阅读说明：本技术 烧结铁氧体磁体 (Sintered ferrite magnet ) 是由 山本将贵 小林义德 于 2018-05-17 设计创作，主要内容包括：一种烧结铁氧体磁体,所述烧结铁氧体磁体由表示金属元素Ca、La、Fe、Co和Zn的原子比的通式Ca<Sub>1-x</Sub>La<Sub>x</Sub>Fe<Sub>2n-y-z</Sub>Co<Sub>y</Sub>Zn<Sub>z</Sub>表示,其中x、y、z和n[2n是由2n＝(Fe+Co+Zn)/(Ca+La)表示的摩尔比]满足0.4<x<0.75,0.15≤y<0.4,0.11≤z<0.4,0.26≤(y+z)<0.65,并且3≤n≤6。(A sintered ferrite magnet composed of a general formula Ca representing the atomic ratio of metal elements Ca, La, Fe, Co and Zn 1‑x La x Fe 2n‑y‑z Co y Zn z Wherein x, y, z and n [2n are molar ratios expressed by 2n ═ Fe + Co + Zn)/(Ca + La)]Satisfies 0.4<x<0.75，0.15≤y<0.4，0.11≤z<0.4，0.26≤(y+z)<0.65 and n is more than or equal to 3 and less than or equal to 6.)

1. A sintered ferrite magnet composed of a general formula Ca representing the atomic ratio of metal elements Ca, La, Fe, Co and Zn_1-xLa_xFe_2n-y-zCo_yZn_zWherein x, y, z and n [2n are molar ratios expressed by 2n ═ Fe + Co + Zn)/(Ca + La)]Satisfy the requirement of

0.4<x<0.75，

0.15≤y<0.4，

0.11≤z<0.4，

0.26 ≦ (y + z) <0.65, and

3≤n≤6。

2. the sintered ferrite magnet of claim 1, wherein said x and y satisfy 0.15 ≦ y ≦ 0.35, and 0.15 ≦ z ≦ 0.35.

3. The sintered ferrite magnet of claim 1 or 2, wherein x satisfies 0.475 ≦ x ≦ 0.7.

4. The sintered ferrite magnet of any one of claims 1 to 3, wherein the y and z satisfy 0.26 ≦ (y + z ≦ 0.6.

5. The sintered ferrite magnet as claimed in any one of claims 1 to 4, wherein SiO is contained at 1.8 mass% or less₂。

6. The sintered ferrite magnet as claimed in any one of claims 1 to 5, wherein in the above general formula, a part of La is substituted by at least one rare earth element other than La.

7. The sintered ferrite magnet as claimed in claim 6, wherein in the above general formula, 50 mol% or less of La is replaced by at least one rare earth element other than La.

Technical Field

The present invention relates to a sintered ferrite magnet.

Background

Sintered ferrite magnets are extremely chemically stable and are excellent in cost performance because their main starting material is inexpensive iron oxide, although their maximum energy product is only 1/10 that is the maximum energy product of sintered rare earth magnets (e.g., sintered NdFeB magnets). Therefore, their global production is still the largest among magnet materials.

In various applications such as motors, speakers, and the like, in which sintered ferrite magnets are used, high-performance materials are strongly required for motors for automobiles, household appliances, and the like. As rare earth materials have recently become more expensive and have more procurement risks, studies have been made on the use of sintered ferrite magnets in industrial motors, motors for driving electric vehicles (EV, HV, PHV, etc.), generators, and the like, in which only sintered rare earth magnets have been used so far.

A typical sintered ferrite magnet is Sr ferrite having a magnetoplumbite structure, the basic composition of which consists of SrFe₁₂O₁₉And (4) showing. By adding SrFe₁₂O₁₉La for middle use³⁺Substitute a part of Sr²⁺And with Co²⁺Replacing a part of Fe³⁺When the obtained sintered Sr-La-Co ferrite magnet was put into practical use in the late 1990 s, the magnetic properties of the ferrite magnet were significantly improved. In 2007, sintered Ca — La — Co ferrite magnets with further improved magnetic properties were put into practical use. However, in order to be used in the above applications, the sintered Ca — La — Co ferrite magnet is required to have high performance, and in specific applications (for example, motors for household appliances), the residual magnetic flux density (hereinafter referred to as "B") needs to be increased_r") to increase the power of the motor.

It is known that B is increased by substituting Zn for a part of Co in a sintered Sr-La-Co ferrite magnet_r(JP 11-154604A, etc.).

However, in the sintered Sr-La-Co ferrite magnetThe substitution of a part of Co with Zn is not practically carried out because it hardly increases B_rWhile remarkably lowering the coercive force (hereinafter referred to as "H_cJ”)。

Object of the Invention

It is therefore an object of the present invention to provide a composition having a high B_rAnd almost no H_cJReduced sintered ferrite magnets.

Summary of The Invention

The inventors have found that the general formula Ca representing the atomic ratio of the metal elements Ca, La, Fe, Co and Zn in Japanese patent application No. 2017-102245_1-xLa_xFe_2n-y-zCo_yZn_zWherein x, y, z and n [2n ] satisfy the following molar ratio of (Fe + Co + Zn)/(Ca + La) ═ 2n]Is required to provide a composition having a high B_rAnd almost no H_cJReduced sintered ferrite magnet:

0.4≤x≤0.6，

0<y≤0.35，

0<z≤0.35，

0.2 ≦ (y + z) 0.4, and

3≤n≤6。

as a result of further studies, the inventors have found that a new composition range partially overlapping with the composition range of japanese patent application No. 2017-102245 provides magnetic properties equivalent to or higher than those obtained by the composition range of japanese patent application No. 2017-102245, thereby proposing the present invention. In addition, the sintered ferrite magnet described below is an illustrative example of the present invention, and the present invention is not limited to the composition represented by the above general formula.

Accordingly, the sintered ferrite magnet of the present invention is composed of the general formula Ca representing the atomic ratio of the metal elements Ca, La, Fe, Co and Zn_1-xLa_xFe_2n-y-zCo_yZn_zWherein x, y, z and n [2n are molar ratios expressed by 2n ═ Fe + Co + Zn)/(Ca + La)]Satisfy the requirement of

0.4<x<0.75，

0.15≤y<0.4，

0.11≤z<0.4，

0.26 ≦ (y + z) <0.65, and

3≤n≤6。

the above x and y preferably satisfy 0.15. ltoreq. y.ltoreq.0.35, and 0.15. ltoreq. z.ltoreq.0.35.

The above x preferably satisfies 0.475. ltoreq. x.ltoreq.0.7.

The above y and z preferably satisfy 0.26. ltoreq. y + z.ltoreq.0.6.

The sintered ferrite magnet of the present invention preferably contains 1.8 mass% or less of SiO₂。

In the above formula, a part of La may be substituted with at least one rare earth element other than La.

In the above formula, 50 mol% or less of La may be substituted with at least one rare earth element other than La.

Effects of the invention

The present invention can provide a composition having a high B_rAnd almost no H_cJReduced sintered ferrite magnets.

Brief Description of Drawings

FIG. 1 is a view showing H in a sintered ferrite magnet of reference example 1_cJAnd B_rA graph of the relationship between.

FIG. 2 is a graph showing H in the sintered ferrite magnet of reference example 2_cJAnd B_rA graph of the relationship between.

FIG. 3 is a graph showing H in the sintered ferrite magnet of reference example 3_cJAnd B_rA graph of the relationship between.

FIG. 4 is a graph showing H in the sintered ferrite magnet of reference example 4_cJAnd B_rA graph of the relationship between.

FIG. 5 is a graph showing H in the sintered ferrite magnet of reference example 5_cJAnd B_rA graph of the relationship between.

Description of the preferred embodiments

In the sintered ferrite magnet of the present invention, the atomic ratio x (La content) is 0.4<x<0.75. X less than 0.4 or greater than 0.75 does not provide high B_r. The atomic ratio x is more preferably 0.475. ltoreq. x.ltoreq.0.7. A portion of La may be replaced with at least one rare earth element other than La. Is replaced byThe amount of La generated is preferably 50 mol% or less of the original amount of La.

Y (Co content) is 0.15. ltoreq. y<0.4. Y less than 0.15 tends to provide a lower H_cJWhile y above 0.4 tends to provide lower B_r. The atomic ratio y is more preferably 0.15. ltoreq. y.ltoreq.0.35.

Z (Zn content) is 0.11-z<0.4. Z less than 0.11 tends to provide lower B_rWhile z above 0.4 tends to provide a lower H_cJ. The atomic ratio z is more preferably 0.15. ltoreq. z.ltoreq.0.35.

The atomic ratios y and z satisfy the relationship of 0.26 ≦ (y + z) < 0.65. When (y + z) is less than 0.26 or 0.65 or more, excellent magnetic properties cannot be obtained. More preferably, (y + z) is 0.26. ltoreq. y + z. ltoreq.0.6.

In the above formula, the molar ratio 2n is represented by 2n ═ Fe + Co + Zn)/(Ca + La), where n is 3. ltoreq. n.ltoreq.6. N less than 3 or greater than 6 does not provide high B_r。

In the production process of the sintered ferrite magnet of the present invention, as described later, 1.8 mass% or less of SiO may be added₂As a sintering aid. SiO added as sintering aid₂Becomes a liquid phase component during sintering, and remains as a component in the grain boundary of the sintered ferrite magnet. Thus, when SiO is added₂When used as a sintering aid, the sintered ferrite magnet of the present invention contains 1.8 mass% or less of SiO₂。SiO₂The content being SiO₂Mass of (C) relative to CaCO₃、La(OH)₃、Fe₂O₃、Co₃O₄ZnO and SiO₂By converting the respective amounts (% by mass) of Ca, La, Fe, Co, Zn and Si in compositional analysis of a sintered ferrite magnet, for example, by means of an ICP optical emission spectrometer, into CaCO₃、La(OH)₃、Fe₂O₃、Co₃O₄ZnO and SiO₂Are calculated from the respective mass.

Although the above formula is represented by the atomic ratio of the metal element, the composition containing oxygen (O) is represented by the formula Ca_{1- x}La_xFe_2n-y-zCo_yZn_zO_αAnd (4) showing. The number of moles α of oxygen is basically α ═ 19, although it varies according to the valence of Fe and Co and the values of x, y, z and n. Further, when sintering in a reducing atmosphere, the ratio of oxygen to the metal element may vary depending on the vacancy of oxygen, the variation in the valence of Fe in the ferrite phase, the variation in the valence of Co, and the like. Therefore, the actual number of moles α of oxygen may deviate from 19. Therefore, the atomic ratio of the metal elements is used in the present invention as the simplest way of expressing the composition.

The main phase constituting the sintered ferrite magnet of the present invention is a composite phase (ferrite phase) having a hexagonal magnetoplumbite (M-type) structure. In general, a magnetic material, particularly a sintered magnet, is composed of a plurality of compounds, and the compound that determines the characteristics (material properties, magnetic properties, etc.) of the magnetic material is defined as a "main phase".

"having a hexamagnetoplumbite (M-type) structure" means that when X-ray diffraction of a sintered ferrite magnet is measured under ordinary conditions, the hexamagnetoplumbite (M-type) structure is observed as a main structure in an X-ray diffraction pattern.

The sintered ferrite magnet of the present invention can be produced by a method for known sintered Sr-La-Co ferrite magnets and Ca-La-Co ferrite magnets. Examples of the production method will be explained below.

Compounds of metals used for the starting material powder such as oxides, carbonates, hydroxides, nitrates, chlorides, etc. can be used regardless of their valences. Solutions containing starting material powders may also be used. The compounds of Ca include carbonates, oxides, chlorides, etc. of Ca. The compound of La includes oxides such as La₂O₃Etc., hydroxides such as La (OH)₃Etc., carbonates such as La₂(CO₃)₃·8H₂O, and the like. The compound of Fe includes iron oxide, iron hydroxide, iron chloride, mill scale (mill scale), and the like. The compound of Co includes oxides such as CoO, Co₃O₄Etc., hydroxides such as CoOOH, Co (OH)₂Etc., carbonates such as CoCO₃Etc., and basic carbonates such as m₂CoCO₃·m₃Co(OH)₂·m₄H₂O(m₂、m₃And m₄Is a positive number), etc. The compound of Zn includes ZnO.

In order to accelerate the reaction during calcination, up to about 1 mass% of a compound containing B (boron), such as B, may be added, if desired₂O₃、H₃BO₃And the like. In particular, H₃BO₃The addition of (2) effectively improves the magnetic property. H added₃BO₃The amount of (b) is preferably 0.3% by mass or less, most preferably about 0.1% by mass. Because of H₃BO₃Has the effect of controlling the shape and size of the grains during sintering, and may be added after calcination (before fine pulverization or sintering), or both before and after calcination.

The prepared starting material powders are formulated and mixed to provide a starting material powder mixture. The formulation and mixing of the starting material powders can be carried out in the wet or dry state. The mixing of the starting material powders is made more uniform by stirring with a medium such as steel balls or the like. In the case of wet mixing, water is preferably used as the dispersion medium. In order to improve the dispersion of the starting material powder, known dispersants such as ammonium polycarboxylates, calcium gluconates, and the like can be used. The slurry of mixed starting materials may be calcined without further treatment or after dewatering.

The starting material powder mixture obtained by dry or wet mixing is heated in an electric furnace, a gas furnace or the like to form a ferrite compound having a hexamagnetoplumbite (M-type) structure by a solid-phase reaction. This process is referred to as "calcination", and the resulting compound is referred to as "calcined body".

The calcination step is preferably performed in an atmosphere having an oxygen concentration of 5 vol% or more. An oxygen concentration of less than 5 vol% results in abnormal grain growth, formation of undesirable phases, and the like. The oxygen concentration is more preferably 20 vol% or more.

As the temperature increases in the calcination step, a solid phase reaction to form a ferrite phase proceeds. When the calcination temperature is less than 1100 deg.c, unreacted hematite (iron oxide) remains, resulting in low magnetic properties. On the other hand, when the calcination temperature exceeds 1450 ℃, crystal grains excessively grow, requiring an excessively long time in the pulverization step. Therefore, the calcination temperature is preferably 1100 to 1450 ℃. The calcination time is preferably 0.5 to 5 hours. The calcined body is preferably coarsely pulverized by a hammer mill or the like.

The calcined body is then pulverized (finely pulverized) by a vibration mill, a jet mill, a ball mill, an attritor, or the like to form a powder (finely pulverized powder). The average particle size of the powder is preferably about 0.4 to 0.8. mu.m. The average particle size of the powder is measured herein by an air permeation method using an apparatus for measuring the specific surface area of the powder (for example, SS-100 available from Shimadzu Corporation) or the like. The pulverization step may be either or both of dry pulverization and wet pulverization. Wet pulverization is carried out using water and/or a nonaqueous solvent (an organic solvent such as acetone, ethanol, xylene, etc.) as a dispersion medium. Generally, a slurry containing water (dispersion medium) and a calcined body is formed. The slurry may contain a known dispersant and/or surfactant in an amount of 0.2 to 2 mass% on a solid content basis. After wet grinding, the slurry may be concentrated.

In the forming step after the pulverization step, the slurry is pressed in a magnetic field or without a magnetic field while removing the dispersion medium. Pressing in a magnetic field can align the crystallographic orientations of the powder particles, significantly improving magnetic properties. To further improve the orientation, a dispersant and a lubricant each in an amount of 0.1 to 1 mass% may be added to the slurry before the molding. Further, prior to shaping, the slurry may be concentrated, if desired. Concentration is preferably performed by centrifugal separation, pressure filtration or the like.

After the calcination step and before the molding step, a calcination auxiliary is added to the calcined body or powder (coarsely or finely pulverized powder). The sintering aid is preferably SiO₂And CaCO₃. As is clear from its composition, the sintered ferrite magnet of the present invention belongs to a sintered Ca-La-Co ferrite magnet. Since the sintered Ca-La-Co ferrite magnet contains Ca as a main phase component, unlike the conventional sintered Sr-La-Co ferrite magnet and the like, it is possible to eliminate the addition of a sintering aid such as SiO₂And CaCO₃Etc., to form a liquid phase and sinter it. That is, it is possible to eliminate the addition of SiO which is mainly used for forming a grain boundary phase in a sintered ferrite magnet₂Or CaCO₃The sintered ferrite magnet of the present invention was prepared. However, to suppress H_cJTo reduce, SiO may be added in the following amount₂And CaCO₃。

SiO added to 100% by mass of the calcined body or powder₂The amount of (B) is preferably 1.8% by mass or less. CaCO added to 100 mass% of the calcined body or powder₃The amount of (b) is preferably 2 mass% or less in terms of CaO. The sintering aid may be added at any time before, during or after the comminuting step. For example, (a) after the sintering aid is added to the calcined body, a pulverization step is performed, (b) the sintering aid is added during the pulverization step, or (c) after the sintering aid is added to the pulverized powder (finely pulverized powder) and mixed, a molding step is performed. As sintering aids, in addition to SiO₂And CaCO₃In addition, Cr may be added₂O₃、Al₂O₃And the like. The amount of each of them may be 1 mass% or less.

CaCO added₃The amount of (c) is herein represented by the value in CaO. Can pass through according to the amount of CaO (CaCO)₃The molecular weight of CaCO added is determined by the formula of (A) molecular weight of CaCO (x) in terms of the amount of CaO)/the molecular weight of CaO₃The amount of (c). For example, when 0.5 mass% of CaCO based on CaO is added₃Then, [100.09 (CaCO)₃Molecular weight of (B) × 0.5 mass% (amount in terms of CaO)](molecular weight of CaO): 0.892 mass% (CaCO added)₃Amount of). In addition, CaCO₃The molecular weight of (a) is 40.08 (atomic weight of Ca) +12.01 (atomic weight of C) +48.00 (atomic weight of O × 3) is 100.09, and the molecular weight of CaO is 40.08 (atomic weight of Ca) +16.00 (atomic weight of O) is 56.08.

After degreasing (if necessary), the green body obtained by pressing is sintered. The sintering is carried out in an electric furnace, a gas furnace, or the like. The sintering is performed in an atmosphere having an oxygen concentration of preferably 10% by volume or more, more preferably 20% by volume or more, and most preferably 100% by volume. The sintering temperature is preferably 1150 ℃ to 1250 ℃. The sintering time is preferably 0 hours (no holding time at the sintering temperature) to 2 hours.

After the sintering step, the final sintered ferrite magnet is obtained by known preparation steps such as a processing step, a washing step, an inspection step, and the like.