JP7287371B2 - Calcined ferrite body, sintered ferrite magnet and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present disclosure 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 cheap iron oxide, which makes 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 SrFe ₁₂ O ₁₉ . In the _latter half of the _1990s ^, a Sr— ^La —Co ferrite sintered magnet (hereinafter ^abbreviated as “ ^SrLaCo magnet ) has been put to practical use, the magnetic properties of ferrite magnets have greatly improved. In 2007, a Ca--La--Co system ferrite sintered magnet (hereinafter sometimes abbreviated as "CaLaCo magnet") with further improved magnetic properties was put to practical use.

Both SrLaCo magnets and CaLaCo magnets require Co to obtain high magnetic properties. In general SrLaCo magnets, Co has an atomic ratio of about 0.2 (Co/Fe=0.017, that is, about 1.7% of the Fe content), whereas in conventional CaLaCo magnets, Co has an atomic ratio of about 0.3. Co (Co/Fe=0.03, that is, about 3% of the Fe content) is contained. 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, conventional CaLaCo magnets inevitably require an increase in raw material costs compared to general SrLaCo magnets. The greatest feature of sintered ferrite magnets is their low cost, so even if they have excellent magnetic properties, high prices will not be accepted in the market. Therefore, worldwide demand for Sr--La--Co ferrite sintered magnets is still high.

On the other hand, among the various applications where ferrite sintered magnets are used, such as motors and speakers, motors for automobile electrical equipment and motors for household appliances are in strong demand for higher performance. In recent years, against the backdrop of soaring prices of rare earth raw materials and the emergence of procurement risks, ferrites are also being used in industrial motors, EV (Electric Vehicle)/HEV drive motors and generators, etc., where only rare earth magnets were used until now. Applications of sintered magnets are being considered.

In order to use them for such applications, high residual magnetic flux density (hereinafter referred to as " _Br ") and high A sintered ferrite magnet having magnetic properties satisfying both coercive force (hereinafter referred to as “H _cJ ”) and high squareness ratio (hereinafter referred to as “H _k /H _cJ ”) is required.

Patent Document 1 proposes a CaLaCo magnet in which part of Ca is replaced with Sr.
Although the CaLaCo magnet in Patent Document 1 contains Co at an atomic ratio of about 0.3 and has high _Br and _HcJ , no data on _Hk / _HcJ is disclosed.

Japanese Patent No. 4254897

Embodiments of the present disclosure are sintered ferrite magnets that have magnetic properties that satisfy all of high B _r , high H _cJ and high H _k /H _cJ , and that use less Co than conventional CaLaCo magnets. enable the offer.

The inventor has diligently studied how to improve _Hk / _HcJ and reduce the amount of Co used while maintaining the high _Br and high _HcJ of CaLaCo magnets. The inventors have focused on the fact that H _k /H _cJ is greatly improved by improving the degree of magnetic orientation (residual magnetic flux density/saturation magnetization=B _r /J _s ). As a result of further research, it was found that the Fe content was reduced more than the general CaLaCo magnet disclosed in Patent Document 1, and the Co content was suppressed to 0.3 or less in terms of atomic ratio, while the ratio of La to Co was It was found that by increasing the content ratio (La/Co), the degree of magnetic orientation is significantly improved, and _Hk / _HcJ is greatly improved while maintaining high _Br and high _HcJ . Furthermore, the inventors have found that H _cJ and H _k /H _cJ can be further improved by appropriately controlling the heating conditions and cooling conditions during firing.

Non-limiting exemplary ferrite calcined bodies of the present disclosure include atoms of metallic elements Ca, R, Sr, Fe, and Co (where R is at least one of rare earth elements and an element essentially containing La) In the general formula showing the ratio: Ca _{1-xy R x Sr} y _{Fe 2n-z} Co _z , the above x, y and z, and n (where 2n is the molar ratio, 2n=(Fe+Co)/ (Ca + R + Sr)) is 0.4 ≤ x < 0.5, 0 < y ≤ 0.2, 0.18 < z < 0.3, 2.0 ≤ x/z ≤ 2.25, and 8.5≦2n−z≦10.

In some embodiments, 9<2n−z≦10.

A non-limiting example ferrite sintered magnet of the present disclosure contains atoms of metallic elements Ca, R, Sr, Fe, and Co (where R is at least one rare earth element and essentially contains La). In the general formula showing the ratio: Ca _{1-xy R x Sr} y _{Fe 2n-z} Co _z , the above x, y and z, and n (where 2n is the molar ratio, 2n=(Fe+Co)/ (Ca + R + Sr)) is 0.35≦x<0.5, 0<y≦0.2, 0.18<z<0.3, 1.8< x/z≦2.25, and 7.5≦2n−z≦10.

In some embodiments, 8<2n−z≦10. In some embodiments, 1.8< x/z≦2.0.

In one embodiment, it further contains 1.5 mass% or less (not including 0 mass%) of Cr in terms of Cr ₂ O ₃ .

In one embodiment, Si is further contained in an amount of 1.0 mass% or less (not including 0 mass%) in terms of _SiO2 .

An exemplary non-limiting method for producing a sintered ferrite magnet of the present disclosure includes the following metal elements: Ca, R, Sr, Fe and Co (where R is at least one rare earth element and contains La In the general formula showing the atomic ratio of Ca _1-x-y R _x Sr _y Fe _2n-z Co _z , the above x, y and z, and n (where 2n is the molar ratio and 2n=( Fe+Co)/(Ca+R+Sr)) is 0.4≦x<0.5, 0<y≦0.2, 0.18<z<0.3, 1.6≦x/z≦2 .25 and 8.5≦2n−z≦10, a raw material powder mixing step of obtaining a mixed raw material powder, and 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 a powder of the calcined body, a molding step of molding the powder of the calcined body to obtain a compact, and a firing step of firing the compact to obtain a sintered body. , In the firing step, the average temperature increase rate in the temperature range from room temperature to 1100 ° C. is 600 ° C./h or more and 1000 ° C./h or less, and the average temperature increase rate in the temperature range from 1100 ° C. to the firing temperature is 1 C./min or more and 10.degree.

In some embodiments, 9<2n−z≦10.
In some embodiments, 1.6≦x/z≦2.0.

In one embodiment, after the calcination step and before the molding step, 1.5 mass% or less (not including 0 mass%) of Cr ₂ O ₃ with respect to 100 mass% of the powder of the calcined body or the calcined body. The step of adding is further included.

In one embodiment, after the calcination step and before the molding step, 1.0 mass% or less (not including 0 mass%) of SiO ₂ is added to 100 mass% of the calcined body or powder of the calcined body. Further comprising steps.

In one embodiment, after the calcination step and before the molding step, CaCO ₃ of 1.0 mass% or less (excluding 0 mass%) in terms of CaO with respect to 100 mass% of the calcined body or powder of the calcined body further comprising the step of adding

According to an embodiment of the present disclosure, a ferrite sintered magnet that has magnetic properties that satisfy all of high B _r , high H _cJ and high H _k /H _cJ and that uses less Co than conventional CaLaCo magnets can be provided.

1. Ferrite calcined body The ferrite calcined body of the embodiment of the present disclosure contains atoms of metallic elements of Ca, R, Sr, Fe and Co (where R is at least one rare earth element and an element essentially containing La) In the general formula showing the ratio: Ca _{1-xy R x Sr} y _{Fe 2n-z} Co _z , the above x, y and z, and n (where 2n is the molar ratio, 2n=(Fe+Co)/ (Ca + R + Sr)) is 0.4 ≤ x < 0.5, 0 < y ≤ 0.2, 0.18 < z < 0.3, 2.0 ≤ x/z ≤ 2.25, and 8.5≦2n−z≦10.

The atomic ratio x (content of R) is 0.4≦x<0.5. If x is less than 0.4 or greater than 0.5, high magnetic properties (B _r , H _cJ , H _k /H _cJ ) cannot be obtained. In particular, when x is 0.5 or more, heterogeneous phases such as R-rich phases and spinel phases are generated, and the magnetic properties (particularly H _k /H _cJ ) are significantly degraded. R is at least one rare earth element and essentially contains La. It is preferable that La is contained in a molar ratio of 50% or more, and it is more preferable that only R=La.

The atomic ratio y (content of Sr) is 0<y≦0.2. If y is 0 (not contained) or exceeds 0.2, high magnetic properties (B _r , H _cJ , H _k /H _cJ ) cannot be obtained. In particular, when y is 0 (does not contain), the Ca content becomes relatively large, resulting in the generation of a Ca-rich heterophase, which significantly reduces the magnetic properties (especially H _k /H _cJ ). That is, Sr has a role of suppressing heterophase formation.

The atomic ratio z (content of Co) is 0.18<z<0.3. As described above, conventional CaLaCo magnets contain Co at an atomic ratio of about 0.3, but in the embodiments of the present disclosure, the Co content can be reduced below 0.3. This is one of the features of the embodiments of the present disclosure. If z is 0.18 or less, high magnetic properties (B _r , H _cJ , H _k /H _cJ ) cannot be obtained. If z is 0.3 or more, the effect of reducing the amount of Co used cannot be obtained.

The atomic ratio x (content of R) and the atomic ratio z (content of Co) satisfy 1.6≦x/z≦2.25. This is the second feature of the embodiments of the present disclosure. In the first place, R (hereinafter, R is called La for ease of explanation) is added to satisfy the electrical neutrality of Fe ³⁺ and Co ²⁺ , and basically x/z=1 (La/ Co=1), but the present inventors previously found that _Br and _HcJ are improved by making La/Co greater than 1 regardless of electrical neutrality. and so on. However, since the conventional CaLaCo magnet based on Patent Document 1 was thought to require a Co atomic ratio of about 0.3, in order to make the La/Co ratio greater than 1, a relatively large amount of La must be contained. However, when the La content increases, heterogeneous phases such as La-rich phases and spinel phases are formed, and H _k /H _cJ is remarkably lowered. Therefore, in the conventional CaLaCo magnet based on Patent Document 1, La/Co=1.67 (La=0.5, Co=0.3) was the limit in terms of magnet properties. In the embodiment of the present disclosure, the atomic ratio z (content of Co) is 0.18<z≦0.3, so even if x/z is 1.6≦x/z≦2.2, La The content is not excessively high, suppressing the formation of heterogeneous phases and improving H _k /H _cJ . More preferably, x/z satisfies 1.6≦x/z≦2.0, and more preferably satisfies 1.8≦x/z≦2.0.

2n−z (Fe content) is 8.5≦2n−z≦10. 2n is a molar ratio, expressed as 2n=(Fe+Co)/(Ca+R+Sr). In the conventional CaLaCo magnet based on Patent Document 1, n was 5.2≦n≦5.8 (2n is 10.4≦n≦11.6). In embodiments of the present disclosure, the Fe content is reduced over conventional CaLaCo magnets. This is the third feature of the embodiments of the present disclosure. 2n−z is more preferably 9<2n−z≦10.

0.18 < z ≤ 0.3 (small Co content), 1.6 ≤ x/z ≤ 2.25 (large R/Co), 8.5 ≤ 2n-z ≤ as described above 10 (low Fe content), the sintered ferrite magnets based on the embodiments of the present disclosure have a magnetic orientation (B _r /J _s ) is very high (eg 98.4% or more, in a preferred embodiment 99% or more). This makes it possible to significantly improve H _k /H _cJ (over 90% in preferred embodiments) while maintaining high B _r and high H _cJ .

Although the general formula is expressed by the atomic ratio of metal elements, the composition containing oxygen (O) is represented by the general formula: Ca _1-xy R _x Sr _y Fe _2n-z Co _{z Oα} . 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 in some cases. Therefore, in the embodiments of the present disclosure, the composition is represented by the atomic ratio of the metal elements, which makes it most easy to identify the composition.

The main phase constituting the ferrite calcined body of the embodiment of the present disclosure 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."

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

An example of a method for manufacturing a sintered ferrite magnet according to an embodiment of the present disclosure, including the above-described method for manufacturing a calcined ferrite body according to an embodiment of the present disclosure, will be described below.

2. Method for producing sintered ferrite magnet As raw material powders, compounds such as oxides, carbonates, hydroxides, nitrates, and chlorides of respective metals can be used regardless of their valences. A solution obtained by dissolving the raw material powder may be used. Examples of Ca compounds include carbonates, oxides, and chlorides of Ca. As the compound of R, taking La as an example, oxides such as La ₂ O ₃ , hydroxides such as La(OH) ₃ , and carbonates such as La ₂ (CO ₃ ) _{3.8H 2} O can be mentioned. be done. Sr compounds include carbonates, oxides, and chlorides of Sr. Examples of Fe compounds include iron oxide, iron hydroxide, iron chloride, mill scale, and the like. 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 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 mass % or less, most preferably about 0.1 mass %. Since H ₃ BO ₃ also has the effect of controlling the shape and size of crystal grains during firing, 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 embodiment of the present disclosure described above 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, or the like to form a ferrite compound having a hexagonal magnetoplumbite (M-type) structure through a solid phase reaction. Form. This process is called "calcination", and the resulting compound is called "calcined body". Therefore, the ferrite calcined body of the embodiment of the present disclosure can be rephrased as a ferrite compound.

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 great deal of 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.

Through the steps described above, the calcined ferrite body of the embodiment of the present disclosure can be obtained. A method for manufacturing a sintered ferrite magnet according to an embodiment of the present disclosure will now be described.

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 embodiments of the present disclosure, the value measured by the air permeation method using a powder specific surface area measuring device (eg 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 mass % to 2 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 the orientation, 0.1 mass % to 1 mass % 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.

Additives 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. Cr ₂ O ₃ , SiO ₂ and CaCO ₃ are preferred as additives. The amount of Cr ₂ O ₃ to be added is preferably 1.5 mass % or less with respect to 100 mass % of the powder of the calcined body or calcined body to be added. Similarly, the amount of SiO ₂ added is preferably 1.0 mass % or less. Further, the amount of CaCO ₃ added is preferably 1.0 mass% or less in terms of CaO.

Cr ₂ O ₃ , SiO ₂ and CaCO ₃ are known additives for sintered ferrite magnets. The addition of these additives has the advantage of improving H _cJ , but has the disadvantage of lowering _Br and H _k /H _cJ . However, in the embodiment of the present disclosure, the magnetic orientation degree (B _r /J _s ) is significantly improved by the three main features described above, so the decrease in B _r and H _k /H _cJ is suppressed. can improve the _HcJ only. Additives are added, for example, to the calcined body obtained by the calcining process and then subjected to the crushing process, added during the crushing process, or powder of the calcined body after the crushing process (pulverized It is possible to adopt a method such as adding to powder) and performing a molding step after mixing. In addition to the above additives, 1 mass % or less of Al ₂ O ₃ and the like may be added.

The sintered ferrite magnet of the embodiment of the present disclosure belongs to the sintered ferrite magnet of the Ca--La--Co system, as is evident from its composition. Since Ca—La—Co ferrite sintered magnets contain Ca as a main phase component, SiO ₂ and CaCO ₃ are not added like general Sr—La—Co ferrite sintered magnets. A liquid phase can be generated and sintered without the addition of materials. That is, it is possible to manufacture the sintered ferrite magnet of the embodiment of the present disclosure without adding SiO ₂ and CaCO ₃ that mainly form grain boundary phases in the sintered ferrite magnet.

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

A molded body 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 performed in an atmosphere having 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 0 hour (no holding at the firing temperature) to 2 hours.

In the embodiment of the present disclosure, the temperature rising/lowering conditions during firing are as follows. The average temperature increase rate in the temperature range from room temperature to 1100°C is 600°C/hour or more and 1000°C/hour or less, and the average temperature increase rate in the temperature range from 1100°C to the firing temperature is 1°C/minute or more and 10°C/minute or less. and the average cooling rate in the temperature range from the firing temperature to 800° C. is 1000° C./hour or more. As a result, H _cJ and H _k /H _cJ can be further improved without lowering the _Br of the obtained sintered ferrite magnet. This is also one of the features of the embodiments of the present disclosure.

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 embodiment of the present disclosure can be sintered by generating a liquid phase without adding additives such as SiO ₂ and CaCO ₃ . A ferrite sintered magnet of the disclosed embodiments can be obtained. At this time, the components and composition of the ferrite calcined 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 an additive is added, especially when a Ca component (for example, CaCO ₃ ), which is also the main component of the ferrite calcined body, is added, the Ca component increases in the ferrite sintered magnet as a whole. element will decrease. For example, using the ferrite calcined body of the embodiment of the present disclosure, when 1.0 mass% of CaCO ₃ is added as an additive in terms of CaO, the maximum variation is 0.4 ≤ x < 0.5 (calcined body) becomes 0.35 ≤ x < 0.5 (sintered magnet), 8.5 ≤ 2n-z ≤ 10 (calcined body) becomes 7.5 ≤ 2n-z ≤ 10 (sintered magnet) . In this case, the preferred range of 2n−z is 8<2n−z≦10.

Therefore, in the ferrite sintered magnet of the embodiment of the present disclosure, the atomic ratio of the metallic elements Ca, R, Sr, Fe and Co (where R is at least one rare earth element and essentially contains La) is In the general formula shown: Ca _1-x-y R _x Sr _y Fe _2n-z Co _z , the above x, y and z, and n (where 2n is a molar ratio, 2n=(Fe+Co)/(Ca+R+Sr ) is represented by 0.35≦x<0.5, 0<y≦0.2, 0.18<z<0.3, 1.8< x/z≦2.25, and 7 .5≦2n−z≦10.

The composition of the sintered ferrite magnet of the embodiment of the present disclosure 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 of the embodiment of the present disclosure. In addition, as described above, although the range varies from the ferrite calcined body, the reasons for limiting the atomic ratios x, y, and z, and the reasons for limiting 2n−z are the same as those for the ferrite calcined body, so an explanation will be given. omitted.

As described above, in the method for producing a sintered ferrite magnet according to the embodiment of the present disclosure, when Cr ₂ O ₃ is added as an additive in an amount of 1.5 mass% or less with respect to 100 mass% of the calcined body or powder of the calcined body There is Cr ₂ O ₃ added as an additive dissolves in the main phase during firing (sintering). Therefore, when Cr ₂ O ₃ is added in the above amount as an additive, the resulting sintered ferrite magnet contains Cr in an amount of 1.5 mass % or less (not including 0 mass %) in terms of Cr ₂ O ₃ .

Similarly, SiO ₂ as an additive may be added in an amount of 1.0 mass% or less with respect to 100 mass% of the powder of the calcined body or the calcined body. SiO ₂ added as an additive 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 an additive, the obtained sintered ferrite magnet contains 1.0 mass % or less (not including 0 mass %) of Si in terms of SiO ₂ .

At this time, due to the content of Cr and Si, the content of each element represented by the general formula: Ca _1-xy R _x Sr _y Fe _2n-z Co _z is relatively reduced. The ranges of x, y, z, n, etc. in the general formula are basically unchanged. The content of Cr and Si is each composition (mass%) of Ca, La, Sr, Fe, Co and Cr and Si in the result of component analysis of the sintered ferrite magnet (for example, the result of ICP emission spectrometry). From, CaCO ₃ , La(OH) ₃ , SrCO ₃ , Fe ₂ O ₃ , Co ₃ O ₄ and Cr ₂ O ₃ , SiO ₂ in terms of mass, and the content ratio (mass%) with respect to the total 100 mass be.

The embodiments of the present disclosure will be described in more detail by examples, but the embodiments of the present disclosure are not limited thereto.

Experimental example 1
As an experimental example based on the embodiment of the present disclosure, sample No. 1 in Table 1 having an atomic ratio in the general formula Ca _1-xy La _x Sr _y Fe _2n-z Co _z was used. CaCO ₃ powder, La(OH) ₃ powder, SrCO ₃ powder, Fe ₂ O ₃ powder and Co ₃ O ₄ powder so that 1-xy, x, y, z and 2n-z shown in 1 to 15 was weighed with a predetermined composition, and after adding 0.1 mass% of H ₃ BO ₃ powder to a total of 100 mass% of the powder after weighing, each was mixed in a wet ball mill for 4 hours, then dried and granulated to 6 types. was obtained. Each of the obtained mixed raw material powders was calcined in the atmosphere at 1200° C. for 3 hours to obtain 6 kinds of calcined bodies.

Each of the obtained calcined bodies was coarsely pulverized with a small mill to obtain coarsely pulverized powders of six types of calcined bodies. CaCO ₃ (addition amount is calculated as CaO), SiO ₂ and Cr ₂ O ₃ shown in Table 1 are added to 100 mass% of the coarsely pulverized powder of each calcined body obtained, and a wet ball mill using water as a dispersion medium is used. The powder was pulverized until the average particle size reached 0.6 μm (measured by the air permeation method using a powder specific surface area measuring device (SS-100 manufactured by Shimadzu Corporation)) to obtain 15 types of 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. While molding at a pressure of about 2.4 MPa, 15 kinds of moldings were obtained.

Each molded body obtained was inserted into a sintering furnace, and the temperature range from room temperature to 1100 ° C. was raised at an average rate of 1000 ° C./hr while air flowed at a flow rate of 10 L / min. C. to the firing temperature (1210.degree. C.) at an average rate of 1.degree. C./min, and fired at 1210.degree. After firing, the heater of the firing furnace is turned off, the air flow rate is set to 10 L/min to 40 L/min, and the temperature range from the firing temperature (1210 ° C.) to 800 ° C. is lowered at an average rate of 1140 ° C./hour. Fifteen kinds of sintered ferrite magnets were obtained by cooling to room temperature in a furnace.

Table 1 shows the measurement results of J _s , B _r , B _r /J _s , H _cJ , H _k and H _k /H _cJ of the obtained ferrite sintered magnets. In Table 1, sample no. Sample No. not marked with * next to . 3 to 15 are experimental examples based on the embodiment of the present disclosure, and sample Nos. marked with *. 1 and 2 are experimental examples (comparative examples) that do not satisfy the embodiment of the present disclosure. Note that H _k in Table 1 means that J is 0.95×J _r (J _r is residual magnetization, J _r =B _r ) is the value of H at the position.

The atomic ratio in Table 1 indicates the atomic ratio (blended composition) when the raw material powders are 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 additives (CaCO ₃ , SiO ₂ and Cr ₂ O ₃ ) added after the calcination process and before the forming process. It is basically the same as the result of analyzing the sintered magnet with an ICP emission spectrometer (eg, ICPV-1017 manufactured by Shimadzu Corporation).

In Table 1, sample no. Samples 1 and 2, 3 and 4, and 5 and 6 have the same composition and manufacturing conditions except that the amount of SiO ₂ added is changed. As is clear from the magnetic properties shown in Table 1, increasing the amount of SiO ₂ added significantly improves _HcJ , but sample No. When x/z (La/Co) is 1.4 as in No. 2, the range of decrease in _Br is large and _Hk / _HcJ is also greatly decreased. On the other hand, sample no. When x/z (La/Co) is 1.6 or more as in 4 and 6, the decrease in _Br is small and the decrease in _Hk / _HcJ is also suppressed.

Also, in Table 1, sample No. 7 to 9, 10 to 12, and 13 to 15 have the same composition and manufacturing conditions, except that the amount of Cr ₂ O ₃ added is changed. As is clear from the magnetic properties shown in Table 1, H _cJ increases as the amount of Cr ₂ O ₃ added increases, but the decrease in _Br is small, and H _k /H _cJ is improved rather than suppressed. There is a tendency.

As in the experimental examples based on the embodiments of the present disclosure, even if the amount of SiO ₂ and Cr ₂ O ₃ added is increased, H _cJ is improved while suppressing the decrease in _Br and H _k /H _cJ . can be 0.18<z≤0.3 (low Co content), 1.6≤x/z≤2.25 (high R/Co), 8.5≤2n-z≤ It is believed that the magnetic orientation degree (B _r /J _s ) is improved due to the three main features of 10 (low Fe content).

Furthermore, as is clear from Table 1, as x/z (La/Co) increases, the degree of magnetic orientation (B _r /J _s ) improves and H _k /H _cJ also improves. This is because the slope of the line connecting _Js and _Br in the demagnetization curve is improved.

In addition, H _k /H _cJ is improved because, in the embodiment of the present disclosure, the atomic ratio z (content of Co) is 0.18<z≦0.3, so x/z is 1.5. This is probably because the content of La does not become too large even when 6≦x/z≦2.2, and the formation of heterogeneous phases is suppressed.

Ferrite sintered magnets according to embodiments of the present disclosure, which have magnetic properties that satisfy all of high B _r , high H _cJ , and high H _k /H _cJ , and that use less Co than conventional CaLaCo magnets, are available in various types. It can be suitably used for motors and the like.

Claims (14)

General formula showing the atomic ratio of the metal elements Ca, R, Sr, Fe and Co (where R is at least one rare earth element and essentially contains La): Ca _1-xy R _x Sr _y In Fe _2n−z Co _z , the x, y and z, and n (where 2n is the molar ratio and is represented by 2n=(Fe+Co)/(Ca+R+Sr)) are 0.4≦x< 0.5, 0 < y ≤ 0.2, 0.18 < z < 0.3, 2.0 ≤ x/z ≤ 2.25, and 8.5 ≤ 2n-z ≤ 10. Charred body. 2. The ferrite calcined body according to claim 1, wherein 9<2n−z≦10. General formula showing the atomic ratio of the metal elements Ca, R, Sr, Fe and Co (where R is at least one rare earth element and essentially contains La): Ca _1-xy R _x Sr _y In Fe _2n−z Co _z , the x, y and z, and n (where 2n is the molar ratio and is represented by 2n=(Fe+Co)/(Ca+R+Sr)) are 0.35≦x< 0.5, 0<y≤0.2, 0.18<z<0.3, 1.8< x/z≤2.25, and 7.5≤2n-z≤10 binding magnets. 4. The sintered ferrite magnet according to claim 3 , wherein 8<2n−z≦10. 5. The sintered ferrite magnet according to claim 3 , wherein 1.8< x/ z≤2.0 . The sintered ferrite magnet according to any one of claims 3 to 5, further containing 1.5 mass% or less (not including 0 mass%) of Cr in terms of Cr ₂ O ₃ . Cr ₂ O. ₃ The sintered ferrite magnet according to any one of claims 3 to 5, further containing 0.7 mass% or more and 1.2 mass% or less of Cr in terms of conversion. The sintered ferrite magnet according to any one of claims 3 to 7, further containing 1.0 mass% or less (not including 0 mass%) of Si calculated as _SiO2 . General formula showing the atomic ratio of the metal elements Ca, R, Sr, Fe and Co (where R is at least one rare earth element and essentially contains La): Ca _1-xy R _x Sr _y In Fe _2n−z Co _z , the x, y and z, and n (where 2n is the molar ratio and is represented by 2n=(Fe+Co)/(Ca+R+Sr)) are 0.4≦x< Raw material powder satisfying 0.5, 0<y≤0.2, 0.18<z<0.3, 1.6≤x/z≤2.25, and 8.5≤2n-z≤10 A raw material powder mixing step of obtaining a mixed raw material powder by mixing, a calcining step of calcining the mixed raw material powder to obtain a calcined body, a pulverizing step of crushing the calcined body to obtain a calcined powder, 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. The temperature rise rate is 600° C./hour or more and 1000° C./hour or less, and the average temperature increase rate in the temperature range from 1100° C. to the firing temperature is 1° C./minute or more and 10° C./minute or less, and the temperature from the firing temperature to 800° C. A method for producing a ferrite sintered magnet with an average temperature drop rate of 1000° C./hour or more in a range. 10. The method for producing a sintered ferrite magnet according to claim 9, wherein 9<2n−z≦10. 11. The method for producing a sintered ferrite magnet according to claim 9 or 10, wherein 1.6≤x/z≤2.0. After the calcination step and before the molding step, a step of adding 1.5 mass% or less (excluding 0 mass%) of Cr ₂ O ₃ to 100 mass% of the calcined body or powder of the calcined body. The method for producing a sintered ferrite magnet according to any one of claims 9 to 11. After the calcining step and before the forming step, the calcined body or the calcined body further includes a step of adding 1.0 mass% or less (not including 0 mass%) of SiO ₂ to 100 mass% of the powder of the calcined body. Item 13. A method for producing a ferrite sintered magnet according to any one of items 9 to 12. After the calcination step and before the molding step, a step of adding CaCO ₃ in an amount of 1.0 mass% or less (excluding 0 mass%) in terms of CaO with respect to 100 mass% of the calcined body or powder of the calcined body. The method for producing a sintered ferrite magnet according to any one of claims 9 to 13, further comprising: