JP2022039923A - Nickel zinc-based ferrite - Google Patents

Abstract

To provide a NiZn-based ferrite which is superior in productivity, and which can suppress the increase in changing rate of a complex relative permeability to a temperature.SOLUTION: A NiZn-based ferrite comprises 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. Supposing that the total quantity of Fe2O3, ZnO, NiO and CuO is 100 mol%, and the total quantities of Fe, Zn, Ni and Cu as primary components are 100 pts.mass in terms of Fe2O3, ZnO, NiO and CuO respectively, Mn is 0.250 pt.mass or less in terms of Mn3O4, Ca is 0.025 pt.mass or more and 0.250 pt.mass or less in terms of CaO, and Si is 0.050 pt.mass in terms of SiO2.SELECTED DRAWING: None

Description

The present invention relates to NiZn-based ferrite.

In recent 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 devices has been adopted. Various electronic components are used in vehicle control systems, but the signal path is to prevent noise leakage in data communication, suppress external noise from being superimposed on the signal path, and prevent malfunction of in-vehicle devices. A noise filter is used for. As the noise filter, a common mode choke coil in which a conducting wire is wound around a ferrite core (hereinafter referred to as a magnetic core) is used. The configuration of the common mode choke coil varies, but there are, for example, a drum type core as described in Patent Document 1 and a common mode choke coil using a plate-shaped core covering the drum-shaped core as a magnetic core.

In the noise filter, the 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.

In general, it is known that the complex relative permeability μ of soft ferrite has a limit of snake (Snoek) in which the real part μ'decreases when the frequency increases due to the loss due to magnetic resonance. The higher the complex relative permeability μ, the lower 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 expressed by Equation 1, and its real part μ', imaginary part μ'. Impedance Z increases exponentially as the frequency increases, and decreases as the real part μ'and the imaginary part μ'decrease.

For example, CAN (Control Area Network)) is known as a standard for data communication by differential transmission 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 several tens of MHz band, the noise filter used in the signal path is as high as 10 MHz or more so as to attenuate the common mode noise. It is required that the impedance is large in the frequency band.

Noise filters are also used in high temperature automobile engine rooms. Therefore, the magnetic transition temperature (Curie temperature Tc) of soft ferrite is at least a temperature exceeding 150 ° C., which exceeds the temperature used, so that it can be used in a wide temperature range of, for example, −40 ° C. to + 150 ° C. It is required that the temperature dependence of the complex relative magnetic permeability μ is small.

In response to such requirements, Patent Document 2 contains Fe, Zn, Ni, Cu, and Ti, and software for a noise filter in which a compound containing Ti is dispersed in the grain boundaries of Fe—Zn—Ni—Cu crystals. Discloses ferrite. The Curie temperature is 160 ° C or higher, the temperature change rate of magnetic permeability can be suppressed to -40% or higher and 40% or lower, and it has excellent stable noise reduction performance in a wide range of temperatures from low temperature to high temperature. It is stated that it can be used as a noise filter.

Japanese Unexamined Patent Publication No. 2012-89804 Japanese Unexamined Patent Publication No. 2011-246343

In Patent Document 2, in order to form a grain boundary structure in which a compound containing Ti is dispersed at a grain boundary, TiO ₂ is further added to the calcined powder of Fe _{2O 3} , ZnO, NiO, and CuO powder and pulverized. Then, it is necessary to mold the obtained pulverized powder and bake it at a predetermined temperature. Since TiO ₂ needs to be added afterwards, it is expected that the production man-hours, equipment used, and types of raw materials will increase in the production of soft ferrite. Therefore, it may be difficult to provide the magnetic core at a low price. Further, according to Table 2 of Patent Document 2, the Curie temperature Tc tends to decrease as the amount of TiO ₂ increases, and the temperature change rate of the magnetic permeability on the high temperature side tends to increase, and there is room for further improvement.

Therefore, an object of the present invention is to provide a NiZn-based ferrite having a high Curie temperature, capable of suppressing the rate of change in complex relative permeability with respect to temperature, and having excellent productivity.

In the first invention, Fe of 47.50 mol% or more and 48.60 mol% or less in terms of Fe ₂ O ₃ , Zn of 29.00 mol% or more and 30.10 mol% or less in terms of ZnO, and 5.50 mol% or more in terms of CuO 6 It is composed of .50 mol% or less of Cu and Ni of 15.00 mol% or more and 17.00 mol% or less in terms of NiO, and the total amount of Fe ₂ O ₃ , ZnO, NiO and CuO is 100 mol%, and Fe, Zn and Ni When the total amount of Cu and Cu is 100 parts by mass in terms of Fe ₂ O ₃ , ZnO, NiO and CuO, respectively.
NiZn-based Mn is 0.250 parts by mass or less in terms of Mn ₃ O ₄ , Ca is 0.025 parts by mass or more and 0.250 parts by mass or less in CaO conversion, and Si is 0.050 parts by mass or less in terms of SiO ₂ . Ferrite.

The NiZn-based ferrite of the present invention has a Curie temperature Tc of 165 ° C. or higher, a complex relative magnetic permeability μ ₂₅ of 650 or higher, and an absolute change rate Δμ _max of the complex relative magnetic permeability μ _max with respect to the complex relative magnetic permeability μ ₂₅ . The value is preferably 5% or less, and the change rate _Δμmin of the complex relative permeability μ _min with respect to the complex relative permeability μ ₂₅ is preferably 20% or less in absolute value.
However, the complex relative permeability μ _max is the highest complex relative permeability μ under the condition of a frequency of 100 kHz between -40 ° C and 150 ° C, and the complex relative permeability μ _min is -40 ° C to 150 ° C. It is the lowest complex relative permeability μ under the condition of a frequency of 100 kHz.
Further, the rate of change Δμ _max = (μ _max −μ ₂₅ ) / μ ₂₅ × 100 (%), and the rate of change Δμ _min = ( _μmin −μ ₂₅ ) / μ ₂₅ × 100 (%).
Further, the complex relative magnetic permeability μ ₂₅ is a complex relative magnetic permeability μ at a frequency of 100 kHz and a temperature of 25 ° C.

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

It is a figure which shows the relationship between the total amount of Fe ₂ O ₃ and Zn O of the NiZn-based ferrite of this invention, and the complex relative magnetic permeability μ ₂₅ . It is a figure which shows the relationship between the ZnO amount of the NiZn-based ferrite of this invention, and the Curie temperature Tc. It is a figure which shows the relationship between the Fe ₂ O ₃ amount of NiZn-based ferrite of this invention, and the rate of change Δμmax. It is a figure which shows the relationship between the amount of Fe ₂ O ₃ of the NiZn-based ferrite of this invention, and the rate of change Δμmin. It is an equivalent circuit diagram which shows an example of the electronic component which uses the NiZn-based ferrite of this invention. It is a perspective view which shows the structure which provided the coil and the terminal in the magnetic core which used the NiZn-based ferrite of this invention. It is a perspective view which shows the appearance structure of the electronic component shown in FIG.

Hereinafter, a NiZn-based ferrite according to an embodiment of the present invention, a magnetic core using the same, and a noise filter will be specifically described. Unless otherwise specified, the description of one embodiment also applies to other embodiments. Further, the following description is not limited, and various changes and additions may be made within the scope of the technical idea of the present invention, and the following changes can be made as appropriate.

FIG. 7 is an external perspective view of the noise filter, and the NiZn-based ferrite of the present invention is used, for example, for the magnetic core thereof. The noise filter 10 includes a drum-shaped core (first magnetic core) 21, a plate-shaped core (second magnetic core) 22, windings 30 and terminals 31 and 32 provided on the first magnetic core 21, and the first magnetic core. The second magnetic core 22 is arranged so as to cover the 21 and is configured as a closed magnetic circuit structure in which the second magnetic cores 22 are adhered and fixed to each other.

FIG. 6 is a perspective view showing the noise filter 10 of FIG. 7 excluding the second magnetic core 22. The first magnetic core 21 has a shaft portion (not shown), a first flange portion 25 and a second flange portion 26 at its ends, and two conducting wires are provided on the shaft portion of the first magnetic core 21. It is spirally wound with a bifilar winding to form the first conductor 30a and the second conductor 30b. Two terminals 31 and 32 are formed on the first flange portion 25 of the first magnetic core 21. Further, although only the terminal 33 appears on the second flange portion 26, two terminals similar to those of the first flange portion 25 are formed, and each of the flange portions has 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). Further, one end of the second conductor 30b is connected to the third terminal 32, and the other end is connected to the fourth terminal 33.

FIG. 5 is an equivalent circuit diagram of the noise filter (common mode choke coil) shown in FIG. 7. In the figure, the terminal T1 corresponds to the first terminal 31 in the noise filter of FIG. Further, the terminal T2 corresponds to a second terminal (not shown). The terminal T3 corresponds to the third terminal 32, and the terminal T4 corresponds to the fourth terminal 33.

(Composition of NiZn-based ferrite)
The NiZn-based ferrite used for the magnetic core is Fe of 47.50 mol% or more and 48.60 mol% or less in terms of Fe ₂ O3 _, Zn of 29.00 mol% or more and 30.10 mol% or less in terms of ZnO, and 5.50 mol% in terms of CuO. It is composed of Cu of 6.50 mol% or less and Ni of 14.80 mol% or more and 18.00 mol% or more in terms of NiO, and the total amount of Fe ₂ O ₃ , ZnO, NiO and CuO is 100 mol%, and Fe, Zn, When the total amount of Ni and Cu is 100 parts by mass in terms of Fe ₂ O ₃ , ZnO, NiO and CuO, respectively, Mn is 0.250 parts by mass or less in terms of Mn ₃ O ₄ , and Ca is 0.025 in terms of CaO. It is represented by a composition of 0 parts by mass or more and 0.250 parts by mass or less, and Si is 0.010 parts by mass or less in terms of SiO ₂ . In addition to this, unavoidable impurity elements in the raw material may be contained.

Fe is preferably 47.50 mol% or more and 48.60 mol% or less in terms of Fe ₂ O ₃ . As the amount of Fe ₂ O ₃ increases, the absolute values of the rate of change Δμ _min and the rate of change _{Δμ max} of the complex relative permeability μ, which will be described later, increase _. It may not be obtained. Here, the desired rate of change Δμ _min and Δμ _max are such that the absolute values of the rates of change Δμ _min and Δμ _max are 40% or less, respectively. If it is less than 47.50 mol%, the complex relative magnetic permeability μ ₂₅ at a temperature of 25 ° C. may decrease, and the desired complex relative magnetic permeability μ ₂₅ may not be obtained. The desired complex relative permeability μ ₂₅ is 650 or more. Fe ₂ O ₃ is more preferably 48.50 mol% or less. Further, 47.80 mol% or more is more preferable, and 48.00 mol% or more is further preferable.

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

The contents of Fe ₂ O ₃ and Zn O 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 magnetic permeability μ ₂₅ can be set to 800 or more. More preferably, it is 77.30 mol% or more. Further, it is preferably 78.40 mol% or less.

Cu is preferably 5.50 mol% or more and 6.50 mol% or less in terms of CuO. If CuO is less than 5.50 mol% or more than 6.50 mol%, the desired complex relative permeability μ ₂₅ may not be obtained. The preferable content of CuO is 5.70 mol% or more. Further, it is preferably 6.30 mol% or less.

Further, Ni is preferably 14.80 mol% or more and 18.00 mol% or less in terms of NiO. The amount of NiO is the balance obtained by subtracting the total amount of the above components of Fe ₂ O ₃ , ZnO, and CuO from the total 100 mol% of Fe ₂ O ₃ , ZnO, NiO, and CuO.

Specific examples of the 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 and the like. In the present invention, except for Mn, Ca, and Si, the Curie temperature Tc of NiZn-based ferrite and the rate of change of complex relative permeability with respect to temperature _Δμmin and _Δμmax are not affected, that is, desired performance is obtained. It may be included as long as it exists.

Among the impurity elements, Mn contained in a large amount in Fe ₂ O ₃ which is a raw material is contained in the raw material because the absolute values of the rate of change of the complex ferrite permeability Δμ _min and Δμ _max increase as the amount increases. The amount of Mn contained in the NiZn-based ferrite is set to about several thousand ppm or less in terms of oxide, and the amount of Mn contained in NiZn-based ferrite is 100 parts by mass of the total amount of Fe, Zn, Ni, and Cu in terms of Fe _{2O 3} , ZnO, NiO, and CuO. It is preferable that the amount is 0 parts by mass or more and 0.250 parts by mass or less in terms of Mn ₃ O ₄ .

Si is preferable in that the Curie temperature Tc and the complex relative permeability μ ₂₅ of the NiZn-based ferrite increase as the amount increases, but the absolute values of the rate of change of the complex relative permeability Δμ _min and Δμ _max also increase. , Si contained in NiZn-based ferrite is 0 parts by mass or more and 0.050 mass in terms of SiO ₂ with respect to 100 parts by mass of the total amount of Fe, Zn, Ni, and Cu in terms of Fe ₂ O ₃ , ZnO, NiO, and CuO. It is preferably less than or equal to the part. More preferably, it is 0.010 part by mass or less.

As the amount of Ca increases _, the rate of change in the complex relative magnetic permeability of NiZn _- based ferrite decreases in absolute values of _Δμmin and _Δμmax . It is preferable that the amount is 0.025 parts by mass or more and 0.250 parts by mass or less in terms of CaO with respect to 100 parts by mass in terms of CuO.

It is preferable that the upper limit of the other impurity elements contained in the raw material is several ppm to several tens of ppm in terms of oxides. The amount of other unavoidable impurities contained in the NiZn-based ferrite is preferably 0.005 part by mass or less.

The quantification of each component of Fe ₂ O ₃ , ZnO, NiO, and CuO can be performed by fluorescent X-ray analysis and ICP emission spectroscopic analysis. Contains elements (Fe, Zn, Ni, Cu, Mn, Zr, Sn, P, S, Bi, Mg, Al, Si, Cl, K, Ca, Ti, V, Cr, Co, Pb) by fluorescent X-ray analysis in advance. Qualitative analysis is performed, and then the contained elements are quantified by a calibration beam method comparing with a standard sample. Inevitable impurities can be quantified by means such as combustion-infrared absorption method and atomic absorption method. Except for Mn, which is abundant in the raw material of Fe ₂ O ₃ , and Ca and Si, which are abundant in nature and easily cause contamination, even if other elements are contained, they are in trace amounts. NiZn-based from the composition ratio based on the value calculated according to the composition ratio of Fe _{2O 3} , ZnO, NiO, CuO from the amounts listed in the inspection table of the raw materials of _{2O 3} , ZnO, NiO, and CuO. You may calculate the amount contained in ferrite.

(Manufacturing method of NiZn-based ferrite)
A compound (oxide) powder of each element of Fe, Zn, Ni, and Cu constituting NiZn-based ferrite is used as a raw material, and they are wet-mixed at a predetermined ratio and then dried to obtain a raw material powder. The raw material powder is calcined at 700 ° C. or higher and at a temperature lower than the sintering temperature to promote spinelization, and a calcined body is obtained.

As the spinel formation progresses, it takes time to crush the calcined body. Therefore, the calcining temperature lower than the sintering temperature is preferably 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 that the temperature is preferably 700 ° C. or higher. The calcination temperature is preferably 850 ° C. or higher. If the composition of the calcined body is different (deviation) from the desired composition, the composition is adjusted by adding compounds of Fe, Zn, Ni, and Cu elements when the calcined body is pulverized. May be.

The calcined body is put into a ball mill together with ion-exchanged water and wet-ground to obtain a slurry. The pulverized body is preferably pulverized until the average particle size of the pulverized powder (measured by the air permeation method) is 1.2 μm or more and 2.5 μm or less, and 1.5 μm or more and 2.0 μm or less. Is more preferable. The crushing time is preferably 0.1 hours or more and 4.0 hours or less. If it is less than 0.1 hours, a preferable crushed particle size may not be obtained, and if it is more than 4.0 hours, impurities may increase due to wear of the crushing media of the crusher and members such as a container.

A binder such as polyvinyl alcohol is added to the slurry, granulated with a spray dryer, and then pressure-molded to obtain a molded product having 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 (NiZn-based ferrite magnetic core). The firing step includes a temperature raising step, a temperature holding step, and a temperature lowering step. The atmosphere in the firing step may be an inert gas atmosphere or an atmospheric atmosphere. In the temperature holding step of 1000 ° C. or higher and 1200 ° C. or lower, it is preferable to hold the temperature within a predetermined temperature range for a predetermined time.

When the average crushed particle size of the calcined powder is small, the sintering reaction activity is high and densification is easily promoted from a low temperature. As a result, it becomes difficult to obtain a dense sintered body having a uniform crystal grain size. By setting the average particle size of the crushed powder to 1.2 μm or more and the sintering temperature in the firing step to 1000 ° C or higher and 1200 ° C or lower, the complex relative magnetic permeability μ ₂₅ and the complex relative magnetic permeability μ of the sintered body are changed. It is preferable because the rates Δμ _min and Δμ _max are stable.

The complex relative magnetic 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. Further, the rate of change Δμ _{max and} Δμ _min can be calculated from the obtained complex relative permeability μ.

(1) Complex relative permeability μ
The sintered body is an annular magnetic core, and the coil component around which the conducting wire is wound is used as an evaluation sample. An LCR meter (4285A manufactured by Agilent Technologies, Inc.) measures the inductance L _m and resistance R _m at a current of 100 kHz and 1 mA, and from the obtained inductance L _m and resistance R _m , formulas 2 to 4 The complex relative permeability μ, its real part μ', and its imaginary part μ'are calculated using.

(A) The real part μ'of complex relative permeability μ

（ｃ）複素比透磁率μ (B) Imaginary part μ with complex relative permeability μ ”

(C) Complex relative permeability μ

The annular magnetic core has a rectangular cross section orthogonal to the magnetic path, and has dimensions of an inner diameter of φ20 mm, an outer diameter of φ30 mm, and a thickness of 8 mm. 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), μ ₀ is the magnetic permeability of the vacuum [4π × ^10-7 ] (H / m), and N is the winding of the conducting wire. The number of times, f is the frequency (Hz), Lm is the measurement inductance (H), and Rm is the measurement resistance (Ω). As the conducting wire, an ennick wire having a wire diameter of φ0.5 mm was used, and the number of windings N was 20 turns.

(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 the measuring jig in the constant temperature bath. The measuring jig is connected to an LCR meter (4285A), changes the temperature of the evaluation sample between -40 ° C and 150 ° C, and measures the inductance L _m and resistance R _m at a frequency of 100 kHz. do. The complex relative magnetic permeability μ _T was calculated from Equations 2 to 4 from the inductance L _m and the resistance R _m obtained under the condition of the temperature T. The complex relative magnetic permeability μ _T is the complex relative magnetic permeability μ at the temperature T, and for example, the complex relative magnetic permeability μ ₂₅ is the complex relative magnetic permeability μ at a temperature of 25 ° C. Further, the complex relative magnetic permeability μ _max is the highest complex relative magnetic permeability μ at a temperature from −40 ° C. to 150 ° C., and Tμ _max is the temperature at which the complex relative magnetic permeability μ _max is obtained. The complex relative magnetic permeability μ _min is the lowest complex relative magnetic permeability μ at a temperature from −40 ° C. to 150 ° C., and T μ _min is a temperature at which the complex relative magnetic permeability μ _min . Using the obtained complex relative permeability μ, the rate of change Δμ _max is calculated from Equation 5 and the rate of change Δμ _min is calculated from Equation 6.

The maximum rate of change Δμ _max on the positive side of the complex relative permeability μ is an absolute value calculated by Equation 5.

The maximum rate of change _Δμmin on the negative side of the complex relative permeability μ is the absolute value calculated by Equation 6.

(3) Curie temperature Tc
The Curie temperature Tc was determined by JIS C2560 using a similar sample and using an LCR meter.

(4) Sintered body density ds
The density was calculated by the volume gravimetric method from the dimensions and weight of the sintered body of NiZn-based ferrite. The sintered body density was set to 5.10 × 10 ³ kg / m ³ as a threshold value, and the above threshold value was judged to be “good”. If the density of the sintered body is low, insufficient sintering may be considered, the mechanical strength is inferior, and chipping or cracking is likely to occur.

(5) Average crystal grain size A sintered body of NiZn-based ferrite was thermally etched at a temperature lower than the firing temperature, and a scanning electron microscope (SEM) photograph (3000 times) of the surface thereof was taken. The observation area of the SEM photograph was 33 μm × 43 μm at a magnification of 3000. Draw three arbitrary straight lines of length L1 on the SEM photograph, count the number N1 of crystal grains existing on each straight line, and divide the length L1 by the number of particles N1 for each straight line to obtain the value L1 / N1. Calculated and the sum of the values of L1 / N1 was divided by 3 to obtain the average crystal grain size. The thermal etching may be performed at a temperature at which the crystal grain boundaries can be confirmed, and is typically performed at a temperature about 50 ° C. to 100 ° C. lower than the firing temperature. If the firing temperature of the NiZn-based ferrite sintered body is unknown, thermal etching may be started at a low temperature and gradually increased until the grain boundaries can be confirmed.

Reference Examples 1 to 21 and Comparative Examples 1 to 9
Fe ₂ O ₃ powder, ZnO powder, CuO powder, and NiO powder raw materials weighed so as to obtain NiZn-based ferrite having the composition shown in Table 1 are wet-mixed, dried, and dried at a temperature of 900 ° C. Temporarily baked for hours. Each of the obtained calcined bodies was put into a ball mill together with ion-exchanged water and pulverized to obtain a slurry. A part of the obtained slurry was dried and the average pulverized particle size was evaluated by an air permeation method. The average pulverized grain size was in the range of 1.5 μm to 1.7 μm. Polyvinyl alcohol was added as a binder to the remaining slurry, granulated by drying with a spray dryer, and pressure-molded to obtain each annular molded product. The total amount of Mn in NiZn _- based ferrite is 0.250 parts by mass in terms of oxide when the _total amount of Fe ₂ O ₃ , ZnO, CuO, and NiO is 100 parts by mass. The raw materials to be used are selected as follows.

Each molded body was sintered at a temperature of 1100 ° C. and a holding time of 2 hours to obtain annular NiZn-based ferrite sintered bodies having an outer diameter of 30 mm, an inner diameter of 20 mm, and a thickness of 8 mm. The firing atmosphere is in the atmosphere.

Density ds of each NiZn-based ferrite sintered body, complex relative magnetic permeability μ, real part μ of complex relative magnetic permeability μ, imaginary part μ'of complex relative magnetic permeability μ, average crystal grain size, Curie temperature Tc, complex ratio The rate of change of magnetic permeability μ Δμmin, _Δμmax , and normalized impedance ZN were measured or calculated by the above method. The results are also shown in Table 1 and FIGS. 1 to 6.
In Table 1, the rate of change of complex relative permeability μ Δμ- ₄₀ , Δμ ₁₀₀ , Δμ ₁₅₀ is the change of complex relative permeability μ _T (T = −40 ° C., 100 ° C., 150 ° C.) with respect to μ ₂₅ . The rate. When μ _T is smaller than μ ₂₅ and the rate of change Δμ is negative, it is indicated by adding a minus. In FIGS. 1 to 4, reference examples are indicated by white circles, comparative examples are indicated by cross marks and black square marks, and the black square marks also indicate that the Curie temperature Tc is less than 160 ° C.

In both the reference example and the comparative example, the density ds of each of the NiZn-based ferrite sintered bodies was good, exceeding 5.15 × 10 ³ kg / m ³ . The average crystal grain size was in the range of 5 μm to 20 μm.

FIG. 2 is a diagram showing the relationship between the amount of ZnO in NiZn-based ferrite and the Curie temperature Tc. The Curie temperature Tc decreased as the amount of ZnO increased, and the temperature was less than 160 ° C. in Comparative Example 5 to Comparative Example 8 in which ZnO exceeded 30.10 mol%.

3 and 4 are diagrams showing the relationship between the amount of Fe ₂ O ₃ and the rate of change Δμmax and Δμmin of the complex relative permeability μ. The rate of change Δμ _max of the complex relative permeability μ increased sharply when the amount of Fe ₂ O ₃ exceeded 48.60 mol%. Further, the rate of change Δμ _min of the complex relative permeability μ tended to increase gradually with respect to the amount of Fe ₂ O ₃ . Further, in Comparative Example 5 to Comparative Example 8 in which the Curie temperature Tc is less than 160 ° C., the temperature at which the complex relative magnetic permeability is μ _min is 150 ° C., which is 150 ° C., while the other evaluation samples are −40 ° C. The rate Δμ _min increased significantly.

FIG. 1 is a diagram showing the relationship between the total amount of Fe ₂ O ₃ and Zn O of NiZn-based ferrite and the complex relative permeability μ. As the total amount of Fe ₂ O ₃ and Zn O increased, the complex relative permeability μ also increased.

Examples 1 to 4 and Comparative Examples 22 to 27
Fe ₂ O ₃ powder, ZnO powder, CuO powder, NiO powder, Mn ₃ O ₄ powder, CaCO ₃ powder, and SiO ₂ powder, which are weighed so as to obtain NiZn-based ferrite having the composition shown in Table 2, are used as raw materials. Fe ₂ O ₃ powder, ZnO powder, CuO powder, and NiO powder were 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 Mn ₃ O ₄ powder, CaCO ₃ powder, SiO ₂ powder, and ion-exchanged water, and pulverized with an attritor to obtain a slurry. A part of the obtained slurry was dried and the average pulverized particle size was evaluated by an air permeation method. The average pulverized grain size was in the range of 1.7 μm to 1.9 μm. Polyvinyl alcohol was added as a binder to the remaining slurry, granulated by drying with a spray dryer, and pressure-molded to obtain each annular molded product.

Each molded body was sintered at a temperature of 1100 ° C. and a holding time of 2 hours to obtain annular NiZn-based ferrite sintered bodies having an outer diameter of 30 mm, an inner diameter of 20 mm, and a thickness of 8 mm. The firing atmosphere is in the atmosphere.

The density ds, the complex relative permeability μ, the Curie temperature Tc, and the rate of change Δμ _min and Δμ _max of the complex relative permeability μ of each NiZn-based ferrite sintered body were measured or calculated by the above method. The results obtained are shown in Table 3. In Table 3, Fe, Zn, Ni, and Cu are the main components, while Mn ₃ O ₄ , CaO, and SiO ₂ are shown as sub-components.

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

As the amount of CaO increases, the absolute values of the complex relative permeability change rate Δμ _min and Δμ _max become smaller, and in Examples 1 to 5 in the range of 0.025 mass or more and 0.250 part by mass or less, the change rate Δμ _min . The absolute value of is 20% or less, the absolute value of Δμ _max is 5% or less, and the rate of change of the complex relative magnetic permeability with respect to temperature is greatly reduced. On the other hand, in Comparative Examples 22 and 24 to 26 in which CaO was 0.010 parts by mass or less, the rate of change was large in _Δμmin and _Δμmax , and in Comparative Example 23 in which CaO was 0.019 parts by mass, the rate of change was _Δμmin and _Δμmax . Although it was improved, the rate of change _exceeded 20%. Further, in Comparative Examples 22 and 24 in which the amount of Mn ₃ O ₄ exceeds 0.250 parts by mass and Comparative Example 26 in which the amount of SiO ₂ exceeds 0.050 parts by mass, the rate of change _Δμmin and _Δμmax are large, and Comparative Examples 25 and 26. The Curie temperature Tc was less than 165 ° C.

As described above, Zn of 47.50 mol% or more and 48.60 mol% or less in terms of Fe ₂ O ₃ , 29.00 mol% or more and 30.10 mol% or less in terms of ZnO, and 5.50 mol% or more and 6.50 mol in terms of CuO. % Or less Cu, consisting of 14.80 mol% or more and 18.00 mol% or less of Ni in terms of NiO, and the total amount of Fe ₂ O ₃ , ZnO, NiO and CuO is 100 mol%, and Fe, Zn, Ni and Cu When the total amount of Fe ₂ O ₃ , ZnO, NiO, and CuO is 100 parts by mass, Mn is 0.250 parts by mass or less in Mn ₃ O ₄ conversion, and Ca is 0.025 parts by mass or more in CaO conversion. By using NiZn-based ferrite having 0.250 parts by mass or less and Si of 0.050 parts by mass or less in terms of SiO ₂ , the Curie temperature Tc is high, and the rate of change of the complex specific magnetic permeability μ with respect to temperature is _Δμmin , Δμ. NiZn-based ferrite having a small _max can be used. In addition, it is excellent in productivity because it does not need to have a complicated organizational structure.

10 Electronic components 21 First magnetic core 22 Second magnetic core 30 Winding (conductor)
31, 32.33 terminals

Claims (2)

Fe ₂ O ₃ equivalent 47.50 mol% or more and 48.60 mol% or less Fe, ZnO equivalent 29.00 mol% or more and 30.10 mol% or less Zn, CuO equivalent 5.50 mol% or more and 6.50 mol% or less Cu , Consists of 14.80 mol% or more and 18.00 mol% or less of Ni in terms of NiO, and the total amount of Fe ₂ O ₃ , ZnO, NiO and CuO is 100 mol%, and the total amount of Fe, Zn, Ni and Cu is calculated. When 100 parts by mass of Fe ₂ O ₃ , ZnO, NiO, and CuO are converted, respectively,
NiZn-based Mn is 0.250 parts by mass or less in terms of Mn ₃ O ₄ , Ca is 0.025 parts by mass or more and 0.250 parts by mass or less in CaO conversion, and Si is 0.050 parts by mass or less in terms of SiO ₂ . Ferrite. The NiZn-based ferrite according to claim 1.
The Curie temperature Tc is 165 ° C. or higher, and the complex relative permeability μ ₂₅ is 650 or higher.
The rate of change Δμ _max of the complex relative permeability μ _max with respect to the complex relative permeability μ ₂₅ is 5% or less in absolute value.
A NiZn-based ferrite having a change rate _Δμmin of the complex relative permeability μ _min with respect to the complex relative permeability μ ₂₅ of 20% or less in absolute value.
However, the complex relative permeability μ _max is the highest complex relative permeability μ between -40 ° C and 150 ° C under the condition of a frequency of 100 kHz, and the complex relative permeability μ _min is -40 ° C to 150 ° C. The complex relative permeability μ is the lowest under the condition of a frequency of 100 kHz.
Further, the rate of change Δμ _max = (μ _max −μ ₂₅ ) / μ ₂₅ × 100 (%), and the rate of change Δμ _min = ( _μmin −μ ₂₅ ) / μ ₂₅ × 100 (%). Further, the complex relative magnetic permeability μ ₂₅ is a complex relative magnetic permeability μ at a frequency of 100 kHz and a temperature of 25 ° C.

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