MnZn ferrite

Abstract

To provide a high magnetic permeability MnZn-based ferrite for a noise filter in which high frequency impedance and ΔB=Bm-Br are improved while maintaining high initial magnetic permeability by adding Nb2O5, V2O5, and Li2CO3 to the MnZn-based ferrite at the same time.SOLUTION: The basic components of Fe2O3: 51.00 to 54.00 mol%, ZnO: 15.00 to 21.00 mol% are set as the balance MnO, and as an additive component, Si is 50 to 150 mass ppm in SiO2 conversion, and Ca is 250 to 1100 mass ppm in CaCO3 conversion, and furthermore, Nb is 50 to 500 mass ppm in Nb2O5 conversion, and / or V is 100 to 700 mass ppm in V2O5 conversion, and Li is 200 to 600 mass ppm in Li2CO3 conversion (however, 200 mass ppm is not included), and the maximum impedance of 500 k to 3 MHz is 40 Ω mm-1 or more, and ΔB=Bm-Br at 100°C is 250 mT or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to MnZn-based ferrite, which is widely used in noise suppression components such as switching power supplies, and more specifically to a high-permeability MnZn-based ferrite for noise filters in which the magnetic saturation characteristics and high-frequency characteristics of the magnetic material have been improved. [Background technology]

[0002] MnZn ferrite, a representative soft magnetic material, is widely used in power transformers and noise suppression components in switching power supplies. In particular, MnZn ferrite used as a noise suppression component requires high magnetic permeability and is used as a common-mode choke in all kinds of electronic devices such as air conditioners, televisions, and personal computers, playing a role in removing unwanted electrical components (noise).

[0003] In recent years, with the increasing electrification of vehicles, demand for MnZn-based ferrites has been growing in the automotive electronics field. In automotive applications, the ambient temperature around the engine compartment ranges from -40°C to 150°C. Therefore, a common-mode choke that exhibits stable characteristics across this entire temperature range is required.

[0004] Currently available MnZn ferrites, even those boasting high permeability, have a saturation magnetic flux density of approximately 440 mT at room temperature and 250 mT at 100°C. Furthermore, the difference between the saturation magnetic flux density Bm and the residual magnetic flux density Br at 100°C, ΔB, is at most around 190 mT, meaning that losses increase significantly at high temperatures. Consequently, noise filter components using such MnZn ferrites generate heat in their operating environments. Therefore, when used as a noise filter, the value of ΔB needs to be high enough to ensure stable operation even at high temperatures, taking into account its effect on pulse noise emitted by inverters, compressors, etc. For example, it needs to be 250mT or higher at 100°C.

[0005] Furthermore, in order to function as a common-mode choke for noise filtering, a normalized impedance that is sufficiently larger than the noise at the frequency of the noise to be removed is required. In recent years, power semiconductors such as silicon carbide (SiC) and gallium nitride (GaN) have begun to be introduced as in-vehicle semiconductors for electric vehicles. However, these power semiconductors generate significant noise in the high-frequency band above 1 MHz. Therefore, when used with such power semiconductors, a common-mode choke with a high normalized impedance that can remove high-frequency noise is necessary.

[0006] MnZn ferrites are inexpensive compared to amorphous metals, making them easy to introduce as noise filters, but Fe 2+ Because of its high Fe content, 3+ -Fe 2+ Because electrons are easily transferred between the elements, the resistivity is low, on the order of 0.1 Ω·m. With such low resistivity, as the frequency band used increases, losses due to eddy currents within the ferrite increase sharply, and the initial permeability decreases. Consequently, the inductance decreases, and at the same time, the maximum value of the normalized impedance decreases and the frequency at which the maximum value occurs decreases. Therefore, in order to obtain a high normalized impedance on the order of MHz, the resistivity must be 10 5 Either use NiZn-based ferrites with a relatively high Ω·m or higher among ferrites, or use MnZn-based ferrites with Fe 2+ It is necessary to reduce the amount of [the substance] to increase the resistivity.

[0007] However, in the case of NiZn ferrite, the initial permeability at low frequencies is low, around several hundred, making it unsuitable for common-mode chokes. On the other hand, in the case of MnZn ferrite, the Fe of the ferrite... 2+ Reducing it has the problem of decreasing the magnetic moment and thus lowering the saturation magnetic flux density.

[0008] As another method for increasing the specific resistance, there is a measure of adding a trace amount of metal oxide. This is because metal oxides other than the main component do not exhibit conductivity and segregate at grain boundaries in the crystal structure. Therefore, the grain boundary resistance increases, resulting in an increase in the specific resistance of the ferrite body.

[0009] However, when a trace amount of metal oxide is added to increase the specific resistance in order to improve the normalized impedance and ΔB at high frequencies as described above, there is generally a problem that the initial permeability at low frequencies around 10 kHz decreases. Note that the normalized impedance in this specification is a value obtained by normalizing the measured impedance with the dimensions and the number of turns of the coil.

[0010] Here, Patent Document 1 and Patent Document 2 show that the addition of Nb2O5 and V2O5 can reduce the residual magnetic flux density and improve ΔB. In addition, Patent Document 3 and Patent Document 4 disclose MnZn ferrites containing Nb, V, and Li, which are effective in improving the normalized impedance and ΔB at high frequencies.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0012] As described above, it has been shown that the addition of Nb2O5 and V2O5 can reduce the residual magnetic flux density and improve ΔB. However, the inventions described in Patent Documents 1 and 2 are applied to MnZn-based ferrites used as magnetic cores for power transformers, and do not mention initial permeability as a high-permeability material. Generally, when additives are added to increase resistivity, the initial permeability at low frequencies of around 10 kHz decreases, so adding only Nb2O5 and V2O5 does not ensure sufficient initial permeability and makes it unsuitable as a ferrite for noise suppression.

[0013] Furthermore, neither of the inventions described in Patent Documents 3 and 4 is intended to improve ΔB and normalized impedance.

[0014] Therefore, in order to use MnZn ferrite as a common-mode choke, high initial permeability is required. However, conventional technology has not solved the problem of improving the normalized impedance and ΔB in the high-frequency band while suppressing the decrease in initial permeability in the low-frequency band.

[0015] The present invention was developed in view of the above circumstances, and aims to provide a MnZn-based ferrite for noise suppression that has high noise rejection capability in the 10kHz to 3MHz range by preventing a decrease in initial permeability in the frequency band of approximately 10 to 150kHz, having a large ΔB even at high temperatures such as 100°C and being less prone to saturation, and by increasing the maximum value of the normalized impedance in the high frequency band of 500kHz to 3MHz. [Means for solving the problem]

[0016] In other words, the gist of the present invention is as follows: 1. A MnZn ferrite composed of a main component and a sub-component, wherein the main component contains iron: 51.00 to 54.00 mol% in terms of Fe2O3, zinc: 15.00 to 21.00 mol% in terms of ZnO, and manganese: the balance; and the sub-component contains Si: 50 to 150 mass ppm in terms of SiO2, Ca: 250 to 1100 mass ppm in terms of CaCO3, Nb: 50 to 500 mass ppm in terms of Nb2O5, and Li: more than 200 mass ppm and 600 mass ppm or less in terms of Li2CO3.

[0017] 2. A MnZn ferrite composed of a main component and a sub-component, wherein the main component contains iron: 51.00 to 54.00 mol% in terms of Fe2O3, zinc: 15.00 to 21.00 mol% in terms of ZnO, and manganese: the balance; and the sub-component contains Si: 50 to 150 mass ppm in terms of SiO2, Ca: 250 to 1100 mass ppm in terms of CaCO3, V: 100 to 700 mass ppm in terms of V2O5, and Li: more than 200 mass ppm and 600 mass ppm or less in terms of Li2CO3.

[0018] 3. A MnZn ferrite composed of a main component and a sub-component, wherein the main component contains iron: 51.00 to 54.00 mol% in terms of Fe2O3, zinc: 15.00 to 21.00 mol% in terms of ZnO, and manganese: the balance; and the sub-component contains Si: 50 to 150 mass ppm in terms of SiO2, Ca: 250 to 1100 mass ppm in terms of CaCO3, Nb: 50 to 500 mass ppm in terms of Nb2O5, V: 100 to 700 mass ppm in terms of V2O5, and Li: more than 200 mass ppm and 600 mass ppm or less in terms of Li2CO3.

[0019] 4. The MnZn ferrite according to any one of items 1 to 3 above, wherein the value of ΔB [mT] obtained by the following formula (1) is 250 mT or more at 100 °C. ΔB = B m - B r ··· (Formula (1)) (However, B m is the saturation magnetic flux density [mT], Br (This is the remanent magnetic flux density [mT])

[0020] 5. In the frequency range of 500kHz to 3MHz, the normalized impedance Z can be calculated using the following equations (2) and (3). norm [Ω·mm -1 The maximum value of ] is 40Ω·mm -1 The above-mentioned MnZn ferrite according to any one of items 1 to 4 above. Z norm =Z·c1 / N 2 ...Equation (2) c1=l e / A e ...Equation (3) (Z is impedance [Ω], c1 is core constant [mm]) -1 ], l e The magnetic path length is [mm], A e is the cross-sectional area [mm²] 2 ], where N is the number of turns in the coil [-])

[0021] A MnZn-based ferrite according to any one of items 1 to 5 above, wherein the μi' (real part of the initial permeability μi) at 6.10 kHz and 23°C is 4000 or more, and the μi' (real part of the initial permeability μi) at 500 kHz and 23°C is 4500 or more.

[0022] 7. Sintering density is 4.97 g / cm³ 3 The above-mentioned MnZn ferrite according to any one of items 1 to 6 above. [Effects of the Invention]

[0023] According to the present invention, a high-permeability MnZn ferrite can be obtained that has a large ΔB=Bm-Br at high temperatures such as 100°C and a high normalized impedance value in the high-frequency band, and can be used as a common-mode choke that can handle high temperatures and high frequencies. [Modes for carrying out the invention]

[0024] The present invention will be described in detail below. As described above, the MnZn-based ferrite of the present invention has oxides of Fe, Zn, and Mn as its basic components. The following mol%s represent the composition ratios of the basic components.

[0025] In this invention, the material contains 51.00 to 54.00 mol% of iron in terms of Fe2O3. Below 51.00 mol% in terms of Fe2O3, the initial permeability at room temperature decreases. On the other hand, when it exceeds 54.00 mol% in terms of Fe2O3, the initial permeability at room temperature decreases, and the loss component increases, resulting in a relative loss coefficient tanδ / μ i This is because the concentration would become too large. Preferably, the range is 51.50 to 54.00 mol% in terms of Fe2O3. More preferably, the range is 52.00 to 53.90 mol% in terms of Fe2O3. Even more preferably, the range is 52.50 to 53.80 mol% in terms of Fe2O3. In addition, if Fe2O3 falls below the lower limit mentioned above, the Bm of the ferrite decreases, making it impossible to obtain a sufficient ΔB. On the other hand, if Fe2O3 exceeds the upper limit mentioned above, it leads to a decrease in the initial permeability of the ferrite, making it unsuitable for its intended high-permeability material applications.

[0026] In this invention, zinc is contained in an amount of 15.00 to 21.00 mol% in terms of ZnO. If the amount of ZnO falls below the lower limit, the resistivity of the ferrite decreases, resulting in poor high-frequency characteristics. On the other hand, if the amount of ZnO exceeds the upper limit, the Bm of the ferrite decreases, and a sufficient ΔB cannot be obtained. The preferred range for ZnO is more than 15.00 mol% and 21.00 mol% or less in terms of ZnO. More preferably, it is 16.00 to 20.00 mol% in terms of ZnO. Even more preferably, it is 17.00 to 20.00 mol% in terms of ZnO.

[0027] In this invention, the remainder is made of Mn because a sufficient initial permeability cannot be obtained if Ni is used. The preferred range for MnO is 23.00 to 30.00 mol%, more preferably 25.00 mol% or more and less than 30.00 mol%, even more preferably 25.00 to 29.50 mol%, and even more preferably 26.00 to 29.40 mol%.

[0028] Next, we will explain the minor components. Si:50-150 ppm by mass in terms of SiO2, Ca:250-1100 ppm by mass in terms of CaCO3 Both SiO2 and CaCO3 segregate at grain boundaries within the crystal structure, improving grain boundary resistance. This, in turn, improves initial permeability and normalized impedance in the high-frequency range. If the amount is less than the lower limit, the initial permeability of ferrite at high frequencies drops sharply, which is unfavorable for high-frequency characteristics. On the other hand, if the amount is more than the upper limit, the initial permeability of ferrite at low frequencies is significantly reduced. Therefore, the above range is appropriate for all components. The preferred addition range for silicon is 55 to 120 ppm by mass in terms of SiO2. The preferred addition range for calcium is 350 to 1080 ppm by mass in terms of CaCO3, more preferably 500 to 1050 ppm by mass in terms of CaCO3.

[0029] Nb:500 ppm by mass (based on Nb2O5 equivalent) Niobium oxide (Nb2O5) segregates at the grain boundaries and binds with Ca, remaining within the grain. 2+ By attracting these particles to the grain boundaries, the grain boundaries are made more resistive, reducing eddy current losses. This allows for a higher normalized impedance in the high-frequency band, which is thought to have the effect of reducing residual magnetic flux density. The reason the Nb2O5 addition range in this invention is set to 50 to 500 ppm by mass is that if it is below this range, the aforementioned effects cannot be fully obtained, while exceeding this range causes abnormal grain growth, leading to a decrease in the resistivity and initial permeability of the ferrite. The preferred addition range for niobium is 60 to 400 ppm by mass in terms of Nb2O5. More preferably, it is in the range of 70 to 350 ppm by mass in terms of Nb2O5, and even more preferably, in the range of 200 to 300 ppm by mass in terms of Nb2O5.

[0030] V:V2O5 equivalent: 100-700 ppm by mass Vanadium oxide (V2O5) has a relatively low melting point and promotes crystal densification by forming a liquid phase during firing, thereby improving sintering density and increasing saturation magnetic flux density. Furthermore, like Nb2O5, V2O5 forms Ca-V bonds near grain boundaries. 2+ It is believed that segregation at grain boundaries leads to increased ferrite resistance, improved normalized impedance in the high-frequency band due to reduced eddy current losses, and a reduction in residual magnetic flux density. Furthermore, V2O5 has a greater effect on reducing residual magnetic flux density than Nb2O5. In addition, since liquid-phase sintering reduces strain near grain boundaries, it is thought that grain boundary stress is reduced and residual magnetic flux density is reduced. In this invention, the V2O5 addition range is set to 100 to 700 ppm by mass because, if it is less than 100 ppm by mass, the above effect cannot be sufficiently obtained, while if it exceeds 700 ppm by mass, the resistivity of the ferrite increases and its initial permeability decreases significantly. The preferred addition range for vanadium is 150 to 600 ppm by mass in terms of V2O5. More preferably, it is in the range of 180 to 550 ppm by mass in terms of V2O5, and even more preferably, in the range of 300 to 500 ppm by mass in terms of V2O5.

[0031] Li: Li2CO3 equivalent: over 200 ppm by mass, and 600 ppm or less by mass. Lithium usually exists in the form of an oxide, and lithium oxide, like the other additives mentioned above, has the effect of improving the resistivity of ferrite. Furthermore, lithium oxide affects the temperature characteristics of the initial magnetic permeability. The initial permeability of MnZn ferrite generally peaks just below the Curie temperature, the temperature at which magnetism disappears, and this is called the primary peak. In addition, the initial permeability of MnZn ferrite also has a peak that appears at a temperature lower than the Curie temperature where the crystal magnetic anisotropy constant K1 becomes 0, and this peak is called the secondary peak. When lithium oxide is added, this secondary peak shifts to the higher temperature side.

[0032] Generally, for high-permeability materials, a composition is selected in which a secondary peak appears around room temperature (around 25°C). However, in this invention, by deliberately shifting the secondary peak to a lower temperature of about 10-15°C and then adding Li2CO3 to adjust it, the secondary peak is shifted to around room temperature (around 25°C). By shifting the secondary peak in this way, this invention makes it possible to improve the resistivity of ferrite while maintaining its high permeability, thereby improving its high-frequency characteristics and reducing its residual magnetic flux density.

[0033] As mentioned above, the secondary peak shifts to the higher temperature side with each addition of lithium, so the amount of lithium must be adjusted according to the temperature of the secondary peak before lithium addition. Specifically, the secondary peak shift is insufficient at concentrations below 200 ppm by mass, while concentrations above 600 ppm by mass cause the secondary peak to shift significantly to the higher temperature side, thus not contributing to the improvement of the initial permeability. Therefore, the above range was chosen. The preferred lithium addition range is 220 to 580 ppm by mass in terms of Li2CO3. More preferably, it is in the range of 250 to 550 ppm by mass in terms of Li2CO3, and even more preferably, in the range of 300 to 500 ppm by mass in terms of Li2CO3.

[0034] It is believed that the synergistic effect of adding at least two, or even all three, of these Nb, V, and Li oxides made it possible to achieve high initial permeability, high ΔB, and high normalized impedance in the high-frequency band for the ferrite.

[0035] In this invention, the value of ΔB[mT], calculated by the following equation (1), is set to 250mT or more at 100°C. This is because, in the case of high-permeability MnZn ferrite materials (μi of 4,000 or more), the saturation magnetic flux density is low and magnetic saturation is likely to occur at high temperatures such as 100°C. The preferred upper limit for such a value of ΔB[mT] is approximately 320mT at 100°C. Here, conventionally, the saturation magnetic flux density at 100°C is about 250 mT, so ΔB is about 190 mT. ΔB = B m -Br ...Equation (1) (However, B m is the saturation magnetic flux density [mT], B r (This is the remanent magnetic flux density [mT])

[0036] The present invention relates to the normalized impedance Z, which can be determined by the following equations (2) and (3) in the frequency range of 500 kHz to 3 MHz. norm [Ω·mm -1 The maximum value occurring around 1MHz is 40Ω·mm -1 This concludes the explanation. This is to remove noise around 1MHz. The preferred upper limit for this maximum value is 65Ω·mm. -1 It is to that extent. Here, conventionally, in the case of high-permeability materials, the inductance at high frequencies is low, so the normalized impedance Z norm It is 30 [Ω·mm -1 It is to that extent. Z norm =Z·c1 / N 2 ...Equation (2) c1=l e / A e ...Equation (3) (Z is impedance [Ω], c1 is core constant [mm]) -1 ], l e The magnetic path length is [mm], A e is the cross-sectional area [mm²] 2 ], where N is the number of turns in the coil [-])

[0037] In this invention, it is preferable that the μi' (real part of the initial permeability μi) at 10 kHz and 23°C is 4000 or more, and the μi' (real part of the initial permeability μi) at 500 kHz and 23°C is 4500 or more. The preferred upper limit for the μi' (real part of the initial permeability μi) at 10 kHz and 23°C is approximately 6500, and the preferred upper limit for the μi' (real part of the initial permeability μi) at 500 kHz and 23°C is also approximately 6500.

[0038] Regarding sintering density, the MnZn-based ferrite of the present invention has a density of 4.97 g / cm³. 3 The above is desirable. Meeting these conditions will result in a saturation magnetic flux density of 4.97 g / cm². 3This is because it is an improvement compared to the case of a sintering density of less than 5.10 g / cm³, and contributes to an improvement in ΔB. The preferred upper limit is 5.10 g / cm³. 3 It is to that extent.

[0039] To achieve the required sintering density, firing at a high temperature of 1370°C or higher is desirable. Furthermore, longer firing times are preferable as they result in higher sintering density. However, excessively long firing times improve properties but decrease productivity, so a practical upper limit is around 12 hours. Also, excessively high firing temperatures increase the evaporation of Zn, significantly affecting compositional variation; therefore, a maximum of around 1450°C is preferable. Additionally, while longer firing times and higher temperatures lead to larger grain growth and higher initial permeability, they also increase the flow of eddy currents within the grains, leading to increased eddy current losses and decreased initial permeability and normalized impedance at high frequencies. Therefore, a temperature of 1370-1385°C and a firing time of 2-4 hours are considered more preferable firing conditions.

[0040] Furthermore, unless otherwise specified in this specification, conventional methods can be used for producing the MnZn-based ferrites used in this invention. [Examples]

[0041] [Example 1] When the iron, zinc, and manganese contained in the raw materials are all converted to Fe2O3, ZnO, and MnO, the ratio of Fe2O3, ZnO, and MnO is 53.44:17.09:27.47 mol%. The raw material powder was weighed and mixed for 16 hours using a wet ball mill, and then calcined in air at 925°C for 3 hours. Next, silicon dioxide, calcium oxide, niobium oxide, and lithium oxide were added to this calcined powder in the ratios shown in Table 1, converted to SiO2, CaCO3, Nb2O5, and Li2CO3, respectively, and the mixture was ground for 16 hours using a wet ball mill. After this grinding, polyvinyl alcohol (PVA) was added to the dried powder, and it was granulated by sieving to obtain granulated powder. The granulated powder was then molded into a toroidal shape to form a molded body. This molded body was then introduced into a batch-type firing furnace and fired at a maximum temperature of 1370°C for 2 hours in a gas stream of appropriately mixed nitrogen gas and air to produce a sintered toroidal core with an outer diameter of 30 mm, an inner diameter of 19 mm, and a height of 6 mm.

[0042] The resulting toroidal core was subjected to a sintering density calculation at 23°C using the Archimedes method, and its resistivity was measured using the four-terminal method. Next, copper wire is wound 10 times around the toroidal core, and the inductance L and quality factor Q are measured using an LCR meter (Keysight 4980A) in the range of -20 to 200°C at 10 kHz. The Curie temperature T is then calculated from the initial permeability based on these values. C The following was calculated. In addition, the inductance L and quality factor Q at 1k to 30MHz at 23℃ were measured, and the normalized impedance Z·c1 / N was calculated based on these values ​​using the initial permeability and core constant. 2 The result was calculated. Furthermore, copper wire with 40 turns on the primary side and 20 turns on the secondary side was wound around the above-mentioned toroidal core, and the saturation magnetic flux density and remanent magnetic flux density were measured using a DC magnetization characteristic test apparatus with a maximum magnetization force H of 1200 A / m. ΔB was calculated as the difference between the saturation magnetic flux density and the remanent magnetic flux density. The results of the investigation into the effects of trace amounts of additives are shown in Table 1.

[0043] [Table 1]

[0044] As shown in the examples in Table 1, when trace amounts of additives are added in combinations such as Nb2O5 and Li2CO3, V2O5 and Li2CO3, the initial permeability improves compared to the case without additives due to the effect of Li2CO3, and the maximum normalized impedance is 40 Ω·mm. -1 The results were as described above. Furthermore, a ΔB of 250 mT or more was obtained at 100°C.

[0045] [Example 2] The raw material powders were weighed, mixed, and calcined as shown in Table 2. To the calcined powder, silicon dioxide and calcium oxide were added in the ratios shown in Table 2 (converted to SiO2 and CaCO3), and niobium oxide, vanadium oxide, and lithium oxide were added at 300, 500, and 300 ppm by mass (converted to Nb2O5, V2O5, and Li2CO3), respectively. Then, the materials were crushed, granulated, and molded in the same manner as in Example 1. The molded bodies were introduced into a batch-type firing furnace and fired at a maximum temperature of 1370°C for 2 hours to obtain a sintered toroidal core similar to that in Example 1.

[0046] The obtained toroidal core was measured for the same parameters using the same method and procedure as in Example 1. Table 2 shows the results of examples in which the effects of Nb2O5, V2O5, and Li2CO3 were investigated by varying the basic composition and the amounts of SiO2 and CaCO3 added. In Comparative Examples 11 and 12, Nb2O5, V2O5, and Li2CO3 were not added.

[0047] [Table 2]

[0048] As shown in Table 2, even when the basic composition and the amounts of SiO2 and CaCO3 added are changed, the addition of Nb2O5, V2O5, and Li2CO3 results in improvements to initial permeability, saturation magnetic flux density, ΔB, and normalized impedance at high frequencies, similar to the results of Example 1.

Claims

1. A MnZn-based ferrite consisting of a basic component and a minor component, The above basic components are: Iron: Fe ２ O ３ Converted to 51.00-54.00 mol%, Zinc: 15.00 to 21.00 mol% in terms of ZnO and Manganese: Remaining It consists of, As the above minor components, Si:SiO ２ Converted to 50-150 ppm by mass, Ca: CaCO ３ Converted to 250-1100 ppm by mass, Nb: Nb ２ O ５ Converted to 50 to 500 ppm by mass and Li:Li ２ CO ３ Converted to more than 200 mass ppm and 600 mass ppm or less A MnZn-based ferrite composed of these elements.

2. A MnZn-based ferrite consisting of a basic component and a minor component, The above basic components are: Iron: Fe ２ O ３ in terms of conversion, 51.00 to 54.00 mol%, Zinc: 15.00 to 21.00 mol% in terms of ZnO and Manganese: Remaining It consists of, As the above minor components, Si:SiO ２ Converted to 50-150 ppm by mass, Ca: CaCO ３ Converted to 250-1100 ppm by mass, V:V ２ O ５ Converted to 100-700 ppm by mass and Li:Li ２ CO ３ Converted to more than 200 mass ppm and 600 mass ppm or less A MnZn-based ferrite composed of these elements.

3. A MnZn-based ferrite consisting of a basic component and a minor component, The above basic components are: Iron: Fe ２ O ３ Converted to 51.00-54.00 mol%, Zinc: 15.00 to 21.00 mol% in terms of ZnO and Manganese: Remaining It consists of, As the above minor components, Si:SiO ２ Converted to 50-150 ppm by mass, Ca: CaCO ３ Converted to 250-1100 ppm by mass, Nb: Nb ２ O ５ Converted to 50-500 ppm by mass, V:V ２ O ５ Converted to 100-700 ppm by mass and Li:Li ２ CO ３ Converted to more than 200 mass ppm and 600 mass ppm or less A MnZn-based ferrite composed of these elements.

4. The MnZn ferrite according to any one of claims 1 to 3, wherein the value of ΔB [mT] obtained by the following equation (1) is 250 mT or more at 100°C. ΔB = B ｍ -B ｒ ...(1) formula (However, B ｍ is the saturation magnetic flux density [mT], B ｒ (This is the remanent magnetic flux density [mT])

5. In the frequency range of 500 kHz to 3 MHz, the normalized impedance Z can be calculated using the following equations (2) and (3). norm [Ω・mm －１ The maximum value of ] is 40Ω·mm －１ The MnZn ferrite according to any one of claims 1 to 4. Z norm = Z·c １ / N ２ ・・・ (Equation (2)) c １ =l ｅ / A ｅ ... (3) (Z is impedance [Ω], c １ The core constant [mm －１ ], l ｅ The magnetic path length is [mm], A ｅ is the cross-sectional area [mm²] ２ ], where N is the number of turns in the coil [-])

6. The MnZn ferrite according to any one of claims 1 to 5, wherein the μi' (real part of the initial permeability μi) at 10 kHz and 23°C is 4000 or more, and the μi' (real part of the initial permeability μi) at 500 kHz and 23°C is 4500 or more.

7. Sintering density is 4.97 g / cm³ ３ The MnZn ferrite according to any one of claims 1 to 6.

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