JPH11307331A - Ferrite magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive high performance ferrite magnet with superior magnetic characteristics, especially B/H curve squarability by adding La, Co, and M elements compositely. SOLUTION: This ferrite magnet has a basic composition, in which an atomic rate is (A1-x Rx )O.n[ Fe1-y (Co1-z Mz )y}2 O3 ] (A indicates Sr and/or Ba, and R indicates at least one or more kinds from among La, Ce, Pr, Nd, Sm, Eu, and Gd. while La is necessarily included, and M indicates Mn and/or V, 0<y<=0.04, and 0<z<=0.75, and 0<=x<=2.4 ny, and 5.4<=n<=6.0).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a new high-performance ferrite magnet which is extremely useful in a wide range of magnet application products and has a higher coercive force (iHc) and a higher saturation magnetization (σs) than conventional ones.

[0002]

2. Description of the Related Art Ferrite magnets are used for various applications including rotating machines such as motors and generators. Recently, particularly in the field of rotating machines for automobiles, ferrite magnets having higher magnetic characteristics have been demanded for the purpose of high efficiency with the aim of reducing the size and weight in the rotating machine field of electric equipment. Conventionally, high-performance Sr ferrite or Ba ferrite magnets have been manufactured as follows. That is, after mixing the iron oxide and the carbonate of Sr or Ba, the ferrite-forming reaction is terminated by calcination. The calcined clinker is coarsely pulverized. The coarsely pulverized calcined powder is converted into SiO ₂ , SrCO ₃ and CaCO ₃ for controlling the sintering behavior, and Al ₂ O ₃ or C for controlling the holding force iHc.
r ₂ O ₃ Average particle diameter value with powder additives such as is 0.7
Finely pulverize to 1.0 μm. The finely pulverized slurry is wet-formed while being oriented in a magnetic field to obtain a formed body.
The molded body is fired and then processed into a product shape to obtain a product.
On the premise of such a manufacturing method, the methods for improving the performance of ferrite magnets are considered to be roughly classified into the following five methods. The first method is atomization. The coercive force iHc increases as the size of the crystal grains in the fired body approaches the critical single domain particle size of about 0.9 μm of the Sr ferrite magnet having the magnetoplumbite type (M type) crystal structure. In view of the grain growth, the finely pulverized particles may be atomized to an average particle size of, for example, 0.7 μm or less. However, this method has a problem that the finer the particles, the worse the dewatering characteristics during wet molding and the lower the production efficiency. The second method is to make the size of the crystal grains of the fired body as uniform as possible. Ideally, the size of the crystal grains is made as uniform as possible, and the value is set to the critical single domain particle diameter value (about 0.9 μm).
And it is sufficient. This is because a crystal grain larger or smaller than this value leads to a decrease in the coercive force iHc. The specific means of improving the performance by this method is to improve the particle size distribution of the finely pulverized powder, but if industrial production is assumed, existing pulverizers such as ball mills and attritors must be used. Inevitably, the degree of improvement is naturally limited.
In recent years, an attempt to produce ferrite fine particles having a uniform particle diameter by a chemical precipitation method has been disclosed, but this method cannot be said to be suitable for industrial mass production. A third method is to improve the degree of crystal orientation that affects magnetic anisotropy. Specific means in this method include adding a surfactant to the finely pulverized slurry to improve the dispersibility of the ferrite particles in the slurry, or to increase the magnetic field strength during orientation. A fourth method is to increase the density of the fired body. The theoretical density of the sintered Sr ferrite is 5.15 g / cc. Sr currently on the market
The density of ferrite magnets is generally in the range of 4.9 to 5.0 g / cc, which corresponds to a theoretical density ratio of 95 to 97%. If the density is increased, the residual magnetic flux density Br is expected to be improved. However, in order to further increase the density beyond the above-mentioned density range, special high-density means such as HIP is required.
However, the introduction of such a special process leads to an increase in manufacturing cost, and may lose the characteristics of the ferrite magnet as a low-cost magnet. A fifth method is to improve the crystal magnetic anisotropy constant Ku or the saturation magnetization s of the ferrite compound itself, which is the main composition constituting the ferrite magnet. Improvement of the crystal magnetic anisotropy constant Ku has a possibility of leading to improvement of the coercive force Hc. Further, the improvement of the saturation magnetization s has a possibility of directly leading to the improvement of the residual magnetic flux density Br. The present inventors have conducted intensive studies to realize the above-described high performance, and as a result,
A new ferrite magnet having remarkably excellent magnetic properties and a basic manufacturing method thereof have been found by the above method. That is, A
By adding a compound of a different metal element (usually a metal oxide) to a composition which can be represented by OnnFe ₂ O ₃ (where A is Sr and / or Ba),
And a method for replacing a part of the Fe element with another element. As the different elements, La and Co
It has been found that the combined addition of M and M elements or Co and M elements is particularly effective. Here, Co and M elements directly play a role in improving the magnetic characteristics, and the La element has an effect of charge compensation.

[0003]

SUMMARY OF THE INVENTION The present inventors have as additives La and Co oxides, namely La ₂ O ₃ and Co _3.
In the course of further study using O ₄ , La ₂ O ₃
It has been found that the solid-state reaction between SrCO ₃ and a mixture of SrCO ₃ + Fe ₂ O ₃ or the solid-state reaction between La and a ferrite composition is insufficient. In other words, the diffusion rate of La in the ferrite composition is low, and as a result, a microstructure having an uneven distribution of La in the sintered body is obtained.
It was found that the substitution effect of a and Co was not sufficiently obtained. If, for example, the content of La in the individual sintered body crystal grains is different, a distribution occurs in the coercive force, and as a result, the squareness of the magnetic hysteresis curve becomes poor, and the magnetic properties can be taken out from the obtained ferrite magnet. This is because the maximum energy product value, which is a measure of energy, decreases. The above La ₂ O ₃ and Co ₃ O ₄
Raw material prices are based on the other major raw materials SrCO ₃ and F
It is much higher than that of e ₂ O ₃ , and has been a major hindrance to the practical use of La and Co-added ferrite magnets. Therefore, an object of the present invention is to provide an inexpensive high-performance ferrite magnet which is excellent in magnetic properties, in particular, squareness of a BH curve, by adding La, Co, and M elements in combination. The object of the present invention is to provide Co,
By adding M element in combination, magnetic properties, especially B
An object of the present invention is to provide an inexpensive high-performance ferrite magnet having excellent H curve squareness.

[0004]

Means for Solving the Problems In order to achieve the above object, the present invention provides an atomic ratio of (A _{1 -x} R _x ) On · {Fe _{1 -y} Co _y ｝ ₂ O ₃ ] (A Is Sr and / or Ba, R is La, Ce, P
at least one of r, Nd, Sm, Eu, and Gd and always includes La) by adding the element Mn and / or V to the composition to obtain Fe or Co of the composition. If you replace parts of your site,
It is possible to reduce the amounts of La and Co added without substantially impairing the essential effects of La and Co addition, which is effective not only in reducing the production cost but also in particular in the magnetic properties. The present invention has been found to have a remarkable effect on improving the squareness of a curve, and has made the present invention.

That is, according to the present invention, (A _{1 -x} R _x ) On · n [｛Fe _{1 -y} (Co _{1 -zM z} ) _y } ₂ O ₃ ] (A is Sr and / or Ba , R is La, Ce, P
at least one of r, Nd, Sm, Eu, and Gd and always includes La, M is Mn and / or V), 0 <y ≦ 0.04, 0 <z ≦ 0.75, 0 ≦ x ≦
The ferrite magnet has a basic composition of 2.4ny, 5.4 ≦ n ≦ 6.0.

R is La and Ce, Pr, Nd, Sm,
The present invention can be configured using at least one of Eu and Gd. Each of these ions has the same valence and similar ionic radius as the Sr ²⁺ ion, and satisfies the conditions for elemental substitution in the oxide. It is also possible to use these composite oxides (for example, mixed rare earth oxides such as misch metal). When a higher iHc and σs are required, the proportion of La in R is preferably at least 50 at%, more preferably at least 70 at%, and R excluding unavoidable impurities has a ratio of La to La. It is ideal to become.

[0007] Co is an essential element as an element to replace the Fe site. Co ions have a magnetic moment due to orbital angular momentum, and it is presumed that the interaction of the orbital angular momentum with the crystal lattice is deeply related to the increase in crystal magnetic anisotropy. This is the source of high ferrite magnets with high magnetic properties. The substitution rate y of Co ions to Fe ions must be 4% or less in atomic ratio. If it exceeds 4%, the magnetic properties deteriorate. When a higher coercive force is required, the substitution rate y may be increased within the above range.

[0008] M is an important element constituting the present invention,
Mn and / or V. Their content relative to Co is at most 75% in atomic ratio. If it exceeds 75%, the original effect of Co on the magnetic properties is impaired. 75%
In the following range, the residual magnetic flux density Br and the coercive force i
Not only can the amount of high-priced Co addition be reduced without significantly lowering Hc, but also the squareness of the demagnetization curve, which is important as practical magnetic characteristics, can be improved. As mentioned above,
The magnet of the present invention is described using a chemical formula in a display format in which a Co site is replaced with Mn and / or V. However, this is merely to clarify the addition ratio of Co to Mn and / or V. This is a convenient description.
This means that the site has been replaced with Co or Mn (V). Another effect of the addition of the M element is that the amount of La added can be reduced. Assuming that the Co ion valence in the ferrite composition is divalent, and when the M element is not added, the relational expression of x = 2ny must be strictly satisfied from the condition of charge compensation. This is because the valences of Sr, La and Fe ions in the ferrite composition are +2, +3 and +3, respectively. However, it is necessary to substantially satisfy the condition of 1.6 ny ≦ x ≦ 2.4 ny in consideration of the presence of unreacted substances and the like, due to the specificity of the ferrite magnet manufactured by the powder metallurgy technique. When the ratio of La and Co is out of the above range, unreacted La or Co or a compound different from magnetoplumbite ferrite is present at the grain boundaries of ferrite crystal grains, deteriorating magnetic properties. This can cause That is, the amount of La added is defined by the amount of Co added and has a lower limit. On the other hand, the feature of Mn and V selected as the M element is that they can have a plurality of valences of two or more. Assuming that the M element ion has a valence of three or more in the ferrite composition, the lower limit of the above-mentioned charge compensation conditions can be reduced in principle, that is, the amount of La added can be reduced. Although the valence of the M element ion in the ferrite composition is not clear, as a result of intensive experimental studies in accordance with the above-described principle, it was found that the addition of the M element resulted in a La content of 0%. It was found that good magnetic properties were obtained in a wide composition range on the weight reduction side, and it was found that the amount of La added could be reduced. That is, the La content may be 0 to 2.4 ny in the substitution rate (x) at the Sr site.

In order to obtain good magnetic properties, the value of n must be 5.4 or more and 6.0 or less. If the n value exceeds 6.0, a different phase (for example, α-Fe ₂ O ₃ ) other than the magnetoplumbite phase is generated, and the magnetic properties are degraded. If the n value is less than 5.4, sufficiently good residual magnetic flux density cannot be obtained.

[0010] The above basic composition is mixed → calcined → pulverized →
It can be formed substantially at the calcining stage of the standard ferrite magnet manufacturing process of molding → sintering. That is, R
And Co and M elements or Co and M elements are added at the mixing stage of the above process, which leads to two high-temperature heating processes of calcination and sintering, and solid diffusion progresses to obtain a more uniform composition. Is obtained. However, at the grinding stage of the standard manufacturing process,
The effect of the present invention can also be substantially improved by adding the compound (for example, oxide) of R and Co and the M element or the compound of the Co and M element (for example, oxide) substantially to make the above ferrite magnet of the present invention a basic composition. There is no loss. In order to obtain a high-performance ferrite sintered body, Si as an additive for suppressing coarsening of crystal grains during sintering is used in the basic composition.
The O ₂ in a weight ratio from 0.2 to 0.5% and / or CaO
Is preferably added at the pulverization stage so as to contain 0.30 to 0.85% by weight.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to embodiments. (Example 1) SrCO ₃ , La ₂ O ₃ , Fe ₂ O ₃ , Co ₃ O
₄ and MnCO ₃ by converting (Sr _1-x La _x ) On · {[Fe _1-y
In _{(Co 1-z Mn z)} y} 2 O 3] becomes formula, n = 5.
85, x = 2ny, y = 0.15, z = 0 to 1 and mixed by wet method, and then at 1250 ° C. for 2 hours,
It was calcined in the atmosphere. The calcined powder was dry-pulverized with a roller mill to obtain a coarse pulverized powder. Thereafter, wet pulverization was performed with an attritor to obtain a slurry containing finely pulverized powder having an average particle size of 0.7 μm. As sintering aids, SiO ₂ and Ca
CO ₃ was 0.4% and 0.4% by weight with respect to the pulverized powder, respectively.
8% Added at the beginning of milling. This slurry was subjected to wet forming in a magnetic field of 10 kOe to obtain a formed body. This molded body was sintered at a temperature range of 1180 to 1230 ° C. for 2 hours to obtain a sintered body. This sintered body was processed into a shape of about 10 × 10 × 20 mm, and the magnetic characteristics were measured with a BH tracer. In ferrite magnets, it is common to evaluate magnetic properties by a combination of residual magnetic flux density Br and coercive force iHc. However, since the Br and iHc values change in conjunction with the sintering temperature, the illustration becomes complicated when, for example, a change in magnetic properties due to the addition amount of a certain element is observed. Therefore, the Br value when iHc is a standard value is Br
^* Was used as an index of magnetic characteristics. This Br ^* value is
The Br and iHc values were plotted on a Br-iHc diagram with the sintering temperature changed by five standard points, and then determined by extrapolating to / from a predetermined iHc value. In the examples according to the present invention, the standard iHc value was 4000 Oe. In the second quadrant of the demagnetization curve, the magnetic field intensity value when the B value becomes 95% of Br is Hk, and the ratio H to iHc is H
The squareness of the demagnetization curve was evaluated at k / iHc. Hk /
Since the iHc value also has a sintering temperature dependence, similarly to the case of Br ^* , the value obtained by extrapolating iHc to 4000 Oe (Hk
/ IHc) ^* was used as an index of squareness. The results are shown in FIG. FIG. 1 shows that the addition of Mn for the purpose of replacing Co improves the squareness of the demagnetization curve without remarkably reducing Br ^* , and the effect of Mn addition is clear. However, when the substitution amount z of Mn to Co exceeds 0.75, the reduction of Br ^* becomes remarkable. Therefore, an appropriate range of z is more than 0 and 0.75 or less. More preferably, it is 0.1 or more and 0.7 or less.

(Example 2) A sintered body was prepared and evaluated in the same manner as in Example 1 except that the value of n was in the range of 5.0 to 6.5. Has a tendency to decrease Br, and if it exceeds 6.0, α-Fe ₂ O
₃ and a marked decrease in Br and iHc. That is, the preferable range of the n value was found to be 5.4 or more and 6.0 or less.

(Example 3) Further, a sintered body was prepared and evaluated in the same manner as in Example 1 except that V was employed as the M element. As a result, it was confirmed that V had the same effect as Mn. did.

Example 4 SrCO ₃ , La ₂ O ₃ , Fe ₂
O ₃ , Co ₃ O ₄ and MnCO ₃ are converted to (Sr _1-x La _x ) O.
In _{n [{Fe 1-y (} Co 1-z Mn z) y} 2 O 3] becomes Formula, n = 5.85, x = 2ny , y = 0~0.05, z
= 0.5 and mixed by wet method.
Calcination was performed in the air at 50 ° C. for 2 hours. The calcined powder was dry-pulverized with a roller mill to obtain a coarse pulverized powder. Thereafter, wet pulverization is performed with an attritor, and the average particle size is 0.7 μm.
A slurry containing finely pulverized powder was obtained. Further, as sintering aids, SiO ₂ and CaCO ₃ were added at a weight ratio of 0.4% and 0.8% with respect to the pulverized powder at the initial stage of pulverization. This slurry was subjected to wet forming in a magnetic field of 10 kOe to obtain a formed body. The molded body was heated at a temperature of 1180 to 1230 ° C. for 2 hours.
After sintering for a time, a sintered body was obtained. About 10 × 10
It was processed into a shape of x20 mm, and its magnetic properties were measured with a BH tracer. As in Example 1, Br and iH
The evaluation was performed using the Br ^* value as an index of c and (Hk / iHc) ^* as an index representing the squareness of the demagnetization curve.
The results are shown in FIG. From FIG. 2, when the ratio of Co and Mn is fixed to 1 and the y value, that is, the (Co + Mn) substitution amount of the Fe site is increased while maintaining the condition of x = 2ny,
A remarkable improvement in Br ^* was observed while maintaining the squareness ratio of the demagnetization curve. However, when the y value exceeds 0.04, the magnetic characteristics are significantly reduced. Therefore, the preferred range of y in the present invention is more than 0 and not more than 0.04, more preferably not less than 0.005 and not more than 0.03.

Example 5 SrCO ₃ , La ₂ O ₃ , Fe ₂
O ₃ , Co ₃ O ₄ and MnCO ₃ are converted to (Sr _1-x La _x ) O.
In _{n [{Fe 1-y (} Co 1-z Mn z) y} 2 O 3] becomes Formula, n = 5.85, x = 0~2.8ny , y = 0.01
3. Compounded so that z = 0.5, mixed by wet method, and calcined at 1250 ° C. for 2 hours in the air. The calcined powder was dry-pulverized with a roller mill to obtain a coarse pulverized powder. Thereafter, wet pulverization was performed with an attritor to obtain a slurry containing finely pulverized powder having an average particle size of 0.7 μm. Further, as sintering aids, SiO ₂ and CaCO ₃ were added at a weight ratio of 0.4% and 0.8% with respect to the pulverized powder at the initial stage of pulverization. This slurry was subjected to wet forming in a magnetic field of 10 kOe to obtain a formed body. This molded body was sintered at a temperature range of 1180 to 1230 ° C. for 2 hours to obtain a sintered body. About 1
It was processed into a shape of 0x10x20 mm, and its magnetic properties were measured with a BH tracer. As in Example 1, the evaluation was performed using the Br ^* value as an index of Br and iHc, and (Hk / iHc) ^* as an index representing the squareness of the demagnetization curve. The results are shown in FIG. From FIG. 3, when the ratio of Co and Mn is fixed to 1 and the x value, that is, the La substitution amount of the Sr site is changed under the condition of y = 0.13, the charge compensation condition X when Mn is not added is X = It can be seen that relatively good magnetic characteristics can be obtained even in a composition region where the x value is smaller than 2 ny. However, under the condition that x was excessively increased as compared with the above condition, a decrease in magnetic properties was observed. Therefore,
An appropriate range of x is 0 or more and 2.4 ny or less, and more preferably 0.05 or more and 2.2 ny or less. As shown in this example, by adding Mn, good magnetic properties can be obtained even in a composition region with a small amount of La added, as compared with the amount of La added defined by the charge compensation conditions when Mn is not added. It was confirmed that it could be obtained.

[0016]

As described above, the ferrite magnet of the present invention has a substantially improved saturation magnetization and / or coercive force as compared with the conventional ferrite magnet even though it is a ferrite magnet substantially having a magnetoplumbite type crystal structure. As a new ferrite magnet with excellent cost performance, it can greatly contribute to the development of a wide range of magnet application products.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a correlation between z and magnetic characteristics in the present invention.

FIG. 2 is a diagram showing an example of a correlation between y and magnetic characteristics in the present invention.

FIG. 3 is a diagram showing an example of a correlation between x and magnetic characteristics in the present invention.

Claims (1)

[Claims] 1. An atomic ratio of (A _{1 -x} R _x ) On · [Fe _{1 -y}
(Co _1-z M _z ) _y } ₂ O ₃ ] (A is Sr and / or Ba, R is La, Ce, P
at least one of r, Nd, Sm, Eu, and Gd and always includes La, M is Mn and / or V), 0 <y ≦ 0.04, 0 <z ≦ 0.75, 0 ≦ x ≦
A ferrite magnet having a basic composition of 2.4ny, 5.4 ≦ n ≦ 6.0.