JP2022151652A - Preliminarily baked ferrite material, and method for manufacturing ferrite sintered magnet - Google Patents

Abstract

To provide a preliminarily baked ferrite material which allows a ferrite sintered magnet having high magnet characteristics to be gained, and a method for manufacturing a ferrite sintered magnet by use of such a preliminarily baked ferrite material.SOLUTION: A preliminarily baked ferrite material comprises: a ferrite phase having an M-type magnetoplumbite structure of hexagonal crystal and containing metal elements of Ca, R, A, Fe and Co (R represents at least one kind of rare earth elements, inevitably including La, and A is Sr and/or Ba); and a spinel ferrite phase containing Co. The preliminarily baked ferrite material includes the ferrite phase of no less than 70 mass% and less than 100 mass%, and the spinel ferrite phase of over 0 mass% and no more than 30 mass%.SELECTED DRAWING: None

Description

The present disclosure relates to a method for manufacturing a calcined ferrite body and a sintered ferrite magnet.

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.

Among the various applications where ferrite sintered magnets are used, such as motors and speakers, there is a strong demand for high-performance materials for automobile electrical equipment motors and home appliance motors. In recent years, against the background of soaring prices of rare earth raw materials and the emergence of procurement risks, industrial motors and drive motors and generators for electric vehicles (EV, HV, PHV, etc.), which used to use only rare earth sintered magnets, Applications of sintered ferrite magnets are also being considered.

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 referred to as "CaLaCo magnet" for short) with further improved magnetic properties was developed and is now in practical use.

By the way, sintered ferrite magnets are generally manufactured through the steps of mixing raw materials, calcining, pulverizing, molding, firing, and processing. In general, "calcination" means that a ferrite phase (ferrite compound, sometimes referred to as M phase) having a hexagonal magnetoplumbite type (M type) structure is formed by a solid phase reaction by heating a mixed raw material. It refers to the process of forming, and the product obtained by calcination is called a “calcined body”.

Conventionally, it is natural to increase the constituent phase ratio of the ferrite phase (hereinafter sometimes referred to as "phase ratio") at the stage of the calcined body (preferably to 100% by mass = M phase single phase) has been implemented. This is because the ferrite sintered magnet obtained by pulverizing, molding, and sintering the calcined body also has a high phase ratio of the M phase, and high magnetic properties can be expected. In other words, hematite phase (α-Fe ₂ O ₃ ), orthoferrite phase (LaFeO ₃ etc.) and spinel ferrite phase (CoFe ₂ O ₄ etc.) other than the ferrite phase (M phase) are heterogeneous phases. It has been thought that it is better not to include it in the calcined body.

JP 2020-155609 A

In Patent Document 1, a Ca—La—Co ferrite sintered magnet in which Co is partially replaced with Zn contains 12 to 30% by mass of hematite phase, 3 to 10% by mass of La orthoferrite phase, and a spinel ferrite phase. describes a method for producing a sintered ferrite magnet using a calcined body powder containing 5 to 10% by mass of

In short, the invention described in Patent Document 1 is a CaLaCo magnet having a unique composition in which the La content exceeds 0.55 in terms of atomic ratio and a part of Co is replaced with Zn, and is calcined at a low temperature to form a solid state. By using a calcined body in which the phase reaction is not completely completed (in the middle of the solid phase reaction), adding a small amount of SiO ₂ and CaO, molding and firing, it is possible to obtain a similar composition at a high temperature. It is said that magnetic properties equivalent to those in the case of using a calcined calcined body in which the solid-phase reaction has completely completed are obtained (Patent Document 1, paragraph 0029, etc.).

However, in the CaLaCo magnet of the invention described in Patent Document 1, which has a unique composition in which the La content exceeds 0.55 in terms of atomic ratio and a part of Co is replaced with Zn, a high residual magnetic flux density (hereinafter " B _r ”) can be obtained, but the coercive force (hereinafter referred to as “H _cJ ”) is low, and the magnetic properties are sufficient for applications such as the above-mentioned industrial motors, electric vehicle drive motors and generators. I can not say.

An object of the present disclosure is to provide a ferrite calcined body capable of obtaining a ferrite sintered magnet having high magnetic properties, and a method for producing a ferrite sintered magnet using the ferrite calcined body.

The inventors of the present invention have made extensive research on further improving the performance of CaLaCo magnets. As a result, contrary to the conventional idea that the calcined body must be a single M-phase, if the calcined body in which the solid-phase reaction is completely completed contains a specific amount of spinel ferrite phase, the It has been found that the magnetic properties of a sintered magnet produced using a calcined body are improved. Furthermore, it has been found that the spinel ferrite phase, which is contained in a specific amount, contains more Mn than the ferrite phase (M phase), which is inevitably contained as an impurity and tends to deteriorate the magnetic properties. In other words, the inventors have found that the spinel ferrite phase has the function of taking in Mn to render it harmless and improving the magnetic properties, and that it is no longer a different phase but an essential constituent phase in the calcined body.

That is, the ferrite calcined body of the present disclosure contains metallic elements of Ca, R, A, Fe, and Co (R is at least one rare earth element and contains La, and A is Sr and/or Ba). and a spinel ferrite phase containing Co, wherein the ferrite phase is 70% by mass or more and less than 100% by mass, and the spinel ferrite phase is 0% by mass. A ferrite calcined body characterized by containing more than 30% by mass or less.

The ferrite calcined body of the present disclosure may further contain more than 0% by mass and less than 3% by mass of the La orthoferrite phase.

Preferably, the ferrite calcined body of the present disclosure does not substantially contain a hematite phase.

The ferrite calcined body of the present disclosure preferably contains the spinel ferrite phase in an amount of 5% by mass or more and 30% by mass or less.

The ferrite calcined body of the present disclosure preferably contains the spinel ferrite phase in an amount of 5% by mass or more and 25% by mass or less.

The ferrite calcined body of the present disclosure preferably contains the spinel ferrite phase in an amount of 10% by mass or more and 20% by mass or less.

In the ferrite calcined body of the present disclosure, the calcined body preferably contains Mn, and the Mn content in the spinel ferrite phase is higher than the Mn content in the ferrite phase.

In the ferrite calcined body of the present disclosure, it is preferable that Mn is contained only in the spinel ferrite phase.

In the ferrite calcined body of the present disclosure, the spinel ferrite phase contains Ca, Fe, Co and Mn, and when the total amount of the elements is 100 at%,
Ca: more than 0 at% and 10 at% or less,
Fe: 80 at% or more and 90 at% or less,
Co: 2 at% or more and 15 at% or less, and Mn: more than 0 at% and 5 at% or less,
is preferably a composition ratio of

In the ferrite calcined body of the present disclosure, when the total amount of Ca, R, A, Fe and Co in the ferrite phase is 100 at%,
Ca: 2.0 at% or more and 6.5 at% or less,
R: 2.0 at% or more and 6.5 at% or less,
A: 0 at% or more and 2 at% or less,
Fe: 83 at% or more and 92 at% or less, and Co: 1.5 at% or more and 6.5% or less,
is preferably a composition ratio of

The method for producing a sintered ferrite magnet of the present disclosure includes a molding step of molding the powder of the calcined ferrite body of the present disclosure to obtain a compact, and a firing step of firing the compact to obtain a sintered compact. A method for producing a sintered ferrite magnet containing

In the method for producing a sintered ferrite magnet of the present disclosure, the calcined body is preferably calcined at a temperature of 1250°C or higher and 1350°C or lower.

In the method for producing a sintered ferrite magnet according to the present disclosure, the calcined body is preferably calcined at a temperature of 1280°C or higher and 1330°C or lower.

In the method for producing a sintered ferrite magnet of the present disclosure, the calcined body is preferably calcined at a temperature of 1290°C or higher and 1320°C or lower.

In the method for producing a sintered ferrite magnet of the present disclosure, the calcined body is preferably calcined in a rotary kiln.

In the method for producing a sintered ferrite magnet of the present disclosure, after the calcined body preparation step and before the forming step, more than 0% by mass and not more than 1.5% by mass of SiO ₂ with respect to 100% by mass of the calcined body It is preferable to further include the step of adding

In the method for producing a sintered ferrite magnet of the present disclosure, after the calcined body preparation step and before the forming step, more than 0% by mass and not more than 1.5% by mass in terms of CaO with respect to 100% by mass of the calcined body of CaCO ₃ is preferably further included.

In the method for producing a sintered ferrite magnet of the present disclosure, after the calcined body preparation step and before the forming step, a step of adding 2% by mass or less of Cr ₂ O ₃ with respect to 100% by mass of the calcined body. It is preferable to further include.

According to the present disclosure, it is possible to provide a calcined ferrite body capable of obtaining a sintered ferrite magnet having high magnetic properties, and a method for producing a sintered ferrite magnet using the calcined ferrite body.

1. Ferrite calcined body The ferrite calcined body of the present disclosure is
Hexagonal M-type magnetoplumbite structure containing metallic elements of Ca, R, A, Fe and Co (R is at least one rare earth element and essentially contains La, and A is Sr and/or Ba) and a spinel ferrite phase containing Co, containing 70% by mass or more and less than 100% by mass of the ferrite phase and more than 0% by mass and 30% by mass or less of the spinel ferrite phase.

In addition, the ferrite calcined body of the present disclosure further contains more than 0% by mass and less than 3% by mass of an orthoferrite phase. And it does not substantially contain a hematite phase.

The main phase constituting the ferrite calcined body is a ferrite phase having a hexagonal magnetoplumbite (M-type) structure. In general, magnetic materials, especially sintered magnets, are defined as composed of multiple compounds.

The phrase “having a hexagonal magnetoplumbite-type (M-type) structure” means that a hexagonal magnetoplumbite-type (M-type) structure is obtained in X-ray diffraction measurement of a calcined ferrite powder under general conditions. It means that an X-ray diffraction pattern is mainly observed.

The ferrite phase contained in the ferrite calcined body is 70% by mass or more and less than 100% by mass. If it is less than 70% by mass, high B _r and H _cj cannot be obtained. In the case of 100% by mass, high magnetic properties cannot be obtained.

A spinel ferrite phase having a composition (A _m Fe _3-m )O ₄ (A is Co, Mn, Ni, Cu, Zn, Ca, etc.) is a phase having an equiaxed spinel structure. The ratio of the spinel ferrite phase contained in the ferrite calcined body is more than 0% by mass and 30% by mass or less. At 0% by mass, a high _Hcj cannot be obtained. If it is more than 30% by weight, high B _r and H _cj cannot be obtained. It is preferably 5% by mass or more and 30% by mass or less, more preferably 5% by mass or more and 25% by mass or less, and still more preferably 10% by mass or more and 20% by mass or less.

The orthoferrite phase (such as LaFeO ₃ ) is a phase having a perovskite structure and is a heterogeneous phase in the ferrite calcined body of the present disclosure. do not have. If the content is 3% by mass or more, the ratio of the different phases increases (the ratio of the ferrite phase decreases), and high magnetic properties cannot be obtained.

A hematite phase (α-Fe ₂ O ₃ ) is a different phase in the ferrite calcined body of the present disclosure. The ferrite calcined body of the present disclosure does not substantially contain a hematite phase. “Substantially free” means that it cannot be confirmed by X-ray diffraction. If the ferrite calcined body contains a hematite phase, the magnetic properties (especially saturation magnetization) are significantly lowered.

Also, the metal element contained in each phase can be measured, for example, by EDS (Energy Dispersive X-ray Spectroscopy) analysis of FE-SEM (Field Emission Scanning Electron Microscope). The ferrite phase of the present disclosure contains Ca, R, A, Fe and Co, and when the total amount of each element (the total amount of each element of Ca, R, A, Fe and Co) is 100 at%,
Ca: 2.0 at% or more and 6.5 at% or less,
R: 2.0 at% or more and 6.5 at% or less,
A: 0 at% or more and 2 at% or less,
Fe: 83 at% or more and 92 at% or less, and Co: 1.5 at% or more and 6.5% or less,
is the composition ratio of

The content of Ca is preferably 2.0 atomic % or more and 6.5 atomic % or less. If it is less than 2.0 at % or exceeds 6.5 at %, high magnetic properties cannot be obtained.

The content of R is preferably 2.0 atomic % or more and 6.5 atomic % or less. If it is less than 2.0 at % or exceeds 6.5 at %, high magnetic properties 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 atomic ratio.

The content of the A element is preferably 0 atomic % or more and 2 atomic % or less. The A element is Sr and/or Ba. Although the effect of the present invention is not impaired even if the element A is not contained, the addition of the element A refines the crystals in the calcined body and reduces the aspect ratio, so that the magnetic properties are further improved. effect can be obtained. If the A element exceeds 2 at %, high magnetic properties cannot be obtained.

The Fe content is preferably 83 at % or more and 92 at % or less. If it is less than 83 at % or more than 92 at %, high magnetic properties cannot be obtained.

The Co content is preferably 1.5 at % or more and 6.5% or less. If the content is less than 1.5 at % or exceeds 6.5 at %, high magnetic properties cannot be obtained.

Further, the spinel ferrite phase contains Ca, Fe, Co and Mn, and when the total amount of each element (the total amount of each element of Ca, Fe, Co and Mn) is 100 at%,
Ca: more than 0 at% and 10 at% or less,
Fe: 80 at% or more and 90 at% or less,
Co: 2 at% or more and 15 at% or less, and Mn: more than 0 at% and 5 at% or less,
is the composition ratio of

The content of Ca is preferably more than 0 atomic % and 5 atomic % or less. If it is less than 2.0 at % or exceeds 6.5 at %, high magnetic properties cannot be obtained.

The Fe element content is preferably 80 at % or more and 90 at % or less. If it is less than 80 at % or exceeds 90 at %, high magnetic properties cannot be obtained.

The Co element content is preferably 2 at % or more and 15 at % or less. If the content is less than 1.5 at % or exceeds 6.5 at %, high magnetic properties cannot be obtained.

The content of the Mn element is preferably more than 0 atomic % and 5 atomic % or less. If it exceeds 0 at % or 5 at %, high magnetic properties cannot be obtained.

Mn is contained as an unavoidable impurity in the Fe compound that is the raw material powder. When Mn is contained in the ferrite phase, it causes deterioration of the magnetic properties. can. More preferably, the ferrite phase does not contain Mn, and Mn is contained only in the spinel ferrite phase. Note that Mn is not limited to being contained as an unavoidable impurity, and may be intentionally added.

In addition, the atomic ratio of metal elements in the entire calcined ferrite body of the present disclosure including the ferrite phase and the spinel ferrite phase can be represented by a general formula as follows.
A general formula showing the atomic ratio of the metallic elements of Ca, R, A, Fe and Co (R is at least one rare earth element and essentially contains La, A is Sr and/or Ba): Ca _{1- In x-y} R _x A _y Fe _2n-z Co _z , the x, y and z, and n (2n is the molar ratio, expressed as 2n=(Fe+Co)/(Ca+R+A)) are
0.3 ≤ 1-xy ≤ 0.65,
0.3≦x≦0.65,
0≤y≤0.2,
satisfying 0.25 ≤ z ≤ 0.65 and 4.5 ≤ n ≤ 7,
It contains more than 0% by mass and not more than 0.5% by mass of Mn in terms of MnO.

The above general formula is expressed by the atomic ratio of the metal elements, but the composition containing oxygen (O) is represented by the general formula: Ca _1-x-y R _x A _y Fe _2n-z Co _z O _α be. 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 atomic ratio α of oxygen may deviate from 19 in some cases. Therefore, in the present disclosure, the composition is represented by the atomic ratio of the metal elements, which makes it most easy to specify the composition.

An example of the method for producing the sintered ferrite magnet of the present disclosure, including the above method for producing the calcined ferrite powder 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. Examples of the R compound include rare earth oxides such as _{La2O3, rare earth hydroxides such as La(OH)3 , and} rare earth carbonates such as _{La2 ( CO3} ) _3.8H2O . Compounds of element A include Sr and/or Ba carbonates, oxides, chlorides, and the like. 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 , m ₄ are positive numbers). Mn is contained as an unavoidable impurity or as an additive in Fe compounds.

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. 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 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 a continuous or batch-type electric furnace, gas furnace, or the like, and a hexagonal magnetoplumbite type (M type) structure. This process is called "calcination", and the resulting compound is called "calcined body".

For example, when calcining using a rotary kiln, which is a continuous gas furnace, if the calcining temperature is less than 1250° C., the amount of spinel ferrite phase formed in the calcined body is insufficient, resulting in poor magnetic properties. On the other hand, if the calcining temperature exceeds 1350° C., the spinel ferrite phase becomes more than 30% by mass, resulting in poor magnetic properties. Therefore, the calcination temperature is preferably 1250° C. or higher and 1350° C. or lower. It is more preferably 1280° C. or higher and 1330° C. or lower, and more preferably 1290° C. or higher and 1320° C. or lower.

In the pulverization step, the calcined body is pulverized (coarsely pulverized) with a hammer mill or the like, and then pulverized (finely pulverized) with a vibration mill, a jet mill, a ball mill, an attritor, or the like to obtain a pulverized powder. The average particle size of the pulverized powder is preferably about 0.4 μm to 1.2 μm. When emphasizing the improvement of magnetic properties, the thickness is preferably about 0.4 μm to 0.7 μm. When the manufacturing cost (reduction of pulverization time, reduction of press cycle, etc.) is emphasized, it is preferable to make it about 0.7 μm to 1.2 μm. In 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 to 2% by mass. After wet grinding, the slurry may be concentrated.

Through the steps described above, the powder of the ferrite calcined body of the present disclosure can be obtained. Next, the method for manufacturing the sintered ferrite magnet of the present disclosure will be described.

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 to 1% by mass of 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.

After the calcination step and before the molding step, a sintering aid is added to the calcined body or its pulverized powder. Only SiO ₂ or both SiO ₂ and CaCO ₃ or Cr ₂ O ₃ in addition to SiO ₂ and CaCO ₃ can be added as sintering aids. The amount of SiO ₂ to be added is preferably more than 0% by mass and 1.5% by mass or less with respect to 100% by mass of the calcined body to be added or its pulverized powder. Without the addition of SiO ₂ , the H _cJ would decrease. The amount of SiO ₂ added is more preferably 0.4 to 0.7% by mass.

The amount of CaCO ₃ to be added is preferably more than 0% by mass and 1.5% by mass or less in terms of CaO with respect to 100% by mass of the calcined body to be added or its pulverized powder. If no _CaCO3 is added, the _HcJ will drop. The amount of CaCO ₃ added is more preferably 0.4% by mass or more and 0.0.6% by mass or less.

The amount of Cr ₂ O ₃ to be added is preferably 2% by mass or less with respect to 100% by mass of the calcined body to be added or its pulverized powder. If it is more than 2% by mass, the _Br is significantly lowered. The amount of Cr ₂ O ₃ added is more preferably 1.5% by mass or less.

The sintering aid is added, for example, by adding it to the calcined body obtained by the calcining step and then performing the pulverizing step, adding it during the pulverizing step, or adding it to the finely pulverized powder after the pulverizing step, A method such as performing a molding step after mixing can be adopted. As a sintering aid, in addition to SiO ₂ , CaCO ₃ and Cr ₂ O ₃ , Al ₂ O ₃ and the like may be added.

In the present disclosure, 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 CaCO ₃ in terms of CaO, {(40.08 [atomic weight of Ca] + 12.01 [atomic weight of C] + 48.00 [atomic weight of 0 × 3] = 100.09 [Molecular weight of CaCO ₃ ]) × 0.5% by mass [addition amount in terms of CaO]} / (40.08 [atomic weight of Ca] + 16.00 [atomic weight of 0] = 56.08 [molecular weight of CaO]) = 0.892% by mass [addition amount of _CaCO3 ].

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 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.

During the temperature rise in the firing step, the average temperature increase rate in the temperature range from room temperature to 1100 ° C. is increased at 400 ° C./h or more and 1000 ° C./h or less, and the average temperature increase in the temperature range from 1100 ° C. to the firing temperature. It is preferable to raise the temperature at a rate of 1° C./min or more and 10° C./min or less. In addition, when the temperature is lowered after the firing time is kept in the firing step (including the case where the firing time is not kept), if the average temperature drop rate in the temperature range from the firing temperature to 800 ° C. is 300 ° C./hour or more, the magnetic properties are further improved. Therefore, it is preferable. These effects can be obtained by employing only the temperature drop rate, but it is more preferable to employ both the temperature rise rate and the temperature drop rate. In addition, when the temperature is described, it refers to the temperature of the object to be heat-treated. The temperature is measured by bringing an R thermocouple into contact with the object to be heat-treated in the kiln.

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.

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

Experimental example 1
_CaCO3 powder _{, La2O3} powder _{, Fe2O3 powder ,} and _Co3O4 powder _were weighed with a predetermined composition so as to have the general _{formula Ca0.5La0.5Fe10.1Co0.3} . , 0.12% by mass of H ₃ BO ₃ powder was added to a total of 100% by mass of the weighed powders, and mixed with an attritor to obtain a mixed slurry. The Fe ₂ O ₃ powder contains Mn as an unavoidable impurity.

The resulting mixed slurry was calcined in the atmosphere at the calcining temperature shown in Table 1 to obtain eight kinds of calcined bodies. Sample no. 1 to 7 were calcined in a rotary kiln, and sample No. 1 was used as a comparative example. 8 was calcined in a box type furnace (batch type electric furnace). The obtained calcined bodies were coarsely pulverized with a small mill to obtain eight kinds of coarsely pulverized powders.

The phase ratio (% by mass) of the constituent phases contained in the eight types of coarsely pulverized powder was determined. Table 1 shows the results. The phase ratio was obtained by performing X-ray diffraction using an X-ray diffractometer (D8 ADVANCE TXS manufactured by Bruker AXS) and performing Rietveld analysis on the obtained X-ray diffraction pattern.

To 100% by mass of 8 types of coarsely ground powder, CaCO ₃ (addition amount is calculated as CaO) and SiO ₂ shown in Table 1 are added and finely ground with a wet ball mill using water as a dispersion medium to obtain a finely ground slurry. Obtained. Pulverization was performed until the average particle size (measured by the air permeation method using a powder specific surface area measuring device (SS-100 manufactured by Shimadzu Corporation)) became the particle size shown in Table 1.

While removing the dispersion medium, each finely pulverized slurry is subjected to 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, and a magnetic field of about 1 T is applied, and a pressure of about 2.4 MPa is applied. Molding was carried out under pressure to obtain 8 kinds of moldings.

Each molded body obtained was inserted into a sintering furnace, heated to 1100° C. at a heating rate of 400° C./hour in the air, and raised from 1100° C. to the firing temperature shown in Table 1 at a rate of 1° C./min. After heating, the magnets were sintered for 1 hour, and the temperature was lowered from the sintering temperature shown in Table 1 to room temperature at an average cooling rate of 300°C/hour while air was supplied at 10 L/min to obtain 8 types of sintered ferrite magnets. rice field. 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, sample no. Sample No. not marked with * next to . 1 to 7 are experimental examples based on the embodiment of the present disclosure, and sample Nos. marked with *. 8 is an experimental example (comparative example) that does 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.

Sample No. using the calcined powder having a spinel ferrite phase of 0% by mass. Sample No. 8 using the calcined body powder containing the magnetic properties of No. 8 and the spinel ferrite phase. Comparing the magnet properties of samples No. 1 to 7, sample No. _{Br of 1 to 7 gave similar characteristics, and all HcJ values} were as high as 400 kA/m or more. Furthermore, sample no. 2 to 6, when the spinel ferrite phase is 10% by mass or more and 20% by mass or less, the value of H _cJ is 420 kA/m or more, which is a very high characteristic.

Moreover, sample no. 1 to 7, the calcining temperature at which high magnetic properties are obtained is 1250° C. or higher and 1350° C. or lower. From the results of 2 to 6, it can be seen that the calcination temperature at which higher magnetic properties can be obtained is 1290°C or higher and 1320°C or lower.

Experimental example 2
_CaCO3 powder _{, La2O3} powder _{, Fe2O3 powder ,} and _Co3O4 powder _were weighed with a predetermined composition so as to have the general _{formula Ca0.5La0.5Fe10.1Co0.3} . , 0.12% by mass of H ₃ BO ₃ powder was added to a total of 100% by mass of the weighed powders, and mixed with an attritor to obtain a mixed slurry. The Fe ₂ O ₃ powder contains Mn as an unavoidable impurity.

The resulting mixed slurry was calcined in the atmosphere using a rotary kiln at the calcining temperature shown in Table 2 to obtain 10 kinds of calcined bodies. The obtained calcined bodies were coarsely pulverized with a small mill to obtain 10 kinds of coarsely pulverized powders.

The phase ratios (% by mass) of the constituent phases contained in the 10 types of coarsely pulverized powders were determined and confirmed in the same manner as in Experimental Example 1. Sample No. with a calcination temperature of 1310°C. Sample Nos. 9 to 13 contain 12% by mass of spinel ferrite phase and have a calcining temperature of 1330°C. Nos. 14 to 18 were confirmed to contain 25% by mass of spinel ferrite phase.

Sample no. The composition ratio (at%) of each element when the total amount of each element contained in the ferrite phase of the coarsely pulverized powders of 9 to 18 (total amount of each element of Ca, La, Fe and Co) is 100 at% In order to examine the composition ratio (at%) of each element when the total amount of each element contained in the spinel ferrite phase (the total amount of each element of Ca, Fe, Co and Mn) is 100 at%, Fe-SEM EDS (energy dispersive X-ray spectroscopy) was analyzed using a field emission scanning electron microscope and measured. Table 2 shows the results.

Sample no. It was found that the spinel ferrite phase contained Mn in all of Nos. 9 to 18, and the ferrite phase did not contain Mn. From this, it is considered that the formation of the spinel ferrite phase in the calcined body has the effect of causing the spinel ferrite phase to contain Mn, which causes the deterioration of the magnetic properties, and suppressing its inclusion in the ferrite phase. , it is considered that a ferrite sintered magnet with high magnetic properties was obtained.

Experimental example 3
_CaCO3 powder _{, La2O3} powder _{, Fe2O3 powder ,} and _Co3O4 powder _were weighed with a predetermined composition so as to have the general _{formula Ca0.5La0.5Fe10.1Co0.3} . , 0.12% by mass of H ₃ BO ₃ powder was added to a total of 100% by mass of the weighed powders, and mixed with an attritor to obtain a mixed slurry. The Fe ₂ O ₃ powder contains Mn as an unavoidable impurity.

The resulting mixed slurry was calcined in the air at the calcining temperature shown in Table 3 to obtain a calcined body. Both were calcined in a rotary kiln. Then, each of the obtained calcined bodies was coarsely pulverized by a small mill to obtain a coarsely pulverized powder.

The phase ratio (% by mass) of the constituent phases contained in the coarsely pulverized powder was determined. Table 3 shows the results. The phase ratio of the constituent phases was obtained in the same manner as in Experimental Example 1.

To 100% by mass of coarsely pulverized powder, CaCO ₃ (addition amount is calculated as CaO) and SiO ₂ shown in Table 3 are added and finely pulverized with a wet ball mill using water as a dispersion medium to obtain seven types of pulverized slurry. Obtained. It was milled until the average particle size (measured as in Experimental Example 1) was the particle size shown in Table 3, respectively.

Each pulverized slurry was molded in the same manner as in Experimental Example 1 to obtain seven types of molded bodies.

Each molded body obtained was inserted into a sintering furnace, heated to 1100° C. at a rate of 400° C./hour in the air, and raised from 1100° C. to the firing temperature shown in Table 3 at a rate of 1° C./min. After heating, the magnets were sintered for 1 hour, and cooled from the sintering temperature shown in Table 3 to room temperature at an average cooling rate of 300°C/hour while air was supplied at 10 L/min to obtain seven types of sintered ferrite magnets. rice field. Table 3 shows the measurement results of B _r , H _cJ and H _k /H _cJ of the obtained sintered ferrite magnet.

Sample no. From the results of 19 to 25, since the calcination temperature is in the range of 1290 ° C. or more and 1320 ° C. or less, the spinel ferrite phase is 10 mass% or more and 20 mass% or less, and the _HcJ value is 420 kA / m or more, which is extremely high. high characteristics were obtained.

Experimental example 4
_CaCO3 powder _{, La2O3} powder _{, Fe2O3 powder ,} and _Co3O4 powder _were weighed with a predetermined composition so as to have the general _{formula Ca0.5La0.5Fe10.1Co0.3} . After adding 0.12% by mass of H ₃ BO ₃ powder with respect to the total 100% by mass of the weighed powders, they were each mixed with an attritor to obtain a mixed raw material slurry. The Fe ₂ O ₃ powder contains Mn as an unavoidable impurity.

The obtained mixed raw material slurry was calcined in the atmosphere at the calcining temperature shown in Table 4 to obtain 18 kinds of calcined bodies. Both were calcined in a rotary kiln. The obtained calcined bodies were coarsely pulverized to obtain 18 kinds of coarsely pulverized powders.

The ratio (%) of constituent phases contained in 18 types of coarsely pulverized powder was determined. Table 4 shows the results. The phase ratio was obtained in the same manner as in Experimental Example 1.

To 100% by mass of 18 types of coarsely ground powder, CaCO ₃ (addition amount is calculated as CaO), SiO ₂ and Cr ₂ O ₃ shown in Table 3 are added, and finely ground with a wet ball mill using water as a dispersion medium. , to obtain a finely ground slurry. It was milled until the average particle size (measured as in Example 1) was the particle size shown in Table 4, respectively.

Each pulverized slurry was molded in the same manner as in Experimental Example 1 to obtain 18 types of molded bodies.

Each molded body obtained was inserted into a sintering furnace, heated to 1100° C. at a heating rate of 400° C./hour in the air, and raised from 1100° C. to the firing temperature shown in Table 1 at a rate of 1° C./min. After heating, calcining for 1 hour, lowering the temperature from the calcining temperature shown in Table 4 to 800 ° C. at an average cooling rate of 300 ° C./h while supplying 10 L / min of air, and then cooling to room temperature over 8.5 hours. 18 types of ferrite sintered magnets were obtained. Table 4 shows the measurement results of B _r , H _cJ and H _k /H _cJ of the obtained sintered ferrite magnets.

Sample no. From the results of 26-43, by adding Cr ₂ O ₃ in addition to CaCO ₃ and SiO ₂ , a higher H _cJ can be obtained than when it is not added. is within the range of 1290° C. to 1320° C., the spinel ferrite phase is 10% by mass to 20% by mass, and the value of _HcJ is 420 kA/m or more, which is very high.

According to the present disclosure, it is possible to obtain a ferrite sintered magnet having high magnetic properties, so the provided ferrite sintered magnet can be suitably used for various motors and the like.

Claims (18)

Hexagonal M-type magnetoplumbite structure containing metallic elements of Ca, R, A, Fe and Co (R is at least one rare earth element and essentially contains La, and A is Sr and/or Ba) and a spinel ferrite phase containing Co,
has
A ferrite calcined body containing 70% by mass or more and less than 100% by mass of the ferrite phase and more than 0% by mass and 30% by mass or less of the spinel ferrite phase. 2. The ferrite calcined body according to claim 1, further comprising more than 0 mass % and less than 3 mass % of La orthoferrite phase. 3. The calcined ferrite body according to claim 1, wherein the calcined ferrite body does not substantially contain a hematite phase. 4. The calcined ferrite body according to claim 1, wherein the spinel ferrite phase is contained in an amount of 5% by mass or more and 30% by mass or less. 5. The calcined ferrite body according to claim 4, wherein the spinel ferrite phase is contained in an amount of 5% by mass or more and 25% by mass or less. 6. The calcined ferrite body according to claim 5, wherein the spinel ferrite phase is contained in an amount of 10% by mass or more and 20% by mass or less. In the ferrite calcined body according to any one of claims 1 to 6, the calcined body contains Mn, and the Mn content in the spinel ferrite phase is higher than the Mn content in the ferrite phase. A calcined ferrite body characterized by: 8. A ferrite calcined body according to claim 7, wherein Mn is contained only in said spinel ferrite phase. In the ferrite calcined body according to claim 7 or claim 8, when the spinel ferrite phase contains Ca, Fe, Co and Mn, and the total amount of the elements is 100 at%,
Ca: more than 0 at% and 10 at% or less,
Fe: 80 at% or more and 90 at% or less,
Co: 2 at% or more and 15 at% or less, and Mn: more than 0 at% and 5 at% or less,
A ferrite calcined body characterized by having a composition ratio of In the ferrite calcined body according to any one of claims 1 to 9, when the total amount of Ca, R, A, Fe and Co in the ferrite phase is 100 at%,
Ca: 2.0 at% or more and 6.5 at% or less,
R: 2.0 at% or more and 6.5 at% or less,
A: 0 at% or more and 2 at% or less,
Fe: 83 at% or more and 92 at% or less, and Co: 1.5 at% or more and 6.5% or less,
A ferrite calcined body characterized by having a composition ratio of A ferrite firing comprising a molding step of molding the pulverized powder of the ferrite calcined body according to any one of claims 1 to 10 to obtain a molded body, and a firing step of firing the molded body to obtain a sintered body. A method for producing a condensed magnet. In the method for producing a sintered ferrite magnet according to claim 11,
A method for producing a sintered ferrite magnet, wherein the calcined body is calcined at a temperature of 1250°C or higher and 1350°C or lower. In the method for producing a sintered ferrite magnet according to claim 12,
A method for producing a sintered ferrite magnet, wherein the calcined body is calcined at a temperature of 1280°C or higher and 1330°C or lower. In the method for producing a sintered ferrite magnet according to claim 13,
A method for producing a sintered ferrite magnet, wherein the calcined body is calcined at a temperature of 1290°C or higher and 1320°C or lower. In the method for producing a ferrite sintered magnet according to any one of claims 11 to 14,
A method for producing a sintered ferrite magnet, wherein the calcined body is calcined in a rotary kiln. In the method for producing a sintered ferrite magnet according to any one of claims 11 to 15,
After the calcined body preparation step and before the forming step, the calcined body further includes a step of adding more than 0% by mass and 1.5% by mass or less of SiO ₂ with respect to 100% by mass 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 11 to 16,
After the calcined body preparation step and before the forming step, a step of adding CaCO ₃ exceeding 0% by mass and not more than 1.5% by mass in terms of CaO with respect to 100% by mass of the calcined body. A method for producing a sintered ferrite magnet characterized by: In the method for producing a ferrite sintered magnet according to any one of claims 11 to 17,
After the calcined body preparation step and before the forming step, a step of adding 2% by mass or less of Cr ₂ O ₃ with respect to 100% by mass of the calcined body. Production method.