JPWO2014084059A1 - Ferrite compound - Google Patents

Abstract

A ferrite compound having a hexagonal M-type magnetoplumbite structure and containing Ca, La, Fe and Co as essential components, 2a, 4e, 4f1 in the unit cell of the M-type magnetoplumbite structure, A ferrite compound in which the total amount of Ca present at 4f2 and 12k sites is 0.05 or more per unit cell.

Description

  The present invention relates to a ferrite compound used for a ferrite sintered magnet or the like.

Ferrite sintered magnets are used in various applications such as various motors, generators, and speakers. As typical ferrite sintered magnets, Sr ferrite (SrFe ₁₂ O ₁₉ ) and Ba ferrite (BaFe ₁₂ O ₁₉ ) having a hexagonal M-type magnetoplumbite structure are known. These sintered ferrite magnets are manufactured at a relatively low cost by powder metallurgy using iron oxide and strontium (Sr) or barium (Ba) carbonate as raw materials.

In recent years, due to environmental considerations and the like, there has been a demand for higher performance of sintered ferrite magnets for the purpose of reducing the size, weight, and efficiency of automotive electrical parts, electrical equipment parts, and the like. In particular, motors used in automotive electrical components maintain high residual magnetic flux density B _r (hereinafter simply referred to as “B _r ”), and do not demagnetize due to strong demagnetizing fields when thinned. There is a demand for a ferrite sintered magnet having a magnetic force H _cJ (hereinafter simply referred to as “H _cJ ”) and a high squareness ratio H _k / H _cJ (hereinafter simply referred to as “H _k / H _cJ ”). Here, H _k is a position where J becomes a constant ratio with respect to the value of J _r (residual magnetization) in the second quadrant of the J (magnetization magnitude) −H (magnetic field strength) curve. Is the value of H (hereinafter the same). The 0.90 J _r to 0.95J _r is used as the value of a certain percentage.

Order to improve the magnetic properties of the sintered ferrite magnet was replaced with the rare earth element La, etc. Some of the Sr in the above Sr ferrite, by substituting a part of Fe with Co, the H _cJ and B _r Japanese Patent Laid-Open No. 10-149910 and Japanese Patent Laid-Open No. 11-154604 have proposed a method for improvement.

  As described in JP-A-10-149910 and JP-A-11-154604, Sr ferrite in which a part of Sr is substituted with a rare earth element such as La and a part of Fe is substituted with Co or the like (hereinafter referred to as “SrLaCo ferrite”). ) Is excellent in magnet properties, and instead of conventional Sr ferrite and Ba ferrite, it is being widely used in various applications, but further improvement in magnet properties is also desired.

Japanese Patent Laid-Open No. 2001-223104 describes that in order to improve the _HcJ of the SrLaCo ferrite, the temperature increase rate in the temperature range from 900 ° C. to the maximum temperature is 1 to 5 ° C./min in the temperature increase process of the firing step. Propose to do. In the examples of JP-A-2001-223104, in the composition of Sr _1-x La _x (Fe _12-y Co _y ) _z O ₁₉ , the heating rate is set to 1 to 5 ° _C./min. Is stated to improve. JP-A-2001-223104 describes that the temperature lowering rate is not particularly limited and is usually 1 to 20 ° C./min. In the examples, the temperature lowering rate is 5 ° C./min.

On the other hand, Ca ferrite is also known as a ferrite sintered magnet together with the Sr ferrite and Ba ferrite. It is known that Ca ferrite has a stable structure represented by a composition formula of CaO—Fe ₂ O ₃ or CaO—2Fe ₂ O ₃ and forms hexagonal ferrite by adding La. However, the obtained magnet characteristics are similar to those of the conventional Ba ferrite and are not sufficiently high.

Patent No. 3181559, the improvement of B _r and H _cJ of the Ca ferrite, and for improving the temperature characteristics of the H _cJ, were replaced with rare earth elements of La such a portion of Ca, Co, etc. for a portion of Fe in was replaced, 20 kOe or more anisotropic magnetic field H _a (hereinafter, simply referred to as "H _a") discloses a Ca ferrite (hereinafter referred to as "CaLaCo ferrite") with, the H _a compared to Sr ferrite The value is 10% or higher.

However, CaLaCo ferrite, although having a H _A above the SrLaCo ferrite, B _r and H _cJ are comparable to SrLaCo ferrite, while the H _k / H _cJ is very poor, high H _cJ and high H _k / _HcJ cannot be satisfied, and it has not yet been applied to various applications such as motors.

  Various proposals have been made to improve the magnetic properties of CaLaCo ferrite. For example, Japanese Patent Laid-Open No. 2006-104050 proposes a CaLaCo ferrite in which the atomic ratio and molar ratio n of each constituent element are optimized, and La and Co are contained at a specific ratio. / 060757 proposes CaLaCo ferrites in which part of Ca is replaced by La and Ba, and International Publication No. 2007/077811 proposes CaLaCo ferrites in which part of Ca is replaced by La and Sr. Yes.

  However, the CaLaCo ferrite described in JP-A-2006-104050, International Publication No. 2007/060757 and International Publication No. 2007/077811 are all magnetic properties compared to the CaLaCo ferrite proposed in Patent No. 3181559. Although it has been improved, it is insufficient to meet the demand for higher performance in recent years, and further improvement in magnet characteristics is desired.

International Publication No. 2011/001831 is a CaLaCo ferrite proposed in JP 2006-104050 A, International Publication No. 2007/060757 and International Publication No. 2007/077811. , 1.8 mass% of SiO _2, and by adding CaCO ₃ 1-2% by weight calcined body in terms of CaO, while preventing a decrease in B _r and H _k / H _cJ as much as possible, the H _cJ A specially improved CaLaCo ferrite is proposed.

CaLaCo ferrite containing a relatively large amount of sintering aid proposed in International Publication No. 2011/001831 improves H _cJ specifically, but most of them have H _cJ of 360 kA / m (about 4.5 _k If it exceeds kOe), H _k / H _cJ is reduced to less than 85%, and it cannot be said that it is sufficient to cope with the thinning of the sintered ferrite magnet that has been requested in recent years.

Accordingly, an object of the present invention, in the CaLaCo ferrite, high and B _r and a high H _k / H _cJ while H _cJ was maintained with improved useful ferrite compound as a compound of the ferrite sintered magnet that can respond to thinning Is to provide.

As a result of diligent research in view of the above object, the inventors have found a ferrite compound having an M-type magnetoplumbite structure in which part of the site occupied by Fe or Co is replaced by Ca in the crystal structure of CaLaCo ferrite. . Then, it found that ferrite sintered magnet that the crystal phase (ferrite phase) the main phase composed of the ferrite compound, has a high H _cJ with a high B _r and a high H _k / H _cJ, completed the present invention did.

That is, the ferrite compound of the present invention is a ferrite compound having a hexagonal M-type magnetoplumbite structure and containing Ca, La, Fe and Co as essential components,
The total amount of Ca present in 2a, 4e, 4f ₁ , 4f ₂ and 12k sites in the unit cell of the M-type magnetoplumbite structure is 0.05 or more per unit cell.

The ferrite compound has a composition formula showing the atomic ratio of the metal elements of A, Fe, and Co which are Ca, La, Ba and / or Sr: Ca _1-xy La _x A _y Fe _2n-zw Co _z Ca _w 1-xy, x, y, z, w, and n indicating a molar ratio are
0.23 ≦ (1-x-y + w) / (1 + w) ≦ 0.75,
0.2 ≦ x / (1 + w) ≦ 0.65,
0 ≦ y / (1 + w) ≦ 0.4,
0.2 ≦ z / (1 + w) <0.65,
w ≧ 0.025
3 <n / (1 + w) <6 and
0 ≦ y / (1-x + w) <0.56
Is preferably satisfied.

  The ferrite compound is obtained by pulverizing a calcined body obtained by calcining raw material powder, a temperature rising rate in a temperature range of 1100 ° C. to firing temperature is 1 to 4 ° C./min, and a temperature range of firing temperature to 1100 ° C. It is preferable to be produced by firing at a temperature lowering rate of 6 ° C./min or more.

Since the ferrite compound according to the present invention has high saturation magnetization and high _HA , it can exhibit high performance when used in a sintered magnet, a bonded magnet, a magnetic recording medium or the like. Especially when used as the main compound constituting the ferrite sintered magnet, with improved H _cJ while maintaining high B _r and a high H _k / H _cJ, sintered ferrite magnets which can respond to thinning is obtained, this By using a ferrite sintered magnet, it is possible to provide various electric motor parts such as various motors, generators, and speakers, electric equipment parts, and the like that are reduced in size, weight, and efficiency.

It is a graph showing the relationship between the heating rate and B _r in the firing step of the sintered ferrite magnet of the sample No.1~8 of Example 1 (closed circles) and H _cJ (black triangles). 6 is a graph showing the relationship between the temperature increase rate and H _k / H _cJ in the firing step of the ferrite sintered magnets of Sample Nos. 1 to 8 in Example 1. FIG. It is a graph showing the relationship between the cooling rate and the B _r and H _cJ in the firing step of the sintered ferrite magnet of the sample No.9~13 of Example 1 (closed circles) and sample Nanba14～18 (black triangles). 4 is a graph showing the relationship between the temperature drop rate and H _k / H _cJ in the firing process of ferrite sintered magnets of Sample Nos. 9 to 13 (black circles) and Sample Nos. 14 to 18 (black triangles) of Example 1. FIG. It is a graph showing the relationship between the heating rate and B _r in the firing step of the sintered ferrite magnet of the sample No.19~26 of Example 1 (closed circles) and H _cJ (black triangles). 4 is a graph showing the relationship between the temperature increase rate and H _k / H _cJ in the firing step of the ferrite sintered magnets of Sample Nos. 19 to 26 in Example 1. FIG.

[1] Ferrite compound The ferrite compound of the present invention has a hexagonal M-type magnetoplumbite structure,
A ferrite compound containing Ca, La, Fe and Co as essential components,
The total amount of Ca present in 2a, 4e, 4f ₁ , 4f ₂ and 12k sites in the unit cell of the M-type magnetoplumbite structure is 0.05 or more per unit cell.

  The ferrite compound of the present invention has a hexagonal M-type magnetoplumbite structure. “Having hexagonal M-type magnetoplumbite structure” means that a ferrite sintered magnet or ferrite powder containing a crystal phase (ferrite phase) composed of the ferrite compound of the present invention is used in a general X-ray diffraction method. It means that an X-ray diffraction pattern of a hexagonal M-type magnetoplumbite structure is mainly observed when measured under conditions.

M-type magnetoplumbite structure hexagonal is a complex crystal structure, when the Sr ferrite, 2d that Sr occupies, 2a that Fe occupies, 4e, 4f _1, 4f ₂ and 12k, and O (oxygen) It has 11 different sites, 4e, 4f, 6h, 12k ₁ and 12k _{2 to} occupy. The number of chemical formula units per unit cell is 2, that is, it contains two chemical formula atoms per unit cell. For example, in the case of Sr ferrite (chemical formula is SrFe ₁₂ O ₁₉ ), 2 Sr, 24 Fe, and 38 O are contained per unit cell.

In the above SrLaCo ferrite, La is present on a part of the 2d site (Sr site), Co is _{2a, 4e, 4f 1, 4f} 2 and 12k site (Fe site) it is known to exist in the part of (See, for example, J. Ceram. Soc. Jpn., 119 (2011) 285-290). Also, in the CaLaCo ferrite described above, like SrLaCo ferrite, Ca and La are present in part of the 2d site, and Co is present in part of the 2a, 4e, 4f ₁ , 4f ₂ and 12k sites. The composition of the conventional ferrite sintered magnet is designed based on such a concept. These are apparent from the composition formulas described in JP-A-2006-104050, International Publication No. 2007/060757, International Publication No. 2007/077811, and the like.

In CaLaCo ferrite, Sr (ion radius of Sr ²⁺ in 144 coordination: 144 pm) and Ba (ion radius of Ba ²⁺ in 161 coordination: 161 pm) are occupied by conventional Sr ferrite and Ba ferrite. In some sites, Ca (12-coordinate Ca ²⁺ ion radius: 134 pm, 6-coordinate ion radius: 100 pm) and La (12-coordinate La ³⁺ ion radius: 136 pm) is replaced, Fe (the Fe ³⁺ in the six-coordinate ion radius: 64.5 pm) of Co ²⁺ in Co (6 coordinated to some sites occupied ionic radius: 74.5 pm) is substituted Therefore, it is considered that a large strain is generated in the crystal structure of the M-type magnetoplumbite compared to the unsubstituted Sr ferrite and Ba ferrite. In addition, in CaLaCo ferrite, the amount of substitution of trivalent La ions for divalent Ca ions and the amount of substitution of divalent Co ions for trivalent Fe ions are significantly different, resulting in an imbalance in the charge balance of the entire crystal. Therefore, it is necessary to maintain the charge balance of the entire crystal by some method. For this reason, the crystal structure of CaLaCo ferrite is more unstable than Sr ferrite and SrLaCo ferrite.

In the ferrite compound of the present invention, the total amount of Ca present in the 2a, 4e, 4f ₁ , 4f ₂ and 12k sites in the unit cell of the M-type magnetoplumbite structure is 0.05 or more per unit cell. That is, 0.05 or more of the sites where 24 Fe and Co exist per unit cell are substituted with Ca. By substituting a part of the Fe site with Ca, it is considered that the distortion of the crystal structure and the imbalance of the charge balance are alleviated and the crystal structure as the M-type magnetoplumbite structure is stabilized.

The total amount of Ca present in the 2a, 4e, 4f ₁ , 4f ₂ and 12k sites in the unit cell of the M-type magnetoplumbite structure should be analyzed by the profile fitting method of diffraction patterns by X-ray diffraction or neutron diffraction. Can do. X-ray diffraction can be performed using a synchrotron radiation facility such as SPring-8 or a commercially available powder X-ray diffractometer, and neutron diffraction can be performed using a facility such as JRR-3 of the Japan Atomic Energy Agency. Can do.

  As a profile fitting method used in the analysis of a diffraction pattern by X-ray diffraction or neutron diffraction, for example, a Rietveld analysis method can be cited. Rietveld analysis is performed by fitting a diffraction pattern calculated from the crystal structure of a substance expected to be contained in a sample to a diffraction pattern obtained by X-ray diffraction, etc. This is a method of analyzing coordinates, types of atoms occupying each site, and occupancy rates. Lead belt analysis software includes commercially available software such as TOPAS (manufactured by Bruker AXS), and RIETAN-FP (F. Izumi and K. Momma, “Three-dimensional visualization in powder diffraction,” Solid State Phenom., 130, 15-20 (2007).). As the crystal structure of the constituent phase, a known structure may be used as the initial structure.

The present invention relates to an improvement of CaLaCo ferrite, and the ferrite compound of the present invention contains Ca, La, Fe and Co as essential components. Preferably, Ca, La, A element is Ba and / or Sr, the composition formula represents an atomic ratio of metal elements of Fe and Co: in _{Ca 1-xy La x A y} Fe 2n-zw Co z Ca w, wherein 1-xy, x, y, z, w, and n indicating the molar ratio are
0.23 ≦ (1-x-y + w) / (1 + w) ≦ 0.75,
0.2 ≦ x / (1 + w) ≦ 0.65,
0 ≦ y / (1 + w) ≦ 0.4,
0.2 ≦ z / (1 + w) <0.65,
w ≧ 0.025,
3 <n / (1 + w) <6 and
0 ≦ y / (1-x + w) <0.56
Is satisfied.

The above composition formula is shown by the atomic ratio of the metal element, but the composition containing oxygen (O) can be represented by the composition formula: Ca _1-xy La _x A _y Fe _{2 n -zw} Co _z Ca _w O _α (where 1 -xy, x, y, z, w and α and n indicating the molar ratio are
0.23 ≦ (1-x-y + w) / (1 + w) ≦ 0.75,
0.2 ≦ x / (1 + w) ≦ 0.65,
0 ≦ y / (1 + w) ≦ 0.4,
0.2 ≦ z / (1 + w) <0.65,
w ≧ 0.025,
3 <n / (1 + w) <6 and
0 ≦ y / (1-x + w) <0.56
When La and Fe are trivalent, Ca, A element and Co are divalent, and when x = w + z and a stoichiometric composition ratio when n = 6, α = 19 is there. ).

  In the composition of the ferrite compound containing oxygen (O), the atomic ratio of oxygen varies depending on the valence of Fe and Co, the n value, and the like. In the ferrite compound, the ratio of oxygen to the metal element changes due to oxygen vacancies when baked in a reducing atmosphere, changes in the valence of Fe in the ferrite compound, changes in the valence of Co, and the like. Therefore, the actual atomic ratio α of oxygen may deviate from 19. Therefore, in the present invention, the composition is expressed by the atomic ratio of the metal element whose composition is most easily specified.

The ferrite compound of the present invention is the main component of a sintered ferrite magnet, that is, the crystal phase (ferrite phase having a hexagonal M-type magnetoplumbite structure) composed of the ferrite compound of the present invention is the main phase. it is thus possible to obtain a ferrite sintered magnet with improved H _cJ while maintaining high B _r and a high H _k / H _cJ. Hereinafter, a ferrite sintered magnet having a crystal phase composed of the ferrite compound of the present invention as a main phase (hereinafter sometimes referred to as “the present ferrite sintered magnet”) will be described.

  As described above, the main phase of the sintered ferrite magnet is a crystal phase composed of the ferrite compound of the present invention, and is a ferrite phase having a hexagonal M-type magnetoplumbite structure. In general, a magnetic material, particularly a sintered magnet, is composed of a plurality of compounds, and a compound that determines the characteristics (physical properties, magnet characteristics, etc.) of the magnetic material is defined as “main phase”. The main phase in the sintered ferrite magnet, that is, a ferrite phase having a hexagonal M-type magnetoplumbite structure also determines basic parts such as physical properties and magnet characteristics of the sintered ferrite magnet.

  In addition to the main phase, the ferrite sintered magnet further includes a first grain boundary phase existing between two main phases and a second grain boundary phase existing between three or more main phases. Contained. The first grain boundary phase existing between the two main phases is a grain boundary phase that is also referred to as a “two-grain grain boundary phase” by those skilled in the art, and is obtained when an arbitrary cross section of a ferrite sintered magnet is observed. This refers to the grain boundary phase that appears linearly at the grain boundaries of the main phase and the main phase. Further, the second grain boundary phase existing between three or more main phases is a grain boundary phase referred to as “multi-point grain boundary phase” by those skilled in the art, and an arbitrary cross section of the ferrite sintered magnet. Is a grain boundary phase that appears between three or more main phases and looks like a substantially triangular shape, a substantially polygonal shape, or an indefinite shape. Since the first grain boundary phase is very thin and difficult to observe with an X-ray diffraction pattern, it is preferably confirmed with a transmission electron microscope or the like having high resolution. In the following description, when the first grain boundary phase and the second grain boundary phase are collectively expressed, they may be simply referred to as “grain boundary phase”.

The sintered ferrite magnet has the main phase, the first grain boundary phase, and the second grain boundary phase, and preferably the second grain boundary phase is scattered in an arbitrary cross section. And the average area of the second grain boundary phase is less than 0.2 μm ² . In a more preferred embodiment, the second grain boundary phase has a structure having 900 or more in a range of 53 × 53 μm ² of an arbitrary cross section. The average area of the second grain boundary phase is obtained by binarizing the reflected electron image (BSE image) of the ferrite sintered magnet cross section by FE-SEM (field emission scanning electron microscope). It can be determined by determining the area and number of phases and dividing the total area by the number.

[2] Method for Producing Ferrite Compound The ferrite compound of the present invention can be formed through the following production steps.
Raw material powder mixing step of mixing raw material powders to obtain mixed raw material powders,
Calcining the mixed raw material powder to obtain a calcined body,
Crushing the calcined body to obtain a calcined powder;
Firing the calcined powder, and including a firing step to obtain a fired body,
In the firing step, the rate of temperature rise in the temperature range of 1100 ° C. to the firing temperature is 1 to 4 ° C./minute, and the temperature drop rate in the temperature range of the firing temperature to 1100 ° C. is 6 ° C./minute or more. In addition, when using the ferrite compound of this invention for a sintered magnet, the shaping | molding process etc. which shape | mold the said calcined body powder and obtain a molded object between the said crushing process and the said baking process are added. Each step will be described below.

(a) Raw material powder mixing step Composition formula indicating the atomic ratio of A element, Fe and Co metal elements in which the ferrite compound is Ca, La, Ba and / or Sr: Ca _1-xy La _x A _y Fe _{2n- In zw} Co _z Ca _w , 1-xy, x, y, z, w, and n indicating a molar ratio are
0.23 ≦ (1-x-y + w) / (1 + w) ≦ 0.75,
0.2 ≦ x / (1 + w) ≦ 0.65,
0 ≦ y / (1 + w) ≦ 0.4,
0.2 ≦ z / (1 + w) <0.65,
w ≧ 0.025
3 <n / (1 + w) <6 and
0 ≦ y / (1-x + w) <0.56
The raw material powder is blended so as to satisfy the above. When n indicating the atomic ratio and molar ratio is outside the above specified range, the ferrite compound of the present invention cannot be obtained.

  Note that La can be partially substituted with at least one rare earth element other than La. The substitution amount is preferably 50% or less of La by molar ratio. A part of Co can be substituted with at least one selected from Zn, Ni and Mn.

Regardless of the valence, the raw material powder can use oxides, carbonates, hydroxides, nitrates, chlorides, and the like of each metal. The solution which melt | dissolved raw material powder may be sufficient. Examples of the Ca compound include Ca carbonate, oxide, chloride and the like. Examples of the La compound include oxides such as La ₂ O ₃ , hydroxides such as La (OH) ₃ , carbonates such as La ₂ (CO ₃ ) ₃ · 8H ₂ O, and the like. Examples of the element A compound include Ba and / or Sr carbonates, oxides, and chlorides. Examples of the iron compound include iron oxide, iron hydroxide, iron chloride, and mill scale. Co compounds include oxides such as CoO and Co ₃ O ₄ , and hydroxides such as CoOOH, Co (OH) ₂ , and Co ₃ O ₄ · m ₁ H ₂ O (m ₁ is a positive number). , Carbonates such as CoCO ₃ , and basic carbonates such as m ₂ CoCO ₃ · m ₃ Co (OH) ₂ · m ₄ H ₂ O (m ₂ , m ₃ and m ₄ are positive numbers) Can be mentioned.

Raw material powders other than CaCO ₃ , Fe ₂ O ₃ and La ₂ O ₃ may be added from the time of raw material mixing, or may be added after calcination. For example, (1) CaCO ₃ , Fe ₂ O ₃ , La ₂ O ₃ and Co ₃ O ₄ are blended, mixed and calcined, and then the calcined body is pulverized and fired to produce a ferrite compound. (2) Mixing CaCO ₃ , Fe ₂ O ₃ and La ₂ O ₃ , mixing and calcining, adding Co ₃ O ₄ to the calcined body, pulverizing and firing to produce a ferrite compound You can also

In order to promote the reaction during calcination, a compound containing B such as B ₂ O ₃ or H ₃ BO ₃ may be added up to about 1% by mass as necessary. 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 firing), both before and after calcination. It may be added.

  Each prepared raw material powder is mixed and it is set as mixed raw material powder. Mixing of the raw material powders may be performed either by a wet method or a dry method. When stirring with a medium such as a steel ball, the raw material powder can be mixed more uniformly. In the case of the wet type, it is preferable to use water as the dispersion medium. For the purpose of enhancing the dispersibility of the raw material powder, a known dispersant such as ammonium polycarboxylate or calcium gluconate may be used. The mixed raw material slurry may be calcined as it is, or after dehydrating the raw material slurry, it may be calcined.

(b) Calcination process The mixed raw material powder obtained by dry mixing or wet mixing is heated using an electric furnace, gas furnace, etc., and by a solid-phase reaction, a hexagonal M-type magnetoplumbite structure The ferrite compound is formed. This process is called “calcination” and the resulting compound is called “calcination”. The ferrite compound formed by calcination is a precursor of the ferrite compound of the present invention, and at this stage, the crystal structure is not sufficiently stabilized, and 2a in the unit cell of the M-type magnetoplumbite structure , 4e, 4f ₁ , 4f ₂ and 12k sites, the total amount of Ca may not be 0.05 or more per unit cell.

  The calcination step is preferably performed in an atmosphere having an oxygen concentration of 5% or more. When the oxygen concentration is less than 5%, abnormal grain growth, generation of a heterogeneous phase, and the like are caused. A more preferable oxygen concentration is 20% or more.

  In the calcination step, a solid phase reaction in which a ferrite compound is formed proceeds with an increase in temperature and is completed at about 1100 ° C. A calcination temperature of less than 1100 ° C. is not preferable because unreacted hematite (iron oxide) remains. On the other hand, when the calcining temperature exceeds 1450 ° C., crystal grains grow too much, and thus, it may take a long time for the grinding in the grinding process. Accordingly, the calcination temperature is preferably 1100 to 1450 ° C, more preferably 1200 to 1350 ° C. The calcination time is preferably 0.5 to 5 hours.

When H ₃ BO ₃ is added before calcination, the ferritization reaction is promoted, and therefore calcination can be performed at 1100 ° C. to 1300 ° C.

(c) Addition of sintering aid When the ferrite compound of the present invention is used in a sintered magnet, a calcined body or a calcined body is used as a sintering aid after the calcining step and before the molding step described later. It is preferable to add 0 to 1.8% by mass of SiO ₂ and 0 to 2% by mass of CaCO ₃ in terms of CaO with respect to 100% by mass of the calcined body or the calcined body powder. For example, the sintering aid may be added by, for example, adding a sintering aid to the calcined body obtained by the calcining step and then performing a grinding step, adding a sintering aid during the grinding step, or grinding. A method of adding a sintering aid to the calcined body after the process and mixing and then performing a molding process can be employed.

In the present invention, the amount of CaCO ₃ added is all expressed in terms of CaO. The addition amount of CaCO ₃ from the addition amount in terms of CaO is calculated by the formula:
(Molecular weight of CaCO ₃ × added amount in terms of CaO) / CaO molecular weight.
For example, when adding 1.5% CaCO ₃ in terms of CaO,
{(40.08 [Ca atomic weight] + 12.01 [C atomic weight] + 48.00 [O atomic weight x 3] = 100.09 [CaCO ₃ molecular weight]) x 1.5 mass% [CaO equivalent amount]} / ( 40.08 [atomic weight of Ca] +16.00 [atomic weight of O] = 56.08 [molecular weight of CaO] = 2.677 mass% [addition amount of CaCO ₃ ].

Since CaLaCo ferrite contains Ca as a main phase component, a liquid phase can be generated and sintered without adding SiO ₂ and CaCO ₃ as sintering aids. That is, the grain boundary phase is formed without adding the SiO ₂ and CaCO ₃ that mainly form the grain boundary phase in the ferrite sintered magnet. On the other hand, when SiO ₂ and CaCO ₃ are added as sintering aids, they become part of the liquid phase component during sintering and become a grain boundary phase after sintering.

In addition to the above-described SiO ₂ and CaCO ₃ , Cr ₂ O ₃ , Al ₂ O _3, etc. can be added after the calcining step and before the molding step described later. Each of these addition amounts is preferably 5% by mass or less.

(d) Grinding step The calcined body is pulverized by a vibration mill, ball mill, attritor or the like to obtain a calcined powder. The average particle size of the calcined powder is preferably about 0.4 to 0.8 μm (air permeation method). The pulverization step may be either dry pulverization or wet pulverization, but is preferably performed in combination.

  The wet pulverization is performed using water and / or a non-aqueous solvent (an organic solvent such as acetone, ethanol, xylene) as a dispersion medium. By wet pulverization, a slurry in which the dispersion medium and the calcined powder are mixed is generated. It is preferable to add a known dispersant and / or surfactant to the slurry in a solid content ratio of 0.2 to 2% by mass. After the wet pulverization, it is preferable to concentrate and knead the slurry.

The pulverized calcined powder contains ultrafine powder of less than 0.1 μm, which causes abnormal grain growth of ferrite particles generated in the firing process, dehydration deterioration in the molding process, and molding defects. It is preferable to heat-treat the pulverized calcined powder to remove the heat. The heat-treated powder is preferably pulverized again. Thus, from the first fine pulverization step, the step of heat-treating the powder obtained by the first fine pulverization step, and the second fine pulverization step of pulverizing the powder subjected to the heat treatment again When the ferrite compound of the present invention is used for a sintered magnet by adopting a pulverization step (hereinafter referred to as “heat treatment re-pulverization step”), the H _cJ of the ferrite sintered magnet can be improved.

In the normal pulverization process, ultrafine powder of less than 0.1 μm is inevitably generated, and the presence of the ultrafine powder causes abnormal grain growth of ferrite particles in the firing process, resulting in a decrease in H _cJ , and dehydration in the molding process. It becomes worse, the molded product becomes defective, or the press cycle is lowered due to a long time for dehydration. When heat treatment is performed on the powder containing the ultrafine powder obtained by the first fine pulverization step, a reaction occurs between the powder having a relatively large particle size and the ultrafine powder, and the amount of the ultrafine powder can be reduced. Then, the particle size is adjusted and necking is removed by the second pulverization step to produce a powder having a predetermined particle size. Thereby, when the ferrite compound of the present invention is used for a sintered magnet by reducing the amount of ultrafine powder and obtaining a powder having excellent particle size distribution, and suppressing abnormal grain growth of ferrite particles in the firing step, It is possible to improve the _HcJ of the present sintered ferrite magnet and solve the above problems in the molding process.

If the effect of improving H _cJ by the heat treatment re-grinding process is used, even if the particle size of the powder by the second pulverization process is set relatively large (for example, an average particle size of about 0.8 to 1.0 μm (air permeation method)), usually H _cJ equivalent to the case of using the powder obtained by the pulverization step (average particle size of about 0.4 to 0.8 μm (air permeation method)) is obtained. Therefore, the time for the second pulverization step can be shortened, and further improvement of dewaterability and improvement of the press cycle can be achieved.

  As described above, according to the heat treatment re-pulverization process, although various advantages can be obtained, an increase in cost accompanying an increase in the manufacturing process cannot be avoided. However, the improvement effect obtained when the heat treatment re-pulverization step is adopted is much larger than that when the heat treatment re-pulverization step is not adopted, so that the cost increase can be offset. Therefore, in the present invention, the heat treatment re-pulverization step is a practically meaningful step.

  The first fine pulverization is the same as the normal pulverization described above, and is performed using a vibration mill, a jet mill, a ball mill, an attritor or the like. The average particle size of the pulverized powder is preferably about 0.4 to 0.8 μm (air permeation method). The pulverization step may be either dry pulverization or wet pulverization, but is preferably performed in combination.

  The heat treatment performed after the first pulverization step is preferably performed at 600 to 1200 ° C, more preferably 800 to 1100 ° C. The heat treatment time is not particularly limited, but is preferably 1 second to 100 hours, and more preferably about 1 to 10 hours.

  The second fine pulverization performed after the heat treatment step is performed using a vibration mill, a jet mill, a ball mill, an attritor or the like as in the first fine pulverization. Since almost the desired particle size has already been obtained in the first pulverization step, particle size adjustment and necking removal are mainly performed in the second pulverization step. Therefore, it is preferable to reduce the pulverization conditions by shortening the pulverization time or the like than the first fine pulverization step. If pulverization is performed under the same conditions as in the first pulverization step, ultrafine powder is generated again, which is not preferable.

The average particle size of the powder after the second fine pulverization is about 0.4 to 0.8 μm (air) as in the normal pulverization step when it is desired to obtain a higher H _cJ than the sintered ferrite magnet obtained by the normal pulverization step. The permeation method is preferred, and if you want to take advantage of the shortening of the pulverization process, further improvement of dewaterability, improvement of the press cycle, etc., 0.8 to 1.2 μm, preferably about 0.8 to 1.0 μm (air permeation method) ) Is preferable.

(e) Forming Step When the ferrite compound of the present invention is used for a sintered magnet, the slurry after the pulverizing step is press-molded in a magnetic field or in a non-magnetic field while removing the dispersion medium. In particular, by press molding in a magnetic field, the crystal orientation of the powder particles can be aligned (orientated), and the magnet characteristics of the ferrite sintered magnet can be dramatically improved. Further, in order to improve the orientation, 0.01% to 1% by mass of a dispersant and a lubricant may be added. Moreover, you may concentrate a slurry before shaping | molding as needed. Concentration is preferably carried out by natural sedimentation, centrifugation, filter press or the like.

(f) Firing step The calcined body powder obtained in the pulverization step or the shaped body obtained in the molding step is degreased if necessary and then fired (sintered). Thus, a fired body (sintered magnet) is obtained. In the firing step, the rate of temperature rise in the temperature range of 1100 ° C. to the firing temperature is 1 to 4 ° C./minute, and the temperature drop rate in the temperature range of the firing temperature to 1100 ° C. is 6 ° C./minute or more. This produces a ferrite compound in which the total amount of Ca present in the 2a, 4e, 4f ₁ , 4f ₂ and 12k sites in the unit cell of hexagonal M-type magnetoplumbite structure is 0.05 or more per unit cell. be able to.

  It is possible to obtain the ferrite compound of the present invention even at a heating rate of less than 1 ° C / minute, for example, 0.5 ° C / minute. However, if the heating rate is too slow, the production cycle becomes longer and the production cost increases. This is not preferable. Therefore, the temperature rising rate is preferably 1 to 4 ° C./min. A more preferable rate of temperature increase is 1 to 2 ° C./min. Further, the upper limit is not particularly defined if the temperature lowering rate is 6 ° C./min or more, but in order to lower the temperature quickly, a cooling facility and a blower facility are required in the firing furnace, which may increase the production cost. Considering these points, the upper limit of the temperature lowering rate is preferably about 10 ° C./min.

  The temperature range in which the heating rate is 1 to 4 ° C./min is 1100 ° C. to the firing temperature. If the rate of temperature rise exceeds 4 ° C./min even in the temperature range of 1100 ° C. or higher, the ferrite compound of the present invention may not be obtained. In addition, if the temperature increase rate in the temperature range of 1100 degreeC-calcination temperature is 1-4 degreeC / min, the temperature increase rate in other temperature will not be specifically limited. In order to set the rate of temperature increase in the temperature range from 1100 ° C. to the firing temperature to 1 to 4 ° C./min, the temperature increase rate is set to 1 to 1 even at a temperature lower than 1100 ° C. It is preferable to keep it at 4 ° C / min.

  The temperature range in which the rate of temperature decrease is 6 ° C./min or more is the firing temperature to 1100 ° C. If the temperature lowering rate temporarily becomes less than 6 ° C./min in the temperature range of 1100 ° C. or higher, the ferrite compound of the present invention may not be obtained. In addition, if the temperature-fall rate in the temperature range of calcination temperature-1100 degreeC is 6 degrees C / min or more, the temperature-fall rate in temperature other than that will not be specifically limited.

  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% or more. If the oxygen concentration is less than 10%, abnormal grain growth or heterogeneous phase formation may occur, making it difficult to use for sintered magnets, bonded magnets, magnetic recording media, and the like. The oxygen concentration is more preferably 20% or more, and most preferably 100%. The firing temperature is preferably 1150 to 1250 ° C. The firing time is preferably 0.5 to 2 hours. The average crystal grain size of the fired body (sintered magnet) obtained by the firing process is about 0.5 to 2 μm.

  The fired body obtained by the firing step is pulverized (pulverized) as necessary to obtain a powder mainly containing a crystal phase composed of the ferrite compound of the present invention, and a bonded magnet, a magnetic recording medium, etc. These performances can be improved by using them in the above. Moreover, the sintered magnet obtained by the said baking process after performing the said shaping | molding process can be used as a ferrite sintered magnet as it is. That is, the sintered ferrite magnet has a crystal composed of the ferrite compound of the present invention (a ferrite phase having a hexagonal M-type magnetoplumbite structure) as a main phase.

The feature of the method for producing a ferrite compound of the present invention is that, in the firing (sintering) step, the rate of temperature increase from 1100 ° C. to the firing temperature is slowed (1 to 4 ° C./min), and the firing temperature after firing is 1100 ° C. It is in the point which makes the temperature-falling speed until it is faster than the temperature-raising speed (more than 6 ℃ / min). As a result, a ferrite compound in which the total amount of Ca present in the 2a, 4e, 4f ₁ , 4f ₂ and 12k sites in the unit cell of the hexagonal M-type magnetoplumbite structure is 0.05 or more per unit cell is obtained. can be, in the ferrite sintered magnet of the ferrite compound as the main constituent, it is possible to improve the H _cJ while maintaining high B _r and a high H _k / H _cJ. The reason for the estimation by the present inventors will be described below, but this reason is estimated from the knowledge obtained at the present time, and is not intended to limit the technical scope of the present invention.

The general firing process of sintered ferrite magnets is classified as liquid phase sintering. In the above-described method for producing a ferrite compound according to the present invention, when SiO ₂ and CaCO ₃ are added as sintering aids, the sintering aid becomes part of the liquid phase component during firing, and no sintering aid is added. In some cases, a part of the main phase forms a liquid phase during firing. These liquid phases become a first grain boundary phase existing between two main phases and a second grain boundary phase existing between three or more main phases after firing.

In the method for producing a ferrite compound of the present invention, the heating rate in the temperature range from 1100 ° C. to the firing temperature is 1 to 4 ° C./min, and the solid phase into the liquid phase is slowly passed through the temperature range. In addition to promoting dissolution and precipitation, each atom moves to a position that stabilizes the crystal structure in the crystal of the M-type magnetoplumbite structure. As a result, more than 0.05 of the sites occupied by 24 Fe and Co per unit cell of the M-type magnetoplumbite structure are replaced by Ca, that is, in the unit cell of the M-type magnetoplumbite structure. The total amount of Ca present in 2a, 4e, 4f ₁ , 4f ₂ and 12k sites is 0.05 or more per unit cell. Thereby, it is considered that the distortion of the crystal structure and the imbalance of the charge balance are alleviated, and the crystal structure as the M-type magnetoplumbite structure is stabilized.

  However, when the temperature is lowered after firing, if the temperature range from 1100 ° C to the firing temperature is passed slowly as in the case of the temperature rise, the solid phase dissolves and precipitates again in the liquid phase, and the M-type magnetoplumbite structure. The movement of atoms in the crystal occurs, and the stabilized crystal structure is broken. Therefore, it is considered that the stable crystal structure formed at the time of temperature rise can be maintained as it is by passing the temperature range quickly by setting the temperature drop rate in the temperature range of the firing temperature to 1100 ° C to 6 ° C / min or more. It is done.

  It is considered that the dissolution and precipitation of the solid phase in the liquid phase and the movement of atoms in the crystal of the M-type magnetoplumbite structure occur not only in the CaLaCo ferrite but also in the SrLaCo ferrite in the firing process. However, CaLaCo ferrite and SrLaCo ferrite differ greatly in the following points.

As described above, in CaLaCo ferrite, when SiO ₂ and CaCO ₃ are added as sintering aids, the sintering aid forms a liquid phase during firing, and when no sintering aid is added, one of the main phases. The part forms a liquid phase during firing. That is, Ca is contained in both the main phase and the liquid phase. In the firing step, when the solid phase is dissolved and precipitated in the liquid phase, it is considered that Ca contained in the main phase and Ca contained in the liquid phase move with each other. That is, the mutual movement of Ca between the main phase and the liquid phase promotes the dissolution and precipitation of the solid phase into the liquid phase, and as a result, the Ca to some of the sites occupied by Fe or Co in the crystal structure of CaLaCo ferrite. It is thought that the replacement of is promoted.

On the other hand, SrLaCo ferrite basically does not contain Ca in the main phase. Therefore, during firing, SiO ₂ and CaCO ₃ added as a sintering aid will mainly form a liquid phase, and unlike CaLaCo ferrite, if no sintering aid is added, a preferred firing temperature around 1200 ° C. In the range, almost no liquid phase is formed. The inventors scanned and transmitted the composition of any three grain boundary phases in a SrLaCo ferrite sintered magnet (added 1.2% by mass of SiO ₂ as a sintering aid and 1.5% by mass of CaCO ₃ in terms of CaO). When a point analysis was performed with a scanning electron microscope (STEM) and an FE-TEM equipped with an energy dispersive X-ray spectroscopy (EDS) function, the results shown in Table 1 were obtained. The unit of content is atomic%.

table 1

  As shown in Table 1, the grain boundary phase of the SrLaCo ferrite sintered magnet contains Sr, La, and Fe in addition to Si and Ca added as a sintering aid. From this result, it is considered that in the SrLaCo ferrite, when the solid phase is dissolved and precipitated in the liquid phase, the main phase is dissolved and the main phase component is moved to the liquid phase.

  It has been found that the stability of the crystal structure having a hexagonal M-type magnetoplumbite structure is Sr ferrite> SrLaCo ferrite> CaLaCo ferrite. As described above, in CaLaCo ferrite, it is considered that Ca contained in the main phase and Ca contained in the liquid phase are mutually moved. The crystal structure of CaLaCo ferrite is different from that of Sr ferrite and SrLaCo ferrite. Another factor is the instability. Therefore, in SrLaCo ferrite with a stable crystal structure, the main phase dissolves and the main phase component may move to the liquid phase, but the liquid phase component does not move to the main phase. . That is, it is unlikely that a stable SrLaCo ferrite phase will take Ca into an unstable state. Therefore, in SrLaCo ferrite, there is no mutual movement between the main phase and the liquid phase when the solid phase dissolves and precipitates in the liquid phase, and the main phase components Sr and La move unilaterally to the liquid phase. It is thought that there is. The main phase components Sr and La are dissolved in the liquid phase, that is, Sr and La are eluted from the outer shell of the main phase, leaving a spinel structure with low crystal magnetic anisotropy. This is considered to be a factor that decreases the directivity.

  Also in the ferrite compound of the present invention, the component of the ferrite compound moves to the grain boundary phase (liquid phase) in the production process. However, as described above, CaLaCo ferrite contains Ca in both the ferrite compound and the liquid phase, and the mutual movement of Ca between the ferrite compound and the liquid phase promotes dissolution and precipitation of the solid phase in the liquid phase. Therefore, it is considered that the crystal structure is stabilized.

  Thus, it is considered that different phenomena occur in CaLaCo ferrite and SrLaCo ferrite when the solid phase dissolves and precipitates in the liquid phase. Therefore, in the SrLaCo ferrite, like the ferrite compound of the present invention, 0.05 or more of sites occupied by 24 Fe and Co per unit cell of the M-type magnetoplumbite structure are replaced by Ca. It is considered that the crystal structure does not become such, and such a crystal structure is unique to CaLaCo ferrite containing Ca as a main component or more than a certain amount, or appears to be remarkable in CaLaCo ferrite.

  Examples in which the ferrite compound of the present invention is the main constituent of a sintered ferrite magnet will be described below, but the present invention is not limited thereto.

Example 1
In the composition formula representing the atomic ratio of metal elements: Ca _1-xy La _x A _y Fe _2n-zw Co _z Ca _w , (1-x-y + w) / (1 + w) = 0.5, x / (1 + w) = 0.5, y / (1 + w) = 0, y / (1-x + w) = 0, z / (1 + w) = 0.3, n / (1 + w) = 5.2 and w = Prepare a raw material powder composed of CaCO ₃ powder, La (OH) ₃ powder, Fe ₂ O ₃ powder and Co ₃ O ₄ powder so that it becomes 0.1, mix in a wet ball mill for 4 hours, dry and adjust. Grained. Subsequently, it was calcined at 1300 ° C. for 3 hours in the atmosphere, and the obtained calcined body was coarsely pulverized with a hammer mill to obtain a coarsely pulverized powder.

SiO ₂ and CaCO ₃ (CaO equivalent value) shown in Table 2 are added to 100% by mass of the coarsely pulverized powder, and a wet ball mill using water as a dispersion medium has an average particle size of 0.55 μm by the air permeation method. Until finely ground. The obtained finely pulverized slurry is molded at a pressure of about 50 MPa while applying a magnetic field of about 1.3 T so that the pressurizing direction and the magnetic field direction are parallel while removing the dispersion medium. A molded body (the axial direction is the magnetic field direction) was obtained.

  The obtained molded body was placed in a firing furnace and fired in the air at a temperature rising rate and a temperature falling rate shown in Table 2 to obtain sintered ferrite magnets (Sample Nos. 1 to 26). The temperature increase rate and temperature decrease rate described in Table 2 indicate the temperature increase rate from 1100 ° C to 1210 ° C (firing temperature) and the temperature decrease rate from 1210 ° C (calcining temperature) to 1100 ° C, respectively. Firing was performed at 1210 ° C. (firing temperature) for 1 hour. The temperature was raised from room temperature to 1100 ° C. at 7.5 ° C./min, and the cooling from 1100 ° C. to room temperature was performed by turning off the firing furnace and opening the firing furnace door.

注1：1100℃から1210℃（焼成温度）までの昇温速度
注2：1210℃（焼成温度）から1100℃までの降温速度Table 2

Note 1: Temperature increase rate from 1100 ° C to 1210 ° C (firing temperature) Note 2: Temperature decrease rate from 1210 ° C (firing temperature) to 1100 ° C

The measurement results of the B _r and H _cJ of the sintered ferrite magnet of the sample No.1~8 Figure 1 shows the results of measurement of H _k / H _cJ in FIG. In Figure 1, a plot of black circles shows the value of B _r, plots of black triangles indicates a value of H _cJ. In H _k / H _cJ , H _k is the value of H at the position where J becomes 0.95J _r in the second quadrant of the J (magnetization magnitude) -H (magnetic field strength) curve ( The same shall apply hereinafter.

The measurement results of the B _r and H _cJ of the sintered ferrite magnet of the sample No.9~18 3 shows the results of measurement of H _k / H _cJ in FIG. 3, the solid line represents the value of B _r, the dotted line indicates the value of H _cJ. 3 and 4, the black circle plot is a sample (No. 9 to 13) with a heating rate of 1 ° C./min, and the black triangle plot is a sample with a heating rate of 4 ° C./min (No. 14 to 18). ).

The measurement results of the B _r and H _cJ of the sintered ferrite magnet of the sample No.19~26 5 shows the results of measurement of H _k / H _cJ in FIG. 5, a plot of black circles shows the value of B _r, plots of black triangles indicates a value of H _cJ.

As shown in FIG. 1 and FIG. 2, in the sample (No. 1 to 8) to which 0.6% by mass of SiO ₂ and 0.7% by mass of CaCO ₃ in terms of CaO were added, the heating rate was 1 to 4 ° C./min. when the range, although B _r and H _k / H _cJ is reduced slightly, H _cJ has significantly improved, H _k / H _cJ was in a 85% or more.

As shown in FIG. 3 and FIG. 4, 0.6% by mass of SiO ₂ and 0.7% by mass of CaCO ₃ in terms of CaO are added, and the temperature rise rate is 1 ° C./min. sample heating rate is 4 ° C. / min (No.14~18), upon the temperature decrease rate and 6 ° C. / min or more, B _r is slightly improved, H _cJ was significantly improved. Further, H _k / H _cJ was maintained at 85% or more. Overall B _r and H _k / H _cJ is than the heating rate towards 1 ° C. / min sample heating rate (No.9~13) is 4 ° C. / min sample (No.9~13) It was slightly higher.

As shown in FIG. 5 and FIG. 6, in the sample (No. 19 to 26) to which 1.2% by mass of SiO ₂ and 1.5% by mass of CaCO ₃ in terms of CaO were added, the rate of temperature increase was from 1 ° C./min to 4 ° C./min. when a minute range, decrease in B _r is hardly observed, H _cJ will have significantly has improved, is obtained a very high value ever exceeding 500 kA / m (about 6.3 kOe) It was. H _k / H _cJ was slightly lower than 85%, but remained high.

Next, Samples Nos. 3, 6, 8, 9, 13, and 24 were pulverized to obtain sinterd powder. The obtained sintered powder was filled in a Lindeman glass capillary with an inner diameter of 0.1 mm, and powder X-ray diffraction measurement was performed using a Debye-Scherrer camera installed in BL19B2 of SPring-8. The incident X-ray energy was 20 keV, the detector was an imaging plate, the exposure time was 5 minutes, and the measurement temperature was room temperature. The resulting diffraction profile was Rietveld analysis using RIETAN-FP, Fe site unit cell of hexagonal M type magnetoplumbite structure (hereinafter _{M-type) (2a, 4e, 4f 1} , 4f 2 and 12k The total amount of Ca (Ca _Fe ) present on the site) was determined. In this Rietveld analysis, for Ca and La, the occupancy site and the occupancy rate were obtained, but Fe and Co were not distinguished and handled as the same kind of virtual elements.

Analysis of Ca _Fe sample No.3,6,8,9,13 and 24, as well as Ca calculated from Ca _Fe, La, Ba and / or A element is Sr, atomic metal element of Fe and Co Composition formula indicating ratio: 1-xy, x, y, z, w, n, (1-x-y + w) / (1 in Ca _1-xy La _x A _y Fe _2n-zw Co _z Ca _w + w), x / (1 + w), y / (1 + w), z / (1 + w), n / (1 + w) and y / (1-x + w) are shown in Table 3. . From the results of this Rietveld analysis, the type and number of Fe sites where Ca is present and the occupation ratio of Ca at each site cannot be specified as one type, and the sites where Ca is present are 2d and 12k. Or 2d, 2a, and 4e, etc., but the Ca _Fe shown in Table 3 can be obtained for each crystal structure model that can be established from the results of these Rietveld analyses. The average value of the total amount of Ca present at the Fe site in the unit cell of the M-type magnetoplumbite structure is shown. For example, for sample No. 3, there are 16 types of crystal structure models that can be established from the results of Rietveld analysis, and the total amount of Ca present in the Fe site in the unit cell of the M-type structure in each crystal structure model is 0.12-0.14 pieces / uc: a (uc unit cell), 0.14 pieces / uc is these mean value as the value of Ca _Fe.

Table 3

Table 3 (continued)

As shown in Table 3, ferrite sintered magnets of sample Nos. 3, 6, 13 and 24 having a temperature rising rate of 1 to 4 ° C./min and a temperature falling rate of 6 ° C./min or more (examples of the present invention) ), Ca _Fe is 0.14 / uc, 0.12 / uc, 0.14 / uc and 0.07 / uc, respectively. On the other hand, sample No. 8 with a temperature drop rate of 6 ° C./min but a temperature rise rate of 6.67 ° C./min as a comparative example, and sample No. 8 with a temperature rise rate of 1 ° C./min but a temperature drop rate of 1 ° C./min. In .9, it can be seen that Ca _Fe is low at 0.02 / uc and 0.04 / uc, respectively.

As described above, the sintered ferrite magnet of the ferrite compound of the present invention has as a main constituent, since it is possible to improve the H _cJ while maintaining high B _r and a high H _k / H _cJ, sufficient to thinning Yes.

Example 2
In the composition formula representing the atomic ratio of metal elements: Ca _1-xy La _x A _y Fe _2n-zw Co _z Ca _w , n / (1 + w) = 5.3 and Ba as element A (y) in Table 4 As shown, for 100% by mass of coarsely pulverized powder, 0.6% by mass of SiO ₂ and 0.7% by mass of CaCO ₃ in terms of CaO were added, the firing temperature was 1200 ° C., and the heating rate shown in Table 4 And the ferrite sintered magnet of sample No.27-31 was obtained like Example 1 except having set it as the temperature fall rate. Note that BaCO ₃ powder was used as the Ba raw material. B _r of resultant sintered ferrite magnet, the measurement result of H _cJ and H _k / H _cJ shown in Table 5. Further, the analysis results of Ca _Fe obtained by Rietveld analysis in the same manner as in Example 1, and the atomic ratio of the Ca, La, Ba and / or Ba A element, Fe and Co metal elements calculated from Ca _Fe A composition formula indicating: 1-xy, x, y, z, w, n, (1-x-y + w) / (1+) in Ca _1-xy La _x A _y Fe _2n-zw Co _z Ca _w Table 6 shows w), x / (1 + w), y / (1 + w), z / (1 + w), n / (1 + w), and y / (1-x + w).

注1：1100℃から1200℃（焼成温度）までの昇温速度
注2：1200℃（焼成温度）から1100℃までの降温速度Table 4

Note 1: Temperature increase rate from 1100 ° C to 1200 ° C (firing temperature) Note 2: Temperature decrease rate from 1200 ° C (firing temperature) to 1100 ° C

Table 5

Table 6

Table 6 (continued)

As is apparent from Tables 5 and 6, the ferrite sintered magnets of Sample Nos. 27 to 29 (this book) having a temperature rising rate of 1 ° C./min to 4 ° C./min and a temperature decreasing rate of 6 ° C./min or more invention example), in a case of containing the a element is also 0.11 or /uc,0.13 or Ca _Fe respectively / uc, and 0.11 units / uc, and the high B _r and high H _cJ and high H _k / H _cJ You can see that On the other hand, as a comparative example, sample No. 30 with a heating rate of 1 ° C./min but a cooling rate of 1 ° C./min, and sample No. 30 with a cooling rate of 6 ° C./min but a heating rate of 6.67 ° C./min In _.31 , it can be seen that Ca _Fe is as low as 0.04 / uc and 0.03 / uc, respectively, and that H _cJ and H _k / H _cJ are low.

Example 3
In the composition formula representing the atomic ratio of the metal element: Ca _1-xy La _x A _y Fe _2n-zw Co _z Ca _w , element A is Sr, (1-x-y + w) / (1 + w), x / (1 + w), y / (1 + w), y / (1-x + w), z / (1 + w) and n / (1 + w) are blended as shown in Table 7. Then, ferrite sintered magnets of Sample Nos. 32 to 36 were obtained in the same manner as in Example 1 except that the firing temperature was 1200 ° C. and the heating rate and the cooling rate shown in Table 7 were used. SrCO ₃ was used as the Sr raw material. B _r of resultant sintered ferrite magnet, the measurement result of H _cJ and H _k / H _cJ shown in Table 8. Further, the analysis result of Ca _Fe obtained by similarly as in example 1, Rietveld analysis, and Ca which is calculated from the Ca _Fe, La, Ba and / or Sr in which the A element, the atomic ratio of Fe and Co metal elements A composition formula indicating: 1-xy, x, y, z, w, n, (1-x-y + w) / (1+) in Ca _1-xy La _x A _y Fe _2n-zw Co _z Ca _w Table 9 shows w), x / (1 + w), y / (1 + w), z / (1 + w), n / (1 + w) and y / (1-x + w).

Table 7

注1：1100℃から1200℃（焼成温度）までの昇温速度
注2：1200℃（焼成温度）から1100℃までの降温速度Table 7 (continued)

Note 1: Temperature increase rate from 1100 ° C to 1200 ° C (firing temperature) Note 2: Temperature decrease rate from 1200 ° C (firing temperature) to 1100 ° C

Table 8

Table 9

Table 9 (continued)

As is clear from Table 8 and Table 9, the sample rate is 1 ° C / min to 4 ° C / min, the temperature decrease rate is 6 ° C / min or more, and y / (1-x + w) is less than 0.56. .32 ferrite sintered magnet of (invention example), it can be seen that Ca _Fe indicates 0.12 pieces / uc, and the high B _r and high H _cJ and high H _k / H _cJ. On the other hand, as a comparative example, sample No. 33 with a heating rate of 1 ° C./min but a cooling rate of 1 ° C./min, sample No. 33 with a cooling rate of 6 ° C./min but a heating rate of 6.67 ° C./min. 34, sample No. 35 where y / (1-x + w) = 0.672 even when the temperature rising rate is 1 ° C./min to 4 ° C./min and the temperature decreasing rate is 6 ° C./min or more, and y / (1- sample No.36 is a x + w) = 1.000, 0.03 or Ca _Fe each /uc,0.03 pieces /uc,0.02 pieces / uc and least 0.00 units / uc, low H _cJ and H _k / H _cJ I understand that.

Example 4
In the composition formula representing the atomic ratio of metal elements: Ca _1-xy La _x A _y Fe _2n-zw Co _z Cau _w , element A is Sr (SrCO ₃ ), and (1-x-y + w) / (1 + w), x / (1 + w), y / (1 + w), y / (1-x + w), z / (1 + w) and n / (1 + w) are shown in Table 10. The calcined body obtained by calcining the raw material powder blended as described above was pulverized in the same manner as in Example 1. The obtained finely pulverized slurry was dried at 150 ° C. for 8 hours, and the finely pulverized powder obtained through a mesh with an opening of 100 μm was subjected to the heating rate and the cooling rate shown in Table 10 except that the firing temperature was 1200 ° C. Firing was carried out in the same manner as in Example 1. The obtained fired body was pulverized in an agate mortar to obtain ferrite fired powders of Sample Nos. 37 to 39.

Table 10

注1：1100℃から1200℃（焼成温度）までの昇温速度
注2：1200℃（焼成温度）から1100℃までの降温速度Table 10 (continued)

Note 1: Temperature increase rate from 1100 ° C to 1200 ° C (firing temperature) Note 2: Temperature decrease rate from 1200 ° C (firing temperature) to 1100 ° C

Table 11 shows the measurement results of the saturation magnetization σ _s and _HA of the obtained sintered ferrite powder. Further, the analysis result of Ca _Fe obtained by similarly as in example 1, Rietveld analysis, and Ca which is calculated from the Ca _Fe, La, A element is Sr, composition formula showing the atomic ratio of metal elements of Fe and Co : 1-xy, x, y, z, w, n, (1-x-y + w) / (1 + w), x in Ca _1-xy La _x A _y Fe _2n-zw Co _z Ca _w Table 12 shows / (1 + w), y / (1 + w), z / (1 + w), n / (1 + w), and y / (1-x + w).

Table 11

Table 12

Table 12 (continued)

As is apparent from Tables 11 and 12, the sintered ferrite powder of Sample No. 37 (invention example) having a temperature rising rate of 1 ° C./min and a temperature decreasing rate of 6 ° C./min is 0.14 pieces of Ca _Fe / in. uc, indicating high σ _s and high _HA . On the other hand, sample No. 38, which has a temperature decrease rate of 6 ° C./min but a temperature increase rate of 6.67 ° C./min as a comparative example, y / In sample No. 39 where (1-x + w) = 1.0, Ca _Fe was as small as 0.03 / uc and 0.00 / uc, respectively, and σ _s and _HA were low.

The ferrite compound according to the present invention can exhibit high performance when used in sintered magnets, bonded magnets, magnetic recording media and the like. Especially when the main constituents of the ferrite sintered magnet, with improved H _cJ while maintaining high B _r and a high H _k / H _cJ, sintered ferrite magnets which can respond to thinning are obtained, which ferrite sintered The magnetized magnet can be suitably used for electric parts for automobiles such as various motors, generators, and speakers, parts for electric devices, and the like, and in particular, can contribute to reducing the size, weight and efficiency of these parts.

Claims (3)

A ferrite compound having a hexagonal M-type magnetoplumbite structure and containing Ca, La, Fe and Co as essential components,
A ferrite compound characterized in that the total amount of Ca present at 2a, 4e, 4f ₁ , 4f ₂ and 12k sites in the unit cell of the M-type magnetoplumbite structure is 0.05 or more per unit cell. 2. The ferrite compound according to claim 1, wherein the composition formula indicates the atomic ratio of the A element, which is Ca, La, Ba and / or Sr, the metal element of Fe and Co: Ca _1-xy La _x A _y Fe _2n-zw In Co _z Ca _w , 1-xy, x, y, z, w, and n indicating a molar ratio are
0.23 ≦ (1-x-y + w) / (1 + w) ≦ 0.75,
0.2 ≦ x / (1 + w) ≦ 0.65,
0 ≦ y / (1 + w) ≦ 0.4,
0.2 ≦ z / (1 + w) <0.65,
w ≧ 0.025
3 <n / (1 + w) <6 and
0 ≦ y / (1-x + w) <0.56
A ferrite compound characterized by satisfying The ferrite compound according to claim 1 or 2, wherein the ferrite compound pulverizes a calcined body obtained by calcining a raw material powder, and a temperature rising rate in a temperature range of 1100 ° C to a firing temperature is 1 to 4 ° C. And a ferrite compound produced by firing under conditions where the temperature lowering rate in the temperature range of 1 to 100 ° C. is 6 ° C./minute or more.

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