CN100334035C - Ferrite material and method of manufacturing the same - Google Patents

Abstract

The present invention provides a production method of a ferrite material comprising as main constituents Fe<SUB>2</SUB>O<SUB>3</SUB>: 62 to 68 mol %, ZnO: 12 to 20 mol %, and MnO substantially constituting the balance, wherein the method comprises a compacting step for obtaining a compacted body by using a powder containing the main constituents, the powder having a specific surface area falling within a range between 2.5 and 5.0 m<SUP>2</SUP>/g and a 90% particle size of 10 mum or less, and a sintering step for sintering the compacted body obtained in the compacting step. Accordingly, the saturation magnetic flux density of the Mn-Zn based ferrite can be improved.

Description

Method for manufacturing ferrite material and Ferrite Material

Technical field

The present invention relates to Mn-Zn based ferrite and manufacture method thereof, particularly be the low-loss of seeking the Mn-Zn based ferrite and the technology that improves near the saturation magnetic flux density of the humidity province 100 ℃.

Background technology

In recent years, electronics just develops towards direction small-sized, high-output power, and various thereupon parts develop towards the direction of high integration, high speed processing, thereby requires the big electric currentization of the supply lead of supply capability.

In addition, even also require at high temperature also to keep the supply lead of pre-determined characteristics, this is because supply lead often is exposed in the heating environment that comes from parts (for example CPU) etc.Even and supply lead also must keep predetermined performance under the such environment for use temperature conditions of higher of automobile electrical electronic circuit.

Therefore, can at high temperature use for the employed transformer of supply lead and choke also requirement with big electric current.

Material as these transformers and choke use has soft magnetic metallic material and Ferrite Material.Ferrite Material can be divided into Mn-Zn based ferrite and Ni based ferrite.

Compare with Ferrite Material, because the saturation magnetic flux density of soft magnetic metallic material is higher, even thereby also can not cause magneticsaturation by bigger electric current.But, soft magnetic metallic material exist usually loss height, price expensive, than problems such as great, rust-preventing characteristic differences.

On the other hand, Ferrite Material have the ratio of performance to price good, in the loss lower advantage of tens of kHz to hundreds of kHz frequency bands.And the Mn-Zn based ferrite is also higher than the saturation magnetic flux density of Ni based ferrite, therefore, big electric current with transformer and reactance coil (below sometimes the two is referred to as transformer etc.) in, generally use the Mn-Zn based ferrite.But in recent years, in the higher temperature district, when specifically using near 100 ℃, also requirement can show the Ferrite Material of high saturation magnetic flux density.As top narrate, although the Mn-Zn based ferrite shows the saturation magnetic flux density higher than Ni based ferrite, near the high-temperature zone 100 ℃ (the following high-temperature zone that only is called), its saturation magnetic flux density is inadequate.

So, being the saturation magnetic flux density of the Ferrite Material that improves the high-temperature zone, the present inventor has carried out various researchs.Wherein, for example patent documentation 1 (spy opens the 2000-159523 communique) is open: by adopting by containing nearly ferric oxide, the content of 60～75mol% is that zinc oxide and the surplus of 0～20mol% (but not containing 0) is forming that manganese oxide constituted, and can obtain 450mT at 100 ℃ and (measure magnetic field: 1000A/m) or above saturation magnetic flux density.Patent documentation 1 is pointed out: (measure magnetic field: 1000A/m) or above saturation magnetic flux density, remove the composition, also need special stipulation calcining and firing condition in order to obtain 450mT at 100 ℃.

Patent documentation 1 disclosed technology be effectively for this technical task of raising of the desired saturation magnetic flux density of Mn-Zn based ferrite, but saturation magnetic flux density also requires to be further enhanced.Here, by means of the method that can keep good this ferrite characteristic of the ratio of performance to price, it is self-evident that hope can improve saturation magnetic flux density.

In addition, Ferrite Material is not only required to have high saturation magnetic flux density, also require to have this characteristic of low-loss.Therefore, the low-loss with regard to the Mn-Zn based ferrite had once proposed various schemes.For example, patent documentation 2 (special public clear 63-59241) is by adding NiO, Li in MnO and ZnO ₂Among O and the MgO at least a kind is to seek to realize the low-loss under 150 ℃ or the above condition.

But although patent documentation 2 disclosed ferrite cores seek to be implemented in the low-loss of 150 ℃ or above humidity province, saturation magnetic flux density is not at the row of consideration.In addition, bottom temp (bottom temperature) be 150 ℃ or more than, thereby, will cause the degeneration of loss and initial magnetic permeability in the humidity province (60～130 ℃) that general transformer etc. uses.

Summary of the invention

The present invention is based on such technical task and finishes, and its purpose is: method for manufacturing ferrite material that a kind of saturation magnetic flux density that adopts easy method just can make the Mn-Zn based ferrite is improved etc. is provided.In addition, problem to be solved provides a kind of humidity province, saturation magnetic flux density height and low Ferrite Material of loss in uses such as general transformers.

The present inventor studies for solving above-mentioned problem, found that: by the Ferrite Material that is shaped and sintering specific surface area and then 90% particle diameter obtain at the powder of specified range, its saturation magnetic flux density is improved.Promptly the invention provides a kind of method for manufacturing ferrite material, the principal constituent of this Ferrite Material is Fe ₂O ₃: 62～68mol%, ZnO:12～20mol% and surplus are essentially MnO, it is characterized in that, this method comprises: the specific surface area that adopts the principal constituent that is contained is at 2.5～5.0m ²In the scope of/g and 90% particle diameter be that 10 μ m or following powder obtain the forming process of molding, and the firing process that burns till the molding that obtains in forming process.

Method for manufacturing ferrite material of the present invention, preferred 50% particle diameter at 0.8～1.8 μ m, 10% particle diameter in the scope of 0.55～0.73 μ m.

Method for manufacturing ferrite material of the present invention further preferably is set in 2.7～5.0m with specific surface area ²In the scope of/g, and 90% particle diameter is set at 5 μ m or following.

Above method is improved the electromagnetic property of Mn-Zn based ferrite by the control powder characteristics.The present invention has also proposed by the intensification condition of control firing process and/or the method that the cooling condition is improved the electromagnetic property of Mn-Zn based ferrite.

Promptly as the method for the intensification condition of controlling firing process, the invention provides a kind of method for manufacturing ferrite material, the principal constituent of this Ferrite Material is Fe ₂O ₃: 62～68mol%, ZnO:12～20mol% and surplus are essentially MnO, and this method comprises: adopt the forming process that contains the powder of principal constituent and obtain molding, and the firing process that burns till the molding that obtains in forming process; Wherein said firing process comprises: 4.0% or following oxygen partial pressure scope in be warming up to the temperature-rise period of preset temperature, maintenance process that keeps at preset temperature and the temperature-fall period after the maintenance process.

In the present invention, preferably will be set at 200 ℃/h or following at the average heating speed of 900 ℃ of temperature-rise period or above humidity province.

In addition, in the present invention, preferably the stable region of keeping preset temperature is set at 900 ℃ of temperature-rise period or above humidity province.

Moreover the method as the cooling condition of controlling firing process the invention provides a kind of method for manufacturing ferrite material, and the principal constituent of this Ferrite Material is Fe ₂O ₃: 62～68mol%, ZnO:12～20mol% and surplus are essentially MnO, it is characterized in that, this method comprises: adopt the forming process that contains the powder of principal constituent and obtain molding, and the firing process that burns till the molding that obtains in forming process; Wherein said firing process is included in maintenance process that the preset temperature district keeps and at the temperature-fall period that carries out after the maintenance process under nitrogen atmosphere, and at temperature-fall period speed of cooling to be set be 100 ℃/h or following slow cooling district.

In the present invention, this slow cooling district preferably is contained in 1000～900 ℃ the scope.

In addition, method for manufacturing ferrite material of the present invention can also contain NiO:5mol% or following (but not containing 0) and/or LiO except above-mentioned principal constituent _0.5: not enough 4mol% (but not containing 0).

According to the above method for manufacturing ferrite material of the present invention that is described in detail, the saturation magnetic flux density that can access 100 ℃ be 470mT or above (measure magnetic field: 1194A/m) and core loss be 1400kW/m ³Or the Ferrite Material of following (condition determination: 100kHz, 200mT).And the present invention's regulation:, be called the minimum value of core loss in the occasion of simple core loss.

In addition, according to method for manufacturing ferrite material of the present invention, the volume specific resistance that can access under the room temperature is 0.13 Ω m or above Ferrite Material.

Moreover, in the present invention, preferably at firing process configuration baffle to cover the direct impact of the air-flow that produces in the firing atmosphere to molding.

More particularly, when a plurality of moldinies burn till, preferably dispose baffle under stacked state to be surrounded as body mode on every side.

This baffle can the sintered body of same composition constitutes by having in fact with conceivable Ferrite Material.In addition, the firing process that baffle is set also goes for the Ferrite Material beyond the composition of the present invention's regulation.

But in recent years, except that requiring the Mn-Zn based ferrite to have high saturation magnetic flux density and the low-loss, also requirement is also less with the degeneration of the core loss of the use association of above-mentioned high-temperature zone, promptly requires to have reliability.Patent documentation 3 (spy opens the 2002-255559 communique) discloses a method of guaranteeing the reliability of core loss.Patent documentation 3 is Fe in principal constituent ₂O ₃: 55.0～59.0mol%, ZnO:0～15.0mol%, NiO:2.0～10.0mol% and surplus are essentially in the Mn-Ni-Zn based ferrite of MnO, with low oxygen partial pressure as firing atmosphere.And then propose: in the temperature-fall period after preset temperature keeps, at preset temperature or the following nitrogen atmosphere that converts to, its speed of cooling is comparable fast before simultaneously.

But, although the scheme of patent documentation 3 is effectively to the reliability of guaranteeing core loss, to as if iron oxide content be low to moderate the material of 55.0～59.0mol%, thereby the saturation magnetic flux density of high-temperature zone is inadequate.

Based on such purpose, the present inventor is for solving above-mentioned problem, surpasses the research that the Mn-Zn based ferrite of the rich Fe of 60mol% carries out with regard to the ferric oxide amount, and the result has obtained following opinion:

(i) for obtaining high saturation magnetic flux density, the Mn-Zn based ferrite of rich Fe is favourable, but then, because generate cation defect easily, so degeneration that can over sight (OS) core loss reliability.

(ii) in order to suppress the generation of cation defect, can the atmosphere when burning till be controlled to be low oxygen partial pressure (for example the oxygen partial pressure less than 1%).Based on burning till of low oxygen partial pressure, although the inhibition that cation defect is generated, in other words the reliability of core loss guaranteed it is that effectively core loss itself will be degenerated.

Based on above background, the Mn-Zn based ferrite of the rich Fe that the present inventor burns till with regard to low oxygen partial pressure has been studied the relation of core loss and eddy-current loss and volume specific resistance.Its result confirms that core loss and eddy-current loss show the Mn-Zn based ferrite of the rich Fe of high value, and its volume specific resistance shows lower value.This can be understood as this volume specific resistance and is subjected to existing about form institute of the CaO that contains as minor component in the Mn-Zn based ferrite etc.An amount of segregation of minor components such as CaO that is to say, if in the crystal boundary of Mn-Zn based ferrite, then can access predetermined volume specific resistance.

The present inventor infers that the Mn-Zn based ferrite of the rich Fe that low oxygen partial pressure burns till is owing to minor components such as CaO exist in the intragranular volume, thereby volume specific resistance is lower, so the present inventor attempts to obtain making the method for the minor components such as CaO of intragranular existence in an amount of segregation of crystal boundary.

At this, minor components such as CaO are present in intragranular in the high-temperature zone of firing process, but are unsettled in the form that intragranular exists, thus in the temperature-fall period after keeping preset temperature in crystal boundary generation segregation.But, can do such understanding: when in the atmosphere that is in low oxygen partial pressure, the minor component of CaO etc. is stranded in intragranular easily, so be suppressed to the segregation of crystal boundary, volume specific resistance reduces.So, for the minor component that makes CaO etc. to an amount of segregation of crystal boundary, perhaps make its minor component that contains CaO etc., the speed of cooling of the temperature-fall period of the firing process that perhaps slows down more than ever beforely.The volume specific resistance of having confirmed the Mn-Zn based ferrite of the rich Fe that obtains like this is improved.

Promptly the invention provides a kind of saturation magnetic flux density height and become the high novel ferrite material of volume specific resistance of core loss index.This Ferrite Material is Fe by principal constituent ₂O ₃: the sintered compact that 62～68mol%, ZnO:12～20mol% and surplus are essentially MnO constitutes, 100 ℃ saturation magnetic flux density be 470mT or above (measure magnetic field: 1194A/m), the volume specific resistance under the room temperature be 0.13 Ω m or more than.

In Ferrite Material of the present invention, as the 1st minor component, at Si and Ca respectively to be converted into SiO ₂And CaCO ₃Count SiO ₂/ CaCO ₃Under=0.055～0.30 the condition, it is effective containing 900～3000ppm.

In addition, in Ferrite Material of the present invention, as the 1st minor component, at Si and Ca respectively to be converted into SiO ₂And CaCO ₃Count SiO ₂/ CaCO ₃Under=0.055～0.19 the condition, it is effective containing 1700～3000ppm.

Based on opinion of the present invention, under the situation of the 1st minor component that contains predetermined amount like this, can access the low and high Ferrite Material of reliability core loss of saturation magnetic flux density height, core loss of high-temperature zone.By making it contain SiO in the scope of recommending in the present invention ₂And CaCO ₃, SiO then ₂And CaCO ₃Can produce segregation at crystal boundary in right amount.Perhaps, also can make SiO as the 1st minor component by in the above-mentioned temperature-fall period that burns till, the slow cooling district being set ₂And CaCO ₃Produce segregation at crystal boundary in right amount.

Ferrite Material of the present invention is except above-mentioned principal constituent (Fe ₂O ₃, ZnO, MnO) in addition, can also contain NiO:5mol% or following (but not containing 0%) and/or LiO _0.5: not enough 4mol% (but not containing O).

And Ferrite Material of the present invention can obtain such characteristic, and promptly core loss is 1400kW/m ³Or the velocity of variation of following (condition determination: 100kHz, 200mT) and core loss is 10% or following (the velocity of variation of core loss=(Pcv1-Pcv2)/Pcv1 * 100; Pcv1 wherein: the core loss before the high-temperature storage; Pcv2: the core loss behind the high-temperature storage; High-temperature storage: be to keep 2000 hours down) at 150 ℃.

In addition, in Ferrite Material of the present invention, the δ value (cation defect amount) in the preferred following ferrite composition formula (1) be 0.0033 or below.

(Zn _a ²⁺，Ni _b ²⁺，Mn _c ²⁺，Mn _d ³⁺，Fe _e ²⁺，Fe _f ³⁺)O _4+δ (1)

Wherein, a+b+c+d+e+f=3, δ=a+b+c+ (3/2) d+e+ (3/2) f-4

Moreover, the invention provides a kind of LiO _0.5Contain quantity not sufficient 4mol% (but not containing 0), 100 ℃ saturation magnetic flux density and be 490mT or above (measure magnetic field: 1194A/m) and core loss be 1300kW/m ³Or the Ferrite Material of following (condition determination: 100kHz, 200mT).

In the Ferrite Material of the invention described above,, preferably contain from Nb as the 2nd minor component ₂O ₅: 400ppm or following (but not containing 0), ZrO ₂: 1000ppm or following (but not containing 0), Ta ₂O ₅: 1000ppm or following (but not containing 0), In ₂O ₅: 1000ppm or following (but not containing 0) and Ga ₂O ₅: 1000ppm or at least a kind of selecting among following (but not containing 0).

Furtherly, in Ferrite Material of the present invention,, can contain from SnO as the 3rd minor component ₂: 10000ppm or following (but not containing 0) and TiO ₂: 10000ppm or at least a kind of selecting among following (but not containing 0).

In addition, in Ferrite Material of the present invention,, preferably contain: be scaled 35ppm or following (but not containing 0), MoO by P from P-compound as the 4th minor component ₃: 1000ppm or following (but not containing 0), V ₂O ₅: 1000ppm or following (but not containing 0), GeO ₂: 1000ppm or following (but not containing 0), Bi ₂O ₃: 1000ppm or following (but not containing 0), Sb ₂O ₃: 3000ppm or at least a kind of selecting among following (but not containing 0).For Ferrite Material, in order to obtain high saturation magnetic flux density, it is effective making the Fe amount increase in the principal constituent.On the other hand, along with the increase of Fe amount, sintering becomes and is difficult to carry out.Therefore, under the situation of selecting rich Fe to form, sintering temperature is raise.But when improving sintering temperature, the Zn composition will evaporate, and causes core loss to increase.Moreover making the firing temperature rising will cause energy usage increases, uses the cost rising of stove material etc., and this may become the unfavorable factor of industrial aspect.In order to get rid of such unfavorable factor, to obtain the saturation magnetic flux density height and the low Ferrite Material of loss of high-temperature zone simultaneously, it is effective containing the 4th minor component.

Description of drawings

The pattern of burning till that Fig. 1 (a) expression heats up continuously with the constant heat-up rate, Fig. 1 (b) expression setting is kept the pattern of burning till of the stable region (Ia) of preset temperature with the scheduled time, and Fig. 1 (c) expression is provided with the pattern of burning till of a plurality of stable regions (Ia, Ib).

Fig. 2 (a) be expression with a plurality of be the synoptic diagram of molding state stacked together by burned material, Fig. 2 (b) expression is set to the state of the baffle of air flow barrier thing, the state of baffle is disposed in Fig. 2 (c) expression in the mode around the body of being surrounded as.

Fig. 3 represents to make the oxygen partial pressure (PO of firing atmosphere ₂) when changing, measure volume specific resistance, the minimum value of core loss, the minimum value of eddy-current loss, the velocity of variation of core loss and the resulting result of variation of δ value (cation defect amount) under the room temperature.

Fig. 4 (a) is an instance graph of representing to be provided with continuously the slow cooling district, and Fig. 4 (b) is an instance graph of representing intermittently to be provided with slow cooling district (IIIb), the slow cooling district (IIIb) that Fig. 4 (c) expression is provided with the form that keeps the scheduled time at preset temperature.

Fig. 5 is the interior chart of 1000～900 ℃ temperature range of representing preferably slow cooling district (IIIb) to be arranged on temperature-fall period (III).

Fig. 6 is the chart of the composition of test portion No.1～17 that obtain of expression the 1st embodiment etc.

Fig. 7 is the chart of the specific surface area of test portion No.18～25 that obtain of expression the 2nd embodiment etc.

Fig. 8 is the chart of the composition of test portion No.26～32 that obtain of expression the 3rd embodiment etc.

Fig. 9 is the chart of the relation of expression oxygen partial pressure of temperature-rise period and saturation magnetic flux density.

Figure 10 is the chart of the firing condition of test portion No.37～43 that obtain of expression the 5th embodiment etc.

Figure 11 represents an example of the pattern of burning till of test portion shown in Figure 10.

Figure 12 is the chart of the composition of test portion No.45～51 that obtain of expression the 6th embodiment etc.

Figure 13 is the chart of the temperature-rise period atmosphere of test portion No.52～54 that obtain of expression the 7th embodiment etc.

Figure 14 is the chart of the minor component of test portion No.55-1～65 that obtain of expression the 8th embodiment etc.

Figure 15 is the chart of expression saturation magnetic flux density that test portion No.66～79 that the slow cooling district makes are set etc.

Figure 16 is the chart of the saturation magnetic flux density of expression when making it contain the 2nd minor component and the 4th minor component etc.

Embodiment

Below describe with regard to embodiment of the present invention.

At first, just the composition of the Mn-Zn based ferrite that the present invention was suitable for describes.

The Mn-Zn based ferrite that the present invention was suitable for contains Fe as principal constituent ₂O ₃: 62～68mol%, ZnO:12～20mol% and surplus are essentially MnO.

Work as Fe ₂O ₃Content when increasing, the saturation magnetic flux density of high-temperature zone rises, on the other hand, core loss has the tendency of degeneration.At Fe ₂O ₃When being less than 62mol%, the saturation magnetic flux density of high-temperature zone reduces.On the other hand, at Fe ₂O ₃When surpassing 68mol%, the increase of core loss is remarkable.Therefore, the present invention is with Fe ₂O ₃Be set at 62～68mol%.Along with Fe ₂O ₃The increase of content, bottom temp (core loss shows minimum temperature) moves to high temperature side, but works as Fe ₂O ₃Content in the scope of 62～68mol% the time, bottom temp can be set in 60～130 ℃ the scope.Preferred Fe ₂O ₃Content be 63～67mol%, further preferred Fe ₂O ₃Content be 63～66mol%.

The content of ZnO also influences saturation magnetic flux density and core loss.When ZnO was less than 12mol%, saturation magnetic flux density reduced, and loss simultaneously increases.In addition, when ZnO surpassed 20mol%, saturation magnetic flux density reduced, and loss simultaneously increases.Therefore, the present invention is set at 12～20mol% with ZnO.Along with the increase of ZnO content, bottom temp moves to high temperature side, when in the scope of ZnO content at 12～20mol%, bottom temp can be set in 60～130 ℃ the scope.The content of preferred ZnO is 13～19mol%, and the content of further preferred ZnO is 14～18mol%.

Ferrite Material of the present invention except that above-mentioned, also contains MnO in fact as surplus as principal constituent, and then preferably contains NiO and/or LiO _0.5As.

NiO is effective making along with the rising of Curie temperature aspect the saturation magnetic flux density raising.In order to give full play to its effect, the present invention preferably contain 0.2mol% or more than.But when the content of NiO surpassed 5mol%, loss increased.Therefore, the present invention is in the scope of 5mol% or following (but not containing 0) content of NiO for the performance saturation magnetic flux density improves and this effect of low-loss.The content of preferred NiO is 0.2～5mol%, and the content of further preferred NiO is 0.5～4mol%, and further the content of preferred NiO is 0.5～3mol%.

LiO _0.5Be effective aspect the saturation magnetic flux density that improves the high-temperature zone.But content reaches 4mol% or when above, loss increases, simultaneously 100 ℃ saturation magnetic flux density be reduced to add before equal or following level.Therefore, the present invention is with LiO _0.5Content be set at not enough 4mol%.Preferred LiO _0.5Content is 0.2～3.5mol%, further preferred LiO _0.5Content is 0.5～3mol%.In addition, the Li oxide compound is with LiO ₂Expression is calculated composition in order to convert with Li, and the present invention is expressed as LiO with the Li oxide compound _0.5

NiO and LiO _0.5The total amount be preferably set to 0.2～5mol%, preferred NiO and LiO _0.5The total amount be 0.5～4mol%, further preferred NiO and LiO _0.5The total amount be 1～3mol%.

Secondly, the qualification reason with regard to minor component describes.

Ferrite Material of the present invention can contain Si and Ca (is converted into SiO as the 1st minor component ₂, CaCO ₃, below only be expressed as SiO sometimes ₂, CaCO ₃).SiO ₂And CaCO ₃Segregation forms resistive formation in crystal boundary, helps to reduce the wastage, and has the effect that improves sintered density as sintering aid simultaneously.

At this, Ferrite Material of the present invention comprises two kinds of situations, promptly the slow cooling district is set and the slow cooling district is not set at the temperature-fall period that burns till.Under the situation that the slow cooling district is not set,, add up to the SiO that contains 1700～3000ppm as the 1st minor component ₂And CaCO ₃, and SiO ₂/ CaCO ₃Be preferably set to 0.055 or more than.In addition, under the situation that the slow cooling district is set, use the still less SiO of content ₂And CaCO ₃Just enough.Specifically, preferably at SiO ₂/ CaCO ₃Under=0.055～0.30 the condition, contain 900～3000ppm.

As the prerequisite of above condition, SiO ₂And CaCO ₃Can contain SiO respectively ₂: 300ppm or following (but not containing 0) and CaCO ₃: 2700ppm or following (but not containing 0).At SiO ₂Surpass 300ppm or CaCO ₃When surpassing 2700ppm, because of the grow up degeneration of the loss that causes of discontinuous abnormal grain will increase.Therefore the present invention should set SiO ₂: 300ppm or following, CaCO ₃: 2700ppm or following.Preferred SiO ₂And CaCO ₃Content be SiO ₂: 100～250ppm, CaCO ₃: 1300～2500ppm, preferred SiO ₂And CaCO ₃Content be SiO ₂: 150～200ppm, CaCO ₃: 1500～2500ppm.

By with SiO ₂/ CaCO ₃Be set at suitable value, and/or by the slow cooling district being set at the temperature-fall period that burns till, then 100 ℃ saturation magnetic flux density can be set at 470mT or above (measure magnetic field: 1194A/m) and with the volume specific resistance under the room temperature be set at 0.13 Ω m or more than.

The Si and the Ca that contain predetermined amount help low-loss and have the effect that improves sintered density as sintering aid, help the raising of the saturation magnetic flux density of high-temperature zone simultaneously.

The present invention can contain from Nb as the 2nd minor component ₂O ₅: 400ppm or following (but not containing 0), ZrO ₂: 1000ppm or following (but not containing 0), Ta ₂O ₅: 1000ppm or following (but not containing 0), In ₂O ₅: 1000ppm or following (but not containing 0), Ga ₂O ₅: 1000ppm or at least a kind of selecting among following (but not containing 0).By means of containing these the 2nd minor components, can obtain the effect that improves saturation magnetic flux density and/or reduce the wastage.

The present invention can contain from SnO as the 3rd minor component ₂: 10000ppm or following (but not containing 0) and TiO ₂: 10000ppm or at least a kind of selecting among following (but not containing 0).SnO ₂And TiO ₂Be present in intragranular and crystal boundary, have the effect that reduces the wastage.When surpassing 10000ppm, cause because of discontinuous abnormal grain the grow up degeneration of the loss that causes and the reduction of saturation magnetic flux density.Therefore, the present invention is with SnO ₂And TiO ₂Higher limit be set at 10000ppm respectively.On the other hand, in order fully to obtain above effect, preferably make the 3rd minor component contain 500ppm or more than.Further preferred SnO ₂And TiO ₂Content be 1000～8000ppm, preferred SnO ₂And TiO ₂Content be 1000～7000ppm.And make it compound when containing the 3rd minor component, the total of content is preferably set to 10000ppm or following.

The present invention can contain from P-compound as the 4th minor component: be scaled 35ppm or following (but not containing 0), MoO by P ₃: 1000ppm or following (but not containing 0), V ₂O ₅: 1000ppm or following (but not containing 0), GeO ₂: 1000ppm or following (but not containing 0), Bi ₂O ₃: 1000ppm or following (but not containing 0), Sb ₂O ₃: 3000ppm or at least a kind of selecting among following (but not containing 0).The 4th minor component has the effect that improves sintered density as sintering aid, helps easy fired simultaneously.In order to bring into play its effect, MoO fully ₃, V ₂O ₅, GeO ₂, Bi ₂O ₃, and Sb ₂O ₃The compound that preferably contains 50ppm or above, P by P convert preferably contain 5ppm or more than.And make it compound when containing the 4th minor component, the total of content is preferably set to 2500ppm or following.

Ferrite Material of the present invention can be set at 100 ℃ saturation magnetic flux density 470mT or above (mensuration magnetic field: 1194A/m), and then can be set at 480mT or above (mensuration magnetic field: 1194A/m) by the above-mentioned composition of suitable selection.In addition, can make core loss show that the bottom temp of minimum value is in 60～130 ℃ the scope, the minimum value with core loss is set at 1300kW/m simultaneously ³Or following (condition determination: 100kHz, 200mT).Particularly by selecting preferred the composition, the minimum value that obtains core loss is 1200kW/m ³Or the saturation magnetic flux density of following (condition determination: 100kHz, 200mT) and 100 ℃ is 500mT or above (measure magnetic field: 1194A/m) this characteristic that in the past can not obtain also is possible.About bottom temp, preferably can be set in 70～120 ℃, further preferably can be set in 80～120 ℃ the scope.Therefore, use the ferrite part of Ferrite Material of the present invention, its bottom temp is present in its practical use temperature district.And Ferrite Material of the present invention has initial magnetic permeability under the room temperature to be 600 and then to be 700 or above such high value.

Describe with regard to method for manufacturing ferrite material of the present invention below.

As the raw material of principal constituent, use oxide compound or by being heated as the powder of compound.Specifically, can use Fe ₂O ₃Powder, Mn ₃O ₄Powder, ZnO powder and then can use NiO powder and Li ₂CO ₃Powder etc.The median size of each raw material powder can suit to be chosen in the scope of 0.1～3.0 μ m.

The raw material powder of wet mixing principal constituent is calcined later on.The incinerating temperature can be the preset temperature in 800～1000 ℃ of scopes, and atmosphere can be N ₂Or atmosphere.Incinerating can suit to select in 0.5～5.0 hour scope steady time.

After the calcining, calcined powder is pulverized.Pulverizing and making specific surface area is 2.5～5.0m ²/ g, 90% particle diameter are 10 μ m or following.

Why specific surface area is set at 2.5～5.0m ²/ g is because at not enough 2.5m ²During/g, sufficient sintered density can not be obtained, higher saturation magnetic flux density can not be obtained.In addition, surpass 5.0m in specific surface area ²During/g, after in most cases confirming sintering, there is abnormal grain to grow up and core loss (Pcv) and initial magnetic permeability (μ i) degeneration.Preferred specific surface area is 2.7～5.0m ²/ g.

Why 90% particle diameter being set at 10 μ m or following, is owing to when surpassing 10 μ m, can not be burnt till density fully.Preferred 90% particle diameter is 5 μ m or following.And then in the present invention, in order to improve saturation magnetic flux density, except 90% particle diameter, also preferably make 50% particle diameter at 0.8～1.8 μ m, 10% particle diameter in the scope of 0.73～0.55 μ m.In addition, 90% particle diameter of the present invention etc. are benchmark and definite with the number, and 90% particle diameter is meant that the accumulation number is 90% particle diameter, and 50% particle diameter is meant that the accumulation number is 50% particle diameter, and 10% particle diameter is meant that the accumulation number is 10% particle diameter.

Above calcining powder is pulverized, and just obtaining specific surface area is 2.5～5.0m ²/ g, 90% particle diameter are 10 μ m or following powder, but the invention is not restricted to this.Also can not do special control and pulverize the calcining powder, by means of the methods such as pulverized powder that screening obtains, also can obtain specific surface area is 2.5～5.0m ²/ g, 90% particle diameter are 10 μ m or following powder.

In addition, the invention is not restricted to the raw material of above-mentioned principal constituent, also can will contain the powder of composite oxides of 2 kinds or above metal as the raw material of principal constituent.For example, the aqueous solution that contains iron(ic) chloride, Manganous chloride tetrahydrate by oxidizing roasting just can obtain containing the powder of the composite oxides of Fe and Mn.This powder is mixed with ZnO powder, and resulting mixed powder also can be used as the principal constituent raw material.In this case, do not need calcining, as long as the specific surface area of the mixed powder of the powder of composite oxides and ZnO powder is 2.5～5.0m ²/ g, 90% particle diameter are 10 μ m or following getting final product.

Equally, as the raw material of minor component, also can use oxide compound or by being heated as the compound powder of oxide compound.Specifically, can use SiO ₂, CaCO ₃, Nb ₂O ₅, ZrO ₂, Ta ₂O ₅, In ₂O ₅, Ga ₂O ₅, SnO ₂, TiO ₂, MoO ₃, V ₂O ₅, GeO ₂, Bi ₂O ₃, Sb ₂O ₃Deng.And when selecting P-compound, can use the powder (Ca for example that obtains P-compound by heating as the 4th minor component ₃(PO ₄) ₂) etc.The raw material powder of these minor components and the powder mixes of calcining the pulverized principal constituent in back.But, also can supply with calcination process with principal constituent with after the raw material powder of principal constituent mixes.

By principal constituent and the powder formed of the minor component that adds as required,, subsequently sintering circuit is a granulated into particle for being carried out smoothly.Granulation for example can use spray-dryer to carry out.A small amount of for example polyvinyl alcohol (PVA) of suitable matrix material that adds is sprayed it and drying with spray-dryer in mixed powder.The particle grain size that obtains is preferably set to about 80～200 μ m.

The particle that obtains for example uses the pressing machine of the metal pattern that has predetermined shape to be shaped to desired shape, and this molding is supplied to firing process then.

Burn till in 1250～1450 ℃ temperature range and keep about 2～10 hours.In order to give full play to the effect of Ferrite Material of the present invention, preferably in 1300～1400 ℃ scope, burn till.

As above theory detailed description, the composition that adopts the present invention to recommend, and with the condition enactment of each operation is above-mentioned condition, then 100 ℃ saturation magnetic flux density can be set at 470mT or abovely (measure magnetic field: 1194A/m), and then be set at 480mT or abovely (measure magnetic field: 1194A/m) and the minimum value of core loss can be set at 1400kW/m ³Or following (condition determination: 100kHz, 200mT), and then be set at 1300kW/m ³Or following (condition determination: 100kHz, 200mT).Particularly by selecting preferred the composition, the minimum value that obtains core loss is 1200kW/m ³Or following (condition determination: 100kHz, 200mT), simultaneously 100 ℃ saturation magnetic flux density is 500mT or above (measure magnetic field: the characteristic that the past 1194A/m) can not obtain also is possible.And according to the present invention, its Ferrite Material has initial magnetic permeability under the room temperature to be 600 and then to be 700 or above such high value.

More than in preferred form of the present invention, the method that the condition of operation before burning till is controlled mainly has been described.Below main narration method that the condition of firing process is controlled.

Shown in Fig. 1 (a), firing process comprises the temperature-rise period (I) that is warmed up to preset temperature, then temperature-rise period (I) keeps the maintenance process (II) of the scheduled time and the temperature-fall period (III) that carries out afterwards in maintenance process (II) at preset temperature.Particularly will constitute the condition that the condition enactment of the temperature-rise period (I) of firing process and/or temperature-fall period (III) is recommended for the present invention, this is effective for improving saturation magnetic flux density.

＜temperature-rise period (I) 〉

It is 4.0% or following zone that the present invention is provided with oxygen partial pressure at temperature-rise period (I).This zone can be the whole zone of temperature-rise period (I), also can be the part of temperature-rise period (I).Under the situation of a part that is temperature-rise period (I), this zone preferably sets in 500 ℃ or above temperature range.This is to surpass at 4.0% o'clock because of the oxygen partial pressure at temperature-rise period (I), can not fully improve in burning till back density, can not obtain higher saturation magnetic flux density.Preferred oxygen partial pressure be 3.0% or below, further preferred oxygen partial pressure be 2.5% or below.

In addition, the present invention is set at 200 ℃/h or following with the average heating speed of temperature-rise period (I).Because if average heating speed surpasses 200 ℃/h, then can not obtain high saturation magnetic flux density.Preferred average heating speed is 150 ℃/h or following, and further preferred average heating speed is 100 ℃/h or following.And can begin average heating speed is set at 200 ℃/h or following from the initial stage of heating up, but, obtain the effect of high saturation magnetic flux density, be set at 200 ℃/h or followingly just can obtain significantly by average heating speed with 900 ℃ or above humidity province.Therefore, for fear of long-timeization of firing process, preferably the average heating speed with 900 ℃ or above humidity province is set at 200 ℃ or following.

At this, temperature-rise period (I) is not limited to shown in the image pattern 1 (a) such with certain heat-up rate situation of elevated temperature continuously, shown in also can image pattern 1 (b) like that, the stable region (Ia) of keeping preset temperature with the scheduled time is set.As shown in the embodiment described later,, stable region (Ia) just can seek the further raising of saturation magnetic flux density by being set.In addition, the stable region shown in Fig. 1 (c) like that, a plurality of (Ia, Ib) are set also is effective.

＜maintenance process (II) 〉

Then temperature-rise period (I) carries out the transition to maintenance process (II).At this, patent specification will keep the maintenance temperature of process (II) to be called firing temperature.

Firing temperature can suit to select in 1250～1450 ℃ scope, as mentioned above, in order to give full play to the effect of Ferrite Material of the present invention, burns till preferably and carries out in 1300～1400 ℃ scope.In addition, the present invention will this moment atmosphere (firing atmosphere) in oxygen partial pressure be set at 2.0% or following, be preferably 1.0% or following, more preferably 0.5% or below.The hold-time of maintenance process (II) can suit to select in 2～10 hours scope.

＜temperature-fall period (III) 〉

Maintenance process (II) carries out the transition to temperature-fall period (III) after finishing.Shown in Fig. 1 (a)～(c), temperature-fall period (III) both can make temperature reduce with certain cooling rate continuously, also can the same stable region that is provided with temperature-rise period (I).

In firing furnace, with a plurality of be that molding is configured with state stacked together by burned material.Fig. 2 (a) has schematically represented this state.Research by the present inventor is learnt: as shown in Fig. 2 (a), when being laminated into body G and burning till, for example molding that obtains by the molding G that is positioned at epimere and the molding that obtains by the molding G that is positioned at the stage casing, its initial magnetic permeability and core loss there are differences, and characteristic also has deviation.

, on one side to burn till be on one side to import predetermined gas in the firing furnace to carry out.For example, on one side import the control above-mentioned oxygen partial pressure in the firing furnace nitrogen implement firing process on one side.At this moment, the air-flow that is caused by the nitrogen that is used to form firing atmosphere (representing with arrow among Fig. 2 (a)) generates in firing furnace.The present inventor infers: the evaporation of temperature deviation in the firing furnace that causes owing to the generation of this air-flow and the Zn that causes because of air-flow etc. is the reason that the characteristic after burning till produces deviation.So, the baffle P of the obstacle that becomes air-flow shown in Fig. 2 (b) is set, so that make the not direct impact forging body G of air-flow, the result can reduce the deviation of characteristic.

Shown in Fig. 2 (b), baffle P is a benchmark with molding G, can be arranged on the upstream side of air-flow at least, but most preferably shown in the image pattern 2 (c) like that, be configured in the mode that is surrounded as body G.But, must avoid forming the stopping property of molding is surrounded by baffle P, because like this, burn till and be difficult to carry out.In addition, baffle P preferably uses and burns till the resulting Ferrite Material of molding G and has the sintered body of same composition.This is for to the unlikely generation detrimentally affect of firing atmosphere.

As above narrate, the condition of major control temperature-rise period (I), can access demonstrate 93% or above, more preferably 95% or the Ferrite Material of above relative density.

In addition, the average crystal grain diameter of ferrite cemented body is preferably in the scope of 5～30 μ m.This is that magnetic hysteresis loss increases because when crystal grain diameter hour, and on the other hand, when crystal grain diameter was big, eddy-current loss increased.Preferred median size is 8～25 μ m, and preferred median size is 10～20 μ m.

At this, volume specific resistance (the following volume specific resistance that only claims under the room temperature when changing the oxygen partial pressure (PO2) of firing atmosphere, sometimes be designated as ρ), minimum value (the following core loss that only claims of the core loss of 100kHz, 200mT, sometimes be designated as Pcv), the minimum value (the following eddy-current loss that only claims is designated as Pev sometimes) of eddy-current loss, the velocity of variation (the following Pcv velocity of variation that is designated as sometimes) of core loss and the variation of δ value (cation defect amount).Its result as shown in Figure 3.Measure test portion composed as follows of usefulness, firing temperature is set at 1350 ℃.In addition, the concrete manufacture method of test portion is followed embodiment described later.

Principal constituent: Fe ₂O ₃: 64.0mol%, MnO:17.5mol%, ZnO:16.5mol%, NiO:2.0mol%

Minor component: SiO ₂: 100ppm, CaCO ₃: 1500ppm, Nb ₂O ₅: 200ppm

As can be seen from Figure 3: at the oxygen partial pressure (PO of firing atmosphere ₂) when reducing, the velocity of variation of core loss (Pcv velocity of variation) reduces, otherwise the value of core loss (Pcv) and eddy-current loss (Pev) increases, and core loss itself will be degenerated.And as can be seen: the Pcv velocity of variation is relevant with the δ value, and the δ value is 0.0034 o'clock, and the Pcv velocity of variation is about 15%, therefore for the Pcv velocity of variation is set at 10% or below, the δ value should be limited to 0.0033 or below.

The present invention has proposed to be provided with at temperature-fall period (III) scheme in slow cooling district for the degeneration of the core loss that suppresses to be caused by burning till under the low oxygen partial pressure.So, describe with regard to the slow cooling district with reference to Fig. 4 (a)～(c) below.

In Fig. 4 (a), the temperature-fall period (III) of maintenance process (II) that continue is made of IIIa, IIIb and IIIc.Wherein IIIb partly is the slow cooling district.This slow cooling district IIIb compares with other district IIIa and IIIc, and speed of cooling is slower.Specifically, the speed of cooling of this slow cooling district IIIb is set at 100 ℃/h or following, is preferably 50 ℃/h or following, more preferably 30 ℃/h or following.

This slow cooling district IIIb is not limited to being provided with like that continuously shown in Fig. 4 (a), also can carry out alternate setting as Fig. 4 (b).And then slow cooling of the present invention district IIIb is in the conceptive occasion that is not limited to lower the temperature, also comprise shown in Fig. 4 (c) like that, keep the form of the scheduled time at preset temperature.As previously mentioned, the purpose that this slow cooling district IIIb is set is: make solid solution in the segregation in crystal boundary of minor components such as intragranular CaO, because this purpose can be understood as: even keep the form of the scheduled time also can reach at preset temperature.

The present invention does not limit the temperature range that slow cooling district IIIb is set, but as described later, and it is bigger to carry out the effect that slow cooling produced 1000～900 ℃ temperature ranges.Therefore, slow cooling district IIIb preferably is arranged in 1000～900 ℃ the temperature range of temperature-fall period III.The experimental result that becomes its basis as shown in Figure 5.

Measure and use the composition of test portion same as described above, firing temperature is 1350 ℃, the oxygen partial pressure when burning till is set at 0.02%.As can be seen from Figure 5: be under 1000～900 ℃ the situation in the temperature of slow cooling district IIIb, the highest and core loss (Pcv) of volume specific resistance (p) and eddy-current loss (Pev) reduce to minimum.Carry out slow cooling by humidity province, compare with the situation that slow cooling district IIIb is not set at 1000～900 ℃, core loss can drop to 1/2 or below.

In addition, more than explanation expression is to be that the maintenance process (II) of carrying out under the low oxygen partial pressure carries out the example of temperature-fall period (III) afterwards immediately, but also can begin to be provided with the process that makes its cooling from firing temperature under low oxygen partial pressure between maintenance process (II) and temperature-fall period (III).

The oxygen partial pressure of the firing atmosphere of above temperature-fall period (III) is set at less than 1%, be preferably set to 0.2% or below, further be preferably set to 0.05% or below.It is in order to suppress cation defect that firing atmosphere is set at such low oxygen partial pressure, and this defective is tended to take place in the rich Fe that becomes object of the present invention forms.

(embodiment)

Enumerate specific embodiment below and further describe the present invention.

＜the 1 embodiment 〉

At first, use the 1st embodiment that the qualification reason of principal constituent is described.

As the raw material of principal constituent, prepare Fe ₂O ₃Powder, MnO powder, ZnO powder, NiO powder and Li ₂CO ₃Powder carries out weighing and makes it become composition shown in Figure 6.Carry out wet mixing after the weighing, 850 ℃ of calcinings 3 hours.

Secondly, the calcined material of principal constituent raw material is mixed mutually with the raw material of minor component, the raw material of minor component uses SiO ₂Powder: 200ppm, CaCO ₃Powder: 1500ppm and Nb ₂O ₅Powder: 200ppm.In the calcined material of principal constituent raw material, add the raw material of minor component, mix while pulverize.

Pulverizing proceeds to the median size that makes calcined material and is about till the 1.5 μ m.In the mixture that obtains, add tackiness agent,, obtain the molding of annular shape through the granulating postforming.

The molding that obtains (maintenance process 5 hours, is kept process oxygen partial pressure (PO under 1350 ℃ temperature in controlled oxygen partial pressure ₂): 0.02%, 1%) burn till, obtain ferrite core thus.In addition, in firing process (oxygen partial pressure: in the temperature-fall period 0.02%), in the speed refrigerative slow cooling district of 1000～900 ℃ humidity provinces settings with 30 ℃/h.Use this ferrite core, measured 100 ℃ of (mensuration magnetic fields: the velocity of variation of saturation magnetic flux density 1194A/m) (the following Bs that is designated as sometimes), core loss (condition determination: 100kHz, 200mT), volume specific resistance and core loss.Its result is shown in Fig. 6 in the lump.Wherein the following formula of the velocity of variation utilization of core loss is tried to achieve.

The velocity of variation of core loss=(Pcv1-Pcv2)/Pcv1 * 100

Pcv1: the core loss before the high-temperature storage; Pcv2: the core loss behind the high-temperature storage; High-temperature storage: be to keep 2000 hours down at 150 ℃

Fe among the test portion No.1,2,3,4 and 5 ₂O ₃Content increases successively.Wherein, at Fe ₂O ₃Content is that 60.0mol% is lower than under the situation of scope of the present invention, and at Fe ₂O ₃Content is that 70.0mol% exceeds under the situation of scope of the present invention, and saturation magnetic flux density is low and core loss is big.

Secondly, test portion No.6,7,8 and 9 ZnO content increase successively.Wherein, be that 10.0mol% is lower than under the situation of scope of the present invention at ZnO content, and be that 21.0mol% exceeds under the situation of scope of the present invention that saturation magnetic flux density is low and core loss is big at ZnO content.

From above result as can be known: in order to ensure high saturation magnetic flux density and low core loss, importantly with Fe ₂O ₃Be set in the scope of 62～68mol%, ZnO be set in the scope of 12～20mol%.

Test portion No.10,11,12 and 13 NiO content increase successively.As can be seen from Figure 6: owing to contain NiO, its core loss and saturation magnetic flux density change.

Consider the following fact: because of containing NiO saturation magnetic flux density is improved, and in containing the example of 6.0mol%, its core loss surpasses 1400kW/m ³, the necessary content of setting NiO.NiO preferably sets in the scope of 0.5～4.0mol%.

Test portion No.14,15,16 and 17 LiO _0.5Content increases successively.As can be seen from Figure 6:: owing to contain LiO _0.5, its core loss and saturation magnetic flux density change.

Consider the following fact: because of containing LiO _0.5And saturation magnetic flux density is improved, and in containing the example of 4.0mol%, its core loss surpasses 1400kW/m ³, must set LiO _0.5Content.LiO _0.5Preferred settings is in the scope that is not less than 0.2mol% and not enough 4.0mol%.

＜the 2 embodiment 〉

For the experiment that the relation of confirming specific surface area and saturation magnetic flux density is carried out is represented with the 2nd embodiment.

As the raw material of principal constituent, prepare Fe ₂O ₃Powder: 65.6mol%, MnO powder: 18.9mol%, ZnO powder: 14.0mol% and NiO powder: 1.5mol% carry out calcining 3 hours at 850 ℃ after the wet mixing.

Secondly, the calcining powder is pulverized, just obtained the various specific surface areas (SSA) shown in Figure 7 and the pulverized powder of 90% particle diameter (90%Ps).In this pulverized powder, add tackiness agent,, obtain the molding of annular shape through the granulating postforming.

The molding that obtains is warming up to 1350 ℃, then oxygen partial pressure is controlled to be 0.8%, just made ferrite core by keeping 5 hours burn till.The ferrite core that obtains is measured 100 ℃ (measured magnetic field: saturation magnetic flux density 1194A/m) (Bs), the density after burning till, the core loss (Pcv) and the initial magnetic permeability (μ i) of 80 ℃ (bottom temps).Its result as shown in Figure 7.

As shown in Figure 7, as the not enough 2.5m of specific surface area (SSA) of pulverized powder ²During/g (test portion No.18), the density after burning till is low, thereby saturation magnetic flux density (Bs) rests on 500mT or following.But, when the specific surface area (SSA) of pulverized powder surpasses 5.0m ²During/g (test portion No.25), core loss (Pcv) surpasses 1400kW/m ³Therefore, the present invention's specific surface area (SSA) that will obtain the powder of molding is set in 2.5～5.0m ²In the scope of/g.As can be seen from Figure 7: in order to obtain high saturation magnetic flux density (Bs), the specific surface area that preferably will obtain the powder of molding is set in 2.7～5.0m ²In the scope of/g.

It can also be seen that in addition: the specific surface area of pulverized powder (SSA) is 2.5m ²/ g or test portion (test portion No.19) above, that 90% particle diameter (90%Ps) surpasses 10 μ m are 2.5m with specific surface area (SSA) ²/ g or test portion (test portion No.20～24) above, 90% particle diameter (90%Ps) less than, 10 μ m are compared, and (Bs) is higher for the latter's saturation magnetic flux density.Therefore, the present invention is set at 10 μ m or following with 90% particle diameter, is preferably set to 5 μ m or following.Also know in addition: obtain the Ferrite Material of high saturation magnetic flux density (Bs) and low core loss (Pcv), 10% particle diameter (10%Ps) of powder is in 0.55～0.73 the scope, and 50% particle diameter (50%Ps) is in the scope of 0.8～1.8 μ m.

＜the 3 embodiment 〉

The oxygen partial pressure of burning till when 1350 ℃ keep is set at 1.0%, similarly makes shown in Figure 8 with the 2nd embodiment in addition based on ferrite core of the present invention.This ferrite core is measured 100 ℃ (measured magnetic field: saturation magnetic flux density 1194A/m) (Bs), the density after burning till, the core loss (Pcv) and the initial magnetic permeability (μ i) of 100 ℃ (bottom temps).Its result as shown in Figure 8.By adopting the composition in the pre-determined range of the present invention and using with specific surface area (SSA) and 90% particle diameter (90%Ps) setting powder within the scope of the present invention, resulting ferrite core can have 480mT and then 500mT or above saturation magnetic flux density (Bs), and core loss (Pcv) is at 1200kW/m ³Or below, and then at 1000kW/m ³Or below.

＜the 4 embodiment 〉

For the relation of the oxygen partial pressure of the temperature-rise period confirming to burn till and saturation magnetic flux density and the experiment of carrying out represent with the 4th embodiment.

As the raw material of principal constituent, prepare Fe ₂O ₃Powder: 65.6mol%, MnO powder: 18.9mol%, ZnO powder: 14.0mol% and NiO powder: 1.5mol% calcined 3 hours at 850 ℃ after wet mixing.

Secondly, calcined body is pulverized, just obtained specific surface area (SSA) and be 3.1m ²/ g, 90% particle diameter are the pulverized powder of 3.2 μ m.This is pulverized powder add tackiness agent,, obtain the molding of annular shape through the granulating postforming.

The molding that obtains burnt till just made ferrite core, wherein burning till is to carry out under following processing condition: be warmed up to 900 ℃ and then be warmed up to 1350 ℃ with the speed of 150 ℃/h ℃ with the speed of 300 ℃/h, kept then 5 hours.In addition, the oxygen partial pressure in 900～1350 ℃ of temperature ranges is set at 0%, 1.0%, 3.0% and 5.0%, the oxygen partial pressure of 1350 ℃ of maintenances is set at 1.0%, make 4 kinds of ferrite cores.And the oxygen partial pressure of the oxygen partial pressure of the temperature-rise period that burns till and maintenance process, set by the nitrogen that in firing furnace, feeds the control above-mentioned oxygen partial pressure.Measure 100 ℃ for this ferrite core and (measured magnetic field: saturation magnetic flux density 1194A/m) (Bs), and measured the density of ferrite core.Its result as shown in Figure 9.Fig. 9 shows the measurement result of the initial magnetic permeability (μ i) of the core loss (Pcv), bottom temp (B.Temp.) of bottom temp and 25 ℃ in the lump.

As can be seen from Figure 9: along with the reduction of oxygen partial pressure, its saturation magnetic flux density (Bs) raises.This can be interpreted as the reduction along with oxygen partial pressure, and density increases, and this is the major cause that saturation magnetic flux density (Bs) raises.

According to above result, the present invention recommend the oxygen partial pressure with 900 ℃ of firing process or above temperature-rise period be set at 4.0% or below.Preferred oxygen partial pressure be 2.5% or below, further preferred oxygen partial pressure be 1.0% or below.

＜the 5 embodiment 〉

The experiment of carrying out for the relation of confirming firing condition and saturation magnetic flux density etc. is represented with the 5th embodiment.

The same molding that obtains annular shape with the 4th embodiment.

The molding that obtains is suitable for intensification condition shown in Figure 10 burns till, made 7 kinds of ferrite cores.And burn till be in stove per unit volume to burn till treatment capacity (number of molding) more and to carry out under 3 sections states that are laminated into body than the 4th embodiment.In addition, the Mn-Zn based ferrite discharges oxygen in the temperature-rise period that burns till, thus per unit volume burn till treatment capacity when increasing, there is the tendency that reduces in magnetic properties.This ferrite core 100 ℃ of (mensuration magnetic fields: saturation magnetic flux density 1194A/m) (Bs) have been measured.And measured the density of ferrite core.Its result is shown among Figure 10 in the lump.In addition, this measurement result is not have setting to be formed the result who measures under the state that surrounds by sintered compact piece described later.

The heat-up rate of Figure 10 is meant 900～1350 ℃ heat-up rate.But except up to 900 ℃ heat-up rate being the test portion No.41 of 300 ℃/h and up to 900 ℃ heat-up rate is the test portion No.42 of 100 ℃/h, other test portion also adopts the described heat-up rate of Figure 10 up to 900 ℃ heat-up rate.In addition, the stable region of Figure 10 is meant in 900～1350 ℃ temperature-rise period and keeps the scheduled time in preset temperature.For example, under the situation of test portion No.41, be warming up to 900 ℃, be warming up to 1200 ℃ from 900 ℃ with the speed of 300 ℃/h with the speed of 75 ℃/h, speed with 75 ℃/h after following 1200 ℃ of maintenances 0.5 hour, through 0.5 hour is warming up to 1350 ℃, kept 5 hours at 1350 ℃, burning till with such pattern of test portion No.41 carried out.

The pattern of burning till of test portion shown in Figure 10 one for example shown in Figure 11.In addition, the oxygen partial pressure of the temperature-rise period that burns till is 0%, and keeping the oxygen partial pressure of process is 1.0%, and this sets by the nitrogen that feeds the control above-mentioned oxygen partial pressure in firing furnace.

As shown in figure 10, No.37 compares with test portion, because the saturation magnetic flux density (Bs) of test portion No.38 and then test portion No.39 is higher, so be favourable to obtaining high saturation magnetic flux density (Bs) when heat-up rate is slow as can be known.In addition, at temperature-rise period the effect that the stable region has further raising saturation magnetic flux density (Bs) is set as can be known by test portion No.40～42.At this, as shown in figure 11, because test portion No.41 similarly heats up with the speed of 300 ℃/h with test portion No.37 until 900 ℃, thus lower as can be known heat-up rate specifically 200 ℃/h or following heat-up rate can adopt in 900 ℃ or above temperature range.Moreover, as test portion No.43,, can further improve saturation magnetic flux density (Bs) by 2 sections stable regions are set.

For test portion No.37, No.39, No.41 and No.43, burn till with 2 kinds of patterns.As the 1st kind of pattern, as shown in Fig. 2 (c), burning till is to be surrounded as under the body G state on every side at the sintered compact piece that adopts and present embodiment is formed equally to carry out.As the 2nd pattern, burn till under the state that is surrounded as without the sintered compact piece around the body G and carry out.For the ferrite core that the 1st pattern and the 2nd pattern obtain, initial magnetic permeability (μ i) and core loss (Pcv) have been measured.Obtain the initial magnetic permeability (μ i) of the ferrite core in epimere and stage casing and the deviation (velocity of variation) of core loss (Pcv) at 3 sections stacked ferrite magnetics in the heart.Its result as shown in figure 10.

As can be seen from Figure 10: surround under the situation about burning till being provided with, compare with the situation of surrounding and burning till is not set, the deviation of the core loss (Pcv) under initial magnetic permeability (μ i) and the bottom temp diminishes.

＜the 6 embodiment 〉

Equally with the 4th embodiment make ferrite core shown in Figure 12, measure 100 ℃ saturation magnetic flux density (Bs), core loss (Pcv), bottom temp (B.Temp.) and the initial magnetic permeability (μ i) of bottom temp.Its result as shown in figure 12, various as can be known compositions can be suitable for the present invention.In addition, the oxygen partial pressure of 900～1350 ℃ temperature range is set at 0% in the temperature-rise period.

＜the 7 embodiment 〉

For the relation of the atmosphere of confirming temperature-rise period and saturation magnetic flux density and the experiment of carrying out represent with the 7th embodiment.

The atmosphere of temperature-rise period as shown in figure 13, the same with the 4th embodiment in addition ferrite core of making is measured 100 ℃ saturation magnetic flux density (Bs), core loss (Pcv), bottom temp (B.Temp.) and the initial magnetic permeability (μ i) of bottom temp.Its result as shown in figure 13.As can be seen from Figure 13: from cold zone more oxygen partial pressure being set at 0% is effectively, is set at low oxygen partial pressure since 500 ℃ or above temperature, can obtain effect of the present invention thus.

＜the 8 embodiment 〉

In order to confirm by control minor component SiO ₂And CaCO ₃Total amount and the characteristic variations of the Ferrite Material that causes of ratio, the experiment of being carried out is represented with the 8th embodiment.

As the raw material of principal constituent, prepare Fe ₂O ₃Powder: 64.0mol%, MnO powder: 17.5mol%, ZnO powder: 16.5mol% and NiO powder: 2.0mol% carry out calcining 3 hours in 850 ℃ after the wet mixing.

Secondly, the calcined material of principal constituent raw material is mixed mutually with the raw material of minor component.The raw material of minor component uses SiO ₂Powder, CaCO ₃Powder and Nb ₂O ₅Powder.In the calcined material of principal constituent raw material, add the raw material of minor component, mix while pulverize.The median size that pulverizing proceeds to calcined material is about till the 1.5 μ m.In the mixture that obtains, add tackiness agent,, just obtain the molding of annular shape in the granulating postforming.

And principal constituent and Nb ₂O ₅The proportioning of powder is as follows:

Fe ₂O ₃：64.0mol％、MnO：17.5mol％

ZnO：16.5mol％、NiO：2.0mol％

Nb ₂O ₅：200ppm

In addition, in minor component, with SiO ₂Powder and CaCO ₃The proportioning of powder is by such many variations of having done shown in Figure 14.

The molding that obtains (maintenance process 5 hours, is kept process oxygen partial pressure (PO in 1350 ℃ in controlled oxygen partial pressure ₂): 0.02%, 1%) burn till, just obtain ferrite core thus.

In addition, use this ferrite core, the same with the 1st embodiment, measure 100 ℃ of (mensuration magnetic fields: the velocity of variation of saturation magnetic flux density 1194A/m) (the following Bs that is designated as sometimes), core loss (condition determination: 100kHz, 200mT), volume specific resistance and core loss.Its result is shown in Figure 14 in the lump.

The present application is such as described above, and its purpose is: with the high saturation magnetic flux density is prerequisite, and the higher Ferrite Material of reliability of a kind of low core loss and core loss is provided.In Figure 14, any test portion of test portion No.55-1～65 all has 450mT or above or 470mT or above and then 500mT or above high saturation magnetic flux density.But about the velocity of variation of core loss and core loss, it is limited that then the two all has the example of good characteristic.For example, test portion No.55-1 (keeping the oxygen partial pressure of process is 0.02%) compares with No.55-2 (keeping the oxygen partial pressure of process is 1.0%), and the velocity of variation that the former demonstrates core loss is 2.7 low value, and core loss surpasses 3500kW/m ³In contrast, the latter to demonstrate core loss be 1500kW/m ³Or following value, and the velocity of variation of core loss is very poor, is 15.4%.This tendency is like this too for test portion No.56-1 and 56-2 etc.Above difference results from the oxygen partial pressure of maintenance process when burning till as aforesaid.

On the other hand, test portion No.58-1 or test portion No.61～63,65, not only core loss is low, and the velocity of variation of core loss is also low.These materials and other material compared, minor component SiO ₂With CaCO ₃Total amount and ratio (SiO thereof ₂/ CaCO ₃, in chart, be expressed as Si/Ca) and difference, i.e. low the and low material of velocity of variation core loss of core loss, its SiO ₂With CaCO ₃Many or its ratio height of total amount.For example, contrast test portion No.55-1 and No.62, its SiO ₂With CaCO ₃Total amount only differ 100ppm, but SiO ₂With CaCO ₃Ratio, test portion No.55-1 is 0.050, and No.62 is higher 0.100.In addition, contrast test portion No.57-1 and No.58-1 are about SiO ₂With CaCO ₃Ratio, test portion No.57-1 is higher; But SiO ₂With CaCO ₃Total amount, then No.58-1 is up to 2650ppm.

Above result disclosed with the high saturation magnetic flux density be prerequisite in the Ferrite Material of the rich Fe that low oxygen partial pressure burns till, as guaranteeing the key element of low core loss, be to control minor component SiO with the stability of core loss ₂With CaCO ₃Total amount and/or its ratio.Specifically, SiO ₂With CaCO ₃Ratio be preferably and surpass 0.055, and SiO ₂With CaCO ₃Total amount be preferably 1700ppm or more than.In this scope, at SiO ₂With CaCO ₃Lower situation under, preferably strengthen SiO ₂With CaCO ₃Total amount, at SiO ₂With CaCO ₃The ratio condition with higher under, can reduce SiO ₂With CaCO ₃Total amount.

As above narrate, by control minor component SiO ₂With CaCO ₃Total amount and ratio thereof, can guarantee the stability of low core loss and core loss.As shown in the 9th embodiment, by the slow cooling district is set in the temperature-fall period of firing process, it is more obvious that this effect will become.

＜the 9 embodiment 〉

In the temperature-fall period of firing process, the effect in order to confirm the slow cooling district is set and the experiment carried out are represented with the 9th embodiment.

Figure 15 represents the characteristics such as saturation magnetic flux density of the 9th embodiment gained material, and wherein this material and material shown in Figure 14 have same composition, and adopts same manufacture method and make.But different with material shown in Figure 14 is that being manufactured in the temperature-fall period of material shown in Figure 15 is provided with the speed of 30 ℃/h in 1000～900 ℃ humidity province and carries out refrigerative slow cooling district.And the speed of cooling beyond in the slow cooling district is 300 ℃/h.For for referencial use, in " correspondence " hurdle of Figure 15, put down in writing the test portion sequence number No. of the same material of forming among Figure 14.

The test portion No.57-1 and 60 of Figure 14 shows 1500kW/m ³Or above 2000kW/m ³Core loss, but by the slow cooling district is set, its core loss becomes 1500kW/m ³Or below.About its volume specific resistance, also be 0.1 Ω m or following, but by the slow cooling district is set, its value surpass 0.2 Ω m or 0.4 Ω m.

As discussed above, by control minor component SiO ₂With CaCO ₃Total amount and ratio thereof, be effectively for the stability of low core loss and core loss, and this effect is provided with the slow cooling district by the temperature-fall period at firing process and becomes more obvious.By the slow cooling district is set at temperature-fall period, even SiO ₂With CaCO ₃Total amount be about 900ppm, still can guarantee the stability of low core loss and core loss.

When confirming to obtain the reason of such effect, found that minor component SiO ₂With CaCO ₃Total amount and the bigger material of ratio thereof, at crystal boundary SiO is arranged ₂With CaCO ₃Segregation, by the slow cooling district is set, it is more obvious that the degree of this segregation becomes simultaneously.In contrast, minor component SiO ₂With CaCO ₃Total amount and ratio materials with smaller thereof, can not confirm to have SiO at crystal boundary ₂With CaCO ₃Segregation.

＜the 10 embodiment 〉

Effect in order to confirm to make it contain the 2nd minor component and the 4th minor component and the experiment carried out are represented with the 10th embodiment.

The same with the 1st embodiment, make ferrite core with composition shown in Figure 16.And as minor component, except SiO ₂, CaCO ₃And Nb ₂O ₅In addition, Fig. 16 described minor components have also been added respectively.As for P, interpolation be calcium phosphate.In Figure 16, with regard to P, expression is converted into the addition of P.In addition, in firing process (oxygen partial pressure: in the temperature-fall period 0.02%), carry out refrigerative slow cooling district with the speed of 30 ℃/h in 1000～900 ℃ humidity provinces setting.Use this ferrite core and the embodiment 1 the same characteristics such as saturation magnetic flux density of having measured.Its result is shown in Figure 16 in the lump.

As can be seen from Figure 16: contain the 2nd minor component or the 4th minor component by making it, saturation magnetic flux density (Bs) surpasses 500mT, and these minor components are effective to improving saturation magnetic flux density.And be provided with under the situation in slow cooling district at the temperature-fall period of firing process, this effect also can obtain.

According to the present invention, can improve the saturation magnetic flux density of Mn-Zn based ferrite in the high-temperature zone, therefore can adapt to various parts develop desired supply lead to high integration and high speed processing aspect big electric currentization.

And, can provide a kind of high Ferrite Material of saturation magnetic flux density height, core loss reliability low and core loss of high-temperature zone according to the present invention.

Claims (15)

1. method for manufacturing ferrite material, the principal constituent of this Ferrite Material is Fe ₂O ₃: 62～68mol%, ZnO:12～20mol% and surplus are essentially MnO, it is characterized in that, this method comprises: adopt and to contain described principal constituent and specific surface area at 2.5～5.0m ²The scope of/g is interior, 90% particle diameter is that 10 μ m or following powder obtain the forming process of molding, and the firing process that burns till the described molding that obtains in described forming process.

2. method for manufacturing ferrite material according to claim 1 is characterized in that: 50% particle diameter of described powder is in the scope of 0.8～1.8 μ m, and 10% particle diameter is in the scope of 0.55～0.73 μ m.

3. method for manufacturing ferrite material according to claim 1 is characterized in that: the specific surface area of described powder is at 2.7～5.0m ²In the scope of/g and 90% particle diameter be 5 μ m or following.

4. method for manufacturing ferrite material according to claim 1, it is characterized in that: described firing process comprises: 4.0% or following oxygen partial pressure scope in be warming up to the temperature-rise period of preset temperature, maintenance process that keeps at described preset temperature and the temperature-fall period after the described maintenance process.

5. method for manufacturing ferrite material according to claim 1, it is characterized in that: described firing process is included in maintenance process that the preset temperature district keeps and the temperature-fall period that carries out under nitrogen atmosphere after described maintenance process, and at described temperature-fall period speed of cooling to be set be 100 ℃/h or following slow cooling district.

6. method for manufacturing ferrite material according to claim 4 is characterized in that: the average heating speed 900 ℃ of described temperature-rise period or above humidity province is 200 ℃/h or following.

7. according to claim 4 or 6 described method for manufacturing ferrite material, it is characterized in that: the stable region of keeping preset temperature is set at 900 ℃ of described temperature-rise period or above humidity province.

8. method for manufacturing ferrite material according to claim 5 is characterized in that: described slow cooling district is included in 1000～900 ℃ the scope.

9. according to claim 1, each described method for manufacturing ferrite material of 4 and 5, it is characterized in that: described Ferrite Material contains NiO: greater than 0mol% but be no more than 5mol% and/or LiO _0.5: greater than 0mol% but not enough 4mol%.

10. according to claim 1, each described method for manufacturing ferrite material of 4 and 5, it is characterized in that: 100 ℃ the saturation magnetic flux density that described Ferrite Material records in the mensuration magnetic field of 1194A/m be 470mT or more than, and the core loss that records under the condition of 100kHz, 200mT is 1400kW/m ³Or below.

11., it is characterized in that according to claim 1, each described method for manufacturing ferrite material of 4 and 5: described Ferrite Material volume specific resistance at room temperature be 0.13 Ω m or more than.

12. according to claim 1, each described method for manufacturing ferrite material of 4 and 5, it is characterized in that: in described firing process, the configuration baffle is to cover the direct impact to described molding of the air-flow that produces in the firing atmosphere.

13. method for manufacturing ferrite material according to claim 12 is characterized in that: a plurality of described moldinies burn till under stacked state, and dispose described baffle to surround described molding mode on every side.

14. method for manufacturing ferrite material according to claim 12 is characterized in that: the sintered body of same composition is constituted described baffle by having in fact with conceivable Ferrite Material.

15. method for manufacturing ferrite material according to claim 13 is characterized in that: the sintered body of same composition is constituted described baffle by having in fact with conceivable Ferrite Material.

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