NiZn-based ferrite, magnetic core using the same, and noise filter

Abstract

To provide NiZn-based ferrite that is excellent in productivity and can restrain the increment of a change rate of complex relative permeability relative to temperature, and a noise filter using the same.SOLUTION: The present invention relates to NiZn-based ferrite that contains Fe of 47.50 mol% or more and 48.60 mol% or less in terms of Fe2O3, Zn of 29.00 mol% or more and 30.10 mol% or less in terms of ZnO, Cu of 5.50 mol% or more and 6.50 mol% or less in terms of CuO, and Ni of 16.51 mol% or more and 18.00 mol% or less in terms of NiO, but does not contain Ti, and when setting the total amount of Fe2O3, ZnO, NiO and CuO to 100 mol%, the total amount of the Fe2O3 and the ZnO is 77.00 mol% or more and 78.50 mol% or less.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This invention relates to NiZn-based ferrite, a magnetic core using the same, and a noise filter. [Background technology]

[0002] In recent years, automobiles have adopted vehicle control systems that use an in-vehicle LAN (Local Area Network) to perform differential data transmission between multiple electronic control units. Various electronic components are used in vehicle control systems, but noise filters are used in the signal path to prevent noise leakage during data communication and to suppress the superposition of external noise on the signal path, thereby preventing malfunctions of in-vehicle equipment. Common mode choke coils are used as noise filters, which consist of a ferrite core (hereinafter referred to as the magnetic core) around which a conductor is wound. There are various configurations for common mode choke coils, but for example, there is a common mode choke coil that uses a drum-shaped core and a plate-shaped core covering it as the magnetic core, as described in Patent Document 1.

[0003] In noise filters, the impedance Z, which is the product of the complex relative permeability μ and frequency of the soft ferrite that makes up the magnetic core, is used to remove noise.

[0004] It is generally known that the complex relative permeability μ of soft ferrite has a snake limit, where the real part μ' decreases as the frequency increases due to losses from magnetic resonance. The higher the complex relative permeability μ of the soft ferrite, the lower the real part μ' begins to decrease from relatively low frequencies. As the real part μ' decreases, the imaginary part μ'' increases, peaks, and then decreases. Such a complex relative permeability μ is expressed by Equation 1, and in accordance with the changes in its real part μ' and imaginary part μ'', the impedance Z increases exponentially as the frequency increases and decreases as the real part μ' and imaginary part μ'' decrease.

[0005]

number

[0006] For example, CAN (Controller Area Network) is a well-known standard for differential transmission data communication, widely used in automotive LANs. Since harmonics of the signal frequency (250kHz or 500kHz in CAN) can become radiated noise up to several tens of MHz, noise filters used in the signal path are required to have high impedance in the high-frequency band of 10MHz or higher to attenuate common-mode noise.

[0007] Furthermore, noise filters are used in high-temperature environments such as the engine compartment of automobiles. Therefore, to enable use in a wide temperature range, for example, from -40°C to +150°C, the magnetic transition temperature (Curie temperature Tc) of the soft ferrite must be at least above 150°C, exceeding the operating temperature, and the temperature dependence of the complex relative permeability μ must be small.

[0008] In response to these requirements, Patent Document 2 discloses a soft ferrite for noise filters containing Fe, Zn, Ni, Cu, and Ti, in which a compound containing Ti is dispersed at the grain boundaries of an Fe-Zn-Ni-Cu crystal. It is stated that the Curie temperature is 160°C or higher, the temperature change rate of magnetic permeability can be kept to between -40% and 40%, and it can be made into an excellent noise filter with stable noise rejection performance over a wide temperature range from low to high temperatures. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2012-89804 [Patent Document 2] Japanese Patent Publication No. 2011-246343 [Overview of the project] [Problems that the invention aims to solve]

[0010] Patent Document 2 describes that in order to create a grain boundary structure in which a Ti-containing compound is dispersed at the grain boundaries, it is necessary to add TiO2 to calcined Fe2O3, ZnO, NiO, and CuO powders, grind them, mold the resulting pulverized powder, and then fire it at a predetermined temperature. Because the addition of TiO2 is required, an increase in production man-hours, equipment used, and types of raw materials is expected in the production of soft ferrite. Therefore, this may hinder the provision of magnetic cores at a low cost. Furthermore, according to Table 2 of Patent Document 2, as the amount of TiO2 increases, the Curie temperature Tc decreases, and the temperature change rate of magnetic permeability on the high-temperature side tends to increase, indicating that there is room for further improvement.

[0011] Therefore, the present invention aims to provide a NiZn-based ferrite that has a high Curie temperature, can suppress the rate of change of complex relative permeability with respect to temperature, and is highly productive, as well as a magnetic core and a noise filter using the same. [Means for solving the problem]

[0012] The first invention is a NiZn-based ferrite consisting of Fe in an amount of 47.50 mol% to 48.60 mol% in Fe2O3 terms, Zn in an amount of 29.00 mol% to 30.10 mol% in ZnO terms, Cu in an amount of 5.50 mol% to 6.50 mol% in CuO terms, and Ni in an amount of 15.00 mol% to 17.00 mol% in NiO terms, wherein the total amount of Fe2O3, ZnO, NiO, and CuO is 100 mol%, and the total amount of Fe2O3 and ZnO is 77.00 mol% to 78.50 mol%.

[0013] In the NiZn-based ferrite of the present invention, it is preferable that the Fe content is 47.50 mol% or more and 48.50 mol% or less in terms of Fe2O3, and the Zn content is 29.25 mol% or more and 29.90 mol% or less in terms of ZnO.

[0014] The NiZn-based ferrite of the present invention has a Curie temperature Tc of 160°C or higher and a complex relative permeability μ 25 It is preferable that the complex relative permeability μ is between 800 and 1200. 25is the complex relative permeability μ at a frequency of 100 kHz and a temperature of 25°C.

[0015] Moreover, the NiZn ferrite of the present invention preferably has a temperature Tμ at which the complex relative permeability μ is maximum between 50°C and 130°C. max

[0016] Moreover, the NiZn ferrite of the present invention 25 for the complex relative permeability μ max of the change rate Δμ max is preferably 40% or less. However, the complex relative permeability μ max is the highest complex relative permeability μ under the condition of a frequency of 100 kHz at temperatures from -40°C to 150°C. Moreover, the change rate Δμ max =(μ max -μ 25 ) / μ 25 × 100 (%).

[0017] Moreover, when the total amounts of Fe, Zn, Ni, and Cu in the NiZn ferrite of the present invention are each 100 parts by mass in terms of Fe2O3, ZnO, NiO, and CuO, it is preferable that Mn is 0.500 parts by mass or less in terms of Mn3O4, Ca is 0.025 parts by mass or less in terms of CaO, and Si is 0.250 parts by mass or less in terms of SiO2.

[0018] Another form of the present invention is a magnetic core using the NiZn ferrite.

[0019] Another form of the present invention is a noise filter using the magnetic core.

[0020] Moreover, the noise filter of the present invention preferably includes a columnar shaft portion, a first magnetic core having flange portions at both ends of the shaft portion, a plate-like second magnetic core passed between the flange portions of the first magnetic core, and a first conductor and a second conductor wound around the shaft portion of the first magnetic core.

Advantages of the Invention

[0021] ​According to the present invention, it is possible to provide a NiZn-based ferrite that has a high Curie temperature and can suppress the rate of change of complex relative permeability with respect to temperature, while also being highly productive, as well as a magnetic core and a noise filter using the same. [Brief explanation of the drawing]

[0022] [Figure 1] This figure shows the relationship between the total amount of Fe2O3 and ZnO and the complex relative permeability μ25 in one embodiment of the NiZn-based ferrite of the present invention. [Figure 2] This figure shows the relationship between the amount of ZnO and the Curie temperature Tc in one embodiment of the NiZn-based ferrite of the present invention. [Figure 3] This figure shows the relationship between the amount of Fe2O3 and the rate of change Δμmax in one embodiment of the NiZn-based ferrite of the present invention. [Figure 4] This figure shows the relationship between the amount of Fe2O3 and the rate of change Δμmin in one embodiment of the NiZn-based ferrite of the present invention. [Figure 5] This figure shows the relationship between frequency and normalized impedance ZN in one embodiment of the NiZn-based ferrite of the present invention. [Figure 6] This figure shows the relationship between frequency and normalized impedance ZN in the comparative example NiZn-based ferrite. [Figure 7] This is an equivalent circuit diagram showing an example of an electronic component using the NiZn-based ferrite of the present invention. [Figure 8] This is a perspective view showing a structure in which a coil and terminals are provided on a magnetic core using the NiZn-based ferrite of the present invention. [Figure 9] Figure 8 is a perspective view showing the external structure of the electronic component. [Figure 10] This figure shows the relationship between the crushed particle size of the calcined powder and the complex relative permeability μ25 in one embodiment of the NiZn-based ferrite of the present invention. [Figure 11] This figure shows the relationship between the crushed particle size of the calcined powder and the rate of change of the complex relative permeability Δμmax and Δμmin in one embodiment of the NiZn-based ferrite of the present invention. [Figure 12] This figure shows the relationship between the firing temperature and the rate of change of complex relative permeability Δμmax and Δμmin in one embodiment of the NiZn-based ferrite of the present invention. [Modes for carrying out the invention]

[0023] The following describes in detail a NiZn-based ferrite, a magnetic core using the same, and a noise filter according to one embodiment of the present invention. Unless otherwise specified, a description of one embodiment applies to other embodiments. Furthermore, the following description is not limiting, and various modifications and additions may be made within the scope of the technical idea of ​​the present invention, and can be modified as appropriate.

[0024] Figure 9 is a perspective view of the noise filter, and the NiZn-based ferrite of the present invention is used, for example, in its magnetic core. The noise filter 10 includes a drum-shaped core (first magnetic core) 21, a plate-shaped core (second magnetic core) 22, and windings 30 and terminals 31 and 32 provided on the first magnetic core 21. The second magnetic core 22 is positioned to cover the first magnetic core 21, and the two are bonded and fixed to each other, forming a closed magnetic circuit structure.

[0025] Figure 8 is a perspective view of the noise filter 10 in Figure 9, excluding the second magnetic core 22. The first magnetic core 21 has a shaft (not shown) and a first flange 25 and a second flange 26 at its ends. Two conductors are wound spirally on the shaft of the first magnetic core 21 using a bifilar winding method, forming the first conductor 30a and the second conductor 30b. Two terminals 31 and 32 are formed on the first flange 25 of the first magnetic core 21. Only terminal 33 is visible on the second flange 26, but it has two terminals similar to those on the first flange 25, with each flange having two terminals. One end of the first conductor 30a is connected to the first terminal 31, and the other end is connected to a second terminal (not shown). One end of the second conductor 30b is connected to a third terminal 32, and the other end is connected to a fourth terminal 33.

[0026] Figure 7 is an equivalent circuit diagram of the noise filter (common mode choke coil) shown in Figure 9. In the figure, terminal T1 corresponds to the first terminal 31 in the noise filter of Figure 9. Terminal T2 corresponds to the second terminal, which is not shown. Terminal T3 corresponds to the third terminal 32, and terminal T4 corresponds to the fourth terminal 33.

[0027] (Composition of NiZn-based ferrite) NiZn ferrite used in magnetic cores consists of 47.50 mol% to 48.60 mol% Fe (based on Fe2O3), 29.00 mol% to 30.10 mol% Zn (based on ZnO), 5.50 mol% to 6.50 mol% Cu (based on CuO), and 14.80 mol% to 18.00 mol% Ni (based on NiO). The total amount of Fe2O3, ZnO, NiO, and CuO is 100 mol%, and the total amount of Fe2O3 and ZnO is 77.00 mol% to 78.50 mol%. In addition, unavoidable impurity elements from the raw materials may be present.

[0028] The amount of Fe is preferably between 47.50 mol% and 48.60 mol% in terms of Fe2O3. The rate of change Δμ of the complex relative permeability μ, which will be described later, increases with the amount of Fe2O3. min or rate of change Δμ max When the absolute value of increases and exceeds 48.60 mol%, the desired rate of change Δμ min Δμ max In some cases, the desired rate of change Δμ may not be obtained. min Δμ max This refers to the rate of change Δμ min Δμ max The absolute values ​​of each are 40% or less. Also, if it is less than 47.50 mol%, the complex relative permeability μ at a temperature of 25°C is less. 25 The desired complex relative permeability μ decreases. 25 The desired complex relative permeability μ may not be obtained. 25 The value is between 800 and 1200. It is even more preferable that the Fe2O3 content be 48.50 mol% or less. It is even more preferable that it be 47.80 mol% or more, and even more preferable that it be 48.00 mol% or more.

[0029] Preferably, the amount of Zn is between 29.00 mol% and 30.10 mol% in terms of ZnO. If the amount of ZnO is less than 29.00 mol%, the desired complex relative permeability μ 25 In some cases, this may not be obtained. At concentrations exceeding 30.10 mol%, a Curie temperature Tc of 160°C or higher may not be obtained. Rate of change Δμ max To reduce the amount, it is preferable to have a concentration of 29.25 mol% or more, and preferably 29.90 mol% or less.

[0030] Furthermore, the Fe2O3 and ZnO content is preferably between 77.00 mol% and 78.50 mol%. Setting it to 77.00 mol% or higher increases the complex relative permeability μ 25 It can be 800 or more. More preferably it is 77.30 mol% or more. It is also preferable that it be 78.40 mol% or less.

[0031] Preferably, the amount of Cu is between 5.50 mol% and 6.50 mol% in terms of CuO. If the amount of CuO is less than 5.50 mol% or greater than 6.50 mol%, the desired complex relative permeability μ 25 This may not always be achieved. The preferred CuO content is 5.70 mol% or more, and preferably 6.30 mol% or less.

[0032] Furthermore, the amount of Ni is preferably between 14.80 mol% and 18.00 mol% in terms of NiO. The amount of NiO is the remainder obtained by subtracting the total amount of the above components Fe2O3, ZnO, and CuO from the total of 100 mol% of Fe2O3, ZnO, NiO, and CuO.

[0033] Examples of impurity elements include Si, Ca, B, C, S, Cl, Se, Br, P, Te, I, Li, Na, Mg, Al, K, Ga, Ge, Sr, In, Sn, Sb, Ba, Bi, Sc, Ti, Mn, V, Cr, Y, Nb, Mo, Pd, Ag, Hf, Ta, Zr, Co, Pb, etc. In this invention, with the exception of Mn, Ca, and Si, all are defined as the Curie temperature Tc or the rate of change of complex relative permeability Δμ with respect to temperature for NiZn-based ferrites. min Δμ maxIt may be included to the extent that it does not affect the performance, i.e., within the range where the desired performance can be obtained.

[0034] Among the impurity elements contained in the raw materials, it is preferable that the amount of Mn, which is abundant in the raw material Fe2O3, be limited to several thousand ppm in terms of oxide, while the other impurity elements are limited to several ppm to several hundred ppm in terms of oxide. In NiZn-based ferrite, for every 100 parts by mass of Fe2O3, ZnO, NiO, and CuO, the amount of Mn is preferably 0.500 parts by mass or less in terms of Mn3O4, and more preferably 0.3 parts by mass or less. Ca is preferably 0.025 parts by mass or less in terms of CaO, and Si is preferably 0.250 parts by mass or less in terms of SiO2. Among the unavoidable impurities, Na, S, Cl, P, Cr, and B should be kept as small as possible to avoid abnormal sintering resulting in insufficient sintering or coarse crystals, preferably totaling 0.1 parts by mass or less, and more preferably 0.05 parts by mass or less. Furthermore, it is preferable that all other unavoidable impurities be 0.005 parts by mass or less. It is preferable that the total amount of Mn, Ca, and Si in terms of oxides is 0.600 parts by mass or less per 100 parts by mass of the total amount of Fe2O3, ZnO, NiO, and CuO.

[0035] The components of Fe2O3, ZnO, NiO, and CuO can be quantified by X-ray fluorescence analysis and ICP emission spectrometry. Qualitative analysis of the constituent elements (Fe, Zn, Ni, Cu, Mn, Zr, Sn, P, S, Bi, Mg, Al, Si, Cl, K, Ca, Ti, V, Cr, Co, Pb, etc.) is performed beforehand by X-ray fluorescence analysis, and then quantification is performed using a calibration curve method comparing the constituent elements with a standard sample. Inevitable impurities can be quantified by methods such as combustion-infrared absorption spectrometry and atomic absorption spectrometry. Furthermore, excluding Mn, which is abundant in the raw materials for Fe2O3, and Ca and Si, which are abundant in nature and easily cause contamination, other elements are present in trace amounts. Therefore, it is acceptable to calculate the amount contained in NiZn-based ferrite based on the composition ratio, using the values ​​calculated according to the composition ratio of Fe2O3, ZnO, NiO, and CuO from the amounts listed on the inspection sheet for the raw materials of Fe2O3, ZnO, NiO, and CuO.

[0036] (Manufacturing method for NiZn-based ferrite) Compound (oxide) powders of the elements Fe, Zn, Ni, and Cu that constitute NiZn ferrite are used as raw materials. These are wet-mixed in predetermined proportions, then dried to obtain the raw material powder. The raw material powder is calcined at a temperature of 700°C or higher but lower than the sintering temperature to promote spinelization and obtain a calcined body.

[0037] As spinelization progresses, it takes more time to pulverize the calcined body; therefore, a calcination temperature lower than the sintering temperature is preferably at least 100°C lower than the sintering temperature. On the other hand, if the calcination temperature is less than 700°C, spinelization is too slow, and the time required for calcination becomes too long; therefore, a temperature of 700°C or higher is preferable. The calcination temperature is preferably 850°C or higher. If the composition of the calcined body differs from the desired composition, the composition may be adjusted by adding compounds of Fe, Zn, Ni, and Cu during the pulverization of the calcined body.

[0038] The calcined material is placed in a ball mill with deionized water and wet-ground to form a slurry. The calcined material is preferably ground until the average particle size of the ground powder (measured by air permeability method) is 1.2 μm or more and 2.5 μm or less, and more preferably until it is 1.5 μm or more and 2.0 μm or less. The grinding time is preferably 0.1 hours or more and 4.0 hours or less. If the grinding time is less than 0.1 hours, a desirable particle size may not be obtained, and if it exceeds 4.0 hours, there is a risk of increased contamination due to wear of the grinding media and containers of the grinder.

[0039] A binder such as polyvinyl alcohol is added to the slurry, granulated using a spray dryer, and then pressure-molded to obtain a molded body of a predetermined shape. The molded body is sintered in a firing furnace at a temperature of 1000°C to 1200°C to obtain a sintered body (magnetic core of NiZn ferrite). The firing process includes a heating step, a temperature holding step, and a cooling step. The atmosphere during the firing process may be an inert gas atmosphere or an atmospheric atmosphere. In the temperature holding step, where the temperature is between 1000°C and 1200°C, it is preferable to hold the temperature within a predetermined temperature range for a predetermined time.

[0040] When the average particle size of the calcined powder is small, the sintering reaction activity is high, and densification is easily promoted from low temperatures. On the other hand, if the set temperature of the firing furnace is high, sintering becomes excessive, resulting in a coarse crystalline structure, making it difficult to produce a sintered body with a uniform and dense crystalline particle size. By setting the average particle size of the crushed powder to 1.2 μm or more and the sintering temperature in the firing process to 1000°C to 1200°C, the complex relative permeability of the sintered body can be increased. 25 or the rate of change of the complex relative permeability μ, Δμ min Δμ max This is preferable because it provides stability.

[0041] The complex relative permeability μ, sintered body density ds, and average grain size d of the obtained sintered body can be measured by the following method. Furthermore, the rate of change Δμ can be obtained from the obtained complex relative permeability μ. max、 Δμ min From the real part μ' and imaginary part μ'' of the complex relative permeability μ, the impedance (normalized impedance Z) is calculated. N It is possible to calculate ).

[0042] (1) Complex relative permeability μ A coil component, in which a sintered body is used as the annular magnetic core and a wire is wound around it, is used as the evaluation sample. The inductance L at 100kHz and 1mA is measured using an LCR meter (Agilent Technologies, Inc. 4285A). m and resistor R m The inductance L obtained by measuring the above was measured. m and resistor R m From this, the complex relative permeability μ, its real part μ', and its imaginary part μ'' are calculated using equations 2 to 4.

[0043] (a) Real part μ' of the complex relative permeability μ

number

[0044] (b) Imaginary part μ of complex relative permeability μ”

number

[0045]

number

[0046] The annular magnetic core has a rectangular cross-section perpendicular to the magnetic path, with dimensions of inner diameter φ20mm, outer diameter φ30mm, and thickness 8mm. Ae is the effective cross-sectional area (m²) of the magnetic core. 2 ), le is the effective magnetic path length of the magnetic core (m), μ0 is the permeability of vacuum [4π × 10 -7 ](H / m), where N is the number of turns of the wire, f is the frequency (Hz), Lm is the measured inductance (H), and Rm is the measured resistance (Ω). An Enic wire with a diameter of φ0.5 mm was used as the conductor, and the number of turns N was set to 20 turns.

[0047] (2) Rate of change of complex relative permeability μ Δμ max Δμ min The evaluation sample used for measuring the complex relative permeability μ is connected to a measurement jig in a constant temperature bath. The measurement jig is connected to an LCR meter (4285A), and the temperature of the evaluation sample is varied between -40°C and 150°C, and the inductance L is measured at a frequency of 100 kHz. m and resistor R m The inductance L obtained under temperature T conditions is measured. m and resistor R m From equations 2 to 4, the complex relative permeability μ T The complex relative permeability μ was calculated. T μ is the complex relative permeability at temperature T, for example, complex relative permeability μ 25 This is the complex relative permeability μ at a temperature of 25°C. max This is the highest complex relative permeability μ at temperatures from -40°C to 150°C, and Tμ max μ is the complex relative permeability. max This is the temperature at which this occurs. Also, the complex relative permeability μ min This is the lowest complex relative permeability μ at temperatures from -40°C to 150°C, and Tμ min μ is the complex relative permeability. min This is the temperature at which the change rate Δμ is obtained using the complex relative permeability μ obtained from Equation 5. maxFrom Equation 6, the rate of change Δμ min Calculate.

[0048] The maximum rate of change Δμ on the positive side of the complex relative permeability μ. max This is the absolute value calculated using Equation 5.

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[0049] The maximum rate of change Δμ on the negative side of the complex relative permeability μ. min This is the absolute value calculated using Equation 6.

number

[0050] (3) Normalized impedance Z N Frequency characteristics Similar to the complex relative permeability μ mentioned above, the inductance L at a current of 1mA at frequencies from 80kHz to 30MHz was measured using an LCR meter (4285A). m and resistor R m The inductance L was measured at room temperature and obtained. m and resistor R m From this, the real part μ' and imaginary part μ'' of the complex relative permeability μ are calculated using equations 2 and 3. Using the obtained real part μ' and imaginary part μ'', the normalized impedance Z is calculated using equation 7. N The following was calculated. The measurement was performed using the Agilent Technologies, Inc. test fixture 16085B.

[0051]

number

[0052] (4) Curie temperature Tc The Curie temperature Tc was determined using a similar sample and an LCR meter according to JIS C2560.

[0053] (5) Sintered body density ds The density of the NiZn-based ferrite sintered body was calculated using the volumetric gravitational method based on its dimensions and weight. The density of the sintered body was 5.10 × 10⁻⁶. 3 kg / m 3 A threshold was set, and anything exceeding this threshold was judged as "good." A low sintered body density suggests insufficient sintering, resulting in inferior mechanical strength and a higher likelihood of chipping and cracking.

[0054] (6) Average grain size A sintered NiZn ferrite body was thermally etched at a temperature lower than the firing temperature, and a scanning electron microscope (SEM) image (3000x magnification) of its surface was taken. The observation area of ​​the SEM image at 3000x magnification was 33 μm × 43 μm. Three arbitrary straight lines of length L1 were drawn on the SEM image, and the number of crystal grains N1 present on each line was counted. For each line, the value L1 / N1 was calculated by dividing the length L1 by the number of grains N1, and the average crystal grain size was obtained by dividing the sum of L1 / N1 values ​​by 3. Note that thermal etching should be performed at a temperature at which crystal grain boundaries can be confirmed, and it is typically preferable to perform it at a temperature about 50°C to 100°C lower than the firing temperature. If the firing temperature of the NiZn ferrite sintered body is unknown, thermal etching should be started at a low temperature and the temperature should be gradually increased until crystal grain boundaries can be confirmed. [Examples]

[0055] Examples 1-21 and Comparative Examples 1-9 The raw materials—Fe2O3 powder, ZnO powder, CuO powder, and NiO powder—weighed to obtain NiZn-based ferrite with the composition shown in Table 1 were wet-mixed, dried, and calcined at 900°C for 1 hour. Each calcined body was placed in a ball mill with deionized water and pulverized to form a slurry. A portion of the obtained slurry was dried and the average particle size was evaluated by air permeation. The average particle size was in the range of 1.5 μm to 1.7 μm in all cases. Polyvinyl alcohol was added as a binder to the remaining slurry, and it was dried and granulated using a spray dryer, and then pressure-molded to obtain annular molded bodies. The raw materials used in the NiZn-based ferrite were selected so that, when the total amount of Fe2O3, ZnO, CuO, and NiO is 100 parts by mass, the amounts of Mn, Si, and Ca, including other impurity elements, are 0.250 parts by mass or less in terms of oxides.

[0056] Each molded body was sintered at a temperature of 1100°C for 2 hours to obtain annular NiZn-based ferrite sintered bodies with an outer diameter of 30 mm, an inner diameter of 20 mm, and a thickness of 8 mm. The firing atmosphere was air.

[0057] The density ds, complex relative permeability μ, real part μ' of complex relative permeability μ, imaginary part μ' of complex relative permeability μ, average grain size, Curie temperature Tc, rate of change of complex relative permeability μ Δμmin, Δμmax, and normalized impedance Z for each NiZn-based ferrite sintered body. N The values ​​were measured or calculated using the method described above. The results, including those obtained, are shown in Table 1 and Figures 1 to 6. In Table 1, the rate of change of the complex relative permeability μ is Δμ. -40 Δμ 100 Δμ 150 μ 25 Complex relative permeability μ based on T This is the rate of change at (T = -40℃, 100℃, 150℃). μ 25 μ T When the change rate Δμ is small and negative, it is indicated with a minus sign. In Figures 1 to 4, the examples are shown with white circles, and the comparative examples are shown with X marks and black squares, with the black squares also indicating that the Curie temperature Tc is less than 160°C.

[0058] [Table 1]

[0059] In both the examples and comparative examples, all NiZn-based ferrite sintered bodies had a density ds of 5.15 × 10⁻⁶. 3 kg / m 3 The results were excellent, exceeding the specified limits. Furthermore, the average crystal grain size was within the range of 5 μm to 20 μm.

[0060] Figure 2 shows the relationship between the amount of ZnO in NiZn-based ferrite and the Curie temperature Tc. As the amount of ZnO increases, the Curie temperature Tc decreases, and in Comparative Examples 5 through 8, where the amount of ZnO exceeded 30.10 mol%, the Curie temperature Tc fell below 160°C.

[0061] Figures 3 and 4 show the relationship between the amount of Fe2O3 and the rate of change Δμmax and Δμmin of the complex relative permeability μ. max The amount of Fe2O3 increased sharply when it exceeded 48.60 mol%. Also, the rate of change Δμ min The ratio of the permeability to the magnetic field showed a tendency to increase gradually with respect to the amount of Fe2O3. Furthermore, in Comparative Examples 5 to 8, where the Curie temperature Tc was less than 160°C, the complex relative permeability μ min The temperature at which this occurs is 150°C, compared to -40°C for other evaluation samples, and the rate of change Δμ min It increased significantly.

[0062] Figure 1 shows the relationship between the total amount of Fe2O3 and ZnO in NiZn-based ferrite and the complex relative permeability μ. As the total amount of Fe2O3 and ZnO increased, the complex relative permeability μ also increased.

[0063] Figures 5 and 6 show the normalized impedance Z of the evaluation samples. N The frequency characteristics are shown. Figure 5 shows μ 25 The evaluation sample from Example 21 was 940, and Figure 6 shows μ 25Using the evaluation sample of Comparative Example 8 with a value of 1480, the results at temperatures of -40°C, 25°C, 60°C, and 100°C are shown. Note that the upper limit of the measurement temperature is not 150°C, but is set to 100°C due to the heat resistance specification of the test lead (measurement cable) prepared for the measurement. Also shown in Table 2 are μ' and μ" at temperatures of -40°C, 25°C, 60°C, and 100°C, which are the basis for the calculation of the normalized impedance Z N . N Note that Z N is the value obtained by rounding the first digit of the value calculated by Equation 7.

[0064]

Table 2

[0065] In Example 21, compared with Comparative Example 8, the frequency at which μ" peaks is higher, and the normalized impedance Z N has less variation with temperature. Also in Comparative Example 8, at a temperature of 100°C and a frequency of 30 MHz, μ' is almost 0, and μ" and Z N are lower than those in Example 21, and a further decrease in Z N is expected at a temperature of 150°C. From these results, it is suggested that Comparative Example 8 with μ 25 exceeding 1200 is not suitable for use as a noise filter at high temperatures.

[0066] Examples 22 to 28 and Reference Examples 1 to 3 Fe2O3 powder, ZnO powder, CuO powder, and NiO powder were weighed to obtain NiZn-based ferrite with the composition shown in Example 21 of Table 1. These were wet-mixed, dried, and calcined at 900°C for 2 hours. The resulting calcined material was placed in an attritor with deionized water and pulverized for 1 minute to 8 hours, as shown in Table 3, to obtain a slurry. A portion of the obtained slurry was dried and the average particle size was evaluated by air permeation. The average particle size was in the range of 0.80 μm to 1.85 μm. If there was a deviation in composition as determined by X-ray fluorescence analysis, raw materials were added to adjust the composition to match that of Example 21. Polyvinyl alcohol was added as a binder to the remaining slurry, and it was dried and granulated using a spray dryer. Annular molded bodies were obtained by pressure molding.

[0067] Each molded body was sintered at a temperature of 1100°C for 2 hours to obtain annular NiZn-based ferrite sintered bodies with an outer diameter of 30 mm, an inner diameter of 20 mm, and a thickness of 8 mm. The firing atmosphere was air.

[0068] The density ds, complex relative permeability μ, the real part μ' of the complex relative permeability μ, the imaginary part μ'' of the complex relative permeability μ, and the rate of change Δμ of the complex relative permeability μ were measured or calculated for each NiZn-based ferrite sintered body using the method described above. The obtained results are shown in Table 3, Figure 7, and Figure 8. Figure 7 shows the relationship between the crushed particle size and the complex relative permeability μ, and Figure 8 shows the relationship between the crushed particle size and the rate of change Δμ of the complex relative permeability μ. min Δμ max This is a diagram showing the relationship between the two.

[0069] [Table 3]

[0070] As shown in Figure 10, the complex relative permeability μ stabilizes when the particle size of the calcined material exceeds 1.20 μm. Also, as shown in Figure 11, the rate of change Δμ of the complex relative permeability μ stabilizes when the particle size of the calcined material exceeds 1.20 μm. min Δμ max The result was stable. On the other hand, when the crushed particle size was 1.20 μm or less, the complex relative permeability μ decreased, and the rate of change of the complex relative permeability μ Δμ min Δμmax increased.

[0071] Examples 29 to 31 and Comparative Examples 4 to 6 Fe2O3 powder, ZnO powder, CuO powder, and NiO powder were weighed so as to obtain a NiZn ferrite having the composition shown in Example 21 of Table 1, wet-mixed, dried, and calcined at a temperature of 900 °C for 2 hours. The obtained calcined product was put into an attritor together with ion-exchanged water and pulverized for 0.5 hours to obtain a slurry. Polyvinyl alcohol was added to the obtained slurry as a binder, dried and granulated by a spray dryer, and pressure-molded to obtain an annular molded body.

[0072] Each molded body was sintered at a firing furnace set temperature of 1080 °C to 1160 °C for a holding time of 2 hours to obtain each NiZn ferrite sintered body having an outer diameter of 30 mm, an inner diameter of 20 mm, and a thickness of 8 mm. The firing atmosphere was air.

[0073] The complex relative permeability μ and the change rate Δμ of the complex relative permeability μ of each NiZn ferrite sintered body were measured or calculated by the above method. Table 4 and FIG. 12 show the obtained results. FIG. 12 shows the relationship between the firing temperature and the change rate Δμ of the complex relative permeability μ min , Δμ max and Δμ. It is a diagram showing the relationship. The firing temperatures shown in Table 4 and FIG. 12 are not the set temperatures of the firing furnace, but the indicated values of a thermal history sensor (manufactured by the Fine Ceramics Center, Refathermo).

[0074]

Table 4

[0075] As is clear from Table 4 and FIG. 12, the complex relative permeability μ tends to increase with respect to the firing temperature, and the change rate Δμ of the complex relative permeability μ max , Δμ min also tends to increase. The complex relative permeability μ and the change rate Δμ of the complex relative permeability μ max , Δμ minBy selecting a small particle size that increases sinterability within a range where the performance does not decrease, and sintering at a low temperature, further improvement in the properties of NiZn-based ferrite can be expected.

[0076] Examples 32-42 and Comparative Examples 10-13 Using Fe2O3 powder, ZnO powder, CuO powder, NiO powder, Mn3O4 powder, CaCO3 powder, and SiO2 powder, which were weighed to obtain NiZn-based ferrites with the compositions shown in Table 5, Fe2O3 powder, ZnO powder, CuO powder, and NiO powder were wet-mixed, dried, and calcined at 900°C for 1 hour. Each of the resulting calcined bodies was placed in a ball mill along with Mn3O4 powder, CaCO3 powder, SiO2 powder, and deionized water, and pulverized with an attritor to obtain a slurry. A portion of the obtained slurry was dried, and the average particle size was evaluated by air permeation. The average particle size was in the range of 1.7 μm to 1.9 μm in all cases. Polyvinyl alcohol was added as a binder to the remaining slurry, and it was dried and granulated using a spray dryer, and then pressure-molded to obtain annular molded bodies.

[0077] Each molded body was sintered at a temperature of 1100°C for 2 hours to obtain annular NiZn-based ferrite sintered bodies with an outer diameter of 30 mm, an inner diameter of 20 mm, and a thickness of 8 mm. The firing atmosphere was air.

[0078] Density ds, complex relative permeability μ, Curie temperature Tc, and rate of change Δμ of complex relative permeability μ for each NiZn-based ferrite sintered body. min Δμ max The values ​​were measured or calculated using the method described above. The results are shown in Table 6. In Table 6, Fe, Zn, Ni, and Cu are shown as the main components, while Mn3O4, CaO, and SiO2 are shown as minor components.

[0079] [Table 5]

[0080] [Table 6]

[0081] In both the examples and comparative examples, all NiZn-based ferrite sintered bodies had a density ds of 5.15 × 10⁻⁶. 3 kg / m 3 The results were excellent, exceeding the specified limits. Furthermore, the average crystal grain size was within the range of 5 μm to 20 μm.

[0082] In Comparative Examples 10 and 11, where the amount of Mn3O4 increased to over 0.500 parts by mass, the complex relative permeability μ decreased on the low-temperature side and increased on the high-temperature side, resulting in the desired rate of change Δμ of the complex relative permeability μ. min Δμ max (A value of 40% or less in absolute terms) was not obtained. The rate of change of the complex relative permeability μ Δμ increases as the amount of CaO increases. min Δμ max Although the amount of SiO2 decreases, in comparative examples 12 and 13, where the amount exceeds 0.250 parts by mass, the complex relative permeability μ decreases and the complex relative permeability μ falls below 800. Also, as the amount of SiO2 increases, the complex relative permeability μ increases, but the rate of change Δμ of the complex relative permeability μ is... min Δμ max It also increased.

[0083] As explained above, by using a NiZn-based ferrite consisting of Fe in the form of 47.50 mol% to 48.60 mol% (equivalent to Fe2O3), Zn in the form of 29.00 mol% to 30.10 mol% (equivalent to ZnO), Cu in the form of 5.50 mol% to 6.50 mol% (equivalent to CuO), and Ni in the form of 14.80 mol% to 18.00 mol% (equivalent to NiO), with a total amount of Fe2O3, ZnO, NiO, and CuO of 100 mol%, and a total amount of Fe2O3 and ZnO of 77.00 mol% to 78.50 mol%, the Curie temperature Tc is high, and the rate of change of the complex relative permeability μ with respect to temperature Δμ min Δμ max This allows for the creation of NiZn-based ferrites with small particle size. Furthermore, because a complex microstructure is not required, productivity is excellent. In addition, noise filters using this material can reduce impedance fluctuations due to temperature changes, resulting in good temperature characteristics. [Explanation of Symbols]

[0084] 10 Electronic Components 21 First magnetic core 22 Second magnetic core 30 windings (conductors) Terminals 31, 32, 33

Claims

1. Fe ２ O ３ In terms of conversion, Fe is "47.50 mol% or more and 48.60 mol% or less", Zn with a concentration of "29.00 mol% or more and 30.10 mol% or less" in terms of ZnO, Cu in CuO equivalent of "5.50 mol% or more and 6.50 mol% or less", Ni with a concentration of "16.51 mol% or more and 18.00 mol% or less" in NiO equivalent. It contains as its main component, and, Fe ２ O ３ When the total amount of ZnO, NiO, and CuO is set to 100 mol%, The Fe ２ O ３ And the total amount of ZnO is "77.00 mol% or more and 78.50 mol% or less", The total amounts of Fe, Zn, Ni, and Cu are expressed in terms of Fe₂O₃, ZnO, NiO, and CuO, respectively. When the mass is 100 parts, Mn in the form of Mn3O4, which is "0.500 parts by mass or less", Ca in terms of CaO equivalent of "0.025 parts by mass or less", Si in terms of SiO₂, "0.250 parts by mass or less", It is added as a minor component, The Curie temperature Tc is 160°C or higher. NiZn-based ferrite.

2. NiZn-based ferrite according to claim 1, The aforementioned Fe is Fe ２ O ３ In terms of conversion, this is "47.50 mol% or more and 48.50 mol% or less". The aforementioned Zn is "29.25 mol% or more and 29.90 mol% or less" in terms of ZnO equivalent. NiZn-based ferrite.

3. NiZn-based ferrite according to claim 1 or 2, Complex relative permeability μ ２５ is the complex relative permeability μ under the conditions of "frequency 100 kHz, temperature 25°C", and is 800 or more and 1200 or less. NiZn-based ferrite.

4. NiZn-based ferrite according to claim 3, The complex relative permeability μ is the temperature Tμ at which it is maximum between 50°C and 130°C. ｍａｘ There is, NiZn-based ferrite.

5. NiZn-based ferrite according to claim 4, Complex relative permeability μ ｍａｘ This is the highest complex relative permeability μ among the complex relative permeability μs under the conditions of "frequency 100 kHz, -40°C to 150°C". The complex relative permeability μ ２５ The complex relative permeability μ for the above ｍａｘ Rate of change Δμ ｍａｘ It is less than 40%, and "Δμ ｍａｘ = (μ ｍａｘ -μ ２５ ) / μ ２５ It is "x 100 (%)" NiZn-based ferrite.

6. A magnetic core using NiZn-based ferrite according to any one of claims 1 to 5.

7. A noise filter using a magnetic core as described in claim 6.

8. A noise filter according to claim 7, The aforementioned magnetic core comprises a columnar shaft portion and a first magnetic core having flange portions at both ends of the shaft portion, The device comprises a plate-shaped second magnetic core that spans between the flanges of the first magnetic core, A noise filter comprising a first conductor and a second conductor wound around the shaft of the first magnetic core.

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