WO2001004917A1

WO2001004917A1 - Ferrite magnet and method for preparation thereof

Info

Publication number: WO2001004917A1
Application number: PCT/JP2000/004553
Authority: WO
Inventors: Hitoshi Taguchi; Yoshiaki Nakagawa; Kiyoyuki Masuzawa
Original assignee: Tdk Corporation
Priority date: 1999-07-07
Filing date: 2000-07-07
Publication date: 2001-01-18
Also published as: MXPA01002383A; KR20010085763A

Abstract

A ferrite magnet which contains A, R, Fe, M and Si as metal elements and has hexagonal ferrite as the main phase thereof; wherein A represents at least one element selected from among Sr, Ba, Ca and Pb, R represents at least one element selected from among rare earth elements (containing Y) and Bi, and M represents at least one element selected from among Co, Mn, Al, Cr, Ni and Zn; wherein when the metal elements are converted to metal oxides having stoichiometric compositions and contents of respective oxides are calculated, the magnet has a SiO2 content of 1.3 to 2.0 mole %; and wherein the magnet has an atomic ratio of {A + R (Fe + M)/12}/Si of 1.1 to 1.9. The ferrite magnet can be used for suppressing the fluctuation of magnetic properties cased by the fluctuation of firing conditions in the preparation of a ferrite magnet having high residual magnetic flux density and high coercive force.

Description

CT / JP00 / 04553

Description Ferrite magnet and method for manufacturing the same

The present invention relates to a magnetoplumbite type hexagonal ferrite magnet and a method for manufacturing the same. Background art

As the oxide permanent magnet material, magnetoplumbite (M-type) hexagonal Sr ferrite or Ba ferrite is mainly used, and these are used as sintered magnets or bonded magnets. ing.

Of particular importance for the magnet properties are the residual magnetic flux density (Br) and the intrinsic coercivity (HcJ). B r is determined by the density and orientation of the magnet and the saturation magnetization (4πI s) determined by its crystal structure.

B r = 4 π I s X degree of orientation X density

Is represented by The type I S ferrite and the Ba ferrite have 4IS of about 4.65 kG. The limits of density and degree of orientation are about 98%, respectively, even for the sintered magnets with the highest values. Therefore, the Br of these magnets is limited to about 4.46 kG, and it has been practically impossible to obtain a high Br of 4.5 kG or more.

On the other hand, the present inventors have disclosed in Japanese Patent Application Laid-Open No. 11-154604, for example, a ferrite magnet having a high residual magnetic flux density and a high coercive force, which cannot be achieved with a conventional M-type magnet. Has been proposed. This ferrite magnet is at least one element selected from Sr, Ba, Ca and Pb, and Sr must be used. Include A as a rare earth element (including Y) and B i force Measure at least one element selected and always including L a, and whether it is C o or C o and Z n Is the element M, the composition ratio of the total of the metal elements of A, R, Fe and M is

A: 1 to 13 atomic%,

R: 0. 0 5~1 0 atom ^_0/0,

F e: 8 0~9 5 atom ^_0/0,

M: 0:! ~ 5 atomic%

Which has a main phase of hexagonal magnetoplumbite type filler. Also, Japanese Patent Application Laid-Open No. H10-149910 discloses that

(S r] _{_{- X R X) O · n}} [(F e -! Y M y) 2 0 3] ( where R is at least one L a, N d and P r, M is Mn, C o , Ni and Zn) at least one of the following basic compositions:

0.0 5 ≤ X ≤ 0.5,

{χΖ (2. 2 n)} ≤ y≤ {x / (1.8 n)},

5.70 ≤ n <6.00

It has been proposed. In order to improve the saturation magnetization, the invention described in the publication discloses that the Fe ion corresponding to the magnetic moment oriented in the antiparallel direction has a smaller magnetic moment than the Fe ion or has a non-magnetic property. In addition to replacing the Sr site with another element (R above), charge compensation is performed in order to suppress the generation of a different phase. Disclosure of the invention

In the process of examining the optimum conditions for manufacturing the ferrite magnets shown in the above publications, Replace 6 sites with 〇0, Ζη, etc. It has been found that the magnetic properties are greatly affected by the sintering conditions when R is replaced by a rare earth element. In other words, with ferrite magnets that do not contain Co, Zn, etc. and rare earth elements, ferrite magnets that contain Co, Zn, etc. and rare earth elements even if the firing conditions fluctuate to such an extent that the magnetic properties do not fluctuate to a problem. Then, it was found that the magnetic characteristics fluctuated remarkably. Specifically, as shown in FIG. 5, it was found that when the oxygen partial pressure in the firing atmosphere fluctuated, especially when the oxygen partial pressure was lower than in air, the coercive force was significantly reduced. It was also found that the coercive force fluctuated greatly even when the firing temperature fluctuated.

When manufacturing ferrite magnets, the firing process involves the absorption and release of oxygen due to the decomposition and combustion of the binder and dispersant, and the absorption and release of oxygen due to changes in the valences of the constituent elements and structural changes. However, the oxygen partial pressure in the firing atmosphere is constantly fluctuating. Since the range of the variation greatly varies depending on various conditions such as the composition of the object to be fired, the amount to be charged into the firing furnace, the type of additive, and the amount of added calorie, the oxygen partial pressure is controlled to be always constant. It is difficult. The firing temperature also varies depending on various factors, such as the distance of the object to be fired from the heat source, the height of the object to be fired from the hearth, and the air flow in the furnace that varies depending on the loading condition of the object to be fired. Therefore, it is difficult to control so that the temperature transition pattern is always constant. Therefore, it is difficult to stably realize the original high coercive force with a ferrite magnet whose composition is easily affected by the oxygen partial pressure fluctuation and the temperature fluctuation during firing.

In particular, continuous furnaces, which are effective in improving productivity during mass production, have larger fluctuations in oxygen partial pressure and temperature transition patterns than batch furnaces. For example, in a temperature transition pattern in a batch furnace, the heating, stabilization, and cooling processes are clear, but in a continuous furnace, there is virtually no stable part, and there is a case where the process directly transitions from heating to cooling. . In addition, furnaces that require low costs for firing, such as gas combustion furnaces that heat by utilizing the combustion of fuel, consume oxygen when burning the fuel, so the oxygen partial pressure in the furnace is extremely high. Fluctuate. Therefore, when using a continuous furnace, a combustion furnace, and a combustion furnace type continuous furnace, a ferrite magnet that is not particularly affected by fluctuations in oxygen partial pressure and temperature during firing is required.

The present invention has been made in view of such circumstances, and it is an object of the present invention to suppress fluctuations in magnetic properties due to fluctuations in firing conditions when manufacturing a fluorite magnet having a high residual magnetic flux density and a high coercive force. And

Such an object is achieved by the present invention of the following (1) to (8).

(1) A that contains at least one element selected from Sr, Ba, Ca and Pb is A, and at least one element selected from rare earth elements (including Y) and Bi When the element is R and at least one element selected from Co, Mn, Al, Cr, Ni and Zn is M, the metal elements are A, R, Fe, M and S containing i, determined Metatoki the content of these metal elements each metal oxide in terms of oxides, 3 content 1_Rei ₂ is 1.3 to 2.0 mole ^_0/0, And,

Atomic ratio {A + R— (F e + M) / 12} / S i

Is 1.1 to: 1.9,

A ferrite magnet containing hexagonal ferrite as the main phase.

(2) The ratio of the total of each of A, R, Fe and M to the total amount of metallic elements is A: 1 to 13 atomic%,

R: 0.05 to 10 atoms ⁰

F e: 80 to 95 atoms ⁰

M: 0.1 to 5 atomic%

The ferrite magnet of (1) above.

(3) It has at least two different Curie temperatures, and these Curie temperatures are between 400 ° C and 480. The ferrite magnet according to (1) or (2) above, which exists in the range of C and whose Curie temperatures are separated by 5 ° C or more from each other. (4) The method for producing a ferrite magnet according to any of (1) to (3) above,

A method for producing a fusible magnet, which includes a firing step of firing a compact of a raw material powder to obtain a sintered magnet, and in this firing step, the oxygen partial pressure in the atmosphere fluctuates.

(5) The method for producing a ferrite magnet according to (4), wherein the oxygen partial pressure in the atmosphere is 0.15 atm or less in at least a part of the firing step.

(6) The method for producing a ferrite magnet according to any of (1) to (3) above,

A method for producing a ferrite magnet, comprising a firing step of firing a molded body of a raw material powder to obtain a sintered magnet, wherein the firing temperature varies in the firing step.

(7) At least one compound containing at least one of the magnet constituent elements is added to the calcined material or particles each having a hexagonal frit as a main phase, and then molded and sintered. 4) A method for manufacturing a flat magnet according to any one of (6) to (6).

(8) The method for producing a ferrite magnet according to (7), wherein a part of the magnet constituent elements is one or more elements selected from the element R and the element M. Action and effect

In the present invention, the element R and the element M are added to a magnet in order to obtain a high residual magnetic flux density and a high coercive force. As shown in the experimental results in FIG. 5, the inventors of the present invention have found that the firing conditions (oxygen partial pressure in the atmosphere) are higher in the case of the fusible magnet to which the elements R and M are added than in the case of the conventional fusible magnet which does not contain these elements. And the calcination temperature), the fluctuation of the magnetic properties was significantly increased. It has been found that optimizing the Si amount and the atomic ratio {A + R— (F e + M) / 12} / S i is extremely effective in suppressing this fluctuation in magnetic properties. .

As described above, ferrite magnets containing element R and element M are not known. Have been. However, it is not known that when the elements R and M are added, the fluctuations in the magnetic properties due to the fluctuations in the firing conditions are significantly increased. Then, in order to suppress the fluctuation of the magnetic properties, the amount of Si and the atomic ratio {A + R— (Fe + M) / \ 2} / Si are controlled so as to be within the range limited by the present invention. Not even known. Further, the present inventors first produced a calcined material having a hexagonal ferrite containing at least an element A as a main phase, and provided the calcined material with at least one kind of magnet constituent elements, in particular, an element R And the method of adding at least one element selected from element M and then sintering to obtain a magnet (referred to as post-addition method in this specification), the effect of fluctuations in firing conditions during sintering Is especially large. Then, it has been found that the control of the Si amount and the atomic ratio {A + R— (Fe + M) / 12} ZSi in the present invention is particularly effective in this case. Ferrite magnets manufactured by the post-addition method as described above usually have a Curie temperature of 2 or more. A magnet containing Co as the element M and having a Curie temperature of 2 or more has improved magnetic properties as compared to a magnet having the same composition and only one Curie temperature.

Regarding the post-addition method, see Japanese Patent Application Laid-Open No. Hei 11-19555 / 16 published after the filing of the basic application of the present application (Japanese Patent Application No. 11-193338). Published on July 21, 2001). However, the publication does not disclose that when the post-addition method is used, the fluctuations in the magnetic properties due to the fluctuations in the firing conditions are further increased, and the Si content and the atomic ratio {A + R— (Fe + M) / 1 2} / Si is not described to be controlled so as to fall within the range limited by the present invention. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a graph showing the relationship between the oxygen partial pressure in the firing atmosphere and the magnetic properties of the sintered magnet.

FIG. 2 is a graph showing the relationship between the firing temperature and the magnetic properties of the sintered magnet. FIG. 3 is a graph showing the relationship between the atomic ratio {A + R— (F e + M) / 12} / S i and the magnetic properties of the sintered magnet.

FIG. 4 is a graph showing the relationship between the CaO content and the magnetic properties of the sintered magnet. Figure 5 is a graph showing the relationship between the oxygen concentration in the firing atmosphere and the coercive force HcJ of the sintered magnet.

FIG. 6 is a reference graph for explaining how to determine two Curie temperatures. BEST MODE FOR CARRYING OUT THE INVENTION

Sintered magnet

The ferrite magnet of the present invention has a hexagonal magnetoplumbite-type (M-type) ferrite as a main phase, and contains A, R, Fe, M, and Si as metal elements. Element A is at least one element selected from Sr, Ba, Ca and Pb. Element R is at least one element selected from rare earth elements (including Y) and Bi. The element M is at least one element selected from Co, Mn, Al, Cr, 1 ^ 1 and 211. In the magnet of the present invention, when the determined content of in terms the metal oxide of the metal element contained in each general oxides, the content of S i 0 ₂ 1. 3~2. 0 mol ^_0/0, preferably from 1.4 to 1.9 mol ^_0/0, and,

Atomic ratio {A + R— (F e + M) / 1 2} / S i

Is 1.:! To 1.9, preferably 1.2 to 1.7.

As described above, in the present invention, a certain amount or more of Si is contained, A + R is made excessive with respect to (Fe + M) 12, and the degree of this excess is made to correspond to the Si amount. As a result, the rate of change of the magnetic properties when the oxygen partial pressure or the temperature fluctuates becomes small, and in particular, a decrease in the coercive force under a low oxygen partial pressure can be significantly suppressed. This contrast, when the content of S i 0 ₂ is too small, fluctuation and also the oxygen partial pressure during firing PC Picture Island 53

However, when the firing temperature fluctuates, the magnetic characteristics greatly fluctuate. On the other hand, if the content of Sio ₂ is too large, the ratio of non-magnetic components such as vitreous material occupying the magnet becomes high, and the magnetic properties, particularly the residual magnetic flux density, become low. Even if {A + R— (F e + M) / 12} / S i is too small or too large, the magnetic properties will change when the oxygen partial pressure and / or the firing temperature fluctuate during firing. Greatly fluctuates. When calculating the content by converting the metal element contained in the magnet to its general oxide, the iron oxide, strontium oxide, barium oxide, calcium oxide, rare earth element (RE) oxide, bismuth oxide, cobalt oxide, manganese oxide, aluminum, chromium oxide and oxides Kei arsenide, respectively F e ₂ 〇 _{3, S r O, B a} O, C a O, RE 2 〇 ₃ (however, P

reOu C e is C e 0 _2, Ding Ding _{_{_{4 0 7), B i 2}}} 0 3, C o O, converted MnO, the A 1 ₂ 〇 _{_3,} C r ₂ 0 ₃ and S i 0 _2. The atomic ratio RZM in the magnet of the present invention is preferably 0.7 to 1.5.

When M is divalent, it is preferable that M = R in terms of valence balance, as described later. By making R excessive relative to 1SM, the effect of the present invention is enhanced.

The effect of the present invention is that the magnet of the present invention has at least two different Curie temperatures, these Curie temperatures are in the range of 400 ° C to 480 ° C, and the absolute value of these differences is It is particularly effective when the temperature is 5 ° C or higher. By adopting a structure having a plurality of Curie temperatures as described above, the squareness HkZHcJ can be remarkably improved, and the content of expensive Co and R can be reduced.

The Curie temperature (T c) is the temperature at which a magnetic material changes from ferromagnetic to paramagnetic. There are several methods for measuring Tc, especially for magnetic materials with multiple Tc, by drawing the magnetization-temperature curve while changing the temperature of the measurement sample with a heater or the like. Find Tc. Here, a vibrating magnetometer (VSM) is often used to measure magnetization. This is because it is easy to secure a space for installing a heater etc. around the measurement sample. The measurement sample may be a powder or a sintered body, but in the case of a powder, it must be fixed with a heat-resistant adhesive or the like. It is preferable to make the sample as small as possible within a range where the measurement accuracy of the magnetization can be ensured so that the entire sample can be heated uniformly at the time of measurement, and it is preferable to make the heating rate relatively slow.

The sample may be anisotropic or isotropic, but in the case of an anisotropic sample, it is preferable to measure in the c-axis direction after magnetization in the c-axis direction, which is the direction of easy magnetization. For isotropic samples, measure magnetization in the same direction as the magnetization direction. The sample is magnetized by applying a sufficiently large magnetic field of 1 T or more. Normally, after magnetizing at room temperature, the magnetization of the sample is measured while increasing the temperature.At this time, no magnetic field is applied, or the measurement is performed under a weak magnetic field of 0.1 T or less even if applied. Is preferred. This is because if a large magnetic field is applied, paramagnetic components are detected at temperatures above the temperature of the lily, and the Curie temperature tends to be unclear.

Figure 6 shows an example where two Curie temperatures appear. FIG. 6 is a graph showing the vicinity of the Curie temperature of the σ-T curve with the temperature T as the horizontal axis and the magnetization as the vertical axis. The σ-Τ curve is convex around the temperature where the magnetization starts to decrease sharply. When the temperature is increased from here, the magnetization σ changes as follows. First, the magnetization decreases sharply as the temperature rises. Next, the σ-Τ curve changes to a downward convex, and the magnetization decreases gradually. Next, the σ-Τ curve changes to a convex shape again, and the magnetic 匕 is sharply reduced. Next, the σ-Τ curve changes to a convex downward again, and the magnetization decreases gradually, but finally the magnetization becomes zero. In the σ-Τ curve, the three intangents at the inflection point, that is, the point that changes from upwardly convex to downwardly convex or the point that changes from downwardly convex to upwardly convex, are represented by I, II, ΠΙ. The intersection of the tangents I and II is the Curie temperature Tc1 on the low temperature side, and the intersection of the tangent III and the horizontal axis is the Curie temperature Tc2 on the high temperature side. Even when there are three or more Curie temperatures, each Curie temperature can be obtained from the σ-Τ curve according to this method. 553

Ten

When a plurality of Curie temperatures are present, the absolute value of the difference between them is 5 ° C or more, preferably 10 ° C or more. These Curie temperatures are in the range of 400 to 480 ° C, preferably in the range of 400 to 470 ° C, and more preferably in the range of 430 to 460 ° C. The Curie temperature of pure M-type Sr ferrite is about 465 ° C.

Here, the ratio (σΐΖσΚΤ) of the magnetization (σΐ) at the lowest Curie temperature to the magnetization (aRT) at 25 ° C is preferably 0.5% to 30%, more preferably 1% to 20%. And more preferably 2% to: 10%. When σ 1 σ RT is less than 0.5%, it is difficult to detect the Curie temperature on the higher temperature side. It is thought that the multiple Curie temperatures appear because the ferrite crystal has a multiphase structure of magnetically different 磁気 -type ferrite. However, even when there are multiple Curie temperatures, single-phase structure consisting of なる phase is detected by ordinary X-ray diffraction. When the post-addition method described above is used, usually, a plurality of Curie temperatures are present. In this case, the number of Curie temperatures is almost two in most cases.

In the magnet of the present invention, the ratio of the total of A, R, Fe and に対する to the total amount of metal elements is preferably

A: 1 to 13 atomic%,

R: 0.05-10 atoms ⁰ /. ,

F e: 80-95 atoms ⁰ /. ,

M: 0.:! ~ 5 atom%

And more preferably

A: 3~1 1 atom ^_0/0,

R: 0.2 to 6 atomic%,

F e: 83~94 atom ^_0/0,

M: 0.3 to 4 atomic% And more preferably

A: 3-9 atom%,

R: 0.5 to 4 atomic%,

F e: 86 to 93 atomic%,

M: 0.5 to 3 atomic%

It is. When the content of the element A is too small, not be generated or M-type ferrite, the greater the alpha-F e ₂ 0 nonmagnetic phase such as _3. When the content of the element Α is too large, it will not be generated or M type Blow wells, it is often non-magnetic phase such as S r F E_〇 ₃ _ _x. The ratio of Sr in A is preferably at least 51 at%, more preferably at least 70 at%, and even more preferably at least 100 at%. If the ratio of Sr in the element A is too low, it is impossible to obtain both the enhancement of the saturation magnetization and the remarkable improvement of the coercive force. If the content of the element R is too small, the amount of the solid solution of the element M becomes small, so that the effect of improving the magnetic properties becomes insufficient. If the content of the element R is too large, the amount of non-magnetic hetero phase such as orthofluorite increases. If the content of the element M is too small or too large, the effect of improving the magnetic properties becomes insufficient.

In the magnet of the present invention, the atomic ratio of A, R, Fe and M is

Formula I (F e ₁₂ _.y M _y ) ₂ 0 ₁₉

Can be represented by In the above formula I, x, y, and z are such that the above {A + R— (F e + M) / 12} / S i is within the above-mentioned limited range, and the above-mentioned RZM is within the above-mentioned preferable range. Should be determined, but

0.04 ≤ X ≤ 0.9,

0.04≤y≤1.0, especially 0.04≤y≤0.5,

0.8 ≤ x / y≤ 5,

0.7 ≤ z <1

Is preferably not deviated. In the above formula I, if x is too small, that is, if the amount of the element R is too small, the solid solution amount of the element M in the hexagonal ferrite cannot be increased, so that the effect of improving the saturation magnetic field and the effect of improving the saturation magnetization can be reduced. The effect of improving the isotropic magnetic field becomes insufficient. If X is too large, the element R cannot be substituted in the hexagonal ferrite to form a solid solution. For example, orthoferrite containing the element R is generated and the saturation magnetization decreases. If y is too small, the effect of improving the saturation magnetization and the effect of improving Z or the anisotropic magnetic field become insufficient. If y is too large, the element M cannot be substituted into the hexagonal ferrite to form a solid solution. In addition, even if the element M can be substituted and dissolved, the anisotropy constant (K and the anisotropic magnetic field (Η _Α ) deteriorate significantly. If ζ is too small, S r and element R are reduced. for including non-magnetic phase is increased, the saturation magnetization i inhibit come summer low. z is too large a _ F e ₂ 0 ₃ phase or element comprising M non-magnetic spinel Blow wells phase increases, saturation magnetization Is getting lower.

In the above formula I, if xZy is too small or too large, the valences of the element R and the element M cannot be balanced, and a heterogeneous phase such as a W-type ferrite is easily generated. When the element M is a divalent ion and the element R is a trivalent ion, it is general that X / y = 1 in terms of valence equilibrium. It is preferable to do it. The reason why the allowable range is large in the region where x / y is greater than 1 is that even when y is small, the valence can be balanced by the reduction of F e ³⁺ → F e ²⁺ .

In the above formula I representing the composition, the number of atoms of oxygen (O) is 19. This is because M is all divalent, R is all trivalent, and x = y, z = l It shows the stoichiometric composition ratio of oxygen at that time. Depending on the types of M and R, and the values of x, y, the number of oxygen atoms differs. Also, for example, when the firing atmosphere is a reducing atmosphere, oxygen vacancies (vacancies) may occur. In addition, Fe usually exists in trivalent form in M-type ferrite, but this may change to divalent state. Also, the valence of the element M such as Co may change. The ratio of oxygen to the metal element changes depending on these factors. In this specification, the number of oxygen atoms is indicated as 19 regardless of the type of R and the values of x, y, and z, but the actual number of oxygen atoms may be a value slightly deviated from this. .

The magnet composition can be measured by fluorescent X-ray quantitative analysis or the like. The presence of the main phase can be confirmed by X-ray diffraction, electron beam diffraction, or the like.

In order to increase the saturation magnetization and coercive force of the magnet, it is preferable to use at least one of Sr and Ca as the element A, and it is particularly preferable to use Sr. The proportion of Sr + Ca in A is preferably at least 51 at%, more preferably at least 70 at%, and even more preferably at least 100 at%.

As the element R, preferably at least one kind of lanthanide, more preferably at least one kind of light rare earth, and still more preferably at least one kind of La, Nd and Pr are used, and especially La is always used. Is preferred. The proportion occupied by La in R is preferably at least 40 at%, more preferably at least 70 at%. In order to improve the saturation magnetization, it is most preferable to use only La as R. This is because, when comparing the solubility limit of hexagonal M-type ferrite, La is the largest. Therefore, if the ratio of La in R is too low, the amount of solid solution of R cannot be increased, and as a result, the amount of solid solution of element M cannot be increased, and the effect of improving magnetic properties is small. It will be connected. When Bi is used in combination, the calcining temperature and the sintering temperature can be lowered, which is advantageous in production.

As the element M, it is preferable to use at least one of Co and Zn, particularly Co. The proportion of Co in M is preferably at least 10 atomic%, more preferably at least 20 atomic%. If the proportion of Co in M is too low, the coercive force is insufficiently improved.

The magnet may contain B ₂ 0 _3. It is possible to lower the calcining temperature Contact and sintering temperature by containing B ₂ 0 _3, which is advantageous on production. The content of B ₂ 0 ₃ Is preferably 0.5% by weight or less of the whole magnet powder. When B ₂ 0 ₃ content is too large, the saturation magnetization will be summer low.

The magnet powder may contain at least one of Na, K and Rb. When these are converted into Na ₂ 〇, K ₂ O and Rb ₂それぞれ, respectively, the total of these contents is preferably not more than 3% by weight of the whole magnet powder. If these contents are too high, the saturation magnetization will be low. Can and these elements expressed in M ^1, M ¹ during ferrite, for example

It is contained in the form of In this case, it is preferable that 0.3 <a≤0.5. If a is too large, the saturation magnetization will be low, and the element M ¹ will evaporate in large quantities during firing.

Also, these forces, such as Ga, In, Li, Mg, Cu, Ti, Zr, Ge, Sn, V, Nb, Ta, Sb, As, W, Mo, etc. It may be contained as an oxide. These contents are 5% by weight of gallium oxide in terms of oxides of stoichiometric composition. /. Below, indium oxide 3% by weight, lithium oxide 1% by weight, magnesium oxide 3% by weight, copper oxide 3% by weight, titanium oxide 3% by weight, zirconium oxide 3% by weight, germanium oxide 3% by weight Below, 3% by weight of tin oxide, 3% by weight or less of vanadium oxide, 3% by weight or less of niobium oxide, 3% by weight or less of tantalum oxide, 3% by weight or less of antimony oxide, 3% by weight or less of arsenic oxide, 3% by weight of tungsten oxide % Or less, and preferably 3% by weight or less of molybdenum oxide.

Production method

Next, a method for manufacturing a magnet will be described.

The production method of the present invention includes a firing step of firing a compact of the raw material powder to obtain a sintered magnet. The method for producing the raw material powder is not particularly limited. For example, the raw material powder may be produced by a so-called calcination by a solid phase reaction, or may be produced by a coprecipitation method or a hydrothermal synthesis method. Hereinafter, the case where the calcining step is provided will be mainly described.

First, after the starting materials are mixed, they are calcined to obtain a calcined body. This calcined body is not disintegrated or pulverized to powder to obtain the raw material powder. After the raw material powder is formed, it is fired.

The magnet of the present invention having the above-described composition can be used for the above-mentioned firing process even if the oxygen partial pressure in the atmosphere fluctuates and / or the firing temperature (stable temperature) fluctuates. Small fluctuations in magnetic force. The present invention exhibits a remarkably high effect when the oxygen partial pressure in the firing atmosphere is 0.15 atm or less, particularly when it is 0.10 atm or less. Therefore, the present invention is suitable for using a gas continuous furnace in which the oxygen partial pressure in the furnace is low. Further, in the present invention, even if the stable temperature fluctuates within a range of, for example, 60 ° C., fluctuations in magnetic characteristics, particularly fluctuations in coercive force, can be suppressed to a small level.

Next, preferable conditions for manufacturing the magnet of the present invention will be described.

As a starting material, an oxide powder or a compound which becomes an oxide by firing, such as a carbonate, a hydroxide, or a nitrate, is used. The average particle size of the starting material is not particularly limited, but is usually preferably about 0.1 to 2 / im. In particular, iron oxyferrite is preferably used in the form of fine powder. Specifically, the primary particles having an average particle diameter of preferably 1 μπι or less, more preferably 0.5 μπι or less are used. Further, as the starting material containing the element Α, it is preferable to use a hydroxide or a carbonate because of good stability during stocking.

The calcination may be usually performed in an oxidizing atmosphere such as air. The calcination conditions are not particularly limited, but usually, the stabilization temperature is 100 to 135 ° C., and the stabilization time is 1 second to 10 hours, more preferably 1 second to 3 hours. The calcined body is substantially magne It has a topranite-type ferrite structure, and the average particle size of the primary particles is preferably 2 / xm or less, more preferably 1 μπι or less, further preferably 0.1 to 1 μιη, and most preferably 0.1 to 0.5 / m. The average particle size can be measured with a scanning electron microscope.

In the present invention, it is favorable preferable to use S i 0 ₂ as the starting material for supplying the S i. S i 0 ₂ may be mixed with other starting material before calcination, may be mixed after calcination, may be distributed to the addition of S i 0 ₂ in the front and calcination after calcination . If both are added S i 0 ₂ is before firing small, the effect of the present invention is realized. However, in order to further improve this onset bright effects, some also less of S i 0 _2, preferably it is preferred to add all the parts, after calcination.

Also, it is not necessary to mix all of the starting material compounds other than Sio ₂ before calcination, and a part or all of each compound may be added after calcination.

Method of adding S io ₂ except the starting material compound after calcination, i.e. in the post-addition method, first, to produce a calcined material for the main phase a hexagonal ferrite containing at least the element A. Next, after pulverizing the calcined material or at the time of pulverizing, a compound to be added later (post-additive) is added to the calcined material, and then molded and sintered. In order to obtain a magnet having a plurality of Curie temperatures as described above, one or two or more elements selected from the above-mentioned element R and the above-mentioned element M, preferably the element R and the element M are added to the post-additive. The compound to be added later is selected so that at least both are contained.

The amount of the post-additive is preferably 1 to 100 volumes of the calcined material. / ₀ , more preferably 5 to 70% by volume, still more preferably 10 to 50% by volume. As the compound containing the element R, an R oxide can be used, but since the R oxide has a relatively high solubility in water, there is a problem that it flows out during wet molding. In addition, since it is hygroscopic, it can easily cause weighing errors. Therefore, the R compound is preferably a carbonate or a hydroxide. The post-additives of the other elements are oxides or calcined A compound that becomes an oxide upon formation, for example, a carbonate or a hydroxide may be added. The post-additive may be added after calcining and before sintering, but is preferably added at the time of pulverization described below. However, in the present invention, a post-additive may be added to particles that are produced by a coprecipitation method, a hydrothermal synthesis method, or the like instead of a calcined material, and that include at least the hexagonal ferrite containing the element A as a main phase. Good.

As for the element R or the element M, it is desirable that at least 30%, more preferably at least 50%, of the total amount contained in the magnet is added as a post-additive. For other elements, the amount added as a post-additive is not particularly limited. The average particle size of the post-additive is preferably about 0.1 to 2 μm.

Here, the addition amount of the post-additive will be specifically described. For example,

S r: L a: F e: Co = 0.8: 0.2: 1 1.8: 0.2

If the purpose is to manufacture a sintered magnet that is

Sr: Fe = 0.8: 9.6 (= 1: 12)

And calcined at the ratio of

L a: F e: C o = 0.2: 2.2: 0.2

By adding the post-additive and firing, the sintered magnet having the above-described target composition can be obtained. Also, for example,

Sr: F e = 0.8: 1 1.8 (= 1: 14.75)

And then calcined (at this time, the calcined material is in the two-phase state of M-type Sr ferrite and _a — Fe ₂ 〇 ₃ ).

L a: C o = 0.2: 0.2

The sintered magnet having the above-mentioned target composition can be obtained also by adding the post-additive and firing.

The reason why sintered magnets manufactured by the post-addition method have multiple Curie temperatures is not clear, but is considered as follows. At the time of sintering, calcining with M-type ferrite phase The reaction between the material particles and the post-additive occurs, and in the process, it is considered that an M-type ferrite portion having a high La concentration and a Co concentration and an M-type ferrite portion having these low concentrations are generated. In other words, assuming that La and Co in the post-additive diffuse toward the center of the calcined material particles during sintering, the concentration of La and Co in the crystal grains after sintering is as follows: It is considered that the surface layer tends to be higher than the central part. Since the Curie temperature depends on the substitution amount of La and Co, especially the substitution amount of La, the presence of multiple Curie temperatures reflects the existence of La and Co concentration distribution in the crystal grains. it is conceivable that. Next, molding and pulverization which is a preceding step will be described.

It is preferable to use a wet molding method for molding the raw material powder. In wet molding, it is preferable to use a molding slurry containing a raw material powder, water as a dispersion medium, and a dispersant. In order to further enhance the effect of the dispersant, it is preferable to provide a wet pulverization step before the wet molding step. When the calcined body powder is used as the raw material powder, the calcined body powder is generally composed of granules. It is preferable to provide a pulverizing step. When the raw material powder is manufactured by a coprecipitation method or a hydrothermal synthesis method, a dry coarse pulverization step is not usually provided, and a wet pulverization step is not necessarily required. Preferably, a wet grinding step is provided. Hereinafter, a case where the calcined body particles are used as a raw material powder and a dry coarse grinding step and a wet grinding step are provided will be described. In the dry coarse pulverization step, pulverization is usually performed until the BET specific surface area becomes about 2 to 10 times. After pulverization, the average particle size is preferably about 0.1 to 1 μπι, and the BET specific surface area is preferably about 4 to 1 O m ² / g. The pulverizing means is not particularly limited, and for example, a dry vibration mill, a dry attritor (medium stirring type mill), a dry ball mill, or the like can be used, but a dry vibration mill is particularly preferable. The pulverization time may be appropriately determined according to the pulverization means. When some starting materials are added after calcination, it is preferable to add them in this dry coarse pulverization step. For example, S i〇 ₂ The C a C 0 ₃ as a C a O by forming, it is preferable to add each of the at least in part in the dry coarse Kona碎process.

Dry coarse pulverization also has the effect of reducing the coercive force HcB by introducing crystal strain into the calcined particles. Decrease in coercive force suppresses agglomeration of particles and improves dispersibility. In addition, the degree of orientation is improved by making the layer soft magnetic. The softened particles return to their original hard magnetism in the subsequent sintering process.

After the dry coarse pulverization, a pulverization slurry containing the pulverized particles and water is prepared, and wet pulverization is performed using the slurry. The content of the raw material powder in the pulverizing slurry is preferably about 10 to 70% by weight. The pulverizing means used for the wet pulverization is not particularly limited, but usually, a ball mill, an attritor, a vibration mill or the like is preferably used. The pulverization time may be appropriately determined according to the pulverization means.

After wet grinding, the slurry for grinding is concentrated to prepare a slurry for molding. Concentration may be performed by centrifugation or the like. The content of the raw material powder in the molding slurry is preferably about 60 to 90% by weight.

In the wet molding process, molding in a magnetic field is performed using a molding slurry. Compacting pressure 0. 1~ 0. 5 t / cm 2 or so, the applied magnetic field. 5 to 1 5 kOe about and Surebayore.

When a non-aqueous dispersion medium is used for the molding slurry, a high degree of orientation can be obtained. However, in order to reduce the load on the environment, it is preferable to use an aqueous dispersion medium. In order to compensate for the decrease in the degree of orientation due to the use of the aqueous dispersion medium, it is preferable that a dispersant is present in the molding slurry. The dispersant used in this case is an organic compound having a hydroxyl group and a carboxyl group, a neutral salt thereof, or a lactone, an organic compound having a hydroxymethylcarboxyl group. It is preferably an organic compound having an enol-type hydroxyl group which can be dissociated as a force or an acid, or a neutralized salt thereof.

When a non-aqueous dispersion medium is used, for example, JP-A-6-53064 As described in above, a dispersion medium is prepared by adding a surfactant such as oleic acid to an organic solvent such as toluene-xylene. By using such a dispersion medium, it is possible to obtain a high degree of magnetic orientation of up to about 98% even when ferrite particles of submicron size that are difficult to disperse are used.

Each of the above organic compounds has 3 to 20 carbon atoms, preferably 4 to 12 carbon atoms, and has a hydroxyl group bonded to 50% or more of the carbon atoms other than the carbon atom double-bonded to the oxygen atom. . When the number of carbon atoms is 2 or less, the effect of improving the degree of orientation becomes insufficient. Even if the number of carbon atoms is 3 or more, the effect is still insufficient if the bonding ratio of the hydroxyl group to a carbon atom other than the carbon atom double-bonded to the oxygen atom is less than 50%. The bonding ratio of the hydroxyl group is limited for the above organic compound, and is not limited for the dispersant itself. For example, when a lactone of an organic compound (hydroxycarboxylic acid) having a hydroxyl group and a carboxyl group is used as the dispersant, the limitation of the bonding ratio of the hydroxyl group is applied to hydroxycarbonic acid itself instead of lactone.

The basic skeleton of the organic compound may be linear or cyclic, and may be saturated or contain an unsaturated bond.

As the dispersant, specifically, hydroxycarboxylic acid or a neutralized salt thereof or a lactone thereof is preferable. In particular, dalconic acid (C = 6; OH = 5; COOH = 1) or a neutralized salt thereof or Lactone, ratatobionic acid (C = 12; OH = 8; COOH = 1), tartaric acid (C = 4; OH = 2; C〇〇H = 2) or a neutralized salt thereof, darcoheptonic acid "V —Lactone (C = 7; OH = 5), and among these, dalconic acid or its neutralized salt or its lactone is preferable because of its high effect of improving the degree of orientation and low cost.

As an organic compound having a hydroxymethylcarbonyl group, sorbose is preferred. As the organic compound having an enol-type hydroxyl group that can be dissociated as an acid, asconolevic acid is preferable.

In the present invention, cunic acid or a neutralized salt thereof can also be used as a dispersant. Cuenoic acid has a hydroxyl group and a carboxyl group, but does not satisfy the condition that 50% or more of the carbon atoms other than the carbon atom double-bonded to the oxygen atom are bonded to the hydroxyl group. However, the effect of improving the degree of orientation is recognized.

The structures of some of the above preferred dispersants are shown below.

D-Dalconic acid-D-Dalcoheptonic acid

T-Lacton

Lactic acid

Lithic acid

Ascorbic acid L- (-) -Sorbose

The degree of orientation by the magnetic field orientation is affected by the pH of the slurry. Specifically, the degree of orientation p H is too low is reduced, a compound that indicates the nature of the acid in aqueous solution thereby as _c dispersant remanence after sintering is affected, for example arsenate Dorokishikarubo phosphate When such a method is used, the pH of the slurry is lowered. Therefore, it is preferable to adjust the pH of the slurry, for example, by adding a basic compound together with the dispersant. As the above basic compound, ammonia and sodium hydroxide are preferable. Ammonia may be added as aqueous ammonia. It is to be noted that the use of sodium salt of hydroxycarboxylic acid can prevent a decrease in pH.

When using the S I_〇 ₂ and C a CO ₃ as a raw material, arsenate Dorokishika carboxylic acid and the use of its lactone, S i 0 ₂ and C a with a slurry one supernatant upon primarily molding slurry prepared as a dispersant C_〇 would ₃ flows out, HcJ can not be obtained Do throat desired performance decreases. Further, when the high p H, such as by adding the basic compound, outflow of S i 0 ₂ and C a C 0 ₃ is more. In contrast, the use of the calcium salt of hydroxycarboxylic acid as a dispersing agent, the outflow of S i O ₂ and C a C_〇 ₃ is suppressed. However, may be added to the basic compound, when or with Natoriumu salt as a dispersing agent, if excessively added with respect to the target composition of S i 0 ₂ and C a C 0 _3, S i in the magnet 〇 The shortage of ₂ and C a O can be prevented. In the case of using the Asukorubin acid, outflow of S io ₂ and C a C 0 ₃ is not substantially observed.

For the above reasons, the pH of the slurry is preferably 7 or more, more preferably 8-11.

The kind of the neutralizing salt used as the dispersant is not particularly limited, and may be any of a calcium salt and a sodium salt. For the above-mentioned reason, the calcium salt is preferably used. If sodium salt is used as the dispersant or aqueous ammonia is added, In addition to the outflow of components, there is a problem that cracks are generated in the formed body and the sintered body, and the formed body becomes sintered.

Incidentally, two or more dispersants may be used in combination.

The amount of the dispersant added is preferably 0.05 to 3.0% by weight, more preferably 0.10 to 2.0% by weight, based on the raw material powder. If the amount of the dispersant is too small, the improvement of the degree of orientation becomes insufficient. On the other hand, if the amount of the dispersing agent is too large, cracks occur in the formed body and the sintered body, and the formed body and the sintered body tend to crack.

When the dispersant is ionizable in an aqueous solution, for example, an acid or a metal salt, the amount of the dispersant to be added is an ion equivalent. That is, the amount to be added is determined by converting to organic components excluding hydrogen ions and metal ions. When the dispersant is a hydrate, the amount added is determined excluding water of crystallization. For example, when the dispersant is calcium dalconate monohydrate, the amount to be added is calculated in terms of dalconate ion. Also, when the dispersant is made of lactone or contains lactone, the amount of addition is calculated in terms of hydroxycarboxylate ions, assuming that all the lactone is opened to form hydroxycarboxylic acid.

The timing of adding the dispersant is not particularly limited, and may be added at the time of dry coarse pulverization, may be added at the time of preparing a slurry for wet pulverization, and may be partially added at the time of dry coarse pulverization. Calories and the remainder may be added during wet grinding. Alternatively, it may be added by stirring after wet milling. In any case, since the dispersant is present in the slurry for molding, the effect of the addition of the dispersant is realized. However, the effect of improving the degree of orientation is higher when it is added during pulverization, especially during dry coarse pulverization. Vibration mills and the like used for dry coarse grinding give larger energy to particles than ball mills and the like used for wet grinding, and the temperature of the particles increases, so that the chemical reaction is likely to proceed. Conceivable. Therefore, if a dispersant is added during dry coarse pulverization, the amount of the dispersant adsorbed on the particle surface increases, and as a result, a higher degree of orientation is obtained. It is considered something. Actually, when the amount of the dispersant remaining in the molding slurry (which is considered to be almost equal to the adsorption amount) was measured, it was found that the dispersant added at the time of dry coarse pulverization was added more than at the time of wet pulverization. The ratio of the residual amount to the amount increases. In the case where the dispersant is added in a plurality of times, the amount of each addition may be set so that the total amount is within the above-mentioned preferable range.

After the wet molding, the molded body is dried, and then the added dispersant is sufficiently decomposed and removed by heat treatment in air or nitrogen, preferably at a temperature of 100 to 500 ° C. I do. Drying and the above heat treatment may be performed continuously.However, if the molded body is rapidly heated without being sufficiently dried, cracks will be generated in the molded body, and it will be loose from room temperature to about 10 oC. It is preferable that the temperature be raised and dried sufficiently in this temperature range. After the heat treatment, firing is performed to obtain a ferrite sintered magnet. The stable temperature at the time of calcination is preferably 1150 to 1250 ° C, more preferably 1160 to 1250 ° C, and the time for maintaining the stable temperature is preferably 0. 5 to 3 hours. Note that, as described above, for example, a stabilization process may not be provided in a continuous furnace or the like, but even in such a case, sufficient performance is obtained with the ferrite magnet of the present invention.

The average crystal grain size of the magnet of the present invention is preferably 2 _μm or less, more preferably 1 μra or less, and further preferably 0.5 to 1.0 μππι. Even if it exceeds 1 m, a sufficiently high coercive force can be obtained. The crystal grain size can be measured by a scanning electron microscope. The specific resistance is usually 10 ° Ωηι or more.

The compact was crushed using a crusher or the like, and classified by sieving or the like so as to have an average particle size of about 100 to 700 / im to obtain magnetically oriented granules. After sintering, a magnet can be obtained by sintering.

In the ferrite magnet of the present invention, by containing the element R and the element M, A coercive force and high saturation magnetization are realized. Therefore, if the shape is the same as that of a conventional ferrite magnet that does not contain these elements, the generated magnetic flux density can be reduced, and when applied to a motor, a high torque can be realized. When applied to headphones, enhanced magnetic circuits can provide sound quality with good linearity, contributing to higher performance of applied products. If the same function as a conventional ferrite magnet is sufficient, the size (thickness) of the magnet can be reduced (thinned), which contributes to reduction in size and weight (thinness). Also, in motors where the field magnets used to be wound-type electromagnets, it is possible to replace them with ferrite magnets, reducing weight, shortening the production process, and reducing costs. Can contribute. Furthermore, because of its excellent coercive force (HcJ) temperature characteristics, it can be used in low-temperature environments where there was a danger of low-temperature demagnetization (permanent demagnetization) of ferrite magnets in the past. The reliability of the products used can be significantly increased. Further, according to the present invention, even if the sintering conditions are unstable, the ferrite magnet having the above-described excellent characteristics can be stably mass-produced. Large contribution to cost reduction.

The magnet of the present invention is processed into a predetermined shape, and is used for a wide range of applications as described below.

For example, for fuel pumps, for power windows, for ABS, for fans, Pino, etc. , Power steering, active suspension, starter, door lock, electric mirror, etc. automotive motors; FDD spindles, VTR capstans, VTR rotary heads, VTR reels, VTR loading, For VTR camera capstan, VTR camera rotary head, VTR camera zoom, VTR camera focus, boombox etc.capstan, CD, LD, MD spindle, CD, LD, MD loading, CD, LD light OA and AV equipment motors for pickups; air conditioner compressors, refrigerator compressors, Motors for home appliances such as electric tool drive, electric fan, microwave fan, microwave plate rotation, mixer drive, dryer fan, shaver drive, electric toothbrush, etc .; robot shaft, joint drive, robot main Motors for FA equipment such as drive, machine tool tape drive, machine tool belt drive, etc .; motor generators, magnets for speakers and headphone, magnetron tubes, MRI magnetic field generators, CD-ROM It can be used for clampers, distributor sensors, ABS sensors, fuel and oil level sensors, magnet latches, etc. Example

Example

S r C_〇 ₃ as a raw _{_{material, F e 2 0 3, S}} i 0 blended ₂ and C a the powder of C 0 _3, after 2 hours mixing and pulverization by a wet attritor, dried sized And made into condyles.

The granules were calcined in air at 1250 ° C for 3 hours to obtain a calcined material. The composition of this calcined material (analytical value by fluorescent X-ray analysis) is shown in Table 1-1.

Then, as a post-additive, S I_〇 _2, C a C0 _3, lanthanum carbonate _{_{[L a 2 (CO 3) 3}} - 8H 2 〇] a, (mixture of C o ₃ 0 ₄ and C oO) cobalt oxide It was added to the calcined material, and 0.6% by weight of calcium dalconate was further added. The mixture was dry-pulverized for 20 minutes using a batch vibrating rod mill to obtain a coarsely pulverized powder. Then, the F e ₂ 0 ₃ was added to the coarsely pulverized powder, after 40 hours wet grinding by a ball mill to obtain a molding slurry was dehydrated concentrated to a concentration of about 78%.

Next, the molding slurry was subjected to compression molding while dewatering, to obtain a molded body having a diameter of 30 mm and a height of 18 mm. At the time of compression molding, a magnetic field of about 13 kOe was applied in the compression direction. The molding pressure was 0.4 t / cm ² .

Next, the compact is fired to form a sintered magnet, and the upper and lower surfaces are processed. The relationship between the air characteristics and the characteristics of the sintered body and the oxygen partial pressure in the firing atmosphere was examined. The firing was performed in a mixed gas atmosphere (1 atm) of oxygen gas and nitrogen gas, and the oxygen partial pressure in the firing atmosphere was controlled by controlling the flow rate of both gases. The heating rate and the cooling rate during firing were 5 ° CZ minutes, the firing temperature was 122 ° C, and the time (stable time) for maintaining the firing temperature was 1 hour.

Table 1-2 shows the compositions (analytical values by fluorescent X-ray) of the sintered magnets whose magnetic properties were evaluated. The composition shown in Table 1-2 is a value for a measurement sample obtained by firing the molding slurry in air at 100 ° C. for 1 hour.

Table 1-1

Content (mol./

SrO BaO CaO La ₂ 0 ₃ Fe ₂ 0 ₃ CoO MnO A1 ₂ 0 ₃ Cr ₂ 0 ₃ Si0 ₂

Calcined material 12.69 0.06 0.17 85.89 0.63 0.13 0.03 0.40

Table 1-2

Content (mol ⁰ /.) {A + R- (Fe + M) / 12} Composition SrO BaO CaO La ₂ 0 ₃ Fe ₂ 0 ₃ CoO MnO A1 ₂ 0 ₃ Cr ₂ 0 ₃ Si0 ₂ / Si Example 1 -1 10.11 0.12 2.66 1.28 81.09 2.61 0.62 0.08 0.10 1.33 1.23

Example 1-2 10.51 0.12 2.53 1.33 80.24 2.69 0.61 0.09 0.10 1.78 1.20

Comparative Example 1-1 10.64 0.12 2.30 1.35 81.06 2.72 0.62 0.08 0.09 1.91 Comparative Example 1-2 11.21 0.11 1.47 1.42 81.05 2.88 0.60 0.09 0.10 1.07 * 1.68

Comparative Example 1-3 11.78 0.12 0.49 1.49 80.37 3.05 0.59 0.09 0.10 1.92 0.85 * Comparative Example 1-4 10.52 0.12 3.02 1.33 80.12 2.72 0.61 0.09 0.09 1.38 1.93 *

: Out of limited range

J

*

The magnet having the composition shown in Table 1 one 2, in FIG. 1, the firing time of the oxygen partial pressure p 0 ₂ and magnetic properties {coercive force (HcJ), residual magnetic flux density (B r) and squareness (Hk / HcJ)} The relationship between and is shown.

As shown in FIG. 1, the composition of the example of the present invention, that is, the composition whose atomic ratio {A + R_ (F e + M) / \ 2} / S i and S i O ₂ content are within the above-mentioned limited range 內In this case, even when firing in an atmosphere with an oxygen partial pressure of 0.05 atm, magnetic properties equivalent to or better than those when firing in air were obtained, and firing was performed in an atmosphere with an oxygen partial pressure of 0.01 atm. In this case, almost no decrease in magnetic properties is observed. Specifically, when the oxygen partial pressure is reduced from 0.20 atm to 0.01 atm, the composition of the comparative example, that is, (A + R—

(F e + M) / 1 2} // S in one of i and S i 0 ₂ content deviates from the limited range composition observed decrease above about 4000e, in particular, the oxygen partial pressure 0 In the composition of the comparative example in which the coercive force exceeding the composition of the example was obtained at 20 atm, the coercive force was reduced by as much as about 15,000 e due to the decrease in the oxygen partial pressure. On the other hand, in the composition of the example, the decrease in coercive force was within about 1500 e or less, and no decrease in the residual magnetic flux density was observed at this time. From these results, the effect of the present invention is clear. Example 2

A sintered magnet having the composition shown in Table 2-2 (analytical value by fluorescent X-ray analysis) was produced in the same manner as in Example 1 except that the calcined material having the composition shown in Table 2-1 was used. However, during firing, the oxygen partial pressure in the atmosphere was fixed at 0.05 atm and the firing temperature was varied. Table 2-

: Out of limited range

Fig. 2 shows the relationship between firing temperature and magnetic properties for magnets with the compositions shown in Table 2-2.

As shown in FIG. 2, in the composition of the comparative example, the coercive force varied greatly when the firing temperature was changed, whereas the composition of the example, that is, the atomic ratio {A + R— (F e + M) } In the composition in which the content of / S i and S i〇 ₂ is within the above-mentioned limited range, the composition of the comparative example, that is, {A + R— (F e + M) / 1 2} / S i and S i O ₂ Coercive force fluctuation is smaller than a composition in which one of the amounts is out of the above-mentioned limited range.

Example 3

A sintered magnet having the composition shown in Table 3-2 (analytical value by fluorescent X-ray analysis) was produced in the same manner as in Example 1 except that the calcined material having the composition shown in Table 3-1 was used. However, at the time of firing, the oxygen partial pressure in the atmosphere was fixed at 0.05 atm, and the firing temperature was fixed at 122 ° C. In addition,

Example 3 A—1,

Example 3 A—2,

Comparative Example 3 A

Group (hereinafter referred to as group A),

Example 3 B—1,

Example 3 B-2,

Comparative Example 3 B

(Hereinafter referred to as Group B), and

Example 3 C-1,

Example 3 C-2,

Comparative Example 3 C

In each of the groups consisting of (hereinafter group C), the elements other than Ca are almost equal, and by changing the amount of Ca, the amount of A and (A + R— (F e + M) / 12} changed / S i ₍

Table 3-〗

Table 3-2

The content (mol%) {A + R- (Fe + M) / 12} composition _{_{SrO BaO CaO La 2 0 3 Fe}} 2 0 3 CoO MnO A1 2 0 3 Cr 2 0 3 Si0 2 / Si Example 3A-1 9.99 0.12 3.25 1.26 80.35 2.56 0.61 0.08 0.12 1.66 1.32 Example 3A-2 9.94 0.12 3.83 1.26 79.83 2.56 0.61 0.08 0.11 1.66 1.69 Comparative example 3A 9.89 0.11 4.40 1.26 79.36 2.56 0.60 0.08 0.10 1.64 2.07 * Example 3B-1 11.10 0.11 1.71 1.40 80.17 2.87 0.59 0.09 0.10 1.86 1.10 Example 3B-2 11.04 0.11 2.33 1.39 79.66 2.87 0.59 0.08 0.09 1.84 1.45 Comparative example 3B 11.16 0.11 1.06 1.41 80.73 2.88 0.60 0.09 0.11 1.85 0.74 * Example 3C-1 10.58 0.12 2.07 1.35 80.94 2.73 0.62 0.09 0.10 1.40 1.19 Example 3C-2 10.56 0.12 2.55 1.34 80.55 2.72 0.61 0.08 0.09 1.38 1.58 Comparative example 3C 10.52 0.12 3.02 1.33 80.12 2.72 0.61 0.09 0.09 1.38 1.93 *

: Out of limited range

Fig. 3 shows the relationship between the atomic ratio {A + R— (Fe + M) / 12} / Si and the magnetic properties of the magnets with the composition shown in Table 3-2. Figure 4 shows the relationship.

In FIG. 3, a comparison of the magnetic properties in each of the groups A, B, and C shows that the coercive force is significantly increased when the atomic ratio is within the range limited by the present invention. That is, it can be seen that the present invention provides a high coercive force under a low oxygen partial pressure. On the other hand, paying attention to the coercive force graph of FIG. 4, it can be seen that the amount of CaO in Comparative Example 3C is smaller than the composition of the Example in Group A and larger than that in Group B. That is, it can be seen that the CaO amount of Comparative Example 3C was neither excessive nor excessive as compared with the compositions of the other Examples.

Conventionally, in the Sr ferrite magnet, it was thought that the content of CaO as an additive had a large effect on the coercive force. It is clear that the coercive force changes significantly depending on {A + R— (Fe + M) 12} ZSi, not on the content.

When a part of La was replaced with Bi in the Sr ferrite produced in each of the above examples, it was found that the calcination temperature could be lowered by adding Bi. That is, the calcination temperature at which the best properties were obtained was shifted to the lower temperature side, and the coercive force was hardly degraded. Further, when a sintered magnet was manufactured with a composition in which part of La was replaced with another rare earth element, the same effect as in each of the above examples was observed.

In each of the above embodiments, lanthanum carbonate and cobalt oxide were added to the calcined material as post-additives. However, even when the same amount was added to the starting material without post-addition, the same effect as in each of the above-mentioned embodiments was obtained. Was observed. However, the effect was slightly lower than in the case of later addition.

The Curie temperature of the sintered magnet produced in each of the above examples was measured according to the following procedure. First, a sintered magnet with a diameter of 5 mm and a height of 6. The sample was processed into a 5 mra column and used as a measurement sample. Next, the sample was magnetized at 25 ° C by applying a magnetic field of about 2 O kOe in the c-axis direction of the sample using a VSM. Next, with the VSM magnetic field generation current set to zero (however, a magnetic field of about 500e is generated due to the residual magnetization of the magnetic pole), the remanent magnetization in the c-axis direction of the sample and the sample temperature are measured simultaneously, The σ-T curve as shown in Fig. 6 was obtained. The temperature of the sample was raised by a heater arranged around the sample. The heating rate was about 10 ° CZ minutes. From the obtained σ-Τ curve, the Curie temperature was determined by the method described above. As a result, the magnets manufactured in each of the above examples have two Curie temperatures, the curie temperature on the low temperature side is between 430 ° C and 450 ° C, and the Curie temperature on the high temperature side is 450 ° C. It was found to be between ~ 460 ° C. The ratio (σ 1 σ RT) of the magnetization (σ ΐ) at the Curie temperature on the low temperature side to the magnetization RT at 25 ° C was 2 to 10%. When each sample was analyzed by X-ray diffraction, it was found that each sample was a Μ type ferrite single phase.

Reference example

Ferrite sintered magnets having the compositions shown in Table 4 below were produced. The Sr fluorite magnet containing La and Co was produced by the above-described addition method. The firing was performed in a mixed gas atmosphere of oxygen gas and nitrogen gas (1 atm), and the oxygen concentration in the firing atmosphere was controlled by controlling the flow rates of both gases. Figure 5 shows the oxygen concentration in the firing atmosphere. The coercive force (HcJ) was measured for these sintered magnets. Fig. 5 shows the results. Table 4

Content (mol%)

SrO BaO CaO La ₂ 0 ₃ CoO MnO Α1 ₂ 0 _Λ Cr ₂ 0, Si0 ₂

LaCo-containing Sr ferrite 11.0 0.1 1.5 1.2 81.7 2.3 0.6 One-1.6

Sr ferrite 13.7 0.1 1.6 82.5 0.6 one 1.5

From Fig. 5, it can be seen that the Sr ferrite magnet containing La and Co significantly changes the coercive force depending on the oxygen concentration in the firing atmosphere, but contains both La and Co. It can be seen that the dependence of the coercive force on the oxygen concentration in the firing atmosphere is low in the conventional Sr ferrite magnet that does not. The LaCo-containing magnet shown in FIG. 5 has an atomic ratio of {A + R— (Fe + M) NO12} / Si force S, which is outside the range limited by the present invention.

From the results shown in FIG. 5, it can be seen from both the results of the above examples that the amount of Si and the atomic ratio {A + R— (F e + M) / 12} / Si are controlled by the element R It is evident that the specific effect is exhibited only in the ferrite magnet containing the element M.

Claims

The scope of the claims

1. Let A contain at least one element selected from Sr, Ba, Ca and Pb, and R be at least one element selected from rare earth elements (including Y) and Bi. When at least one element selected from Co, Mn, Al, Cr, Ni, and Zn is M, the metal element contains A, R, Fe, M, and Si. when these metal elements was determined the content of each metal oxide in terms of oxides, the content of 5 1_Rei ₂ is 1.3 to 2.0 mol%, and,

Atomic ratio {A + R— (F e + M) / 1 2} / S i

Is 1.:!~1.9

Ferrite magnet with hexagonal ferrite as the main phase.

2. The ratio of the total of each of A,, Fe and M to the total amount of metal elements is A ::! To 1 3 atom ^_0/0,

R: 0.05 to 10 atoms ⁰ / o,

F e: 80-95 atoms ⁰ /. ,

M: 0 .:! ~ 5 atoms ⁰ /.

The ferrite magnet according to claim 1, wherein the ferrite magnet is:

3. Claims having at least two different Curie temperatures, wherein these Curie temperatures are in the range of 400 ° C to 480 ° C and whose Curie temperatures are more than 5 ° C from each other The ferrite magnet of paragraph 1 or 2.

4. A method for producing a ferrite magnet according to any one of claims 1 to 3, wherein

5. In at least a part of the firing process, the oxygen partial pressure in the atmosphere is 0.15 5. The method of claim 4, wherein the pressure is not more than the pressure.

6. A method for producing a ferrite magnet according to any one of claims 1 to 3, wherein

7. At least one compound containing at least one of the magnet constituent elements is added to the calcined material or particles each having a hexagonal ferrite as a main phase, and then molded and sintered. Item 7. The method for producing a fusible magnet according to any one of Items 6 to 6.

8. The method for manufacturing a ferrite magnet according to claim 7, wherein a part of the magnet constituent elements is one or more elements selected from the element R and the element M.