn ferrite has the high potentialities of useful materials in the multilayer chip ferrite components, not only the multilayer chip inductors but also the multilayer LC and EMI chip filter components.

磁性材料 Ｍｎ添加によるＮｉＣｕＺｎフェライトの信頼性向上

Mn content dependence on the resistivity and on the reliability of NiCuZn ferrites were investigated to obtain highly reliable NiCuZn ferrites for multilayer chip components. The resistivity drastically increased by Mn addition and the obtained high resistivity was maintained even at high temperature. From the result of complex impedance analysis, it was found that the increase of resistivity might be controlled by the intra-grain resistivity. The result of high temperature life test indicated that Mn addition can be improved on the reliability of NiCuZn ferrites.

磁性材料 フェライトの応力特性に及ぼす組成と微細構造の影響

As is known, the magnetic properties of ferrites are liable to be influenced by external stress. In this paper we describe our study of the effects of chemical composition and microstructure on the stress sensitivity of initial permeability of NiMgCuZn ferrites. When the external stress is applied to the ferrites, the reducing of the initial permeability due to the deficiency of Fe2O3 is observed. Furthermore, a finely dispersed grain size in microcrystalline structure is highly effective in stabilizing of initial permeability. As the compressive stress is applied parallel to the magnetic field, the maximum initial permeability of NiCuZn ferrite can be observed at 4 MPa. On the other hand, that of MgCuZn ferrite is observed at around 0 MPa. It seems possible to stabilize the initial permeability against the external stress by a further increase in composition ratio of NiO/(NiO + MgO).