Mnzn-based ferrite

Abstract

Provided is an MnZn-based ferrite having a high incremental permeability over a wide temperature range. The MnZn-based ferrite according to the present invention is composed of a base component, a secondary component, and unavoidable impurities. Using 100.0 mol% for the sum of Fe, Zn, and Mn as, respectively, Fe2O3, ZnO, and MnO, the base component is Fe : 52.0 mol% to 53.6 mol% as Fe2O3, Zn : 10.1 mol% to less than 13.0 mol% as ZnO, and Mn : balance. The secondary component comprises, with reference to the base component, Si : 30 to 200 ppm by mass as SiO2, Ca : 300 to 1000 ppm by mass as CaO, Co : 2100 to 3500 ppm by mass as Co3O4, Ti : 2500 to 4000 ppm by mass as TiO2, Nb : 50 to 500 ppm by mass as Nb2O5, and V : 0 to 500 ppm by mass as V2O5.

Description

MnZn ferrite

[0001] The present invention relates to an MnZn-based ferrite, and more particularly to an MnZn-based ferrite suitable for electronic components such as pulse transformers.

[0002] The transformers used in Ethernet (registered trademark) devices are pulse transformers with a soft magnetic material in the magnetic core for the purpose of matching impedance at the input / output terminals or maintaining electrical insulation. Pulse transformers have high inductance, i.e., high incremental permeability (μ Δ ) Here, incremental permeability is a value that indicates the permeability (ease of magnetization) of a magnetic core when a magnetic field is applied. Note that incremental permeability and effective permeability are synonymous, so in this specification they will be consistently referred to as incremental permeability.

[0003] Toroidal MnZn ferrite is commonly used for magnetic cores using soft magnetic materials. Among many soft magnetic materials, MnZn ferrite is particularly easy to obtain high magnetic permeability and high inductance. Furthermore, MnZn ferrite is inexpensive compared to metallic magnetic materials such as amorphous metals, and because it is an oxide, it does not rust and is stable.

[0004] However, since MnZn-based ferrite is an oxide magnetic material, it does not have a high Curie temperature and its magnetic properties change significantly with temperature fluctuations. Therefore, compared to metal magnetic materials, it has the disadvantage that it is difficult to obtain stable magnetic properties over a wide temperature range.

[0005] Pulse transformers are sometimes installed outdoors, such as when used in line termination devices, and the MnZn-based ferrites used in pulse transformers must have a high initial permeability (μi) over a wide temperature range, from low to high. In digital communication equipment, pulse transformers can become magnetized due to fluctuations in the positive / negative balance of the pulse voltage being transmitted, causing them to operate under a DC magnetic field. Even under such a DC magnetic field, a high inductance, i.e., a high incremental permeability, is required for signal conversion. In applications such as those described above, the magnitude of the DC magnetic field applied varies depending on the required inductance specification and usage, but a high incremental permeability is required at room temperature.

[0006] Pulse transformers have traditionally been used in many consumer devices, but in recent years, with the advancement of car networking, they have also begun to be used more in automobiles. Conventional consumer device applications were required to operate normally within temperature ranges such as 0 to 70°C, -40 to 85°C, or -40 to 105°C, but automotive applications require normal operation over a wider temperature range, such as -40 to 125°C or -50 to 150°C.

[0007] On the other hand, Ethernet devices also use PoE (Power over Ethernet) power supplies, such as PoE / PoE+ / PoE++, which directly supply the device's driving power in conjunction with the transmission signal. In this case, pulse transformers are used under conditions where a current greater than that of the signal transmission is superimposed. Furthermore, due to increased PoE power output and the increasing current caused by the spread of SiC and GaN semiconductors, peripheral components in the device generate heat, and the operating environment of pulse transformer cores is expected to shift to higher temperatures. Therefore, MnZn-based ferrites used in this application are required to have high inductance, i.e., high incremental permeability, at higher temperatures and under high magnetic field superimposition, even if they have a low initial permeability μi.

[0008] The MnZn ferrites used in conventional consumer devices are Fe ２ O ３MnZn-based ferrites are primarily composed of ZnO and MnO, and exhibit high permeability when the primary components are such that the magnetic anisotropy constant and magnetostriction constant are zero. For this reason, MnZn-based ferrites are used as small or thin magnetic cores for transformers, noise filters, and the like. Although it is difficult to obtain stable magnetic properties over a wide temperature range, methods have been proposed to achieve high incremental permeability when a DC magnetic field is applied in the temperature range of -40 to 85°C or -40 to 105°C in order to accommodate pulse transformers for consumer applications. In this specification, all values ​​of initial permeability and incremental permeability are expressed as a ratio (relative permeability) to the vacuum permeability μo.

[0009] Patent Documents 1, 2, and 3 propose ferrites having an incremental permeability of 2000 or more when a DC magnetic field is applied in the temperature range of -40 to 85°C. Patent Documents 4 and 5 propose MnZnCo-based ferrites having high initial permeability over a wide temperature range of about -20 to 150°C. Patent Document 6 proposes an MnZn-based ferrite having an initial permeability of 3000 or more at 23°C, a small rate of change in initial permeability between -20 and 150°C, and a saturation magnetic flux density of 540 mT or more at 23°C.

[0010] Patent Document 7 proposes an MnZn-based ferrite that has an incremental permeability of 400 or more in the temperature range of 0°C to 85°C and an incremental permeability of 700 or more at 65°C when a large DC magnetic field of 80 A / m is applied.

[0011] JP 2008-143745 A JP 2010-189247 A JP 2010-195596 A JP 2015-229625 A JP 2015-229626 A JP 2005-236069 A JP 2010-173899 A

[0012] However, the temperature range assumed in Patent Documents 1, 2, and 3 is -40 to 85°C, and an incremental permeability of 2300 or more cannot be obtained in the temperature range of -50 to 150°C. Although the temperature range assumed in Patent Documents 4 and 5 is wide, the MnZnCo-based ferrites in Patent Documents 4 and 5 are intended for noise filters, and the incremental permeability when a DC magnetic field is applied is not taken into consideration, making it impossible to obtain an incremental permeability of 2300 or more in the temperature range of -50 to 150°C. Patent Document 6 describes that the rate of change of the initial permeability is small in the temperature range of -20 to 150°C, but does not take into consideration the incremental permeability when a DC magnetic field is applied, making it impossible to obtain an incremental permeability of 2300 or more in the temperature range of -50 to 150°C.

[0013] In Patent Document 7, although a large DC magnetic field of 80 A / m is applied, the incremental permeability at 85°C is less than 1000 in all cases, and it is impossible to obtain an incremental permeability of a practical level of 1000 or more in a temperature range exceeding 85°C.

[0014] To date, many MnZn-based ferrites suitable for pulse transformers in consumer devices that can be used in a temperature range of -40 to 85°C have been proposed. However, no MnZn-based ferrite has been proposed that has excellent incremental permeability when a DC magnetic field is applied over a wide temperature range, such as that suitable for automotive LANs that can be used in a temperature range of -50 to 150°C.

[0015] Furthermore, no MnZn-based ferrite has been proposed that is suitable for PoE power supply and can be used in a temperature range exceeding 85° C., and that provides a high incremental magnetic permeability when a DC magnetic field of 50 A / m is applied.

[0016] Therefore, an object of the present invention is to provide an MnZn-based ferrite having a high incremental permeability over a wide temperature range, i.e., an incremental permeability of 2300 or more when a DC magnetic field of 25 A / m is applied in a temperature range of −50 to 150° C. Another object of the present invention is to provide an MnZn-based ferrite having an incremental permeability of 1000 or more when a DC magnetic field of 50 A / m is applied at 125° C.

[0017] In general, the incremental permeability of MnZn-based ferrite for general use is generally measured by applying a DC magnetic field of 25 A / m, but there are special cases in which a DC magnetic field of 33 A / m is applied depending on the use of the MnZn-based ferrite, as in Patent Documents 1, 2, and 3. In the present invention, the DC magnetic field applied when measuring the incremental permeability of MnZn-based ferrite for general use is 25 A / m. Also, the DC magnetic field applied when measuring the incremental permeability of MnZn-based ferrite for PoE power supply use is 50 A / m.

[0018] The inventors conducted extensive research to solve the above problems and have come to the following findings: By containing predetermined amounts of Fe and Zn as basic components, the remainder being Mn, and predetermined amounts of Si, Ca, Co, Ti, Nb, and V as minor components, it is possible to achieve an incremental permeability of 2300 or more when a DC magnetic field of 25 A / m is applied in the temperature range of -50 to 150°C. Furthermore, it is possible to achieve an incremental permeability of 1000 or more when a DC magnetic field of 50 A / m is applied at 125°C.

[0019] The present invention, which has been completed based on the above findings, has the following essential features.

[0020] [1] An MnZn-based ferrite consisting of a basic component, a subcomponent, and unavoidable impurities, wherein the basic components are Fe, ２ O ３ The total of Fe, Zn, and Mn calculated as ZnO and MnO is 100.0 mol%, ２ O ３ Zn: 10.1 mol % or more and less than 13.0 mol % in terms of ZnO; and Mn: the balance, and the minor components are ２ Ca: 300 ppm by mass or more and 1000 ppm by mass or less in terms of CaO; Co: Co ３ O ４ converted to 2100 mass ppm or more and 3500 mass ppm or less, Ti: TiO ２ converted to 2500 mass ppm or more and 4000 mass ppm or less, Nb: Nb２ O ５ converted to 50 mass ppm or more and 500 mass ppm or less, and V:V ２ O ５ The MnZn-based ferrite contains, in terms of Zn, Zn content of 0 ppm by mass or more and 500 ppm by mass or less.

[0021] [2] V ２ O ５ The MnZn-based ferrite according to [1] above, having a V content of 50 ppm by mass or more and 250 ppm by mass or less in terms of vanadium content.

[0022] [3] V ２ O ５ The MnZn-based ferrite according to [1] above, having a V content of 100 ppm by mass or more and 500 ppm by mass or less in terms of vanadium content.

[0023] [4] The MnZn-based ferrite according to [1] or [2] above, which has an incremental permeability of 2300 or more when a DC magnetic field of 25 A / m is applied in a temperature range of −50 to 150° C.

[0024] [5] The MnZn-based ferrite according to the above [1] or [3], which has an incremental permeability of 1000 or more when a DC magnetic field of 50 A / m is applied at 125°C.

[0025] According to the present invention, it is possible to obtain an MnZn-based ferrite having a high incremental permeability over a wide temperature range, i.e., an incremental permeability of 2300 or more when a DC magnetic field of 25 A / m is applied in the temperature range of −50 to 150° C. Furthermore, according to the present invention, it is possible to obtain an MnZn-based ferrite having an incremental permeability of 1000 or more when a DC magnetic field of 50 A / m is applied at 125° C.

[0026] FIG. 1A shows examples and comparative examples of the present invention in which the content of the basic component Fe is changed. FIG. 1B shows examples and comparative examples in which the content of the basic component Zn is changed. FIG. 1C shows examples and comparative examples in which the content of the basic component Zn is changed. FIG. 2A shows examples and comparative examples in which the content of the minor component Si is changed. FIG. 2B shows examples and comparative examples in which the content of the minor component Si is changed. FIG. 2C shows examples and comparative examples in which the content of the minor component Si is changed. FIG. 2C shows examples and comparative examples in which the content of the minor component Co was changed. FIG. 2D shows examples and comparative examples in which the content of the minor component Ti was changed. FIG. 2E shows examples and comparative examples in which the content of the minor component Nb was changed. FIG. 3 shows examples and comparative examples in which the content of the minor component V was changed. 4A is a graph showing the incremental permeability of an example of the present invention and a comparative example when a DC magnetic field of 50 A / m is applied in a temperature range of -50 to 125°C for an example of the present invention and a comparative example. FIG. 4A shows an example of the present invention and a comparative example in which the content of the minor component Ca is changed. FIG. 4B is a graph showing the incremental permeability of an example of the present invention and a comparative example in which the content of the minor component V is changed.

[0027] Hereinafter, an embodiment of the MnZn-based ferrite according to the present invention will be described. Note that the embodiment described below is an example of the present invention, and the configuration of the present invention is not limited to this specific example.

[0028] [MnZn-based ferrite] The MnZn-based ferrite according to the present invention comprises basic components, accessory components, and inevitable impurities, and the basic components are oxides of Fe, Zn, and Mn. Note that the mol% below indicates the composition ratio of the basic components.

[0029] (Main component) Fe ２ O ３ : 52.0 mol% or more and 53.6 mol% or less Fe contained in the MnZn ferrite ２ O ３ If the Fe content is less than 52.0 mol % in terms of Fe content, the incremental permeability will be significantly reduced. ２ O ３ On the other hand, the Fe content of the MnZn ferrite is preferably 52.0 mol % or more, and more preferably 52.6 mol % or more, calculated as Fe. ２ O ３ If the Fe content exceeds 53.6 mol % in terms of Fe content, the incremental magnetic permeability also decreases significantly. ２ O ３ The Fe content of the MnZn ferrite is 53.6 mol % or less, and preferably 53.1 mol % or less, calculated as Fe. ２ O ３ When the content of Fe is approximately 53.0 mol %, the magnetostriction constant λ becomes 0, and the incremental permeability when a DC magnetic field is applied becomes the highest. ２ O ３ It is thought that the further the Fe content is from the converted value of 53.0 mol%, i.e., from the case where λ = 0, the more the core expands and contracts due to the applied magnetic field, causing deformation, resulting in stress, which inhibits domain wall movement and significantly reduces the incremental permeability.

[0030] ZnO: 10.1 mol% or more, but less than 13.0 mol% It is known that the Curie temperature and secondary peak of MnZn-based ferrites change depending on the ratio of Fe to Zn. When Zn is contained in an amount of 10.1 mol% or more but less than 13.0 mol% in terms of ZnO, the Curie temperature is generally 200°C or higher, and a high incremental permeability can be obtained up to a high temperature range of 150°C. When the Zn contained in the MnZn-based ferrite is less than 10.1 mol% in terms of ZnO, the Curie temperature is high, but the initial permeability when no DC magnetic field is applied decreases, resulting in a decrease in the incremental permeability when a DC magnetic field is applied across the entire temperature range. Therefore, the Zn contained in the MnZn-based ferrite should be 10.1 mol% or more in terms of ZnO, preferably 10.2 mol% or more, more preferably 10.5 mol% or more, and even more preferably 11.0 mol% or more. On the other hand, when the Zn content in the MnZn-based ferrite is 13.0 mol % or more in terms of ZnO, the initial permeability increases when no DC magnetic field is applied, but the Curie temperature decreases, and the incremental permeability decreases when a DC magnetic field is applied at 150° C. Therefore, the Zn content in the MnZn-based ferrite is preferably less than 13.0 mol % and 12.9 mol % or less in terms of ZnO.

[0031] The Curie temperature of the MnZn ferrite according to the present invention is preferably 190° C. or higher, and more preferably 200° C. or higher, in order to obtain a high incremental permeability when a DC magnetic field is applied even at 150° C. There is no particular upper limit to the Curie temperature of the MnZn ferrite, but it is generally 230° C. or lower.

[0032] MnO: balance The MnZn ferrite according to the present invention contains Fe ２ O ３ The total amount of ZnO and MnO is 100.0 mol%. The Mn contained in the MnZn-based ferrite is preferably 33.9 mol% or more in terms of MnO. The Mn contained in the MnZn-based ferrite is preferably 37.0 mol% or less, and more preferably 36.9 mol% or less in terms of MnO.

[0033] (Sub-components) Next, the sub-components will be described. The MnZn ferrite according to the present invention contains Si, Ca, Co, Ti, and Nb as sub-components in addition to the above-mentioned basic components. It is further preferable that V is contained as a sub-component. These are SiO ２ , CaO, Co ３ O ４ , TiO ２ , Nb ２ O ５ , V ２ O ５ The secondary components of the composition of the present invention are present in the form of oxides such as SiO ２ , CaO, Co ３ O ４ , TiO ２ , and Nb ２ O ５ Alternatively, SiO ２ , CaO, Co ３ O ４ , TiO ２ , Nb ２ O ５ , and V ２ O ５ In the present invention, the content of the accessory component is the content relative to the basic component.

[0034] SiO ２ :30 mass ppm or more and 200 mass ppm or less SiO ２ is an additive that promotes the formation of grain boundaries, suppresses grain growth, increases resistivity, and reduces initial permeability. ２ By adding Si, the incremental permeability can be increased in a wide temperature range of -50 to 150°C. ２ If the content is less than 30 ppm by mass in terms of Si, the incremental permeability in the low temperature range and the high temperature range decreases, and it becomes difficult to obtain an incremental permeability of 2300 or more when a DC magnetic field is applied in a wide temperature range of −50 to 150° C. Therefore, the Si contained in the MnZn ferrite is preferably SiO ２The Si content in the MnZn-based ferrite is 30 ppm by mass or more, preferably 32 ppm by mass or more, and more preferably 35 ppm by mass or more, calculated as SiO ２ If the converted amount exceeds 200 mass ppm, the initial magnetic permeability drops significantly, and the incremental magnetic permeability also drops significantly accordingly, making it difficult to obtain an incremental magnetic permeability of 2300 or more in the wide temperature range of -50 to 150°C. Therefore, the Si contained in the MnZn ferrite is preferably SiO ２ The converted amount is 200 ppm by mass or less, preferably 190 ppm by mass or less, more preferably 150 ppm by mass or less, and even more preferably 49 ppm by mass or less.

[0035] CaO: 300 ppm by mass or more and 1000 ppm by mass or less CaO is an additive that promotes the formation of crystal grain boundaries, inhibits crystal grain growth, increases resistivity, and reduces initial permeability. However, by incorporating an appropriate amount of CaO into MnZn-based ferrite, it is possible to increase the incremental permeability over a wide temperature range of -50 to 150°C. If the Ca content of the MnZn-based ferrite is less than 300 ppm by mass, calculated as CaO, the incremental permeability in low and high temperature regions decreases, making it difficult to obtain an incremental permeability of 2300 or more when a DC magnetic field is applied over a wide temperature range of -50 to 150°C. Therefore, the Ca content of the MnZn-based ferrite is set to 300 ppm by mass or more, and preferably 390 ppm by mass or more, calculated as CaO. On the other hand, if the Ca content of the MnZn-based ferrite exceeds 1000 ppm by mass in terms of CaO, the initial permeability drops significantly, and accordingly the incremental permeability also drops significantly, making it difficult to obtain an incremental permeability of 2300 or more in the wide temperature range of −50 to 150° C. Therefore, the Ca content of the MnZn-based ferrite is set to 1000 ppm by mass or less in terms of CaO, preferably 950 ppm by mass or less, and more preferably 840 ppm by mass or less.

[0036] In MnZn-based ferrites for PoE power supply applications, where the incremental permeability when a DC magnetic field of 50 A / m is applied at 125° C. is important, a higher incremental permeability can be obtained by including more Ca. Therefore, in MnZn-based ferrites for PoE power supply applications, the amount of Ca contained in the MnZn-based ferrite is preferably 500 ppm by mass or more, more preferably 600 ppm by mass or more, even more preferably 700 ppm by mass or more, and most preferably 800 ppm by mass or more, calculated as CaO.

[0037] On the other hand, if the Ca content of the MnZn-based ferrite exceeds 1000 ppm by mass in terms of CaO, the initial permeability decreases excessively, and the incremental permeability also decreases accordingly, so that the incremental permeability when a DC magnetic field of 50 A / m is applied at 125° C. falls below 1000, which is not preferable. Therefore, even in MnZn-based ferrite for PoE power supply applications, the Ca content of the MnZn-based ferrite is set to 1000 ppm by mass or less, and preferably 950 ppm by mass or less, in terms of CaO.

[0038] Co ３ O ４ :2100 mass ppm or more and 3500 mass ppm or less Co ３ O ４ is an effective additive for improving the temperature dependency of the magnetic properties of MnZn ferrite. ３ O ４ By containing Co, the change in incremental permeability with respect to temperature when a DC magnetic field is applied becomes small, and the incremental permeability in both the low temperature and high temperature ranges is improved. ３ O ４ Since Co also has the effect of shifting the temperature dependency of magnetic permeability to the low temperature side, if the Co content is too low or too high, the balance of magnetic permeability between the low temperature range and the high temperature range is lost, the incremental magnetic permeability decreases in the low temperature range or the high temperature range, and it becomes impossible to obtain a high incremental magnetic permeability in the wide temperature range of -50 to 150°C. ３ O ４If the Co content is less than 2100 mass ppm in terms of mass, the maximum point of the temperature characteristic of the incremental magnetic permeability shifts to the high temperature side, and although the incremental magnetic permeability at high temperatures is high, the characteristics at low temperatures deteriorate, and it becomes impossible to obtain an incremental magnetic permeability of 2300 or more in the wide temperature range of -50 to 150°C. ３ O ４ On the other hand, the Co content of the MnZn ferrite is preferably 2100 mass ppm or more, and more preferably 2300 mass ppm or more, calculated as Co. ３ O ４ If the Co content exceeds 3500 mass ppm in terms of mass, the maximum point of the temperature characteristic of the incremental permeability shifts to the low temperature side, and although the low temperature characteristic of the incremental permeability is improved, the high temperature characteristic deteriorates, and it becomes impossible to obtain an incremental permeability of 2300 or more in the wide temperature range of -50 to 150°C. ３ O ４ The converted amount is 3500 mass ppm or less, and preferably 3200 mass ppm or less.

[0039] TiO ２ :2500 mass ppm or more and 4000 mass ppm or less TiO ２ is an effective additive for increasing the incremental permeability of MnZn ferrite when a DC magnetic field is applied. ２ does not have much effect on the size of the ferrite grain size, but an appropriate amount of TiO ２ By containing TiO, the coercive force of the ferrite decreases, and the gradient of the demagnetization curve changes in the region where a magnetic field equivalent to a DC magnetic field of 25 A / m is applied, thereby increasing the incremental permeability. ２ Since Ti also has the effect of shifting the temperature characteristics of the initial permeability and incremental permeability to the low temperature side, if the content is not appropriate, the low temperature characteristics and high temperature characteristics will deteriorate, and it will be impossible to obtain an incremental permeability of 2300 or more in the wide temperature range of -50 to 150°C. ２If the converted amount is less than 2500 mass ppm, the increase in incremental permeability is insufficient and the temperature characteristics shift to the high temperature side, making it impossible to obtain an incremental permeability of 2300 or more in the wide temperature range of -50 to 150°C. Therefore, Ti contained in MnZn ferrite is preferably TiO ２ The Ti content in the MnZn ferrite is 2500 mass ppm or more, preferably 2650 mass ppm or more, and more preferably 2800 mass ppm or more, calculated as TiO ２ If the converted amount exceeds 4000 mass ppm, the temperature characteristics shift to the low temperature side, and in the temperature range around -50°C, the incremental permeability when a DC magnetic field is applied also drops sharply, although the cause is unknown, so that an incremental permeability of 2300 or more cannot be obtained. ２ The converted amount is 4000 mass ppm or less, preferably 3950 mass ppm or less, more preferably 3500 mass ppm or less, and even more preferably 3300 mass ppm or less.

[0040] Nb ２ O ５ :50 mass ppm or more and 500 mass ppm or less Nb ２ O ５ Nb has the effect of suppressing the generation of coarse crystal grains, obtaining fine and uniform crystal grains, and increasing the resistivity. By containing an appropriate amount of Nb, the incremental permeability can be increased when a DC magnetic field is applied. The Nb contained in MnZn ferrite is Nb ２ O ５ If the Nb content is less than 50 ppm by mass, the generation of coarse crystal grains is not sufficiently suppressed, and the resistivity is also reduced, resulting in a decrease in the incremental permeability when a DC magnetic field is applied. ２ O ５ The Nb content in the MnZn-based ferrite is 50 ppm by mass or more, preferably 75 ppm by mass or more, more preferably 100 ppm by mass or more, and even more preferably 130 ppm by mass or more, calculated as Nb. ２ O ５If the Nb content exceeds 500 ppm by mass, the crystal grains become finer and the resistivity increases, which makes it difficult for the domain walls to move and reduces the initial permeability. ２ O ５ The converted amount is 500 ppm by mass or less, preferably 475 ppm by mass or less, and more preferably 400 ppm by mass or less.

[0041] V ２ O ５ :0 mass ppm or more and 500 mass ppm or less V ２ O ５ Also, Nb ２ O ５ Similarly, Nb is an additive that has the effect of suppressing the generation of coarse crystal grains, obtaining fine and uniform crystal grains, and increasing the resistivity. By including Nb and an appropriate amount of V, the incremental permeability can be suitably increased when a DC magnetic field is applied. Therefore, for general applications in the temperature range of -50 to 150°C, the V contained in MnZn ferrite is ２ O ５ is 0 mass ppm or more, preferably 50 mass ppm or more, and more preferably 55 mass ppm or more. In addition, in PoE power supply applications where the incremental magnetic permeability when a DC magnetic field of 50 A / m is applied at 125°C is important, V contained in the MnZn-based ferrite is ２ O ５ is 0 mass ppm or more, preferably 100 mass ppm or more, and more preferably 150 mass ppm or more.

[0042] On the other hand, in any application, the V contained in the MnZn ferrite is V ２ O ５ If the V content exceeds 500 ppm by mass, the crystal grains become finer and the resistivity increases, which makes it difficult for the domain walls to move and reduces the initial permeability. This also reduces the incremental permeability. ２ O ５The V content of the MnZn ferrite for PoE power supply applications is 500 mass ppm or less, preferably 490 mass ppm or less, more preferably 480 mass ppm or less, and even more preferably 250 mass ppm or less. ２ O ５ is 500 mass ppm or less, and preferably 400 mass ppm or less.

[0043] (Inevitable Impurities) The composition of the MnZn-based ferrite of the present invention is composed of inevitable impurities other than the basic components and minor components. Examples of inevitable impurities include P, B, S, Cl, and K, and the total content of these inevitable impurities is controlled to 500 ppm by mass or less. The total content of inevitable impurities is preferably 100 ppm by mass or less, and more preferably 50 ppm by mass or less.

[0044] (Initial Permeability When a DC Magnetic Field Is Not Applied) When a DC magnetic field is applied to MnZn-based ferrite, the initial permeability decreases, i.e., the incremental permeability also decreases. Therefore, in order to obtain a high incremental permeability, it is important to maintain a high initial permeability when a DC magnetic field is not applied. For general-purpose MnZn-based ferrites in the temperature range of -50 to 150°C, if the initial permeability at 23°C when no DC magnetic field is applied is 3500 or more, a high incremental permeability of 2300 or more can be suitably obtained over a wide temperature range of -50 to 150°C. Therefore, it is preferable that the initial permeability of MnZn-based ferrite at 23°C when no DC magnetic field is applied is 3500 or more. On the other hand, there is no particular upper limit to the initial permeability at 23°C when no DC magnetic field is applied, but it is generally 5000 or less.

[0045] (Incremental permeability when a DC magnetic field of 25 A / m is applied in a temperature range of -50 to 150°C) When the MnZn-based ferrite has the above composition, the incremental permeability when a DC magnetic field of 25 A / m is applied in a temperature range of -50 to 150°C can be made 2300 or more. There is no particular upper limit to the incremental permeability when a DC magnetic field of 25 A / m is applied in a temperature range of -50 to 150°C, but it is generally 4500 or less.

[0046] (Incremental permeability when a DC magnetic field of 50 A / m is applied at 125°C, for PoE power supply applications) In MnZn-based ferrite, the incremental permeability drops significantly, especially in the high temperature range, when the applied DC magnetic field is increased, but when the MnZn-based ferrite has the above composition, the incremental permeability when a DC magnetic field of 50 A / m is applied at 125°C can be made 1000 or more. There is no particular upper limit to the incremental permeability when a DC magnetic field of 50 A / m is applied at 125°C, but it is generally 2000 or less.

[0047] [Method for producing MnZn-based ferrite] Next, a method for producing the MnZn-based ferrite according to the present invention will be described. As a method for producing the MnZn-based ferrite according to the present invention, a known general production method can be used.

[0048] An example of a method for producing MnZn-based ferrite according to the present invention is as follows. First, Fe, which is the main component, is ２ O ３ , ZnO and Mn ３ O ４ (The composition ratio is Mn ３ O ４ The powder raw materials (treated in terms of MnO rather than MnO) are weighed to the content specified in the present invention and mixed in an attritor or ball mill to obtain a mixed powder. The mixing method may be either a dry or wet method. The mixed powder is then calcined at 800 to 1000°C to obtain a calcined powder. The calcined powder is then wet-pulverized in an attritor or ball mill to a particle size of approximately 0.8 to 1.6 μm to obtain a pulverized powder. At this time, oxides of the minor components are added and pulverized to obtain the content specified in the present invention. The pulverization process is homogenized to prevent bias in the concentration of the minor components. An organic binder such as polyvinyl alcohol is added to the resulting pulverized powder, and the powder is granulated using a spray dryer or the like to obtain a granulated powder. The granulated powder is then filled into a mold of a predetermined shape and molded to obtain a compact. The resulting compact is fired at approximately 1100 to 1400°C to obtain an MnZn-based ferrite.

[0049] The MnZn-based ferrite thus obtained exhibits high incremental permeability of 2300 or more in a wide temperature range of -50 to 150°C when a DC magnetic field of 25 A / m is applied, and also exhibits high incremental permeability of 1000 or more when a DC magnetic field of 50 A / m is applied at 125°C.

[0050] (Improved Variability) Conventional MnZn-based ferrites for pulse transformers require a low upper temperature limit of 85°C, and thus require high initial and incremental permeabilities. Therefore, compositions with a high ZnO molar ratio and high initial permeability are often used. It is generally known that Zn is prone to evaporation when fired at high temperatures. When small ferrite cores are molded and fired using ferrite powder with a high initial permeability (high ZnO molar ratio), evaporation of Zn from the core surface is often a problem. Due to the evaporation of Zn, the composition of the ferrite core surface differs slightly from that of the ferrite core interior. Therefore, using ferrite powder with a high ZnO molar ratio increases the variation in the surface composition, resulting in increased variations in the initial and incremental permeabilities. In contrast, the MnZn-based ferrite of the present invention uses a composition with a high Curie temperature (low ZnO molar ratio) to enable use over a wide temperature range from -50°C to 150°C. In this way, when a ferrite powder with a low ZnO molar ratio is used, evaporation of Zn from the ferrite core surface is suppressed, so the difference in composition between the core surface and the interior is small, and the variations in initial permeability and incremental permeability are also small. The ferrite of the present invention has a composition with a lower ZnO molar ratio than conventional MnZn-based ferrites for pulse transformers, and therefore has the advantage of reducing variations in magnetic properties.

[0051] Fe, the basic component of MnZn ferrite ２ O ３ , ZnO, and Mn ３ O ４Each raw material powder was weighed so that the composition ratios (composition ratios are converted to MnO) would be as shown in Tables 1 to 3. High purity raw material powders were used for each raw material powder. These raw material powders were mixed and pulverized in a ball mill for 16 hours, and then calcined in air at 925°C for 3 hours to obtain calcined powder. Next, SiO was added to this calcined powder so that the content would be as shown in Tables 1 to 3. ２ , CaCO ３ , Co ３ O ４ , TiO ２ , and Nb ２ O ５ In some cases shown in Table 3, V ２ O ５ The mixture was then pulverized in a ball mill for 12 hours to obtain a pulverized powder. Polyvinyl alcohol was then added to the pulverized powder, which was then granulated and molded into a toroidal core under a pressure of 118 MPa. The compact was then placed in a sintering furnace and sintered at a maximum temperature of 1350°C to obtain a sintered sample (ferrite core) measuring 30.5 mm in total, 19 mm in inner diameter, and 6.5 mm in height.

[0052] Each ferrite core thus obtained was wound with 20 turns, and its magnetic properties were measured using a Precision LCR Meter E4980A (Keysight Technologies). The initial permeability (without a DC magnetic field applied: 0 A / m) was measured at 23°C and a frequency of 100 kHz. The incremental permeability (with a DC magnetic field applied: 25 A / m) was measured at temperatures of -50°C, 0°C, 23°C, 50°C, 100°C, and 150°C and a frequency of 100 kHz. Tables 1 to 3 show the measurement results, and Figures 1A, 1B, 2A to 2E, and 3 show graphs of the measurement results.

[0053] Similarly, as shown in Table 4, the amount of CaO added and V ２ O ５ Ferrite cores were fabricated with different amounts of additives. Table 4, Figures 4A and 4B show the results of measuring the incremental permeability at a frequency of 100 kHz at temperatures of -50°C, 0°C, 23°C, 50°C, 75°C, 100°C and 125°C while applying a DC magnetic field of 50 A / m.

[0054] The contents of P, B, S, Cl, K and other unavoidable impurities were quantified in accordance with JIS K 0102 (ICP mass spectrometry) and confirmed to be 500 ppm by mass or less in total. The measurement results are shown in the tables.

[0055]

[0056]

[0057]

[0058]

[0059] From the results of Examples 1 to 10 and Comparative Examples 1 to 4 shown in Table 1 and FIGS. 1A and 1B, it can be seen that the basic composition of Fe is ２ O ３ It can be seen that when the Zn content is 52.0 mol % or more and 53.6 mol % or less in terms of ZnO, and when the Zn content is 10.1 mol % or more and less than 13.0 mol % in terms of ZnO, an incremental permeability of 2300 or more can be obtained in the temperature range of -50 to 150°C when a DC magnetic field of 25 A / m is applied.

[0060] From the results of Examples 11 to 15 and Comparative Examples 5 and 6 shown in Table 2 and FIG. 2A, it can be seen that the secondary component Si is SiO ２ If the converted content is 30 mass ppm or more and 200 mass ppm or less, it can be seen that when a DC magnetic field of 25 A / m is applied, an incremental permeability of 2300 or more can be obtained in the temperature range of -50 to 150°C.

[0061] From the results of Examples 11 and 16 to 19 and Comparative Examples 7 and 8 shown in Table 2 and FIG. 2B, it can be seen that when the auxiliary component Ca is 300 mass ppm or more and 1000 mass ppm or less in terms of CaO, an incremental permeability of 2300 or more can be obtained in the temperature range of −50 to 150° C. when a DC magnetic field of 25 A / m is applied.

[0062] From the results of Examples 11 and 20 to 23 and Comparative Examples 9 and 10 shown in Table 2 and FIG. 2C, it can be seen that the auxiliary component Co ３ O ４It can be seen that if the converted content is in the range of 2100 mass ppm or more and 3500 mass ppm or less, an incremental permeability of 2300 or more can be obtained in the temperature range of -50 to 150°C when a DC magnetic field of 25 A / m is applied.

[0063] From the results of Examples 11 and 24 to 26 and Comparative Examples 11 and 12 shown in Table 2 and FIG. 2D, it can be seen that the auxiliary component Ti is TiO ２ It can be seen that if the converted content is in the range of 2500 mass ppm to 4000 mass ppm, an incremental permeability of 2300 or more can be obtained in the temperature range of -50 to 150°C when a DC magnetic field of 25 A / m is applied.

[0064] From the results of Examples 11 and 27 to 30 and Comparative Examples 13 and 14 shown in Table 2 and FIG. 2E, it can be seen that the auxiliary component Nb is ２ O ５ It can be seen that if the converted content is in the range of 50 mass ppm to 500 mass ppm, an incremental permeability of 2300 or more can be obtained in the temperature range of -50 to 150°C when a DC magnetic field of 25 A / m is applied.

[0065] From the results of Examples 31 to 35 and Comparative Example 15 shown in Table 3 and FIG. 3, it can be seen that the subcomponent V is V ２ O ５ If the content is 500 mass ppm or less in terms of mass conversion, when a DC magnetic field of 25 A / m is applied, an incremental magnetic permeability of 2300 or more can be obtained in the temperature range of -50 to 150°C, and V ２ O ５ V than without additives ２ O ５ It can be seen that the addition of Fe results in a higher incremental permeability in both the low and high temperature ranges.

[0066] From the results of Examples 36 to 39 and Comparative Example 16 shown in Table 4 and FIG. 4A, it can be seen that when the auxiliary component Ca is 300 mass ppm or more and 1000 mass ppm or less in terms of CaO, an incremental permeability of 1000 or more can be obtained at 125°C when a DC magnetic field of 50 A / m is applied.

[0067] From the results of Examples 39 to 46 and Comparative Example 17 shown in Table 4 and FIG. 4B, it can be seen that the subcomponent V is V ２ O ５If the content is 500 mass ppm or less in terms of mass conversion, an incremental magnetic permeability of 1000 or more can be obtained at 125°C when a DC magnetic field of 50 A / m is applied, and V ２ O ５ V than without additives ２ O ５ It can be seen that the addition of Cr results in a higher incremental magnetic permeability at 125°C.

[0068] (Example Variation Investigation) For Example 47 and Comparative Example 18 shown in Table 5, ferrite pulverized powder was prepared in the same manner as described above. Polyvinyl alcohol was added to the pulverized powder and granulated. A pressure of 118 MPa was applied to form a toroidal core, resulting in a compact. The compact was then placed in a sagger and loaded into a firing furnace. Sintering was performed at a maximum temperature of 1350°C to produce 100 sintered samples (cores) measuring an outer diameter of 6.0 mm, an inner diameter of 3.0 mm, and a height of 4.0 mm. For each core obtained, the initial permeability at 23°C and the incremental permeability when a DC magnetic field of 25 A / m was applied at -40°C were measured using the method described above, and the standard deviation σ for each was calculated from the measurement results. Table 5 shows the magnetic properties (initial permeability and incremental permeability, which are the average values ​​of the 100 measured samples) and the standard deviation σ.

[0069] Here, Comparative Example 18 had the same components as Sample No. 1-5 (Invention Example of Patent Document 1) in Patent Document 1. Although there is a difference in the initial permeability between Inventive Example 47 and Comparative Example 18, the incremental permeability when a DC magnetic field of 25 A / m is applied at −40° C. is almost the same.

[0070]

[0071] As shown in Table 5, in the case of Example 47, the standard deviation σ is smaller for both the initial permeability at 23° C. and the incremental permeability when a DC magnetic field of 25 A / m is applied at −40° C. than for Comparative Example 18. This shows that the composition of the present invention with a low ZnO molar ratio has smaller variations in magnetic properties than the conventional composition with a high ZnO molar ratio, and is therefore more preferable.

[0072] According to the present invention, it is possible to obtain an MnZn-based ferrite that has a high incremental permeability over a wide temperature range, which is suitable for electronic components such as pulse transformers, i.e., an incremental permeability of 2300 or more when a DC magnetic field of 25 A / m is applied in the temperature range of -50 to 150°C. Also, it is possible to obtain an MnZn-based ferrite that has an incremental permeability of 1000 or more when a DC magnetic field of 50 A / m is applied at 125°C. This makes it possible to accommodate automotive applications and PoE power supply applications that require a wider temperature range than conventional applications.

Claims

1. A MnZn-based ferrite consisting of a basic component, a subcomponent, and unavoidable impurities, wherein the basic components are Fe, ２ O ３ The total of Fe, Zn, and Mn calculated as Fe, ZnO, and MnO is 100.0 mol%, ２ O ３ Zn: 10.1 mol % or more and less than 13.0 mol % in terms of ZnO; and Mn: balance. ２ Ca: 300 ppm by mass or more and 1000 ppm by mass or less in CaO conversion; Co: Co ３ O ４ 2100 mass ppm or more and 3500 mass ppm or less in terms of Ti: TiO ２ 2500 mass ppm or more and 4000 mass ppm or less in terms of Nb: Nb ２ O ５ In terms of V, 50 ppm by mass or more and 500 ppm by mass or less, and V: V ２ O ５ The MnZn-based ferrite contains 0 ppm by mass or more and 500 ppm by mass or less.

2. V ２ O ５ The MnZn-based ferrite according to claim 1, wherein the content of V in terms of vanadium is 50 ppm by mass or more and 250 ppm by mass or less.

3. V ２ O ５ The MnZn-based ferrite according to claim 1, wherein the content of V in terms of vanadium is 100 ppm by mass or more and 500 ppm by mass or less.

4. The MnZn-based ferrite according to claim 1 or 2, which has an incremental permeability of 2300 or more when a DC magnetic field of 25 A / m is applied in the temperature range of -50 to 150°C.

5. The MnZn-based ferrite according to claim 1 or 3, which has an incremental permeability of 1000 or more when a DC magnetic field of 50 A / m is applied at 125° C.

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