MnZn-based ferrite and method for producing MnZn-based ferrite

Abstract

Provided is a MnZn-based ferrite having excellent characteristics of maximum magnetic flux density (Bm) even in a high-temperature environment. The MnZn ferrite according to one embodiment of the present invention contains Fe2O3, ZnO, and MnO as main components, in 100 mol% of the main components, the content of Fe2O3 is 56.0 to 59.0 mol%, the content of ZnO is 2.5 to 7.0 mol%, and the remainder is MnO, and the MnZn ferrite contains 0.010 to 0.050 mass% of SiO2, 0.020 to 0.060 mass% of CaO, and 0.150 to 0.350 mass% of Co2O3 as auxiliary components relative to 100 mass% of the main components.

Description

TECHNICAL FIELD

[0001] The present application relates to a MnZn-based ferrite and a method for producing a MnZn-based ferrite. BACKGROUND

[0002] MnZn-based ferrites are widely used for communication equipment applications, power supply applications, and the like, because they have characteristics such as high permeability, high magnetic flux density, and easy magnetization even for a small magnetic field. Various studies are being made on MnZn-based ferrites to obtain characteristics corresponding to the applications.

[0003] In Patent Literature 1, as a MnZn-based ferrite sintered body having low magnetic core loss in a wide temperature range at a high frequency of 300 to 500 kHz and small temporal change in the magnetic core loss in a high-temperature environment, a MnZn-based ferrite sintered body containing main components composed of specific amounts of Fe2O3, ZnO, and MnO and sub-components composed of specific amounts of SiO2, CaCO3, Co3O4, ZrO2, and Ta2O5, having an average crystal grain diameter of 3 μm or more and less than 8 μm, and a sintered body density of 4.65 g / cm3 or more and less than 4.75 g / cm3 is disclosed. 3 The above.

[0004] In Patent Literature 2, as a MnZn-based ferrite having low power loss in a wide temperature range and operating magnetic flux density even at a high frequency of 1 MHz or more, a low-loss MnZn-based ferrite containing specific amounts of Fe, Mn, and Zn as main components, containing specific amounts of Co, Ca, and Si as first sub-components, containing specific amounts of Va group elements as second sub-components, having an average crystal grain diameter of less than 3.2 μm, and having a volume resistivity of 1 Ω·m or more is disclosed.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT LITERATURE

[0007] Patent Literature 1: International Publication No. 2018 / 181242;

[0008] Patent Literature 2: International Publication No. 2006 / 054749. SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] In recent years, MnZn-based ferrites are used in various environments, and the use in a high-temperature environment is also increasing. In addition, in order to improve the direct current superimposition characteristics in a product using a high-frequency low-loss ferrite, a ferrite having good characteristics of maximum magnetic flux density Bm is required. Therefore, a ferrite having good characteristics of maximum magnetic flux density Bm even in a high-temperature environment is required.

[0011] In view of the above problems, it is an object of the present application to provide a MnZn ferrite having excellent characteristics of maximum magnetic flux density Bm even in a high-temperature environment and a method for manufacturing a MnZn ferrite.

[0012] Solution to Problem

[0013] The MnZn ferrite of one embodiment of the present application contains Fe2O3, ZnO, and MnO as main components, and in 100 mol% of the main components, Fe2O3 is 56.0 to 59.0 mol%, ZnO is 2.5 to 7.0 mol%, and the remainder is MnO. The MnZn ferrite contains the following components as sub-components: 0.010 to 0.050 mass% of SiO2, 0.020 to 0.060 mass% of CaO, and 0.150 to 0.350 mass% of Co2O3, relative to 100 mass% of the main components.

[0014] The MnZn ferrite can further contain 0.010 to 0.100 mass% of ZrO as a sub-component.

[0015] The maximum magnetic flux density Bm of the MnZn ferrite at 100 °C can be 450 mT or more.

[0016] The sintered density of the MnZn ferrite can be 4.9 g / cm 3 or more.

[0017] The unit volume core loss (Pcv) of the MnZn ferrite at 100 °C, 1 MHz, and 50 mT can be 250 mW / cm 3 or less.

[0018] The magnetic permeability μ of the MnZn ferrite at 25 °C can be 450 or more.

[0019] The method for manufacturing a MnZn ferrite of one embodiment of the present application is a method for manufacturing the above-described MnZn ferrite, and includes a step of mixing raw materials containing each main component so that Fe2O3 is 56.0 to 59.0 mol%, ZnO is 2.5 to 7.0 mol%, and the remainder is MnO in 100 mol% of the main components after sintering; a step of adding raw materials containing each sub-component so that 0.010 to 0.050 mass% of SiO2, 0.020 to 0.060 mass% of CaO, and 0.150 to 0.350 mass% of Co2O3 are contained relative to 100 mass% of the main components after sintering; and a step of crushing the obtained mixed powder until the crushed powder has a D90 particle diameter of 1.2 μm or less.

[0020] The method for producing the MnZn ferrite described above can further include a step of molding the crushed powder and performing heat treatment at 1150 to 1250°C.

[0021] Effects of Invention

[0022] According to the present application, it is possible to provide a MnZn ferrite and a method for producing a MnZn ferrite, which have good characteristics of maximum magnetic flux density Bm even in a high-temperature environment. DETAILED DESCRIPTION

[0023] Hereinafter, the MnZn ferrite and the method for producing a MnZn ferrite of the present application will be described. In addition, "to" indicating a numerical range includes the lower limit value and the upper limit value thereof unless otherwise specified.

[0024] [MnZn Ferrite]

[0025] The MnZn ferrite of the present application (hereinafter also referred to as the present MnZn ferrite) contains Fe2O3, ZnO, and MnO as main components,

[0026] In 100 mol% of the main components described above, Fe2O3 is 56.0 to 59.0 mol%, ZnO is 2.5 to 7.0 mol%, and the remainder is MnO,

[0027] The MnZn ferrite described above contains the following components as sub-components:

[0028] 0.010 to 0.050 mass% of SiO2; 0.020 to 0.060 mass% of CaO; and 0.150 to 0.350 mass% of Co2O3, with respect to 100 mass% of the main components described above.

[0029] The present MnZn ferrite contains Fe2O3, ZnO, and MnO as main components. In the present MnZn ferrite, in 100 mol% of the main components, Fe2O3 is 56.0 to 59.0 mol%, ZnO is 2.5 to 7.0 mol%, and the remainder (34.0 to 41.5 mol%) is MnO.

[0030] By making Fe2O3 56.0 mol% or more, preferably 57.0 mol% or more, it is possible to obtain a MnZn ferrite having a high maximum magnetic flux density Bm at 100°C. On the other hand, by making Fe2O3 59.0 mol% or less, preferably 58.0 mol% or less, it is possible to obtain a MnZn ferrite having a low core loss per volume (Pcv) at 100°C, 1 MHz, 50 mT, and a high permeability μ at 25°C.

[0031] Further, by making ZnO 2.5 mol% or more, preferably 3.5 mol% or more, it is possible to obtain an MnZn-based ferrite having low core loss per volume (Pcv) at 100°C, 1 MHz, 50 mT. On the other hand, by making ZnO 7.0 mol% or less, preferably 5.5 mol% or less, it is possible to obtain an MnZn-based ferrite having high maximum magnetic flux density Bm at 100°C.

[0032] Further, the present MnZn-based ferrite contains at least SiO2, CaO, and Co2O3 as subcomponents.

[0033] Further, by making SiO2 0.010 mass% or more, preferably 0.015 mass% or more, more preferably 0.025 mass% or more, and making SiO2 0.050 mass% or less, preferably 0.045 mass% or less, it is possible to obtain an MnZn-based ferrite having low core loss per volume (Pcv) at 100°C, 1 MHz, 50 mT.

[0034] Further, by making CaO 0.020 mass% or more, preferably 0.025 mass% or more, more preferably 0.030 mass% or more, and making CaO 0.060 mass% or less, preferably 0.055 mass% or less, more preferably 0.045 mass% or less, it is possible to obtain an MnZn-based ferrite having low core loss per volume (Pcv) at 100°C, 1 MHz, 50 mT.

[0035] Further, by making Co2O3 0.150 mol% or more, preferably 0.250 mol% or more, it is possible to obtain an MnZn-based ferrite having low core loss per volume (Pcv) at 100°C, 1 MHz, 50 mT. On the other hand, by making Co2O3 0.350 mol% or less, preferably 0.300 mol% or less, it is possible to obtain an MnZn-based ferrite having high permeability μ at 25°C.

[0036] The present MnZn-based ferrite can further contain other components within a range where the effects of the present application are exerted. As the other components, there can be mentioned other metal oxides added as needed, elements unavoidably contained, and the like. As the other metal oxides, there can be mentioned, for example, ZrO2, Ta2O5, Nb2O5, Bi2O3, MoO3, and the like, with ZrO2 being particularly preferred. Further, as the elements unavoidably contained, there can be mentioned C (carbon atom), P (phosphorus atom), B (boron atom), and the like.

[0037] The present MnZn ferrite can obtain a MnZn ferrite having a core loss per volume (Pcv) of 250 mW / cm3 at 100°C, 1 MHz, 50 mT, by making the content of ZrO2 0.010 mass% or more, preferably 0.030 mass% or more, and making the content of ZrO2 0.100 mass% or less, preferably 0.060 mass% or less, more preferably 0.050 mass% or less.

[0038] The total content of the other metal oxides and elements other than ZrO2 is preferably 0.1 mass% or less, more preferably 0.01 mass% or less, with respect to 100 mass% of the main components.

[0039] In the present MnZn ferrite described above, since the content of Fe2O3 is increased and the content of ZnO is decreased, the Curie temperature Tc can be increased, and thus the maximum magnetic flux density Bm at 100°C can be 450 mT or more. Thus, a MnZn ferrite having a good characteristic of the maximum magnetic flux density Bm even in a high-temperature environment can be provided.

[0040] Further, the present MnZn ferrite has the above composition, and thus a MnZn ferrite having a core loss per volume (Pcv) of 250 mW / cm3 at 100°C, 1 MHz, 50 mT can be obtained. 3 The following MnZn ferrite. Further, the present MnZn ferrite has the above composition, and thus a MnZn ferrite having a magnetic permeability μ of 450 or more at 25°C can be obtained.

[0041] The present MnZn ferrite can be particularly preferably used for a power supply circuit or the like used in a high-frequency and high-temperature environment such as a server.

[0042] [Method for manufacturing MnZn ferrite]

[0043] Next, one embodiment of a method for manufacturing a MnZn ferrite (hereinafter, also referred to as the present manufacturing method) will be described.

[0044] The production method is a production method capable of suitably producing the above-described MnZn-based ferrite, and includes at least the following steps: a step (mixing step) of mixing raw materials containing respective main components so that, after sintering, Fe2O3 is 56.0 to 59.0 mol% and ZnO is 2.5 to 7.0 mol% out of 100 mol% of the main components, and the remainder is MnO; a step (adding step) of adding raw materials containing respective sub components so that, after sintering, 0.010 to 0.050 mass% of SiO2, 0.020 to 0.060 mass% of CaO, and 0.150 to 0.350 mass% of Co2O3 are contained with respect to 100 mass% of the above-described main components; and a step (crushing step) of crushing the resulting mixed powder until the D90 particle diameter is 1.2 μm or less. The production method can further include a drying and granulating step of adding a binder to the mixed powder of the main components after the above-described mixing step and granulating; a pre-sintering step of pre-sintering the resulting granules; a drying and granulating step of the crushed powder or the granules thereof; a molding step of molding the crushed powder or the granules thereof; a heat treatment step (sintering step) of subjecting the molded body to heat treatment; and the like.

[0045] In the above-described mixing step, the main components are mixed so that the main components after sintering become the composition of the above-described MnZn ferrite. The form of the main components before mixing is not particularly limited, and is preferably in powder form from the viewpoint of easy handling and uniform mixing. The raw material powder of the main components is mixed and crushed as necessary to produce a mixed powder. The mixing and crushing method can be appropriately selected from publicly known methods. Specifically, a pulverizer, a bead mill, or the like can be mentioned. The particle diameter of the mixed powder is not particularly limited, and is preferably adjusted so that the median particle diameter D50 is 0.5 μm to 1.5 μm from the viewpoint of uniformity and the like. The D50 of the particle diameter and the D90 described later are particle diameters at which the cumulative frequency of the particle diameter becomes 50% (D50) and 90% (D90), respectively, in the particle size distribution of each of the particles as the object. In addition, the particle size distribution of the mixed powder can be measured using a particle size distribution measuring device.

[0046] The drying and granulating step can also be performed for the mixed powder of the above-described main components. In the drying and granulating step, for example, 0.5 to 1 mass parts of a binder such as polyvinyl alcohol is added to the mixed powder obtained in the mixing step, and spraying is performed using a spray dryer or the like, whereby granules can be obtained. Subsequently, the obtained granules can be pre-sintered, for example, at 750°C for about 1 hour in an air atmosphere to produce a pre-sintered product (pre-sintering step).

[0047] Next, a sub-component is added to the pre-sinter to make the sub-component after sintering the composition of the above-described MnZn ferrite. The form of the sub-component before addition is not particularly limited, and is preferably in a granular form from the viewpoint of ease of handling and uniform mixing.

[0048] After the addition of the sub-component, the resulting mixed powder is crushed to obtain a crushed powder. The crushing is appropriately adjusted so that the average crystal grain size of the resulting MnZn ferrite is 6 μm or less. Methods such as crushing the pre-sinter until the D90 of the particle size after crushing is 1.2 μm or less can be mentioned.

[0049] In the drying and granulation step, 0.5 to 1.0 parts by mass of a binder such as polyvinyl alcohol is added to the crushed powder obtained in the crushing step, and spraying is performed using a spray dryer or the like, whereby granules are obtained. At this time, the median particle size D50 of the granules is desirably 40 μm or more and 200 μm or less.

[0050] In the molding step, the granules obtained in the drying and granulation step are molded into a prescribed shape. The prescribed shape can be designed as appropriate according to the use or the like. For example, the granules are molded into a toroidal core having an outer diameter of 15 mm, an inner diameter of 10 mm, and a height of 6 mm.

[0051] By heat-treating the molded granules, a sintered body (MnZn ferrite) is produced. The heat-treatment (sintering) conditions are preferably heating at 1150 to 1250°C for several hours. By heat-treating at 1150°C or higher, a sintered density of 4.9 g / cm 3 The above. Furthermore, a MnZn ferrite having a high maximum magnetic flux density Bm at 100°C can be obtained. On the other hand, by heat-treating at 1250°C or lower, a MnZn ferrite having a low magnetic core loss per volume (Pcv) at 100°C, 1 MHz, and 50 mT can be obtained.

[0052] By the present application described above, a MnZn ferrite having good characteristics in the maximum magnetic flux density Bm even in a high-temperature environment and low loss, and a method for producing a MnZn ferrite can be provided.

[0053] Example

[0054] Hereinafter, examples and comparative examples are mentioned to specifically describe the present application. In addition, the present application is not limited by these descriptions.

[0055] [Example 1]

[0056] The raw material powders were weighed and mixed so that the Fe2O3 content after sintering was 56.00 mol%, the ZnO content was 5.50 mol%, and the MnO content was 38.50 mol%, totaling 100 mol%. With respect to 100 parts by mass of the total mass of the above mixture, 0.5 parts by mass of polyvinyl alcohol was added, and spraying was performed using a spray dryer, whereby granules were obtained. Next, the granules were pre-fired at 750°C for 1 hour in an air environment, and a pre-fired product was obtained. Next, with respect to 100 parts by mass of the main component, SiO2 was added to the pre-fired product so that the SiO2 content after sintering was 0.045 parts by mass, and similarly, Ca(OH)2 was added so that the CaO content after sintering was 0.025 parts by mass, Co3O4 was added so that the Co2O3 content after sintering was 0.300 parts by mass, and ZrO2 was added so that the ZrO2 content after sintering was 0.050 parts by mass.

[0057] Next, as a crushing step, the mixture of the pre-fired product and the additives was crushed using a crusher so that the D90 of the particle size after crushing was 1.2 μm or less, and a crushed powder was obtained. Next, as a drying and granulating step, 1 part by mass of polyvinyl alcohol was added to the crushed powder when the total mass of the crushed powder was 100 parts by mass, and spraying was performed using a spray dryer, whereby granules were obtained. Next, as a molding step and a sintering step, the granules were molded into a core in the shape of a circular ring with an outer diameter of 12 mm, an inner diameter of 8 mm, and a height of 5 mm, and sintering was performed at an oxygen partial pressure (PO2) of 3.3% and a sintering temperature of 1150°C, and a sintered body (MnZn-based ferrite) was obtained.

[0058] [Examples 2 to 11, Comparative Examples 1 to 12]

[0059] In Example 1, the raw materials were mixed and added in such a manner that the contained proportions of the main component and the subcomponent after sintering were as shown in Table 1, and otherwise, the MnZn-based ferrites of Examples 2 to 11 and Comparative Examples 1 to 12 were obtained in the same manner as in Example 1.

[0060] <Assessment>

[0061] A test sample was produced by winding a copper wire 22 times on the primary side and 22 times on the secondary side on a molded toroidal core, and the maximum magnetic flux density Bm of the MnZn-based ferrite at 100°C was measured using a BH analyzer. A test sample was produced by winding a copper wire 5 times on a molded toroidal core, and the permeability μ of the MnZn-based ferrite at 25°C was measured using an impedance analyzer. A test sample was produced by winding a copper wire 5 times on the primary side and 5 times on the secondary side on a molded toroidal core, and the unit volume magnetic core loss (Pcv) of the MnZn-based ferrite at 100°C, 1 MHz, and 50 mT was measured using a BH analyzer. The sintered density was measured by the Archimedes method. The broken particle size D90 was found by measuring the slurry of the broken powder obtained during the production process of the above-described examples and comparative examples using a wet-type particle size distribution measuring device. From the images obtained by mirror-polishing each of the MnZn-based ferrites obtained in the examples and comparative examples, dissolving the grain boundary phase by etching, and observing with a microscope, the average crystal grain size was calculated by image analysis. In addition, the measurement was performed on 100 crystal grains, respectively. The results are shown in Table 1.

[0062] [Table 1]

[0063]

[0064] [Results]

[0065] In the MnZn-based ferrites of Examples 1 to 11, in 100 mol% of the main component, Fe2O3 was 56.00 to 59.00 mol%, ZnO was 2.50 to 7.00 mol%, and the remainder was MnO, and with respect to 100 mass% of the main component, 0.010 to 0.050 mass% of SiO2, 0.020 to 0.060 mass% of CaO, 0.150 to 0.350 mass% of Co2O3, and 0.000 to 0.100 mass% of ZrO2 were contained as sub-components, the maximum magnetic flux density Bm at 100°C was 450 mT or more, and the unit volume magnetic core loss (Pcv) at 100°C, 1 MHz, and 50 mT was 250 mW / cm 3 Hereinafter, the permeability μ at 25°C was 450 or more, and the sintered density was 4.9 g / cm 3 or more.

[0066] The present application has been described based on the above-described embodiments, but the present application is not limited only to the configuration of the above-described embodiments, and various modifications, combinations, and the like that can be made by those skilled in the art within the scope of the invention claimed in the claims of the present application are also included.

[0067] This application claims priority based on Japanese Application No. 2023-112999, filed on July 10, 2023, and incorporates all of its disclosures herein.

Claims

1. A MnZn-based ferrite containing Fe2O3, ZnO, and MnO as main components. In the 100 mol% of the principal component, Fe2O3 content was 56.0–59.0 mol% ZnO content is 2.5–7.0 mol% The remaining part is MnO. The MnZn-based ferrite contains the following components as secondary components: Relative to 100% by mass of the principal component, 0.010–0.050% by mass of SiO2; 0.020–0.060% by mass of CaO; 0.150–0.350% by mass of Co2O3.

2. The MnZn-based ferrite according to claim 1, wherein, The MnZn-based ferrite further contains 0.010 to 0.100% by mass of ZrO as a secondary component.

3. The MnZn-based ferrite according to claim 1 or 2, wherein, The maximum magnetic flux density Bm of the MnZn-based ferrite at 100℃ is above 450mT.

4. The MnZn-based ferrite according to claim 1 or 2, wherein, The sintering density of the MnZn-based ferrite is 4.9 g / cm³. 3 above.

5. The MnZn-based ferrite according to claim 1 or 2, wherein, The MnZn-based ferrite exhibits a core loss (Pcv) of 250 mW / cm² at 100 °C, 1 MHz, and 50 mT. 3 the following.

6. The MnZn-based ferrite according to claim 1 or 2, wherein, The MnZn-based ferrite has a permeability μ of over 450 at 25℃.

7. A method for manufacturing MnZn-based ferrite, wherein the MnZn-based ferrite is the MnZn-based ferrite as described in claim 1 or 2. The manufacturing method includes: The process of mixing raw materials containing each main component so that, after sintering, the main components contain 56.0–59.0 mol% Fe2O3, 2.5–7.0 mol% ZnO, and the remainder MnO. The process of adding raw materials containing each of the secondary components so that, relative to 100% by mass of the main component, the sintered product contains 0.010–0.050% by mass of SiO2, 0.020–0.060% by mass of CaO, and 0.150–0.350% by mass of Co2O3; and The process of crushing the resulting mixed powder until it becomes a crushed powder with a D90 particle size of less than 1.2 μm.

8. The method for manufacturing MnZn-based ferrite according to claim 7, wherein, The manufacturing method further includes the step of shaping the crushed powder and heat-treating it at 1150-1250°C.

Images