JP5717056B2 - Ferrite porcelain manufacturing method - Google Patents

Description

The present invention relates to the production how ferrite porcelain, and more particularly to a method of manufacturing a ferrite ceramic containing at least NiO and Fe ₂ O _3.

  Conventionally, Ni—Cu—Zn-based ferrite porcelain has been widely used for core members (magnetic cores) of single-plate coil parts, laminated inductors, composite laminated parts, and the like, and ferrite materials have been actively developed.

For example, Patent Document 1 discloses that Fe ₂ O ₃ is 47.5 mol% to 50.5 mol%, NiO is 18.0 mol% to 34.0 mol%, ZnO is 12.0 mol% to 28.0 mol%, and CuO is 1 A ferrite core for a noise filter having a composition of 0.5 mol% to 10.0 mol% and an average equivalent circle diameter of sintered grains of 1 μm to 5 μm has been proposed.

In Patent Document 1, by firing in an air atmosphere, a ferrite core having a specific resistance ρ of 10 ⁶ Ω · cm or more and a room temperature saturation magnetization of 440 mT or more is obtained. Patent Document 1 describes that it is effective to reduce the content of CuO in order to improve saturation magnetization.

  That is, in a coil component using a ferrite porcelain as a core member, it is important to obtain a stable inductance L even when a large current is applied. To that end, a large direct current is applied to the coil. However, it is necessary to have a DC superposition characteristic that suppresses a decrease in inductance L. In order to obtain good DC superposition characteristics that can maintain the DC superposition characteristics up to a high magnetic field, it is necessary to improve the saturation magnetization (saturation magnetic flux density Bs).

  And in patent document 1, by using a ferrite material with high saturation magnetization of 440 mT or more, it can suppress that an inductance falls even when a large current is sent through a coil, and this is suitable for a high current use. Ferrite porcelain can be realized.

  Also, in Patent Document 2, the raw material composition of the ferrite base is a copper conductor integrated firing in which a PbO component is added in a proportion of 0.3 parts by weight or more and 5.0 parts by weight or less with respect to 100 parts by weight of Ni—Zn ferrite. Type ferrite elements have been proposed.

Further, in Patent Document 2, the raw material composition of the ferrite base is such that the PbO component is 0.3 to 5.0 parts by weight and the B ₂ O ₃ component is 0 with respect to 100 parts by weight of the Ni—Zn ferrite. A copper conductor-integrated sintered ferrite element to which 0.03 to 1.5 parts by weight and a SiO ₂ component are added in a proportion of 0.03 to 1.5 parts by weight has been proposed.

In Patent Document 2, by adding a low melting point glass component of PbO, PbO, B ₂ O ₃ , or SiO _{2 to} the ferrite material, firing at a low temperature of 950 to 1030 ° C. is possible in a nitrogen atmosphere. .

JP 2002-343620 A (Claim 6, Claim 4, Table 2) Japanese Examined Patent Publication No. 7-97525 (Claim 1, Claim 2, (3), page 5, column 5 line 7 to page 8)

  However, in Patent Document 1, although the saturation magnetization is improved by reducing the content of CuO, the firing temperature is set to, for example, 1050 to 1250 when the content of CuO having a melting point as low as 1026 ° C. is decreased. There was a problem from the viewpoint of energy saving and cost reduction because it had to be raised to about ℃.

Further, in Patent Document 2, since glass components PbO, B ₂ O ₃ , and SiO ₂ are added, these glass components cause abnormal grain growth during the firing process, resulting in a decrease in magnetic permeability, etc. Therefore, there has been a problem that desired good magnetic properties cannot be obtained.

  Moreover, in Patent Document 2, since PbO is contained in the ferrite, there is a problem in terms of environmental load.

The present invention has been made in view of such circumstances, and it is a ferrite having good sinterability and insulating property by low-temperature firing at 1000 ° C. or less and good DC superposition characteristics without adding a glass component. and its object is to provide a manufacturing how of porcelain.

In order to achieve the above object, the present inventors have conducted extensive research using a Ni-based ferrite material. The content of CuO in the ferrite powder is 0.5 to 1.75 mol%, and the content of ZnO. When the atmosphere was adjusted to an oxygen concentration of 0.001 to 0.1% by volume and baked without adding a glass component, sinterability and insulation were achieved at a low temperature firing of 1000 ° C. or lower. It was found that a ferrite ceramic having good DC superposition characteristics having a good saturation and a saturation magnetic flux density of 480 mT or more can be obtained.

The present invention has been made on the basis of such knowledge, and the method for producing a ferrite porcelain according to the present invention is a method for producing a ferrite porcelain containing at least Fe ₂ O ₃ and NiO, wherein a glass component is added. Without adding Fe ₂ O ₃ and NiO, a ferrite powder was prepared by mixing CuO in a range of 0.5 to 1.75 mol% and ZnO in a range of 10 to 28 mol%, and the ferrite powder was molded. Thereafter, firing is performed at a firing temperature of 1000 ° C. or less in an atmosphere having an oxygen concentration of 0.001 to 0.1% by volume, a saturation magnetic flux density is 480 mT or more , and a specific resistance is 1.0 × 10 ⁷ Ω · cm or more. It is characterized by the production of ferrite porcelain.

Further, as a result of further diligent research by the present inventors, it is possible to further improve the DC superposition characteristics by adding SnO ₂ in a range of 1.3 parts by weight or less with respect to 100 parts by weight of the ferrite powder. I understood.

That is, in the method for producing a ferrite porcelain of the present invention, it is preferable to add SnO ₂ in a range of 1.3 parts by weight or less with respect to 100 parts by weight of the ferrite powder.

In the method for manufacturing a ferrite porcelain of the present invention, the content of Fe ₂ O ₃ is preferably 44 to 49.8 mol%.

According to the above method for producing a ferrite porcelain, a glass component is not added, but in addition to Fe ₂ O ₃ and NiO, CuO is mixed in a range of 0.5 to 1.75 mol% and ZnO is mixed in a range of 10 to 28 mol%. powder was prepared, after forming process the ferrite powder, the oxygen concentration is fired at a firing temperature of 1000 ° C. or less in an atmosphere of 0.001 to 0.1 vol%, the saturation magnetic flux density of not less than 480 mT, and the ratio Since a ferrite porcelain having a resistance of 1.0 × 10 ⁷ Ω · cm or more is manufactured, good sinterability can be obtained even if the ferrite composition does not contain a glass component, and at a low temperature of 1000 ° C. or less. It is possible to manufacture a ferrite porcelain having a high saturation magnetic flux density Bs and a good direct current superposition characteristic while ensuring good insulation even when fired.

  In addition, since no glass component is contained in the ferrite powder, it is possible to ensure good magnetic properties without causing abnormal grain growth during firing and hence without causing a decrease in magnetic permeability. And since it does not contain the Pb system component as a glass component, it does not cause environmental pollution.

Further, by adding SnO ₂ in a range of 1.3 parts by weight or less with respect to 100 parts by weight of the ferrite powder, the saturation magnetic flux density is further improved, and thereby a desired ferrite porcelain having further improved direct current superposition characteristics is obtained. Can be manufactured.

It is sectional drawing which shows one Embodiment of the coil components manufactured using the manufacturing method of the ferrite porcelain of this invention. It is a figure which shows the relationship between content of CuO at the time of baking in air | atmosphere atmosphere, and a sintered density. It is a figure which shows the relationship between content of CuO at the time of baking in an atmospheric condition, and specific resistance. It is a figure which shows the relationship between content of CuO at the time of baking in the atmosphere of oxygen concentration 0.1 volume%, and a sintering density. It is a principal part enlarged view of FIG. It is a figure which shows the relationship between content of CuO at the time of baking in the atmosphere of oxygen concentration 0.1 volume%, and a specific resistance. It is a figure which shows the relationship between content of CuO, and a saturation magnetic flux density. It is a figure which shows the relationship between content of CuO, and the increase rate of saturation magnetic flux density.

  Next, an embodiment of the present invention will be described in detail.

The ferrite porcelain as one embodiment of the present invention is formed of a Ni—Zn—Cu based ferrite material containing Fe ₂ O ₃ , NiO, ZnO, and CuO.

And in this Embodiment, it mix | blends so that content of CuO in a ferrite composition may be 0.5-1.75 mol% .

Here, the reason why the content of CuO in the ferrite composition is set to 0.5 to 1.75 mol% as described above is as follows.

  A coil component using a ferrite porcelain as a core material is required to have good DC superposition characteristics such that the DC superposition characteristics can be maintained up to a high magnetic field. For this purpose, the ferrite porcelain needs to have a high saturation magnetic flux density Bs. As described in Patent Document 1, in order to increase the saturation magnetic flux density Bs, it is effective to reduce the CuO content.

However, when the CuO content exceeds 1.75 mol%, a sufficiently high saturation magnetic flux density Bs cannot be obtained. On the other hand, when the CuO content is less than 0.5 mol%, if sintered at a low temperature of 950 ° C., the sintered density is reduced to 5.10 g / cm ³ or less, which may cause a decrease in sinterability.

Therefore, in the present embodiment, the composition components are blended so that the CuO content is 0.5 to 1.75 mol% .

Furthermore, in this Embodiment, it mix | blends so that content of ZnO in a ferrite composition may be 10-28 mol%. If the ZnO content is less than 10 mol%, the magnetic permeability may be reduced, while if it exceeds 28 mol%, the saturation magnetic flux density Bs may be reduced.

Further, the contents of Fe ₂ O ₃ and NiO in the ferrite composition are not particularly limited, but from the viewpoint of obtaining desired characteristics, Fe ₂ O ₃ : 44 to 49.8 mol%, NiO: the balance It is preferable to blend so that. When the content of Fe ₂ O ₃ is less than 44 mol%, the magnetic permeability may be decreased, and when it exceeds 49.8 mol%, the sinterability may be decreased.

Furthermore, in the present invention, it is also preferable to add SnO ₂ to the ferrite powder, and it becomes possible to obtain a ferrite porcelain with further improved direct current superposition characteristics. In this case, in order to obtain a desired property improvement, SnO ₂ needs to be added at least 0.3 parts by weight or more with respect to 100 parts by weight of the ferrite powder. However, when the amount exceeds 1.3 parts by weight with respect to 100 parts by weight of the ferrite powder, the magnetic permeability is significantly reduced. Thus when adding SnO ₂ is from 0 · 3 to 1.3 parts by weight based on the ferrite powder 100 parts by weight is preferred.

  The ferrite porcelain is fired in a nitrogen atmosphere having an oxygen concentration of 0.1% by volume or less, so that it has good sinterability and insulation even when fired at a low temperature of 1000 ° C. or less, and direct current superposition. A ferrite porcelain having good characteristics can be obtained.

  Next, the manufacturing method of the ferrite porcelain will be described in detail.

First, as ceramic raw _materials, Fe ₂ O 3, ZnO, prepared NiO, and CuO, for example, _{Fe 2 O 3: 44~49.8mol%,} ZnO: 10~28mol%, CuO: 0.5~1. 75 mol%, NiO: These ceramic raw materials are weighed so as to be the balance, and a predetermined amount of SnO ₂ is weighed if necessary.

  Next, these weighed materials are put into a ball mill together with pure water and cobblestones such as PSZ (Partial Stabilized Zirconia) balls, sufficiently mixed and pulverized wet, evaporated and dried, and then at a temperature of 700 to 800 ° C. Calcination is performed for a predetermined time to obtain a calcined product.

  Next, the calcined product is sufficiently wet pulverized again in a ball mill, an appropriate amount of an organic binder such as polyvinyl alcohol is added, and is molded using a pressure press or the like to obtain a ceramic molded body.

Next, the obtained ceramic molded body was fired at a temperature of 950 to 1000 ° C. for 2 to 3 hours in an N ₂ —O ₂ mixed gas atmosphere adjusted to an oxygen concentration of 0.1% by volume or less. Can be produced.

  Here, the reason for setting the firing atmosphere to an oxygen concentration of 0.1% by volume or less is as follows.

  By reducing the oxygen concentration during firing, oxygen defects are formed in the crystal structure, and interdiffusion of Fe, Ni, Cu, and Zn present in the crystal is promoted, and low-temperature sinterability can be enhanced.

  However, if the oxygen concentration in the firing atmosphere exceeds 0.1% by volume, formation of oxygen defects in the crystal structure becomes insufficient, and firing at low temperatures becomes difficult.

  Therefore, in the present embodiment, the oxygen concentration in the firing atmosphere is adjusted to 0.1% by volume or less.

  And by making the oxygen concentration of the firing atmosphere 0.1 volume% or less in this way, CuO is reduced to Cu even when fired at a low temperature of 950 to 1000 ° C. due to the equilibrium oxygen concentration of Cu—CuO. Can be avoided as much as possible, and therefore the desired insulation can be ensured without lowering the specific resistance ρ.

Further, as described above, the oxygen concentration in the firing atmosphere is set to 0.001 to 0.1% by volume , and the CuO content is reduced to the range of 0.5 to 1.75 mol%. Combined with the improvement, the saturation magnetic flux density Bs can be improved, and thereby the DC superimposition characteristics can be improved.

  However, when the oxygen concentration is less than 0.001% by volume, oxygen defects are formed more than necessary, and as a result, the specific resistance ρ of the ferrite porcelain may be lowered. Therefore, the oxygen concentration is preferably 0.001% by volume or more.

In this manner, in the present embodiment, without adding a glass component, in addition to _Fe 2 _O 3, N iO, a mixture of CuO 0.5~1.75mol%, the ZnO in the range of 10～28Mol% ferrite After producing the powder and molding the ferrite powder , a ferrite porcelain having a magnetic flux saturation density of 480 mT or more is fired at a firing temperature of 1000 ° C. or less in an atmosphere having an oxygen concentration of 0.001 to 0.1% by volume. Since it is manufactured, even if it does not contain a glass component in the ferrite composition, it can obtain good sinterability that can be fired at a low temperature of 1000 ° C. or less, and has good insulation and direct current superposition characteristics. A good ferrite porcelain can be obtained.

Specifically, it has good sinterability with a sintered density of 5.10 g / cm ³ or more, good insulation with a specific resistance ρ of 10 ⁷ Ω · cm or more , and high saturation of 480 mT or more. A ferrite porcelain having a magnetic flux density Bs and good DC superposition characteristics can be obtained by low-temperature firing at 1000 ° C. or lower. As a result, a ferrite porcelain in which the decrease in the inductance L is suppressed even when a large current is applied can be obtained at low energy and cost.

Moreover, since the ferrite composition does not contain glass components (PbO, SiO ₂ , B ₂ O _3, etc.), it does not cause abnormal grain growth during firing, and avoids a decrease in magnetic permeability. And good magnetic properties can be secured. In particular, since it does not contain a Pb-based component as a glass component, it does not cause environmental pollution.

Further, by adding a predetermined amount of SnO ₂ to the ferrite powder, the saturation magnetic flux density Bs can be further improved, and a ferrite porcelain with further improved DC superposition characteristics can be obtained.

  FIG. 1 is a cross-sectional view showing an embodiment of a coil component manufactured using the ferrite porcelain.

  The coil component is formed in a disk shape and includes a core member 3 including a shaft core portion 1 and a pair of flange portions 2 a and 2 b connected to both ends of the shaft core portion 1. And the coil | winding 4 is wound around the said axial center part 1, and this coil | winding 4 is further armored by the protective member 5 which has thermosetting resins, such as an epoxy resin, as a main component. In addition, mounting electrodes 6 a and 6 b are formed on one main surface of the core member 3. The core member 3 is formed of the ferrite porcelain.

  As described above, since the core member 3 is formed of the ferrite porcelain of the present invention, the coil component can have good DC superposition characteristics such that the insulation property is good and the DC superposition characteristics can be maintained up to a high magnetic field. Therefore, it is possible to obtain a coil component suitable for high current use that can suppress a decrease in inductance L even when a large direct current is applied.

  The present invention is not limited to the above embodiment. In the above embodiment, the case where the ferrite porcelain of the present invention is used for the core member has been described, but it goes without saying that it can be used for a magnetic layer of a multilayer composite component such as a multilayer inductor or a multilayer LC component.

  Next, examples of the present invention will be specifically described.

[Sample preparation]
Fe ₂ O ₃ , ZnO, NiO, and CuO were prepared as ceramic raw materials, and these ceramic raw materials were weighed so as to have the composition shown in Table 1. Next, these weighed materials were put in a ball mill together with pure water and PSZ balls, mixed and pulverized in a wet manner for 16 hours, evaporated to dryness, and calcined at a temperature of 750 ° C. for 2 hours.

  These calcined materials are wet-ground again in a ball mill for 10 hours, an appropriate amount of polyvinyl alcohol (organic binder) is added, and then a pressure press is used to form a ring-shaped sample having an outer diameter of 20 mm, an inner diameter of 12 mm, and a thickness of 1 mm. Was made. Similarly, a pressure press was used to prepare a disk-shaped sample having a diameter of 10 mm and a thickness of 1 mm.

Then, each sample obtained was fired for 2 hours at a temperature of 950 to 1100 ° C. in an air atmosphere or in a mixed gas atmosphere of N ₂ —O ₂ in which the oxygen concentration was adjusted to 0.1% by volume. 1 to 10 ring-shaped samples and disk-shaped samples were prepared.

(Sample evaluation)
(Sinterability and insulation)
About each ring-shaped sample of sample numbers 1-10, the Archimedes method was used, the sintering density (g / cm < ³ >) was calculated | required, and sinterability was evaluated.

In addition, for each of the disk-shaped samples of sample numbers 1 to 10, silver was applied to both sides and baked to form electrodes, and a DC voltage of 50 V was applied to measure insulation resistance (IR). The specific resistance logρ (Ω · cm) was determined from the dimensions. The sintered density is 5.0 g / cm ³ or more, preferably 5.10 g / cm ³ or more is evaluated as “sinterability”, and the specific resistance logρ is 5.0 or more, preferably 7.0 or more. Was evaluated as “good”.

  Table 1 shows the ferrite composition, the firing temperature, the sintering density and the specific resistance logρ in each firing atmosphere (atmosphere and oxygen concentration 0.1 volume%) of each sample of sample numbers 1 to 10.

a. When firing in an air atmosphere When the content of CuO in the ferrite composition is as low as 0 to 1.75 mol% as in sample numbers 1 to 6, even if firing at each temperature of 950 to 1050 ° C or 1100 ° C, The sintered density was less than 5.0 g / cm ^3, and it was confirmed that the sinterability was poor.

In sample No. 7, the content of CuO in the ferrite composition was increased to 2.5 mol%, so that when sintered at a temperature of 1100 ° C., the sintered density improved to 5.22 g / cm ³ and the specific resistance logρ was 9 However, the firing temperature was high and the desired low-temperature firing could not be performed.

In Sample No. 8, the content of CuO in the ferrite composition was increased to 5.0 mol%, so that when sintered at a temperature of 1050 ° C., the sintered density was improved to 5.20 g / cm ³ and the specific resistance logρ was 9 .3 and good. That is, by setting the content of CuO to 5.0 mol%, it was possible to sinter at a temperature lower than that of Sample No. 7, but the firing temperature was still high and the desired low temperature firing could not be performed.

Sample No. 9 has a high CuO content of 7.0 mol% in the ferrite composition, so that even when fired at a low temperature of 950 ° C., the sintered density becomes 5.05 g / cm ³ and low temperature firing is possible. The specific resistance logρ was also good at 6.4. However, in this case, a desired high saturation magnetic flux density Bs could not be obtained as will be described later.

Sample No. 10 has a CuO content of as high as 9.0 mol% in the ferrite composition, so that, similarly to Sample No. 9, a sintered density of 5.0 g / cm ³ or higher and 5% even when fired at a low temperature of 950 ° C. A specific resistance logρ of 0.0 or more can be secured, but in this case as well as the sample number 9, a desired high saturation magnetic flux density Bs could not be obtained.

FIG. 2 is a graph showing the relationship between the CuO content and the sintered density, where the horizontal axis represents the CuO content (mol%) and the vertical axis represents the sintered density (g / cm ³ ). In the figure, ◇ indicates a firing temperature of 950 ° C., Δ indicates a firing temperature of 1000 ° C., □ indicates a firing temperature of 1050 ° C., and ○ indicates a firing temperature of 1100 ° C.

As apparent from FIG. 2, the sintering density is increased and the sinterability is improved by increasing the firing temperature and increasing the CuO content. In particular, when the CuO content is 7.0 mol% or more, a sintered density of 5.0 g / cm ³ or more can be ensured even when firing at a temperature of 950 to 1000 ° C. However, when firing in an air atmosphere as will be described later, a sufficiently high saturation magnetic flux density Bs that satisfies the desired DC superposition characteristics could not be obtained.

  FIG. 3 is a graph showing the relationship between the CuO content and the specific resistance logρ, where the horizontal axis represents the CuO content (mol%) and the vertical axis represents the specific resistance logρ (Ω · cm). In the figure, ◇ indicates a firing temperature of 950 ° C., Δ indicates a firing temperature of 1000 ° C., □ indicates a firing temperature of 1050 ° C., and ○ indicates a firing temperature of 1100 ° C.

  As is apparent from FIG. 3, when firing in an air atmosphere, the specific resistance logρ tends to increase by raising the firing temperature, and the specific resistance logρ is 5 even when firing at a low temperature of 950 to 1000 ° C. 0.0 or more could be secured. However, when firing in an air atmosphere as will be described later, a high saturation magnetic flux density Bs that satisfies the desired DC superposition characteristics could not be obtained.

b. When firing at an oxygen concentration of 0.1% by volume In any of sample numbers 1 to 10, firing at a temperature range of 950 to 1100 ° C. can ensure a sintered density of 5.00 g / cm ³ or more. And good sinterability could be obtained. This is because the oxygen concentration at the time of firing is as low as 0.1% by volume, oxygen defects are formed in the crystal structure, interdiffusion of Fe, Ni, Cu, Zn present in the crystal is promoted, and sinterability is improved. It seems that we were able to increase it. However, when the content of CuO is less than 0.2 mol% with Shitamawa' a 0.5 mol%, when fired at 950 ° C., sintered density was also found to decrease to less than 5.10 g / cm ^3.

  However, in Sample No. 9, since the content of CuO in the ferrite composition was too large, 7.0 mol%, the specific resistance logρ was reduced to less than 5.0, and the insulation was reduced. This is because the CuO content is large, so that the amount of CuO reduced to Cu is increased, and the specific resistance logρ is therefore decreased.

  In Sample No. 10, since the content of CuO in the ferrite composition was too large, 9.0 mol%, for the same reason as Sample No. 9, the specific resistance logρ was reduced to less than 5.0, and the insulating property was reduced.

  In addition, when the firing temperature was set to 1100 ° C. for sample numbers 1 and 5, the specific resistance logρ decreased to less than 5.0. This is because the CuO content is as low as 0 mol% or 1.0 mol% CuO, but due to the relationship of the equilibrium oxygen concentration of Cu—CuO at 1100 ° C., the firing atmosphere becomes a reducing atmosphere and the reduction of CuO is promoted. This seems to have caused a decrease in the resistance logρ.

  When the firing temperature was set to 1050 ° C. to 1100 ° C. with sample numbers 6 to 8, the specific resistance log ρ decreased to less than 5.0. This is because the CuO content is as low as 1.75 mol% to 5 mol%, but due to the relationship of the equilibrium oxygen concentration of Cu—CuO at 1050 ° C. to 1100 ° C., the firing atmosphere becomes a reducing atmosphere and the reduction of CuO is promoted. Like the above, it seems that the specific resistance logρ was lowered.

In addition, when the sample numbers 7 and 8 were fired at 1000 ° C., the specific resistance logρ was 7.0 or less.

On the other hand, since the sample numbers 4 to 6 have a CuO content of 0.5 to 1.75 mol% and are within the scope of the present invention, the specific resistance log ρ is not limited even when firing at a firing temperature of 950 to 1000 ° C. Both are 7.0 or more, and the sintered density is 5.10 g / cm. ³ The above can be secured, and it has been found that good insulation can be obtained even when firing at a low temperature of 1000 ° C. or lower.

FIG. 4 is a view showing the relationship between the CuO content and the sintered density, and FIG. 5 is an enlarged view of the main part of FIG. The horizontal axis represents the CuO content (mol%), and the vertical axis represents the sintered density (g / cm ³ ). Further, in the figure, ◇ indicates a firing temperature of 950 ° C., □ indicates a firing temperature of 1000 ° C., and Δ indicates a firing temperature of 1050 ° C.

As is clear from FIGS. 4 and 5, it was found that when the oxygen concentration was set to 0.1% by volume, a sintered density of 5.0 g / cm ³ or more could be secured.

  FIG. 6 is a diagram illustrating the relationship between the CuO content and the specific resistance logρ, where the horizontal axis represents the CuO content (mol%) and the vertical axis represents the specific resistance logρ (Ω · cm). In the figure, ◇ indicates a firing temperature of 950 ° C., Δ indicates a firing temperature of 1000 ° C., and □ indicates a firing temperature of 1050 ° C.

  As apparent from FIG. 6, when the firing temperature is raised, CuO is easily reduced to Cu due to the equilibrium oxygen concentration of Cu—CuO, and the specific resistance logρ tends to decrease.

Further, when the CuO content was 1.75 mol% or less and firing was carried out at a temperature of 1000 ° C. or less, the specific resistance logρ was able to obtain a good insulating property of 7.0 or more.

  On the other hand, when the CuO content was 7 mol% or more, the specific resistance log ρ was lowered to 5.0 or less, resulting in a loss of insulation.

(DC superposition characteristics)
About each ring-shaped sample of sample numbers 1-10, saturation magnetic flux density Bs (mT) at the time of baking at the temperature of 1000 degreeC is measured, and increase rate (%) of saturation magnetic flux density Bs is calculated, and direct current | flow The superposition characteristics were evaluated.

  Here, the saturation magnetic flux density Bs is measured by using a vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd., VSM-5-15), measuring saturation magnetization at a magnetic flux density of 1T, and the measured value and sintered density. And calculated from

  The increase rate of the saturation magnetic flux density Bs was calculated using the saturation magnetic flux density Bs when the CuO content was 9 mol% and fired in the air atmosphere (sample number 10) as a reference (100%).

  Table 2 shows the ferrite composition, firing temperature, saturation magnetic flux density Bs in each firing atmosphere (atmosphere and oxygen concentration 0.1% by volume), and increasing rate (%) of the saturation magnetic flux density Bs for each sample Nos. 1 to 10. Show.

As is clear from Table 2, the saturation magnetic flux density Bs was as low as 349 to 462 mT when fired in an air atmosphere. In Sample Nos. 1 to 8, when sintered at a temperature of 1000 ° C., the content of CuO having a low melting point is as low as 5 mol% or less, so that a sintered density of 5.0 g / cm ³ or more can be obtained. This seems to have caused a decrease in sinterability. In Sample Nos. 9 and 10, since the CuO content is too high as 7 mol% or 9 mol% (see Table 1), it seems that the desired high saturation magnetic flux density Bs could not be obtained.

  On the other hand, even when the oxygen concentration is 0.1% by volume, if the CuO content is too high as 7 mol% or 9 mol% as in sample numbers 9 and 10, the saturation magnetic flux density Bs is less than 480 mT. Thus, the desired high saturation magnetic flux density Bs could not be obtained.

  On the other hand, when the oxygen concentration is 0.1 vol% and the CuO content is 5 mol% or less, the saturated magnetic flux density Bs is 480 mT or more as in sample numbers 1 to 8, and the sample fired in the atmosphere. An increase rate of 5% or more with respect to No. 10 could be obtained. In particular, in Sample Nos. 1 to 6 having a CuO content of 0 to 1.75 mol%, the increase rate of the saturation magnetic flux density Bs was improved to 10% or more.

  FIG. 7 is a graph showing the relationship between the CuO content and the saturation magnetic flux density Bs, where the horizontal axis represents the CuO content (mol%) and the vertical axis represents the saturation magnetic flux density Bs (mT). In the figure, a circle indicates a case where firing is performed in an atmosphere having an oxygen concentration of 0.1% by volume, and a circle indicates a case where firing is performed in an air atmosphere.

  As is apparent from FIG. 7, when the CuO content is reduced in the air atmosphere, the sinterability is lowered and the desired high saturation magnetic flux density Bs cannot be obtained. On the other hand, when the CuO content is increased. Although the sinterability is improved, the saturation magnetic flux density Bs cannot be increased.

  On the other hand, when fired at an oxygen concentration of 0.1%, since the sinterability is good, a saturation magnetic flux density Bs of 480 mT or more can be obtained in a region where the CuO content is 5 mol% or less. In particular, when the CuO content is suppressed to 1.75 mol% or less, a satisfactory saturation magnetic flux density Bs of 500 mT or more can be obtained.

  FIG. 8 is a diagram showing the relationship between the CuO content and the increase rate of the saturation magnetic flux density Bs, where the horizontal axis represents the CuO content (mol%) and the vertical axis represents the saturation magnetic flux density Bs (mT). In the figure, a circle indicates a case where firing is performed in an atmosphere having an oxygen concentration of 0.1% by volume, and a circle indicates a case where firing is performed in an air atmosphere.

  As is apparent from FIG. 8, when sintered at 1000 ° C. in an air atmosphere, since the sinterability is inferior in the region where the CuO content is 5 mol% or less, the saturation magnetic flux density Bs tends to decrease as the CuO content decreases. is there.

  On the other hand, when firing at an oxygen concentration of 0.1%, the saturation magnetic flux density Bs is increased compared to Sample No. 10 fired in the air atmosphere. When the CuO content is 5 mol% or less, the saturation magnetic flux density Bs is increased by 5% or more. In particular, when the CuO content is 1.75 mol% or less, the saturation magnetic flux density Bs is 10% or more. It turned out to increase.

(Comprehensive evaluation)
From the above, when firing in an air atmosphere, the content of CuO cannot be increased and sintering cannot be performed without firing at a high temperature of 1050 ° C. or higher. Even if sintering can be performed at a high temperature of 1050 ° C., since the content of CuO is large, a desired high saturation magnetic flux density Bs cannot be obtained, and good DC superposition characteristics cannot be obtained.

On the other hand, when the content of CuO in the ferrite composition is 5.0 mol% or less and the atmosphere is adjusted to an oxygen concentration of 0.1%, a high sinterability with a sintering density of 5.0 g / cm ³ or more is obtained. Even when baked at a temperature of 1000 ° C., a good saturation magnetic flux density Bs with an increase rate of 5% or more is obtained at 480 mT or more while maintaining good insulation with a specific resistance logρ of 5.0 or more. I found out that I could do it.

In particular, in an atmosphere in which the content of CuO in the ferrite composition is 0.5 to 1.75 mol% and the oxygen concentration is set to 0.1%, the sintered density is 5. High saturation sinterability of 10 g / cm ³ or more, good insulation with a specific resistance logρ of 7.0 or more, and a good saturation magnetic flux of 10% or more at 500 mT or more It was found that the density Bs can be obtained.

These ceramic raw materials are weighed so that the contents of Fe ₂ O ₃ , ZnO, NiO, and CuO are as shown in Table 3, and then the outer diameter is the same as in Example 1 in the same manner and procedure. A ring-shaped sample having a diameter of 20 mm, an inner diameter of 12 mm, and a thickness of 1 mm was produced.

And the obtained sample was baked at a temperature of 1000 ° C. for 2 hours in a mixed gas atmosphere of N ₂ —O ₂ in which the oxygen concentration was adjusted to 0.1% by volume, and samples Nos. 11 to 20 were produced. .

  Next, about each sample of sample numbers 11-20, an annealed copper wire is wound for 20 turns, an impedance analyzer (E4991A, manufactured by Agilent Technologies) is used to measure inductance at a frequency of 1 MHz, and magnetic permeability is measured from the measured value. μ was determined.

  Moreover, the magnetic flux saturation density Bs was calculated | required by the method and procedure similar to Example 1 about each sample of the sample numbers 11-20.

  Table 3 shows the ferrite composition, firing temperature, and magnetic permeability μ of each sample Nos. 11-20.

As is apparent from Table 3, the magnetic permeability μ is 100 or more without impairing the magnetic flux saturation density Bs within the range of Fe ₂ O ₃ : 44 to 49.8 mol% and ZnO: 10 to 28 mol%. It was found that an effective value can be secured.

These ceramic raw materials were weighed so as to be Fe ₂ O ₃ : 49.0 mol%, NiO: 26.0 mol%, ZnO: 24.0 mol%, and CuO: 1.0 mol%, and further containing SnO ₂ SnO ₂ was weighed so that the amount was 100 parts by weight of ferrite powder and the parts shown in Table 4.

  Then, a ring-shaped sample having an outer diameter of 20 mm, an inner diameter of 12 mm, and a thickness of 1 mm was produced by the same method and procedure as in Example 1.

The obtained sample was baked for 2 hours at a temperature of 1000 ° C. in a mixed gas atmosphere of N ₂ —O ₂ with an oxygen concentration adjusted to 0.1% by volume, thereby preparing samples Nos. 31 to 35.

  Next, the initial value L0 of the inductance was measured for each of the samples Nos. 31 to 35 by the same method and procedure as in Example 3, and the magnetic permeability μ was obtained from the initial value L0. Next, in accordance with JIS standard C2560-2, a direct current was superimposed on these samples so that the magnetic field was 500 A / m, and the inductance L was measured. The inductance change rate was obtained based on the inductance L and the initial value L0 of the inductance, and the DC superposition characteristics were evaluated.

Table 4 shows the ferrite composition, the content of SnO ₂ , the firing temperature, the magnetic permeability μ, and the inductance change rate of each sample of sample numbers 31 to 35.

As is clear from the comparison between sample number 31 and sample numbers 32-35, it was found that by adding SnO ₂ , the inductance change rate was reduced and the DC superposition characteristics were improved. It was also found that as the amount of SnO ₂ added increases, the rate of change in inductance also decreases and the DC superposition characteristics improve. That is, it was confirmed that the addition of SnO ₂ contributes to the improvement of the DC superposition characteristics, and that the DC superposition characteristics improve as the addition amount increases.

  Even when fired at a low temperature of 1000 ° C. or lower, it is possible to realize a ferrite porcelain and a coil component suitable for a large current application having good sinterability and insulation and good DC superposition characteristics.

1 Axle core 2a, 2b collar 3 core member 4 winding

Claims (3)

A method for producing a ferrite porcelain containing at least Fe ₂ O ₃ and NiO,
Without adding a glass component, in addition to the Fe ₂ O ₃ and the NiO, a ferrite powder is prepared by mixing CuO in a range of 0.5 to 1.75 mol% and ZnO in a range of 10 to 28 mol%. After being molded, firing was performed at a firing temperature of 1000 ° C. or less in an atmosphere having an oxygen concentration of 0.001 to 0.1% by volume, a saturation magnetic flux density of 480 mT or more , and a specific resistance of 1.0 × 10 ^7. A method for producing a ferrite porcelain, characterized by producing a ferrite porcelain of Ω · cm or more . The method for producing a ferrite porcelain according to claim 1 , wherein SnO ₂ is added in an amount of 1.3 parts by weight or less with respect to 100 parts by weight of the ferrite powder. _3. The method for manufacturing a ferrite porcelain according to claim 1, wherein the content of Fe ₂ O ₃ is 44 to 49.8 mol%.

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