MnZn ferrite

Abstract

To provide a MnZn-based ferrite capable of reducing loss even against voltage fluctuation of high frequency.SOLUTION: A MnZn-based ferrite of the present invention is composed mainly of Fe2O3, ZnO and MnO. The ferrite contains 53.2-56.3 mol% of Fe2O3, 1.0-9.0 mol% of ZnO, and the balance MnO in 100 mol% of the main component, and contains 0.9-2.0 mass% of Co2O3, 0.005-0.06 mass% of SiO2, and 0.01-0.06 mass% of CaO as accessory components based on 100 mass% of the main component.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a MnZn-based ferrite. [Background technology]

[0002] MnZn-based ferrite has properties such as high initial permeability, high magnetic flux density, and ease of magnetization even in a small magnetic field, and is widely used for communication equipment applications, power supplies, etc. Various studies have been conducted on MnZn-based ferrite to obtain properties according to applications (e.g., Patent Documents 1-2).

[0003] For example, Patent Document 1 discloses a specific low-loss ferrite for liquid crystal backlights, which is a ferrite that adjusts the temperature range at which power loss is minimized to 20 to 60°C, and contains as main components 53.0 to 54.5 mol % of Fe2O3, 6 to 12 mol % of ZnO, and the remainder MnO, and contains as accessory components 200 to 1000 ppm of CaO, 0 to 300 ppm of SiO2, and 100 to 4000 ppm of CoO, and further contains 50 to 500 ppm of at least one of Nb2O5 and Ta2O5.

[0004] Patent Document 2 discloses a specific magnetic ferrite material that contains iron oxide, zinc oxide, and manganese oxide as main components, with the zinc oxide content in the range of 7.0 to 9.0 mol % calculated as ZnO, the manganese oxide content in the range of 36.8 to 39.2 mol % calculated as MnO, and the remainder iron oxide, as an auxiliary component, cobalt oxide in the range of 2500 to 4500 ppm calculated as Co3O4, as a MnZn-based magnetic ferrite material that has low power loss over a wide temperature range and small temperature change in power loss. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-2866 [Patent Document 2] JP 2001-80952 A Summary of the Invention [Problem to be solved by the invention]

[0006] As electronic devices become smaller and more powerful, efforts are being made to increase the switching frequency of switching power supplies (for example, 1 to 3 MHz). Core materials for inductors that make up switching power supply circuits are also being required to have low loss even at high switching frequencies.

[0007] The present invention is to solve the above problems, and provides an MnZn ferrite that can reduce loss even with high-frequency voltage fluctuations. [Means for solving the problem]

[0008] The MnZn-based ferrite according to the present invention is composed mainly of Fe2O3, ZnO, and MnO, In 100 mol % of the main component, Fe2O3 is 53.2 to 56.3 mol %, ZnO is 1.0 to 9.0 mol %, and the remainder is MnO, The composition is characterized in that it contains, relative to 100% by mass of the main component, 0.9 to 2.0% by mass of Co2O3, 0.005 to 0.06% by mass of SiO2, and 0.01 to 0.06% by mass of CaO as accessory components.

[0009] One embodiment of the MnZn-based ferrite further contains, as an accessory component, at least one selected from ZrO2, Ta2O5, and Nb2O5 in a total amount of 0.03 to 0.12 mass% relative to 100 mass% of the main component.

[0010] In one embodiment of the MnZn-based ferrite, the hysteresis loop of the magnetization curve is of the Perminvar type.

[0011] In one embodiment of the MnZn-based ferrite, the initial permeability is 300 to 900 H / m.

[0012] In one embodiment of the MnZn-based ferrite, the residual magnetic flux density (Br) is 400 mT or less.

Advantages of the Invention

[0013] The present invention provides an MnZn ferrite capable of reducing losses even against high-frequency voltage fluctuations.

Brief Description of the Drawings

[0014] [Figure 1] It is a graph showing the hysteresis loops of Comparative Example 9, Comparative Example 10, Example 35, Example 36, Example 38, and Comparative Example 12.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, the MnZn ferrite according to the present invention will be described. Note that "~" indicating a numerical range includes its lower limit value and upper limit value unless otherwise specified.

[0016] <MnZn Ferrite> The MnZn ferrite according to the present invention (hereinafter also referred to as the present MnZn ferrite) has Fe2O3, ZnO, and MnO as main components. Among 100 mol% of the main components, Fe2O3 is 53.2 to 60.0 mol%, ZnO is 1.0 to 9.0 mol%, and the balance is MnO. With respect to 100% by mass of the main components, as sub-components, it contains 0.9 to 2.0% by mass of Co2O3, 0.005 to 0.06% by mass of SiO2, and 0.01 to 0.06% by mass of CaO.

[0017] By having the above composition, the above-mentioned present MnZn ferrite generates induced magnetic anisotropy, promotes the permeabilization of the hysteresis loop described later, and is presumed to reduce losses against high-frequency voltage fluctuations, particularly hysteresis loss and residual loss.

[0018] The hysteresis loop of the magnetization curve will be described with reference to FIG. 1. FIG. 1 is a graph showing the hysteresis loops of Comparative Example 9, Comparative Example 10, Example 35, Example 36, Example 38, and Comparative Example 12, in which the amount of Co2O3 was changed in the examples described later. The hysteresis loops in FIG. 1 were measured at an applied magnetic field of 100 A / m in the evaluation method "residual magnetic flux density and hysteresis loop" of the examples described later. Comparative Example 9 is a non-Perminvar type hysteresis loop, Comparative Examples 10 and 12 are weak Perminvar type hysteresis loops, and Examples 35, 36, and 38 are Perminvar type hysteresis loops. In each graph, the horizontal axis represents the magnetic field H, and the vertical axis represents the magnetic flux density B, and the slope of the hysteresis loop near H = 0 is the initial permeability μ. In the non-Perminvar-type hysteresis loop, the values ​​of initial permeability μ and residual magnetic flux density Br are large. On the other hand, in the Perminvar-type hysteresis loop, the values ​​of initial permeability μ and residual magnetic flux density Br are small, and magnetic flux density B follows the fluctuations in the magnetic field H, so the difference in magnetic flux density when the magnetic field is changed in the positive direction and when it is changed in the negative direction is small. The MnZn-based ferrite has the above composition, and thus has a Perminvar-type hysteresis loop. As a result, it is presumed that the MnZn-based ferrite can reduce hysteresis loss and residual loss even in the case of high-frequency voltage fluctuations. In the present invention, the terms Perminvar type, weak Perminvar type, and non-Perminvar type are defined as follows. Perminvar type: μ≦700 and Br(mT)≦300 Weak Perminvar type: 700<μ≦900 and Br(mT)≦400; or μ≦900 and 300 <Br(mT)≦400 Non-Perminvar type: 900<μ or 400 <Br(mT)

[0019] This MnZn ferrite is composed mainly of Fe2O3, ZnO, and MnO. Fe2O3 is 53.2 to 56.3 mol% in 100 mol% of the main components. With Fe2O3 at 53.2 mol% or more, a Perminvar type hysteresis loop is obtained, and from the viewpoint of further reducing loss, 53.8 mol% or more is preferable. With Fe2O3 at 56.3 mol% or less, deterioration of loss in the low temperature region can be suppressed, and from the viewpoint of further reducing loss, 56.1 mol% or less is preferable, and 55.9 mol% or less is more preferable. ZnO is 1.0 to 9.0 mol% in 100 mol% of the main components. When ZnO is 1.0 mol% or more, the sinterability is excellent and the productivity of the MnZn-based ferrite is improved. When ZnO is 9.0 mol% or less, a Perminvar type hysteresis loop is obtained and loss is suppressed. From the viewpoint of further reducing loss, ZnO is preferably 6.0 mol% or less. The remainder of the main component (31 to 45.8 mol% of 100 mol% of the main component) is MnO.

[0020] The MnZn ferrite further contains, with respect to 100% by mass of the main component, 0.9 to 2.0% by mass of Co2O3, 0.005 to 0.06% by mass of SiO2, and 0.01 to 0.06% by mass of CaO as accessory components. By making the Co2O3 content 0.9 mass% or more, perminvarization is promoted. Also, by making the Co2O3 content 2.0 mass% or less, the deterioration of loss in the low temperature region can be suppressed, and a content of 1.7 mass% or less is preferable. When the SiO2 content is 0.005% by mass or more, the grain boundary phase is sufficiently formed, the loss is suppressed, and the strength is improved. Also, when the SiO2 content is 0.06% by mass or less, the enlargement of the crystal grains is suppressed. From the viewpoint of further reducing the loss, the SiO2 content is preferably 0.02 to 0.05% by mass. When the CaO content is 0.01% by mass or more, the grain boundary phase is sufficiently formed, the loss is suppressed, and the strength is improved. When the CaO content is 0.06% by mass or less, the enlargement of the crystal grains is suppressed. From the viewpoint of further reducing the loss, the CaO content is preferably 0.03 to 0.05% by mass.

[0021] The MnZn ferrite may further contain other components within the range in which the effects of the present invention are achieved. Preferred components include ZrO2, Ta2O5, Nb2O5, etc. These components may be used alone or in combination of two or more. The total content of the other components is preferably 0.03 to 0.12 mass% relative to 100 mass% of the main component.

[0022] From the viewpoint of reducing hysteresis loss and residual loss in particular, the present MnZn-based ferrite preferably has a Perminvar-type hysteresis loop in the magnetization curve.

[0023] The present MnZn ferrite preferably has an initial magnetic permeability μ of 300 to 900 H / m. When the initial magnetic permeability is within the range of 300 to 900 H / m, loss is further reduced. Moreover, the MnZn ferrite preferably has a residual magnetic flux density Br of 400 mT or less.

[0024] The present MnZn ferrite can be suitably used, for example, as a core material for an inductor used in a switching power supply circuit having a high switching frequency (for example, 1 to 3 MHz).

[0025] <Method of manufacturing the present MnZn-based ferrite> The present MnZn-based ferrite may be produced by any method that can provide the above-mentioned properties. A preferred method for producing Zn-based ferrite will now be described by way of example.

[0026] First, the main components Fe2O3, ZnO, and MnO are blended to obtain the above composition, mixed uniformly, and granulated. The obtained powder may be calcined at, for example, about 650 to 950°C.

[0027] The obtained powder is crushed until the average particle size is about less than 1 μm, and the sub-components are added to the crushed powder so as to obtain the above-mentioned composition. After uniformly mixing, the mixture is fired at about 1150 to 1300° C. to obtain the present MnZn-based ferrite. EXAMPLES

[0028] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these descriptions.

[0029] [Example 1] The raw powders were weighed and mixed so that the total content after sintering was 100 mol%, with Fe2O3 content of 56.3 mol%, ZnO content of 4.0 mol%, and MnO content of 39.7 mol%. In the mixing process, the mixture was crushed with an attritor until the average particle size of the mixture was 1.0 μm. Next, in the drying and granulation process, 0.5 parts by mass of polyvinyl alcohol was added per 100 parts by mass of the total mass of the mixture, and granules were obtained by spraying with a spray dryer. Next, in the calcination process, the mixture was calcined at 750°C for 1 hour in an air atmosphere to obtain a calcined product.

[0030] When the total mass of the obtained calcined product was taken as 100 parts by mass, the raw material powders were added as accessory components such that the amounts of SiO2, CaO, ZrO2, and Co2O3 were 0.03% by mass, 0.04% by mass, 0.075% by mass, and 1.5% by mass, respectively.

[0031] Next, in the crushing process, the mixture of the calcined material and additives was crushed in a crusher so that the median diameter D50 of the particle size after crushing was 0.5 μm or more and 1.0 μm or less to obtain crushed powder. Next, in the drying and granulation process, 1 part by mass of polyvinyl alcohol was added to the crushed material when the total mass of the crushed material was 100 parts by mass, and granules were obtained by spraying with a spray dryer. The median diameter D50 of the granules at this time was 100 μm. Next, in the molding and sintering processes, the granules were molded into a toroidal core with an outer diameter of 16 mm, an inner diameter of 10 mm, and a height of 5 mm, and sintered at 1200 °C to obtain a sintered body (MnZn-based ferrite).

[0032] [Examples 2 to 53, Comparative Examples 1 to 12] In the above Example 1, the blending ratios of the main components and the subcomponents were changed as shown in Tables 1 to 8, but in the same manner as in the Example, each sintered body (MnZn ferrite) was obtained.

[0033] <Evaluation method> (1) Initial permeability The primary winding was wound 10 times around the molded toroidal MnZn ferrite (core), and the initial permeability μ at 10 KHz at 23° C. was measured using an impedance analyzer. (2) Residual magnetic flux density and hysteresis loop The primary winding was wound 25 times and the secondary winding was wound 25 times around the molded toroidal core, and the hysteresis loop was measured when a magnetic field of 1000 A / m was applied using a BH analyzer to determine the residual magnetic flux density Br. (3) Core loss (PCV) The primary winding was wound five times and the secondary winding five times around the molded toroidal core, and the Pcv was measured under the conditions of 1MHz-50mT using a BH analyzer in an atmosphere of 25℃ and 120℃. The results are shown in Tables 1 to 8.

[0034] [Table 1]

[0035] [Table 2]

[0036] [Table 3]

[0037] [Table 4]

[0038] [Table 5]

[0039] [Table 6]

[0040] [Table 7]

[0041] [Table 8]

[0042] [Summary of results] The MnZn-based ferrites of Examples 1 to 53 described above, which contain Fe2O3, ZnO, and MnO as main components, with 53.2 to 56.3 mol% of Fe2O3, 1.0 to 9.0 mol% of ZnO, and the remainder MnO in 100 mol% of the main components, and contain, as accessory components, 0.9 to 2.0 mass% of Co2O3, 0.005 to 0.06 mass% of SiO2, and 0.01 to 0.06 mass% of CaO relative to 100 mass% of the main components, all obtained a Perminvar-type hysteresis loop, and were shown to reduce losses even with respect to high-frequency voltage fluctuations of 1 MHz.

Claims

1. Fe ２ O ３ The main components are ZnO and MnO, In 100 mol% of the main components, Fe ２ O ３ is 53.2 to 56.3 mol %, ZnO is 1.0 to 9.0 mol %, and the remainder is MnO; Co as an auxiliary component relative to 100% by mass of the main component ２ O ３ 0.9 to 2.0 mass% of SiO ２ 0.005 to 0.06 mass %, CaO 0.01 to 0.06 mass %, ZrO 2 0 to 0.12 mass %, An MnZn-based ferrite with a Perminvar-type hysteresis loop in the magnetization curve.

2. Fe ２ O ３ The main components are ZnO and MnO, In 100 mol% of the main components, Fe ２ O ３ is 53.2 to 56.3 mol %, ZnO is 1.0 to 9.0 mol %, and the remainder is MnO; Co as an auxiliary component relative to 100% by mass of the main component ２ O ３ 0.9 to 2.0 mass% of SiO ２ 0.005 to 0.06 mass %, CaO 0.01 to 0.06 mass %, ZrO 2 0 to 0.12 mass %, An MnZn-based ferrite having an initial magnetic permeability of 300 to 900 H / m.

3. Fe ２ O ３ The main components are ZnO and MnO, In 100 mol% of the main components, Fe ２ O ３ is 53.2 to 56.3 mol %, ZnO is 1.0 to 9.0 mol %, and the remainder is MnO; Co as an auxiliary component relative to 100% by mass of the main component ２ O ３ 0.9 to 2.0 mass% of SiO ２ 0.005 to 0.06 mass %, CaO 0.01 to 0.06 mass %, ZrO 2 0 to 0.12 mass %, A MnZn-based ferrite having a residual magnetic flux density (Br) of 400 mT or less.

4. An MnZn-based ferrite according to any one of claims 1 to 3, containing 0.03 to 0.12 mass% of ZrO2 relative to 100 mass% of the main component.

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