FERRITE SINTERED MAGNET, MOTOR AND GENERATOR

Abstract

Ferrite sintered magnet, comprising: a main phase formed by ferrite with a hexagonal crystal structure of the magnetoplumbite type, wherein the main phase contains Fe and Co, and a heterophase which is a crystalline phase different from the main phase and contains a first minor phase, wherein the first minor phase contains La, Ca, Si, B and Fe, and in the first minor phase an atomic ratio of Fe is lower than that in the main phase, wherein the ferrite sintered magnet contains CaB2O4, wherein the first minor phase contains CaB2O4, and wherein the area ratio of CaB2O4 in the first minor phase on the total cross-sectional area of ​​the ferrite sintered magnet is 1.5% to 6.3%.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a ferrite sintered magnet, a motor and a generator. BACKGROUND

[0002] Ba ferrite, Sr ferrite, and Ca ferrite with a hexagonal crystal structure are known as a magnetic material used in a ferrite sintered magnet. A magnetoplumbite type (M type), a W type, and the like are known as the crystal structure of such ferrite. Of these, the magnetoplumbite type (M type) ferrite is mainly used as a magnetic material for a motor or the like. The M-type ferrite is generally represented by a general formula AFe 12 O 19 shown.

[0003] Generally, residual magnetic flux density (Br) and coercive force (HcJ) are used as indexes of magnetic properties of ferrite sintered magnets. In the related art, adding various elements other than the elements constituting ferrite is considered from the perspective of improving Br and HcJ. For example, International Publication WO 2012 / 090935 A1 considers that by adding SiO2 and CaCO3, a grain boundary phase (a second phase) and a third phase are generated in addition to a ferrite phase having a hexagonal M-type magnetoplumbite structure, thus improving magnetic performance. Publication US 2012 / 0211 910 A1 relates to a rotating machine, a bonded magnet, a magnetic roller, and a method for producing a sintered ferrite magnet. Publication DE 197 40 353 A1 relates to a compact magnetic glass-ceramic molded body with a high fill factor of magnetic particles and a method for producing the same. SUMMARY

[0004] A motor, a generator, and the like, which are major applications of ferrite sintered magnets, require downsizing in each of the technical fields. For this reason, an internal structure is complex, and a magnet's installation space is becoming smaller. Therefore, reducing a thickness is being considered to reduce the installation space. However, in a case where the thickness decreases, there is a concern that the ferrite sintered magnet will be demagnetized due to a diamagnetic field.

[0005] Therefore, according to one aspect of the present disclosure, a ferrite sintered magnet having a sufficiently high coercive field strength is provided. According to another aspect of the present disclosure, a motor or a generator comprising the ferrite sintered magnet having a sufficiently high coercive field strength is provided.

[0006] According to one aspect of the present disclosure, there is provided a ferrite sintered magnet comprising a main phase formed of ferrite having a hexagonal magnetoplumbite-type crystal structure, wherein the ferrite sintered magnet contains CaB2O4.

[0007] The ferrite sintered magnet described above has a sufficiently high coercive force. A mechanism for improving the coercive force is unclear, but the following factors are conjectured. The ferrite sintered magnet described above contains CaB2O4. Here, CaB2O4 is not a magnetic body, and a melting point (1128°C) of CaB2O4 is close to a firing temperature of the ferrite sintered magnet. For this reason, wettability during liquid-phase sintering or the like is improved, and the dispersibility of each element in the ferrite sintered magnet is improved. Accordingly, for example, it is considered that Fe is easily substituted with Co at a B site of the hexagonal magnetoplumbite-type ferrite, which is the main phase. It is conjectured that the coercive force of the ferrite sintered magnet can be further improved according to such a mechanism. However, the mechanism for improving the coercive force is not limited to this.

[0008] The CaB2O4 described above can be contained in a heterophase, which is a crystalline phase different from the main phase. Furthermore, the area fraction of CaB2O4 in the total cross-sectional area of ​​a sintered magnet can be 0.05% to 2%.

[0009] The melting point of the heterophase tends to be lower than that of the bulk phase. Therefore, the heterophase is considered to contain CaB2O4, and thus, it is possible to further improve wettability during liquid-phase sintering. Furthermore, CaB2O4 is not a magnetic body, and therefore, in a case where the area fraction of CaB2O4 is less than or equal to 2%, it is possible to further enhance the magnetic properties.

[0010] In the ferrite sintered magnet described above, when an atomic ratio of Co to the total of Fe and Co in the main phase is set to a ratio (A) and an atomic ratio of Co to the total of Fe and Co in the entire magnet is set to a ratio (B), a ratio of the ratio (A) to the ratio (B) can be greater than 1.2. Accordingly, the ratio of Co in the main phase can be sufficiently higher than the ratio of Co in the entire sintered body. Therefore, the coercive force of the ferrite sintered magnet can be further increased.

[0011] The above-described ratio (B) may be less than or equal to 3.5%. In the ferrite sintered magnet of the present disclosure, Co is sufficiently incorporated into the main phase, and therefore, a sufficiently high coercive force can be maintained even in a case where the Co content in the ferrite sintered magnet is low.

[0012] The temperature coefficient of the coercive force of the ferrite sintered magnet can be -0.06 to 0 [% / °C]. Accordingly, irreversible demagnetization due to low temperature is suppressed, and the change in coercive force with temperature decreases, thus enabling the ferrite sintered magnet to exhibit high performance over a wide temperature range.

[0013] According to another aspect of the present disclosure, a motor comprising the above-described ferrite sintered magnet is provided. According to yet another aspect of the present disclosure, a generator comprising the above-described ferrite sintered magnet is provided. The above-described ferrite sintered magnet has a high coercive force. Such a ferrite sintered magnet can be mounted on the motor, the generator, and the like by reducing the thickness. Therefore, it is possible to contribute to the downsizing of the motor, the generator, or the like.

[0014] According to one aspect of the present disclosure, it is possible to provide a ferrite sintered magnet with a sufficiently high coercive field strength. According to another aspect of the present disclosure, it is possible to provide a motor or a generator comprising the ferrite sintered magnet with a sufficiently high coercive field strength. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view schematically illustrating an embodiment of a ferrite sintered magnet. Fig. 2 is a diagram schematically illustrating a microstructure on a cross-sectional surface of the ferrite sintered magnet. Fig. 3 is a schematic cross-sectional view illustrating an embodiment of a motor. Fig. 4 is a cross-sectional view along the line IV-IV of the engine of Fig. 3. Fig. 5 is a photograph showing an observed image (magnification: 2000 times) of a cross-sectional surface of a ferrite sintered magnet of Production Example 5 according to an electron microscope. Fig.6 is a photograph when a second sub-phase surrounded by a main phase and its near region are observed with a high-resolution transmission electron microscope (HRTEM) on the cross-sectional surface of the sintered ferrite of Preparation Example 6. Fig. 7 is a Fourier-transformed image obtained by performing two-dimensional Fourier transform on a part of an image of the second sub-phase on the cross-sectional surface of the sintered ferrite of Production Example 6. Fig. 8 is a model diagram corresponding to an HRTEM image of Fig. 6 corresponds. Fig. 9 is a photograph of an observed image (magnification: 10,000 times) when the cross-sectional area of ​​the ferrite sintered magnet of Production Example 6 is observed with a scanning transmission electron microscope. DETAILED DESCRIPTION

[0015] Several embodiments will be described below with reference to the drawings according to a case. In the description, the same reference numerals are used for the same elements or for elements having the same function, and their repeated description will be omitted as appropriate. Furthermore, the dimensional ratio of each part is not limited to the illustrated ratio.

[0016] Fig. 1 is a perspective view schematically illustrating a ferrite sintered magnet according to an embodiment. An anisotropic ferrite sintered magnet 10 has a curved shape such that an end surface is in the shape of a circular arc, and generally has a shape referred to as an arc segment shape, C-shape, roof tile shape, or arc shape. The ferrite sintered magnet 10 is preferably used, for example, as a magnet for a motor or a generator. However, the shape of the ferrite sintered magnet is not limited to the shape of Fig. 1 limited.

[0017] The ferrite sintered magnet includes a main phase formed from a ferrite phase with a magnetoplumbite-type crystal structure. In the present disclosure, "main phase" refers to a crystalline phase most abundantly contained in the ferrite sintered magnet. The crystalline phase most abundantly contained in the ferrite sintered magnet is the ferrite phase. An area ratio of the main phase on a cross-sectional area of ​​the ferrite sintered magnet may, for example, be greater than or equal to 80% or range from 85% to 98%.

[0018] The ferrite sintered magnet contains CaB2O4. A melting point (1128°C) of CaB2O4 is close to a firing temperature of the ferrite sintered magnet, thus having an effect of improving wettability during liquid-phase sintering or the like. Therefore, the dispersibility of each element in the ferrite sintered magnet is improved by containing CaB2O4, and Fe in the main phase is easily substituted with Co. Therefore, even in a case where the Co content in the entire ferrite sintered magnet is low, it is possible to effectively incorporate Co into the main phase. Accordingly, even in a case where the amount of Co used is small, it is possible to sufficiently increase the coercive force of the ferrite sintered magnet.

[0019] CaB2O4 may be contained in the heterophase. It is assumed that CaB2O4 is contained in the heterophase, and thus, it is possible to further improve wettability during liquid-phase sintering. The area ratio of CaB2O4 to the total cross-sectional area on the cross-sectional area of ​​the ferrite sintered magnet may be less than or equal to 2% from the perspective of minimizing the non-magnetic content. Furthermore, the area ratio may be greater than or equal to 0.05% or greater than or equal to 0.1% from the perspective of sufficiently increasing the Co content in the main phase.

[0020] The CaB2O4 contained in the ferrite sintered magnet can be determined by observing the cross-sectional area of ​​the ferrite sintered magnet with a high-resolution transmission electron microscope (HRTEM), performing a two-dimensional Fourier transform on the observed image, and obtaining the surface distance and surface angle of the crystal surfaces. The area of ​​CaB2O4 can be obtained based on the determination result and the observed image.

[0021] When an atomic ratio [Co / (Fe + Co)] of Co to the total of Fe and Co in the entire ferrite sintered magnet is set to a ratio (B), the ratio (B) may be, for example, less than or equal to 5% or less than or equal to 3.5%. Further, when an atomic ratio [Co / (Fe + Co)] of Co to the total of Fe and Co in the main phase is set to a ratio (A), the ratio (A) may be, for example, 3% to 5%. A ratio of the ratio (A) to the ratio (B) may be greater than 1.2, greater than or equal to 1.3, or greater than or equal to 1.4. Thus, the ratio of the ratio (A) to the ratio (B) increases, and therefore, even in a case where the content of Co in the entire ferrite sintered magnet is reduced, the ferrite sintered magnet with a sufficiently high coercive force can be obtained.The ferrite sintered magnet of this embodiment contains CaB2O4, and thus it is possible to increase the ratio of ratio (A) to ratio (B).

[0022] The ferrite sintered magnet contains a crystalline phase (heterophase) different from the main phase. The heterophase contained in the ferrite sintered magnet may be one type or two or more types. If multiple types of heterophases are contained, all of the heterophases may contain CaB2O4, or one type of heterophase may contain CaB2O4. CaB2O4 tends to be contained in a heterophase in which the atomic ratio of B is higher than the atomic ratio of Fe. Hereinafter, the heterophase containing CaB2O4 is referred to as a first minor phase.

[0023] The first minor phase of the ferrite sintered magnet contains La, Ca, Si, B, and Fe, and the atomic ratio of Fe in the first minor phase is lower than that in the main phase. The first minor phase of the ferrite sintered magnet contains La, Ca, Si, B, and Fe. The atomic ratio of Ca in the first minor phase is higher than the atomic ratio of La, the atomic ratio of B is higher than the atomic ratio of Fe, and the atomic ratio of Fe is lower than that in the main phase. It is possible to obtain the area fraction of CaB2O4 in the first minor phase from the area determined as CaB2O4 and the area of ​​the first minor phase on the cross-sectional area of ​​the ferrite sintered magnet. From the perspective of sufficiently increasing the Co content in the main phase while keeping the proportion of the non-magnetic body low, the area fraction of CaB2O4 in the first minor phase on the entire cross-sectional area of ​​the ferrite sintered magnet is 1.5% to 6.3%.It is also described that from the point of view of sufficiently increasing the Co content in the main phase while keeping the proportion of the non-magnetic body low, the area fraction of CaB2O4 in the first minor phase on the entire cross-sectional area of ​​the ferrite sintered magnet can be, for example, less than or equal to 11%.

[0024] The area ratio of CaB2O4 to the total cross-sectional area of ​​the ferrite sintered magnet can be calculated from the area ratio of the first minor phase to the total cross-sectional area of ​​the ferrite sintered magnet and the area ratio of CaB2O4 to the first minor phase. The area ratio of CaB2O4 to the total cross-sectional area of ​​the ferrite sintered magnet may be less than or equal to 2% or less than or equal to 1% from the perspective of obtaining a higher coercive force. The area ratio of CaB2O4 to the total cross-sectional area of ​​the ferrite sintered magnet may be greater than or equal to 0.1% or greater than or equal to 0.2% from the perspective of further improving the dispersibility of each of the elements.

[0025] The ferrite sintered magnet may contain a heterophase that does not contain CaB2O4. Hereinafter, the heterophase that does not contain CaB2O4 is referred to as a second minor phase. Examples of the second minor phase include a heterophase in which an atomic ratio of B is lower than an atomic ratio of Fe. In addition, the second minor phase contains, for example, La, Ca, and Fe. In the second minor phase, an atomic ratio of La is higher than that in the main phase, and the atomic ratio of La is higher than an atomic ratio of Ca.

[0026] The area fraction of each of the main phase and the heterophase (the first sub-phase and the second sub-phase) in the ferrite sintered magnet can be obtained by observing the cross-sectional area of ​​the ferrite sintered magnet with a scanning transmission electron microscope / energy dispersive X-ray analysis (RTEM / EDA) and performing image processing. The composition of each of the main phase and the second sub-phase can be measured using RTEM / EDA. The composition of the first sub-phase can be measured using a scanning transmission electron microscope / electron energy loss spectroscopy (RTEM / EELS).

[0027] Fig.2 is a diagram schematically illustrating a microstructure by magnifying a portion of the cross-sectional area of ​​the ferrite sintered magnet. The ferrite sintered magnet 10 includes a main phase 12 and a first sub-phase 13 and a second sub-phase 14 included in the particles of the main phase 12. The main phase 12 is a ferrite phase with a hexagonal magnetoplumbite-type crystal structure. In contrast, the first sub-phase 13 and the second sub-phase 14 are heterophases with a crystal structure different from that of the main phase 12. The first sub-phase 13 contains a CaB2O4 compound. The second sub-phase 14 may not contain the CaB2O4 compound, but may contain, for example, orthoferrite. The orthoferrite is a compound (RFeO3) with a perovskite structure containing a rare earth element (R) and an iron element (Fe).

[0028] The first subsidiary phase 13 contains La, Ca, Si, B, and Fe. In the first subsidiary phase 13, the atomic ratio of Ca is higher than the atomic ratio of La, the atomic ratio of B is higher than the atomic ratio of Fe, and the atomic ratio of Fe is lower than that in the main phase. In the first subsidiary phase 13, for example, when the total of La, Ca, Si, B, and Fe is set to 100 atomic%, the ratio of La is 1 atomic% to 25 atomic%, the ratio of Ca is 30 atomic% to 70 atomic%, the ratio of Si is less than or equal to 50 atomic%, the ratio of B is 8 atomic% to 60 atomic%, and the ratio of Fe is less than or equal to 20 atomic%. From the perspective of increasing the Co content in the main phase 12, the first subsidiary phase 13 may not contain Co. In the first sub-phase 13, when the total of La, Ca, Si, B, Fe and Co is fixed at 100 atomic%, the ratio of Co can be less than or equal to 0.5 atomic%.Accordingly, it is possible to increase the atomic ratio of Co in the main phase.

[0029] In the first sub-phase 13, when the total of La, Ca, Si, B, and Fe is set to 100 atomic%, the total of the atomic ratio of Ca and the atomic ratio of La is, for example, 31 atomic% to 95 atomic%. The first sub-phase 13 may contain an element other than those described above. At least ten first sub-phases 13 are formed on the cross-sectional surface of the ferrite sintered magnet, as shown in Fig. 2, arbitrarily extracted, and the composition of the first sub-phase 13 can be obtained as the mean value of each analysis result.

[0030] The area ratio of the first sub-phase 13 in the ferrite sintered magnet is greater than or equal to 1%. From the perspective of sufficiently increasing a coercive force and a residual magnetic flux density, the area ratio of the first sub-phase 13 may be, for example, 3% to 20%, or it may be 7% to 15%. The area ratio of the first sub-phase 13 can be adjusted by changing a mixing ratio of a raw material compound containing boron (B) at the time of mixing the raw materials.

[0031] For example, in the second minor phase 14, when the total of La, Ca, and Fe is set to 100 atomic%, the ratio of La can be 10 atomic% to 60 atomic%, the ratio of Ca can be 0 atomic% to 19 atomic%, and the ratio of Fe can be 10 atomic% to 60 atomic%. The second minor phase 14 may contain an element other than La, Ca, and Fe. Examples of such an element include Si. When the total of La, Ca, Fe, and Si is set to 100 atomic%, the ratio of Si can be 0 atomic% to 19 atomic%, for example. At least ten second minor phases 14 are formed on the cross-sectional area of ​​the ferrite sintered magnet as shown in Fig. 2, arbitrarily extracted, and the composition of the second minor phase can be obtained as the mean value of each analysis result.

[0032] The area ratio of the second sub-phase 14 on the cross-sectional area of ​​the ferrite sintered magnet may be less than or equal to 5%, 0.5% to 4%, or 1% to 3%. In a case where the area ratio of the second sub-phase increases excessively, there is a case where a sufficiently excellent coercive force is impaired. On the other hand, in a case where the area ratio of the second sub-phase decreases excessively, there is also a case where a sufficiently excellent coercive force is impaired. The area ratio of the second sub-phase can be adjusted, for example, by changing a mixing ratio of a raw material compound containing La at the time of mixing the raw materials.

[0033] When the overall composition of the ferrite sintered magnet containing the main phase and the heterophase is represented by the general formula (I) described below, the expressions (1), (2), and (3) described below can be satisfied. In the general formula (I), x, y, and m represent a molar ratio. In the general formula (I), R represents La or at least one kind of element selected from rare earth elements including La and Y, and A represents Ca or Ca and an element consisting of one or both of Sr and Ba. R 1-x A x Fe m-y Co y (I) 0.2≤x≤0.8 0.1≤y≤0.65 3≤m<14

[0034] In the general formula (I), x may be less than or equal to 0.7 or less than or equal to 0.6 from the viewpoint of further increasing the coercive force. From the same viewpoint, x may be greater than or equal to 0.25 or greater than or equal to 0.3. In addition, x may be less than 0.55 or less than or equal to 0.5 from the viewpoint of suppressing irreversible demagnetization due to low temperature. In the general formula (I), y may be less than or equal to 0.6 or less than or equal to 0.5 from the viewpoint of further increasing the magnetic properties.

[0035] From the same point of view, y in the general formula (I) may be greater than or equal to 0.15 or greater than or equal to 0.2. From the viewpoint of further increasing the coercive force, m in the general formula (I) may be greater than or equal to 4 or greater than or equal to 5. From the same point of view, m in the general formula (I) may be less than or equal to 13 or less than or equal to 12. In the general formula (I), m is preferably greater than or equal to 7.5, and more preferably greater than or equal to 8, from the viewpoint of suppressing irreversible demagnetization by low temperature while further increasing the coercive force. In the general formula (I), m may be 8 to 13 or 8 to 12 from the viewpoint of suppressing irreversible demagnetization by low temperature while further increasing the coercive force.

[0036] Preferably, the ferrite sintered magnet described above satisfies expressions (4) and (5). 0.2≤x<0.55 7.5 <m<14

[0037] The above-described expressions (4) and (5) are satisfied, and thus it is possible to further suppress the irreversible demagnetization by low temperature and obtain the ferrite sintered magnet with more excellent magnetic properties at a low temperature.

[0038] From the viewpoint of enhancing magnetic properties, A in General Formula (I) preferably comprises Ca or Ca and Sr as a main component. A may comprise only Ca or only Ca and Sr.

[0039] In several embodiments, General Formula (I) may be represented by General Formula (II). In General Formula (I), x is identical to x1 + x2 in General Formula (II). Therefore, the contents related to the range of x also apply to the range of x1 + x2. In General Formula (II), R represents at least one kind of element selected from La or a rare earth element including La and Y, and E represents at least one kind of element selected from the group consisting of Sr and Ba. R 1-x1-x2 Ca x1 E x2 Fe m-y Co y (II)

[0040] When the composition of the ferrite sintered magnet is represented by General Formula (II), Expressions (6), (7), (8), and (9) described below are satisfied. In General Formula (II), x1, x2, y, and m represent a molar ratio. Therefore, when the composition of the ferrite sintered magnet is represented by General Formula (I), Expression (1) can be satisfied, and when the composition of the ferrite sintered magnet is represented by General Formula (II), Expressions (6), (7), (8), and (9) can be satisfied. 0.1≤x1≤0.65 0≤x2<0.5 0.1≤y≤0.65 3≤m<14

[0041] In General Formula (II), x1 may be less than or equal to 0.6 or less than or equal to 0.5 from the viewpoint of further increasing the coercive force. From the same viewpoint, x1 may be greater than or equal to 0.2 or greater than or equal to 0.3. In General Formula (II), x2 may be less than or equal to 0.4 or less than or equal to 0.3 from the viewpoint of further increasing the coercive force. In General Formula (II), x2 may be 0.

[0042] In the general formula (II), y may be less than or equal to 0.6 or less than or equal to 0.5 from the viewpoint of further enhancing the magnetic properties. From the same viewpoint, y in the general formula (II) may be greater than or equal to 0.15 or greater than or equal to 0.2. From the viewpoint of further enhancing the coercive force, m in the general formula (II) may be greater than or equal to 4 or greater than or equal to 5. From the same viewpoint, m in the general formula (II) may be less than or equal to 13 or less than or equal to 12. In the general formula (II), m is preferably greater than or equal to 7.5, and more preferably greater than or equal to 8, from the viewpoint of improving the magnetic properties at a low temperature.In the general formula (II), m can be 8 to 13 or 8 to 12 from the viewpoint of suppressing irreversible demagnetization by low temperature while further increasing the coercive field strength.

[0043] Preferably, the ferrite sintered magnet described above satisfies expressions (10) and (11). 0.2≤x1+X2<0.55 7.5 <m<14

[0044] The above-described expressions (10) and (11) are satisfied, and thus it is possible to further suppress the irreversible demagnetization by low temperature and obtain the ferrite sintered magnet with more excellent magnetic properties at a low temperature.

[0045] The content ratio of each element represented by General Formula (I) and General Formula (II) can be measured by X-ray fluorescence analysis. Furthermore, the content ratio of each element represented by General Formula (I) and General Formula (II) is generally equal to the mixing ratio of each of the starting materials in a mixing step described below. The boron (B) content can be measured by inductively coupled plasma emission spectral analysis (ICP emission spectral analysis).

[0046] From the viewpoint of increasing the CaB2O4 content, the B content in the ferrite sintered magnet is, for example, 0.15 mass% to 0.6 mass% with respect to B2O3. The above-described B content may be less than or equal to 0.5 mass% or less than or equal to 0.4 mass% from the viewpoint of further increasing the magnetic properties. The above-described B content may be greater than 0.18 mass% or greater than or equal to 0.2 mass% from the viewpoint of further increasing the magnetic properties. Preferably, the above-described B content is greater than 0.2 mass% and less than or equal to 0.4 mass% from the viewpoint of sufficiently increasing the CaB2O4 content.

[0047] From the viewpoint of enhancing magnetic properties, E in General Formula (II) preferably contains Sr as a main component. E may contain only Sr.

[0048] Preferably, R in General Formula (I) and General Formula (II) comprises lanthanum (La) or lanthanum (La) and one or more types of elements selected from the group consisting of cerium (Ce), praseodymium (Pr), neodymium (Nd), and samarium (Sm). R may comprise only La.

[0049] The ferrite sintered magnet contains Si as a constituent element, which is an element not represented in the above-described general formula (I) or (II). Examples of the constituent element other than Si include Na. These constituent elements are contained, for example, in the ferrite sintered magnet as an oxide or a composite oxide thereof.

[0050] For example, the Si content in the ferrite sintered magnet may be less than or equal to 3 mass% when Si is determined in terms of SiO2. The Si content in the ferrite sintered magnet and the ferrite particles may be less than 0.3 mass% when Si is determined in terms of SiO2 from the viewpoint of further enhancing the magnetic properties. From the same viewpoint, the total content of Si and B in the ferrite sintered magnet and the ferrite particles may be 0.1 mass% to 0.8 mass% or 0.2 mass% to 0.5 mass% when Si and B are determined in terms of SiO2 and B2O3, respectively. The silicon (Si) content can be measured by inductively coupled plasma emission spectrometry (ICP emission spectrometry). The content of Na in the ferrite sintered magnet and the ferrite particles can be, for example, 0 mass% to 0.2 mass% when determining Na with respect to Na2O.

[0051] The content of Na in the ferrite sintered magnet can be, for example, less than or equal to 0.2 mass%, 0.01 mass% to 0.15 mass%, or 0.02 mass% to 0.1 mass% when determining Na with respect to Na2O.

[0052] Impurities contained in the raw material or unavoidable components arising from the production equipment may be contained in the ferrite sintered magnet in addition to the components described above. Examples of such components include titanium (Ti), chromium (Cr), manganese (Mn), molybdenum (Mo), vanadium (V), aluminum (Al), and the like. These components may be contained in the ferrite sintered magnet as an oxide or a composite oxide thereof. The content of the partial component, impurities, and unavoidable component described above can be measured by X-ray fluorescence analysis or ICP emission spectral analysis.The partial component, the impurities and the unavoidable component described above may be segregated into a grain boundary of ferritic crystal grains of the ferrite sintered magnet and they may form a heterophase different from the first minor phase and the second minor phase.

[0053] A composition range of the main phase in the ferrite sintered magnet is set such that the above-described overall composition of the ferrite sintered magnet is within the above-described range.

[0054] The average particle diameter of the crystal grains (ferrite particles) containing the main phase in the ferrite sintered magnet can be, for example, less than or equal to 5 μm, less than or equal to 4 μm, or from 0.5 μm to 3 μm. According to such an average particle diameter, it is possible to further increase the coercive force. The average particle diameter of the crystal grains of the ferrite sintered magnet can be obtained using the observed image of the cross-sectional area of ​​the ferrite sintered magnet according to TEM or SEM. Specifically, image processing is performed on the observed SEM or TEM image containing hundreds of crystal grains, and thus a particle diameter distribution is measured. The number-average value of the particle diameters of the crystal grains is calculated from the measured number-average particle diameter distribution.It is determined that the mean value measured as described above is the mean particle diameter of the crystal grains.

[0055] For example, the coercive field strength of the ferrite sintered magnet at 20°C is preferably greater than or equal to 4900 Oe (=389.93 kA / m), and more preferably greater than or equal to 5000 Oe (=397.89 kA / m). The residual magnetic flux density of the ferrite sintered magnet at 20°C is preferably greater than or equal to 3000 G (=0.3 T), and more preferably greater than or equal to 3500 G (=0.35 T). Preferably, the ferrite sintered magnet has both excellent coercive field strength (HcJ) and excellent residual magnetic flux density (Br).

[0056] For example, the coercive force of the ferrite sintered magnet at -30°C is preferably greater than or equal to 4900 Oe (=389.93 kA / m), and more preferably greater than or equal to 5000 Oe (=397.89 kA / m). A temperature coefficient of coercive force (a temperature coefficient of HcJ) in the present disclosure is calculated from the value of the coercive force at -30°C and 20°C. The temperature coefficient of HcJ calculated as described above may be -0.06 to 0 [% / °C] or -0.01 to 0 [% / °C].

[0057] There is a case where the residual magnetic flux density of the magnetized ferrite magnet decreases when the ferrite magnet is cooled to a sufficiently low temperature and then returned to the original temperature. This is called irreversible low-temperature demagnetization. This irreversible low-temperature demagnetization is a major weakness of the ferrite magnet in the related art. The ferrite sintered magnet of this embodiment has a sufficiently high coercive force and is thus capable of suppressing irreversible low-temperature demagnetization. Furthermore, the temperature coefficient of HcJ is set to be less than or equal to 0 [% / °C], and therefore, it is possible to suppress irreversible low-temperature demagnetization.

[0058] The ferrite sintered magnet can be used, for example, in a motor or a generator. More specifically, the ferrite sintered magnet can be used as a magnet in a motor for a passenger car, such as a fuel pump motor, an automatic window motor, an anti-lock braking system (ABS) motor, a fan motor, a windshield wiper motor, a power steering motor, an active suspension motor, a starter motor, a door lock motor, and a power mirror motor.In addition, the ferrite sintered magnet can be used as a magnet in a motor for office automation and audio-visual (OA / AV) equipment, such as a motor for a floppy disk drive (FDD) spindle, a motor for a video tape recorder (VTR) capstan, a motor for a VTR rotary head, a motor for a VTR tape reel, a motor for a VTR loading system, a motor for a VTR camera capstan, a motor for a VTR camera rotary head, a motor for a VTR camera zoom, a motor for a VTR camera focusing system, a motor for a capstan of a radio cassette recorder or the like, a motor for a CD / DVD / MD spindle, a motor for a CD / DVD / MD loading system, and a motor for a CD / DVD pickup unit.Furthermore, the ferrite sintered magnet can be used as a magnet in a motor for household electrical appliances, such as an air conditioner compressor motor, a freezer compressor motor, a power tool driving motor, a dryer fan motor, a shaver driving motor, and an electric toothbrush motor. Furthermore, the ferrite sintered magnet can be used as a magnet in a motor for FA devices, such as a robot shaft motor, a joint driving motor, a robot main drive motor, a machine tool table driving motor, and a machine tool belt driving motor.

[0059] Fig.3 is a schematic cross-sectional view illustrating one embodiment of the motor. A motor 30 of this embodiment includes the ferrite sintered magnet 10. The motor 30 is a single-brush DC motor and includes a bottomed tubular casing 31 (a stator) and a rotatable rotor 32 concentrically provided on the inner peripheral side of the casing 31. The rotor 32 includes a rotor shaft 36 and a rotor core 37 fixed on the rotor shaft 36. An elbow 33 is fixed to the opening portion of the casing 31, and the rotor core is housed in a space defined by the casing 31 and the elbow 33. The rotor shaft 36 is rotatably supported by bearings 34 and 35 provided in the central portion of the casing 31 and the central portion of the elbow 33, respectively, so as to oppose each other.Two C-type ferrite sintered magnets 10 are mounted on the inner peripheral surface of the tubular portion of the housing 31 so as to face each other.

[0060] Fig. 4 is a cross-sectional view along the line IV-IV of the engine 30 of Fig. 3. The ferrite sintered magnet 10 as the magnet for a motor is adhered to the inner peripheral surface of the housing 31 with an adhesive, using the outer peripheral surface as the adhesive surface. It is possible to reduce the thickness of the ferrite sintered magnet 10, and thus, it is possible to sufficiently narrow a gap between the housing 31 and the rotor 32. Therefore, the motor 30 can be downsized while maintaining performance.

[0061] Next, an example of a method for manufacturing the ferrite sintered magnet will be described. The manufacturing method described below includes a mixing step, a calcination step, a pulverization step, a molding step, and a firing step. The details of each of the steps are described below.

[0062] In the mixing step, a plurality of raw materials are mixed to obtain a raw material composition. Examples of the raw material include one or two or more types of compounds (raw material compounds) containing at least one selected from the group consisting of the elements represented by General Formula (I) or (II) and boron as an elemental component. Preferably, the raw material compound is in the form of, for example, a powder. Examples of the raw material compound include an oxide or a compound that becomes an oxide by firing (a carbonate, a hydroxide, a nitrate, and the like). For example, SrCO3, La(OH)3, Fe2O3, BaCO3, CaCO3, Co3O4, B2O3, and the like can be exemplified.For example, the average particle diameter of the powder of the starting material compound is approximately 0.1 µm to 2.0 µm from the viewpoint of ease of mixing.

[0063] Compared with other raw materials, a boron compound such as boron oxide tends to dissolve easily in water and disperse easily when heated. Therefore, the mixing ratio of the boron compound in the raw material composition in the mixing step must be greater than the boron content ratio in the ferrite sintered magnet. For example, the ratio of the mixing ratio to the content ratio is 120% to 300%.

[0064] In the mixing step, a raw material compound that is a constituent component (a simple element substance, an oxide, or the like) may be mixed as needed. The raw material composition can be obtained, for example, by weighing each of the raw materials so that a desired ferrite sintered magnet is obtained, mixing the raw materials, and then performing a mixing and pulverizing treatment for approximately 0.1 to 20 hours using a wet attritor, a ball mill, or the like.

[0065] In the calcination step, the raw material composition obtained in the mixing step is calcined. The calcination can be carried out, for example, in an oxidizing atmosphere such as air. A calcination temperature can be, for example, 1100°C to 1400°C or 1100°C to 1300°C. A calcination time can be, for example, 1 second to 10 hours or 1 second to 3 hours. A proportion of the ferrite phase (an M phase) in a calcined powder (the ferrite particles) obtained by calcination can be, for example, greater than or equal to 70 volume% or greater than or equal to 75 volume%. The proportion of the ferrite phase can be obtained like the proportion of the main phase of ferrite in the ferrite sintered magnet.

[0066] In the pulverization step, the calcined powder, which is in the form of granules or agglomerates resulting from the calcination step, is pulverized. Ferrite particles are thus obtained. For example, the pulverization step can be carried out by dividing it into two steps: pulverizing the calcined powder into a coarse powder (a coarse pulverization step) and then finely pulverizing the coarse powder (a fine pulverization step).

[0067] Coarse pulverization can be carried out, for example, using a vibrating mill or the like, until the average particle diameter of the calcined powder is 0.5 µm to 5.0 µm. In fine pulverization, the coarse powder obtained by coarse pulverization is further pulverized using a wet attritor, a ball mill, a jet mill, or the like. In fine pulverization, pulverization is carried out such that the average particle diameter of the obtained fine powder (the ferrite particles) is, for example, approximately 0.08 µm to 2.0 µm. A specific surface area of ​​the fine powder (obtained, for example, by a BET method) is, for example, approximately 7 m 2 / g up to 12 m 2 / g. The preferred pulverization time varies depending on the pulverization method. For example, the pulverization time for a wet attritor is 30 minutes to 10 hours, and for wet pulverization with a ball mill, the pulverization time is 10 hours to 50 hours. The specific surface area of ​​the ferrite particles can be measured using a commercially available BET specific surface area meter (product name: HM Model-1210, manufactured by MOUNTECH Co. Ltd. (TM).

[0068] In the fine pulverization step, in order to increase a degree of magnetic orientation of a sintered body obtained after firing, for example, a polyhydric alcohol represented by a general formula C n (OH) n H n+2represented by . In the general formula, n can be, for example, 4 to 100 or 4 to 30. Examples of the polyhydric alcohol include sorbitol. Furthermore, two or more types of polyhydric alcohols can be used together. Further, in addition to the polyhydric alcohol, other known dispersants can be used together.

[0069] In a case where the polyhydric alcohol is added, the added amount may be, for example, 0.05 mass% to 5.0 mass% or 0.1 mass% to 3.0 mass% based on a matter to be added (e.g., the coarse powder). Furthermore, the polyhydric alcohol added in the fine pulverization step is removed by thermolysis in the firing step described below.

[0070] In the coarse pulverization step and / or the fine pulverization step, a powder such as SiO2 is added as the component. By adding such a component, it is possible to improve sintering properties and magnetic properties. However, from the viewpoint of sufficiently enhancing the magnetic properties, it is preferable that the added amount of SiO2 is not too large.

[0071] In the molding step, the ferrite particles obtained in the pulverization step are molded in a magnetic field to obtain a molded article. Molding can also be performed using other dry or wet molding methods. From the viewpoint of increasing the degree of magnetic alignment, molding is preferably performed by wet molding.

[0072] In a case where molding is performed by wet molding, for example, the above-described fine pulverization step is performed in a wet process, thus obtaining a slurry, and then the slurry is thickened to a predetermined concentration, thus obtaining a slurry for wet molding. Molding can be performed using the slurry for wet molding. The slurry is thickened by centrifugation, filter press, or the like. The content of the ferrite particles in the slurry for wet molding is, for example, 30 mass% to 80 mass%. In the slurry, for example, water exemplifies a dispersion medium for dispersing the ferrite particles. A surfactant such as gluconic acid, gluconate, and sorbitol may be added to the slurry. A non-aqueous solvent may be used as the dispersion medium.An organic solvent such as toluene or xylene can be used as the non-aqueous solvent. In this case, a surfactant such as oleic acid can be added. Furthermore, the slurry can be prepared for wet molding by adding the dispersion medium or the like to the ferrite particles in a dry state after they have been finely pulverized.

[0073] Next, in wet forming, the forming is carried out with respect to the slurry for wet forming in the magnetic field. In this case, a forming pressure is, for example, 9.8 MPa to 49 MPa (0.1 ton / cm 2 up to 0.5 ton / cm 2 ). The magnetic field to be applied is, for example, 398 kA / m to 1194 kA / m (5 kOe to 15 kOe).

[0074] In the firing step, the molded body obtained in the molding step is fired, thus obtaining the ferrite sintered magnet. The molded body can be fired in an oxidizing atmosphere such as the atmosphere. A firing temperature can be, for example, 1050°C to 1270°C or 1080°C to 1240°C. Furthermore, a firing time (a time for which the firing temperature is maintained) can be, for example, 0.5 hours to 3 hours.

[0075] In the firing step, heating may be performed at a temperature rise rate of approximately 0.5°C / minute before reaching the firing temperature, for example, from room temperature to approximately 100°C. Accordingly, it is possible to sufficiently dry the molded article before sintering. Furthermore, it is possible to sufficiently remove the surfactant added in the molding step. Furthermore, such treatment may be performed at the beginning of the firing step, or it may be performed separately before the firing step.

[0076] Thus, it is possible to manufacture the ferrite sintered magnet. However, the method for manufacturing the ferrite sintered magnet is not limited to the example described above. For example, the molding step and the firing step can be performed by the following procedure. That is, the molding step can be performed by a type of ceramic injection molding (CIM) or powder injection molding (PIM) molding method. In the CIM molding method, dried ferrite particles are first heated and kneaded together with a binder resin, thus forming a pellet. The pellet is subjected to injection molding into a mold to which a magnetic field is applied, thus obtaining a preformed body. The preformed body is subjected to debinding treatment, thus obtaining the molded body. The more detailed procedure is described below.

[0077] A finely pulverized slurry containing the ferrite particles obtained during wet pulverization is dried. The drying temperature can be, for example, 80°C to 150°C or 100°C to 120°C. The drying time can be 1 hour to 40 hours or 5 hours to 25 hours. The average particle diameter of the primary particles of a magnetic powder after drying can be, for example, 0.08 µm to 2 µm or 0.1 µm to 1 µm.

[0078] The ferrite particles, after being dried, are kneaded together with an organic component such as a binder resin, waxes, a lubricant, a plasticizer, and a sublimation compound, and formed into a pellet using a pelletizer or the like. The organic component may be contained in the molded article, for example, at 35% to 60% by volume or 40% to 55% by volume. Kneading may be performed using a kneader or the like. For example, a twin-screw or single-screw extruder is used as the pelletizer. Kneading and pelletizing may be performed while heating in accordance with a melting temperature of the organic component to be used.

[0079] A polymer compound such as a thermoplastic resin is used as the binder resin. Examples of the thermoplastic resin include polyethylene, polypropylene, an ethylene-vinyl acetate copolymer, atactic polypropylene, an acrylic polymer, polystyrene, polyacetal, and the like.

[0080] Synthetic wax such as paraffin wax, urethane wax and polyethylene glycol are used as the waxes in addition to natural wax such as carnauba wax, montan wax and beeswax.

[0081] Examples of the lubricant include fatty acid esters and the like. Examples of the plasticizer include phthalic acid esters.

[0082] The added amount of binder resin is, for example, 3% to 20% by mass based on 100% by mass of the ferrite particles. The added amount of wax is, for example, 3% to 20% by mass based on 100% by mass of the ferrite particles. The added amount of lubricant is, for example, 0.1% to 5% by mass based on 100% by mass of the ferrite particles. The added amount of plasticizer is, for example, 0.1% to 5% by mass based on 100% by mass of the binder resin.

[0083] Next, the pellet is introduced into a conventional magnetic field injection molding apparatus, and injection molding is performed with respect to a mold having a cavity of a predetermined shape. The magnetic field is applied to the mold before injection with respect to the mold. The pellet is heated and melted at, for example, 160°C to 230°C in the extruder and injected into the mold cavity by a screw. The temperature of the mold is, for example, 20°C to 80°C. The magnetic field applied to the mold can be approximately 398 kA / m to 1592 kA / m (5 kOe to 20 kOe). In this way, the preformed body is obtained using the magnetic field injection molding apparatus.

[0084] The resulting preformed body is subjected to heat treatment at a temperature of 100°C to 600°C in the atmosphere or in nitrogen, and the debinding treatment is performed, thus obtaining the molded body. In a case where a variety of organic components are used, the debinding treatment can be performed multiple times.

[0085] Next, in the firing step, the molded body subjected to the debinding treatment is fired in the atmosphere at, for example, a temperature of 1100°C to 1250°C or 1160°C to 1230°C for about 0.2 hours to 3 hours, and thus the ferrite sintered magnet is obtained.

[0086] As described above, several embodiments of the present invention have been described, but the present invention is not limited to the embodiments described above. For example, the motor is not limited to the embodiments in Fig. 3 and Fig. 4 and may be an engine with other configurations. EXAMPLES

[0087] The contents of the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. [Production of the ferrite sintered magnet] (Production examples 1 to 11)

[0088] Iron oxide (Fe2O3), calcium carbonate (CaCO3), cobalt oxide (Co3O4), and lanthanum hydroxide (La(OH)3) were prepared as the starting material. The starting materials were mixed so that the composition of the general formula (I) was as shown in Table 1. A predetermined amount of boron oxide (B2O3) was added to a mixed substance obtained as described above, and mixing and pulverization were performed for 10 minutes using a wet attritor, thus obtaining the slurry (the mixing step). In Production Examples 1 to 10, the mixing ratio of each of the starting materials was changed so that the ferrite sintered magnet having the composition shown in Table 1 was obtained.

[0089] The slurry was dried, and then calcined, in which the slurry was kept at 1300°C in the atmosphere for 2 hours, to obtain calcined powder (the calcination step). The obtained calcined powder was subjected to coarse pulverization using a small vibrating rod mill for 10 minutes, thus obtaining coarse powder. 0.2 mass% of silicon oxide (SiO2) was added to the coarse powder. Thereafter, fine pulverization was performed for 35 hours using a wet ball mill, thus obtaining the slurry containing ferrite particles (the pulverization step).

[0090] The slurry obtained after fine pulverization was adjusted so that a solid content concentration was 73% to 75%, thus obtaining a slurry for wet molding. The slurry for wet molding was molded in an applied magnetic field of 796 kA / m (10 kOe) using a magnetic field wet molding machine, thus obtaining a cylindrical molded article with a diameter of 30 mm and a thickness of 15 mm (the molding step). The obtained molded article was dried at room temperature in the atmosphere, and then firing was performed by keeping the molded article at 1180°C in the atmosphere for 1 hour (the firing step). Thus, a cylindrical ferrite sintered magnet was obtained. <zusammensetzungsanalyse>

[0091] The boron (B) and silicon (Si) contents in the ferrite sintered magnet of each of the preparation examples were measured using the following procedure. A 0.1 g sample of the ferrite sintered magnet was mixed with 1 g of sodium peroxide and 1 g of sodium carbonate, and heated and melted. The molten substance was dissolved in a solution of 40 ml of pure water and 10 ml of hydrochloric acid, and then pure water was added to obtain 100 ml of a solution. Using the solution, the boron content was determined by determining boron in terms of B2O3, and the silicon content was determined by determining silicon in terms of SiO2, according to ICP emission spectral analysis (ICP-AES). For ICP emission spectral analysis, an analyzer (instrument designation: ICPS 8100CL) manufactured by Shimadzu Corporation (TM) was used, and matrix matching was performed during the measurement.For the general formula (I) described above, x, y, and m were determined based on the mixing ratio of the starting material in the mixing step. The results are shown in Table 1. <Analyse der Nebenphase>

[0092] For the ferrite sintered magnet of each of the preparation examples, the presence or absence of the main phase and the heterophase (the first sub-phase and the second sub-phase) and each area ratio thereof were measured by TEM (product name: Titan G2, manufactured by FEI company) (TM), TEM / EDX (product name: Super-X, manufactured by FEI company) (TM), and TEM / EELS (product name: GIF Quantum ER, manufactured by Gatan, Inc.) (TM). Specifically, the ferrite sintered magnet was cut so that the cross-sectional area parallel to an alignment axis was observed, and the cross-sectional area was observed with a scanning transmission electron microscope. In the Fig. From the observed image shown in Figure 5, the main phase, which has approximately the same composition as the overall composition of the ferrite sintered magnet, and two types of heterophases, which have a different color than the main phase, were determined. Then, the first sub-phase (a black area in the observed image) and the second sub-phase (a white area in the observed image) were determined using TEM / EDX and an electron energy loss spectrometer (TEM / EELS, product name: GIF Quantum ER, manufactured by Gatan, Inc. (TM)) attached to a TEM. The observed image was subjected to image analysis, and the area ratio of the first sub-phase and the second sub-phase on the cross-sectional surface of the ferrite sintered magnet was obtained. The results are shown in Table 2. Furthermore, the Remarks column of Table 2 distinguishes between Examples and Comparative Examples. <Bestimmung der kristallinen Phase der ersten Nebenphase>

[0093] Fig. 6 is a photograph taken when the first sub-phase 13 surrounded by the main phase 12 and its near region are observed with a high-resolution transmission electron microscope (HRTEM) on the cross-sectional surface of the sintered ferrite of Preparation Example 6. As shown in Fig. As shown in Figure 6, it was confirmed that a compound 22 (a crystal) was generated in the first sub-phase 13. Therefore, a two-dimensional Fourier transform was performed on a high-resolution image of the compound 22, and a Fourier-transformed image was obtained. The Fourier-transformed image was analyzed as in an electron diffraction pattern, and a crystalline phase of the compound 22 was determined. Specifically, the surface distance of the crystal surfaces was obtained from spots indicating periodicity appearing in the Fourier-transformed image, and an angle (a surface angle) between two crystal surfaces was obtained from an angle between two spots. The crystalline phase was determined based on the surface distance and the surface angle of two crystal surfaces.The value of surface distance and surface angle affects an error corresponding to a measurement and a fluctuation corresponding to a composition, and thus the surface distance has an allowable error range of ±8% and the surface angle has an allowable error range of ±2 degrees.

[0094] The picture above right in Fig. 6 is the high-resolution image of compound 22. Fig. Figure 7 is the Fourier-transformed image obtained by performing two-dimensional Fourier transform on Compound 22. As a result of determining the crystalline phase of Compound 22 based on the surface distance and surface angle of two crystal surfaces, it was confirmed that Compound 22 was CaB2O4. The same analysis was performed on the other preparation examples, and thus the presence or absence of CaB2O4 was confirmed. <Quantitative Bestimmung von CaB2O4>

[0095] For the ferrite sintered magnet of each of the preparation examples containing CaB2O4, using an HRTEM image as described in Fig. 6, a quantitative analysis of CaB2O4 was carried out. Fig. 8 is an HRTEM image of Fig. 6 corresponding model diagram to describe an analysis method. As in Fig. 6 and Fig. As shown in Figure 8, the compound 22 (CaB2O4) is distributed in the first minor phase 13. Therefore, image analysis of the first minor phase 13 was performed, and an area ratio of the compound 22 (CaB2O4) on the first minor phase 13 was obtained. Then, the area ratio and the area ratio of the first minor phase 13 on the cross-sectional area of ​​the ferrite sintered magnet were multiplied together, and the area ratio of the compound 22 (CaB2O4) on the cross-sectional area of ​​the ferrite sintered magnet was calculated. The results are shown in Table 2. [Evaluation of the ferrite sintered magnet]<Bewertung der magnetischen Eigenschaften>

[0096] The upper and lower surfaces of the ferrite sintered magnet were machined, and then the magnetic properties were measured at 20°C and -30°C using a BH tracer with a maximum applied magnetic field of 29 kOe (=2307.75 kA / m). Accordingly, the residual magnetic flux density [Br(G)] and coercive force [HcJ(Oe)], the temperature coefficient of HcJ, and the temperature coefficient of Br were obtained at each of the temperatures. The magnetic properties at -30°C were measured using a cooling device that utilizes a refrigerator and a Peltier element, the prepared ferrite sintered magnet sample, and an edge portion of the BH tracer sample. The atmosphere was cooled to -30°C, and the temperature of the sample and the edge portion of the measurement sample were stabilized, and then the measurement was performed.Accordingly, the residual magnetic flux density [Br(G)] and coercive field strength [HcJ(Oe)] were measured at -30°C. The results are shown in Table 3 (where 1 Oe = 79.58 A / m and 1 G = 0.1 mT). Furthermore, the magnetic properties were measured at -30°C for a portion of the fabricated samples.

[0097] In Table 3, the temperature coefficient of HcJ and the temperature coefficient of Br were obtained according to the following expressions. Temperature coefficient of HcJ(% / °C)=[HcJ(20°C)−HcJ(−30°C)] / 50(°C) / HcJ(20°C)×100 Temperature coefficient of Br(% / °C)=[Br(20°C)−Br(−30°C)] / 50(°C) / Br(20°C)×100

[0098] In the expressions described above, HcJ (20°C) and HcJ (-30°C) for HcJ(Oe) at 20°C and -30°C, respectively. Br (20°C) and Br (-30°C) represent Br(G) at 20°C and -30°C, respectively. [Table 1] Manufacturing example composition Fe Co R (La) A (Ca) B2O3 SiO2 my y 1 - x x Mass-% Mass-% Manufacturing example 1 9,3 0,28 0,56 0,44 0,02 0,2 Manufacturing example 2 9,4 0,28 0,57 0,43 0,05 0,2 Manufacturing example 3 9,5 0,30 0,57 0,43 0,11 0,2 Manufacturing example 4 9,5 0,30 0,57 0,43 0,14 0,2 Manufacturing example 5 9,5 0,30 0,55 0,45 0,21 0,2 Manufacturing example 6 9,5 0,29 0,58 0,42 0,22 0,2 Production example 7 9,5 0,30 0,58 0,42 0,34 0,2 Manufacturing example 8 9,5 0,30 0,58 0,42 0,42 0,2 Manufacturing example 9 9,5 0,30 0,58 0,42 0,64 0,2 Manufacturing example 10 7,2 0,30 0,60 0,40 0,04 0,2 Production example 11 7,2 0,30 0,60 0,40 0,22 0,2 [Table 2] Manufacturing example Area share of the first secondary phase (%) Area share of the second secondary phase (%) Area fraction of CaB2O4 in the first sub-phase (%) Area fraction 1 of CaB2O4 in sintered magnets (%) Remarks Manufacturing example 1 unavailable 3,6 unavailable unavailable Comparison example Manufacturing example 2 unavailable 3,5 unavailable unavailable Comparison example Manufacturing example 3 unavailable 3,2 unavailable unavailable Comparison example Manufacturing example 4 0,8 3,0 unavailable unavailable Comparison example Manufacturing example 5 9,9 2,3 4,2 0,42 Example Manufacturing example 6 10,5 2,0 5,6 0,59 Example Manufacturing example 7 16,4 1,6 10,1 1,66 Example Manufacturing example 8 3,1 2,0 1,5 0,05 Example Manufacturing example 9 unavailable 2,7 unavailable unavailable Comparison example Manufacturing example not 4,8 not not Comparison example game 10 available available available game Manufacturing example 11 11,7 2,5 6,3 0,74 Example [Table 3] Manufacturing example Br (G) 20°C HcJ (Oe) 20°C Br (G) -30° C HcJ (Oe) -30° C Temperature coefficient of HcJ (% / °C) Temperature coefficient of Br (% / °C) Manufacturing example 1 4222 3630 4616 3503 0,070 -0,187 Manufacturing example 2 4247 3658 - - - - Manufacturing example 3 4302 5045 4702 5010 0,014 -0,186 Manufacturing example 4 4320 5483 4713 5472 0,004 -0,182 Manufacturing Example 5 4311 6707 4697 6791 -0,025 -0,179 Manufacturing Example 6 4313 6764 4697 6872 -0,032 -0,178 Manufacturing Example 7 4148 5921 - - - - Manufacturing Example 8 3829 5238 - - - - Manufacturing Example 9 3481 4734 - - - - Manufacturing example 10 4105 4860 - - - - Manufacturing Example 11 4107 6769 - - - -

[0099] As shown in Table 1 to Table 3, no CaB2O4 was found in the ferrite sintered magnet of Preparation Examples 1 to 4, 9, and 10. However, in the ferrite sintered magnet of Preparation Examples 5 to 8, and 11, CaB2O4 was found in the first sub-phase. Furthermore, in these Preparation Examples, CaB2O4 was not found in any phase other than the first sub-phase. In these Preparation Examples, the ferrite sintered magnet had a sufficiently high coercive force. Furthermore, in Preparation Examples 5 and 6, it was confirmed that the temperature coefficient of HcJ had negative characteristics, and irreversible demagnetization by low temperature was not produced. <Analyse 1 der Zusammensetzung jeder Phase>

[0100] Fig. 5 is a photograph of the observed image (magnification: 2000 times) when the cross-sectional area of ​​the ferrite sintered magnet of Preparation Example 6 is observed with a scanning transmission electron microscope. Fig. Figure 9 is a photograph of the observed image (magnification: 10,000 times) when the cross-sectional area of ​​the ferrite sintered magnet of Preparation Example 6 is observed with a scanning transmission electron microscope. In the photographs of Fig. 5 and Fig. In Figure 9, a black area represents the first sub-phase, a white area represents the second sub-phase, and the other gray areas represent the main phase. The composition of the main phase and the first sub-phase contained in the ferrite sintered magnet of Production Example 6 and Production Example 11 was measured using the above-described TEM / EDX, and the composition of the second sub-phase was measured using the above-described TEM / EELS. The same measurement was performed for Production Example 1.

[0101] The compositions of the main phase, the first sub-phase, and the second sub-phase of Preparation Examples 6 and 11 are shown in Table 4. The composition of the main phase of Preparation Examples 6 and 11 was approximately equal to the overall composition of the ferrite sintered magnet. For the main phase and the first sub-phase, the measurement was performed with respect to 13 randomly selected spots, and when the total of Si, Ca, Fe, Co, and La was set to 100 atomic%, an atomic ratio of each of the elements was obtained. The arithmetic mean thereof was determined to be the composition of each of the phases. For the second sub-phase, the measurement was performed with respect to 13 randomly selected spots, and when the total of Si, Ca, Fe, Co, La, and B was set to 100 atomic%, an atomic ratio of each of the elements was obtained.The arithmetic mean was determined to be the composition of the second minor phase. Co was not included in the second minor phase of Preparation Examples 6 and 11. [Table 4] Element Manufacturing example 6 Production example 11 Main phase First side phase Second sub-phase Main phase First side phase Second sub-phase Si 0,3 2,7 1,3 0,1 3,4 0,3 Ca 3,7 45,9 4,3 5,6 45,0 5,1 Fe 85,8 4,7 44,9 84,7 6,2 47 Co 4,0 0,0 0,5 3,7 0,0 0,7 La 6,2 8,9 49,0 5,9 8,7 46,9 B - 37,8 - - 36,7 - In total 100 100 100 100 100 100

[0102] In the ferrite sintered magnet of Production Example 1, it was confirmed that the main phase and the second sub-phase were contained, but the first sub-phase was not contained. Then, two types of phases with very different compositions were found as the second sub-phase. The composition of each of the phases was measured as in Production Examples 6 and 11. The results are shown in Table 5. The compositions of two types of phases as the second sub-phase are shown in Table 5. The composition of the main phase of Production Example 1 was approximately the same as the overall composition of the ferrite sintered magnet. [Table 5] element Manufacturing example 1 Main phase Second secondary phase (1) Second secondary phase (2) Si 0,1 0,3 17,9 Ca 3,7 9,3 53,1 Fe 87,6 44,4 21,2 Co 2,9 1,0 2,3 La 5,7 45,0 2,2 B - - 3,2 In total 100 100 100

[0103] In the table, "-" indicates that no measurement was taken. <Analyse 2 der Zusammensetzung jeder Phase>

[0104] As in "Analysis 1 of the Composition of Each Phase," the composition of the main phase contained in the ferrite sintered magnet of each of the preparation examples was measured using the TEM / EDX described above, and when the total of Si, Ca, Fe, Co, and La was set to 100 atomic%, the elemental ratio of each of the elements was obtained. Then, the atomic ratio of Co to the total of Fe and Co in the main phase was obtained. The results are shown in Table 6. In addition, for the entire ferrite sintered magnet, the atomic ratio of Co to the total of Fe and Co was obtained based on the measured values ​​in Table 1. The results are shown in Table 6.

[0105] When the atomic ratio [Co / (Fe + Co)] in the main phase described above was set to a ratio (A) and the atomic ratio [Co / (Fe + Co)] in the entire ferrite sintered magnet was set to a ratio (B), a ratio of ratio (A) to ratio (B) was calculated. The results are also shown in Table 6. [Table 6] Manufacturing example Main phase Co / (Fe + Co) (%) Ferrite sintered magnet Co / (Fe + Co) (%) Co in main phase / Co in sintered magnet Manufacturing example 1 3,2 2,92 1,09 Manufacturing example 2 3,2 2,89 1,11 Manufacturing example 3 3,5 3,06 1,14 Manufacturing example 4 3,6 3,06 1,18 Manufacturing example 5 4,4 3,06 1,44 Manufacturing example 6 4,5 2,96 1,52 Production example 7 3,8 3,06 1,24 Manufacturing example 8 3,7 3,06 1,21 Manufacturing example 9 3,3 3,06 1,08 Manufacturing example 10 3,6 4,00 0,90 Production example 11 4,2 4,00 1,05

[0106] Considering all preparation examples, in Preparation Examples 5 to 8, where CaB2O4 was included in the second minor phase, the ratio of ratio (A) to ratio (B) was greater than 1.2. This indicates that Co in the main phase is effectively incorporated into the main phase, and that Fe in the main phase is sufficiently substituted with Co. Thus, it is assumed that improving the ratio of Fe to Co substitution in the main phase contributes to an improvement in the coercive force and temperature properties.

[0107] In Preparation Example 11, in which CaB2O4 was contained in the second minor phase, "Co in main phase / Co in sintered magnet" was lower than in Preparation Examples 5 to 8. It is considered that this is because, as shown in Table 1, in Preparation Example 11, the ratio of Co to Fe in the entire ferrite sintered magnet was high, and thus Co was already sufficiently incorporated into the main phase. It follows that even in a case where the Co content in the entire ferrite sintered magnet is relatively low (Preparation Examples 5 to 8), CaB2O4 of the second minor phase has an action of effectively incorporating Co into the main phase.< / zusammensetzungsanalyse>

Claims

[1] Ferrite sintered magnet comprising: a main phase formed by ferrite with a hexagonal crystal structure of the magnetoplumbite type, wherein the main phase contains Fe and Co, and a heterophase which is a crystalline phase different from the main phase and contains a first minor phase, wherein the first minor phase contains La, Ca, Si, B and Fe, and in the first minor phase an atomic ratio of Fe is lower than that in the main phase, wherein the ferrite sintered magnet contains CaB2O4, wherein the first minor phase contains CaB2O4, and wherein the area ratio of CaB2O4 in the first minor phase on the total cross-sectional area of ​​the ferrite sintered magnet is 1.5% to 6.3%. [2] The ferrite sintered magnet according to claim 1, wherein the content of B in the ferrite sintered magnet is greater than or equal to 0.2 mass% in terms of B2O3. [3] The ferrite sintered magnet according to claim 1 or 2, wherein an area ratio of CaB2O4 to a total cross-sectional area of ​​the ferrite sintered magnet is 0.05% to 2%. [4] The ferrite sintered magnet according to any one of claims 1 to 3, wherein when an atomic ratio of Co to the total of Fe and Co in the main phase is set to a ratio (A) and an atomic ratio of Co to the total of Fe and Co in an entire magnet is set to a ratio (B), a ratio of the ratio (A) to the ratio (B) is greater than 1.

2. [5] The ferrite sintered magnet according to any one of claims 1 to 4, wherein a temperature coefficient of a coercive field strength is -0.06 to 0% / °C. [6] Engine, comprising: the ferrite sintered magnet according to one of claims 1 to 5. [7] Generator comprising: the ferrite sintered magnet according to one of claims 1 to 5.

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