JP7111150B2 - Calcined ferrite body, sintered ferrite magnet and method for producing the same - Google Patents

Description

The present invention relates to a calcined ferrite body, a sintered ferrite magnet, and a method for producing the same.

Although the maximum energy product of ferrite sintered magnets is only 1/10 that of rare earth sintered magnets (e.g., NdFeB sintered magnets), their main raw material is inexpensive iron oxide, making them excellent in terms of cost performance. It has the advantage of being extremely stable. Therefore, it is used in a variety of applications such as various motors and speakers, and its global production weight is still the largest among magnetic materials.

A typical sintered ferrite magnet is Sr ferrite having a _{magnetoplumbite} structure, and its basic composition is represented by _SrFe12O19 . In the latter half of the 1990s, Sr-La-Co ferrite sintered magnets in which Sr ²⁺ in SrFe ₁₂ O ₁₉ was partly replaced with La ³⁺ and Fe ³⁺ was partly replaced with Co ²⁺ were put into practical use. The magnetic properties of the magnet are greatly improved. In 2007, Ca-La-Co ferrite sintered magnets with further improved magnetic properties were put to practical use.

In both the Sr--La--Co system ferrite sintered magnets and the Ca--La--Co system ferrite sintered magnets described above, Co is indispensable for obtaining high magnetic properties. The Sr-La-Co system ferrite sintered magnet contains Co in an atomic ratio of about 0.2, and the Ca-La-Co system ferrite sintered magnet contains Co in an atomic ratio of about 0.3. The price of Co (Co oxide) is ten to several ten times that of iron oxide, which is the main raw material of sintered ferrite magnets. Therefore, the Ca--La--Co system ferrite sintered magnet inevitably increases the raw material cost compared to the Sr--La--Co system ferrite sintered magnet. The most important feature of sintered ferrite magnets is that they are inexpensive, so even if they have excellent magnetic properties, they will not be accepted in the market if the price is high. Therefore, worldwide demand for Sr-La-Co ferrite sintered magnets is still high.

In recent years, the price of Co has skyrocketed as demand for Li-ion batteries has increased due to an increase in the supply of electric vehicles. In the aftermath, even Sr-La-Co ferrite sintered magnets, which have excellent cost performance, are in a situation where it is difficult to maintain product prices. Against this background, how to reduce the amount of Co used while maintaining the magnetic properties is an urgent issue.

Although it is not intended to reduce the amount of Co, for example, in a Sr-La-Co ferrite sintered magnet, by substituting a part of Co with Zn, the residual magnetic flux density (hereinafter referred to as "B _r ") is increased. It is known to improve (JP-A-11-154604, etc.).

However, when part of Co is replaced with Zn in the _Sr -La-Co ferrite sintered magnet, the improvement in Br is not so large, but the coercive force (hereinafter referred to as " _HcJ ") is significantly reduced. However, it has not yet been put to practical use.

Therefore, an object of the present invention is to have a high Br and a small decrease in _{HcJ (higher HcJ than} in a Sr-La-Co ferrite sintered magnet in which a part of Co is replaced with Zn), Moreover, it is another object of the present invention to provide a sintered ferrite magnet in which the amount of Co used is reduced by 25% or more compared to a conventional Sr-La-Co system ferrite sintered magnet (containing Co in an atomic ratio of about 0.2).

That is, the ferrite calcined body of the present invention is
General formula showing the atomic ratio of the metal elements Ca, R, Fe, Co and Zn (where R is at least one rare earth element and essentially contains La): Ca _1-x R _x Fe _{2n- In yz} Co _y Zn _z ,
The x, y and z, and n (where 2n is the molar ratio and is represented by 2n = (Fe + Co + Zn) / (Ca + R)) are
0.4≤x≤0.6,
0 < y < 0.15,
0.1≤z≤0.4,
0.2≤(y+z)≤0.4, and
4≤n≤6
satisfy.

The y preferably satisfies 0<y≦0.13.

The 1-x, x, y and z preferably satisfy 1-x≧x when 0.2≦(y+z)≦0.3 and 1-x<x when 0.3<(y+z)≦0.4. .

The ferrite sintered magnet of the present invention is
General formula showing the atomic ratio of the metal elements Ca, R, Fe, Co and Zn (where R is at least one rare earth element and essentially contains La): Ca _1-x R _x Fe _{2n- In yz} Co _y Zn _z ,
The x, y and z, and n (where 2n is the molar ratio and is represented by 2n = (Fe + Co + Zn) / (Ca + R)) are
0.3≤x≤0.6,
0 < y < 0.15,
0.05≤z≤0.4,
0.15≤(y+z)≤0.4, and
3.4≤n≤6
satisfy.

The sintered ferrite magnet of the present invention preferably further contains SiO ₂ in an amount of 1.5% by mass or less.

The method for producing a sintered ferrite magnet of the present invention comprises:
General formula showing the atomic ratio of the metal elements Ca, R, Fe, Co and Zn (where R is at least one rare earth element and essentially contains La): Ca _1-x R _x Fe _{2n- In yz} Co _y Zn _z ,
The x, y and z, and n (where 2n is the molar ratio and is represented by 2n = (Fe + Co + Zn) / (Ca + R)) are
0.4≤x≤0.6,
0 < y < 0.15,
0.1≤z≤0.4,
0.2≤(y+z)≤0.4, and
4≤n≤6
A raw material powder mixing step for obtaining a mixed raw material powder by mixing raw material powders satisfying
a calcining step of calcining the mixed raw material powder to obtain a calcined body;
a pulverizing step of pulverizing the calcined body to obtain powder of the calcined body;
It includes a molding step of molding the powder of the calcined body to obtain a molded body, and a firing step of firing the molded body to obtain a sintered body.

In the method for producing a sintered ferrite magnet of the present invention, after the calcining step and before the forming step, 1.5% by mass or less of SiO ₂ is added to 100% by mass of the calcined body or powder of the calcined body. Preferably, further steps are included.

In the method for producing a sintered ferrite magnet of the present invention, after the calcining step and before the forming step, CaCO ₃ is added in an amount of 1.5% by mass or less in terms of CaO with respect to 100% by mass of the calcined body or the powder of the calcined body. preferably further comprising the step of adding

In the method for producing a sintered ferrite magnet of the present invention, the atomic ratio y of the calcined body preferably satisfies 0<y≦0.13.

In the method for producing a sintered ferrite magnet of the present invention, the atomic ratios 1-x, x, y and z of the calcined body satisfy 1-x≧x when 0.2≦(y+z)≦0.3 and 0.3< It is preferable to satisfy 1-x<x when (y+z)≤0.4.

According to the present invention, it has a high Br, a small decrease in _{HcJ (higher HcJ than} in a Sr-La-Co ferrite sintered magnet in which a part of Co is replaced with Zn), and It is possible to provide a ferrite sintered magnet in which the amount of Co used is reduced by 25% or more compared to conventional Sr-La-Co system ferrite sintered magnets (containing Co at an atomic ratio of about 0.2).

1. Ferrite calcined body The ferrite calcined body of the present invention is
General formula showing the atomic ratio of the metal elements Ca, R, Fe, Co and Zn (where R is at least one rare earth element and essentially contains La): Ca _1-x R _x Fe _{2n- In yz} Co _y Zn _z ,
The x, y and z, and n (where 2n is the molar ratio and is represented by 2n = (Fe + Co + Zn) / (Ca + R)) are
0.4≤x≤0.6,
0 < y < 0.15,
0.1≤z≤0.4,
0.2≤(y+z)≤0.4, and
4≤n≤6
satisfy.

In the ferrite calcined body of the present invention, the atomic ratio x (content of R) is 0.4≦x≦0.6. If x is less than 0.4 or more than 0.6, a high _Br cannot be obtained. R is at least one rare earth element and an element essentially containing La. The content of rare earth elements other than La is preferably 50% or less of the total amount of R in terms of molar ratio.

The atomic ratio y (content of Co) is 0<y<0.15. If y is 0.15 or more, the effect of reducing the amount of Co used cannot be obtained. If y is 0 (does not contain), the decrease in H _cJ becomes large, which is not preferable. The atomic ratio y is preferably 0<y≦0.13, more preferably 0.08<y≦0.13, and even more preferably 0.10≦y≦0.13.

The atomic ratio z (content of Zn) is 0.1≦z≦0.4. A high _Br cannot be obtained when z is less than 0.1 or exceeds 0.4.

The atomic ratios y and z satisfy the relationship 0.2≤(y+z)≤0.4. If (y+z) is less than 0.2 or more than 0.4, high _Br cannot be obtained. Further, the atomic ratios 1-x and x more preferably satisfy 1-x≧x when 0.2≦(y+z)≦0.3 and 1-x<x when 0.3<(y+z)≦0.4.

In the above general formula, 2n is a molar ratio, expressed as 2n=(Fe+Co+Zn)/(Ca+R). n is 4≦n≦6. If n is less than 4 or more than 6, high B _r cannot be obtained.

Although the general formula is expressed by the atomic ratio of metal elements, the composition containing oxygen ( _O ) is represented by the general formula _{: Ca1} - _{xRxFe2n - yzCoyZnzOα} . The number of moles α of oxygen is basically α=19, but varies depending on the valences of Fe and Co, the values of x, y and z, and n. In addition, the ratio of oxygen to the metal element changes due to oxygen vacancies (vacancy) when firing in a reducing atmosphere, changes in the valence of Fe in the ferrite phase, changes in the valence of Co, and the like. Therefore, the actual number of moles α of oxygen may deviate from 19. Therefore, in the present invention, the composition is represented by the atomic ratio of the metal elements, which is the easiest to specify.

The main phase constituting the ferrite calcined body of the present invention is a compound phase (ferrite phase) having a hexagonal magnetoplumbite (M-type) structure. In general, magnetic materials, particularly sintered magnets, are composed of multiple compounds, and the compound that determines the properties (physical properties, magnetic properties, etc.) of the magnetic material is defined as the "main phase".

“Hexagonal magnetoplumbite (M type) structure” means that X It means that a line diffraction pattern is mainly observed.

An example of the method for producing the sintered ferrite magnet of the present invention, including the method for producing the ferrite calcined body of the present invention described above, will be described below.

2. Manufacturing method of ferrite sintered magnet As raw material powder, compounds such as oxides, carbonates, hydroxides, nitrates, and chlorides of respective metals can be used regardless of valence. A solution obtained by dissolving the raw material powder may be used. Ca compounds include carbonates, oxides and chlorides of Ca. Examples of La compounds include oxides such as _{La2O3, hydroxides such as La(OH)3 , and} carbonates such as _{La2 ( CO3} ) _3.8H2O . Examples of Fe compounds include iron oxide, iron hydroxide, iron chloride, and millscale. Co compounds include oxides such as CoO and Co3O4 _, hydroxides such as CoOOH and Co ₍ OH) ₂ , carbonates such as _CoCO3 , and _m2CoCO3 · _{m3Co (} OH) ₂ . · Basic carbonates such as m ₄ H ₂ O (m ₂ , m ₃ and m ₄ are positive numbers). A compound of Zn includes ZnO .

A compound containing B (boron), such as B ₂ O ₃ and H ₃ BO ₃ , may be added up to about 1% by mass, if necessary, in order to promote the reaction during calcination. Addition of H ₃ BO ₃ is particularly effective in improving magnetic properties. The amount of H ₃ BO ₃ added is preferably 0.3% by mass or less, most preferably about 0.1% by mass. H ₃ BO ₃ also has the effect of controlling the shape and size of crystal grains during firing, so it may be added after calcination (before pulverization or before calcination). may be added.

Raw material powders satisfying the components and composition of the ferrite calcined body of the present invention are mixed to form a mixed raw material powder. Blending and mixing of raw material powders may be carried out by either a wet method or a dry method. Stirring with a medium such as a steel ball allows the raw material powder to be mixed more uniformly. In the wet method, it is preferable to use water as a dispersion medium. A known dispersant such as ammonium polycarboxylate and calcium gluconate may be used for the purpose of enhancing the dispersibility of the raw material powder. The mixed raw material slurry may be calcined as it is, or may be calcined after dewatering the raw material slurry.

The mixed raw material powder obtained by dry-mixing or wet-mixing is heated using an electric furnace, a gas furnace, etc., and a ferrite compound with a hexagonal magnetoplumbite (M-type) structure is formed by a solid phase reaction. Form. This process is called "calcination", and the resulting compound is called "calcined body".

In the calcining step, a solid phase reaction that forms a ferrite phase progresses as the temperature rises. If the calcining temperature is less than 1100°C, unreacted hematite (iron oxide) remains, resulting in poor magnetic properties. On the other hand, if the calcining temperature exceeds 1450° C., the crystal grains grow too much, which may require a long time for pulverization in the pulverization step. Therefore, the calcination temperature is preferably 1100°C to 1450°C. The calcining time is preferably 0.5 to 5 hours. It is preferable to coarsely pulverize the calcined body after calcination with a hammer mill or the like.

The calcined ferrite body of the present invention can be obtained through the steps described above. Next, the method for producing the sintered ferrite magnet of the present invention will be explained.

The calcined body is pulverized (pulverized) by a vibration mill, a jet mill, a ball mill, an attritor, or the like to obtain calcined powder (finely pulverized powder). The average particle size of the calcined powder is preferably about 0.4 μm to 0.8 μm. In the present invention, the value measured by the air permeation method using a powder specific surface area measuring device (for example, SS-100 manufactured by Shimadzu Corporation) is referred to as the average particle size of the powder (average particle size). The pulverization step may be either dry pulverization or wet pulverization, or both may be combined. In the case of wet pulverization, water and/or a non-aqueous solvent (organic solvent such as acetone, ethanol, xylene, etc.) is used as a dispersion medium. Typically, a slurry containing water (dispersion medium) and a calcined body is produced. A known dispersant and/or surfactant may be added to the slurry at a solid content ratio of 0.2 to 2% by mass. After wet grinding, the slurry may be concentrated.

In the molding step, the slurry after the pulverization step is press-molded in a magnetic field or in a non-magnetic field while removing the dispersion medium. By press-molding in a magnetic field, the crystal orientation of the powder particles can be aligned (orientated), and the magnetic properties can be dramatically improved. Furthermore, in order to improve orientation, 0.1 to 1 mass % each of a dispersant and a lubricant may be added to the slurry before molding. Also, the slurry may be concentrated before molding, if necessary. Concentration is preferably carried out by centrifugation, filter press or the like.

A sintering aid may be added to the calcined body or powder of the calcined body (coarsely pulverized powder or finely pulverized powder) after the calcining step and before the molding step. SiO ₂ and CaCO ₃ are preferred as sintering aids. The sintered ferrite magnet of the present invention belongs to the Ca-La-Co system sintered ferrite magnet, as is apparent from its composition. Since Ca-La-Co ferrite sintered magnets contain Ca as the main phase component, SiO ₂ and CaCO ₃ are not sintered like conventional Sr-La-Co ferrite sintered magnets. A liquid phase is formed and can be sintered without the addition of auxiliary agents. In other words, the sintered ferrite magnet of the present invention can be produced without adding SiO ₂ and CaCO ₃ which mainly form grain boundary phases in the sintered ferrite magnet. However, in order to suppress the decrease in _HcJ , SiO ₂ and CaCO ₃ may be added in the amounts shown below.

The amount of SiO ₂ to be added is preferably 1.5% by mass or less with respect to 100% by mass of the calcined body to be added or the powder of the calcined body. The amount of CaCO ₃ to be added is preferably 1.5% by mass or less in terms of CaO with respect to 100% by mass of the calcined body or powder of the calcined body to be added. The sintering aid is added, for example, by adding it to the calcined body obtained by the calcining process and then performing the crushing process, adding it during the crushing process, or adding the powder of the calcined body after the crushing process ( It is possible to adopt a method such as adding to a finely pulverized powder) and performing a molding step after mixing. As a sintering aid, in addition to SiO ₂ and CaCO ₃ , Cr ₂ O ₃ , Al ₂ O ₃ and the like may be added. The amount of each of these added may be 1% by mass or less.

In the present invention, the amount of CaCO ₃ added is expressed in terms of CaO. The added amount of CaCO ₃ can be obtained from the added amount in terms of CaO by the formula: (molecular weight of CaCO ₃ × added amount in terms of CaO)/molecular weight of CaO. For example, when adding 0.5% by mass of _CaCO3 in terms of CaO, the amount is {(40.08 [atomic weight of Ca] + 12.01 [atomic weight of C] + 48.00 [atomic weight of O x 3] = 100.09 [ _CaCO3 molecular weight]) × 0.5 mass% [addition amount in terms of CaO]} / (40.08 [atomic weight of Ca] + 16.00 [atomic weight of O] = 56.08 [molecular weight of CaO]) = 0.892 mass% [addition of _CaCO3 amount].

A compact obtained by press molding is degreased as necessary, and then fired (sintered). Firing is performed using an electric furnace, a gas furnace, or the like. Firing is preferably carried out in an atmosphere with an oxygen concentration of 10% by volume or more. More preferably 20% by volume or more, most preferably 100% by volume. The firing temperature is preferably 1150°C to 1250°C. The firing time is preferably from 0 hours (no holding at the firing temperature) to 2 hours.

After the firing process, a sintered ferrite magnet is finally manufactured through known manufacturing processes such as a working process, a cleaning process, and an inspection process.

3. Ferrite sintered magnet As described above, the ferrite calcined body of the present invention can be sintered by generating a liquid phase without adding a sintering aid such as _SiO2 or _CaCO3 . A ferrite sintered magnet of the present invention can be obtained. At this time, the components and composition of the calcined ferrite body and the components and composition of the sintered ferrite magnet are basically the same (inclusion of impurities in the manufacturing process is not considered).

On the other hand, when a sintering aid is added, especially when the Ca component (e.g. CaCO ₃ ), which is also the main component of the ferrite calcined body, is added as a sintering aid, the Ca component of the sintered ferrite magnet as a whole increases. Therefore, other elements are relatively decreased. For example, when using the ferrite calcined body of the present invention and adding 1.5% by mass of _CaCO3 in terms of CaO as a sintering aid, the most variable case is 0.4 ≤ x ≤ 0.6 (calcined body) is 0.3 ≤ x ≤ 0.6 (sintered magnet), 0.1 ≤ z ≤ 0.4 (calcined body), 0.05 ≤ z ≤ 0.4 (sintered magnet), 0.2 ≤ (y + z) ≤ 0.4 (calcined body), 0.15 ≤ (y + z) ≤ 0.4 (sintered magnet) and 4 ≤ n ≤ 6 (calcined body) become 3.4 ≤ n ≤ 6 (sintered magnet).

Therefore, the ferrite sintered magnet of the present invention is
General formula showing the atomic ratio of the metal elements Ca, R, Fe, Co and Zn (where R is at least one rare earth element and essentially contains La): Ca _1-x R _x Fe _{2n- In yz} Co _y Zn _z ,
The x, y and z, and n (where 2n is the molar ratio and is represented by 2n = (Fe + Co + Zn) / (Ca + R)) are
0.3≤x≤0.6,
0 < y < 0.15,
0.05≤z≤0.4,
0.15≤(y+z)≤0.4, and
3.4≤n≤6
will be satisfied.

The composition of the sintered ferrite magnet of the present invention when oxygen (O) is included, the main phase constituting the sintered ferrite magnet, the definition of the hexagonal magnetoplumbite (M type) structure, etc. It is the same as the ferrite calcined body. Further, as described above, although the range varies from that of the ferrite calcined body, the reasons for limiting the atomic ratios x, y, and z, and the reasons for limiting n are the same as those for the ferrite calcined body, so the explanation is omitted.

As described above, in the method for producing a sintered ferrite magnet of the present invention, SiO ₂ as a sintering aid may be added in an amount of 1.5% by mass or less with respect to 100% by mass of the calcined body or powder of the calcined body. SiO ₂ added as a sintering aid becomes a liquid phase component during firing (sintering), and exists as one component of the grain boundary phase in the sintered ferrite magnet. Therefore, when SiO ₂ is added in the above amount as a sintering aid, the resulting sintered ferrite magnet contains 1.5% by mass or less of SiO ₂ . At this time, the content of each element represented by the general formula: Ca _1-x R _x Fe _2n-yz Co _y Zn _z is relatively reduced due to the content of SiO ₂ , but x , y, z, n, etc. basically do not change. The content of SiO ₂ is determined from the composition (% by mass) of Ca, R, Fe, Co, Zn, and Si in the results of component analysis of the sintered ferrite magnet (for example, the results using an ICP emission spectrometer). ₃ , La(OH) ₃ , Fe ₂ O ₃ , Co ₃ O ₄ , ZnO and SiO ₂ are converted into masses, and the content ratio (% by mass) with respect to the total 100 % by mass.

The present invention will be explained in more detail by examples, but the present invention is not limited to them.

Experimental example 1
As experimental examples based on the present invention, in the general formula Ca _1-x La _x Fe _2n-yz Co _y Zn _z , the atomic ratios of 1-x, x, y, z and CaCO ₃ powder, La(OH) ₃ powder, Fe ₂ O ₃ powder, Co ₃ O ₄ powder, and ZnO powder were weighed according to a predetermined composition so that 2n was obtained. After 0.1% by mass of H ₃ BO ₃ powder was added, each mixture was mixed in a wet ball mill for 4 hours, dried, and granulated to obtain 18 kinds of mixed raw material powders.

Further, as a comparative example, in the general formula _Sr1 - _{xLaxFe2n - yzCoyZnz} , the atomic ratios of Sr, La, Co, and Zn and _n are the atomic ratios shown in Sample Nos. 19 and 20 in Table 1. SrCO ₃ powder, La(OH) ₃ powder, Fe ₂ O ₃ powder, Co ₃ O ₄ powder, and ZnO powder were weighed with a predetermined composition so that H After 0.1% by mass of _3BO3 powder was added _, the mixture was mixed in a wet ball mill for 4 hours, dried, and granulated to obtain two kinds of mixed raw material powders.

A total of 20 types of mixed raw material powders thus obtained were calcined in air at the calcining temperature shown in Table 1 for 3 hours to obtain 20 types of calcined bodies.

Each of the obtained calcined bodies was coarsely pulverized with a small mill to obtain coarsely pulverized powder of 20 types of calcined bodies. To 100% by mass of the coarsely pulverized powder of each calcined body obtained, CaCO ₃ (addition amount is calculated as CaO) and SiO ₂ shown in Table 1 are added, and a wet ball mill using water as a dispersion medium is used. (measured by an air permeation method using a powder specific surface area measuring device (SS-100 manufactured by Shimadzu Corporation)) to obtain 20 kinds of finely pulverized slurries.

A magnetic field of about 1 T is applied to each finely pulverized slurry obtained by the pulverization process using a parallel magnetic field forming machine (vertical magnetic field forming machine) in which the direction of pressure and the direction of the magnetic field are parallel while removing the dispersion medium. 20 types of compacts were obtained by compacting at a pressure of about 2.4 MPa.

Each molded body obtained was inserted into a sintering furnace and fired in air at the firing temperature shown in Table 1 for 1 hour to obtain 20 types of sintered ferrite magnets. Table 1 shows the measurement results of B _r , H _cJ and H _k /H _cJ of the obtained sintered ferrite magnet. In Table 1, samples No. 1 to 14 not marked with * next to the sample No. are experimental examples based on the present invention, and samples No. 15 to 18 marked with * are experiments that do not satisfy the present invention. Sample Nos. 19 and 20 marked with * are experimental examples (comparative examples) in which a part of Co was replaced with Zn in conventional Sr--La--Co based sintered magnets. In Table 1, H _k is 0.95×J _r (J _r is remanent magnetization, J _r = B _r ) in the second quadrant of the J (magnetization magnitude)-H (magnetic field strength) curve. is the value of H at the position where the value of The same applies to Experimental Example 2 below.

The atomic ratio in Table 1 indicates the atomic ratio (blending composition) when the raw material powder was blended. The atomic ratio (composition of the sintered magnet) in the sintered body (ferrite sintered magnet) after firing is based on the atomic ratio at the time of blending, and the additives (H ₃ BO ₃ , etc.) added before the calcination process and the amount of sintering aids (CaCO ₃ and SiO ₂ ) added after the calcining process and before the forming process. is basically the same as the result of analysis by an ICP emission spectrometer (for example, ICPV-1017 manufactured by Shimadzu Corporation). The same applies to Experimental Example 2 below.

*比較例

表1（続き）

*比較例
table 1

*Comparative example

Table 1 (continued)

*Comparative example

As shown in Table 1, compared to Samples Nos. 19 and 20, which are experimental examples (comparative examples) in which part of Co was replaced with Zn in Sr-La-Co sintered magnets, the magnets contained the same amount of Co. Sample No. 1 and sample No. 2 containing the same amount of Zn have high _{Br and high HcJ ,} and are comparable to conventional Sr-La-Co sintered magnets (with an atomic ratio of Co of about 0.2). containing), the amount of Co used can be reduced by 25% or more. That is, the ferrite sintered magnet based on the present invention ( Ca—La—Co based sintered magnets) have higher _{Br and higher H cJ than} conventional Sr—La—Co based sintered magnets.

Moreover, as is clear from Table 1, the magnetic properties of sample No. 15 (y+z=0.1), which does not satisfy 0.2≦(y+z)≦0.4, are greatly deteriorated. Furthermore, by satisfying 1-x≧x when 0.2≦(y+z)≦0.3 and 1-x<x when 0.3<(y+z)≦0.4, higher magnetic properties can be obtained. When 0.2≦(y+z)≦0.3, sample No. 11 (y+z=0.3, 1-x<x), which does not satisfy 1-x≧x, shows a tendency for the magnetic properties to deteriorate. Further, it can be seen that samples Nos. 16 to 18, which do not satisfy 0<y<0.15, that is, y=0 (does not contain Co), tend to exhibit a greater decrease in _HcJ .

Experimental example 2
As experimental examples based on the present invention, in the general formula Ca _1-x La _x Fe _2n-yz Co _y Zn _z , the atomic ratios of 1-x, x, y, z and CaCO ₃ powder, La(OH) ₃ powder, Fe ₂ O ₃ powder, Co ₃ O ₄ powder, and ZnO powder were weighed according to a predetermined composition so that 2n was obtained. After 0.1% by mass of H ₃ BO ₃ powder was added, each mixture was mixed in a wet ball mill for 4 hours, dried, and granulated to obtain 8 kinds of mixed raw material powders.

As a comparative example, in the general formula _Sr1 - _{xLaxFe2n - yzCoyZnz} , the atomic ratios of Sr, La, Co, and Zn and _n are the atomic ratios shown in Sample No. 29 in Table 2. SrCO ₃ powder _, La(OH) ₃ powder, Fe ₂ O ₃ powder, Co ₃ O ₄ powder and ZnO powder were weighed in a predetermined composition as shown in FIG. After adding 0.1% by mass of the _three powders, they were each mixed in a wet ball mill for 4 hours, then dried and granulated to obtain one type of mixed raw material powder.

The calcination, coarse pulverization, and fine grinding were performed in the same manner as in Experimental Example 1 except that the calcination temperature, CaCO ₃ (addition amount is calculated as CaO) and SiO ₂ addition amount, average particle size, and sintering temperature shown in Table 2 were used. A total of 9 types of sintered ferrite magnets were obtained by pulverizing, molding and firing. Table 2 shows the measurement results of B _r , H _cJ and H _k /H _cJ of the obtained sintered ferrite magnet. In Table 2, samples No. 21 to 26 not marked with * next to sample No. are experimental examples based on the present invention, and samples No. 27 and 28 marked with * are experiments that do not satisfy the present invention. Sample No. 29 marked with an asterisk (*) is an example (comparative example) in which a portion of Co was replaced with Zn in a conventional Sr--La--Co based sintered magnet.

*比較例

表2（続き）

*比較例
Table 2

*Comparative example

Table 2 (continued)

*Comparative example

Sample Nos. 21 and 22 have the same 1-x, x, y, and z as Sample No. 1 of Experimental Example 1, but 2n is reduced (10.26 → 9.76) Experimental example (Samples No. 21 and 22 are The added amounts of CaCO ₃ and SiO ₂ are different), and sample No. 23 is an experimental example in which 2n is further reduced (9.76→9.26) from sample Nos. 21 and 22. As shown in Table 2, it can be seen that H _cJ is improved by decreasing 2n.

Samples No. 24 and 25 have the same 1-x, x, y + z and 2n as sample No. 21, and y + z is 0.26 and y is smaller than sample No. 21 (y = 0.13) (y = 0.10, 0.05 ) is an experimental example. It can be seen that _HcJ tends to decrease as y decreases. From these tendencies, it can be said that y is preferably 0.10 or more in order to obtain higher magnetic properties.

Sample No. 26 is an experimental example in which y is increased in a composition close to sample No. 12 of Experimental Example 1, which satisfies 1-x<x when 0.3<(y+z)≦0.4. It can be seen that H _cJ improves as y increases.

Further, as shown in Table 2, sample No. 27 (y + z = _0.16 ), which does not satisfy 0.2 ≤ (y + z) ≤ 0.4, has a significant decrease in Br, 0 < y < 0.15, 0.1 ≤ z ≤ 0.4 and 0.2 ≤ Sample No. 28 (y=0, z=0.50, y+z=0.50), which does not satisfy any of (y+z) _≤0.4 , shows a significant drop in HcJ.

Furthermore, as shown in Table 2, compared to Sample No. 29, which is an experimental example (comparative example) in which a part of Co was replaced with Zn in the Sr-La-Co sintered magnet, it contained almost the same amount of Co. It can be seen that Sample No. 12 of Experimental Example 1, which has a similar _HcJ , is extremely high in _Br .

According to the present invention, it is possible to provide a ferrite sintered magnet that has a high _{Br, a small decrease in HcJ ,} and uses 25% or more less Co than conventional Sr-La-Co ferrite sintered magnets. Since it becomes possible, it can be suitably used for various motors.

Claims (10)

General formula showing the atomic ratio of the metal elements Ca, R, Fe, Co and Zn (where R is at least one rare earth element and essentially contains La): Ca _1-x R _x Fe _{2n- In yz} Co _y Zn _z ,
The x, y and z, and n (where 2n is the molar ratio and is represented by 2n = (Fe + Co + Zn) / (Ca + R)) are
0.4≤x≤0.6,
0 < y < 0.15,
0.1≤z≤0.4,
0.2≤(y+z)≤0.4, and
4≤n≤6
A ferrite calcined body that satisfies In the ferrite calcined body according to claim 1,
A calcined ferrite body, wherein y satisfies 0<y≦0.13. In the ferrite calcined body according to claim 1 or 2,
1-x, x, y and z are
satisfies 1-x≧x when 0.2≦(y＋z)≦0.3,
A calcined ferrite body characterized by satisfying 1-x<x when 0.3<(y+z)≤0.4. General formula showing the atomic ratio of the metal elements Ca, R, Fe, Co and Zn (where R is at least one rare earth element and essentially contains La): Ca _1-x R _x Fe _{2n- In yz} Co _y Zn _z ,
The x, y and z, and n (where 2n is the molar ratio and is represented by 2n = (Fe + Co + Zn) / (Ca + R)) are
0.3≤x≤0.6,
0 < y < 0.15,
0.05≤z≤0.4,
0.15≤(y+z)≤0.4, and
3.4≤n≤6
A sintered ferrite magnet that satisfies In the ferrite sintered magnet according to claim 4,
A sintered ferrite magnet, further comprising 1.5% by mass or less of SiO ₂ . General formula showing the atomic ratio of the metal elements Ca, R, Fe, Co and Zn (where R is at least one rare earth element and essentially contains La): Ca _1-x R _x Fe _{2n- In yz} Co _y Zn _z ,
The x, y and z, and n (where 2n is the molar ratio and is represented by 2n = (Fe + Co + Zn) / (Ca + R)) are
0.4≤x≤0.6,
0 < y < 0.15,
0.1≤z≤0.4,
0.2≤(y+z)≤0.4, and
4≤n≤6
A raw material powder mixing step for obtaining a mixed raw material powder by mixing raw material powders satisfying
a calcining step of calcining the mixed raw material powder to obtain a calcined body;
a pulverizing step of pulverizing the calcined body to obtain powder of the calcined body;
A method for producing a sintered ferrite magnet, comprising: a molding step of molding the powder of the calcined body to obtain a molded body; and a firing step of firing the molded body to obtain a sintered body. In the method for producing a sintered ferrite magnet according to claim 6,
After the calcining step and before the forming step, a step of adding 1.5% by mass or less of SiO ₂ to 100% by mass of the calcined body or powder of the calcined body. Method of manufacturing magnets. In the method for producing a ferrite sintered magnet according to claim 6 or 7,
After the calcining step and before the molding step, the method further includes a step of adding CaCO ₃ in an amount of 1.5% by mass or less in terms of CaO with respect to 100% by mass of the calcined body or powder of the calcined body. A method for producing a sintered ferrite magnet. In the method for producing a sintered ferrite magnet according to any one of claims 6 to 8,
A method for producing a sintered ferrite magnet, wherein the atomic ratio y of the calcined body satisfies 0<y≦0.13.
In the method for producing a sintered ferrite magnet according to any one of claims 6 to 9,
The atomic ratio 1-x, x, y and z of the calcined body is
satisfies 1-x≧x when 0.2≦(y+z)≦0.3, and satisfies 1-x<x when 0.3<(y+z)≦0.4.