JP2001057305A - Hexagonal ferrite magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a hexagonal ferrite magnet having a high residual magnetic flux density and a high coersive force by a method wherein the saturation magnetization of an M type ferrite and the magnetic anisotropy of the ferrite are enhanced at the same time. SOLUTION: At least one kind of the element selected from among Sr, Ba and Ca is denoted to be A, one kind of the element of any of the elements of La, Pr, Nd and Ce or more than two kinds of the elements is or are denoted to be R, and one kind of the element of any of the elements of Co, Ni and Zn or more than two kinds of the elements is or are denoted to be M. Then a hexagonal ferrite magnet contains the A, the R, an Fe and the M. The constituent ratio of the of the total of the respective metallic elements of these A, R, Fe and M is A: 1 to 13 atomic %, R: 0.5 to 10 atomic %, Fe: 80 to 95 atomic % and M: 0.1 to 5 atomic % to the quantity of all the metallic elements and when the content in the vicinities of the centers of the crystal grains of the R is 3 wt.% or lower, 4 wt.% or higher of the R is contained in the vicinity of the crystal grain boundary.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hexagonal ferrite suitably used as a permanent magnet material for an automobile motor or the like, and more particularly to a hexagonal ferrite having a magnetoplumbite type structure.

[0002]

2. Description of the Related Art Magnet plumbite type (M type) hexagonal Sr ferrite or Ba ferrite is mainly used as an oxide permanent magnet material, and these sintered magnets and bonded magnets are manufactured. ing.

[0003] Of the magnet properties, particularly important are the residual magnetic flux density (Br) and the intrinsic coercive force (HcJ).

[0004] Br is determined by the density of the magnet and its degree of orientation,
It is determined by the saturation magnetization (4πIs) determined by the crystal structure, and is expressed by Br = 4πIs × degree of orientation × density. The 4πIs of M-type Sr ferrite and Ba ferrite is about 4.65 kG. Density and degree of orientation,
Even in the case of the sintered magnet that can obtain the highest value, 98
% Is the limit. Therefore, Br of these magnets
Is limited to about 4.46 kG, and high B of 4.5 kG or more
Obtaining r has heretofore been virtually impossible.

The present inventors have disclosed in Japanese Patent Application Laid-Open No. Hei 9-115715 that by adding an appropriate amount of, for example, La and Zn to M-type ferrite, 4πIs can be increased up to about 200G.
It has been found that Br can be increased to 4.5 kG or more. However, in this case, since the anisotropic magnetic field ( _HA ) described later decreases, it was difficult to simultaneously obtain Br of 4.5 kG or more and HcJ of 3.5 kOe or more.

HcJ is the anisotropic magnetic field ｛H_A(= 2K₁/ I
s) The product (H) of｝ and the single domain particle ratio (fc)_A× fc)
Is proportional to Where K₁Is the crystal magnetic anisotropy constant
It is a constant determined by the crystal structure like Is. M type B
For a ferrite, K₁= 3.3 × 10⁶erg / cm^ThreeIn
In the case of M-type Sr ferrite, K₁= 3.5 × 10⁶er
g / cm ^ThreeIt is. Thus, M-type Sr ferrite has the largest
K₁Is known to have₁No more improvement
It was difficult to do.

The demagnetizing factor determined by the shape of the particles is N
Then, as shown in the following equation 1, as N becomes larger, a larger demagnetizing field is applied to the particles, thereby deteriorating HcJ. HcJ∝ (2K ₁ / Is−NIs) (1)

Generally, when the aspect ratio of a particle increases (flatten), N increases and HcJ deteriorates.

On the other hand, when the ferrite particles are in a single magnetic domain state, it is necessary to rotate the magnetization against the anisotropic magnetic field in order to reverse the magnetization, and thus the maximum HcJ is expected. In order to convert the ferrite particles into single domain particles, it is necessary that the size of the ferrite particles be equal to or less than the critical diameter (dc) described below.

Dc = 2 (k · Tc · K ₁ / a) ^1/2 / Is ²

Here, k is the Boltzmann constant, Tc is the Curie temperature, and a is the distance between iron ions. In the case of M-type Sr ferrite, dc is about 1 μm. For example, when manufacturing a sintered magnet, it is necessary to control the crystal grain size of the sintered body to 1 μm or less. Conventionally, it has been difficult to realize such fine crystal grains at the same time as high density and high degree of orientation for obtaining high Br. However, the present inventors have disclosed in Japanese Patent Application Laid-Open No. 6-53064 a new method. A manufacturing method was proposed, and it was shown that high characteristics could not be obtained. However, also in this method, when Br is 4.4 kG, H
The cJ was about 4.0 kOe, and it was difficult to maintain a high Br of 4.4 kG or more and simultaneously obtain a high HcJ of 4.5 kOe or more.

In order to control the crystal grain size of the sintered body to 1 μm or less, it is necessary to reduce the grain size in the forming step to preferably 0.5 μm or less in consideration of the grain growth in the sintering step. is there. When such fine particles are used, there is a problem that productivity generally decreases due to an increase in molding time and cracks during molding. For this reason, it has been very difficult to achieve both high characteristics and high productivity.

On the other hand, in order to obtain a high HcJ, Al ₂ O ₃
It has been conventionally known that the addition of Cr ₂ O ₃ is effective. In this case, since Al ³⁺ and Cr ³⁺ have the effect of replacing Fe ³⁺ having an “upward” spin in the M-type structure to increase _HA and suppress grain growth, it is 4.5 kOe or more. High HcJ is obtained. However, the sintering density tends to decrease as Is decreases, so that the Br decreases significantly. For this reason, only about 4.2 kG Br was obtained at the maximum with a composition in which HcJ was 4.5 kOe.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to increase the saturation magnetization and magnetic anisotropy of M-type ferrite at the same time to achieve a high residual magnetism that cannot be achieved with the conventional M-type hexagonal ferrite magnet. An object of the present invention is to realize a hexagonal ferrite magnet having a magnetic flux density and a high coercive force.

[0015]

This and other objects are achieved by any one of the following constitutions (1) to (3). (1) At least one element selected from Sr, Ba and Ca is A, one or more of La, Pr, Nd and Ce is R, and any one of Co, Ni and Zn A species or two or more species are M,
R, Fe and M, and the A, R, Fe and M
The total composition ratio of each metal element is A: 1 to 13 atomic%, R: 0.05 to 10 atomic%, Fe: 80 to 95 atomic%, M: 0.1 to A hexagonal ferrite magnet containing 5 atomic% and containing 4 wt% or more near crystal grain boundaries when the content of R near the crystal grain center is 3 wt% or less. (2) The hexagonal ferrite magnet according to (1), wherein when the content of the element M near the center of the crystal grain is 1 wt% or less, the content of the element M is more than 1 wt% near the crystal grain boundary. (3) The hexagonal ferrite magnet according to (1) or (2), which is a magnetoplumbite ferrite.

[0016]

[Action] Among the properties of the hexagonal ferrite magnet, HcJ is usually much smaller than the value expected from single domain particle theory. One of the causes is that the particle size is larger than the critical diameter of a single magnetic domain as described above, but in many cases, this cannot be explained alone.

As a result of careful observation of the sintered body by TEM, the present inventors have found that, as shown in FIG. 25, some of the crystal grains 1 have a stacking fault 2 on a plane orthogonal to the c-axis. I figured it out. Note that, in the drawing, the arrow c indicates the c-axis direction.

Here, for example, Japanese Patent Application No. 9-56856 (International Publication WO98 / 38654) and Japanese Patent Application Laid-Open No. 10-1499.
As described in JP-A-10, Sr ²⁺ is converted to La
^In the case of an M-type Sr ferrite composition in which Fe ³⁺ is replaced by Co ²⁺ with ³⁺ , both the saturation magnetization which is a basic magnetic property depending on the crystal structure and the crystal magnetic anisotropy constant (K1) increase. As a result, high characteristics can be obtained. However, the present inventors have found for the first time that stacking faults are particularly likely to occur when a hexagonal ferrite magnet having a composition substituted with elements having different valences and ionic radii is manufactured by a conventional manufacturing method. Further, they have found that due to such stacking faults, high crystal magnetic anisotropy may not be sufficiently reflected in coercive force, which is a magnet property.

The present inventors have disclosed a production method (post-addition method) described in Japanese Patent Application No. 9-273936.
Better magnetic properties were obtained, and it was found that the ferrite magnet produced by this method had two Curie temperatures, but as a result of further studies, stacking faults were extremely reduced at this time. This led to the present invention.

Further, as a method of reducing stacking faults, a method of increasing R is effective. In addition, Japanese Patent Application No. 9
As described in Japanese Patent No. 273932, a method of producing an atmosphere containing excess oxygen, specifically, an oxygen partial pressure of more than 0.2 atm, in firing hexagonal ferrite is also effective.

Hexagonal ferrite such as a magnetoplumbite structure has oxygen ions (O ²⁻ ) that are ABAB ...
, And has a structure in which part of oxygen ions is replaced by Sr ²⁺ , Ba ^2+, Ca ^{2+, and the} like. In addition, small ions such as iron ions (Fe ³⁺ ) are located in gaps between layers formed of O ²⁻ and Sr ²⁺ . Generally, stacking faults are defined as AB
The stacking faults such as AB... Are partially disordered in the stacking order. The stacking faults in this specification will be described in more detail as follows.

As shown in FIG. 1, the M-type hexagonal ferrite has a structure in which S layers and R layers are alternately laminated, such as S layer / R layer / S * layer / R * layer. ing. Where S
* And R * are obtained by rotating S and R by 180 degrees about the c-axis. From the following experimental example (TEM-EDS analysis),
The possibility that the stacking fault is a portion where the S layer (spinel layer) portion has abnormally grown has increased. This is, for example, Journal
of Solid State Chemistry vol. 26, P1-6 (1978), which is called "Intergrowth Layer".

The hexagonal ferrite containing R and M has many stacking faults. By reducing the stacking faults,
Obtaining high characteristics is the first finding by the present inventors. Note that ideally, the number of defects is zero, but in practice, the number of crystal grains having stacking faults is n
Where N / N = N, where N is the total number of crystal grains.
It has been found that high characteristics can be obtained even in the range of 0.05 to 0.35.

The cause of the deterioration of the magnetic properties of the ferrite magnet when such stacking faults are present is presumed to be as follows. First, when the stacking fault is a non-magnetic layer,
It is considered that the crystal grains (grains) are magnetically separated. This is effectively the same as the flattening of the particles, the demagnetizing factor (N) increases, and according to the above equation 1,
HcJ deteriorates. Secondly, if the stacking fault is a spinel layer exhibiting soft magnetism, it is considered that the soft magnetic layer forms a closed magnetic circuit and the effective crystal magnetic anisotropy decreases.

The present inventors have also disclosed the above-mentioned Japanese Patent Application No. 9-27.
In 3936, excellent magnetic properties were obtained by the production method (post-addition method) described therein, and it was found that a ferrite magnet produced by this method had two Curie temperatures, At this time, among the elements added later, it was found for the first time that the concentration of the element R such as La was low at the center of the crystal grain and relatively high near the grain boundary and at the triple point.

Furthermore, at this time, it has been found that the distribution of the element M such as Co is similar to that of the element R, although the analysis becomes difficult if the amount is small, and the distribution is sometimes unclear.

Thus, a ferrite magnet having excellent magnetic properties can be obtained by employing a structure in which R such as La or M such as Co is present in a higher concentration near the grain boundary than near the center of the crystal grain. The cause is presumed as follows. First, it is known that Sr ferrite containing La and Co has large crystal magnetic anisotropy. Therefore, if such an element exists in high concentration near the grain boundary,
It is considered that a magnetic phase having large anisotropy exists near the grain boundary. It is known that such a structure is easy to obtain a high coercive force, for example, by suppressing generation of reverse magnetic domains. Second, since the concentration of R or Co is low at the center of the crystal grain, the above stacking faults are reduced.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION The hexagonal ferrite magnet of the present invention has at least one selected from Sr, Ba and Ca.
A, R, at least one of La, Pr, Nd and Ce, R, Co, Ni and Z
n is M, A, R, F
e and M, and the total composition ratio of each of the metal elements A, R, Fe and M is as follows: A: 1 to 13 atomic%, R: 0.05 to 10 atomic%, based on the total amount of metal elements. ,
Fe: 80 to 95 atomic%, M: 0.1 to 5 atomic%, and when the content of R near the center of the crystal grain is 3 wt% or less, 4 wt% or more, particularly 5 wt% near the crystal grain boundary. It contains the above.

Preferably, when the content of the element M near the center of the crystal grains is 1 wt% or less, the content of the element M is more than 1 wt% near the crystal grain boundaries.

As described above, by adopting a structure in which R and M are more present near the grain boundary than near the center of the crystal grain, excellent magnetic characteristics can be obtained.

[0031] The hexagonal ferrite magnet of the present invention comprises Sr,
A is at least one element selected from Ba and Ca, R is an element having an ionic radius of 1.00 ° or more capable of taking a +3 valence or +4 valence, and contains A, R and Fe, and R is a crystal particle. Are more present in the vicinity of the grain boundaries than in the center. With such a structure, excellent magnetic characteristics can be obtained.

Such a structure can be said to be similar to a "core-shell structure" such as that found in a dielectric material such as barium titanate. Then, such a structure can be identified by analyzing by TEM-EDS.

Here, in order to form hexagonal ferrite,
Has an oxygen ion (O ^2-) And close size
And specifically, 1.00 to 1.60 on
It must be about gustrom. M is oxygen
ON (O^2-) And smaller than iron ions (Fe³⁺Close to)
It is necessary, specifically, 0.50 to 0.90 Angstroms
It needs to be about tromes.

The hexagonal ferrite magnet of the present invention only needs to contain the above-mentioned A, R and Fe, and other additives and the like are not particularly limited.
at least one element selected from a and Ca
And the ionic radius capable of taking +3 valence or +4 valence is 1.
An element having an ionic radius of 0.90 Å or more, particularly 1.00 to 1.60 Å, is defined as R.
When M is an element of Å or less, particularly 0.50 to 0.90 Å, it contains A, R, Fe and M.

Preferably, the total composition ratio of each metal element of A, R, Fe and M is 3 to 11 at%, R: 0.2 to 6 at%, F
e: 83 to 94 atomic%, M: 0.3 to 4 atomic%,
More preferably, A: 3 to 9 atomic%, R: 0.5 to 4
Atomic%, Fe: 86 to 93 atomic%, M: 0.5 to 3 atomic%.

In each of the above constituent elements, A represents Sr, B
It is at least one element selected from a and Ca. If A is too small, M-type ferrite will not be generated or non-magnetic phase such as α-Fe ₂ O ₃ will increase. A
Is too large, no M-type ferrite is formed or SrF
Non-magnetic phases such as eO _3-x increase. The ratio of Sr in A is preferably at least 51 atomic%, more preferably 7 atomic%.
It is 0 atomic% or more, and more preferably 100 atomic%.
If the ratio of Sr in A is too low, it becomes impossible to obtain both the saturation magnetization improvement and the remarkable improvement in coercive force.

R is preferably La, Nd, Pr or Ce. If R is too small, the solid solution amount of M will be small, and it will be difficult to obtain the effects of the present invention. If R is too large, non-magnetic hetero phases such as orthoferrite increase. The proportion of La in R is preferably 4
0 atomic% or more, more preferably 70 atomic% or more;
It is most preferable to use only La as R for improving the saturation magnetization. This is because, when comparing the solid solution limit amount to hexagonal M-type ferrite, La is the largest. Therefore, if the proportion of La in R is too low, the solid solution amount of R cannot be increased, and as a result, the solid solution amount of element M cannot be increased, and the effect of the present invention is reduced. I will.

The element M is preferably Co, Ni or Zn. If M is too small, the effects of the present invention will be difficult to obtain, and if M is too large, Br and HcJ will be conversely reduced, making it difficult to obtain the effects of the present invention. The ratio of Co in M is preferably at least 10 atomic%, more preferably at least 20 atomic%. If the ratio of Co is too low, the improvement of the coercive force becomes insufficient.

Here, there is a correlation between the contents of R and M and the number of crystal grains having defects, and the number of crystal grains having defects tends to increase as the amounts of R and M increase. However, when more R is present than the stoichiometric composition, the number of crystal grains having defects is reduced.

Although stacking faults can be identified relatively easily by TEM or the like, it is not practical to measure the total number of crystal grains in this case. Thus, for example, T
When the number of crystals in a certain visual field when observing a plane (a-plane) parallel to the c-axis of the anisotropic sintered magnet by EM (transmission electron microscope) is measured, and the total number of the crystal grains is N The number of crystal grains having defects found in the crystal grains is assumed to be n, and is estimated as the above number. Here, the magnification of the observed TEM is 1000 to 100,000 times, particularly 10,000 to 20 times.
2,000 times is preferable, and the visual field to be observed is preferably 2 or more visual fields, particularly 2 to 10 visual fields, and N is 20 to 50.
It is about 0. The number of defects existing in a crystal grain is usually about one or two, but may be three or more.

Preferably, the hexagonal magnetoplumbite-type ferrite is represented by A _{1 -x} R _x (Fe _{12 -y} M _y ) _z O _19. ≦ x ≦ 0.9, especially 0.04 ≦
x ≦ 0.6, 0.04 ≦ y ≦ 0.5, 0.8 ≦ x / y ≦
5, 0.7 ≦ z ≦ 1.2.

More preferably, 0.04 ≦ x ≦ 0.
5, 0.04 ≦ y ≦ 0.5, 0.8 ≦ x / y ≦ 5, 0.
7 ≦ z ≦ 1.2, more preferably 0.1 ≦ x ≦
0.4, 0.1 ≦ y ≦ 0.4, 0.8 ≦ z ≦ 1.1, and particularly preferably 0.9 ≦ z ≦ 1.05.

In the above formula 2, if x is too small, that is, if the amount of the element R is too small, the solid solution amount of the element M in the hexagonal ferrite cannot be increased, and the effect of improving the saturation magnetization and / or the anisotropic magnetic field The improvement effect becomes insufficient. If x is too large, substitutional solid solution of the element R in the hexagonal ferrite will not be possible, and for example, orthoferrite containing the element R will be generated and the saturation magnetization will decrease. If y is too small, the effect of improving the saturation magnetization and / or the effect of improving the anisotropic magnetic field become insufficient. If y is too large, the element M cannot be substituted and solid-solved in the hexagonal ferrite. Further, even in a range where the element M can be substituted for solid solution, the anisotropy constant (K ₁ ) and the anisotropic magnetic field (H _A ) greatly deteriorate. If z is too small, the non-magnetic phase containing Sr and the element R increases, so that the saturation magnetization decreases.
If z is too large, the α-Fe ₂ O ₃ phase or the nonmagnetic spinel ferrite phase containing the element M increases, and the saturation magnetization decreases. Note that the above formula is defined as including no impurities.

In the above equation (2), even if x / y is too small,
Even if it is too large, the valence of element R and element M cannot be balanced.
As a result, a different phase such as W-type ferrite is easily generated. Former
Since element M is divalent, the element R is a trivalent ion.
In this case, ideally, x / y = 1. Note that x / y exceeds 1
The reason that the allowable range is large in the region is that even if y is small,
³⁺→ Fe²⁺Valence can be balanced by the reduction of
You.

In the above formula (2) representing the composition, the number of atoms of oxygen (O) is 19, which means that when R is all trivalent and x = y, z = 1, It shows a stoichiometric composition ratio. The number of oxygen atoms varies depending on the type of R and the values of x, y, and z. Further, for example, when the firing atmosphere is a reducing atmosphere, oxygen deficiency (vacancy) may occur. Further, Fe is M
Usually, trivalent is present in the type ferrite, but this may change to divalent or the like. Also, M such as Co
The valence of the element represented by may also change, so that the ratio of oxygen to the metal element changes. In this specification, the number of oxygen atoms is indicated as 19 regardless of the type of R and the values of x, y, and z, but the actual number of oxygen atoms slightly deviates from the stoichiometric composition ratio. Is also good.

The composition of the ferrite can be measured by a fluorescent X-ray quantitative analysis or the like. The presence of the main phase is confirmed by X-ray diffraction, electron diffraction and the like.

The magnet powder may contain B ₂ O ₃ . By including B ₂ O ₃ , the calcining temperature and the sintering temperature can be lowered, which is advantageous in production. B ₂ O ₃
Is preferably 0.5% by weight or less of the whole magnet powder. If the B ₂ O ₃ content is too large, the saturation magnetization will be low.

The magnet powder may contain at least one of Na, K and Rb. These when converted into Na ₂ O, K ₂ O and Rb ₂ O, respectively, the total content thereof is preferably not more than 3 wt% of the total magnetic powder. If these contents are too large, the saturation magnetization will be low. When these elements expressed in M ^I, M ^I in ferrite is contained, for example, in the form of ^{_{Sr 1.3-2a R a M I a-}} 0.3 Fe 11.7 M 0.3 O 19. In this case, 0.3 <a ≦ 0.
It is preferably 5. When a is too large, in addition to the saturation magnetization becomes low, a problem that the element M ^I is thus a large amount of evaporation occurs during firing.

In addition to these impurities, for example, Si,
Al, Ga, In, Li, Mg, Mn, Ni, Cr, C
u, Ti, Zr, Ge, Sn, V, Nb, Ta, Sb,
As, W, Mo, etc. in the form of oxides, each containing 1% by weight or less of silicon oxide, 5% by weight or less of aluminum oxide, 5% by weight or less of gallium oxide, 3% by weight or less of indium oxide,
1% by weight or less of lithium oxide, 3% by weight of magnesium oxide
Below, manganese oxide 3% by weight, nickel oxide 3% by weight, chromium oxide 5% by weight, copper oxide 3% by weight, titanium oxide 3% by weight, zirconium oxide 3% by weight, germanium oxide 3% by weight , Tin oxide 3% by weight or less, vanadium oxide 3% by weight or less, niobium oxide 3
% By weight, 3% by weight or less of tantalum oxide, 3% by weight or less of antimony oxide, 3% by weight or less of arsenic oxide, 3% by weight or less of tungsten oxide, and 3% by weight or less of molybdenum oxide.

Also, the hexagonal ferrite magnet of the present invention
Preferably at least two different Curie temperatures Tc
1, Tc2, and the two different Curie temperatures Tc
1, Tc2 is 400 to 470 ° C.
1, the absolute value of the difference between Tc2 is 5 ° C. or more. By having two different Curie temperatures in this way, the squareness Hk
/ HcJ is remarkably improved.

The Curie temperature can be determined from a change point in the magnetization (σ) -temperature (T) curve of the magnet. More specifically, the temperature is obtained from the temperature at the intersection of the tangent to the low-temperature curve at the changing point of the σ-T curve and the temperature axis, according to a conventional method. The absolute value of the difference between the two different Curie points Tc1 and Tc2 is 5 ° C. or more, preferably 10 ° C. or more. The upper limit is not particularly limited, but 465 ° C.
It is about. Their Curie temperatures are between 400 and 470
° C, preferably in the range of 430-460 ° C. This 2
One Curie temperature is considered to be because the structure of the ferrite crystal of the present invention has a two-phase structure of M-type ferrite that is magnetically different due to a manufacturing process described below. However, in the ordinary X-ray diffraction method, an M-phase single phase is detected.

The squareness Hk / HcJ is preferably at least 90%, particularly preferably at least 92%. The maximum is 95%. The magnet of the present invention preferably has a degree of orientation Ir / Is of 96.5% or more, more preferably 99.5% or more.
It is preferably at least 7%. The highest is 98%
To the extent. By improving the degree of orientation, a high Br
Is obtained. Also, in the molded article, since the value of the degree of magnetic orientation is also affected by the density of the molded article, the surface of the molded article is measured by X-ray diffraction, and the molding obtained by the surface index and the intensity of the appearing peak is performed. The degree of crystallographic orientation of the body (X-ray orientation) is important. The degree of X-ray orientation of the molded body controls the value of the degree of magnetic orientation of the sintered body to a considerable extent. Preferably, ΣI (00L) / ΣI (hkL) is used as the X-ray orientation degree. (00L) is c such as (004) or (006)
This is a display that generically names the surfaces, and $ I (00L) is (00L)
It is the sum of all peak intensities of the surface. Also, (hk
L) represents all detected peaks and ΔI (hk
L) is the sum of their intensities. Therefore, ΔI (0
0L) / ΣI (hkL) represents the degree of c-plane orientation. This ΔI (00L) / ΔI (hkL) is preferably 0.1.
It is preferably 85 or more, more preferably 0.9 or more, and its upper limit is about 1.0.

Next, a method for producing a sintered ferrite magnet will be described. The above ferrite sintered magnet is usually made of A (A is Sr, Ba, Ca), R (R is
Element having an ionic radius capable of taking +3 valence or +4 valence and having an ion radius of 1.00 angstroms or more: preferably La, Pr, N
d or Ce), M (M is an element having an ionic radius of 0.90 angstroms or less: preferably C
o, Ni or Zn) -containing compound powder,
At least one or two or more of these raw material powders;
The mixture of Fe-containing oxide powders is calcined. Then, after calcination, the above A (A is Sr, Ba, C
a), R (R is an element capable of taking a valence of +3 or +4 and having an ionic radius of 1.00 angstroms or more: preferably La, Pr, Nd or Ce), M (M
Is manufactured by adding and mixing at least one or two or more of powders of a compound containing an element having an ionic radius of 0.90 angstroms or less: preferably Co, Ni or Zn). A (where A is Sr, B
a, Ca), R (R is an element capable of taking a valence of +3 or +4 and having an ionic radius of 1.00 angstroms or more: preferably La, Pr, Nd or Ce), M
(M is an element having an ionic radius of 0.90 angstroms or less: preferably Co, Ni or Zn) as the powder of the compound containing an oxide or a compound which becomes an oxide by firing, for example, carbonate, hydroxide Substances, nitrates and the like. The average particle size of the raw material powder is not particularly limited, but the iron oxide is preferably a fine powder, and the average particle size of the primary particles is preferably 1 μm or less, particularly preferably 0.5 μm or less. In addition, in addition to the above-mentioned raw material powder, B ₂ O ₃ and the like and other compounds such as Si, Al, Ga,
n, Li, Mg, Mn, Ni, Cr, Cu, Ti, Z
r, Ge, Sn, V, Nb, Ta, Sb, As, W, M
A compound containing o or the like may be contained as an additive or an impurity such as an unavoidable component.

The calcination is performed, for example, in the
The heat treatment may be performed at 1350 ° C. for 1 second to 10 hours, particularly about 1 second to 3 hours.

The calcined body thus obtained has a substantially magnetoplumbite-type ferrite structure, and the primary particles have an average particle size of preferably 2 μm or less, more preferably 1 μm or less, and still more preferably. Is 0.1-1μ
m, most preferably 0.1-0.5 μm. The average particle size may be measured with a scanning electron microscope.

Next, after pulverizing the calcined body or at the time of pulverizing, the above A (A is Sr, Ba, Ca) and R (R is
Element having an ionic radius capable of taking +3 valence or +4 valence and having an ion radius of 1.00 angstroms or more: preferably La, Pr, N
d or Ce), M (M is an element having an ionic radius of 0.90 angstroms or less: preferably C
o, Ni or Zn) is produced by mixing, molding and sintering at least one kind or two or more kinds of powders of a compound containing (o, Ni or Zn). Specifically, it is preferable to manufacture according to the following procedures. The amount of the compound powder added is 1
It is preferably from 100 to 100% by volume, more preferably from 5 to 70% by volume, particularly preferably from 10 to 50% by volume.

The addition time of the compound is not particularly limited as long as it is after calcination and before calcination, but it is preferable to add the compound at the time of pulverization described below. The type and amount of the raw material powder to be added are arbitrary, and the same raw material may be added separately before and after calcination. However, 30% or more of the total amount,
In particular, 50% or more is preferably added in a post-process performed after calcination. The average particle size of the compound to be added is usually about 0.1 to 2 μm.

In the present invention, wet molding is performed using a molding slurry containing magnetic oxide particles, water as a dispersion medium, and a dispersant. To further enhance the effect of the dispersant, wet molding is performed. It is preferable to provide a wet grinding step before the wet molding step. Further, when calcined particles are used as the oxide magnetic particles, the calcined particles are generally in a granular form. It is preferable to provide a pulverizing step. In addition, when the oxide magnetic particles are manufactured by a coprecipitation method or a hydrothermal synthesis method, the dry coarse pulverizing step is not usually provided, and the wet pulverizing step is not essential. Is preferably provided with a wet grinding step. Hereinafter, a case where the calcined particles are used as the oxide magnetic particles and a dry coarse pulverization step and a wet pulverization step are provided will be described.

In the dry coarse pulverization step, pulverization is usually performed until the BET specific surface area becomes about 2 to 10 times. The average particle size after pulverization is about 0.1-1 μm, and the BET specific surface area is 4-1
It is preferably about 0 m ² / g, and the CV of the particle size is 80%.
Hereinafter, it is particularly preferable to maintain the content at 10 to 70%. The pulverizing means is not particularly limited. For example, a dry vibrating mill, a dry attritor (medium stirring type mill), a dry ball mill, or the like can be used, and it is particularly preferable to use a dry vibrating mill. The pulverization time may be appropriately determined according to the pulverization means. In addition, it is preferable to add a part of the raw material powder during the dry grinding step.

The dry coarse pulverization also has an effect of reducing the coercive force HcB by introducing crystal strain into the calcined particles. Due to the decrease in coercive force, aggregation of particles is suppressed, dispersibility is improved, and the degree of orientation is also improved. The crystal strain of the particles is released in a later sintering step, and can be made a permanent magnet.

Incidentally, in the case of dry coarse pulverization, SiO
₂ and CaCO ₃ which becomes CaO upon firing are added. SiO ₂ and CaCO ₃ may be partially added before calcination, in which case the improvement in properties is observed.

After the dry coarse pulverization, a pulverization slurry containing the pulverized particles and water is prepared, and wet pulverization is performed using the slurry. The content of the calcined particles in the slurry for pulverization is 10
It is preferably about 70% by weight. The pulverizing means used for the wet pulverization is not particularly limited, but usually a ball mill, an attritor, a vibration mill, or the like is preferably used. The pulverization time may be appropriately determined according to the pulverization means.

After the wet pulverization, the pulverizing slurry is concentrated to prepare a molding slurry. Concentration may be performed by centrifugation or the like. The content of the calcined particles in the molding slurry is preferably about 60 to 90% by weight.

In the wet molding step, molding in a magnetic field is performed using a molding slurry. Molding pressure is 0.1-0.5ton / cm
^The applied magnetic field may be about ² to 15 kOe.

It is preferable to use a non-aqueous dispersion medium for the molding slurry because a high degree of orientation can be obtained. In the present invention, a molding slurry in which a dispersant is added to an aqueous dispersion medium is preferably used. The dispersant preferably used in the present invention is an organic compound having a hydroxyl group and a carboxyl group, a neutralized salt thereof, a lactone thereof, an organic compound having a hydroxymethylcarbonyl group, or an acid compound. It is preferable that the compound is an organic compound having an enol-type hydroxyl group which can be dissociated, or a neutralized salt thereof.

When a non-aqueous dispersion medium is used,
For example, as described in JP-A-6-53064, a dispersion medium is prepared by adding a surfactant such as oleic acid to an organic solvent such as toluene or xylene. By using such a dispersion medium, it is possible to obtain a high degree of magnetic orientation of about 98% at the maximum even when ferrite particles having a submicron size that are difficult to disperse are used.

Each of the above organic compounds has 3 to 20 carbon atoms,
It is preferably 4 to 12, and a hydroxyl group is bonded to 50% or more of carbon atoms other than the carbon atom double-bonded to the oxygen atom. If the number of carbon atoms is 2 or less, the effects of the present invention cannot be realized. Further, even when the number of carbon atoms is 3 or more, the effect of the present invention cannot be realized if the bonding ratio of the hydroxyl group to carbon atoms other than the carbon atom double-bonded to the oxygen atom is less than 50%. The bonding ratio of the hydroxyl group is limited for the above-mentioned organic compound, and is not limited for the dispersant itself. For example, when a lactone of an organic compound (hydroxycarboxylic acid) having a hydroxyl group and a carboxyl group is used as the dispersant, the limitation of the bonding ratio of the hydroxyl group is applied to the hydroxycarboxylic acid itself, not to the lactone.

The basic skeleton of the organic compound may be linear or cyclic, and may be saturated or contain an unsaturated bond.

As the dispersant, specifically, hydroxycarboxylic acid or a neutralized salt thereof or a lactone thereof is preferable. Particularly, gluconic acid (C = 6; OH = 5; COOH
= 1) or a neutralized salt thereof or a lactone thereof, lactobionic acid (C = 12; OH = 8; COOH = 1), tartaric acid (C = 4; OH = 2; COOH = 2) or a neutralized salt thereof, glucoheptone Acid γ-lactone (C = 7; OH
= 5) is preferred. Among these, gluconic acid or its neutralized salt or its lactone is preferable because it has a high effect of improving the degree of orientation and is inexpensive.

As the organic compound having a hydroxymethylcarbonyl group, sorbose is preferred.

As the organic compound having an enol-type hydroxyl group which can be dissociated as an acid, ascorbic acid is preferable.

In the present invention, citric acid or a neutralized salt thereof can also be used as a dispersant. Citric acid has a hydroxyl group and a carboxyl group, but does not satisfy the condition that a hydroxyl group is bonded to 50% or more of carbon atoms other than a carbon atom double-bonded to an oxygen atom. However, the effect of improving the degree of orientation is recognized.

For some of the above preferred dispersants,
The structure is shown below.

[0074]

Embedded image

Further, Japanese Patent Application No. 10-159 filed by the present applicant
A dispersant as described in JP-A-927 may be used. That is, the dispersant is a sugar having a carboxyl group or a derivative thereof, or an organic compound that is a salt thereof. The dispersant has a carbon number of 21 or more.

Since the viscosity of the slurry increases as the molecular weight of the dispersant increases, if the viscosity of the slurry is too high, the viscosity may be reduced by, for example, a method of hydrolyzing the dispersant with an enzyme or the like. .

The saccharides constituting the basic skeleton in the dispersant include polysaccharides such as cellulose and starch, as well as reduced derivatives, oxidized derivatives and dehydrated derivatives thereof, and a wide range of derivatives such as amino sugars and thiols. It is a compound that also includes sugars and the like.

Examples of the saccharide having a carboxyl group include O
It is preferable that at least a part of the H group forms an ether bond with an organic compound having a carboxyl group. As such a compound, an ether of a saccharide and glycolic acid is preferable, and specifically, carboxymethyl cellulose or carboxymethyl starch is preferable. In these compounds, the degree of substitution of the carboxymethyl group, that is, the degree of etherification is 3 at the maximum, but the degree of etherification is preferably 0.4 or more. If the degree of etherification is too small, it becomes difficult to dissolve in water. Note that carboxymethylcellulose is usually synthesized in the form of a sodium salt, and this sodium salt can also be used as a dispersant in the present invention. However, an ammonium salt is preferably used because it has little adverse effect on magnetic properties. Oxidized starch is also a saccharide having a carboxyl group in the molecule, and is a dispersant preferably used in the present invention.

The degree of orientation by magnetic field orientation is determined by the pH of the slurry.
Affected by Specifically, if the pH is too low, the degree of orientation decreases, which affects the residual magnetic flux density after sintering. When a compound exhibiting an acid property in an aqueous solution, such as hydroxycarboxylic acid, is used as the dispersant, the pH of the slurry becomes low. Therefore,
For example, it is preferable to adjust the pH of the slurry by adding a basic compound together with the dispersant. As the basic compound, ammonia and sodium hydroxide are preferable. Ammonia may be added as aqueous ammonia. In addition, by using the sodium salt of hydroxycarboxylic acid, the pH can be prevented from lowering.

As an auxiliary component like a hexagonal ferrite magnet,
T SiO_TwoAnd CaCO_ThreeWhen adding a dispersant and
When using hydroxycarboxylic acid and its lactone,
Mainly when preparing slurry for molding
Both are SiO_TwoAnd CaCO _ThreeLeaked, and HcJ
And the desired performance cannot be obtained. Also on
When the pH is increased by adding the basic compound
Contains SiO_TwoAnd CaCO_ThreeMore outflow
You. In contrast, calcium salts of hydroxycarboxylic acids
If is used as a dispersant, SiO_TwoAnd CaCO_Threeof
Outflow is suppressed. However, if the above basic compound is added,
Or when using sodium salt as a dispersant
And SiO_TwoAnd CaCO_ThreeOver target composition
If added, SiO in the magnet_TwoOf CaO and CaO
Can be prevented. In addition, when using ascorbic acid,
In the case, SiO_TwoAnd CaCO_ThreeAlmost no outflow
I can't.

For the above reasons, the pH of the slurry is preferably 7 or more, more preferably 8 to 11.

The type of the neutralizing salt used as the dispersing agent is not particularly limited, and may be any of a calcium salt and a sodium salt. For the above-mentioned reason, the calcium salt is preferably used. When a sodium salt is used as the dispersant or when ammonia water is added, there is a problem that, in addition to the outflow of subcomponents, cracks are easily generated in the formed body and the sintered body.

The dispersants may be used in combination of two or more.

The amount of the dispersant added is preferably 0.05 to 3.0% by weight, more preferably 0.10 to 2.0% by weight, based on the calcined particles which are the oxide magnetic particles. . If the amount of the dispersant is too small, the degree of orientation will not be sufficiently improved. On the other hand, if the amount of the dispersing agent is too large, cracks are likely to occur in the molded body and the sintered body.

When the dispersant is ionizable in an aqueous solution, for example, an acid or a metal salt, the amount of the dispersant to be added is an ion equivalent. That is, the amount of addition is determined in terms of organic components excluding hydrogen ions and metal ions.
When the dispersant is a hydrate, the amount of addition is determined excluding water of crystallization. For example, when the dispersant is calcium gluconate monohydrate, the amount to be added is calculated in terms of gluconate ions.

When the dispersant is made of lactone or contains lactone, the amount of addition is determined in terms of hydroxycarboxylic acid ions, assuming that all of the lactone is opened to form hydroxycarboxylic acid.

The timing of adding the dispersant is not particularly limited, and may be added during dry coarse pulverization, may be added during the preparation of a slurry for wet pulverization, or may be partially added during dry coarse pulverization. And the remainder may be added during wet grinding. Alternatively, it may be added by stirring or the like after wet pulverization. In any case, the effect of the present invention is realized because the dispersant is present in the molding slurry. However, the effect of improving the degree of orientation is higher at the time of pulverization, particularly at the time of dry coarse pulverization. In a vibration mill or the like used for dry coarse pulverization, larger energy is given to the particles than in a ball mill or the like used for wet pulverization, and the temperature of the particles increases, so that the chemical reaction is likely to proceed. Therefore, if a dispersant is added during dry coarse grinding,
It is considered that the amount of the dispersant adsorbed on the particle surface is increased, and as a result, a higher degree of orientation is obtained. Actually, when the residual amount of the dispersing agent in the molding slurry (which is considered to be almost equal to the adsorption amount) is measured, the amount of the dispersing agent added during the dry coarse grinding is larger than that when the dispersing agent is added during the wet grinding. The ratio of the residual amount to is increased. In addition, when the dispersant is added in a plurality of times,
What is necessary is just to set the addition amount of each time so that the total addition amount may be in the preferable range described above.

After the forming step, the formed body is subjected to a heat treatment at a temperature of 100 to 500 ° C. in the atmosphere or in nitrogen to sufficiently decompose and remove the added dispersant. Next, in the sintering step, the molded body is preferably for example 1150-12 in air.
Sintering is performed at a temperature of 50 ° C., more preferably 1160 to 1220 ° C. for about 0.5 to 3 hours to obtain an anisotropic hexagonal ferrite magnet.

The average crystal grain size of the magnet of the present invention is preferably 2 μm or less, more preferably 1 μm or less, and still more preferably 0.5 to 1.0 μm. In the present invention, the average crystal grain size exceeds 1 μm. However, a sufficiently high coercive force can be obtained. The crystal grain size can be measured by a scanning electron microscope. Incidentally, the resistivity is at least about 10 ⁰ [Omega] m.

The above compact was crushed using a crusher or the like, and the average particle size was 100 to 700 μm by sieving or the like.
m to obtain a magnetic field-oriented granule, which is subjected to dry magnetic field molding, and then sintered to obtain a sintered magnet.

After the calcination using the calcined body slurry, the powder may be dried and then fired to obtain magnet powder.

By using the hexagonal ferrite magnet of the present invention, the following effects can be generally obtained, and an excellent applied product can be obtained. In other words, if the shape is the same as that of a conventional ferrite product, the magnetic flux density generated from the magnet can be increased, so that a motor can achieve higher torque, etc., and if it is a speaker or headphone, the magnetic circuit can be strengthened. It can contribute to high performance of applied products, such as obtaining good sound quality with linearity. Also,
The size (thickness) of the magnet should be the same as before.
Can be made smaller (thinner), which can contribute to downsizing and weight reduction (thinner). Further, even in a motor in which the field magnet is conventionally a winding type electromagnet, it can be replaced with a hexagonal ferrite magnet, which contributes to weight reduction, shortening of the production process, and cost reduction. . Further, the coercive force (H
Because of its excellent temperature characteristics of cJ), it can be used even in low-temperature environments where there was a danger of low-temperature demagnetization (permanent demagnetization) of hexagonal ferrite magnets. Can be significantly improved in reliability.

The hexagonal ferrite magnet of the present invention is processed into a predetermined shape and used for a wide range of applications as described below.

For example, for fuel pump, power window, ABS, fan, wiper, power steering, active suspension, starter,
Automotive motors for door locks, electric mirrors, etc .; FD
For D spindle, VTR capstan, VTR rotary head, VTR reel, VTR loading, VT
For R camera capstan, VTR camera rotating head,
Motors for OA and AV equipment such as VTR camera zoom, VTR camera focus, boombox capstan, CD, LD, MD spindle, CD, LD, MD loading, CD, LD optical pickup, etc .; Motors for home appliances such as for refrigerator compressor, electric tool drive, electric fan, microwave oven fan, microwave plate rotation, mixer drive, dryer fan drive, shaver drive, electric toothbrush, etc .;
Motors for FA equipment such as robot axes, joint drive, robot main drive, machine tool table drive, machine tool belt drive, etc .; motor generators, magnets for speakers and headphones, magnetron tubes, magnetic field generation for MRI It is suitably used for devices, clampers for CD-ROMs, sensors for distributors, sensors for ABS, fuel / oil level sensors, magnet latches, and the like.

[0095]

EXAMPLES <Experimental Examples> The following materials were used as raw materials. Fe ₂ O ₃ powder (primary particle diameter 0.3 μm), 1000.0 g (including Mn, Cr, Si, Cl as impurities) SrCO ₃ powder (primary particle diameter 2 μm), 130.3 g (Ba, Ca as impurities (Including) Cobalt oxide 17.56 g La ₂ O ₃ 35.67 g

As an additive, 2.30 g of SiO ₂ powder (primary particle diameter: 0.01 μm) and 1.72 g of CaCO ₃ powder (primary particle diameter: 1 μm) were used.

The above starting materials and additives were pulverized with a wet attritor, dried and sized, and dried in air.
It was calcined at 250 ° C. for 3 hours to obtain a granular calcined body. As a result of measuring the magnetic properties of the obtained calcined body with a sample vibration magnetometer (VSM), the saturation magnetization σs was 68 emu / g, and the coercive force H was
cJ was 4.6 kOe.

The obtained calcined body (110 g) was mixed with Si
O ₂ (0.44g), CaCO ₃ a (1.38 g), were mixed respectively predetermined amounts, further calcium gluconate (1.
13 g), and the batch was shaken by a vibrating rod mill.
Dry coarse crushing for minutes. At this time, the strain due to the pulverization was introduced, and the HcJ of the calcined body particles was reduced to 1.7 kOe.

This operation was performed twice, 210 g of the obtained coarsely pulverized material was collected, and 400 cc of water was added as a dispersion medium and mixed to prepare a slurry for pulverization. The specific surface area of the calcined body is 7
Grinding was performed until m ² / g. The solid concentration of the slurry for grinding was 34% by weight.

Using this slurry for wet grinding, wet grinding was performed in a ball mill for 40 hours. The specific surface area after the wet pulverization was 8.5 m ² / g (average particle size: 0.5 μm). The pH of the slurry after the wet pulverization was 9 to 10.

After the wet pulverization, the slurry for pulverization was centrifuged to adjust the concentration of the calcined particles in the slurry to about 78% to obtain a slurry for molding. Compression molding was performed while removing water from the molding slurry. This molding was performed while applying a magnetic field of about 13 kOe in the compression direction. The obtained molded body was a cylindrical shape having a diameter of 30 mm and a height of 18 mm. The molding pressure was 0.4 ton / cm ² .

Next, after the molded body is heat-treated at 100 to 360 ° C. to sufficiently remove gluconic acid,
The temperature was raised at a rate of 5 ° C./min, and firing was performed by maintaining the temperature at 1220 ° C. for 1 hour to obtain a sintered body. The obtained sintered body was observed with a high-resolution TEM, and the composition of the stacking fault portion and the other portions was analyzed by EDS analysis. Each one
The average value measured at zero point is shown below.

Stacking fault portion (wt%) Portion other than stacking fault (wt%) Fe ₂ O ₃ 84.5 84.2 SrO 8.5 9.8 La ₂ O ₃ 3.4 3.7 CoO 2.6 0.9 SiO ₂ 0.8 1.0 CaO 0.2 0.4

In this case, since the analysis area (spot size) by EDS is wider than the width of the stacking fault, the composition of the stacking fault portion is affected by the other portions. It was confirmed that a large amount of Co was present in the portion. Further, the stacking fault was carefully observed with a high-resolution TEM (transmission electron microscope). FIG. 1 shows a general crystal structure of the hexagonal ferrite magnet of the present invention.
FIG. 2 shows a high-resolution TEM photograph of a stacking fault portion.
As shown in FIG. 1, the M-type hexagonal ferrite has a structure in which S layers and R layers are alternately stacked like an S layer / R layer / S * layer / R * layer. Here, S * and R * are
S and R are rotated by 180 degrees about the c-axis.
However, from FIG. 2, it was found that the stacking fault is a portion where the period is disordered. Note that the region indicated by C in the figure represents the length (unit cell or unit cell) corresponding to the lattice constant C. Here, it is considered that divalent ions such as Co enter the spinel layer. Therefore, if the stacking fault is considered to be "IntergrowthLayer" of the spinel layer, it can be explained that the Co concentration in the stacking fault portion is high. I understood.

Example 1 [Sintered magnet: Sample 1 (added after aqueous system)] The following materials were used as raw materials. Fe ₂ O ₃ powder (primary particle diameter 0.3 μm), 1000.0 g (including Mn, Cr, Si, Cl as impurities) SrCO ₃ powder (primary particle diameter 2 μm), 161.2 g (Ba and Ca as impurities Including)

As an additive, 2.30 g of SiO ₂ powder (primary particle diameter: 0.01 μm) and 1.72 g of CaCO ₃ powder (primary particle diameter: 1 μm) were used.

The starting materials and additives were pulverized with a wet attritor, dried and sized, and then dried in air.
It was calcined at 250 ° C. for 3 hours to obtain a granular calcined body.

With respect to the obtained calcined body (87.26 g),
_{SiO 2 (0.44g), CaCO 3} (1.38g), lanthanum carbonate _{[La 2 (CO 3) 3 ·} 8H 2 O ] (6.12 g
) And cobalt oxide (CoO) (1.63 g) were mixed, and calcium gluconate (1.13 g) was further added.
) Was added and dry coarsely ground for 20 minutes with a batch vibrating rod mill. At this time, the strain due to the pulverization was introduced, and the HcJ of the calcined body particles was reduced to 1.7 kOe.

This operation was performed twice to obtain the coarsely crushed material 1
77 g was collected, 37.25 g of the same iron oxide (α-Fe ₂ O ₃ ) as used as a raw material was added, and 400 cc of water was added as a dispersion medium and mixed to prepare a slurry for grinding. Grinding was performed until the calcined body had a specific surface area of 7 m ² / g. The solid concentration of the slurry for grinding was 34% by weight.

Using this slurry for wet grinding, wet grinding was performed in a ball mill for 40 hours. The specific surface area after the wet pulverization was 8.5 m ² / g (average particle size: 0.5 μm). The pH of the slurry after the wet pulverization was 9.5.

After the wet pulverization, the slurry for pulverization was centrifuged to adjust the concentration of the calcined particles in the slurry to 78% to obtain a slurry for molding. Compression molding was performed while removing water from the molding slurry. This molding is
This was performed while applying a magnetic field of about 13 kOe in the compression direction. The obtained molded body was a cylindrical shape having a diameter of 30 mm and a height of 18 mm. The molding pressure was 0.4 ton / cm ² .

Next, the molded body is heat-treated at 100 to 300 ° C. to sufficiently remove gluconic acid.
The temperature was raised at a rate of 5 ° C./min, and firing was performed by maintaining the temperature at 1220 ° C. for 1 hour to obtain a sintered body. The composition of the obtained sintered body was Sr _0.8 La _0.2 (Fe _11.8 Co _0.2 ) O ₁₉ . The structure of the a-plane of the obtained sintered body was observed with a TEM (transmission electron microscope). The magnification at this time is 1000
At 0x, the visual field was observed in two visual fields. As a result, the ratio n / N of the number n of the crystals having stacking faults to the number N (N = 80) of the entire crystal grains was 9/80. TEM photographs of the obtained samples are shown in FIGS. These enlarged photographs are shown in FIGS. 5 (upper half) and 6 (lower half), and FIGS. 7 (upper half) and 8 (lower half), respectively. Further, as a result of performing component analysis by EDS at the same time as the TEM observation, La was scarcely present at the central part in the grains, but was present more in the vicinity of grain boundaries and at the triple point. The results are shown in FIGS. Here, FIG. 9 shows an analysis result at a grain boundary portion, FIG. 10 shows an analysis result at the inside of a crystal grain, and FIG. 11 shows an analysis result at a triple point. Furthermore, for the observed arbitrary particles 1 and ₃ , La ₂ O ₃ and CoO were continuously analyzed in the order of the grain boundary → the inside of the particle → the grain boundary. The results are shown in FIGS. From these measurement results, it was confirmed that La and Co were also present at a higher concentration near the grain boundaries than inside the grains. When each sample was analyzed by X-ray diffraction, it was found that each sample was a single phase of M-type ferrite.

Further, after processing the upper and lower surfaces of the obtained sintered body, the residual magnetic flux density (Br) and the coercive force (HcJ and Hc
b) and maximum energy product [(BH) max], saturation magnetization (4π
Is), magnetic orientation (Ir / Is), squareness (Hk /
HcJ) was measured. Table 1 shows the results.

Next, a sample was prepared with a diameter of 5 mm and a height of 6.5 mm.
Processed to. The Curie temperature Tc was determined by measuring the temperature dependence of the magnetization in the c-axis direction using a VSM. As a result, the Curie temperature Tc of the sample No. 1 of the present invention was 44
It was found that there were two stages of 0 ° C and 456 ° C.

[0115]

[Table 1]

In Table 1, * represents a comparative sample.

Example 2 A molded article produced in the same manner as in Example 1 was used except that the oxygen concentration was 1%.
It was fired at 20% and 50%, and the magnetic properties, Curie temperature, and temperature coefficient of Br were measured in the same manner as in Example 1. Table 2 shows the results.

[0118]

[Table 2]

As is clear from Table 2, the magnetic properties of the obtained sintered body are improved as the oxygen concentration increases.

Further, the firing atmosphere O ₂ : 1% and 20%
Was observed with a TEM. The results are shown in FIGS. As is clear from FIGS. 16 and 17, it is understood that the defect increases when the oxygen concentration is low.

Comparative Example 1 [Sintered magnet: Sample 2 (added before solvent system)] The following materials were used as raw materials. Fe ₂ O ₃ powder (primary particle diameter 0.3 μm), 1000.0 g (including Mn, Cr, Si, Cl as impurities) SrCO ₃ powder (primary particle diameter 2 μm), 130.3 g (Ba, Ca as impurities (Including) Cobalt oxide 17.56 g La ₂ O ₃ 35.67 g

As an additive, 2.30 g of SiO ₂ powder (primary particle diameter: 0.01 μm) and 1.72 g of CaCO ₃ powder (primary particle diameter: 1 μm) were used.

The starting materials and additives were pulverized with a wet attritor, dried and sized, and then dried in air.
It was calcined at 250 ° C. for 3 hours to obtain a granular calcined body. As a result of measuring the magnetic properties of the obtained calcined body with a sample vibration magnetometer (VSM), the saturation magnetization σs was 68 emu / g, and the coercive force H was
cJ was 4.6 kOe.

The obtained calcined body (110 g) was mixed with Si
O ₂ (0.44g), CaCO ₃ a (1.38 g), respectively mixing predetermined amounts, 20 by the vibration rod mill batch
Dry coarse crushing for minutes. At this time, the strain due to the pulverization was introduced, and the HcJ of the calcined body particles was reduced to 1.7 kOe.

Next, the calcined powder was wet-pulverized in a ball mill for 40 hours using xylene as a non-aqueous solvent and oleic acid as a surfactant. Oleic acid was added in an amount of 1.3% by weight based on the calcined powder. The calcined body powder in the slurry was 33% by weight. The pulverization was performed until the specific surface area became 8 to 9 m ² / g.

After the wet pulverization, the slurry for pulverization was centrifuged to adjust the concentration of ferrite particles in the slurry to about 85%, thereby obtaining a slurry for molding. Compression molding was performed while removing the solvent from the molding slurry. This molding was performed while applying a magnetic field of about 13 kOe in the compression direction. The obtained molded body was a cylindrical shape having a diameter of 30 mm and a height of 18 mm. The molding pressure was 0.4 ton / cm ² .

Next, the molded body was heat-treated at 100 to 360 ° C. to sufficiently remove oleic acid.
The temperature was raised at a rate of 5 ° C./min, and firing was performed by maintaining the temperature at 1220 ° C. for 1 hour to obtain a sintered body. The composition of the obtained sintered body was Sr _0.8 La _0.2 (Fe _11.8 Co _0.2 ) O ₁₉
Met. The obtained sintered body was observed with a TEM in the same manner as in Sample 1 described above. As a result, the total number of crystal grains N
The ratio n / N of the number n of the crystals having stacking faults to (N = 120) was 50/120. TEM photographs of the obtained sample are shown in FIGS. Further, as a result of performing component analysis by EDS at the same time as the TEM observation, unlike the above example, the La concentration hardly changed in the crystal grain, near the grain boundary, and at the triple point. The results are shown in FIGS. Here, FIG. 20 shows an analysis result at the grain boundary, FIG. 21 shows an analysis result at the inside of the crystal grain, and FIG. 22 shows an analysis result at the triple point. As a result, it was found that the amount of La in the crystal grains was reduced when the post-addition method was used in the examples. When each sample was analyzed by X-ray diffraction, it was found that each sample was a single phase of M-type ferrite.

Further, after processing the upper and lower surfaces of the obtained sintered body, the residual magnetic flux density (Br) and the coercive force (HcJ and Hc
b) and maximum energy product [(BH) max], saturation magnetization (4π
Is), magnetic orientation (Ir / Is), squareness (Hk /
HcJ) was measured. Table 1 shows the results.

Next, a sample was prepared with a diameter of 5 mm and a height of 6.5 mm.
Processed to. The Curie temperature Tc was determined by measuring the temperature dependence of the magnetization in the c-axis direction using a VSM. As a result, the Curie temperature Tc of Comparative Sample No. 2 was 444
It was found that the temperature was one stage of ° C.

Comparative Example 2 [Sintered magnet: (Sample 3: Zn
In Comparative Example 1, the raw material powder was changed so as to contain Zn instead of Co, and the final composition was Sr _0.8 R _0.3 (Fe _11.7 Zn _0.3 ) O ₁₉ (R = La, Ce, Pr , Nd, Sm) were obtained in the same manner as in Comparative Example 1, except that the sintered body was adjusted. The obtained sintered body was observed with a TEM in the same manner as in Sample 1 described above. As a result, the ratio n / N of the number n of crystals having stacking faults to the number N of all crystal grains is 0.6 to 0.8.
Met. Further, many crystals containing three or more stacking faults were observed in one crystal grain. Next, TEM-E
The composition of the stacking fault portion and the other portion was analyzed by DS. The average value measured for each of the ten points is shown below.

Stacking fault portion (wt%) Portion other than stacking fault (wt%) Fe ₂ O ₃ 83.99 84.65 SrO 6.49 7.22 La ₂ O ₃ 5.22 6.13 ZnO 4.30 2.00

From this, it was found that a large amount of Zn was present in the stacking fault portion. TEM photographs of these samples are shown in FIGS.

Comparative Example 3 The composition of the sintered body was changed to Sr _1-x La _x Fe _12-x Co _x
O ₁₉ (x = 0, 0.1, 0.2, 0.3, 0.4,
0.6), a sintered body was produced in the same manner as in Comparative Example 1, and observed by TEM. As a result, as shown in Table 3 below, the ratio of stacking faults was found to increase as the ratio of La and Co increased (x increased). Further, it was found that the Co concentration was high in these stacking fault portions.

[0134]

[Table 3]

Further, the magnetic properties of the sintered body were measured in the same manner as in Comparative Example 1. Table 4 shows the results. The magnetic properties (especially HcJ) of the sintered body improved as x increased in the range of x = 0 to 0.3, but deteriorated when x was 0.4 or more. This is considered to be a result of a multiplication of the characteristic improvement effect due to the inclusion of La and Co with the characteristic deterioration effect due to the increase in the ratio of stacking faults. Therefore, by keeping the ratio of stacking faults low, La and C
It is considered that the effect of o can be further enhanced.

[0136]

[Table 4]

[0137] Comparative Example 4 composition of the sintered _{body, Sr 0.7 La 0.3 Fe 11.7 Ni} 0.3 O 19 Sr 0.8 La 0.2 Fe 11.8 Mn 0.2 O 19 Sr 0.8 La 0.2 Fe 11.8 Cu 0.2 O 19 SrFe 11.7 Co 0.3 O 19 SrFe _A sintered body was prepared in the same manner as in Comparative Example 1 except that the _{thickness was changed to 11.6} Ti _0.2 O _19, and analyzed by TEM-EDS. As a result, Sr
Samples other than _0.8 La _0.2 Fe _11.8 Mn _0.2 O ₁₉ were confirmed to have similar defects, and it was confirmed that the element M of the sintered body was present at a high concentration in the defect portions. The effects of the present invention are clear from the above examples.

[0138]

As described above, according to the present invention, by simultaneously increasing the saturation magnetization and magnetic anisotropy of M-type ferrite, a high residual magnetism that cannot be achieved with the conventional M-type hexagonal ferrite magnet is obtained. A hexagonal ferrite magnet having a magnetic flux density and a high coercive force can be realized.

[Brief description of the drawings]

FIG. 1 is a view showing a crystal structure of a hexagonal ferrite magnet of the present invention.

FIG. 2 is a TEM photograph of a defective portion obtained in an experimental example.

FIG. 3 shows the structure of the a-plane of the sintered magnet sample 1 of the present invention as T
It is the 1st drawing substitute photograph image | photographed by EM.

FIG. 4 shows the structure of the a-plane of the sintered magnet sample 1 of the present invention as T
It is the 2nd drawing substitute photograph image | photographed by EM.

FIG. 5 is an enlarged photograph (upper half) of FIG. 3;

FIG. 6 is an enlarged photograph (lower half) of FIG. 3;

FIG. 7 is an enlarged photograph (upper half) of FIG. 4;

FIG. 8 is an enlarged photograph (lower half) of FIG. 5;

FIG. 9 is a diagram showing a result of component analysis of a sintered magnet sample 1 of the present invention at a grain boundary portion by EDS.

FIG. 10 is a diagram showing the results of component analysis inside crystal grains by EDS of the sintered magnet sample 1 of the present invention.

FIG. 11 is a diagram showing the results of component analysis of the sintered magnet sample 1 of the present invention at the triple junction by EDS.

FIG. 12 is a TEM photograph showing a state in which La ₂ O ₃ and CoO are continuously analyzed from an arbitrary particle 1 at a grain boundary → inside of the particle → grain boundary.

FIG. 13 is a graph showing the results of continuous analysis of La ₂ O ₃ and CoO for an arbitrary particle 1 in the order of grain boundary → inside of the particle → grain boundary.

FIG. 14 is a TEM photograph showing a state in which La ₂ O ₃ and CoO are continuously analyzed for an arbitrary particle 3 in the order of grain boundary → inside of the particle → grain boundary.

FIG. 15 is a graph showing the results of continuous analysis of La ₂ O ₃ and CoO for an arbitrary particle 3 in the order of grain boundary → inside of the particle → grain boundary.

FIG. 16 is a TEM photograph of a sintered body obtained in Example 2 with a firing atmosphere of O ₂ : 1%.

FIG. 17 is a TEM photograph of a sintered body obtained in Example 2 in a firing atmosphere of O ₂ : 20%.

FIG. 18 is a second drawing substitute photograph taken by TEM of the structure of the a-plane of the sintered magnet sample 1 of the comparative example.

FIG. 19 is a second drawing-substitute photograph taken by TEM of the structure of the a-plane of the sintered magnet sample 1 of the comparative example.

FIG. 20 is a diagram showing a component analysis result at a grain boundary portion by EDS of a sintered magnet sample 1 of a comparative example.

FIG. 21 is a diagram showing the results of component analysis inside crystal grains by EDS of a sintered magnet sample 1 of a comparative example.

FIG. 22 is a diagram showing a result of component analysis of a sintered magnet sample 1 of a comparative example at a triple junction by EDS.

FIG. 23 is a TEM photograph of the sample obtained in Comparative Example 2.

FIG. 24 is a TEM photograph of the sample obtained in Comparative Example 2.

FIG. 25 is a conceptual diagram showing a state of crystal grains and stacking faults.

[Description of Signs] 1 Crystal particle 2 Stacking fault

Claims (3)

[Claims] 1. At least one element selected from Sr, Ba and Ca is A, one or more of La, Pr, Nd and Ce is R, and any of Co, Ni and Zn Or one or more of them is M, and contains A, R, Fe and M, and the total composition ratio of each of the metal elements of A, R, Fe and M is as follows: 1 to 13 atomic%, R: 0.05 to 10 atomic%, Fe: 80 to 95 atomic%, M: 0.1 to 5 atomic%, and the content of R near the crystal grain center is 3 wt% or less. , A hexagonal ferrite magnet containing 4 wt% or more in the vicinity of the grain boundaries. 2. The hexagonal ferrite magnet according to claim 1, wherein when the content of the element M near the center of the crystal grain is 1 wt% or less, the content of the element M is more than 1 wt% near the crystal grain boundary. 3. The hexagonal ferrite magnet according to claim 1, which is a magnetoplumbite ferrite.