NiZn-BASED FERRITE, AND MAGNETIC CORE USED WITH 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] The present invention relates to a NiZn-based ferrite, a magnetic core using the same, and a noise filter.

Background Art

[0002] In recent years, in automobiles, a vehicle control system using an in-vehicle LAN (Local Area Network) that performs data communication by differential transmission between a plurality of electronic control units has been adopted. Although various electronic components are used in the vehicle control system, a noise filter is used in the signal path to prevent leakage of noise in data communication, suppress external noise from overlapping the signal path, and prevent malfunction of in-vehicle devices. As the noise filter, a common-mode choke coil in which a conductor is wound around a ferrite core (hereinafter referred to as a magnetic core) is used. Although the configuration of the common-mode choke coil varies, for example, there is a common-mode choke coil that uses a drum-shaped core and a plate-shaped core covering the drum-shaped core as the magnetic core as described in Patent Document 1.

[0003] In the noise filter, impedance Z represented by the product of the complex relative permeability μ of the soft ferrite constituting the magnetic core and the frequency is used for noise removal.

[0004] Generally, it is known that the complex relative permeability μ of soft ferrite has a Snoek's limit in which the real part μ' decreases as the frequency increases due to losses caused by magnetic resonance. The higher the complex relative permeability μ of the soft ferrite, the earlier the real part μ' begins to decrease from a relatively low frequency. As the real part μ' decreases, the imaginary part μ” increases, shows a peak, and then decreases. Such a complex relative permeability μ is represented by Equation 1, and according to the changes in the real part μ' and the imaginary part μ”, the impedance Z exponentially increases as the frequency increases, and shows a behavior of decreasing as the real part μ' and the imaginary part μ” decrease.

[0005]

Equation

[0006] For example, CAN (Controller Area Network) is known as a standard for differential transmission-based data communication that is widely used as an in-vehicle LAN. Since the harmonics of the signal frequency (250 kHz or 500 kHz in CAN) may become radiated noise up to the tens of MHz band, the noise filter used in the signal path is required to have a large impedance in the high-frequency band of 10 MHz or higher so as to attenuate the common-mode noise.

[0007] Also, the noise filter is used even in the engine room of an automobile where the temperature is high. Therefore, for example, so that it can be used in a wide temperature range of -40°C to +150°C, the magnetic transition temperature (Curie temperature Tc) of the soft ferrite is a temperature exceeding at least 150°C, which is higher than the temperature at which it is used, and it is required that the temperature dependence of the complex relative permeability μ is small.

[0008] In response to such requirements, Patent Document 2 discloses a soft ferrite for a noise filter containing Fe, Zn, Ni, Cu, Ti and having a compound containing Ti dispersed at the grain boundaries of the Fe-Zn-Ni-Cu crystal. It is described that the Curie temperature is 160°C or higher, the temperature change rate of the magnetic permeability can be suppressed to -40% or more and 40% or less, and it can be made into an excellent noise filter having stable noise removal performance in a wide temperature range from the low temperature range to the high temperature range.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0010] In Patent Document 2, in order to obtain a grain boundary structure in which a compound containing Ti is dispersed at grain boundaries, it is necessary to add TiO2 to the calcined powders of Fe2O3, ZnO, NiO, and CuO powders, pulverize them, mold the obtained pulverized powder, and bake it at a predetermined temperature. Since post-addition of TiO2 is required, an increase in production man-hours, the equipment used, and the types of raw materials is expected in the production of soft ferrites. Therefore, it may hinder the provision of cores at low cost. Further, 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 the magnetic permeability on the high temperature side tends to increase, leaving room for further improvement.

[0011] Therefore, an object of the present invention is to provide a NiZn-based ferrite having a high Curie temperature, capable of suppressing the change rate of the complex relative magnetic permeability with respect to temperature, excellent in productivity, a core using the same, and a noise filter.

Means for Solving the Problems

[0012] The first invention is a NiZn-based ferrite comprising 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 15.00 mol% or more and 17.00 mol% or less in terms of NiO, the total amount of Fe2O3, ZnO, NiO, and CuO being 100 mol%, and the total amount of Fe2O3 and ZnO being 77.00 mol% or more and 78.50 mol% or less.

[0013] In the NiZn-based ferrite of the present invention, it is preferable that the Fe is 47.50 mol% or more and 48.50 mol% or less in terms of Fe2O3, and the Zn 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 the complex relative magnetic permeability μ 25 is preferably 800 or more and 1200 or less. However, the complex relative magnetic permeability μ 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 has a complex relative permeability μ 25 with respect to the complex relative permeability μ max and a change rate Δμ max of 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.

Effects of the Invention

[0021] ​According to the present invention, it is possible to provide a NiZn-based ferrite having a high Curie temperature and capable of suppressing the change rate of the complex relative permeability with respect to temperature, while being excellent in productivity, a magnetic core using the same, and a noise filter.

Brief Description of Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Mode for Carrying Out the Invention

[0023] Hereinafter, the NiZn ferrite according to one embodiment of the present invention, the magnetic core using the same, and the noise filter will be specifically described. Unless otherwise specified, the description of one embodiment is also applicable to other embodiments. Further, the following description is not limiting, and various changes and additions may be made within the scope of the technical idea of the present invention, and it can be appropriately changed.

[0024] FIG. 9 is an external perspective view of a noise filter, and the NiZn ferrite of the present invention is used, for example, for its magnetic core. The noise filter 10 includes a drum-shaped core (first magnetic core) 21, a plate-shaped core (second magnetic core) 22, windings 30 provided on the first magnetic core 21, and terminals 31 and 32. The second magnetic core 22 is arranged so as to cover the first magnetic core 21, and is configured in a closed magnetic circuit structure in which they are adhesively fixed to each other.

[0025] FIG. 8 is a perspective view showing the noise filter 10 of FIG. 9 excluding the second magnetic core 22. The first magnetic core 21 has a shaft portion (not shown) and a first flange portion 25 and a second flange portion 26 at its end. Two conducting wires are wound in a spiral bifilar winding on the shaft portion of the first magnetic core 21 to form a first conducting wire 30a and a second conducting wire 30b. Two terminals 31 and 32 are formed on the first flange portion 25 of the first magnetic core 21. Although only the terminal 33 appears on the second flange portion 26, two terminals similar to the first flange portion 25 are formed, and each of the flange portions has two terminals. One end of the first conducting wire 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 conducting wire 30b is connected to the third terminal 32, and the other end is connected to the fourth terminal 33.

[0026] FIG. 7 is an equivalent circuit diagram of the noise filter (common mode choke coil) shown in FIG. 9. In the figure, terminal T1 corresponds to the first terminal 31 in the noise filter of FIG. 9. Also, terminal T2 corresponds to a second terminal (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) The NiZn-based ferrite used for the magnetic core consists of 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 14.80 mol% or more and 18.00 mol% or more in terms of NiO, with the total amount of Fe2O3, ZnO, NiO, and CuO being 100 mol%, and the total amount of Fe2O3 and ZnO being represented by a composition of 77.00 mol% or more and 78.50 mol% or less. In addition, inevitable impurity elements in the raw materials may be included.

[0028] It is preferable that Fe is 47.50 mol% or more and 48.60 mol% or less in terms of Fe2O3. As the amount of Fe2O3 increases, the change rate Δμ of the complex relative permeability μ described later min and the change rate Δμ max increase in absolute value, and if it exceeds 48.60 mol%, the desired change rate Δμ min , Δμ max may not be obtained. Here, the desired change rate Δμ min , Δμ max means that the absolute values of the change rates Δμ min , Δμ max are each 40% or less. Also, if it is less than 47.50 mol%, the complex relative permeability μ at a temperature of 25 ° C 25 decreases, and the desired complex relative permeability μ 25 may not be obtained. The desired complex relative permeability μ 25 is 800 or more and 1200 or less. It is more preferable that Fe2O3 is 48.50 mol% or less. Also, 47.80 mol% or more is more preferable, and 48.00 mol% or more is even more preferable.

[0029] Zn is preferably 29.00 mol% or more and 30.10 mol% or less in terms of ZnO conversion. When ZnO is less than 29.00 mol%, the desired complex relative permeability μ 25 may not be obtained. When it exceeds 30.10 mol%, a Curie temperature Tc of 160 °C or higher may not be obtained. The change rate Δμ max is preferably 29.25 mol% or more and preferably 29.90 mol% or less to reduce it.

[0030] And the contents of Fe2O3 and ZnO are preferably 77.00 mol% or more and 78.50 mol% or less. By setting it to 77.00 mol% or more, the complex relative permeability μ 25 can be made 800 or more. More preferably, it is 77.30 mol% or more. Also, it is preferably 78.40 mol% or less.

[0031] Cu is preferably 5.50 mol% or more and 6.50 mol% or less in terms of CuO conversion. When CuO is less than 5.50 mol% or exceeds 6.50 mol%, the desired complex relative permeability μ 25 may not be obtained. The preferred content of CuO is 5.70 mol% or more. Also, 6.30 mol% or less is preferred.

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

[0033] As impurity elements, specifically, 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. can be mentioned. In the present invention, except for Mn, Ca, and Si, any of them can affect the Curie temperature Tc of NiZn-based ferrite and the change rate Δμ min of the complex relative permeability with respect to temperature, Δμ maxIt may be included as long as it does not affect, that is, within the range where the desired performance can be obtained.

[0034] Among the impurity elements contained in the raw materials, Mn, which is contained in a large amount in Fe2O3 serving as the raw material, is about several thousand ppm in terms of oxide conversion, and the other impurity elements are preferably limited to several ppm to several hundred ppm each in terms of oxide conversion. In NiZn ferrites, with respect to 100 parts by mass of the total amount of Fe2O3, ZnO, NiO, and CuO, Mn is preferably 0.500 parts by mass or less in terms of Mn3O4 conversion, more preferably 0.3 parts by mass or less. Ca is preferably 0.025 parts by mass or less in terms of CaO conversion, and Si is preferably 0.250 parts by mass or less in terms of SiO2 conversion. Among the inevitable impurities, Na, S, Cl, P, Cr, and B are preferably minimized so that abnormal sintering such as insufficient sintering or coarse crystals does not occur, and the total is preferably 0.1 parts by mass or less, more preferably 0.05 parts by mass or less. Further, each of the other inevitable impurities is preferably 0.005 parts by mass or less. The total amount of Mn, Ca, and Si in terms of oxide conversion with respect to 100 parts by mass of the total amount of Fe2O3, ZnO, NiO, and CuO is preferably 0.600 parts by mass or less.

[0035] The quantification of each component of Fe2O3, ZnO, NiO, and CuO can be carried out by X-ray fluorescence analysis and ICP emission spectrometry. First, qualitative analysis of the contained 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 by X-ray fluorescence analysis in advance, and then the contained elements are quantified by the calibration curve method of comparing with standard samples. In addition, the inevitable impurities can be quantified by means such as combustion-infrared absorption method and atomic absorption method. Note that except for Mn, which is contained in a large amount in the raw material of Fe2O3, and Ca and Si, which are abundant in nature and are likely to cause contamination, the other elements are contained in trace amounts even if they are contained. Therefore, based on the values calculated according to the composition ratios of Fe2O3, ZnO, NiO, and CuO from the amounts described in the inspection table of the raw materials of Fe2O3, ZnO, NiO, and CuO, the amounts contained in NiZn ferrites can be calculated from the composition ratios without any problem.

[0036] (Method for manufacturing NiZn-based ferrite) Compounds (oxides) of Fe, Zn, Ni, and Cu that make up NiZn-based ferrite are used as raw materials, and after wet-mixing them in a predetermined ratio, they are dried to obtain raw material powder. The raw material powder is calcined at a temperature of 700 °C or higher and lower than the sintering temperature to promote spinelization and obtain a calcined body.

[0037] As spinelization progresses, it takes time to grind the calcined body. Therefore, the calcination temperature lower than the sintering temperature is preferably specifically 100 °C or more 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, so it is preferably 700 °C or more. The calcination temperature is preferably 850 °C or more. When the composition of the calcined body has a difference (deviation) from the desired composition, when grinding the calcined body, compounds of each element of Fe, Zn, Ni, and Cu may be added to adjust the composition.

[0038] The calcined body is put into a ball mill together with ion-exchanged water and wet-ground to obtain a slurry. The grinding of the calcined body is preferably carried out until the average particle size of the ground powder (measured by the 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 hour or more and 4.0 hours or less. If it is less than 0.1 hour, a preferable grinding particle size may not be obtained, and if it exceeds 4.0 hours, there is a risk of an increase in the mixing of impurities due to the wear of members such as the grinding media and containers of the grinder.

[0039] A binder such as polyvinyl alcohol is added to the slurry, granulated with 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 or higher and 1200 °C or lower to obtain a sintered body (core of NiZn-based ferrite). The firing process includes a heating process, a temperature holding process, and a cooling process. The atmosphere in the firing process may be an inert gas atmosphere or an air atmosphere. In the temperature holding process at a temperature of 1000 °C or higher and 1200 °C or lower, it is preferable to hold it for a predetermined time within a predetermined temperature range.

[0040] When the average pulverized particle size of the calcined powder is small, the sintering reaction activity is high, and densification is likely to be promoted from a low temperature. On the other hand, when the set temperature of the firing furnace is high, sintering becomes excessive, resulting in a coarse crystal structure and making it difficult to obtain a sintered body with uniform crystal grain size and high density. By setting the average particle size of the pulverized powder to 1.2 μm or more and the sintering temperature in the firing process to 1000 °C or more and 1200 °C or less, the complex relative permeability μ 25 of the sintered body and the change rate Δμ min of the complex relative permeability μ max become stable, which is preferable.

[0041] The complex relative permeability μ, the sintered body density ds, and the average crystal grain size d of the obtained sintered body can be measured by the following methods. Also, from the obtained complex relative permeability μ, the change rate Δμ max、 Δμ min can be calculated from the real part μ' and the imaginary part μ" of the complex relative permeability μ to obtain the impedance (normalized impedance Z N ).

[0042] (1) Complex relative permeability μ Use the sintered body as an annular magnetic core, and the coil component wound with a conductor as the evaluation sample. Using an LCR meter (4285A manufactured by Agilent Technologies), measure the inductance L m and the resistance R m at a current of 100 kHz and 1 mA, and calculate the complex relative permeability μ, its real part μ', and imaginary part μ" using Equations 2 to 4 from the obtained inductance L m and resistance R m .

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

Equation

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

Equation

[0045]

Number

[0046] Note that the annular magnetic core has a rectangular cross-section perpendicular to the magnetic path, with an inner diameter of φ20 mm, an outer diameter of φ30 mm, and a thickness of 8 mm. Also, Ae is the effective cross-sectional area of the magnetic core (m 2 ), le is the effective magnetic path length of the magnetic core (m), μ0 is the magnetic permeability of vacuum [4π×10 -7 (H / m), N is the number of turns of the conductor, f is the frequency (Hz), Lm is the measured inductance (H), and Rm is the measured resistance (Ω). An enameled wire with a wire diameter of φ0.5 mm was used for the conductor, and the number of turns N was 20 turns.

[0047] (2) Rate of change Δμ of the complex relative permeability μ max , Δμ min Connect the evaluation sample used for measuring the complex relative permeability μ to the measuring fixture in the thermostat. Note that the measuring fixture is connected to an LCR meter (4285A). Between -40°C and 150°C, change the temperature of the evaluation sample and measure the inductance L m and the resistance R m at a frequency of 100 kHz. The inductance L m and the resistance R m obtained under the condition of temperature T are used to calculate the complex relative permeability μ T from Equation 2 to Equation 4. The complex relative permeability μ T is the complex relative permeability μ at temperature T. For example, the complex relative permeability μ 25 is the complex relative permeability μ at 25°C. Also, the complex relative permeability μ max is the highest complex relative permeability μ at temperatures from -40°C to 150°C, and Tμ max is the temperature at which the complex relative permeability becomes μ max . Also, the complex relative permeability μ min is the lowest complex relative permeability μ at temperatures from -40°C to 150°C, and Tμ min is the temperature at which the complex relative permeability becomes μ min . Using the obtained complex relative permeability μ, the rate of change Δμ maxFrom Equation 6, the rate of change Δμ min is calculated.

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

Number

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

Number

[0050] (3) Normalized impedance Z N The frequency characteristics of Similar to the above-mentioned complex relative permeability μ, the inductance L at a frequency of 80 kHz to 30 MHz with a current of 1 mA is measured by an LCR meter (4285A) m and the resistance R m at room temperature, and the obtained inductance L m and the resistance R m are used to calculate the real part μ' and the imaginary part μ'' of the complex relative permeability μ by Equations 2 and 3. The obtained real part μ' and imaginary part μ'' are used to calculate the normalized impedance Z N by Equation 7. Note that an Agilent Technologies test fixture 16085B was used for the measurement.

[0051]

Number

[0052] (4) Curie temperature Tc The Curie temperature Tc was determined in accordance with JIS C2560 using an LCR meter with similar samples.

[0053] (5) Sintered body density ds The density of the NiZn ferrite sintered body was calculated by the bulk density method from the dimensions and weight of the sintered body. The sintered body density was 5.10×10 3 kg / m 3 was used as the threshold value, and values exceeding the threshold were judged as "good". If the sintered body density is low, insufficient sintering is considered, the mechanical strength is inferior, and chipping and cracking are likely to occur.

[0054] (6) Average crystal grain size The NiZn ferrite sintered body was thermally etched at a temperature lower than the firing temperature, and a scanning electron microscope (SEM) photograph (3000 times magnification) of its surface was taken. The observation area of the SEM photograph was 33 μm × 43 μm at 3000 times magnification. Three arbitrary straight lines of length L1 were drawn on the SEM photograph, the number of crystal grains N1 existing on each straight line was counted, the value L1 / N1 obtained by dividing the length L1 by the number of particles N1 for each straight line was calculated, and the sum of the values of L1 / N1 was divided by 3 to obtain the average crystal grain size. Note that thermal etching may be performed at a temperature at which grain boundaries can be confirmed, and typically it is preferably performed at a temperature about 50 °C to 100 °C lower than the firing temperature. When the firing temperature of the NiZn ferrite sintered body is unknown, thermal etching may be started at a low temperature and performed while gradually increasing the temperature until grain boundaries can be confirmed.

Examples

[0055] Examples 1 to 21 and Comparative Examples 1 to 9 The respective raw materials of Fe2O3 powder, ZnO powder, CuO powder, and NiO powder were weighed so as to obtain a NiZn ferrite having the composition shown in Table 1, wet-mixed, dried, and calcined at a temperature of 900 °C for 1 hour. Each of the obtained calcined bodies was put into a ball mill together with ion-exchanged water and pulverized to form a slurry. A part of the obtained slurry was dried and the average pulverized particle size was evaluated by the air permeability method. All of the average pulverized particle sizes were in the range of 1.5 μm to 1.7 μm. Polyvinyl alcohol was added to the remaining slurry as a binder, dried and granulated together by a spray dryer, and pressure-molded to obtain each annular molded body. Note that Mn in the NiZn ferrite is selected such that when the total amount of Fe2O3, ZnO, CuO, and NiO is 100 parts by mass, Mn, Si, and Ca are 0.250 parts by mass or less in terms of oxide even including other impurity elements.

[0056] Each molded body was sintered at a temperature of 1100 °C for a holding time of 2 hours to obtain each annular NiZn ferrite sintered body having an outer diameter of 30 mm × an inner diameter of 20 mm × a thickness of 8 mm. The firing atmosphere was in air.

[0057] The density ds, complex relative permeability μ, real part μ' of the complex relative permeability μ, imaginary part μ' of the complex relative permeability μ, average crystal grain size, Curie temperature Tc, change rates Δμmin and Δμmax of the complex relative permeability μ, and normalized impedance Z of each NiZn ferrite sintered body N were measured or calculated by the above method. The obtained results are also shown in Table 1 and FIGS. 1 to 6. In Table 1, the change rate Δμ of the complex relative permeability μ -40 , Δμ 100 , Δμ 150 is the change rate of the complex relative permeability μ 25 with respect to μ T (T = -40 °C, 100 °C, 150 °C). When μ 25 is smaller than μ T and the change rate Δμ is negative, it is indicated with a minus sign. In FIGS. 1 to 4, the examples are indicated by white circles, the comparative examples are indicated by cross marks and black squares, and the black squares also indicate that the Curie temperature Tc is less than 160 °C.

[0058]

Table 1

[0059] In both the examples and the comparative examples, the density ds of any NiZn-based ferrite sintered body was excellent, exceeding 5.15×10 3 kg / m 3 . Also, the average crystal grain size was in the range of 5 μm to 20 μm.

[0060] Figure 2 is a diagram showing the relationship between the amount of ZnO and the Curie temperature Tc of the NiZn-based ferrite. As the amount of ZnO increased, the Curie temperature Tc decreased, and in Comparative Examples 5 to 8 where the amount of ZnO exceeded 30.10 mol%, it was less than 160 °C.

[0061] Figures 3 and 4 are diagrams showing the relationship between the amount of Fe2O3 and the change rates Δμmax and Δμmin of the complex relative permeability μ. The change rate Δμ max increased rapidly when the amount of Fe2O3 exceeded 48.60 mol%. Also, the change rate Δμ min tended to increase gradually with respect to the amount of Fe2O3. Also, in Comparative Examples 5 to 8 where the Curie temperature Tc was less than 160 °C, the temperature at which the complex relative permeability μ min became was 150 °C, while that of the other evaluation samples was -40 °C, and the change rate Δμ min increased significantly.

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

[0063] Figures 5 and 6 show the frequency characteristics of the normalized impedance Z N of the evaluation samples. Figure 5 uses the evaluation sample of Example 21 where μ 25 is 940, and Figure 6 uses 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, in Table 2, 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 are shown together with Z 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, μ' at a temperature of 100°C and a frequency of 30 MHz 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 The Fe2O3 powder, ZnO powder, CuO powder, and NiO powder were weighed so as to obtain the 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 body was put into an attritor together with ion-exchanged water and pulverized for 1 minute to 8 hours respectively as shown in Table 3 to form a slurry. A part of the obtained slurry was dried and the average pulverized particle size was evaluated by the air permeability method. The average pulverized particle size was in the range of 0.80 μm to 1.85 μm. When there was a compositional deviation by fluorescent X-ray analysis, the raw materials were added and adjusted to the composition shown in Example 21. Polyvinyl alcohol was added to the remaining slurry as a binder, dried and granulated by a spray dryer, and pressure-molded to obtain each annular molded body.

[0067] Each molded body was sintered at a temperature of 1100 °C for a holding time of 2 hours to obtain each annular NiZn ferrite sintered body having an outer diameter of 30 mm × an inner diameter of 20 mm × a thickness of 8 mm. The firing atmosphere was in air.

[0068] The density ds, complex relative permeability μ, real part μ' of the complex relative permeability μ, imaginary part μ" of the complex relative permeability μ, and change rate Δμ of the complex relative permeability μ of each NiZn ferrite sintered body were measured or calculated by the above method. Table 3, FIGS. 7 and 8 also show the obtained results. FIG. 7 is a diagram showing the relationship between the pulverized particle size and the complex relative permeability μ, and FIG. 8 is the change rate Δμ of the complex relative permeability μ min 、Δμ max and the relationship therewith.

[0069]

Table 3

[0070] As shown in FIG. 10, when the pulverized particle size of the calcined body exceeds 1.20 μm, the complex relative permeability μ becomes stable. Also, as shown in FIG. 11, when the pulverized particle size exceeds 1.20 μm, the change rate Δμ of the complex relative permeability μ min 、Δμ max becomes stable. On the other hand, when the pulverized particle size is 1.20 μm or less, the complex relative permeability μ decreases, and the change rate Δμ of the complex relative permeability μ 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-based 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 body was put into an attritor together with ion-exchanged water and pulverized for 0.5 hour to form 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-based 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 Nin-based ferrite sintered body were measured or calculated by the above method. Table 4 and FIG. 12 show the obtained results as well. FIG. 12 is a diagram showing 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 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 minIf a pulverized particle size with a smaller diameter that increases the sinterability is selected within a range where it does not decrease, and sintering is performed at a lower firing temperature, further property improvement of the NiZn-based ferrite can be expected.

[0076] Examples 32 to 42 and Comparative Examples 10 to 13 Weighed raw materials of Fe2O3 powder, ZnO powder, CuO powder, NiO powder, Mn3O4 powder, CaCO3 powder, and SiO2 powder were used so as to obtain NiZn-based ferrites having the compositions shown in Table 5. After wet-mixing the Fe2O3 powder, ZnO powder, CuO powder, and NiO powder, they were dried and calcined at a temperature of 900 °C for 1 hour. Each of the obtained calcined bodies was put into a ball mill together with Mn3O4 powder, CaCO3 powder, SiO2 powder, and ion-exchanged water, and pulverized with an attritor to form a slurry. A part of the obtained slurry was dried, and the average pulverized particle size was evaluated by the air permeability method. The average pulverized particle size was all in the range of 1.7 μm to 1.9 μm. Polyvinyl alcohol was added to the remaining slurry as a binder, dried and granulated with a spray dryer, and pressure-molded to obtain each annular molded body.

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

[0078] The density ds, complex relative permeability μ, Curie temperature Tc, and change rate Δμ of the complex relative permeability μ of each NiZn-based ferrite sintered body min , Δμ max were measured or calculated by the above method. The obtained 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 the sub-components.

[0079]

Table 5

[0080]

Table 6

[0081] In both the examples and the comparative examples, the density ds of any NiZn-based ferrite sintered body was good, exceeding 5.15×10 3 kg / m 3 . Also, the average crystal grain size was in the range of 5 μm to 20 μm.

[0082] In Comparative Examples 10 and 11 where the amount of Mn3O4 increased and exceeded 0.500 parts by mass, the complex relative permeability μ on the low-temperature side decreased and increased on the high-temperature side, and the change rate Δμ min , Δμ max (less than or equal to 40% in absolute value) could not be obtained. When the amount of CaO increased, the change rates Δμ min , Δμ max of the complex relative permeability μ became smaller, but in Comparative Examples 12 and 13 where it exceeded 0.250 parts by mass, the complex relative permeability μ decreased and the complex relative permeability μ became less than 800. Also, when the amount of SiO2 increased, the complex relative permeability μ increased, but the change rates Δμ min , Δμ max of the complex relative permeability μ also increased.

[0083] As described above, by using an NiZn-based ferrite composed of 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 14.80 mol% or more and 18.00 mol% or less in terms of NiO, with the total amount of Fe2O3, ZnO, NiO, and CuO being 100 mol% and the total amount of Fe2O3 and ZnO being 77.00 mol% or more and 78.50 mol% or less, a NiZn-based ferrite with a high Curie temperature Tc and a small change rate Δμ min , Δμ max of the complex relative permeability μ with respect to temperature can be obtained. Also, since there is no need for a complex microstructure, it is excellent in productivity. Further, a noise filter using it can reduce the impedance fluctuation associated with temperature change and can have good temperature characteristics.

Explanation of symbols

[0084] 10 Electronic component 21 First core 22 Second core 30 Coil (conductive wire) 31, 32, 33 Terminals

Claims

1. Fe ２ O ３ In terms of Fe, it is "47.50 mol% or more and 48.60 mol% or less" Zn of "29.00 mol% or more and 30.10 mol% or less" in terms of ZnO, Cu is "5.50 mol% or more and 6.50 mol% or less" in terms of CuO, NiO equivalent of "16.51 mol% to 18.00 mol%" contains and, Fe ２ O ３ When the total amount of ZnO, NiO and CuO is 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"; NiZn ferrite.

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

3. The NiZn-based ferrite according to claim 1 or 2, The Curie temperature Tc is 160° C. or higher, Complex relative permeability μ ２５ is the complex relative permeability μ under the condition of "frequency 100 kHz, temperature 25 ° C.", which is 800 to 1200; NiZn ferrite.

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

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

6. The NiZn-based ferrite according to any one of claims 1 to 5, The total amount of the Fe, Zn, Ni and Cu is Fe ２ O ３ , when calculated as 100 parts by mass in terms of ZnO, NiO and CuO, Mn ３ O ４ "0.500 parts by mass or less" of Mn converted into Ca in an amount of "0.025 parts by mass or less" calculated as CaO; SiO ２ "0.250 parts by mass or less" of Si in terms of conversion, Contains NiZn ferrite.

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

8. A noise filter using the magnetic core according to claim 7.

9. 9. The noise filter according to claim 8, The magnetic core includes a first magnetic core having a columnar shaft portion and flange portions at both ends of the shaft portion; a plate-shaped second magnetic core disposed between the flanges of the first magnetic core; A noise filter comprising a first conducting wire and a second conducting wire wound around an axis of the first magnetic core.

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