MnZn-BASED 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 ferrites that are widely used in noise suppression components for switching power supplies and the like, and more particularly to high-permeability MnZn-based ferrites for noise filters that have improved magnetic saturation characteristics and high-frequency characteristics of the magnetic material. [Background technology]

[0002] MnZn ferrite, a representative soft magnetic material, is widely used in power transformers for switching power supplies and noise suppression components. MnZn ferrite used in noise suppression components is required to have high magnetic permeability, and is used as a common mode choke that removes unwanted electrical components (noise) in all electronic devices such as air conditioners, televisions, and computers.

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

[0004] Although currently commercially available MnZn ferrites have high magnetic permeability, their saturation magnetic flux density is only about 440 mT at room temperature and 250 mT at 100°C. Furthermore, ΔB, the difference between the saturation magnetic flux density Bm and the residual magnetic flux density Br at 100°C, is at most about 190 mT, resulting in significant loss at high temperatures. Therefore, noise filter components that use such MnZn ferrites generate heat in their operating environments. Therefore, when used as a noise filter, the ΔB value needs to be high enough to ensure stable use even at high temperatures, taking into account the effect on pulse noise emitted by inverters, compressors, etc.; for example, it needs to be 250 mT or more at 100°C.

[0005] Furthermore, in order to function as a common mode choke for a noise filter, it needs to have a normalized impedance that is sufficiently larger than the noise at the frequency of the noise to be removed. 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, but these power semiconductors generate large amounts of 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 eliminate noise in the high-frequency band is required.

[0006] MnZn ferrite is inexpensive compared to amorphous metals, making it easy to introduce as a noise filter. 2+ Because of the high content of Fe 3+ -Fe 2+ Because electrons are easily exchanged between the ferrite and the material, 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 in the ferrite increase sharply, causing the initial permeability to decrease. This reduces the inductance, and at the same time, this reduces the maximum value of the normalized impedance and causes the frequency at which the maximum value is reached to decrease. Therefore, to obtain a high normalized impedance in the MHz order, the resistivity must be 10 5 NiZn ferrite, which has a relatively high resistance of Ω·m or more among ferrites, is used, or Fe in MnZn ferrite is used. 2+ It is necessary to reduce the amount of and increase the resistivity.

[0007] However, NiZn ferrite has a low initial permeability of only a few hundred at low frequencies, making it unsuitable for common mode chokes. On the other hand, MnZn ferrite has a low initial permeability of only a few hundred at low frequencies, making it unsuitable for common mode chokes. 2+ If the value is reduced, the magnetic moment decreases, resulting in a problem of a decrease in the saturation magnetic flux density.

[0008] Another method for increasing resistivity is to add a small amount of metal oxide. This is because metal oxides other than the main component do not exhibit conductivity and segregate at the grain boundaries in the crystalline structure. This increases the grain boundary resistance, which in turn increases the resistivity of the ferrite itself.

[0009] However, when a small amount of metal oxide is added to increase the resistivity in order to improve the normalized impedance or ΔB at high frequencies, there is a problem that the initial permeability at low frequencies, generally around 10 kHz, decreases. In this specification, the normalized impedance is a value obtained by normalizing the actually measured impedance with respect to the dimensions and the number of turns of the coil.

[0010] Here, Patent Documents 1 and 2 show that the addition of Nb2O5 and V2O5 reduces the residual magnetic flux density and improves ΔB. Furthermore, Patent Documents 3 and 4 disclose MnZn-based ferrites containing Nb, V, and Li, which are effective in improving high-frequency normalized impedance and ΔB. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 6-140231 [Patent Document 2] Japanese Patent Application Publication No. 6-283320 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-080344 [Patent Document 4] Japanese Patent Application Laid-Open No. 2001-342058 Summary of the Invention [Problem to be solved by the invention]

[0012] As mentioned above, it has been shown that the addition of Nb2O5 and V2O5 has the effect of reducing the residual magnetic flux density and improving 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 the initial permeability as a high-permeability material. Generally, when an additive is 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 is therefore unsuitable as a ferrite for noise suppression.

[0013] Furthermore, neither of the inventions described in Patent Document 3 nor Patent Document 4 aims to improve ΔB and normalized impedance.

[0014] Therefore, in order to use MnZn ferrite as a common mode choke, it is necessary for it to have a high initial permeability, and conventional technology has not yet 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 has been developed in view of the above circumstances, and aims to provide an MnZn-based ferrite for noise suppression that has a large ΔB and is not easily saturated even at high temperatures such as 100°C, while preventing a decrease in initial permeability in a frequency band of about 10 to 150 kHz, and that has a high noise removal ability in the range of 10 kHz to 3 MHz by increasing the maximum value of normalized impedance in a high frequency band of 500 kHz to 3 MHz. [Means for solving the problem]

[0016] That is, the gist and configuration of the present invention are as follows. 1. An MnZn-based ferrite consisting of basic components and accessory components, wherein the basic components include iron: 51.00 to 54.00 mol% calculated as Fe2O3, zinc: 15.00 to 21.00 mol% calculated as ZnO, and manganese: the balance, and the accessory components include Si: 50 to 150 ppm by mass calculated as SiO2, Ca: 250 to 1100 ppm by mass calculated as CaCO3, Nb: 50 to 500 ppm by mass calculated as Nb2O5, and Li: more than 200 ppm by mass and 600 ppm by mass or less calculated as Li2CO3.

[0017] 2. An MnZn-based ferrite consisting of basic components and accessory components, wherein the basic components include iron: 51.00 to 54.00 mol% calculated as Fe2O3, zinc: 15.00 to 21.00 mol% calculated as ZnO, and manganese: the balance, and the accessory components include Si: 50 to 150 mass ppm calculated as SiO2, Ca: 250 to 1100 mass ppm calculated as CaCO3, V: 100 to 700 mass ppm calculated as V2O5, and Li: more than 200 mass ppm and not more than 600 mass ppm calculated as Li2CO3.

[0018] 3. An MnZn-based ferrite consisting of basic components and accessory components, wherein the basic components include iron: 51.00 to 54.00 mol% calculated as Fe2O3, zinc: 15.00 to 21.00 mol% calculated as ZnO, and manganese: the balance, and the accessory components include Si: 50 to 150 mass ppm calculated as SiO2, Ca: 250 to 1100 mass ppm calculated as CaCO3, Nb: 50 to 500 mass ppm calculated as Nb2O5, V: 100 to 700 mass ppm calculated as V2O5, and Li: more than 200 mass ppm and not more than 600 mass ppm calculated as Li2CO3.

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

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

[0021] 6. The MnZn-based ferrite according to any one of items 1 to 5, wherein μi' (the real part of the initial permeability μi) at 10 kHz and 23°C is 4000 or more, and μi' (the real part of the initial permeability μi) at 500 kHz and 23°C is 4500 or more.

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

[0023] According to the present invention, a high-permeability MnZn-based ferrite is 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 withstand high temperatures and high frequencies. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention will be described in detail below. As described above, the MnZn ferrite of the present invention is based on oxides of Fe, Zn, and Mn, and the mol% below indicates the composition ratio within the base components.

[0025] In the present invention, the iron content is 51.00 to 54.00 mol% calculated as Fe2O3. If the iron content is less than 51.00 mol% calculated as Fe2O3, the initial permeability at room temperature decreases. On the other hand, if the iron content exceeds 54.00 mol% calculated as Fe2O3, the initial permeability at room temperature decreases, the loss component increases, and the relative loss factor tanδ / μ i This is because the content becomes large. Preferably, it is in the range of 51.50 to 54.00 mol% in terms of Fe2O3. More preferably, it is in the range of 52.00 to 53.90 mol% in terms of Fe2O3. Still more preferably, it is in the range of 52.50 to 53.80 mol% in terms of Fe2O3. In addition, if the Fe2O3 content falls below the lower limit, the Bm of the ferrite decreases, making it impossible to obtain a sufficient ΔB. On the other hand, if the Fe2O3 content exceeds the upper limit, the initial permeability of the ferrite decreases, making it unsuitable for use as a high-permeability material.

[0026] In the present invention, zinc is contained in an amount of 15.00 to 21.00 mol% calculated as ZnO. If the ZnO content is less than the lower limit, the resistivity of the ferrite decreases, resulting in poor high-frequency characteristics. On the other hand, if the ZnO content exceeds the upper limit, the Bm of the ferrite decreases, making it impossible to obtain a sufficient ΔB. The preferred range of ZnO is more than 15.00 mol% and not more than 21.00 mol% calculated as ZnO. More preferably, it is 16.00 to 20.00 mol% calculated as ZnO. Even more preferably, it is 17.00 to 20.00 mol% calculated as ZnO.

[0027] In the present invention, the reason why the remainder is Mn is that sufficient initial permeability cannot be obtained with Ni. The preferred range of MnO is 23.00 to 30.00 mol%, more preferably 25.00 mol% or more but less than 30.00 mol%, even more preferably 25.00 to 29.50 mol%, and still more preferably 26.00 to 29.40 mol%.

[0028] Next, the secondary components will be described. Si: 50 to 150 mass ppm in SiO2 equivalent, Ca: 250 to 1100 mass ppm in CaCO3 equivalent Both SiO2 and CaCO3 segregate at grain boundaries in the crystalline structure, improving the resistance of the grain boundaries. This improves the initial permeability and normalized impedance in the high-frequency band. If the content is less than the lower limit, the initial permeability of the ferrite at high frequencies drops sharply, which is detrimental to high-frequency characteristics. On the other hand, if the content is greater than the upper limit, the initial permeability of the ferrite at low frequencies drops significantly. Therefore, the above-mentioned ranges are appropriate for each component. The preferred range for silicon addition is 55 to 120 mass ppm in terms of SiO2. The preferred range for calcium addition is 350 to 1080 mass ppm in terms of CaCO3, more preferably 500 to 1050 mass ppm in terms of CaCO3.

[0029] Nb: 50 to 500 mass ppm in terms of Nb2O5 Niobium oxide Nb2O5 segregates at the grain boundaries and binds with Ca, which remains within the grains. 2+ This is thought to have the effect of attracting the magnetic flux density to the grain boundaries, increasing the resistance of the grain boundaries and reducing eddy current loss, thereby maintaining a high normalized impedance in the high frequency band and reducing the residual magnetic flux density. The reason why the Nb2O5 content range in the present invention is set to 50 to 500 ppm by mass is that, if the content is below this range, the above-mentioned effects are not sufficiently obtained, while if the content exceeds this range, abnormal grain growth occurs, resulting in a decrease in the resistivity and initial permeability of the ferrite. The preferred range of niobium content is 60 to 400 ppm by mass, calculated as Nb2O5. A more preferred range is 70 to 350 ppm by mass, calculated as Nb2O5, and an even more preferred range is 200 to 300 ppm by mass, calculated as Nb2O5.

[0030] V: 100 to 700 mass ppm in terms of V2O5 Vanadium oxide V2O5 has a relatively low melting point and forms a liquid phase during firing, which promotes densification of the crystal, improves sintered density, and increases saturation magnetic flux density. In addition, V2O5, like Nb2O5, forms Ca-V bonds near the grain boundaries, resulting in Ca 2+ It is thought that the segregation of V2O5 at the grain boundaries increases the resistance of ferrite, reduces eddy current loss, improves normalized impedance in the high frequency band, and reduces residual magnetic flux density. Note that V2O5 has a greater effect on reducing residual magnetic flux density than Nb2O5. In addition, liquid phase sintering relieves strain near grain boundaries, which is thought to reduce grain boundary stress and remanence. In the present invention, the V2O5 content is set to 100 to 700 ppm by mass because, if the content is less than 100 ppm by mass, the above-mentioned effects are not fully achieved, while if the content exceeds 700 ppm by mass, the resistivity of the ferrite increases and its initial permeability drops significantly. The preferred range of vanadium content is 150 to 600 ppm by mass, calculated as V2O5. A more preferred range is 180 to 550 ppm by mass, calculated as V2O5, and an even more preferred range is 300 to 500 ppm by mass, calculated as V2O5.

[0031] Li: More than 200 mass ppm and 600 mass ppm or less in terms of Li2CO3 Lithium is usually present in the form of an oxide, and lithium oxide, like the other additives mentioned above, has the effect of improving the resistivity of ferrite. Lithium oxide also 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 is called the primary peak. The initial permeability of MnZn ferrite also has a peak that appears at a temperature lower than the Curie temperature, where the magnetocrystalline anisotropy constant K1 becomes 0. This peak is called the secondary peak, and adding lithium oxide shifts this secondary peak toward higher temperatures.

[0032] Generally, for high magnetic permeability materials, a composition is selected in which the secondary peak appears near room temperature (near 25°C), but in the present invention, a composition in which the secondary peak is intentionally shifted to a temperature approximately 10 to 15°C lower is added with Li2CO3 to adjust the secondary peak to near room temperature (near 25°C).By shifting the secondary peak in this way, the present invention can improve the resistivity of ferrite while maintaining its high magnetic permeability, thereby achieving effects such as improving its high-frequency characteristics and reducing its residual magnetic flux density.

[0033] As mentioned above, the secondary peak shifts toward higher temperatures with each addition of lithium, so the amount must be adjusted depending on the temperature of the secondary peak before lithium addition. Specifically, if the amount is 200 mass ppm or less, the secondary peak does not shift sufficiently, while if the amount is more than 600 mass ppm, the secondary peak shifts significantly toward higher temperatures, which does not contribute to improving the initial magnetic permeability. The preferred range of lithium addition is 220 to 580 mass ppm in terms of Li2CO3. More preferably, it is 250 to 550 mass ppm in terms of Li2CO3, and even more preferably, it is 300 to 500 mass ppm in terms of Li2CO3.

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

[0035] In the present invention, the value of ΔB [mT] calculated by the following formula (1) is set to 250 mT or more at 100°C. This is because in the case of high magnetic 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 of the value of ΔB [mT] is approximately 320 mT 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 is the residual magnetic flux density [mT])

[0036] The present invention provides a standardized impedance Z that can be calculated using 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 1 MHz is 40 Ω mm -1 This is to eliminate noise around 1 MHz. The preferable upper limit of this maximum value is 65 Ω mm -1 To an extent Here, conventionally, in the case of high permeability materials, the inductance at high frequencies is low, so the normalized impedance Z norm is 30 [Ω·mm -1 ] is about that level. 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 is the magnetic path length [mm], A e is the cross-sectional area [mm 2 ], N is the number of turns in the coil [-])

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

[0038] The sintered density of the MnZn ferrite of the present invention is 4.97 g / cm 3 By satisfying this requirement, the saturation magnetic flux density becomes 4.97 g / cm 3This is because the sintered density is improved compared to when the sintered density is less than 5.10 g / cm. 3 That's about it.

[0039] To achieve this sintered density, firing at a high temperature of 1370°C or higher is desirable. Furthermore, a longer firing time is preferable because it increases the sintered density. However, if the firing time is too long, the properties improve but productivity decreases, so the practical upper limit is approximately 12 hours. Furthermore, if the firing temperature is too high, the amount of Zn evaporation increases, significantly affecting composition fluctuations, so a maximum of approximately 1450°C is preferable. Furthermore, firing at a higher temperature for a longer period of time increases the crystal grain size, increasing the initial permeability but also increasing the flow of eddy currents within the grains, which increases eddy current loss and reduces the initial permeability and normalized impedance at high frequencies. Therefore, a temperature of 1370 to 1385°C and a time of 2 to 4 hours are considered more preferable firing conditions.

[0040] The MnZn ferrite of the present invention can be produced by any conventional method unless otherwise specified in this specification. [Example]

[0041] [Example 1] The raw material powders were weighed so that the ratio of Fe2O3, ZnO, and MnO was 53.44:17.09:27.47 mol%, when the iron, zinc, and manganese contained were all converted to Fe2O3, ZnO, and MnO. The powders were mixed for 16 hours using a wet ball mill and calcined in air at 925°C for 3 hours. Silicon oxide, calcium oxide, niobium oxide, and lithium oxide, calculated as SiO2, CaCO3, Nb2O5, and Li2CO3, were then added to the calcined powder in the ratios shown in Table 1, and the mixture was then pulverized in a wet ball mill for 16 hours. After the pulverization, the powder was dried, and polyvinyl alcohol (PVA) was added. The mixture was then granulated by passing it through a sieve to obtain a granulated powder. The granulated powder was formed into a toroidal shape to produce a compact, which was then introduced into a batch-type sintering furnace and sintered at a maximum temperature of 1370°C for 2 hours in a gas flow of an appropriate mixture of 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] For the toroidal core thus obtained, the sintered density was calculated at 23° C. by the Archimedes method, and the resistivity was measured by the four-terminal method. Next, 10 turns of copper wire were wound around the toroidal core, and the inductance L and quality factor Q were measured in the range of -20 to 200°C at 10 kHz using an LCR meter (Keysight 4980A). The Curie temperature T was calculated from the initial permeability calculated based on these values. C In addition, the inductance L and quality factor Q were measured at 23°C from 1k to 30MHz, and the normalized impedance Z·c1 / N was calculated by normalizing these values with the initial permeability and core constant. 2 was calculated. The toroidal core was wound with 40 turns of copper wire on the primary side and 20 turns on the secondary side, and the saturation magnetic flux density and residual magnetic flux density were measured using a DC magnetization characteristic tester with a maximum magnetizing force H of 1200 A / m. ΔB was calculated as the difference between the saturation magnetic flux density and the residual magnetic flux density. The results of investigating the effects of trace 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 the combinations of Nb2O5 and Li2CO3, V2O5 and Li2CO3, and Nb2O5, V2O5 and Li2CO3, the initial permeability is improved compared to the case without additives due to the effect of Li2CO3, and the maximum value of the normalized impedance is 40 Ω·mm -1 Furthermore, ΔB was able to reach 250 mT or more at 100°C.

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

[0046] The obtained toroidal core was measured for the same items using the same methods and procedures as in Example 1. The results of examples in which the basic composition and the amounts of SiO2 and CaCO3 added were changed and the effects of Nb2O5, V2O5, and Li2CO3 were investigated are also shown in Table 2. In Comparative Examples 11 and 12, Nb2O5, V2O5, and Li2CO3 were not added.

[0047] [Table 2]

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

Claims

1. An MnZn-based ferrite consisting of a basic component and a subcomponent, The basic ingredients mentioned above are: Iron: Fe ２ O ３ Converted to 51.00 to 54.00 mol%, Zinc: 15.00 to 21.00 mol% in terms of ZnO, and Manganese: Remainder Including, The above-mentioned minor components (excluding Ti and V) include: Si:SiO ２ Converted to 50 to 150 ppm by mass, Ca: CaCO ３ Converted to 250 to 1100 mass ppm, Nb: Nb ２ O ５ converted to 50 to 500 mass ppm and Li: Li ２ CO ３ Converted to more than 200 mass ppm and 600 mass ppm or less MnZn ferrite.

2. An MnZn-based ferrite consisting of a basic component and a subcomponent, The basic ingredients mentioned above are: Iron: Fe ２ O ３ Converted to 51.00 to 54.00 mol%, Zinc: 15.00 to 21.00 mol% in terms of ZnO, and Manganese: Remainder Including, The above-mentioned secondary components (excluding the case where Ti is contained) include: Si:SiO ２ Converted to 50 to 150 ppm by mass, Ca: CaCO ３ Converted to 250 to 1100 mass ppm, V:V ２ O ５ Converted to 100 to 700 mass ppm and Li: Li ２ CO ３ Converted to more than 200 mass ppm and 600 mass ppm or less MnZn ferrite.

3. An MnZn-based ferrite consisting of a basic component and a subcomponent, The basic ingredients mentioned above are: Iron: Fe ２ O ３ Converted to 51.00 to 54.00 mol%, Zinc: 15.00 to 21.00 mol% in terms of ZnO, and Manganese: Remainder Including, The above-mentioned secondary components (excluding the case where Ti is contained) include: Si:SiO ２ Converted to 50 to 150 ppm by mass, Ca: CaCO ３ Converted to 250 to 1100 mass ppm, Nb: Nb ２ O ５ Converted to 50 to 500 mass ppm, V:V ２ O ５ Converted to 100 to 700 mass ppm and Li: Li ２ CO ３ Converted to more than 200 mass ppm and 600 mass ppm or less MnZn ferrite.

4. 4. The MnZn-based ferrite according to claim 1, wherein the value of ΔB [mT] calculated by the following formula (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 is the residual magnetic flux density [mT])

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

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

7. Sintered density is 4.97 g / cm ３ The MnZn-based ferrite according to any one of claims 1 to 6.

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