JP2014028710A - Ferrite sintered body and noise filter equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ferrite sintered body having an increased magnetic permeability, and to provide a noise filter formed by winding a metal wire around the ferrite sintered body having a high specific resistance and magnetic permeability.SOLUTION: A ferrite sintered body is made of Ni-Zn ferrite containing Ti, and the Ti is unevenly distributed in the vicinity of a grain boundary in crystal grains of the Ni-Zn ferrite. A noise filter is formed by winding a metal wire around the ferrite sintered body in which Ti is unevenly distributed in the vicinity of the grain boundary in crystal grains of the Ni-Zn ferrite and which has a component composition containing not less than 48 mol% and not more than 50 mol% of Fe, calculated as FeO, not less than 29 mol% and not more than 31 mol% of Zn, calculated as ZnO, not less than 14 mol% and not more than 16 mol% of Ni, calculated as NiO, and not less than 5 mol% and not more than 7 mol% of Cu, calculated as CuO, based on 100 mol% of the total amount of the components, and contains not less than 0.05 mass% and not more than 0.3 mass% of Ti, calculated as TiO, based on 100 mass% of the total amount of the components.

Description

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

  Ferrite sintered bodies made of a Ni—Zn ferrite material having a high specific resistance are widely used as cores for inductors, transformers, ballasts, electromagnets and the like.

  In particular, with the advent of vehicles with complex control systems such as electric cars and hybrid cars in recent years, electric circuits incorporated in control devices mounted on cars have become complicated, and electric circuits become complicated. In order to prevent the noise generated from the electric circuit from increasing and adversely affecting the electronic components on the circuit, the electric circuit is provided with a ferrite sintered body made of a Ni—Zn ferrite material as a core for noise removal. Many noise filters are used.

Then, the Ni-Zn-based ferrite material used in the core of such applications, for example, Patent Document 1, Fe, Ni, Zn, and Cu 48 to 50 mol% calculated as _Fe 2 _{O 3,} calculated as ZnO 0.16 to 1.0 part by weight of Ti in terms of TiO ₂ was contained with respect to 100 parts by weight of the main component containing 15 to 30% by mole, 7 to 35% by mole in terms of NiO, and 2 to 7% by mole in terms of CuO. Ni-Zn ferrite has been proposed.

Further, Patent Document 2, _Fe 2 _{O 3} is 49.0mol% ~50.0mol% as main composition, NiO is 10.0mol% ~15.0mol%, CuO is 5.0mol% ~8.0mol%, the balance being ZnO Ni In the ferrite system, Ti as an auxiliary component is 0.1% by weight or less in terms of TiO ₂ (0
Ni-Zn-based ferrites that contain no) have been proposed.

JP 2004-269316 A Japanese Patent Laid-Open No. 2002-321971

  The Ni—Zn based ferrites proposed in Patent Documents 1 and 2 can reduce the core loss at high temperature by containing Ti. In recent years, Ni—Zn based ferrites have a high specific resistance. In addition, the magnetic permeability is required to be higher, and this requirement is particularly high in the case of Ni—Zn-based ferrite that becomes the core of the noise filter.

  The present invention has been devised to satisfy the above-described requirements, and an object thereof is to provide a ferrite sintered body having an increased magnetic permeability. It is another object of the present invention to provide a noise filter formed by winding a metal wire around a ferrite sintered body having a high specific resistance and high magnetic permeability.

  The sintered ferrite body of the present invention is made of Ni—Zn-based ferrite containing Ti, and Ti is unevenly distributed in the vicinity of grain boundaries in crystal grains of the Ni—Zn-based ferrite.

Further, in the noise filter of the present invention, Ti is unevenly distributed in the vicinity of grain boundaries in the crystal grains of Ni-Zn ferrite, and the component composition range when the total is 100 mol% is Fe is Fe.
48 mol% or more and 50 mol% or less in terms of ₂ O ₃ , Zn is 29 mol% or more and 31 mol% or less in terms of ZnO, Ni is 14 mol% or more and 16 mol% or less in terms of NiO, and Cu is 5 mol% in terms of CuO 7 mol% or less, characterized in that a metal wire is wound around a sintered ferrite body containing 0.05 mass% or more and 0.3 mass% or less of Ti in terms of TiO ₂ with respect to a total of 100 mass% of the above components. It is.

  According to the ferrite sintered body of the present invention, since Ti is unevenly distributed in the vicinity of the grain boundary in the crystal grains of Ni-Zn ferrite, the magnetic permeability can be increased.

  Further, according to the noise filter of the present invention, a metal wire is wound around a ferrite sintered body having a high specific resistance and high magnetic permeability, whereby a noise filter having excellent noise removal performance can be obtained.

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.

  Hereinafter, the ferrite sintered body of the present invention and a noise filter including the same will be described. The ferrite sintered body of the present embodiment is used for the purpose of, for example, inductors, transformers, ballasts and electromagnets for noise insulation and voltage reduction, by winding a metal wire with the ferrite sintered body as a core. It is used for the noise filter.

  Here, there are various shapes of ferrite sintered bodies as cores. For example, the ring-shaped toroidal core 1 shown in the perspective view of FIG. 1A or the bobbin shown in the perspective view of FIG. Shaped bobbin core 2 and the like.

  Such a ferrite sintered body is required to increase the magnetic permeability, and is composed of Ni—Zn-based ferrite containing Ti. Ti is present in the vicinity of the grain boundary in the crystal grain of this Ni—Zn-based ferrite. By being unevenly distributed, a ferrite sintered body that satisfies the above-described requirements can be obtained.

  Here, the Ni-Zn ferrite is composed of Fe oxide, Zn oxide and Ni oxide, or Fe oxide, Zn oxide, Ni oxide and Cu oxide. Is. In the following, the components constituting the Ni—Zn-based ferrite described above may be collectively described as main components. Further, the vicinity of the grain boundary in the crystal grain means a range from the interface of the crystal grain to the range corresponding to 20% of the crystal grain diameter in each crystal grain, and the area other than the vicinity of the grain boundary is referred to as the inside. In the present embodiment, the uneven distribution means that more Ti exists near the grain boundary than in the crystal grain. Needless to say, even when Ti is not contained in the interior, it is unevenly distributed.

  Further, it is not clear why the magnetic permeability can be increased due to the uneven distribution of Ti in the vicinity of the grain boundaries in the crystal grains of the Ni—Zn-based ferrite. This is based on the knowledge that the magnetic permeability can be increased by Ti being unevenly distributed in the vicinity of the grain boundary as compared with the case where Ti is present throughout.

As a method for confirming the abundance of Ti in crystal grains made of Ni—Zn-based ferrite, a processed surface obtained by polishing the surface and cross section of the ferrite sintered body is observed with a transmission electron microscope (TEM). Then, using the attached energy dispersive X-ray spectrometer (EDS), by applying a spot (φ1 nm) inside the crystal grain and in the vicinity of the grain boundary, the mass in the spot of φ1 nm is 100% by mass. It is possible to know the abundance (mass ratio) of each element. Specifically, for example, when Fe, Zn, Ni, Cu, Ti, and O are detected, the abundance of each element can be confirmed, and the abundance of Ti at each of three points inside and near the grain boundary. Can be confirmed, and an average value can be obtained and compared.

Moreover, what is necessary is just to measure a sample on conditions with a frequency of 100 kHz about a magnetic permeability using a LCR meter. As a sample, for example, a ring-shaped toroidal core 1 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.

The ferrite sintered body of this embodiment has a component composition range when the total is 100 mol%, Fe is 48 mol% or more and 50 mol% or less in terms of Fe ₂ O ₃ , and Zn is 29 mol in terms of ZnO. % To 31 mol%, Ni to 14 mol% to 16 mol% in terms of NiO, and Cu to 5 mol% to 7 mol% in terms of CuO.
It is preferable to contain 0.05 mass% or more and 0.3 mass% or less in conversion of ₂ .

First, the component composition range when the total is 100 mol% is as follows: Fe is 48 mol% or more and 50 mol% or less in terms of Fe ₂ O ₃ , Zn is 29 mol% or more and 31 mol% or less in terms of ZnO, Ni is NiO A ferrite sintered body having a high specific resistance and a high magnetic permeability can be obtained by converting from 14 mol% to 16 mol% in terms of conversion and Cu from 5 mol% to 7 mol% in terms of CuO. And, Ti is unevenly distributed in the vicinity of the grain boundary in the crystal grains of the Ni-Zn ferrite, and the Ti content is 0.05% by mass or more and 0.3% by mass or less in terms of TiO ₂ , thereby having a high specific resistance. However, a ferrite sintered body with higher magnetic permeability can be obtained. In addition, it is preferable that content of these component composition occupies 98 mass% or more, when all the components which comprise a ferrite sintered compact are 100 mass%.

Here, in the confirmation of the abundance of Ti in the crystal grains of the Ni—Zn ferrite described above, for example, when the content of Ti with respect to the total of 100 mass% of the main components is 0.2 mass% in terms of TiO ₂ , Ti However, in the vicinity of the grain boundary in the crystal grains, an amount equivalent to several to several tens of times the total content of the main components with respect to 100% by mass (for example, 0.3 to 3.5%)
Ti exists. If the abundance in the vicinity of the grain boundary is large, the abundance of Ti in the interior is trace or not detected. Therefore, in such a Ti content, specifically, uneven distribution means that the amount of Ti present in the vicinity of the grain boundary is several times the content with respect to a total of 100% by mass of the main components, and the amount of Ti present in the interior Is less than 50% of the content relative to the total of 100% by mass of the main components.

As for the 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%.

The method for measuring the main component composition, ICP (Inductively Coupled Plasma) using emission spectrophotometer or fluorescence X-ray analyzer, Fe, Zn, Ni, seeking the content of Cu, respectively _Fe 2 _{O 3} It can be confirmed by converting to ZnO, NiO, and CuO, calculating the molar value from the respective molecular weights, and calculating the occupation ratio with respect to a total of 100 mol%. As for the Ti content, the content of Ti may be calculated using an ICP emission spectroscopic analyzer or a fluorescent X-ray analyzer, converted to TiO ₂ , and a value with respect to 100% by mass of the main component.

Next, details of an example of the method for producing a ferrite sintered body according to the present embodiment will be described below. The method for producing a ferrite material according to the present embodiment is as follows. First, as a starting material, an oxide of Fe, Zn and Ni, or a metal such as carbonate or nitrate that generates an oxide by firing is used to obtain a Ni-Zn ferrite. Prepare salt. In this case, the average particle size is preferably 0.5 μm or more and 5 μm or less when, for example, Fe is iron oxide (Fe ₂ O ₃ ), Zn is zinc oxide (ZnO), and Ni is nickel oxide (NiO). . When the Ni-Zn ferrite includes Cu oxide, a Cu oxide or a metal salt such as carbonate or nitrate that generates an oxide by firing is prepared. At this time, for example, when Cu is copper oxide (CuO), the average particle diameter is preferably 0.5 μm or more and 5 μm or less.

Here, in the method for producing a ferrite sintered body according to the present embodiment, silicon oxide (SiO ₂ ) having an average particle diameter of 0.5 to 10 μm is added to these starting materials. Then, each starting material and silicon oxide are weighed to a desired amount, pulverized and mixed with a ball mill or a vibration mill, and then 600 ° C.
The synthesized calcined body is obtained by calcining at a temperature of 800 ° C. or lower for 2 hours or longer. Thus, by adding silicon oxide to the starting material and performing calcination synthesis, Ti added after calcination can be unevenly distributed in the vicinity of the grain boundaries in the crystal grains of the Ni—Zn-based ferrite. In addition, the specific resistance is increased by including silicon oxide. On the other hand, when silicon oxide is not added or silicon oxide is added after calcination, Ti exists inside the crystal grains or in the entire vicinity of the grain boundaries, and the magnetic permeability cannot be increased.

In addition, in the ferrite sintered body, the component composition range when the total is 100 mol% is F.
e is 48 mol% or more and 50 mol% or less in terms of Fe ₂ O ₃ , Zn is 29 mol% or more and 31 mol% or less in terms of ZnO, Ni is 14 mol% or more and 16 mol% or less in terms of NiO, and Cu is in terms of CuO It is preferable to weigh so as to be 5 mol% or more and 7 mol% or less. Silicon oxide is preferably weighed so as to be 0.3% by mass or less (excluding 0% by mass) with respect to 100% by mass of the main component.

Next, a desired amount is weighed using an oxide of Ti having an average particle size of 0.5 to 10 μm or a metal salt such as carbonate or nitrate that forms Ti oxide by firing. In addition, it is preferable to weigh so that Ti is 0.05% by mass or more and 0.3% by mass or less in terms of TiO ₂ with respect to 100% by mass of the main component. And after putting into a ball mill, a vibration mill, etc. with a calcined body and mixing, a predetermined amount of binder is further added to make a slurry and granulated using a spray granulator (spray dryer) to obtain spherical granules.

  Next, this spherical granule is press-molded to obtain a molded body having a predetermined shape. And after performing the binder removal process in the range of 400-800 degreeC in the range of 400-800 degreeC in the obtained molded object, this is hold | maintained at the maximum temperature of 1000-1200 degreeC in a baking furnace for 2 to 5 hours. Then, the ferrite sintered body of the present embodiment can be obtained by firing.

In the ferrite sintered body of the present embodiment, _CaO, may contain ZrO 2, MnO _2. When CaO or ZrO ₂ is included, the specific resistance can be increased, and when MnO ₂ is included, the magnetic permeability can be increased. In addition, since CaO, ZrO ₂ and MnO ₂ are all contained in the ferrite sintered body, it is preferable that the content is less than 0.2% by mass with respect to 100% by mass of the main component. What is necessary is just to add to a calcined body so that it may become the range of this content.

Examples of the present invention will be specifically described below, but the present invention is not limited to these examples.

  Ferrite sintered bodies with different component compositions and manufacturing methods were produced, and the permeability was measured. First, iron oxide, zinc oxide, nickel oxide and copper oxide having an average particle diameter of 1 μm were prepared as starting materials. Moreover, silicon oxide was prepared.

Then, using iron oxide, zinc oxide, nickel oxide and copper oxide, weigh them so as to have the composition shown in Table 1, put them into a ball mill, pulverize and mix them, and then calcine them at a temperature of 700 ° C. or lower for 2 hours. Thus, a synthesized calcined body was obtained.

Further, using iron oxide, zinc oxide, nickel oxide and copper oxide, weighed so as to have the composition shown in Table 2, and silicon oxide was added so as to have the content shown in Table 2 with respect to 100% by mass of the main component. Weighed. And after putting into a ball mill and pulverizing and mixing, it was calcined at a temperature of 700 ° C. or lower for 2 hours to obtain a synthesized calcined body.

Next, titanium oxide was weighed so as to have the contents shown in Tables 1 and 2 with respect to 100% by mass of the main component, and mixed with a calcined body in a ball mill. Thereafter, a predetermined amount of a binder was added to form a slurry, which was granulated using a spray granulator to obtain spherical granules. And the molded object of the shape of the toroidal core 1 shown in FIG. 1 was obtained by press-molding using the obtained spherical granule.

Next, the resulting molded body was held in a degreasing furnace at a maximum temperature of 600 ° C. for 5 hours and subjected to a debinding process to obtain a degreased body, which was then heated in a firing furnace at the maximum temperature of 1100 ° C. Baked for 2 hours. The obtained sintered body was ground to obtain a toroidal ferrite sintered body (sample Nos. 1 to 44) having an outer diameter of 13 mm, an inner diameter of 7 mm, and a thickness of 3 mm. In Table 1, sample No. 1 and Sample 2 in Table 2. 23 differs from sample 23 only in the presence or absence of addition of silicon oxide to the starting material. 2 to 22 are sample Nos. Corresponds to 24-44.

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. Tables 1 and 2 show the results. It was. Then, the magnetic permeability of the sample without addition of silicon oxide shown in Table 1 is μ1, and the corresponding sample to which silicon oxide is added (for example, if Table 1 is Sample No. 1, Sample No. 23 in Table 2) Table 2 shows the values obtained by the calculation formula of (μ2−μ1) / μ1 × 100 as the improvement rate of the magnetic permeability.

  In addition to the shape, a measurement sample having a diameter of 16 mm and a thickness of 1 mm was separately prepared by the same manufacturing method as that of each sample, and an applied voltage of 1000 V, using a super insulation resistance meter (TOA DSM-8103), The specific resistance was measured by a three-terminal method (JIS K6271; double ring electrode method) in an environment of a temperature of 26 ° C. and a humidity of 36%, and the results are shown in Tables 1 and 2.

In addition, the surface of each sample cut is mirror-finished, observed with a transmission electron microscope (TEM), and an internal energy dispersive X-ray spectrometer (EDS) is used in the crystal grains and near the grain boundaries. Spots (φ1 nm) were applied to each of the three locations, and the abundance between the inside of the crystal grain and the vicinity of the grain boundary was confirmed by the average value. When the difference was less than 0.5%, “inside = grain boundary”, grain When the vicinity of the boundary is 0.5% or more, Table 1 and Table 2 indicate that “inside <near grain boundary”.

Also, for each sample, using a fluorescent X-ray analyzer, Fe, Zn, seeking metal element amount of Ni and Cu, respectively of iron oxide _{(Fe 2 O} 3), zinc oxide (ZnO), nickel oxide (NiO ), Converted into copper oxide (CuO), the molar value was calculated from the respective molecular weights, and the occupancy with respect to the total of 100 mol% was calculated and shown in Tables 1 and 2. Further, Ti was also measured using a fluorescent X-ray analyzer, converted to TiO ₂ , calculated with respect to 100% by mass of the main component, and the results are shown in Tables 1 and 2.

From Tables 1 and 2, it was found that the magnetic permeability can be increased by the uneven distribution of Ti in the vicinity of the grain boundaries in the crystal grains made of Ni-Zn ferrite. Also, the total is 100
The component composition range when the mol% is used is 48 mol% or more and 50 mol% or less in terms of Fe ₂ O ₃ , Zn is 29 mol% or more and 31 mol% or less in terms of ZnO, Ni is 14 mol% in terms of NiO It was found that a ferrite sintered body having a high specific resistance and high magnetic permeability can be obtained when the content is 16 mol% or less and Cu is 5 mol% or more and 7 mol% or less in terms of CuO. Further, Ti is unevenly distributed in the vicinity of the grain boundary in the crystal grains of the Ni—Zn-based ferrite, and the Ti content is 0.05% by mass or more and 0.3% by mass or less in terms of TiO ₂ , thereby having a high specific resistance. As a result, it was found that the improvement rate of magnetic permeability exceeded 10%, and a ferrite sintered body with higher magnetic permeability could be obtained.

  Sample No. Regarding No. 39, the presence of Ti inside the crystal grains was confirmed. About 23-38 and 40-44, presence of Ti was not confirmed inside. Accordingly, silicon oxide can be allowed to exist only in the vicinity of the grain boundaries in the crystal grains by weighing the silicon oxide so that the content in the ferrite sintered body is 0.05% by mass or more and adding it to the starting material. all right.

Sample No. When a ferrite sintered body of 25, 26 and 40 to 43 is used as a core, a metal wire is wound to form a noise filter, and it is incorporated into a control device that requires complex control such as an electric vehicle or a hybrid car. It was found that this is a noise filter with excellent noise removal performance.

1: Toroidal core 1a: Winding part 2: Bobbin core 2a: Winding part

Claims (3)

A ferrite sintered body comprising Ni—Zn-based ferrite containing Ti, wherein Ti is unevenly distributed in the vicinity of grain boundaries in crystal grains of the Ni—Zn-based ferrite. The component composition range when the total is 100 mol% is Fe 48 mol% or more and 50 mol% or less in terms of Fe ₂ O ₃ , Zn is 29 mol% or more and 31 mol% or less in terms of ZnO, Ni is NiO equivalent 14 mol% or more and 16 mol% or less, and Cu is 5 mol% or more and 7 mol% or less in terms of CuO, and Ti is 0.05 mass% or more in terms of TiO _{2 and} 0.3 to 0.3 mol with respect to a total of 100 mass% of the above components. 2. The ferrite sintered body according to claim 1, wherein the ferrite sintered body is contained by mass% or less. A noise filter obtained by winding a metal wire around the ferrite sintered body according to claim 2.

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