JP2010047438A - MnZn FERRITE AND MnZn FERRITE CORE - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide MnZn ferrite and an MnZn ferrite core which can obtain high initial magnetic permeability over a broad frequency band. <P>SOLUTION: In the surface of the fired body of MnZn ferrite contains, as auxiliary components, SiO<SB>2</SB>of 0 to 0.005 pts.wt.(excluding zero), CaO of 0.02 to 0.2 pts.wt., MoO<SB>3</SB>of 0.05 to 0.5 pts.wt., Bi<SB>2</SB>O<SB>3</SB>of 0.005 to 0.1 pts.wt. and V<SB>2</SB>O<SB>5</SB>of 0.005 to 0.1 pts.wt., based on 100 pts.wt. of the main components composed of MnO, ZnO and Fe<SB>2</SB>O<SB>3</SB>, a precipitated phase including MoO<SB>3</SB>and CaO is contained, and, by controlling the average crystal grain size to 30 to 100 μm and controlling the specific resistance of the fired body to 20 to 100 Ωcm, the MnZn ferrite core in which initial magnetic permeability at 1 kHz is ≥12,000 and initial magnetic permeability at 150 kHz is ≥12,500 can be obtained. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a high magnetic permeability MnZn ferrite, and more particularly to a MnZn ferrite suitable as a ferrite core for a noise filter.

  2. Description of the Related Art In recent years, technological innovations for downsizing and high performance of electronic devices have been remarkable, and there has been a demand for high performance, for example, high magnetic permeability and low loss of Mn—Zn ferrite used therewith. Especially, the ferrite core for noise filters is required to exhibit a high initial permeability over a wide frequency band.

In order to obtain high initial permeability, it is necessary to increase the average crystal grain size. In order to increase the crystal grain size, a method of adding an appropriate amount of various grain growth additives such as Bi ₂ O ₃ is used for the purpose of promoting grain growth (for example, Patent Documents 1 and 2). 3).

Patent Document 1 proposes a high-permeability MnZn ferrite in which SiO ₂ , CaO, MoO ₃ , and Bi ₂ O ₃ are added as additives to the main component composed of MnO, ZnO, and Fe ₂ O _3. Yes. In Patent Document 2, 52.0 to 53.0 mol% FeO ₃ , 19.0 to 23.5 mol% ZnO, and the main component consisting of MnO as the balance, SiO ₂ , CaO, Bi ₂ as subcomponents. A high permeability oxide magnetic material has been proposed in which O ₃ is added and a reducing agent is further added. Patent Document 3 proposes a magnetic material having a high magnetic permeability in which Fe ₂ O ₃ , MnO, and ZnO are main components and Bi ₂ O ₃ and V ₂ O ₅ are added as subcomponents thereto. In these documents, Bi ₂ O ₃ is added for the purpose of increasing the crystal grain size.

JP 2008-094663 A JP 2002-093614 A JP-A-56-160330

  On the other hand, in order to obtain a high initial permeability in a wide frequency band up to a high frequency band, it is necessary to increase the specific resistance of the material.

  Eddy current loss increases with increasing frequency, and the initial permeability decreases in the high frequency band. An effective means for preventing this is to increase the resistance of the material, thereby improving the frequency characteristics of the initial permeability in the high frequency band.

  For this reason, generally, a method is used in which an additive that precipitates at the grain boundary is added to increase the specific resistance of the grain boundary and to obtain a high initial permeability in a wide frequency band.

  As described above, the method using various grain growth additives is effective for increasing the crystal grain size and obtaining high initial permeability. However, the grain growth additive is also an abnormal grain growth promoting factor, and abnormal grains are easily generated. Abnormal grains increase eddy current loss and lead to a decrease in specific resistance, resulting in a decrease in initial permeability in a high frequency band.

  In order to increase the crystal grain size, a method of increasing the firing temperature is effective. However, if the firing temperature is too high, ZnO volatilizes from the surface of the fired body, resulting in distortion due to the resulting composition gradient, leading to a decrease in initial permeability.

  As described above, in general, a material having a high initial permeability in a low frequency band has a problem that it is difficult to maintain a high initial permeability up to a high frequency band, and a high initial permeability in a wide frequency band. It is desired to obtain magnetic permeability.

  The present invention has been made to solve such problems, and a technical problem thereof is to provide a MnZn ferrite and a MnZn ferrite core having high initial permeability in a wide frequency band.

As a result of various investigations, in the MnZn ferrite whose main component is MnO, ZnO, Fe ₂ O ₃ , SiO ₂ is contained in an amount of 0 to 0.005 parts by weight (0% as a subcomponent with respect to 100 parts by weight of the main component). CaO is 0.02 part by weight to 0.2 part by weight, MoO ₃ is 0.05 part by weight to 0.5 part by weight, and Bi ₂ O ₃ is 0.005 part by weight to 0.1 part by weight. , Having a precipitated phase containing MoO ₃ and CaO on the surface of the sintered body of MnZn ferrite containing 0.005 to 0.1 parts by weight of V ₂ O ₅ , and having an average crystal grain size of 30 μm or more and 100 μm or less By setting the specific resistance of the fired body to 20 Ωcm or more and 100 Ωcm or less, an MnZn ferrite core having an initial permeability of 12,000 or more at 1 kHz and an initial permeability of 12,500 or more at 150 kHz can be obtained. I found it. Hereinafter, the “parts by weight” of the additive as a subsidiary component when the main component is 100 parts by weight will be simply expressed by “wt%”.

That is, according to the present invention, the main component is MnZn ferrite whose main component is MnO, ZnO, Fe ₂ O ₃ , and SiO ₂ is 0 to 0.005 part by weight as a subcomponent with respect to 100 parts by weight of the main component. (Excluding 0), CaO 0.02 to 0.2 parts by weight, MoO ₃ 0.05 to 0.5 parts by weight, Bi ₂ O ₃ 0.005 to 0.1 parts by weight MnZn ferrite characterized by containing 0.005 parts by weight to 0.1 parts by weight of V ₂ O ₅ by weight is obtained.

In addition, MnZn ferrite having a precipitated phase containing MoO ₃ and CaO on the surface of the sintered body of MnZn ferrite and having an average crystal grain size of 30 μm or more and 100 μm or less is obtained.

  Moreover, it is a MnZn ferrite core which consists of a sintered body of MnZn ferrite, The specific resistance of the said sintered body is 20 ohm-cm or more and 100 ohm-cm or less, The MnZn ferrite core characterized by the above-mentioned is obtained.

  Further, it is a MnZn ferrite core made of a sintered body of MnZn ferrite, wherein the sintered body has an initial permeability at 1 kHz of 12,000 or more and an initial permeability at 150 kHz of 12,500 or more. A MnZn ferrite core is obtained.

According to the product of the present invention, SiO ₂ added to MnZn ferrite is 0 to 0.005 wt% (not including 0) and CaO is 0.02 wt% to 0.2 wt% to inhibit crystal grain growth. Therefore, since a high-resistance grain boundary layer can be formed, eddy current loss can be reduced. As a result, a MnZn ferrite core having a high initial permeability even in a high frequency band can be obtained.

Further, MnZn ferrite containing 0.05 wt% to 0.5 wt% of MoO ₃ , 0.005 to 0.1 wt% of V ₂ O _5, and 0.005 wt% to 0.1 wt% of Bi ₂ O ₃ is used. As a result, the crystal grain size can be increased at a firing temperature at which ZnO does not volatilize from the surface of the fired body, so that a MnZn ferrite core having a high initial permeability can be obtained.

Bi ₂ O ₃ and V ₂ O ₅ are crystal grain growth additives and additives that generate abnormal grains. MoO ₃ has a sizing action, and has an effect of enlarging crystal grains while suppressing abnormal grain growth caused by Bi ₂ O ₃ and V ₂ O ₅ . Patent Document 1 is an invention in which only one of Bi ₂ O ₃ is added. Adding a proper amount of Bi ₂ O _{3 and} an appropriate amount of MoO ₃ as a crystal grain growth additive further adds a crystal grain growth additive. Although it was thought that abnormal grain growth was promoted, according to the present invention, a MnZn ferrite core having a good crystal grain size can be obtained.

Further, the obtained sintered body of MnZn ferrite has a precipitated phase containing MoO ₃ and CaO on its surface, the average crystal grain size is 30 μm or more and 100 μm or less, and the specific resistance of the sintered body is 20 Ωcm or more and 100 Ωcm or less. Therefore, an MnZn ferrite core having an initial permeability of 12,000 or more at 1 kHz and an initial permeability of 12,500 or more at 150 kHz can be obtained. Since the product of the present invention described above is a MnZn ferrite core having a high initial permeability in a wide frequency band, a small and high-performance noise filter can be provided when used as a ferrite core for a noise filter.

As a result of various investigations, in the MnZn ferrite whose main component is MnO, ZnO, Fe ₂ O ₃ , SiO ₂ is added as 0 to 0.005 parts by weight (0% as a subcomponent with respect to 100 parts by weight of the main component). CaO is 0.02 part by weight to 0.2 part by weight, MoO ₃ is 0.05 part by weight to 0.5 part by weight, and Bi ₂ O ₃ is 0.005 part by weight to 0.1 part by weight. , Having a precipitated phase containing MoO ₃ and CaO on the surface of the sintered body of MnZn ferrite containing 0.005 parts by weight to 0.1 parts by weight of V ₂ O ₅ , and having an average crystal grain size of 30 μm or more and 100 μm or less By setting the specific resistance of the fired body to 20 Ωcm or more and 100 Ωcm or less, an MnZn ferrite core having an initial permeability of 12,000 or more at 1 kHz and an initial permeability of 12,500 or more at 150 kHz can be obtained. all right.

In general, the composition range of the main component of MnZn ferrite having a high magnetic permeability is, 52.0～54.5Mol% of Fe ₂ O _3, 24.0~28.0mol% of MnO, 19.5mol% ~24.0mol In the present invention, it is desirable that the main component is in the above-described composition range since a composition in the vicinity of% ZnO is manufactured as a high magnetic permeability material.

The reason why SiO ₂ is set to 0 to 0.005 wt% (not including 0) as a subcomponent is that when it exceeds 0.005 wt%, crystal grain growth is inhibited and the initial permeability is remarkably lowered.

  The reason why CaO is 0.02 wt% to 0.2 wt% is that if it is less than 0.02 wt%, since the grain boundary layer formation is insufficient, the specific resistance becomes low, and the increase in eddy current loss causes the high frequency band This is because the initial magnetic permeability at the time is reduced and a high initial magnetic permeability cannot be obtained in a wide frequency band. Further, if it exceeds 0.2 wt%, excess CaO inhibits crystal grain growth, and sufficient initial permeability cannot be obtained.

Bi ₂ O ₃ is 0.005 wt% to 0.1 wt% and V ₂ O ₅ is 0.005 wt% to 0.1 wt% because Bi ₂ O ₃ is less than 0.005 wt% and V ₂ O ₅ is If the content is less than 0.005 wt%, the crystal grain growth effect brought about by Bi ₂ O ₃ and V ₂ O ₅ cannot be obtained, which leads to a reduction in initial permeability. Further, when Bi ₂ O ₃ exceeds 0.1 wt% and V ₂ O ₅ exceeds 0.1 wt%, abnormal grain growth caused by Bi ₂ O ₃ and V ₂ O ₅ becomes remarkable, and the initial permeability is reduced. This is because the specific resistance is reduced.

The a MoO ₃ was 0.05 wt% to 0.5 wt%, when MoO ₃ is less than 0.05 wt%, to inhibit the sizing action of MoO _3, resulting in the _{Bi 2 O 3, V 2 O} 5 This is because abnormal grain growth becomes remarkable, leading to a decrease in magnetic permeability and a decrease in specific resistance. This is because if MoO ₃ exceeds 0.5 wt%, the grain growth effect brought about by Bi ₂ O ₃ and V ₂ O ₅ cannot be obtained, and the initial permeability is reduced.

  Moreover, in the obtained MnZn ferrite, the average grain size of the fired body was set to 30 μm or more and 100 μm or less because when the average crystal grain size is less than 30 μm, the crystal grain size is small, so that sufficient initial permeability can be obtained. It is because it is not possible. In addition, if the average crystal grain size exceeds 100 μm, the formation of the grain boundary layer is insufficient, so the specific resistance is lowered, and the initial permeability in the high frequency band is reduced due to the increase in eddy current loss. This is because high initial permeability cannot be obtained.

  The specific resistance of the fired body is set to 20 Ωcm or more and 100 Ωcm or less. If the specific resistance is less than 20 Ωcm, the initial permeability in a high frequency band is reduced due to an increase in eddy current loss, and a high initial permeability is obtained in a wide frequency band. This is because the magnetic susceptibility cannot be obtained. Further, if the specific resistance exceeds 100 Ωcm, the crystal grain size is small, so that sufficient initial permeability cannot be obtained.

Although it is unknown in detail about the precipitation phase containing MoO ₃ and CaO present on the surface of the sintered body of MnZn ferrite, MoO ₃ is a volatile additive and is a eutectic mixture between CaO as a grain boundary component and the surface of the sintered body. It is presumed that In the experimental results of the present inventors, in the case of the invention product showing a high initial permeability, a precipitated phase containing MoO ₃ and CaO is found on the surface. It is desirable that a precipitated phase containing MoO ₃ and CaO exists on the surface of the body.

Example 1
As an invented product, a main component composed of 52.5 mol% Fe ₂ O ₃ , 22.5 mol% ZnO, 25.0 mol% MnO, and 0 to 0 as subcomponents in the outer frame with respect to these main components 0.006 wt% SiO ₂ , 0.01 wt% to 0.21 wt% CaO, 0.04 wt% to 0.6 wt% MoO ₃ , 0.004 wt% to 0.15 wt% Bi ₂ O ₃ , 0 to 0.15 wt% V ₂ O ₅ was added and mixed for 2 hours using an attritor.

  After mixing, the mixture was granulated with a spray dryer and pre-fired in the air at 850 ° C. for 2 hours. The pre-baked powder obtained was pulverized with an attritor. After pulverization, it was granulated with a spray dryer, pressed into a toroidal shape of φ25 mm-φ15 mm-12 mm, and fired at 1320 ° C.

As a conventional product, a main component composed of 52.5 mol% Fe ₂ O ₃ , 22.5 mol% ZnO, and 25.0 mol% MnO is used. .015 wt% SiO ₂ , 0.015 wt% CaO and 0.015 wt% Bi ₂ O ₃ were added and mixed for 2 hours using an attritor. After mixing, the mixture was granulated with a spray dryer and pre-baked in an air at 850 ° C. for 2 hours. The obtained prefired powder was pulverized with an attritor. After pulverization, it was granulated with a spray dryer, pressed into a toroidal shape of φ25 mm-φ15 mm-12 mm, and fired at 1320 ° C.

  For magnetic properties, the obtained MnZn ferrite fired body was wound with 10 turns and the initial permeability was measured. The specific resistance was measured by applying a Ga-In paste on the upper and lower surfaces of the sample. Moreover, the analysis of the surface precipitation phase was performed by SEM-EDX and X-ray diffraction.

Table 1 shows the initial magnetic permeability at 1 kHz and 150 kHz for the average crystal grain size, specific resistance, and 1 kHz and 150 kHz of the conventional product and the inventive product in which the addition amount of SiO ₂ , CaO, MoO ₃ , Bi ₂ O ₃ , and V ₂ O ₅ is changed In the table). In Table 1, the amount of the auxiliary component added is within the scope of the present invention, and the outside of the range is the comparative product.

As shown in Table 1, SiO ₂ is 0 to 0.005 wt% (not including 0), CaO is 0.02 wt% to 0.2 wt%, MoO ₃ is 0.05 wt% to 0.5 wt%, Bi ₂ Invented product containing 0.005 wt% to 0.1 wt% of O _{3 and} 0.005 wt% to 0.1 wt% of V ₂ O ₅ , the average crystal grain size of the sintered body is 30 μm to 100 μm, specific resistance 20Ωcm or more and 100Ωcm or less, the initial permeability at 1 kHz is 12,000 or more, and the initial permeability at 150 kHz is 12,500 or more. Moreover, the composition analysis of the surface of the fired body was performed by SEM-EDX analysis, and as a result of further X-ray diffraction, it was confirmed that the precipitated phases of MoO ₃ and CaO were present in all invention products.

  FIG. 1 shows the frequency characteristics of the complex magnetic permeability μ ′ (real part) and μ ″ (imaginary part) of the inventive product 6 and the conventional product. The inventive product has a higher frequency from a lower frequency band than the conventional product. It was confirmed that both complex permeability μ ′ and μ ″ showed high values in a wide frequency band.

(Example 2)
As an invention, a main component composed of 52.5 mol% Fe ₂ O ₃ , 22.5 mol% ZnO, and 25.0 mol% MnO has an outer frame and subcomponents as 0 Add 0.001 wt% SiO ₂ , 0.07 wt% CaO, 0.2 wt% MoO ₃ , 0.05 wt% Bi ₂ O ₃ , 0.02 wt% V ₂ O ₅ and use an attritor. Mixed for 2 hours.

  After mixing, the mixture was granulated with a spray dryer and pre-fired in the air at 850 ° C. for 2 hours. The pre-baked powder obtained was pulverized with an attritor. After pulverization, it was granulated with a spray dryer, pressed into a toroidal shape of φ25 mm−φ15 mm-12 mm, and fired at 1300 ° C. to 1450 ° C.

As a conventional product, a main component composed of 52.5 mol% Fe ₂ O ₃ , 22.5 mol% ZnO, and 25.0 mol% MnO is used. .015 wt% SiO ₂ , 0.015 wt% CaO and 0.015 wt% Bi ₂ O ₃ were added and mixed for 2 hours using an attritor. After mixing, the mixture was granulated with a spray dryer and pre-fired in the air at 850 ° C. for 2 hours. The obtained prefired powder was pulverized with an attritor. After pulverization, it was granulated with a spray dryer, pressed into a toroidal shape of φ25 mm-φ15 mm-12 mm, and fired at 1320 ° C.

  As for the magnetic properties, the obtained sintered body was wound with 10 turns, and the initial permeability was measured. The specific resistance was measured by applying a Ga-In paste on the upper and lower surfaces of the sample. Moreover, the analysis of the surface precipitation phase was performed by SEM-EDX and X-ray diffraction.

  Table 2 shows the average crystal grain size, specific resistance, and initial permeability at 1 kHz and 150 kHz (indicated by μ in the table) of the conventional product and the invention product with different firing temperatures.

  As shown in Table 2, even when the firing temperature is changed, the average crystal grain size of the fired body is 30 μm or more and 100 μm or less, and the specific resistance is 20Ωcm or more and 100Ωcm or less. It was confirmed that the magnetic permeability was 12,000 or more and the initial permeability at 150 kHz was 12,500 or more. According to the MnZn ferrite of the present invention, since the crystal grain size can be increased at a normal firing temperature at which ZnO does not volatilize from the surface of the fired body, it is found that a MnZn ferrite core having a high initial permeability can be obtained. It was.

Moreover, as a result of performing compositional analysis on the surface of the fired body by SEM-EDX analysis and further performing X-ray diffraction, it was confirmed that MoO ₃ and CaO precipitated phases were present in all the invention products.

  From the above results, it was confirmed that the MnZn ferrite of the present invention has a high initial permeability in a wide frequency band as compared with the conventional product. Further, by employing the MnZn ferrite of the present invention, it is possible to provide a small and high performance ferrite core for noise filters.

Frequency characteristics of the complex permeability μ ′ (real part) and μ ″ (imaginary part) of Invention 6 and the conventional product.

Claims (4)

It is MnZn ferrite whose main component is MnO, ZnO, Fe ₂ O ₃ , and SiO ₂ is 0 to 0.005 part by weight (excluding 0) as a subcomponent with respect to 100 parts by weight of the main component, CaO There 0.02 part by weight to 0.2 parts by weight, MoO ₃ 0.05 part by weight to 0.5 parts by weight, Bi ₂ O ₃ is 0.005 part by weight to 0.1 parts by weight, V ₂ O ₅ MnZn ferrite characterized by containing 0.005 weight part-0.1 weight part. A MnZn ferrite having a precipitated phase containing MoO ₃ and CaO on the surface of the sintered body of MnZn ferrite according to claim 1 and having an average crystal grain size of 30 μm or more and 100 μm or less.   2. A MnZn ferrite core comprising the fired body of MnZn ferrite according to claim 1, wherein the fired body has a specific resistance of 20 [Omega] cm to 100 [Omega] cm.   2. An MnZn ferrite core comprising the sintered body of MnZn ferrite according to claim 1, wherein the sintered body has an initial permeability of 12,000 or more at 1 kHz and an initial permeability of 12,500 or more at 150 kHz. The MnZn ferrite core characterized by the above-mentioned.

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