MnZn-BASED FERRITE

Abstract

A MnZn-based ferrite that can reduce the loss even when a high-frequency voltage fluctuation occurs is provided. The above MnZn-based ferrite is a MnZn-based ferrite including Fe2O3, ZnO, and MnO as main components, in which Fe2O3 is 53.2 to 56.3 mol % and ZnO is 1.0 to 9.0 mol %, with a balance of MnO, in 100 mol % of the main components, and the MnZn-based ferrite includes 0.9 to 2.0% by mass of Co.sub.2O.sub.3, 0.005 to 0.06% by mass of SiO.sub.2, and 0.01 to 0.06% by mass of CaO, as auxiliary components, per 100% by mass of the main components.

Claims

1. A MnZn-based ferrite comprising Fe2O3, ZnO, and MnO as main components, wherein Fe2O3 is 53.2 to 56.3 mol % and ZnO is 1.0 to 9.0 mol %, with a balance of MnO, in 100 mol % of the main components, and the MnZn-based ferrite comprises 0.9 to 2.0% by mass of Co2O3, 0.005 to 0.06% by mass of SiO.sub.2, and 0.01 to 0.06% by mass of CaO, as auxiliary components, per 100% by mass of the main components.

2. The MnZn-based ferrite according to claim 1, further comprising 0.03 to 0.12% by mass in total of one or more selected from ZrO2, Ta2O5, and Nb2O5, as an auxiliary component, per 100% by mass of the main components.

3. The MnZn-based ferrite according to claim 1, wherein a hysteresis loop of a magnetization curve is a perminvar type.

4. The MnZn-based ferrite according to claim 1, wherein an initial magnetic permeability is 300 to 900 H/m.

5. The MnZn-based ferrite according to claim 1, wherein a residual magnetic flux density (Br) is 400 mT or less.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0017] FIG. 1 is graphs showing the hysteresis loops of Comparative Example 9, Comparative Example 10, Example 35, Example 36, Example 38, and Comparative Example 12.

DESCRIPTION OF EMBODIMENTS

[0018] Hereinafter, the MnZn-based ferrite according to the present invention will be described.

[0019] Unless otherwise specified, the numerical range represented by using “to” includes the lower limit value and the upper limit value thereof.

[0020] <MnZn-Based Ferrite>

[0021] The MnZn-based ferrite according to the present invention (hereinafter, also referred to as the present MnZn-based ferrite) includes Fe.sub.2O.sub.3, ZnO, and MnO as main components, in which Fe.sub.2O.sub.3 is 53.2 to 60.0 mol % and ZnO is 1.0 to 9.0 mol %, with a balance of MnO, in 100 mol % of the main components, and the MnZn-based ferrite includes 0.9 to 2.0% by mass of Co.sub.2O.sub.3, 0.005 to 0.06% by mass of SiO.sub.2, and 0.01 to 0.06% by mass of CaO, as auxiliary components, per 100% by mass of the main components.

[0022] It is presumed that because the present MnZn-based ferrite has the above composition, induced magnetic anisotropy is generated and the formation of the hysteresis loop into a perminvar type described later is promoted to reduce the loss when a high-frequency voltage fluctuation occurs, especially the hysteresis loss and the residual loss.

[0023] The hysteresis loop of a magnetization curve will be described with reference to FIG. 1. FIG. 1 is graphs 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 Co.sub.2O.sub.3 was changed in 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 has a non-perminvar type hysteresis loop, Comparative Examples 10 and 12 each have a weak perminvar type hysteresis loop, and Examples 35, 36 and 38 each have a perminvar type hysteresis loop.

[0024] In each graph, the horizontal axis represents the magnetic field H, the vertical axis represents the magnetic flux density B, and the slope of the hysteresis loop in the vicinity of H=0 is the initial magnetic permeability μ. In the non-perminvar type hysteresis loop, the initial magnetic permeability μ and the residual magnetic flux density Br each have a large value. On the other hand, in the perminvar type hysteresis loop, the initial magnetic permeability μ and the residual magnetic flux density Br each have a small value, and the magnetic flux density B follows a fluctuation in the magnetic field H, and thus the difference in magnetic flux density between when the magnetic field is changed in the positive direction and when the magnetic field is changed in the negative direction is small.

[0025] Because the present MnZn-based ferrite has the above composition, a perminvar type hysteresis loop can be obtained. As a result, it is presumed that the MnZn-based ferrite can reduce the hysteresis loss and the residual loss even when a high-frequency voltage fluctuation occurs.

[0026] In the present invention, the perminvar type, the weak perminvar type, and the non-perminvar type are defined as follows.

[0027] Perminvar type: μ≤700 and Br (mT)≤300,

[0028] Weak perminvar type: 700<μ≤900 and Br (mT)≤400, or μ≤900 and 300<Br (mT)≤400, and

[0029] Non-perminvar type: 900<μ or 400<Br (mT).

[0030] The present MnZn-based ferrite includes Fe.sub.2O.sub.3, ZnO, and MnO as main components.

[0031] Fe.sub.2O.sub.3 is 53.2 to 56.3 mol % in 100 mol % of the main components. When Fe.sub.2O.sub.3 is 53.2 mol % or more, a perminvar type hysteresis loop can be obtained, and Fe.sub.2O.sub.3 is preferably 53.8 mol % or more from the viewpoint of further reducing the loss. In addition, when Fe.sub.2O.sub.3 is 56.3 mol % or less, deterioration of the loss in a low temperature region can also be suppressed, and Fe.sub.2O.sub.3 is preferably 56.1 mol % or less, and more preferably 55.9 mol % or less, from the viewpoint of further reducing the loss.

[0032] 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 present MnZn-based ferrite is improved. When ZnO is 9.0 mol % or less, a perminvar type hysteresis loop can be obtained, and the loss is suppressed. ZnO is preferably 6.0 mol % or less from the viewpoint of further reducing the loss.

[0033] MnO is the balance of the main components (31 to 45.8 mol % in 100 mol % of the main components).

[0034] In addition, the present MnZn-based ferrite includes 0.9 to 2.0% by mass of Co.sub.2O.sub.3, 0.005 to 0.06% by mass of SiO.sub.2, and 0.01 to 0.06% by mass of CaO, as auxiliary components, per 100% by mass of the main components.

[0035] When Co.sub.2O.sub.3 is 0.9% by mass or more, perminvar type formation is promoted. In addition, when Co.sub.2O.sub.3 is 2.0% by mass or less, deterioration of the loss in a low temperature region can also be suppressed, and Co.sub.2O.sub.3 is preferably 1.7% by mass or less.

[0036] When SiO.sub.2 is 0.005% by mass or more, a grain boundary phase is sufficiently formed to suppress the loss and also improve the strength. In addition, when SiO.sub.2 is 0.06% by mass or less, the enlargement of a crystal grain is suppressed. SiO.sub.2 is preferably 0.02 to 0.05% by mass from the viewpoint of further reducing the loss.

[0037] When CaO is 0.01% by mass or more, a grain boundary phase is sufficiently formed to suppress the loss and also improve the strength. When CaO is 0.06% by mass or less, the enlargement of a crystal grain is suppressed. CaO is preferably 0.03 to 0.05% by mass from the viewpoint of further reducing the loss.

[0038] The present MnZn-based ferrite may further include a further component as long as the effects of the present invention are exhibited. Preferable components include ZrO.sub.2, Ta.sub.2O.sub.5, and Nb.sub.2O.sub.5. These components may be included singly or in combinations of two or more. The total content of the further component is preferably 0.03 to 0.12% by mass per 100% by mass of the main components.

[0039] The present MnZn-based ferrite is preferably one in which the hysteresis loop of a magnetization curve is a perminvar type, particularly from the viewpoint of reducing the hysteresis loss and the residual loss.

[0040] The present MnZn-based ferrite preferably has an initial magnetic permeability μ as described above of 300 to 900 H/m. When the initial magnetic permeability is within the range of 300 to 900 H/m, the loss is further reduced.

[0041] In addition, the present MnZn-based ferrite preferably has a residual magnetic flux density Br of 400 mT or less.

[0042] The present MnZn-based ferrite can be suitably used, for example, as a core material of an inductor used in a switching power supply circuit having a switching frequency of a high frequency (for example, 1 to 3 MHz).

[0043] <Method for Producing the Present MnZn-Based Ferrite>

[0044] The present MnZn-based ferrite may be appropriately selected from the methods by which the above properties are obtained. Hereinafter, a suitable method for producing a MnZn-based ferrite will be described with reference to an example.

[0045] First, Fe.sub.2O.sub.3, ZnO, and MnO, which are the main components, are blended in such a way as to have the above composition, and uniformly mixed, and granulated. The resulting powder may be calcined at, for example, about 650 to 950° C.

[0046] The resulting powder is disintegrated until the average particle diameter is less than about 1 μm, and the auxiliary components are added to the disintegrated powder in such a way as to have the above composition. The present MnZn-based ferrite can be obtained by uniformly mixing the resulting mixture and then firing the same at about 1150 to 1300° C.

EXAMPLES

[0047] Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The present invention is not limited by the descriptions thereof.

Example 1

[0048] Each raw material powder was weighed and mixed such that after sintering, the Fe.sub.2O.sub.3 content was 56.3 mol %, the ZnO content was 4.0 mol %, and the MnO content was 39.7 mol % to make a total of 100 mol %. In the mixing step, the mixture was disintegrated by using an attritor until the average particle size of the mixture was 1.0 μm. Next, in a drying/granulation step, when the total mass of the above mixture was 100 parts by mass, 0.5 parts by mass of polyvinyl alcohol was added, and the resulting mixture was sprayed by using a spray dryer to obtain a granule. Next, the granule was calcined at 750° C. for 1 hour in an air atmosphere to obtain a calcined product.

[0049] Raw material powders of auxiliary components, respectively, were added such that SiO.sub.2 was 0.03% by mass, CaO was 0.04% by mass, ZrO.sub.2 was 0.075% by mass, and Co.sub.2O.sub.3 was 1.5% by mass, when the total mass of the obtained calcined product was 100 parts by mass.

[0050] Next, as a disintegration step, a mixture of the calcined product and the additives was disintegrated by using a disintegrator such that the median particle diameter D50 after disintegration was 0.5 μm or more and 1.0 μm or less, to obtain a disintegrated powder. Next, as a drying/granulation step, when the total mass of the disintegrated product was 100 parts by mass, 1 part by mass of polyvinyl alcohol was added to the disintegrated product, and the resulting mixture was sprayed by using a spray dryer to obtain a granule. The median diameter D50 of the granule at this time was 100 μm. Next, as a molding step and a sintering step, the granule was molded into a toroidal type core having 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).

Examples 2 to 53 and Comparative Examples 1 to 12

[0051] Sintered bodies (MnZn-based ferrites) thereof were obtained in the same manner as in Example except that in Example 1, the blending proportions of the main components and the auxiliary components were changed to the blending proportions, respectively, shown in Tables 1 to 8.

<Evaluation Methods>

[0052] (1) Initial Magnetic Permeability

[0053] A primary winding was wound 10 times around the molded toroidal type MnZn-based ferrite (core), and the initial magnetic permeability u at 10 KHz at 23° C. was measured by using an impedance analyzer.

[0054] (2) Residual Magnetic Flux Density and Hysteresis Loop

[0055] A primary winding was wound 25 times and a secondary winding was wound 25 times around the molded toroidal type core, and the hysteresis loop when a magnetic field of 1000 A/m was applied was measured by using a BH analyzer to determine the residual magnetic flux density Br.

[0056] (3) Core Loss (Pcv)

[0057] A primary winding was wound 5 times and the secondary winding 5 times around the molded toroidal type core, and Pcv was measured by using a BH analyzer under conditions of 1 MHz-50 mT in atmospheres of 25° C. and 120° C.

[0058] Results thereof are shown in Table 1 to Table 8.

TABLE-US-00001 TABLE 1 Evaluation items Initial Residual Main components Auxiliary components magnetic magnetic flux [mol %] [% by mass] Pcv Pcv permeability μ density Br Hysteresis Example Fe.sub.2O.sub.3 MnO ZnO SiO.sub.2 CaO ZrO.sub.2 CO.sub.2O.sub.3 25° C. 120° C. [H/m] [mT] loop Comparative 56.4 39.6 4.0 0.03 0.04 0.075 1.5 760 320 280 330 Weak Example 1 perminvar Example 1 56.3 39.7 4.0 0.03 0.04 0.075 1.5 490 280 300 300 Perminvar Example 2 56.2 39.8 4.0 0.03 0.04 0.075 1.5 350 250 320 280 Perminvar Example 3 56.1 39.9 4.0 0.03 0.04 0.075 1.5 290 220 350 250 Perminvar Example 4 55.9 40.1 4.0 0.03 0.04 0.075 1.5 240 200 380 220 Perminvar Example 5 55.6 40.4 4.0 0.03 0.04 0.075 1.5 180 150 410 180 Perminvar Example 6 55.3 40.7 4.0 0.03 0.04 0.075 1.5 140 180 430 190 Perminvar Example 7 55.0 41.0 4.0 0.03 0.04 0.075 1.5 150 200 450 210 Perminvar Example 8 54.7 41.3 4.0 0.03 0.04 0.075 1.5 170 220 510 230 Perminvar Example 9 54.4 41.6 4.0 0.03 0.04 0.075 1.5 200 230 550 240 Perminvar Example 10 54.1 41.9 4.0 0.03 0.04 0.075 1.5 220 240 590 250 Perminvar Example 11 53.8 42.2 4.0 0.03 0.04 0.075 1.5 230 250 610 260 Perminvar Examela 12 53.5 42.5 4.0 0.03 0.04 0.075 1.5 250 260 640 260 Perminvar Example 13 53.2 42.8 4.0 0.03 0.04 0.075 1.5 270 280 690 270 Perminvar Comparative 53.1 42.9 4.0 0.03 0.04 0.075 1.5 280 300 740 280 Weak Example 2 perminvar

TABLE-US-00002 TABLE 2 Evaluation items Initial Residual Main components Auxiliary components magnetic magnetic flux [mol %] [% by mass] Pcv Pcv permeability μ density Br Hysteresis Example Fe.sub.2O.sub.3 MnO ZnO SiO.sub.2 CaO ZrO.sub.2 CO.sub.2O.sub.3 25° C. 120° C. [H/m] [mT] loop Comparative 54.1 35.9 10 0.03 0.04 0.075 1.5 320 360 790 300 Weak Example 3 perminvar Example 14 54.1 36.9 9.0 0.03 0.04 0.075 1.5 280 300 700 290 Perminvar Example 15 54.1 37.9 8.0 0.03 0.04 0.075 1.5 250 280 690 280 Perminvar Example 16 54.1 38.9 7.0 0.03 0.04 0.075 1.5 240 260 340 280 Perminvar Example 17 54.1 39.9 6.0 0.03 0.04 0.075 1.5 230 250 310 270 Perminvar Example 18 54.1 40.9 5.0 0.03 0.04 0.075 1.5 220 240 600 260 Perminvar Example 19 54.1 41.9 4.0 0.03 0.04 0.075 1.5 220 240 590 250 Perminvar Example 20 54.1 42.9 3.0 0.03 0.04 0.075 1.5 210 243 560 240 Perminvar Example 21 54.1 43.9 2.0 0.03 0.04 0.075 1.5 180 200 530 230 Perminvar Example 22 54.1 44.9 1.0 0.03 0.04 0.075 1.5 200 230 500 230 Perminvar

TABLE-US-00003 TABLE 3 Evaluation items Initial Residual Main components Auxiliary components magnetic magnetic flux [mol %] [% by mass] Pcv Pcv permeability μ density Br Hysteresis Example Fe.sub.2O.sub.3 MnO ZnO SiO.sub.2 CaO ZrO.sub.2 CO.sub.2O.sub.3 25° C. 120° C. [H/m] [mT] loop Comparative 54.1 41.9 4.0 0 0.04 0.075 1.5 300 340 580 250 Perminvar Example 4 Example 23 54.1 41.9 4.0 0.01 0.04 0.075 1.5 250 270 600 240 Perminvar Example 24 54.1 41.9 4.0 0.02 0.04 0.075 1.5 230 250 600 240 Perminvar Example 25 54.1 41.9 4.0 0.03 0.04 0.075 1.5 220 240 590 250 Perminvar Example 26 54.1 41.9 4.0 0.04 0.04 0.075 1.5 220 230 580 260 Perminvar Example 27 54.1 41.9 4.0 0.05 0.04 0.075 1.5 230 250 600 240 Perminvar Example 28 54.1 41.9 4.0 0.06 0.04 0.075 1.5 250 300 650 270 Perminvar Comparative 54.1 41.9 4.0 0.07 0.04 0.075 1.5 500 630 900 280 Weak Example 5 perminvar

TABLE-US-00004 TABLE 4 Evaluation items Initial Residual Main components Auxiliary components magnetic magnetic flux [mol %] [% by mass] Pcv Pcv permeability μ density Br Hysteresis Example Fe.sub.2O.sub.3 MnO ZnO SiO.sub.2 CaO ZrO.sub.2 CO.sub.2O.sub.3 25° C. 120° C. [H/m] [mT] loop Comparative 54.1 41.9 4.0 0.03 0 0.075 1.5 330 370 580 230 Perminvar Example 6 Example 29 54.1 41.9 4.0 0.03 0.01 0.075 1.5 270 290 580 240 Perminvar Example 30 54.1 41.9 4.0 0.03 0.02 0.075 1.5 250 270 590 250 Perminvar Example 31 54.1 41.9 4.0 0.03 0.03 0.075 1.5 230 250 580 260 Perminvar Example 32 54.1 41.9 4.0 0.03 0.04 0.075 1.5 220 240 590 250 Perminvar Example 33 54.1 41.9 4.0 0.03 0.05 0.075 1.5 230 250 620 260 Perminvar Example 34 54.1 41.9 4.0 0.03 0.06 0.075 1.5 260 280 640 270 Perminvar Comparative 54.1 41.9 4.0 0.03 0.07 0.075 1.5 550 650 880 280 Weak Example 7 perminvar

TABLE-US-00005 TABLE 5 Evaluation items Initial Residual Main components Auxiliary components magnetic magnetic flux [mol %] [% by mass] Pcv Pcv permeability μ density Br Hysteresis Example Fe.sub.2O.sub.3 MnO ZnO SiO.sub.2 CaO ZrO.sub.2 CO.sub.2O.sub.3 25° C. 120° C. [H/m] [mT] loop Comparative 54.1 41.9 4.0 0.03 0.04 0.075 0 1500 1100 800 470 Non-perminvar Example 8 Comparative 54.1 41.9 4.0 0.03 0.04 0.075 0.4 1050 700 710 410 Non-perminvar Example 9 Comparative 54.1 41.9 4.0 0.03 0.04 0.075 0.6 500 380 630 330 Weak perminvar Example 10 Comparative 54.1 41.9 4.0 0.03 0.04 0.075 0.8 320 310 620 310 Weak perminvar Example 11 Example 35 54.1 41.9 4.0 0.03 0.04 0.075 0.9 240 250 600 200 Perminvar Example 36 54.1 41.9 4.0 0.03 0.04 0.075 1.4 130 200 590 250 Perminvar Example 27 54.1 41.9 4.0 0.03 0.04 0.075 1.7 220 210 550 280 Perminvar Example 38 54.1 41.9 4.0 0.03 0.04 0.075 2.0 1350 230 410 300 Perminvar Comparative 54.1 41.9 4.0 0.03 0.04 0.075 2.2 2360 460 310 390 Weak perminvar Example 12

TABLE-US-00006 TABLE 6 Evaluation items Initial Residual Main components Auxiliary components magnetic magnetic flux [mol %] [% by mass] Pcv Pcv permeability μ density Br Hysteresis Example Fe.sub.2O.sub.3 MnO ZnO SiO.sub.2 CaO ZrO.sub.2 CO.sub.2O.sub.3 25° C. 120° C. [H/m] [mT] loop Example 39 54.1 41.9 4.0 0.03 0.04 0.000 1.5 330 370 560 220 Perminvar Example 40 54.1 41.9 4.0 0.03 0.04 0.020 1.5 320 340 570 240 Perminvar Example 41 54.1 41.9 4.0 0.03 0.04 0.030 1.5 270 290 590 250 Perminvar Example 42 54.1 41.9 4.0 0.03 0.04 0.050 1.5 230 250 580 240 Perminvar Example 43 54.1 41.9 4.0 0.03 0.04 0.075 1.5 220 240 590 250 Perminvar Example 44 54.1 41.9 4.0 0.03 0.04 0.100 1.5 230 250 630 260 Perminvar Example 45 54.1 41.9 4.0 0.03 0.04 0.120 1.5 260 280 640 260 Perminvar

TABLE-US-00007 TABLE 7 Evaluation items Initial Residual Main components Auxiliary components magnetic magnetic flux [mol %] [% by mass] Pcv Pcv permeability μ density Br Hysteresis Example Fe.sub.2O.sub.3 MnO ZnO SiO.sub.2 CaO ZrO.sub.2 CO.sub.2O.sub.3 25° C. 120° C. [H/m] [mT] loop Example 46 54.1 41.9 4.0 0.03 0.04 0 1.5 340 370 560 220 Perminvar Example 47 54.1 41.9 4.0 0.03 0.04 0.03 1.5 280 290 600 240 Perminvar Example 48 54.1 41.9 4.0 0.03 0.04 0.075 1.5 220 240 590 250 Perminvar Example 49 54.1 41.9 4.0 0.03 0.04 0.12 1.5 260 270 650 250 Perminvar

TABLE-US-00008 TABLE 8 Evaluation items Initial Residual Main components Auxiliary components magnetic magnetic flux [mol %] [% by mass] Pcv Pcv permeability μ density Br Hysteresis Example Fe.sub.2O.sub.3 MnO ZnO SiO.sub.2 CaO ZrO.sub.2 CO.sub.2O.sub.3 25° C. 120° C. [H/m] [mT] loop Example 50 54.1 41.9 4.0 0.03 0.04 0 1.5 340 370 570 220 Perminvar Example 51 54.1 41.9 4.0 0.03 0.04 0.03 1.5 280 290 600 230 Perminvar Example 52 54.1 41.9 4.0 0.03 0.04 0.075 1.5 230 250 590 250 Perminvar Example 53 54.1 41.9 4.0 0.03 0.04 0.12 1.5 270 270 650 250 Perminvar

SUMMARY OF RESULTS

[0059] It was shown that the MnZn-based ferrites of Examples 1 to 53 above each had a perminvar type hysteresis loop and has a reduced loss even when a voltage fluctuation at a high frequency of 1 MHz occurs, in which the MnZn-based ferrites contained Fe.sub.2O.sub.3, ZnO, and MnO as main components, in which Fe.sub.2O.sub.3 was 53.2 to 56.3 mol % and ZnO was 1.0 to 9.0 mol %, with a balance of MnO, in 100 mol % of the main components, and the MnZn-based ferrites contained 0.9 to 2.0% by mass of Co.sub.2O.sub.3, 0.005 to 0.06% by mass of SiO.sub.2, and 0.01 to 0.06% by mass of CaO, as auxiliary components, per 100% by mass of the main components.

[0060] The present application claims priority based on Japanese Patent Application No. 2020-176040 filed on Oct. 20, 2020, the disclosure of which is incorporated herein by reference in its entirety.