(19)
(11)EP 3 187 475 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
29.07.2020 Bulletin 2020/31

(21)Application number: 15835796.2

(22)Date of filing:  31.08.2015
(51)International Patent Classification (IPC): 
C04B 35/38(2006.01)
H01F 1/34(2006.01)
(86)International application number:
PCT/JP2015/074622
(87)International publication number:
WO 2016/032001 (03.03.2016 Gazette  2016/09)

(54)

MnZn-BASED FERRITE AND METHOD FOR MANUFACTURING THE SAME

MNZN-FERRIT UND VERFAHREN ZUR HERSTELLUNG DAVON

FERRITE MNZN ET PROCÉDÉ POUR LA FABRIQUER


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 29.08.2014 JP 2014174996

(43)Date of publication of application:
05.07.2017 Bulletin 2017/27

(73)Proprietor: Hitachi Metals, Ltd.
Tokyo 108-8224 (JP)

(72)Inventors:
  • TADA, Tomoyuki
    Mishima-gun Osaka 618-0013 (JP)
  • MIYOSHI, Yasuharu
    Mishima-gun Osaka 618-0013 (JP)
  • KOYUHARA, Norikazu
    Mishima-gun Osaka 618-0013 (JP)

(74)Representative: Cabinet Beaumont 
4, Place Robert Schuman B.P. 1529
38025 Grenoble Cedex 1
38025 Grenoble Cedex 1 (FR)


(56)References cited: : 
EP-A2- 1 560 229
JP-A- 2001 220 146
JP-A- 2007 031 240
JP-A- 2007 070 209
JP-A- 2008 169 072
US-A1- 2009 242 827
JP-A- H06 140 231
JP-A- 2007 031 240
JP-A- 2007 051 052
JP-A- 2007 150 006
JP-A- 2009 227 554
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    [Technical Field]



    [0001] The present invention relates to a MnZn-based ferrite used in an electronic component such as a transformer, an inductor, a reactor or a choke coil which is used for various kinds of power supply devices, and a method for manufacturing the MnZn-based ferrite.

    [Background Art]



    [0002] A device such as a high-power electric motor, a charger is disposed in an electric vehicle that is one of electric transportation equipment such an EV (Electric Vehicle), a PHEV (Plug-in Hybrid Electric Vehicle) which spreads rapidly in recent years, and such a device is provided with an electronic component which withstands a high voltage and a large current. The electronic component includes a coil and a magnetic core as a basic configuration, and the magnetic core is comprised of a magnetic material such as a MnZn-based ferrite. Document JP 2007/150006 discloses a magnetic property recovery method of ferrite core. Document US 2009/242827 discloses a ferrite sintered body and a manufacturing method therefor.

    [0003] In such an application, various mechanical and electric loading conditions occur in the electronic component during running, and a used environmental temperature is also various. In the electronic component used in a consumer-electronics device, a MnZn-based ferrite is used whose composition is designed so that a minimum temperature of a magnetic core loss (also called a power loss) is 100 °C or lower for example, however, it is often the case that the MnZn-based ferrite is used that has the minimum temperature of the magnetic core loss Pcv reaching a high temperature over 100 °C, based on the assumption that the MnZn-based ferrite is used under the high-temperature environment for on-vehicle use. Moreover, a low magnetic core loss is required in a wide temperature range.

    [0004] Generally, the magnetic core loss Pcv of the ferrite consists of a hysteresis loss Ph, an eddy current loss Pe and a residual loss Pr. The hysteresis loss Ph increases in proportion to a frequency due to a direct-current hysteresis, and the eddy current loss Pe increases in proportion to the square of a frequency due to an electromotive force which is generated by an eddy current occurring according to an electromagnetic induction action. The residual loss Pr is the remaining loss which is related to a factor such as a domain wall resonance, and is revealed on a frequency of 500 kHz or more. That is, the hysteresis loss Ph, the eddy current loss Pe and the residual loss Pr change depending on a frequency, and a ratio thereof accounting for the whole magnetic core loss also changes depending on a frequency band.

    [0005] The magnetic core loss of the MnZn-based ferrite has a temperature dependence, has the low hysteresis loss at a temperature where a crystal magnetic anisotropy constant K1 is zero, and has a minimum value at that temperature. An initial permeability µi is the maximum at that temperature, therefore, it is also called the secondary peak of the initial permeability µi. Since the magnetic core loss has a minimum value concerning the temperature, usually, a temperature at which the magnetic core loss is the minimum is adjusted with the crystal magnetic anisotropy constant K1 in anticipation of the generation of heat by the magnetic core loss, and the temperature is set to a temperature slightly higher than an environmental temperature to which the electronic component is exposed, which prevents the ferrite from losing magnetism due to thermal run-away.

    [0006] The temperature at which the magnetic core loss is the minimum, i.e., the temperature at which the crystal magnetic anisotropy constant K1 is zero, can be changed according to the sum obtained by appropriately adjusting an amount of a metal ion having a positive crystal magnetic anisotropy constant K1 and an amount of a metal ion having a negative crystal magnetic anisotropy constant K1 among metal ions mainly constituting spinel in the MnZn-based ferrite. For the metal ions constituting spinel, the metal ions having the positive K1 are Fe2+ and Co2+ and the like and the metal ions having the negative K1 are Fe3+, Mn2+, Ni2+, and the like. Although the change of the temperature at which the magnetic core loss is the minimum can be comparatively easy by adjusting the metal ions such as Fe2+, Fe3+, Zn2+, and Mn2+, it is difficult to improve the temperature dependence of the magnetic core loss based on such a process only. Thus, Co2+ is employed that has a crystal magnetic anisotropy constant and a magnetostriction constant adequately larger than those of Fe2+, which improves the temperature dependence of the magnetic core loss.

    [0007] Patent Document 1 discloses a MnZn-based ferrite which contains Fe2O3: 52.0-55.0 mol%, MnO: 32.0-44.0 mol% and ZnO: 4.0-14.0 mol% as a main component and contains CaO: 200-1000 ppm, SiO2: 50-200 ppm, Bi2O3: 500 ppm or less, Ta2O5: 200-800 ppm and CoO: 4000 ppm or less as a sub component. In the MnZn-based ferrite disclosed in Patent Document 1, the balance of the metal ions is adjusted with a composition amount of Fe2O3, CoO, ZnO, MnO, etc., and the temperature at which the magnetic core loss is the minimum is changed, which improves the temperature dependence of the magnetic core loss, while Bi2O3 is added to obtain a MnZn-based ferrite whose magnetic core loss is low in a wider temperature range.

    [0008] Such an employment of Co2+ is effective in the improvement of the temperature dependence of the magnetic core loss. However, the divalent metal ion such as Fe2+ and Co2+ is easy to move via a lattice defect to cause the increase of magnetic anisotropy, and also time-dependent change of a magnetic property such as the increase of the magnetic core loss and the decline of a magnetic permeability. Especially, it is known that the MnZn-based ferrite containing Co has such a marked tendency and the time-dependent change is accelerated under the high-temperature environment. Accordingly, the MnZn-based ferrite used for an electronic component which is easy to be exposed to a high temperature is required to further lower the magnetic core loss and to suppress control the time-dependent change of the magnetic property.

    [0009] As a method of suppressing the time-dependent change of the magnetic property of the MnZn-based ferrite, Patent Document 2 and Patent Document 3 disclose to control an ambient oxygen concentration in calcination. The calcination includes a temperature rising step, a high temperature maintaining step and a temperature falling step as a basic process, and in Patent document 2 and Patent Document 3 the ambient oxygen concentration is strictly controlled at the high temperature maintaining step and the temperature falling step especially.

    [Prior Art Document]


    [Patent Document]



    [0010] 

    [Patent Document 1] Japanese Patent Laid-Open Publication No. 2001-220146

    [Patent Document 2] Japanese Patent Laid-Open Publication No. 2004-292303

    [Patent Document 3] Japanese Patent Laid-Open Publication No. 2007-70209

    [Patent Document 4] JP 2007/150006 A;

    [Patent Document 5] US2009/242827


    [Summary of Invention]


    [Problems to be Solved by Invention]



    [0011] Although Patent Document 1 does not describe the time-dependent change of the magnetic property, according to the present inventors' study, it is revealed that in a case of the composition containing Bi like the MnZn-based ferrite described in Patent Document 1, there is a case where the ambient oxygen concentration is controlled so as to suppress the time-dependent change of the magnetic property, thereby causing the increase of the magnetic core loss. Accordingly, an object of the present invention is to provide a MnZn-based ferrite which allows to have a low magnetic core loss and to suppress the time-dependent change of the magnetic property under the high-temperature environment and the increase of the magnetic core loss, and a method for manufacturing the same.

    [Means for Solving Problems]



    [0012] A first aspect as defined in claim 1, is a MnZn-based ferrite containing Fe, Mn and Zn as a main component and containing Si, Ca, Co and Bi, and at least one of Ta and Nb, and at least one of Ti and Sn as a sub component, wherein given that a total amount is 100 mol% when the main component includes Fe2O3, ZnO and MnO respectively, Fe ranges from 53.25 mol% or more to 54.00 mol% or less on the basis of Fe2O3, Zn ranges from 2.50 mol% or more to 8.50 mol% or less on the basis of ZnO and Mn is the remainder on the basis of MnO, and at a frequency of 100 kHz in a maximum magnetic flux density of 200 mT, a magnetic core loss (Pcv130A) at 130 °C is 400 kW/m3 or less, and a rate of change Ps of the magnetic core loss is 5 % or less that is expressed in the following formula using the magnetic core loss (Pcv130B) at 130 °C after maintaining the MnZn-based ferrite at 200 °C for 96 hours.



    [0013] In the first aspect, Si ranges from 0.003 mass% or more to 0.015 mass% or less on the basis of SiO2, Ca ranges from 0.06 mass% or more to 0.3 mass% or less on the basis of CaCO3, Co ranges from 0.16 mass% or more to 0.4 mass% or less on the basis of Co3O4, and Bi ranges from 0.0075 mass% or more to 0.04 mass% or less on the basis of Bi2O3, and in a case where Ta or Nb is contained independently, Ta ranges from 0.015 mass% or more to 0.04 mass% or less on the basis of Ta2O5 or Nb ranges from 0.015 mass% or more to 0.04 mass% or less on the basis of Nb2O5, and in a case where Ti or Sn is contained independently, Ti ranges from 0.02 mass% or more to 0.2 mass% or less on the basis of TiO2 or Sn ranges from 0.02 mass% or more to 0.2 mass% or less on the basis of SnO2, and in a case where both of Ta and Nb are contained, the converted total amount of Ta2O5 and Nb2O5 ranges from 0.015 mass% or more to 0.04 mass% or less, and in a case where both of Ti and Sn are contained, the converted total amount of TiO2 and SnO2 ranges from 0.02 mass% or more to 0.2 mass% or less.

    [0014] In the MnZn-based ferrite of the first aspect, it is preferred that the magnetic core loss between 100°C and 150 °C is 500 kW/m3 or less and the minimum temperature of the magnetic core loss ranges from 110 °C to 150 °C.

    [0015] In the MnZn-based ferrite of the first aspect, it is preferred that the magnetic core loss (Pcv130B) at 130 °C after maintaining the MnZn-based ferrite at 200 °C for 96 hours is 400 kW/m3 or less.

    [0016] A second aspect as defined in claim 4, is a method for manufacturing a MnZn-based ferrite, comprising a calcination step of molding an oxide powder of the main component and the sub component specified in the first aspect to obtain a molded body and calcinating the molded body, wherein the calcination step includes a temperature rising step, a high temperature maintaining step and a temperature falling step, and a temperature at the high temperature maintaining step ranges from 1250 °C to 1400 °C, and an oxygen concentration in an atmosphere at the high temperature maintaining step is 0.7 % or less in a volume percent, and an oxygen concentration at 1200 °C is 0.5 % or less and an oxygen concentration at 1100 °C is 0.1 % or less at the temperature falling step.

    [Effects of Invention]



    [0017] According to the present invention, the present invention can provide a MnZn-based ferrite which allows to have a low magnetic core loss and to suppress the time-dependent change of the magnetic property under the high-temperature environment and the increase of the magnetic core loss, and a method for manufacturing the same.

    [Brief Description of Drawings]



    [0018] 

    FIG. 1 is a view showing a temperature condition of a calcination step according to one embodiment of the present invention.

    FIG. 2 is a view showing the relation between an amount of Bi2O3 of a MnZn-based ferrite and magnetic core losses before and after maintaining at a high temperature.

    FIG. 3 is a view showing the relation between amounts of TiO2 and SnO2 of the MnZn-based ferrite and the magnetic core losses before and after maintaining at the high temperature.


    [Mode for Carrying out Invention]



    [0019] The following description specifically explains a MnZn-based ferrite according to one embodiment of the present invention, a magnetic core with the same, and a method for manufacturing the same.

    (Composition of MnZn-based ferrite)



    [0020] In order to reduce a magnetic core loss Pcv at a desired temperature, it is required to optimize a composition and to appropriately adjust an amount of a metal ion having a positive crystal magnetic anisotropy constant K1 and an amount of a metal ion having a negative crystal magnetic anisotropy constant K1, the metal ions constituting spinel. However, there is little degree of a freedom of the composition selection due to the restriction of the required magnetic property such as a saturation magnetic flux density Bs, a curie temperature Tc, an initial magnetic permeability µi other than the magnetic core loss Pcv. In a composition containing much Fe2O3, a magnetization curve obtained by applying an external magnetic field is narrow near the origin, and becomes a so-called perminvar type easily, and the magnetic core loss increases. Then, from the above viewpoint, in the present invention, a composition range is selected that as a main component Fe2O3 ranges from 53.25 mol% or more to 54.00 mol% or less, ZnO ranges from 2.50 mol% or more to 8.50 mol% or less and MnO is the remainder in a manner such that the minimum temperature of the magnetic core loss ranges from 110 °C to 150 °C. Note that in the present invention, the main component means an element or a compound mainly constituting a spinel ferrite, while the sub component means an element or a compound subsidiarily used for the formation and a part thereof contains an element which dissolves to the spinel ferrite. Moreover, the sub component further contains an element constituting the spinel ferrite like Co because a content thereof is low as compared with that of the main component.

    [0021] In the MnZn-based ferrite of the present invention, the MnZn-based ferrite contains Fe, Mn and Zn as the main component and contains Si, Ca, Co and Bi, and at least one of Ta and Nb, and at least one of Ti and Sn as the sub component.

    [0022] In the MnZn-based ferrite of the present invention, Si and Ca are contained in a predetermined range, Si and Ca of a high resistance are present in a grain boundary of a ferrite sintered body (for example, a magnetic core) obtained by calcinating the MnZn-based ferrite, and then a crystal grain is insulated to exert an effect such as the increase of a volume resistivity ρ and the reduction of a relative loss factor tanδ/µi. In the present invention, Si is contained that ranges from 0.003 mass% or more to 0.015 mass% or less on the basis of SiO2, and Ca is contained that ranges from 0.06 mass% or more to 0.3 mass% or less on the basis of CaCO3. Furthermore preferably, Ca is contained that ranges from more than 0.06 mass% to 0.3 mass% or less on the basis of CaCO3.

    [0023] Although Si is entirely segregated in the grain boundary and its triple point, there is a case where Ca dissolves to a spinel phase in the middle of the calcination step, and a part thereof dissolves and remains in the crystal grain even after the calcination step. When Ca which dissolves to the spinel phase increases, it is possible that the resistance in the crystal grain is increased and the volume resistivity ρ is increased, but Ca in the gain boundary decreases relatively. In order to obtain the high volume resistivity ρ so as to achieve a MnZn-based ferrite whose loss is low, it is effective that Ca which dissolves to the spinel phase and Ca which is segregated to the grain boundary are appropriately adjusted to increase the resistance in the crystal grain and to form the grain boundary of a high resistance. Such an adjustment can be performed with the later-described calcination temperature and the calcination atmosphere control.

    [0024] By further adding Co2+ in addition to Fe2+, it is possible that the temperature change of the loss is reduced, the loss is low in a wide temperature range, and a relative temperature coefficient αµir is reduced. Moreover, by adding Co2+, a residual magnetic flux density Br can be reduced, which can further reduce the hysteresis loss Ph. However, such an effect by Co2+ may cause the magnetic core loss to deteriorate because in a case where the content of Co is excessive, the magnetization curve becomes the perminvar type easily and the crystal magnetic anisotropy constant becomes too high toward a positive side on a low temperature side. For this reason, in the present invention, Co is contained that ranges from 0.16 mass% or more to 0.4 mass% or less on the basis of Co3O4. Furthermore preferably, Co is contained that ranges from 0.16 mass% or more to less than 0.4 mass% on the basis of Co3O4.

    [0025] Bi is entirely segregated in the grain boundary and its triple point and contributes to the forming of the grain boundary of a high resistance. Bi also functions as a sintering accelerator and densifies a crystal structure. A crystal grain size increases, the hysteresis loss decreases, and the magnetic core loss is reduced. Much Bi causes an abnormal sintering to increase the magnetic core loss. Bi is contained that ranges from 0.0075 mass% or more to 0.04 mass% or less on the basis of Bi2O3. Preferably, Bi is contained that ranges from 0.01 mass% or more to less than 0.04 mass% on the basis of Bi2O3.

    [0026] Ta and Nb are Group Va elements, and these components appear in a grain boundary layer with Si and Ca, increase a resistance of the grain boundary layer, and then contributes to the reduction of the loss. Ta or Nb may be contained independently, or both of them may be contained. In a case where Ta or Nb is contained independently, Ta or Nb is contained that ranges from 0.015 mass% or more to 0.04 mass% or less on the basis of Ta2O5 or Nb2O5 and in a case where both of Ta and Nb are contained, a total amount of Ta2O5 and Nb2O5 ranges from 0.015 mass% or more to 0.04 mass% or less. In a case where Nb is contained independently, more preferably, Nb is contained that ranges from 0.015 mass% or more to less than 0.04 mass% on the basis of Nb2O5. Once the amount of Ta and/or Nb exceeds a predetermined amount, the magnetic core loss increases, and when the amount of Ta and/or Nb does not reach the predetermined amount, the effect of reducing the magnetic core loss is hard to be acquired.

    [0027] Moreover, in the present invention, at least one of Ti and Sn is contained as the sub component, which can further improve the magnetic core loss as a synergistic effect with the other sub component including Bi and also suppress the time-dependent change of the magnetic property under the high-temperature environment. Sn and Ti are tetravalent stable metal ions, dissolve in the crystal grain, and increase the volume resistivity ρ so as to reduce the magnetic core loss Pcv. Note that Ti and Sn are entirely present in the crystal grain, but a part thereof may be present in the grain boundary. In a case where Ti or Sn is contained independently, Ti or Sn is contained that ranges from 0.02 mass% or more to 0.2 mass% or less on the basis of TiO2 or SnO2 and even in a case where both of Ti and Sn are contained, a total amount of TiO2 and SnO2 ranges from 0.02 mass% or more to 0.2 mass% or less. Once the amount of Ti and/or Sn exceeds a preferred composition amount is exceeded, there is a case where an abnormal gain growth easily occurs to cause the power loss to deteriorate and to reduce the saturation magnetic flux density.

    [0028] Sulfur S, chlorine Cl, phosphorus P, boron B etc. may be contained as impurities in a raw material which constitutes the MnZn-based ferrite. In the present invention, these impurities are not specified especially, but it is known experientially that the reduction of the impurities achieves the reduction of the magnetic core loss and the improvement in the magnetic permeability. Especially concerning S, there is a case where a compound with Ca is generated, and is segregated in the grain boundary as a foreign substance to reduce the volume resistivity ρ and to increase the eddy current loss. For this reason, in order to further reduce the magnetic core loss, it is preferred that impurities are reduced and preferably S is set to be 0.03 mass% or less, Cl is set to be 0.01 mass% or less, P is set to 0.001 mass% or less and B is set to be 0.0001 mass% or less.

    (Method for Manufacturing MnZn-based ferrite)



    [0029] A raw material is weighted so that there is a predetermined composition amount as the MnZn-based ferrite, and then Fe2O3, MnO (Mn3O4 is used) and ZnO as the main component are temporally calcinated and cracked, and then SiO2, CaCO3, Co3O4 and Bi2O3, and Ta2O5 or Nb2O5, and TiO2 or SnO2 as the sub component are appropriately added and mixed, and a binder is added thereto and then the obtained composition is granulated and molded, and then is calcinated. In the present invention, the MnZn-based ferrite obtained after the calcination may be called a ferrite sintered body.

    [0030] The calcination step includes the high temperature maintaining step of maintaining in a predetermined temperature range, the temperature rising step which is the preceding step of the high temperature maintaining step, and the temperature falling step which is the following step of the high temperature maintaining step, and it is preferred that the temperature rising step is performed in the atmosphere during reaching from a room temperature to any temperature ranging from 750 °C to 950, N2 is substituted at any temperature ranging from 750 °C to 950 °C, an oxygen concentration is controlled in a range of 0.2 % to 0.7 % at the high temperature maintaining step where any temperature ranging from 1250 to 1400 °C is set, and also the equilibrium oxygen partial pressure is changed to the N2 atmosphere at the temperature falling step.

    [0031]  A rising rate at the temperature rising step may be appropriately selected according to a residual carbon state in a debinding and to a composition. Preferably the rising rate ranges from 50 to 200 °C/hr. Moreover it is known that Ca is segregated to the grain boundary as the oxygen concentration is higher and Ca dissolves to the spinel phase at a high temperature over 1100 °C in the low oxygen partial pressure to the N2 atmosphere. Then, in the present invention, it is preferred that the oxygen partial pressure is adjusted, which segregates Ca in the gain boundary while the dissolving of Ca into the crystal grain is appropriately controlled to reduce the magnetic core loss.

    [0032] In order to increase the resistance of the grain boundary, the control of a temperature falling rate according to a composition is employed as a calcination condition, and preferably a falling rate from a high-temperature maintaining temperature to 1000 °C ranges from 50 to 150 °C/hr, and a falling rate from 1000 °C to 900 °C ranges from 50 to 300 °C/hr, and a falling rate from 900 °C to 600 °C ranges from 150 to 500 °C/hr.

    [0033] More preferably, the control at the temperature falling step is specified by the following formula which is a function of an oxygen concentration PO2 (volume percent; %) and a temperature T (°C).



    [0034] Note that a and b are constants and it is preferred that "a" ranges from 3.1 to 12.8 and "b" ranges from 6000 to 20000. "a" is specified from a temperature and an oxygen concentration at the high temperature maintaining step. Moreover, once "b" is smaller than a predetermined range, an oxygen concentration is high and the oxidization progresses even when a temperature falls, and hematite may deposit from spinel. Furthermore, once "b" is large, the oxygen concentration falls and wustite deposits, and then the crystal grain and the gain boundary layer are not adequately oxidized to reduce the resistance. More preferably, "a" ranges from 6.4 to 11.5 and "b" ranges from 10000 to 18000, and the oxygen concentration at the high temperature maintaining step is controlled to be 0.7 % or less, the oxygen concentration at 1200 °C is controlled to be 0.5 % or less and the oxygen concentration at 1100 °C is controlled to be 0.1 % or less, which can further reduce the time-dependent change of the magnetic property under the high-temperature environment.

    [0035] Although an average crystal grain size of the MnZn-based ferrite is appropriately set according to an used frequency of an electronic component utilizing the MnZn-based ferrite, it is preferred that the average crystal grain size is set to 5 µm or less for a high frequency use of 500 kHz or more to reduce the eddy current loss, while the crystal grain is refined to subdivide a magnetic domain so as to reduce the loss due to the domain wall resonance, and it is preferred that the average crystal grain size is set to be more than 5 µm and 30 µm or less for a frequency use of less than 500 kHz to reduce a coercive force Hc so as to reduce the hysteresis loss.

    [Example 1]



    [0036] The following description explains the present invention more in detail with specific examples. A raw material was weighed so that there was a composition that amounts of Bi2O3 and TiO2 shown in Table 1 as the MnZn-based ferrite were different from each other. Fe2O3, MnO (Mn3O4 is used) and ZnO were used as a raw material of the main component, and wet-mixed and then dried and temporally calcinated at 900 °C for 3 hours. Subsequently, a temporally calcinated powder as well as SiO2, CaCO3, Co3O4, Ta2O5, Bi2O3 and TiO2 were added to a ball mill, and were ground and mixed until an average grinding grain size was 1.2 to 1.5 µm. Polyvinyl alcohol was added to the obtained mixture as a binder and was granulated with a spray drier, and then was molded to a predetermined shape to obtain a ring-shaped molded body, and the molded body was calcinated to obtain a magnetic core (a ferrite sintered body) with an outer diameter of ϕ25 mm × an inner diameter of ϕ15 mm × a thickness of 5 mm. In the following, an example where "*" is affixed to No. indicates a comparative example with the inclusion of Table 1.

    [0037] FIG. 1 indicates a temperature condition of the calcination step. The calcination step was performed in the atmosphere at the temperature rising step during reaching from a room temperature to 800 °C, and N2 was substituted at the temperature. At the high temperature maintaining step where 1300 °C was set, the oxygen concentration was set to be a value shown in the column of the O2 concentration of Table 1, and a maintaining time was set to 4 hours. At the temperature falling step during reaching from 1300 °C (high-temperature maintaining temperature) to 900 °C at the equilibrium oxygen partial pressure, the falling rate was set to 100 °C/hr, and the falling rate was set to 300 °C/hr after 900 °C or less.

    [Table 1]



    [0038] 
    Table 1
    No.Fe2O3 (mol %)ZnO (mol %)MnO (mol %)Co3O4 (mass %)SiO2 (mass %)CaCO3 (mass %)Ta2O5 (mass %)Nb2O5 (mass %)Bi2O3 (mass %)TiO2 (mass %)SnO2 (mass %)O2 concentration (%)
    *1 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0 0 0 1
    *2 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0 0 0 0.5
    *3 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0.02 0 0 3
    *4 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0.02 0 0 0.7
    *5 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0.02 0 0 0.5
    *6 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0.02 0 0 0.3
    *7 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0.02 0 0 0.2
    *8 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0 0.1 0 0.5
    9 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0.0075 0.1 0 0.5
    10 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0.01 0.1 0 0.5
    *11 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0.02 0.1 0 1
    12 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0.02 0.1 0 0.5
    13 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0.04 0.1 0 0.5
    *14 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0.05 0.1 0 0.5


    [0039] About the obtained magnetic core, the magnetic core loss Pcv, the saturation magnetic flux density Bs, and the average crystal grain size were evaluated. An evaluation method is as follows.

    (Magnetic core loss Pcv)



    [0040] For the magnetic core loss Pcv, the B-H analyzer (SY-8232) manufactured by Iwatsu Electric Co., Ltd. was used, a primary winding and a secondary winding are wound around the magnetic core for 5 turns respectively, and the magnetic core loss was measured at a frequency of 100 kHz and a maximum magnetic flux density of 200 mT at a room temperature (23 °C) to 150 °C.

    [0041] The magnetic core was held in a high temperature bath in the atmosphere of 200 °C for 96 hours to leave it in the high-temperature environment, and then the magnetic core was retrieved from the high temperature bath and after a temperature of the magnetic core falls to the room temperature, the magnetic core was evaluated at 130 °C on the same conditions, and a rate of change Ps of the magnetic core loss was calculated with the following formula from the magnetic core losses at 130 °C before and after leaving it in the high-temperature environment.



    [0042] Note that Pcv130A is the magnetic core loss at 130 °C before leaving the magnetic core in the high-temperature environment, and Pcv130B is the magnetic core loss at 130 °C after leaving the magnetic core in the high-temperature environment. Note that in the measurement of the magnetic core loss before leaving the magnetic core in the high-temperature environment, the magnetic core was placed in a constant temperature bath adjusted in the atmosphere of up to 150 °C for about 10 minutes to 15 minutes for stabilizing the temperature of the magnetic core, but the time-dependent change of the magnetic property did not substantially occur with the inclusion of magnetic cores of the following Examples.

    (Saturation magnetic flux density Bs)



    [0043] For a saturation magnetic flux density (Bs), a primary winding and a secondary winding were wound around the magnetic core for 40 turns respectively, a magnetic field of 1.2 kA/m was applied to the magnetic core and the saturation magnetic flux density (Bs) was measured at 130 °C using the direct-current magnetization measurement test equipment (manufactured by the METRON Inc., SK-110 type).

    (Average crystal grain size)



    [0044] For an average crystal grain size, a grain boundary was thermally etched in a mirror polished surface of a ferrite sintered body (1100 °C × 1 hr, processing in N2) and the surface was photographed with an optical microscope by 400 times, and then the average crystal grain size was calculated in a rectangular area of 140 µm × 105 µm on this picture with a quadrature.

    [0045] Table 2 indicates the evaluated results of the magnetic core loss Pcv, the saturation magnetic flux density Bs and the average crystal grain size. Note that "-" means not-evaluated in the average crystal grain size.

    [Table 2]



    [0046] 
    Table 2
    No.magnetic core loss Pcv(kW/m3)minimum temperature of magnetic core loss (°C)magnetic core loss at 130°C after left in high-temperature environment (kW/m3)rate of change Ps of magnetic core loss (%)saturation magnetic flux density Bs at 130°C (mT)average crystal grain size (µ m)
    23°C100°C130°C150°C
    *1 671 432 384 440 130 443 15.4 410 12.1
    *2 710 476 420 488 130 431 2.6 413 -
    *3 804 523 452 514 130 585 29.4 404 -
    *4 697 444 385 436 130 414 7.5 412 -
    *5 702 447 403 475 130 413 2.5 415 -
    *6 761 479 433 501 130 438 1.2 415 -
    *7 897 601 543 635 130 545 0.4 414 -
    *8 734 462 408 479 130 419 2.7 414 12.0
    9 715 405 357 420 130 365 2.2 414 -
    10 707 399 355 413 130 362 2.0 414 12.8
    *11 655 378 336 389 130 391 16.4 411 -
    12 683 384 348 400 130 356 2.2 415 13.0
    13 689 421 371 428 130 382 3.0 415 13.4
    *14 736 449 402 455 130 412 2.5 413 14.3


    [0047] Each of the magnetic core losses of the MnZn-based ferrites of Example shown in No. 9, No. 10, No. 12 and No. 13 was low, and the magnetic core loss at 130 °C before leaving the MnZn-based ferrite in the high-temperature environment was 380 kW/m3 or less, the magnetic core loss (Pcv130B) after leaving the magnetic core in the high-temperature environment was 400 kW/m3 or less, the magnetic core loss from 100 °C to 150 °C was 430 kW/m3 or less, and a minimum temperature of the magnetic core loss ranged from 110 °C to 150 °C. As shown in No. 11 and No. 12, the oxygen concentration is controlled so as to suppress the time-dependent change of the magnetic core loss, which further reduces a rate of increase of the magnetic core loss (Pcv130A) at 130 °C as compared with the comparative example. FIG. 2 shows the magnetic core losses before and after leaving the MnZn-based ferrites shown in No. 8, No. 10 and No. 12-14. In FIG. 2, a solid line represents the magnetic core loss before leaving them in the high-temperature environment, and a dashed line represents the magnetic core loss after leaving them in the high-temperature environment. The magnetic core loss turns out to be the minimum to the amount of Bi2O3.

    [Example 2]



    [0048] A raw material was weighed so that there was a composition that amounts of TiO2 and SnO2 shown in Table 3 as the MnZn-based ferrite were different from each other. The other step conditions are the same as Example 1, therefore, the explanation thereof is omitted.

    [Table 3]



    [0049] 
    Table 3
    No.Fe2O3 (mol %)ZnO (mol %)MnO (mol %)Co3O4 (mass %)SiO2 (mass %)CaCO3 (mass %)Ta2O5 (mass %)Nb2O5 (mass %)Bi2O3 (mass %)TiO2 (mass %)SnO2 (mass %)O2 concentration (%)
    *5 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0.02 0 0 0.5
    15 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0.02 0.02 0 0.5
    16 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0.02 0.05 0 0.5
    17 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0.02 0.1 0 0.5
    18 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0.02 0.2 0 0.5
    *19 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0.02 0.3 0 0.5
    20 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0.02 0 0.02 0.5
    21 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0.02 0 0.05 0.5
    22 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0.02 0 0.1 0.5
    23 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0.02 0 0.2 0.5
    *24 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0.02 0 0.3 0.5
    25 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0.02 0.1 0.05 0.5
    *26 53.65 4.5 41.85 0.3 0.006 0.12 0.03 0 0.02 0.15 0.15 0.5


    [0050] About the obtained magnetic core, the magnetic core loss Pcv, the saturation magnetic flux density Bs, and the average crystal grain size were evaluated. The evaluation method is the same as Example 1, therefore, the explanation thereof is omitted. The result is shown in Table 4.

    [Table 4]



    [0051] 
    Table 4
    No.magnetic core loss Pcv(kW/m3)minimum temperature of magnetic core loss (°C)magnetic core loss at 130°C after left in high-temperature environment (kW/m3)rate of change Ps of magnetic core loss (%)saturation magnetic flux density Bs at 130°C (mT)average crystal grain size (µm)
    23°C100°C130°C150°C
    *5 702 447 403 475 130 413 2.5 415 -
    15 695 435 391 447 130 399 2.0 415 -
    16 688 415 373 422 130 381 2.1 414 -
    17 683 384 348 398 130 356 2.2 415 13.0
    18 694 395 361 407 130 368 2.0 412 -
    *19 540 355 500 617 100 516 3.2 410 -
    20 687 433 388 440 130 397 2.3 415 -
    21 681 420 381 431 130 389 2.0 413 -
    22 685 404 362 415 130 369 1.9 413 -
    23 697 404 375 434 130 383 2.1 411 -
    *24 666 375 453 560 130 467 3.1 407 -
    25 688 411 367 426 130 375 2.2 411 -
    *26 623 389 434 538 100 445 2.5 407 -


    [0052] Each of the magnetic core losses of the MnZn-based ferrites of Example was low. FIG. 3 shows the magnetic core losses before and after leaving the MnZn-based ferrites shown in No. 5 and No. 15-24 in the high-temperature environment. In FIG. 3, a solid line of a circle represents the magnetic core loss before leaving in the high-temperature environment the MnZn-based ferrites shown in No. 5 and No. 15-19 whose TiO2 amounts are changed, and a dashed line represents the magnetic core loss after leaving them in the high-temperature environment. Also, a solid line of a triangle represents the magnetic core loss before leaving in the high-temperature environment the MnZn-based ferrites shown in No. 20-24 whose SnO2 amounts are changed, and a dashed line represents the magnetic core loss after leaving them in the high-temperature environment. The magnetic core loss turns out to be the minimum to the amounts of TiO2 and SnO2.

    [Example 3]



    [0053] Fe2O3, MnO (Mn3O4 is used), ZnO, SiO2, CaCO3, Co3O4, Ta2O5, Nb2O5, Bi2O3 and TiO2 were weighed so as to obtain a composition shown in Table 5 as the MnZn-based ferrite. The other step conditions are the same as Example 1, therefore, the explanation thereof is omitted.

    [Table 5]



    [0054] 
    Table 5
    No.Fe2O3 (mol %)ZnO (mol %)MnO (mol %)Co3O4 (mass %)SiO2 (mass %)CaCO3 (mass %)Ta2O5 (mass %)Nb2O5 (mass %)Bi2O3 (mass %)TiO2 (mass %)SnO2 (mass %)O2 concentration (%)
    27 53.75 4.50 41.75 0.16 0.003 0.08 0.03 0 0.02 0.1 0 0.5
    28 53.75 4.50 41.75 0.16 0.015 0.08 0.03 0 0.02 0.1 0 0.5
    *29 53.75 4.50 41.75 0.16 0.02 0.08 0.03 0 0.02 0.1 0 0.5
    *30 53.75 4.50 41.75 0.16 0.006 0.04 0.03 0 0.02 0.1 0 0.5
    31 53.75 4.50 41.75 0.16 0.006 0.06 0.03 0 0.02 0.1 0 0.5
    32 53.75 4.50 41.75 0.16 0.006 0.3 0.03 0 0.02 0.1 0 0.5
    *33 53.75 4.50 41.75 0.16 0.006 0.4 0.03 0 0.02 0.1 0 0.5
    *34 53.75 4.50 41.75 0 0.006 0.08 0.03 0 0.02 0.1 0 0.5
    35 53.75 4.50 41.75 0.16 0.006 0.08 0.03 0 0.02 0.1 0 0.5
    36 53.75 4.50 41.75 0.4 0.006 0.08 0.03 0 0.02 0.1 0 0.5
    *37 53.75 4.50 41.75 0.5 0.006 0.08 0.03 0 0.02 0.1 0 0.5
    *38 53.75 4.50 41.75 0.3 0.006 0.08 0 0 0.02 0.1 0 0.5
    39 53.75 4.50 41.75 0.3 0.006 0.08 0.015 0 0.02 0.1 0 0.5
    40 53.75 4.50 41.75 0.3 0.006 0.08 0.04 0 0.02 0.1 0 0.5
    *41 53.75 4.50 41.75 0.3 0.006 0.08 0.05 0 0.02 0.1 0 0.5
    42 53.75 4.50 41.75 0.3 0.006 0.08 0 0.015 0.02 0.1 0 0.5
    43 53.75 4.50 41.75 0.3 0.006 0.08 0 0.04 0.02 0.1 0 0.5
    *44 53.75 4.50 41.75 0.3 0.006 0.08 0 0.05 0.02 0.1 0 0.5
    45 53.75 4.50 41.75 0.3 0.006 0.08 0.015 0.015 0.02 0.1 0 0.5


    [0055] About the obtained magnetic core, the magnetic core loss Pcv and the saturation magnetic flux density Bs were evaluated. The evaluation method is the same as Example 1, therefore, the explanation thereof is omitted. The result is shown in Table 6. Each of the magnetic core losses of the MnZn-based ferrites of Example was low and a remarkable magnetic property was obtained.

    [Table 6]



    [0056] Examples 31, 36 and 43 are outside the scope of the invention.
    Table 6
              
    No.magnetic core loss Pcv(kW/m3)minimum temperature of magnetic core loss (°C)magnetic core loss at 130°C after left in high-temperature environment (kW/m3)rate of change Ps of magnetic core loss (%)saturation magnetic flux density Bs at 130°C (mT)average crystal grain size (µ m)
    23°C100°C130°C150°C
    27 820 409 357 428 130 369 3.4 410 -
    28 824 451 389 463 130 397 2.1 418 -
    *29 1743 1164 994 1169 130 1012 1.8 420 -
    *30 1111 632 553 655 130 572 3.4 406 -
    31 827 455 395 473 130 405 2.5 415 -
    32 815 452 386 475 130 396 2.6 413 -
    *33 1336 742 621 751 130 635 2.3 403 -
    *34 1075 512 406 544 130 407 0.2 416 -
    35 830 454 389 467 130 393 1.0 417 -
    36 651 422 399 441 130 417 4.5 415 -
    *37 613 457 450 488 130 490 8.9 413 -
    *38 725 493 432 501 130 445 3.0 413 -
    39 703 423 375 430 130 385 2.7 415 -
    40 694 397 351 403 130 359 2.3 418 -
    *41 1006 725 631 739 130 653 3.5 421 -
    42 700 395 354 406 130 363 2.5 414 -
    43 713 451 398 458 130 411 3.3 417 -
    *44 1422 954 821 1059 130 837 1.9 420 -
    45 687 405 363 417 130 372 2.5 418 -

    [Example 4]



    [0057] Fe2O3, MnO (Mn3O4 is used), ZnO, SiO2, CaCO3, Co3O4, Ta2O5, Bi2O3 and TiO2 were weighed so as to obtain a composition shown in Table 7 as the MnZn-based ferrite. The other step conditions are the same as Example 1, therefore, the explanation thereof is omitted.

    [Table 7]



    [0058] 
    Table 7
    No.Fe2O3 (mol %)ZnO (mol %)MnO (mol %)Co3O4 (mass %)SiO2 (mass %)CaCO3 (mass %)Ta2O5 (mass %)Nb2O5 (mass %)Bi2O3 (mass %)TiO2 (mass %)SnO2 (mass %)O2 concentration (%)
    46 53.25 5.50 41.25 0.16 0.006 0.08 0.03 0 0.02 0.1 0 0.5
    47 53.25 6.50 40.25 0.16 0.006 0.08 0.03 0 0.02 0.1 0 0.5
    48 53.25 7.50 39.25 0.16 0.006 0.08 0.03 0 0.02 0.1 0 0.5
    49 53.25 8.50 38.25 0.16 0.006 0.08 0.03 0 0.02 0.1 0 0.5
    50 53.75 3.50 42.75 0.16 0.006 0.08 0.03 0 0.02 0.1 0 0.5
    51 53.75 4.50 41.75 0.16 0.006 0.08 0.03 0 0.02 0.1 0 0.5
    52 54.00 2.50 43.50 0.16 0.006 0.08 0.03 0 0.02 0.1 0 0.5
    53 *54 54.00 3.50 42.50 0.16 0.006 0.08 0.03 0 0.02 0.1 0 0.5
    53.75 9.50 36.75 0.16 0.006 0.08 0.03 0 0.02 0.1 0 0.5
    *55 53.75 1.50 44.75 0.16 0.006 0.08 0.03 0 0.02 0.1 0 0.5
    *56 52.75 5.50 41.75 0.16 0.006 0.08 0.03 0 0.02 0.1 0 0.5
    *57 54.25 2.50 43.25 0.16 0.006 0.08 0.03 0 0.02 0.1 0 0.5


    [0059] About the obtained magnetic core, the magnetic core loss Pcv and the saturation magnetic flux density Bs were evaluated. The evaluation method is the same as Example 1, therefore, the explanation thereof is omitted. The result is shown in Table 8.

    [Table 8]



    [0060] 
    Table 8
    No.magnetic core loss Pcv(kW/m3)minimum temperature of magnetic core loss (°C)magnetic core loss at 130°C after left in high-temperature environment (kW/m3)rate of change Ps of magnetic core loss (%)saturation magnetic flux density Bs at 130°C (mT)average crystal grain size (µm)
    23°C100°C130°C150°C
    46 908 463 386 384 150 393 1.8 396 -
    47 811 423 377 420 130 384 1.8 392 -
    48 707 365 366 464 120 371 1.4 387 -
    49 569 300 386 488 110 390 1.2 385 -
    50 886 436 354 372 120 366 3.3 420 -
    51 896 370 335 446 120 342 2.1 417 -
    52 948 425 356 421 130 373 4.8 422 -
    53 870 348 338 478 120 351 3.9 420 -
    *54 338 629 737 759 40 743 0.9 378 -
    *55 1165 605 458 388 150< 486 6.1 407 -
    *56 1221 666 545 516 150 552 1.3 390 -
    *57 827 375 434 608 110 458 5.5 423 -


    [0061] Each of magnetic core losses of the MnZn-based ferrites of Example was low and a remarkable magnetic property was obtained. A temperature at which the magnetic core loss Pcv was the minimum varied according to composition amounts of Fe2O3, MnO and ZnO, and a minimum temperature of the magnetic core loss ranged from 110 °C to 150 °C in Example, but it was 40 °C in No. 54 of the comparative example and it was a temperature over 150 °C in No. 55 of the comparative example.


    Claims

    1. A MnZn-based ferrite containing Fe, Mn and Zn as a main component and containing Si, Ca, Co and Bi, and at least one of Ta and Nb, and at least one of Ti and Sn as a sub component, characterized in that
    given that a total amount is 100 mol% when the main component includes Fe2O3, ZnO and MnO respectively, Fe ranges from 53.25 mol% or more to 54.00 mol% or less on the basis of Fe2O3, Zn ranges from 2.50 mol% or more to 8.50 mol% or less on the basis of ZnO and Mn is the remainder on the basis of MnO,
    Si ranges from 0.003 mass% or more to 0.015 mass% or less on the basis of SiO2, Ca ranges from 0.06 mass% or more to 0.3 mass% or less on the basis of CaCO3, Co ranges from 0.16 mass% or more to 0.4 mass% or less on the basis of Co3O4, and Bi ranges from 0.0075 mass% or more to 0.04 mass% or less on the basis of Bi2O3, and in a case where Ta or Nb is contained independently, Ta ranges from 0.015 mass% or more to 0.04 mass% or less on the basis of Ta2O5 or Nb ranges from 0.015 mass% or more to 0.04 mass% or less on the basis of Nb2O5, and in a case where Ti or Sn is contained independently, Ti ranges from 0.02 mass% or more to 0.2 mass% or less on the basis of TiO2 or Sn ranges from 0.02 mass% or more to 0.2 mass% or less on the basis of SnO2, and in a case where both of Ta and Nb are contained, the converted total amount of Ta2O5 and Nb2O5 ranges from 0.015 mass% or more to 0.04 mass% or less, and in a case where both of Ti and Sn are contained, the converted total amount of TiO2 and SnO2 ranges from 0.02 mass% or more to 0.2 mass% or less, and
    at a frequency of 100 kHz in a maximum magnetic flux density of 200 mT, a magnetic core loss (Pcv130A) at 130 °C is 400 kW/m3 or less, and a rate of change Ps of the magnetic core loss is 5 % or less that is expressed in the following formula using the magnetic core loss (Pcv130B) at 130 °C after maintaining the MnZn-based ferrite at 200 °C for 96 hours.


     
    2. The MnZn-based ferrite according to claim 1, wherein
    the magnetic core loss between 100°C and 150 °C is 500 kW/m3 or less and the minimum temperature of the magnetic core loss ranges from 110 °C to 150 °C.
     
    3. The MnZn-based ferrite according to claim 2, wherein
    the magnetic core loss (Pcv130B) at 130 °C after maintaining the MnZn-based ferrite at 200 °C for 96 hours is 400 kW/m3 or less.
     
    4. A method for manufacturing a MnZn-based ferrite, comprising:

    a calcination step of molding an oxide powder of the main component and the sub component specified in claim 1 to obtain a molded body and calcinating the molded body,
    and

    the calcination step includes a temperature rising step, a high temperature maintaining step and a temperature falling step,

    a temperature at the high temperature maintaining step ranges from 1250 °C to 1400 °C, and an oxygen concentration in an atmosphere at the high temperature maintaining step is 0.7 % or less in a volume percent, and

    an oxygen concentration at 1200 °C is 0.5 % or less and an oxygen concentration at 1100 °C is 0.1 % or less at the temperature falling step.


     


    Ansprüche

    1. Ferrit auf MnZn-Basis, der Fe, Mn und Zn als Hauptkomponente und Si, Ca, Co und Bi sowie mindestens eines von Ta und Nb und mindestens eines von Ti und Sn als Unterkomponente enthält, dadurch gekennzeichnet, dass
    wenn gegeben ist, dass die Gesamtmenge 100 Mol-% beträgt und wenn die Hauptkomponente Fe2O3, ZnO bzw. MnO aufweisen, dann liegt Fe liegt im Bereich von 53,25 Mol-% oder mehr bis 54,00 Mol-% oder weniger auf der Basis von Fe2O3, Zn im Bereich von 2,50 Mol-% oder mehr bis 8,50 Mol-% oder weniger auf der Basis von ZnO und Mn ist der Rest auf der Basis von MnO,
    Si im Bereich von 0,003 Massen-% oder mehr bis 0,015 Massen-% oder weniger auf der Basis von SiO2 liegt, Ca im Bereich von 0,06 Massen-% oder mehr reicht bis 0,3 Massen- % oder weniger auf der Basis von CaCO3 liegt, Co im Bereich von 0,16 Massen-% oder mehr bis 0,4 oder weniger auf der Basis Co3O4 liegt, Bi im Bereich von 0,0075 Massen- % oder mehr bis 0,04 Massen-% oder weniger auf der Basis von Bi2O3 liegt, und für einen Fall, wo Ta oder Nb unabhängig voneinander vorgesehen sind, liegt Ta im Bereich von 0,015 Massen-% oder mehr bis 0,04 Massen-% oder weniger auf der Basis von Ta2O5 oder Nb im Bereich von 0,015 Massen-% oder mehr bis 0,04 Massen-% oder weniger auf der Basis von Nb2O5, und für einen Fall, wo Ti oder Sn unabhängig voneinander vorgesehen sind, liegt Ti im Bereich von 0,02 Massen-% oder mehr bis 0,2 Massen-% oder weniger auf der Basis von TiO2 oder Sn im Bereich von 0,02 Massen-% oder mehr bis 0,2 Massen-% oder weniger auf der Basis von SnO2, und für einen Fall, wo sowohl Ta als auch Nb vorgesehen sind, liegt die umgerechnete Gesamtmenge Ta2O5 und Nb2O5 im Bereich von 0,015 Massen- % oder mehr bis 0,04 Massen-% oder weniger, und für einen Fall, wo sowohl Ti als auch Sn vorgesehen sind, liegt die umgerechnete Gesamtmenge TiO2 und SnO2 im Bereich von 0,02 Massen- % oder mehr bis 0,2 Massen-% oder weniger
    bei einer Frequenz von 100 kHz in einer maximalen magnetischen Flussdichte von 200 mT ein Magnetkernverlust (Pcv130A) bei 130 °C 400 kW/m3 oder weniger beträgt, und eine Änderungsrate Ps des Magnetkernverlusts 5% oder weniger beträgt, die ausgedrückt ist in der folgenden Formel unter Verwendung des Magnetkernverlusts Pcv130B) bei 130 °C nach einem Halten des Ferrits auf MnZn-Basis für 96 Stunden bei 200°Cm.


     
    2. Ferrit auf MnZn-Basis nach Anspruch 1, wobei der Magnetkernverlust zwischen 100 °C und 150 °C 500 kW/m3 oder weniger beträgt und die minimale Temperatur des Magnetkernverlusts im Bereich von 110 °C bis 150 °C liegt.
     
    3. Ferrit auf MnZn-Basis nach Anspruch 2, wobei der Magnetkernverlust (Pcv130B) bei 130 ° C nach 96-stündigem Halten des Ferrits auf MnZn-Basis bei 200 °C 400 kW/m3 oder weniger beträgt.
     
    4. Verfahren zur Herstellung eines Ferrits auf MnZn-Basis, aufweisend:

    einen Kalzinierungsschritt des Formens eines Oxidpulvers der in Anspruch 1 angegebenen Hauptkomponente und Unterkomponente, um einen Formkörper zu erhalten und des Kalzinierens des Formkörpers,

    wobei der Kalzinierungsschritt einen Temperatur-Erhöhungsschritt, einen Hochtemperatur-Halteschritt und Temperatur-Ab senkschritt aufweist,

    wobei eine Temperatur im Hochtemperatur-Halteschritt im Bereich von 1250 °C bis 1400 °C liegt und eine Sauerstoffkonzentration einer Atmosphäre im Hochtemperatur-Halteschritt 0,7% oder weniger in Volumenprozent beträgt, und

    wobei eine Sauerstoffkonzentration bei 1200 °C im Temperatur-Absenkschritt 0,5% oder weniger und eine Sauerstoffkonzentration bei 1100 °C im Temperatur-Absenkschritt 0,1% oder weniger beträgt.


     


    Revendications

    1. Ferrite à base de MnZn contenant Fe, Mn et Zn comme composant principal, et contenant Si, Ca, Co et Bi, et au moins l'un de Ta et Nb, et au moins l'un de Ti et Sn comme sous-composant,
    caractérisé en ce que
    étant donné qu'une quantité totale est de 100 % en moles lorsque le composant principal comprend Fe2O3, ZnO et MnO respectivement, Fe est compris entre 53,25 % en moles ou plus et 54,00 % en moles ou moins sur la base de Fe2O3, Zn est compris entre 2,50 % en moles ou plus et 8,50 % en moles ou moins sur la base de ZnO, et Mn est le reste sur la base de MnO,
    Si est compris entre 0,003 % en masse ou plus et 0,015 % en masse ou moins sur la base de SiO2, Ca est compris entre 0,06 % en masse ou plus et 0,3 % en masse ou moins sur la base de CaCO3, Co est compris entre 0,16 % en masse ou plus et 0,4 % en masse ou moins sur la base de Co3O4, et Bi est compris entre 0,0075 % en masse ou plus et 0,04 % en masse ou moins sur la base de Bi2O3, et dans le cas où Ta ou Nb est contenu indépendamment, Ta est compris entre 0,015 % en masse ou plus et 0,04 % en masse ou moins sur la base de Ta2O5 ou Nb est compris entre 0,015 % en masse ou plus et 0,04 % en masse ou moins sur la base de Nb2O5, et dans le cas où Ti ou Sn est contenu indépendamment, Ti est compris entre 0,02 % en masse ou plus et 0,2 % en masse ou moins sur la base de TiO2 ou Sn est compris entre 0,02 % en masse ou plus et 0,2% en masse ou moins sur la base de SnO2, et dans le cas où Ta et Nb sont contenus tous les deux, la quantité totale convertie de Ta2O5 et de Nb2O5 est comprise entre 0,015 % en masse ou plus et 0,04 % en masse ou moins, et dans le cas où Ti et Sn sont contenus tous les deux, la quantité totale convertie de TiO2 et de SnO2 est comprise entre 0,02 % en masse ou plus et 0,2 % en masse ou moins, et
    à une fréquence de 100 kHz dans une densité de flux magnétique maximum de 200 mT, les pertes magnétiques de noyau (Pcv130A) à 130 °C sont de 400 kW/m3 ou moins, et le taux de variation Ps des pertes magnétiques de noyau est de 5 % ou moins comme exprimé dans la formule suivante utilisant les pertes magnétiques de noyau (Pcv130B) à 130 °C après avoir maintenu le ferrite à base de MnZn à 200 °C pendant 96 heures :


     
    2. Ferrite à base de MnZn selon la revendication 1, dans laquelle les pertes magnétiques de noyau entre 100 °C et 150 °C sont de 500 kW/m3 ou moins et la température minimum des pertes magnétiques de noyau est comprise entre 110 °C et 150 °C.
     
    3. Ferrite à base de MnZn selon la revendication 2, dans laquelle
    les pertes magnétiques de noyau (Pcv130B) à 130 °C après avoir maintenu la ferrite à base de MnZn à 200 °C pendant 96 heures sont de 400 kW/m3 ou moins.
     
    4. Procédé de fabrication d'une ferrite à base de MnZn, comprenant :

    une étape de calcination consistant à mouler de la poudre d'oxyde du composant principal et du sous-composant spécifiés en revendication 1 pour obtenir un corps moulé et à calciner le corps moulé, et

    l'étape de calcination comprend une étape de montée en température, une étape de maintien à haute température et une étape de descente en température,

    la température au niveau de l'étape de maintien à haute température est comprise entre 1250 °C et 1400 °C, et la concentration en oxygène dans une atmosphère au niveau de l'étape de maintien à haute température est de 0,7 % ou moins en pourcentage en volume, et

    la concentration en oxygène à 1200 °C est de 0,5 % ou moins et la concentration en oxygène à 1100 °C est de 0,1 % ou moins au niveau de l'étape de descente en température.


     




    Drawing











    Cited references

    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description