JP5693725B2 - Ferrite sintered body and ferrite core provided with the same - Google Patents

Description

  The present invention relates to a ferrite sintered body and a ferrite core formed by winding a metal wire around the ferrite sintered body.

  In recent years, the LAN interface part of various IT-related equipment has been equipped with a pulse transformer for the purpose of insulation and noise removal. The core part is an inductor, transformer, ballast, electromagnet, noise filter. Similar to the above, a ferrite sintered body is used. Such a core is required to have a high magnetic permeability. Therefore, among ferrite sintered bodies, Mn—Zn ferrite sintered bodies with high magnetic permeability have been widely used. However, Mn—Zn ferrite has a problem of low specific resistance (electric resistance).

On the other hand, Ni—Zn ferrite is known as a ferrite having a specific resistance approximately two orders of magnitude higher than that of Mn—Zn ferrite. For example, Patent Document 1 discloses that Fe is converted to Fe ₂ O ₃ at 45.0 to 50.0 mol%, Ni is converted to NiO at 5.0 to 10.0 mol%, Cu is converted to CuO at 5.0 to 15.0 mol%, When Zn is converted to ZnO, 25.0 to 35.0 mol%, at least one metal selected from Mo, W, V, Cr, Mg, Ca, Sr and Ba and Mn are added to MoO ₃ , WO and V ₂ O ₅ , respectively. , Cr ₂ O ₃ , MgO, CaO, SrO, BaO, and Mn ₃ O ₄ in total 0.1 to 3.0 mol%, and oxide magnetic material containing Li to Li ₂ O 0.01 to 3.0 mol% Proposed.

JP-A-8-208233

  However, although the oxide magnetic material of Patent Document 1 has a high specific resistance, the magnetic permeability shown in the examples is at most 2000, and there is a problem that the magnetic permeability is low.

  On the other hand, since the ferrite sintered body needs to have no characteristic change when the use environment temperature changes due to heat generated from mounted parts such as various IT-related devices, the specific resistance, In addition to the high permeability and Curie temperature, the temperature change rate of the permeability at room temperature (25 ° C.) to 100 ° C. is required to be small.

  The present invention relates to a ferrite sintered body having a high specific resistance, magnetic permeability and Curie temperature and a small temperature change rate of magnetic permeability from room temperature (25 ° C.) to 100 ° C., and a pulse formed by winding a metal wire around the ferrite sintered body. The object is to provide a transformer core.

The ferrite sintered body of the present invention comprises Fe of 49 mol% or more and 50 mol% or less in terms of Fe ₂ O ₃ and Zn of 32 mol% or more and 34.5 mol% or less in terms of ZnO, out of 100 mol% of the main component composition, Ni That the content of ZnO is 6.5 mol% to 12.5 mol% in terms of NiO and Cu is 5 mol% to 9 mol% in terms of CuO, and that ZnO is present at the grain boundaries of the ferrite crystal composed of the main component. It is a feature.

  The ferrite core of the present invention is characterized in that a metal wire is wound around the ferrite sintered body having the above-described configuration.

  According to the ferrite sintered body of the present invention, a ferrite sintered body having high specific resistance, magnetic permeability, and Curie temperature and a small temperature change rate of magnetic permeability from room temperature (25 ° C.) to 100 ° C. can be obtained.

  According to the ferrite core of the present invention, a ferrite core having stable and good performance can be obtained in a wide temperature range from a low temperature range to a high temperature range.

An example of the ferrite sintered compact of this embodiment is shown, (a) is a perspective view of a toroidal core, (b) is a perspective view of a bobbin core. It is a schematic diagram which shows an example of the crystal structure of the ferrite sintered compact of this embodiment.

  Hereinafter, the ferrite sintered body of the present invention and a ferrite core including the same will be described.

  The ferrite sintered body of the present embodiment has an inductor, a transformer, a ballast, an electromagnet, a noise filter, and recently, a personal computer, a digital TV, an AV, by winding a metal wire around the ferrite sintered body as a core. It is used for a pulse transformer for the purpose of insulation, noise removal, etc., which is mounted on a LAN interface unit equipped in equipment.

  Here, there are various ferrite sintered body shapes. For example, the ring-shaped toroidal core 10 shown in the perspective view of FIG. 1A or the bobbin-shaped bobbin core shown in the perspective view of FIG. There are 20 etc.

The ferrite sintered body of the present embodiment constituting such a ferrite core has a high specific resistance, magnetic permeability (μ), and Curie temperature (Tc), in addition to various IT-related devices, for example. Since it is necessary that the characteristic change does not occur when the use environment temperature is changed by the heat generated from the mounted component, the temperature change rate of the magnetic permeability at 25 ° C. to 100 ° C. is required to be small. Here, the ferrite sintered body of the present embodiment satisfy this requirement, among the main component composition 100 mol%, the Fe Fe ₂ O ₃ 50 mol% 49 mol% or more in terms of less, and Zn in terms of ZnO Grain boundaries of ferrite crystals comprising 32 mol% to 34.5 mol%, Ni containing 6.5 mol% to 12.5 mol% in terms of NiO and Cu containing 5 mol% to 9 mol% in terms of CuO It is characterized in that ZnO is present in (hereinafter also simply referred to as a crystal grain boundary).

Here, the reason why the main component is in the composition range described above is that a ferrite sintered body having a high specific resistance, magnetic permeability, and Curie temperature can be obtained. In contrast, the Fe is less than 49 mol% calculated as Fe ₂ O _3, there is a tendency for permeability is low, tends to decrease the specific resistance exceeds 50 mol%. Further, when Zn is less than 32 mol% in terms of ZnO, the magnetic permeability tends to be low, and when it exceeds 34.5 mol%, the Curie temperature tends to decrease. Further, when Ni is less than 6.5 mol% in terms of NiO, the Curie temperature tends to decrease, and when it exceeds 12.5 mol%, the magnetic permeability tends to decrease. Further, if Cu is less than 5 mol% in terms of CuO, the magnetic permeability tends to be low, and if it exceeds 9 mol%, the Curie temperature tends to be low.

  In addition, the mass in terms of oxides of Fe, Zn, Ni, and Cu constituting the main component should occupy 95% by mass or more when all the components constituting the ferrite sintered body are 100% by mass.

And about the confirmation method of the main component composition of the ferrite sintered compact of this embodiment, content of Fe, Zn, Ni, and Cu using an ICP (Inductively Coupled Plasma) emission spectroscopic analyzer or a fluorescent X-ray analyzer. May be converted into Fe ₂ O ₃ , ZnO, NiO, and CuO, the molar value may be calculated from each molecular weight, and the occupation ratio of each molar value in the total of the calculated molar values may be calculated.

  Next, an example of the crystal structure of the ferrite sintered body of the present embodiment will be described with reference to the schematic diagram shown in FIG. A hexagonal shape shown in FIG. 2 is a ferrite crystal 2 composed of the above-described main components, and a boundary between the ferrite crystals 2 is a crystal grain boundary 3. In the ferrite sintered body of the present embodiment, the presence of ZnO indicated by reference numeral 1 at the grain boundary 3 suppresses the interaction of magnetic force between the ferrite crystals 2, so that the temperature change of the magnetic permeability The rate can be reduced. In particular, it is preferable that ZnO exists at the triple point in the crystal grain boundary 3.

  Here, a method for confirming the presence of ZnO at the crystal grain boundaries 3 will be described. First, the ferrite sintered body is cut and the cross section is mirror finished. Then, a mirror-processed cross section is observed with a transmission electron microscope (TEM) to confirm the presence or absence of the compound at the crystal grain boundary, and the crystal structure of the compound is confirmed using the attached energy dispersive X-ray diffractometer. Thus, it can be confirmed whether or not ZnO exists in the crystal grain boundaries 3.

  Next, a method for measuring the specific resistance, the magnetic permeability, the Curie temperature, and the temperature change rate of the magnetic permeability will be described. First, for specific resistance, for example, a plate-shaped sample having a diameter of 10 to 20 mm and a thickness of 0.5 to 2 mm is prepared, and an applied voltage of 1000 V and a temperature of 26 are measured using a super insulation resistance meter (TOA DSM-8103). What is necessary is just to measure by 3 terminal method (JIS K6271; double ring electrode method) in the measurement environment of 36 degreeC and humidity 36%.

  Next, regarding the magnetic permeability, the sample may be measured under the condition of a frequency of 100 kHz using an LCR meter. As a sample, for example, a ring-shaped toroidal core 10 made of a ferrite sintered body shown in FIG. 1A having an outer diameter of 13 mm, an inner diameter of 7 mm, and a thickness of 3 mm is used. A wire with a wire diameter of 0.2 mm wound around the entire circumference is used 10 times. Further, the Curie temperature can be obtained by a bridge circuit method using an LCR meter using a sample similar to that at the time of measuring the magnetic permeability.

Furthermore, the temperature change rate of the magnetic permeability may be measured by using a similar sample and connecting it to a measurement jig in a thermostatic bath. The measuring jig is connected to the LCR meter, and measured at a frequency of 100 kHz. The magnetic permeability at 25 ° C. is μ ₂₅ , and the highest magnetic permeability when the temperature is raised from 25 ° C. to 100 ° C. is μ _100. , (Μ ₁₀₀ −μ ₂₅ ) / μ ₂₅ × 100.

The ferrite sintered body of the present embodiment has a high specific resistance, magnetic permeability, and Curie temperature, and has a small temperature change rate of magnetic permeability. Specifically, the specific resistance is 10 ⁷ Ω · m or more, The permeability is 2700 or more, the Curie temperature is 75 ° C. or more, and the temperature change rate of the permeability at 25 ° C. to 100 ° C. can be 30% or less.

In the ferrite sintered body of the present embodiment, it is preferable that the area occupation ratio of ZnO is 0.1% or more and 3.0% or less. Here, the area occupancy of ZnO is one field when measuring a mirror-finished cross section of a ferrite sintered body using a wavelength dispersive X-ray microanalyzer apparatus (JXA-8100 manufactured by JEOL), for example, 70 μm. It is an area ratio occupied by ZnO in an area of 4900 μm ^{2 of} × 70 μm.

The method for calculating the occupation area ratio is as follows. First, Zn is measured using a wavelength dispersion type X-ray microanalyzer apparatus (JXA-8100 made by JEOL). And the mapping which recorded the intensity | strength of the characteristic X-ray detected in each analysis point within 1 visual field on the XY coordinate is used. When ZnO is present at the grain boundary, the mapping shows a high value of the characteristic X-ray intensity of Zn. Therefore, a portion showing a value 20% or more higher than the average value of the characteristic X-ray intensity of Zn in this mapping is regarded as a portion where ZnO is present at the crystal grain boundary, and the area of this portion is the viewing area. By dividing by 4900 μm ² and expressing as a percentage, the area occupation ratio of ZnO can be obtained.

  When the area occupancy of ZnO calculated in this way is 0.1% or more and 3.0% or less, the magnetic permeability can be improved and the temperature change of the magnetic permeability can be suppressed by suppressing the interaction of magnetic force between ferrite crystals. The rate can be further reduced.

Moreover, it is preferable that the ferrite sintered compact of this embodiment contains 0.05 mass% or more and 0.3 mass% or less in terms of MnO ₂ with respect to 100 mass% of the main component having the above composition range. Since Mn can have a plurality of valences, MnO ₂ and Mn ₃ O ₄ existing as oxides are changed in valence to MnO by heating, and the excess oxygen component accompanying the change is the crystal of the main component. By filling oxygen defects, the magnetic permeability can be improved.

Moreover, it is preferable that the ferrite sintered compact of this embodiment contains 0.01 mass% or more and 0.3 mass% or less of Mo in conversion of MoO ₃ with respect to 100 mass% of the main component having the composition range described above. Mo can promote the crystal grain growth of the main component, and the magnetic permeability can be improved by setting the content within the above-described range. In order to further improve the magnetic permeability, it is preferable to contain Mo in an amount of 0.05% by mass to 0.2% by mass in terms of MoO ₃ .

In addition to the main components, Mo and Mn, Si and Ca oxides may be included. The specific resistance can also be improved by including this Si or Ca oxide. In addition, when the oxide of Si or Ca is included, it is preferable that it is 0.4 mass% or less in total in which Si is converted into SiO ₂ and Ca is converted into CaO with respect to 100 mass% of the main component.

As for the contents of Mo and Mn, the contents of Mo and Mn are obtained using an ICP emission spectroscopic analyzer or a fluorescent X-ray analyzer, and converted to MoO ₃ and MnO ₂ , respectively. The value for can be calculated. The same applies to Si and Ca.

  And since the ferrite core formed by winding a metal wire around the ferrite sintered body of the present embodiment uses a ferrite sintered body having a high specific resistance, magnetic permeability, and Curie temperature, and a low rate of change in the temperature of the magnetic permeability. In a wide temperature range from low temperature range to high temperature range, it becomes a ferrite core that has stable and good performance, and can be suitably used for inductors, transformers, ballasts, electromagnets, noise filters, personal computers, digital TVs, It can also be suitably used for a pulse transformer mounted on a LAN interface unit equipped in an AV device.

  Next, details of an example of the method for producing a ferrite sintered body according to the present embodiment will be described below.

In the method for producing a ferrite material according to the present embodiment, first, as a starting material, an oxide of Fe, Zn, Ni, Cu or a metal salt such as carbonate or nitrate that generates an oxide by firing is prepared. The average particle size at this time is, for example, 0.5 μm when Fe is iron oxide (Fe ₂ O ₃ ), Zn is zinc oxide (ZnO), Ni is nickel oxide (NiO), and Cu is copper oxide (CuO). It is 5 μm or less. In addition, with respect to Zn, zinc oxide added as a starting material and zinc oxide added as a ZnO source to be present at grain boundaries after calcination, the ferrite sintered body has 32 mol% or more and 34.5 mol% in terms of ZnO. Since it is contained below, the starting material is weighed by subtracting the amount added after calcination. For Fe, Ni, and Cu, Fe is 49 mol% or more and 50 mol% or less in terms of Fe ₂ O ₃ , Ni is 6.5 mol% or more and 12.5 mol% or less in terms of NiO, and Cu is 5 mol% or more in terms of CuO. Weigh so that the composition range is 9 mol% or less.

  Then, each powder constituting the main component weighed as a starting material is pulverized and mixed with a ball mill or a vibration mill, and then calcined at a temperature of 700 ° C. or higher and 750 ° C. or lower for 2 hours or longer to obtain a calcined body synthesized into ferrite. Get.

  Next, a predetermined amount of zinc oxide serving as a ZnO source to be present at the crystal grain boundary is weighed and put into a ball mill, a vibration mill or the like together with the calcined body and a solvent and pulverized and mixed. In addition, it is preferable that the addition amount of a zinc oxide is 0.001 mol% or more and 0.02 mol% or less in conversion of ZnO. Moreover, it is preferable that the average particle diameter of the zinc oxide added here is 2 micrometers or more and 4 micrometers or less. The reason why the average particle diameter of zinc oxide is 2 μm or more and 4 μm or less is that the zinc oxide to be added does not easily dissolve in the ferrite crystal but is dispersed in the crystal grain boundaries of the ferrite sintered body.

  And after grind | pulverizing until an average particle diameter becomes 1 micrometer or less, a predetermined amount of binder is added and it is set as a slurry, It granulates using a spray granulator (spray dryer), and obtains a spherical granule. Next, this spherical granule is press-molded to obtain a molded body having a predetermined shape. Thereafter, the molded body is degreased in a range of 400 to 800 ° C. in a degreasing furnace to obtain a degreased body, and then held in a firing furnace in the range of 1000 to 1200 ° C. for 2 to 5 hours and fired. Thus, the ferrite sintered body of the present embodiment is obtained. In this firing step, firing is preferably performed with the degreased body completely covered with a refractory material in order to prevent evaporation of the Fe and Zn components.

In order to contain Mo and Mn, for example, molybdenum oxide (MoO ₃ ) or manganese oxide (MnO ₂ ) may be prepared and added during pulverization after calcination. For Si and Ca, silicon oxide (SiO ₂ ) and calcium oxide (CaO) may be prepared and added during pulverization after calcination.

As for Mn, since it is preferable that Mn is contained in an amount of 0.05% by mass or more and 0.3% by mass or less in terms of MnO ₂ with respect to 100% by mass of the main component of the ferrite sintered body, is taken as 100 mass% of the mass of the main components plus the zinc oxide to be added later, contrary, is preferably 0.05 mass% or more and 0.3 mass% or less with MnO ₂ basis.

In addition, with respect to Mo, since it is preferable to include Mo in an amount of 0.01% by mass or more and 0.3% by mass or less in terms of MoO ₃ with respect to 100% by mass of the main component of the ferrite sintered body, When the mass of the main component added with zinc oxide to be added later is 100% by mass, it is preferably in the range of 0.01% by mass to 0.3% by mass in terms of MoO ₃ . Furthermore, with respect to Ca and Si, it is preferable that the total mass converted to CaO and SiO ₂ is set to 0.4% by mass or less with respect to 100% by mass. Hereinafter, examples of the present invention are specifically described. However, the present invention is not limited to this embodiment.

  Examples of the ferrite sintered body of the present embodiment are shown below.

  Sample No. with different main component compositions. Samples No. 1 and No. 18 to which zinc oxide is not added after calcining 1 to 17 and a sintered body are produced. Presence / absence of ZnO at grain boundaries, magnetic permeability, Curie temperature, and room temperature (25 ° C.) to 100 ° C. A test was conducted to measure the rate of change in permeability with temperature.

  First, as starting materials, powders of iron oxide, zinc oxide, nickel oxide and copper oxide having an average particle diameter of 1 μm were prepared and weighed so as to have the ratio shown in Table 1. In addition, about zinc oxide, the quantity except the addition amount after calcination was used for the starting material. Each powder constituting the main component weighed as a starting material was pulverized and mixed with a vibration mill, and calcined at 750 ° C. for 2 hours to obtain a calcined body. Next, the amount of zinc oxide powder shown in Table 1 is weighed, put into a ball mill with a calcined body and a solvent and pulverized, and then a binder is added to form a slurry, which is prepared using a spray granulator (spray dryer). Granulated to give spherical granules. The zinc oxide powder added after calcination had an average particle size of 3 μm.

  Next, this spherical granule was press-molded to obtain a molded body to be a toroidal core 10 having the shape shown in FIG. Thereafter, the compact was subjected to a degreasing treatment at 600 ° C. in a degreasing furnace to obtain a degreased body. After that, the degreased body is arranged on a fired shelf board made of a refractory material, and the degreased body is completely covered with a block-like refractory material, and then in an atmospheric firing furnace at 1000 to 1200 ° C. for 2 hours. Hold and fired. Thereafter, grinding was performed, and sample No. 1 consisting of a toroidal core 10 having an outer diameter of 13 mm, an inner diameter of 7 mm, and a thickness of 3 mm as shown in FIG. 1 to 17 ferrite sintered bodies were obtained. Sample No. 18 was obtained by the same production method as described above except that zinc oxide powder was not added after calcination.

Then, a coated copper wire having a wire diameter of 0.2 mm was wound 10 times around the entire circumference of the winding portion 10a of each sample, and the magnetic permeability at a frequency of 100 kHz was measured using an LCR meter. In addition, the Curie temperature was determined by the bridge circuit method. Furthermore, using the sample similar to the measurement of magnetic permeability, it connected to the measurement jig | tool in a thermostat, and measured the temperature change rate of the magnetic permeability. This measuring jig is connected to an LCR meter, and measured at a frequency of 100 kHz. The magnetic permeability at 25 ° C. is μ ₂₅ , and the highest magnetic permeability when the temperature is raised from 25 ° C. to 100 ° C. is μ ₁₀ Then, the temperature change rate of the magnetic permeability from 25 ° C. to 100 ° C. was obtained by the formula (μ ₁₀₀ −μ ₂₅ ) / μ ₂₅ × 100.

  In addition, for the presence or absence of ZnO at the grain boundaries, the sample was cut and the cross section was mirror-finished, and the mirror-processed cross section was observed with a transmission electron microscope to confirm the presence of the compound at the crystal grain boundary. The crystal structure of the compound was confirmed using a dispersive X-ray diffractometer.

  For specific resistance, the same spherical granules as in the preparation of each sample were press-molded to obtain a disk-shaped molded body having a thickness of 2 mm or less, and then a sintered body was obtained by the same firing method. It was. Thereafter, grinding was performed to obtain a measurement sample having a shape of φ of 16 mm and a thickness of 1 mm. And it measured by the 3 terminal method (JIS K6271; double ring electrode method) in the environment of applied voltage 1000V, temperature 26 degreeC, and humidity 36% using the super-insulation resistance meter (DSM-8103 by TOA). The results are shown in Table 1.

Incidentally, for each sample, using a fluorescent X-ray analyzer, the Fe in terms of _Fe 2 _{O 3} seeking each metal element amount, the Zn in terms of ZnO, in terms of Ni to NiO, with Cu CuO Converted, the molar value was calculated from each molecular weight, and the occupancy of each molar value in the total molar value was calculated. As a result, the main component composition was as shown in Table 1. In addition, about ZnO, it confirmed that it was the mol% which added ZnO which is a main component in Table 1, and ZnO added after calcination. The results are shown in Table 1.

From the results of Table 1, among 100 mol% of the main component composition, Fe is 49 mol% or more and 50 mol% or less in terms of Fe ₂ O ₃ , Zn is 32 mol% or more and 34.5 mol% or less in terms of ZnO, Ni is NiO equivalent In the case of sample No. 1 which does not satisfy at least one from the composition range of 6.5 mol% to 12.5 mol% and Cu is 5 mol% to 9 mol% in terms of CuO. For 1,4,5,8,9,12,13,16, the permeability is less than 2700, the Curie temperature is less than 75 ° C, or the temperature change rate of the permeability between 25 ° C and 100 ° C is over 30% It was. Further, Sample No. which does not contain ZnO in the crystal grain boundary. 18 had a temperature change rate of magnetic permeability of 25 ° C. to 100 ° C. exceeding 30%.

In contrast, among the main component composition 100 mol%, Fe and _Fe 2 _{O 3} 50 mol% 49 mol% or more in terms of less, and Zn in terms of ZnO 32 mol% or more 34.5 mol% or less, the Ni in terms of NiO 6.5 Sample No. 1 containing mol% or more and 12.5 mol% or less and Cu containing 5 mol% or more and 9 mol% or less in terms of CuO, and ZnO is present at the grain boundaries of the ferrite crystal composed of the main component. 2,3,6,7,10,11,14,15,17 have a permeability of 2700 or more, a Curie temperature of 75 ° C or more, and a temperature change rate of permeability of 25 ° C to 100 ° C of 30% The following were confirmed to have good characteristics.

  And sample no. When a metal wire is wound around 2, 3, 6, 7, 10, 11, 14, 15, 17 and used as a core for a pulse transformer, the resistivity, magnetic permeability, and Curie temperature are high, and the rate of change in the temperature of the magnetic permeability Since a ferrite sintered body having a small diameter is used, it was confirmed that the pulse transformer has a stable and good performance in a wide temperature range from a low temperature range to a high temperature range.

  Next, sample Nos. 1 and 2 with different zinc oxide powder amounts and particle sizes added after calcination. 19-30 were produced and the test which measures the temperature change rate of a magnetic permeability and the magnetic permeability of room temperature (25 degreeC)-100 degreeC was implemented.

  FIG. 1A shows an outer diameter of 13 mm, an inner diameter of 7 mm, and a thickness of 3 mm according to the same production method as in Example 1 except that the amount and particle size of zinc oxide added after calcination were changed. Sample No. comprising the toroidal core 10 having the shape shown in FIG. 19-30 ferrite sintered bodies were obtained. The magnetic permeability and the temperature change rate of the magnetic permeability were measured by the same method as in Example 1.

In addition, the sample is cut and the cross section is mirror-finished, Zn is measured using a wavelength dispersive X-ray microanalyzer device (JXA-8100, manufactured by JEOL), and each analysis point within one field of view (70 μm × 70 μm) The mapping which recorded the intensity | strength of the characteristic X-ray detected by XY to the XY coordinate was obtained. When ZnO is present at the crystal grain boundary, the intensity of the characteristic X-ray of Zn is high in this mapping, so that it is 20% or more than the average value of the characteristic X-ray intensity of Zn in this mapping. The area occupied by ZnO present at the grain boundary is expressed by expressing the high part as ZnO at the grain boundary and dividing the area of this part by the viewing area of 4900 μm ² as a percentage. Asked. The results are shown in Table 2. In addition, about the main component composition of each sample, it confirmed that it was as having described in Table 2 by the method similar to Example 1. FIG.

  From the results in Table 2, the sample No. 1 in which the area occupancy of ZnO existing at the grain boundaries is 0.1% or more and 3% or less. Samples Nos. 20 to 24 and 26 to 30 have sample numbers of less than 0.1% or more than 3.0% of the occupied area of ZnO existing at the grain boundaries. It was confirmed that the magnetic permeability or the temperature change rate of the magnetic permeability was better than 19 and 25.

Next, with respect to the main component composition, the amount of zinc oxide added after calcining, and the particle size, sample No. Sample No. 28 is the same as sample No. 28, but the content in terms of MnO ₂ is varied. 31 to 38 were prepared, and the permeability was measured by the same method as in Example 1. The addition of MnO ₂ was performed during pulverization after calcination.

In addition, the main component composition was calculated by the same method as in Example 1 and confirmed to be as shown in Table 3. As for Mn, using a fluorescent X-ray analyzer, in terms of MnO ₂ in search of metallic element content was calculated mass for the main component of 100% by mass. The results are shown in Table 3.

From Table 3, it was found that the magnetic permeability can be improved by containing Mn in an amount of 0.05% by mass or more and 0.3% by mass or less in terms of MnO ₂ with respect to 100% by mass of the main component.

Next, for the main component composition, the content in terms of MnO ₂ , the added amount of zinc oxide added after calcining, and the particle size, sample No. Sample No. 33 was the same as Sample No. 33, but the content in terms of MoO ₃ was varied. 39 to 46 were prepared, and the permeability was measured by the same method as in Example 1. The addition of MoO ₃ was carried out in the same manner as MnO ₂ during pulverization after calcination.

Further, the main component composition was calculated by the same method as in Example 1 and confirmed to be as shown in Table 4. Further, Mn, for Mo, using a fluorescent X-ray analyzer, respectively seeking metal element content in terms of _MnO 2, MoO _3, was calculated mass for the main component of 100% by mass. The results are shown in Table 4.

From Table 4, it was found that the permeability can be improved by containing Mo in an amount of 0.01% by mass to 0.3% by mass in terms of MoO ₃ with respect to 100% by mass of the main component. In particular, sample no. 41-43 is obtained high magnetic permeability results showed the main component of 100 wt%, Mo was found that it is more preferred to contain 0.2 mass% or less than 0.05 wt% calculated as MoO _3.

1: ZnO (zinc oxide)
2: Ferrite crystal 3: Grain boundary
10: Toroidal core
10a: Winding part
20: Bobbin core

Claims (5)

Among the main component composition 100 mol%, Fe and _Fe 2 _{O 3} 50 mol% 49 mol% or more in terms of less, and Zn in terms of ZnO 32 mol% or more 34.5 mol% or less, the Ni in terms of NiO 6.5 Mol% or more and 12.5 mol% or less and Cu is contained in an amount of 5 mol% or more and 9 mol% or less in terms of CuO, and ZnO is present at the grain boundaries of the ferrite crystal composed of the main component. Ferrite sintered body.   2. The ferrite sintered body according to claim 1, wherein an area occupation ratio of the ZnO is 0.1% or more and 3% or less. 3. The ferrite sintered body according to claim 1, wherein Mn is contained in an amount of 0.05% by mass or more and 0.3% by mass or less in terms of MnO ₂ with respect to 100% by mass of the main component. The ferrite sintered body according to any one of claims 1 to 3, wherein Mo is contained in an amount of 0.01% by mass to 0.3% by mass in terms of MoO ₃ with respect to 100% by mass of the main component. .   A ferrite core comprising a ferrite sintered body according to any one of claims 1 to 4 wound with a metal wire.

Images