Ferrite sintered magnet, method for manufacturing same, and ferrite calcined body

Abstract

[Problem] To provide a CaLaCo-based ferrite sintered magnet that has a novel composition, wherein it is possible to stably obtain high Hk / cj while suppressing a decrease in Br and HcJ. [Solution] The method comprises: a raw material powder mixing step of mixing raw material powders to obtain a mixed raw material powder, the raw material powders being such that, in the general formula in which the atomic ratio of metal elements of Ca, R, A, Fe, and Co is expressed as Ca1-x-yRxAyFe2n'-z'Coz', the x, y, z', and n' satisfy the relationships 0.30≤1-x-y≤0.55, 0.25≤x≤0.40, 0.15≤y≤0.40, 1-x-y>y, 0≤z'<0.18, and 8.5≤2n'-z'<11.0; a calcination step; a pulverization step; a molding step; and a firing step. The raw material powders of Co are added to the calcined body or the powder of the calcined body so that z, which is the Co content in the ferrite sintered magnet, satisfies the relationships 0<z≤0.18 and z'<z in total.

Description

Ferrite sintered magnet and method for manufacturing the same, and ferrite calcined body

[0001] This disclosure relates to ferrite sintered magnets, methods for manufacturing the same, and ferrite calcined bodies.

[0002] Although ferrite sintered magnets have a maximum energy product that is only about one-tenth that of rare-earth sintered magnets (for example, NdFeB sintered magnets), they offer excellent cost performance because their main raw material is inexpensive iron oxide, and they are also chemically extremely stable. For this reason, they are used in a wide range of applications such as motors and speakers, and their global production volume remains the largest among magnetic materials.

[0003] Typical ferrite sintered magnets are Sr ferrites with a magnetoplanbite structure, and their basic composition is SrFe １２ O １９ It is represented as follows: In the late 1990s, SrFe １２ O １９ Sr ２＋ Part of La ３＋ Replace with Fe ３＋ Co ２＋ The magnetic properties of ferrite magnets have greatly improved with the practical application of Sr-La-Co ferrite sintered magnets (sometimes abbreviated as "SrLaCo magnets"), which are substituted with . Furthermore, in 2007, Ca-La-Co ferrite sintered magnets (sometimes abbreviated as "CaLaCo magnets"), which have even better magnetic properties, were put into practical use.

[0004] In the above-mentioned SrLaCo-based magnets and CaLaCo-based magnets, Co is indispensable for obtaining high magnetic properties. The SrLaCo-based magnet contains Co at an atomic ratio of about 0.2 (Co / Fe = 0.017, that is, about 1.7% of the Fe content), and the CaLaCo-based magnet contains Co at an atomic ratio of about 0.3 (Co / Fe = 0.03, that is, about 3% of the Fe content). The price of Co (oxidized Co) corresponds to ten to dozens of times that of iron oxide, which is the main raw material of ferrite sintered magnets. Therefore, in the CaLaCo-based magnet, an increase in raw material cost is inevitable compared with the SrLaCo-based magnet. Since the greatest attraction of ferrite sintered magnets lies in their low cost, even if they have high magnetic properties, they are difficult to be accepted in the market if the price is high. Therefore, globally, the demand for SrLaCo-based magnets is still high.

[0005] In view of the current situation, the inventor has proposed a general formula showing the atomic ratio of metal elements of Ca, R, A, Fe, and Co (where R is at least one rare earth element including La as an essential element, and A is Sr and / or Ba): Ca １－ｘ－ｙ R ｘ A ｙ Fe ２ｎ－ｚ Co ｚ In this formula, x, y, and z, as well as n (where 2n is the molar ratio and is expressed as 2n = (Fe + Co) / (Ca + La + A)), satisfy 0.15 ≤ x ≤ 0.35, 0.05 ≤ y ≤ 0.40, 1 - x - y > y, 0 < z ≤ 0.18, and 7.5 ≤ 2n - z < 11.0. A novel CaLaCo-based ferrite sintered magnet (Patent Document 1) with such a composition has been proposed.

[0006] Japanese Patent No. 6927404

[0007] Among various applications where ferrite sintered magnets are used, there is a strong demand for high performance in motors for automotive electrical equipment, motors for household appliances, etc. In recent years, against the backdrop of soaring prices of rare earth raw materials and the emergence of procurement risks, the application of ferrite sintered magnets has also been studied in industrial motors and drive motors / generators for EV (Electric Vehicle) / HEV, which have hitherto used only rare earth magnets.

[0008] To use it for those applications, a high residual magnetic flux density B is required to suppress demagnetization due to a strong demagnetizing field when thinned and demagnetization at high temperatures (e.g., 140°C). ｒ (Hereafter simply referred to as "B") ｒ (There are cases where this is the case) and high coercivity H ｃＪ (Hereafter simply referred to as "coercivity" or "H") ｃＪ In addition to the case of a high aspect ratio (hereinafter referred to as "H"), there are cases where this is the case. ｋ / H ｃｊ It is necessary to have (in some cases) H ｋ In the second quadrant of the J (magnetization magnitude) - H (magnetic field strength) curve, J is 0.90 J. ｒ Or 0.95J ｒ This is the value of H at the position where the value is (J ｒ This is remanent magnetization, J ｒ = B ｒ ). 0.90J or less ｒ H in this case ｋ H using ｋ / H ｃｊ to "H ｋ (90) / H ｃｊ ", 0.95J ｒ H in this case ｋ H using ｋ / H ｃｊ to "H ｋ (95) / H ｃｊ There are cases where this is the case.

[0009] The ferrite sintered magnet according to Patent Document 1 has high B ｒ and high H ｃＪ This material has the properties to reduce the amount of Co used compared to conventional SrLaCo-based magnets and CaLaCo-based magnets. Specifically, it makes it possible to provide a ferrite sintered magnet that has the same magnetic properties as conventional SrLaCo-based magnets with a lower Co content (less than 0.15 atomic ratio) than conventional SrLaCo-based magnets. Furthermore, it is extremely superior in that it has magnetic properties that surpass conventional SrLaCo-based magnets, and in a preferred form, magnetic properties that are comparable to conventional CaLaCo-based magnets, with a Co content equivalent to that of conventional SrLaCo-based magnets (0.15 to 0.18 atomic ratio).

[0010] However, the ferrite sintered magnet according to Patent Document 1 is H ｋ(95) / H ｃｊ The percentage may be around 90% or less, and good H ｋ / H ｃｊ There was a problem in that it could not be obtained stably. Also, the ferrite sintered magnet according to Patent Document 1 is B ｒ If you increase the firing temperature to improve it (for example, from 1210°C to 1230°C), H ｋ / H ｃｊ There was a problem in that it decreased significantly.

[0011] Embodiments of this disclosure are ferrite sintered magnets having the same components and composition as Patent Document 1, B ｒ and H ｃＪ While suppressing the decline, maintain a stable high H ｋ / H ｃｊ This enables the provision of ferrite sintered magnets that can obtain B. ｒ Even when the firing temperature is increased for improvement, H ｋ / H ｃｊ This makes it possible to provide ferrite sintered magnets that can suppress the decrease in performance.

[0012] The present inventors have developed a ferrite sintered magnet with the same components and composition as in Patent Document 1, and H ｋ / H ｃｊ We diligently researched ways to improve this. And, the Co raw material powder (Co) that had been added in the raw material powder mixing process before calcination (hereinafter sometimes referred to as "pre-addition") ３ O ４ By adding part or all of the powder after the calcination process and before the molding process (hereinafter sometimes referred to as "post-addition"), B ｒ and H ｃＪ While suppressing the decline, maintain a stable high H ｋ / H ｃｊ In addition to obtaining B ｒ Even when the firing temperature is increased for improvement, H ｋ / H ｃｊ We found that it is possible to suppress the decline of [the substance].

[0013] An exemplary method for manufacturing a ferrite sintered magnet, not limited to this disclosure, is provided by a general formula expressing the atomic ratios of the metallic elements Ca, R, A, Fe, and Co (wherein R is at least one rare earth element and essentially contains La, and A is Sr and / or Ba): Ca １－ｘ－ｙ R ｘ A ｙ Fe ２ｎ’－ｚ’ Co ｚ’ The process includes: a raw material powder mixing step to obtain a mixed raw material powder by mixing raw material powders that satisfy the following conditions: 0.30 ≤ 1 - x - y ≤ 0.55, 0.25 ≤ x ≤ 0.40, 0.15 ≤ y ≤ 0.40, 1 - x - y > y, 0 ≤ z' < 0.18, and 8.5 ≤ 2n' - z' < 11.0; a calcination step to obtain a calcined body by calcining the mixed raw material powder; a grinding step to obtain a calcined body powder by grinding the calcined body; a molding step to obtain a molded body by molding the calcined body powder; and a firing step to obtain a sintered body by firing the molded body. After the calcination process, raw material powder of Co is added to the calcined body or the powder of the calcined body before the molding process such that the total Co content z in the ferrite sintered magnet satisfies 0 < z ≤ 0.18 and z' < z.

[0014] In an exemplary method for manufacturing a ferrite sintered magnet, which is not limited to this disclosure, the H of the ferrite sintered magnet ｋ (95) / H ｃＪ It exceeds 86%. However, H ｋ (95) is the second quadrant of the J-H curve, where J is 0.95 × J ｒ This is the value of H at the position where the value is obtained (J is the magnitude of magnetization, H is the strength of the magnetic field, J ｒ (This is remanent magnetization). In one embodiment, H ｋ (95) / H ｃＪ It is over 90%.

[0015] In one embodiment, 1-x-y is 0.30 ≤ 1-x-y ≤ 0.45.

[0016] In one embodiment, x is 0.30 ≤ x ≤ 0.35.

[0017] In one embodiment, y is 0.20 ≤ y ≤ 0.30.

[0018] In one embodiment, z' and z are such that z' / z ≤ 0.5.

[0019] In one embodiment, z' and z satisfy z' / z ≤ 0.5, and z ≤ 0.15.

[0020] In one embodiment, 2n'-z' is 9.0 ≤ 2n'-z' ≤ 10.0.

[0021] In one embodiment, after the calcination process and before the molding process, 1.5 mass% or less (excluding 0 mass%) of SiO per 100 mass% of the calcined body or the powder of the calcined body is added. ２ The process further includes the addition of [a certain substance].

[0022] In one embodiment, after the calcination process and before the molding process, the calcined body or the powder of the calcined body is treated with CaO equivalent to 1.5 mass% or less (excluding 0 mass%) of CaCO3. ３ The process further includes the addition of [a certain substance].

[0023] In exemplary embodiments, not limited to the present disclosure, the ferrite sintered magnet is a ferrite sintered magnet containing a plurality of first ferrite main phase particles having a core-shell structure and a plurality of second ferrite main phase particles not having a core-shell structure, wherein in EPMA analysis of any cross-section of the ferrite sintered magnet, the average value of the La content in the shell portion of the plurality of first ferrite main phase particles (La ｓ１ ) and the average value of the La content in the core (La ｃ１ The difference between (La ｓ１－ La ｃ１ ) and the average value of the La content in the outer shell of the plurality of second ferrite main phase particles (La ｓ２ ) and the average value of La content in the center (La ｃ２ The difference between (La ｓ２－ La ｃ２ When that is the case, the above (La ｓ１－ La ｃ１ ) and (La ｓ２－ Laｃ２ is the absolute value of the difference from (La ｓ１－ La ｃ１ ), i.e., |(La ｓ２－ La ｃ２ )| is 0.5 mass% or less.

[0024] In one embodiment, the average value of the Co content (Co ｓ１ ) in the shell portion of the plurality of first ferrite main phase particles and the average value of the Co content (Co ｃ１ ) in the core portion are defined as (Co ｓ１－ Co ｃ１ ). The average value of the Co content (Co ｓ２ ) in the outer shell portion of the plurality of second ferrite main phase particles and the average value of the Co content (Co ｃ２ ) in the central portion are defined as (Co ｓ２－ Co ｃ２ ). When the absolute value of the difference between (Co ｓ１－ Co ｃ１ ) and (Co ｓ２－ Co ｃ２ ), i.e., |(Co ｓ１－ Co ｃ１ ) - (Co ｓ２－ Co ｃ２ )| is 0.1 mass% or less.

[0025] In one embodiment, in the general formula showing the atomic ratio of the metal elements of Ca, R, A, Fe, and Co (where R is at least one rare earth element including La as an essential element, and A is Sr and / or Ba): Ca １－ｘ－ｙ R ｘ A ｙ Fe ２ｎ－ｚ Co ｚ , x, y, z, and n (where 2n is the molar ratio and 2n = (Fe + Co) / (Ca + R + A)) satisfy 0.30 ≦ 1 - x - y ≦ 0.55, 0.25 ≦ x ≦ 0.40, 0.15 ≦ y ≦ 0.40, 1 - x - y > y, 0 < z ≦ 0.18, and 8.5 ≦ 2n - z < 11.0.

[0026] In one embodiment, H ｋ (95) / H ｃＪ is more than 86%. However, H ｋ(95) is the second quadrant of the J-H curve, where J is 0.95 × J ｒ This is the value of H at the position where the value is obtained (J is the magnitude of magnetization, H is the strength of the magnetic field, J ｒ (This refers to remanent magnetization.)

[0027] In one embodiment, H ｋ (95) / H ｃＪ That is over 90%.

[0028] In one embodiment, 1-x-y is 0.30 ≤ 1-x-y ≤ 0.50.

[0029] In one embodiment, x is 0.30 ≤ x ≤ 0.35.

[0030] In one embodiment, y is 0.20 ≤ y ≤ 0.30.

[0031] In one embodiment, z is 0 < z ≤ 0.15.

[0032] In one embodiment, 2n-z is 8.5 ≤ 2n-z ≤ 10.0.

[0033] In exemplary embodiments, the ferrite calcined body of this disclosure has a general formula representing the atomic ratio of the metallic elements Ca, R, A, Fe, and Co (wherein R is at least one rare earth element and essentially contains La, and A is Sr and / or Ba): Ca １－ｘ－ｙ R ｘ A ｙ Fe ２ｎ’－ｚ’ Co ｚ’ In this mixture, x, y, z', and n' (where 2n' is a molar ratio and is expressed as 2n' = (Fe + Co) / (Ca + R + A)) satisfy the following conditions: 0.30 ≤ 1 - x - y ≤ 0.55, 0.25 ≤ x ≤ 0.40, 0.15 ≤ y ≤ 0.40, 1 - x - y > y, 0 ≤ z' < 0.18, and 8.5 ≤ 2n' - z' < 11.0, and the mixture contains 1.6 mass% or more of La orthoferrite phase.

[0034] In one embodiment, z' is 0 ≤ z' ≤ 0.09.

[0035] In one embodiment, the system contains ferrite-dominant phase particles having a c-axis length of 23.0000 Å or more.

[0036] In one embodiment, the material contains ferrite-dominant phase particles having a c-axis length / a-axis length of 3.9030 or more.

[0037] In one embodiment, the material contains a magnetic phase in which magnetization disappears or a magnetic phase transition occurs at temperatures above 454°C.

[0038] In one embodiment, the content of ferrite-dominant phase particles is 98.4 mass% or less.

[0039] According to embodiments of this disclosure, in a ferrite sintered magnet having the same components and composition as Patent Document 1, B ｒ and H ｃＪ While suppressing the decline, maintain a stable high H ｋ / H ｃｊ This makes it possible to provide a ferrite sintered magnet that can obtain B. Alternatively, according to an embodiment of the present disclosure, in a ferrite sintered magnet having the same components and composition as in Patent Document 1, B ｒ Even when the firing temperature is increased for improvement, H ｋ / H ｃｊ This makes it possible to provide ferrite sintered magnets that can suppress the decrease in performance.

[0040] Co addition method and B under sintering condition A in Experimental Example 1 ｒ This figure shows the relationship between the Co addition method and H under sintering condition A in Experimental Example 1. ｃｊ This figure shows the relationship between the Co addition method and H under sintering condition A in Experimental Example 1. ｋ (95) / H ｃｊ This figure shows the relationship between the Co addition method and H under sintering condition A in Experimental Example 1. ｋ (90) / H ｃｊ This figure shows the relationship between the Co addition method and B under sintering conditions B in Experimental Example 1. ｒ This figure shows the relationship between the Co addition method and H under sintering condition B in Experimental Example 1. ｃｊ This figure shows the relationship between the Co addition method and H under sintering condition B in Experimental Example 1. ｋ (95) / H ｃｊThis figure shows the relationship between the Co addition method and H under sintering condition B in Experimental Example 1. ｋ (90) / H ｃｊ This figure shows the relationship between the two. This figure shows an example of a backscattered electron image obtained by SEM of ferrite sintered magnet sample No. 1* from Experimental Example 1. This figure shows an example of a backscattered electron image obtained by SEM of ferrite sintered magnet sample No. 25 from Experimental Example 1.

[0041] The method for manufacturing a ferrite sintered magnet according to this disclosure is a general formula representing the atomic ratio of the metallic elements Ca, R, A, Fe, and Co (wherein R is at least one rare earth element and essentially contains La, and A is Sr and / or Ba): Ca １－ｘ－ｙ R ｘ A ｙ Fe ２ｎ’－ｚ’ Co ｚ’ The process includes: a raw material powder mixing step to obtain a mixed raw material powder by mixing raw material powders that satisfy the following conditions: 0.30 ≤ 1 - x - y ≤ 0.55, 0.25 ≤ x ≤ 0.40, 0.15 ≤ y ≤ 0.40, 1 - x - y > y, 0 ≤ z' < 0.18, and 8.5 ≤ 2n' - z' < 11.0; a calcination step to obtain a calcined body by calcining the mixed raw material powder; a grinding step to obtain a calcined body powder by grinding the calcined body; a molding step to obtain a molded body by molding the calcined body powder; and a firing step to obtain a sintered body by firing the molded body. The present invention is characterized by adding raw material powder of Co to the calcined body or the powder of the calcined body after the calcination step and before the molding step, such that the total Co content z in the ferrite sintered magnet satisfies 0 < z ≤ 0.18 and z' < z.

[0042] The steps in the embodiments of this disclosure are described below.

[0043] In the aforementioned raw material powder mixing step, the raw material powder to be mixed satisfies the following: General formula showing the atomic ratio of the metallic elements Ca, R, A, Fe, and Co (wherein R is at least one rare earth element and must contain La, and A is Sr and / or Ba): Ca １－ｘ－ｙ R ｘ A ｙFe ２ｎ’－ｚ’ Co ｚ’ In this case, x, y, z', and n' (where 2n' is a molar ratio and is expressed as 2n' = (Fe + Co) / (Ca + R + A)) satisfy the following conditions: 0.30 ≤ 1 - x - y ≤ 0.55, 0.25 ≤ x ≤ 0.40, 0.15 ≤ y ≤ 0.40, 1 - x - y > y, 0 ≤ z' < 0.18, and 8.5 ≤ 2n' - z' < 11.0.

[0044] The atomic ratio 1-x-y (Ca content) is 0.30 ≤ 1-x-y ≤ 0.55. If 1-x-y is less than 0.30 or greater than 0.55, the B rating is high. ｒ and high H ｃＪ It is not possible to obtain this. Preferably, 1-x-y is 0.30 ≤ 1-x-y ≤ 0.50, and more preferably 0.30 ≤ 1-x-y ≤ 0.45.

[0045] The atomic ratio x (content of R) is 0.25 ≤ x ≤ 0.40. R is at least one rare earth element and must contain La. The content of rare earth elements other than La is preferably 50% or less of the total amount of R in molar ratio, and more preferably 0% (R = La, excluding impurities). If x is less than 0.25 or greater than 0.40, the B is high. ｒ and high H ｃＪ It is not possible to obtain this. It is preferable that x is 0.30 ≤ x ≤ 0.35.

[0046] The atomic ratio y (content of A) is 0.15 ≤ y ≤ 0.40. A is Sr and / or Ba. It is preferable that A = Sr. If y is less than 0.15 or greater than 0.40, the B content is high. ｒ and high H ｃＪ It is not possible to obtain this. It is preferable that y is 0.20 ≤ x ≤ 0.30.

[0047] The atomic ratio z' (Co content) in the raw material powder mixing step is 0 ≤ z' < 0.18. The atomic ratio z' (pre-addition amount) in the raw material powder mixing step and the amount z-z' (post-addition amount) added to the calcined body or calcined body powder after the calcination step and before the molding step are adjusted so that the atomic ratio z, which is the Co content in the ferrite sintered magnet obtained by the embodiment of this disclosure, satisfies 0 < z ≤ 0.18 and z' < z. ｃＪ If z exceeds 0.18, the reduction in Co usage cannot be obtained. It is preferable that z is 0 < z ≤ 0.15. Furthermore, it is preferable that z is 0.08 ≤ z ≤ 0.18, and more preferably 0.08 ≤ z ≤ 0.15.

[0048] The atomic ratio 2n'-z' (Fe content) is 8.5 ≤ 2n'-z' < 11.0. If 2n'-z' is less than 8.5 or greater than 11.0, the B rating is high. ｒ and high H ｃＪ It is not possible to obtain it.

[0049] The above general formula is shown in terms of the atomic ratio of metal elements, but the composition containing oxygen (O) is shown in the general formula: Ca １－ｘ－ｙ R ｘ A ｙ Fe ２ｎ’－ｚ’ Co ｚ’ O α It is expressed as follows. The number of moles of oxygen α is basically α = 19, but it varies depending on the valencies of Fe and Co, the values ​​of x and y and n, etc. Also, the ratio of oxygen to metal elements changes due to oxygen vacancies (vacancies) when calcined in a reducing atmosphere, changes in the valency of Fe in the ferrite phase, changes in the valency of Co, etc. Therefore, the actual number of moles of oxygen α may deviate from 19. For this reason, in this embodiment, the composition is expressed in terms of the atomic ratio of metal elements, which is the easiest to identify.

[0050] As raw material powders, compounds such as oxides, carbonates, hydroxides, nitrates, and chlorides of each metal can be used, regardless of their valency. A solution of the raw material powder may also be used. Examples of Ca compounds include Ca carbonates, oxides, and chlorides. A typical example is CaCO3. ３As an example of a compound of R, La ２ O ３ Oxides such as La(OH) ３ Hydroxides such as La ２ (CO ３ ) ３ 8H ２ Examples include carbonates such as O. Typically, La(OH) ３ Examples of compounds of element A include carbonates, oxides, and chlorides of Sr and / or Ba. Typically, SrCO ３ BaCO ３ Examples of Fe compounds include iron oxide, iron hydroxide, iron chloride, and mill scale. Typically, Fe ２ O ３ As for compounds of Co, CoO, Co ３ O ４ Oxides such as CoOOH, Co(OH) ２ Hydroxides such as CoCO2 ３ Carbonates such as m ２ CoCO ３ ・m ３ Co(OH) ２ ・m ４ H ２ Basic carbonates such as O (m ２ , m ３ , m ４ (where is a positive number) is an example. Typically, Co ３ O ４ That is the case.

[0051] To accelerate the reaction during calcination, use B as needed. ２ O ３ , H ３ BO ３ Compounds containing B (boron), such as H, may be added up to about 1 mass%. ３ BO ３ Adding H is effective in improving magnetic properties. ３ BO ３ The amount added is preferably 0.3 mass% or less. ３ BO ３Since it also has the effect of controlling the shape and size of crystal grains during calcination, it may be added after calcination (before fine grinding or before calcination), or it may be added both before and after calcination. In that case, H ３ BO ３ The total amount of this substance can be added up to approximately 1 mass%, and it is preferable that the total amount added be 0.3 mass% or less.

[0052] The raw material powders may be blended and mixed using either a wet or dry method. Mixing with a medium such as steel balls allows for more uniform mixing of the raw material powders. In the case of a wet method, it is preferable to use water as the dispersion medium. Known dispersants such as ammonium polycarboxylate and calcium gluconate may be used to improve the dispersibility of the raw material powders. The mixed raw material slurry may be calcined as is, or the raw material slurry may be dehydrated before calcination.

[0053] In the calcination process, the mixed raw material powder obtained by dry or wet mixing is heated using an electric furnace, gas furnace, or the like. This causes a solid-phase reaction to form a ferrite compound with a hexagonal magnetoplumbite (M-type) structure. This process is called "calcination," and the resulting compound is called a "calcined body." Therefore, the ferrite calcined body in the embodiments of this disclosure can be rephrased as a ferrite compound.

[0054] The ferrite calcined body of the embodiments of this disclosure and the main phase constituting the ferrite sintered magnet obtained by the embodiments of this disclosure are both compound phases (ferrite phases) having a hexagonal magnetoplumbite (M-type) structure. Generally, magnetic materials, especially sintered magnets, are composed of multiple compounds, and the compound that determines the properties of the magnetic material (physical properties, magnetic properties, etc.) is defined as the "main phase." Hereinafter, the "main phase" may be referred to as "ferrite main phase particles" or "M-phase."

[0055] "Having a hexagonal magnetoplanvite (M-type) structure" means that when the X-ray diffraction of a ferrite calcined body or ferrite sintered magnet is measured under general conditions, the X-ray diffraction pattern mainly observed is that of a hexagonal magnetoplanvite (M-type) structure.

[0056] In the calcination process, a solid-state reaction proceeds in which the ferrite phase is formed as the temperature rises. If the calcination temperature is below 1100°C, unreacted hematite (iron oxide) remains, resulting in low magnetic properties. On the other hand, if the calcination temperature exceeds 1450°C, the crystal grains grow too large, which can require a considerable amount of time for grinding in the grinding process. Therefore, the calcination temperature is preferably between 1100°C and 1450°C. The calcination time is preferably between 0.5 hours and 5 hours. After calcination, the calcined material is preferably coarsely ground using a hammer mill or the like.

[0057] In the grinding process, the calcined body is ground (finely ground) using a vibratory mill, jet mill, ball mill, attritor, etc., to obtain calcined body powder (finely ground powder). The average particle size of the calcined body powder is preferably about 0.4 μm to 1.2 μm. In the embodiments of this disclosure, the value measured by the air permeability method using a powder specific surface area measuring device (e.g., Shimadzu SS-100) is referred to as the average particle size (average particle size). The grinding process may be either dry grinding or wet grinding, or a combination of both. In the case of wet grinding, water and / or a non-aqueous solvent (organic solvent such as acetone, ethanol, or xylene) is used as the dispersion medium. Typically, a slurry containing water (dispersion medium) and calcined body is produced. Known dispersants and / or surfactants may be added to the slurry in an amount of 0.2 mass% to 2 mass% by solid content ratio. After wet grinding, the slurry may be concentrated.

[0058] The molding process involves press-molding the slurry after the grinding process in a magnetic field while removing the dispersion medium. Press-molding in a magnetic field allows for alignment (orientation) of the crystal orientation of the powder particles, dramatically improving the magnetic properties. Furthermore, to further improve orientation, 0.1 mass% to 1 mass% each of a dispersant and a lubricant may be added to the slurry before molding. The slurry may also be concentrated before molding as needed. Concentration is preferably performed by centrifugation, filter pressing, etc.

[0059] In the firing process, the molded body obtained by press molding is degreased as necessary, and then fired (sintered) to obtain a sintered body (ferrite sintered magnet). The firing is carried out using an electric furnace, gas furnace, etc. The firing temperature is preferably around 1150°C to 1250°C. The firing time is preferably 0 hours (no holding at firing temperature) to 2 hours.

[0060] In embodiments of this disclosure, for example, as shown in the experimental examples described later, a firing process may be employed in which the heating rate is 1 to 4°C / min in a temperature range of 1100°C to the firing temperature, as disclosed in International Publication No. 2014 / 021149.

[0061] After the calcination process and before the molding process, a Co raw material powder is added to the calcined body or the powder of the calcined body (coarsely ground powder or finely ground powder) such that the total Co content z in the ferrite sintered magnet satisfies 0 < z ≤ 0.18 and z' < z. In other words, in the ferrite sintered magnet obtained by the embodiment of this disclosure, a Co raw material powder is added (post-added) to the calcined body or the powder of the calcined body after the calcination process and before the molding process such that the total z satisfies 0 < z ≤ 0.18 and z' < z. Post-addition of the Co raw material powder can be done by, for example, adding it to the calcined body obtained by the calcination process and then carrying out the grinding process, adding it in the middle of the grinding process, or adding and mixing it to the powder of the calcined body (finely ground powder) after the grinding process and then carrying out the molding process. The term "in total" refers to the sum of the atomic ratio z' (pre-addition amount) in the raw material powder mixing step and the amount z-z' (post-addition amount) added to the calcined body or calcined body powder after the calcination step and before the molding step. In ferrite sintered magnets, the total Co content z is preferably 0 < z ≤ 0.15. Furthermore, z is preferably 0.08 ≤ z ≤ 0.18, and more preferably 0.08 ≤ z ≤ 0.15.

[0062] It is preferable that the relationship z' / z ≤ 0.5 is satisfied between the atomic ratio z' (pre-added amount) in the raw material powder mixing process and the Co content z in the ferrite sintered magnet. That is, it is preferable that the pre-added amount and the post-added amount are in the relationship pre-added amount ≤ post-added amount. Alternatively, the pre-added amount of Co may be set to zero, and all Co may be added post-added. For example, if the Co content z in the ferrite sintered magnet is 0.18, the atomic ratio z' in the raw material powder mixing process is set to z' = 0, and approximately 4.53 mass% of Co raw material powder (Co) corresponding to 0.18 parts in atomic ratio is added so that z = 0.18. ３ O ４ It is preferable to add the powder at the end (add the entire amount at the end). Alternatively, the atomic ratio in the raw material powder mixing step is z' = 0.09 (half added beforehand), and approximately 2.25 mass% of Co raw material powder (Co) corresponding to 0.09 minutes of atomic ratio is added so that z = 0.18. ３ O ４ It is preferable to add the powder later (half the amount added later). Also, when z is 0.15, the atomic ratio z' in the raw material powder mixing step is set to z'=0, and approximately 1.40 mass% of Co raw material powder (Co) corresponding to 0.15 minutes in atomic ratio is added so that z=0.15. ３ O ４ It is preferable to add the powder at the end (add the entire amount at the end). Alternatively, the atomic ratio in the raw material powder mixing step is z' = 0.075 (half added beforehand), and approximately 0.69 mass% of Co raw material powder (Co) corresponding to 0.075 parts in atomic ratio is added so that z = 0.15. ３ O ４ It is preferable to add the powder later (half of the amount added later).

[0063] In addition to the mandatory steps listed above, the following optional steps may also be performed.

[0064] After the calcination process and before the molding process, a sintering aid may be added to the calcined body or the powder of the calcined body (coarsely ground powder or finely ground powder). The sintering aid may be SiO ２ only, or SiO ２ and CaCO ３It is preferable to add both. The ferrite sintered magnet obtained by the method for manufacturing a ferrite sintered magnet according to the embodiments of this disclosure belongs to the Ca-La-Co type ferrite sintered magnet, as is clear from its composition. In CaLaCo magnets, Ca is included as the main phase component, so unlike conventional SrLaCo magnets, SiO ２ CaCO ３ Even without adding sintering aids such as SiO, a liquid phase is formed and sintering can be performed. That is, in ferrite sintered magnets, the grain boundary phase is mainly formed by SiO. ２ CaCO ３ The ferrite sintered magnet of the present invention can be manufactured without adding H. ｃＪ To suppress the decrease, the following amount of SiO ２ and CaCO ３ It may be added.

[0065] SiO ２ When adding CaCO3, the amount to be added is preferably more than 0 mass% and 1.5 mass% or less, and more preferably 0.7 mass% or more and 1.2 mass% or less, relative to 100 mass% of the calcined body or calcined body powder to be added. ３ When adding SiO, the amount to be added is preferably more than 0 mass% and 1.5 mass% or less in terms of CaO, more preferably more than 0 mass% and 1.0 mass% or less, and even more preferably 0.4 mass% or more and 0.9 mass% or less, based on 100 mass% of the calcined body or calcined body powder to be added. The addition of the sintering aid can be done by, for example, adding it to the calcined body obtained by the calcination process and then carrying out the grinding process, adding it in the middle of the grinding process, or adding it to the calcined body powder (finely ground powder) after the grinding process, mixing it, and then carrying out the molding process. ２ and CaCO ３ In addition to Cr ２ O ３ Al ２ O ３ Other substances may be added. The amount of each of these added substances may be 1 mass% or less.

[0066] In the embodiments of this disclosure, CaCO３ All amounts added are expressed in terms of CaO equivalent. From the amount added in terms of CaO equivalent, CaCO ３ The amount to add is given by the formula: (CaCO2) ３ It can be calculated by (molecular weight of [the substance] × amount added in terms of CaO) / molecular weight of CaO. For example, 0.5 mass% CaCO2 in terms of CaO. ３ When adding, {(40.08 [atomic weight of Ca] + 12.01 [atomic weight of C] + 48.00 [atomic weight of O × 3] = 100.09 [CaCO2] ３} (molecular weight of [CaO]) × 0.5 mass% [amount added in CaO equivalent]) / (40.08 [atomic weight of Ca] + 16.00 [atomic weight of O] = 56.08 [molecular weight of CaO]) = 0.892 mass% [CaCO ３ The amount to be added is as follows:

[0067] After the firing process, known manufacturing processes such as processing, cleaning, and inspection may be carried out as needed.

[0068] The ferrite sintered magnet obtained by the manufacturing method of the ferrite sintered magnet according to the embodiment of this disclosure is basically the same as the ferrite sintered magnet according to Patent Document 1 in terms of components and composition, but the magnetic properties are different. The ferrite sintered magnet according to the embodiment of this disclosure has a stable high H compared to the ferrite sintered magnet according to Patent Document 1. ｋ / H ｃｊ You can obtain H ｋ (95) / H ｃＪ It exceeds 86%. In a preferred embodiment, H ｋ (95) / H ｃＪ It is 90% or more. In a preferred embodiment, H ｋ (90) / H ｃＪ It is 93% or more. Furthermore, the ferrite sintered magnet obtained by the method for manufacturing a ferrite sintered magnet according to the embodiment of this disclosure has a compositional distribution within the main phase particles that differs from that of the ferrite sintered magnet according to Patent Document 1, as described below. This compositional distribution within the main phase particles is H ｋ / H ｃｊ This is thought to be related to the improvement effect.

[0069] Both the ferrite sintered magnet described in Patent Document 1 and the ferrite sintered magnet of this disclosure obtained by the method for manufacturing the ferrite sintered magnet of the embodiment of this disclosure have a ferrite compound (ferrite phase) with a hexagonal magnetoplumbite (M-type) structure as the main phase constituting the magnet.

[0070] Furthermore, when any cross-section of any ferrite sintered magnet is observed using a backscattered electron image obtained by SEM, it can be seen that the ferrite main phase particles have a core-shell structure with a core portion and a shell portion distinguishable by the intensity of their colors (hereinafter sometimes referred to as "first ferrite main phase particles"), and that the ferrite main phase particles do not have a core-shell structure (cannot be distinguished by the intensity of their colors) (hereinafter sometimes referred to as "second ferrite main phase particles"). Figure 9 shows an example of a backscattered electron image obtained by SEM of a ferrite sintered magnet with all Co added beforehand (sample No. 1* in the experimental example described later, the ferrite sintered magnet according to Patent Document 1), and Figure 10 shows an example of a backscattered electron image obtained by SEM of a ferrite sintered magnet with all Co added afterward (sample No. 25 in the experimental example described later, the ferrite sintered magnet according to the embodiment of this disclosure). In Figures 9 and 10, the ferrite main phase particles indicated by A in the figures each have a dark core portion and a light shell portion, and it can be seen that they have a core-shell structure. There are many other ferrite main phase particles that have a core-shell structure besides A. On the other hand, there are many ferrite-dominant phase particles that do not have a core-shell structure, such as the ferrite-dominant phase particle shown as B in the figure.

[0071] As described above, the method for manufacturing a ferrite sintered magnet according to the embodiments of this disclosure is characterized in that, instead of pre-adding all of the Co raw material powder in the raw material powder mixing step before calcination, some or all of the Co raw material powder is added after the calcination step and before the molding step. However, the ferrite sintered magnet according to this disclosure obtained by post-adding the Co raw material powder also has characteristics that differ from the ferrite sintered magnet according to Patent Document 1.

[0072] The characteristic is that, in EPMA analysis of any cross-section of the ferrite sintered magnet according to this disclosure, the average value of the La content in the shell portion of the ferrite main phase particles (first ferrite main phase particles) having the core-shell structure (hereinafter referred to as "La") ｓ１" and the average value of the La content in the core (hereinafter referred to as "La ｃ１ The difference between (La ｓ１－ La ｃ１ ) and the average value of the La content in the outer shell of the ferrite main phase particles (second ferrite main phase particles) that do not have the core-shell structure (hereinafter referred to as "La") ｓ２ " and the average value of the La content in the center (hereinafter referred to as "La ｃ２ The difference between (La ｓ２－ La ｃ２ When this is the case, the above (La ｓ１－ La ｃ１ ) and (La ｓ２－ La ｃ２ The absolute value of the difference between (La) ｓ１－ La ｃ１ )-(La ｓ２－ La ｃ２ )| becomes 0.5 mass% or less. The above (La ｓ１－ La ｃ１ ) is (La ｓ１－ La ｃ１ Preferably, (La ｓ１－ La ｃ１ ) and (La ｓ２－ La ｃ２ ) is (La ｓ１－ La ｃ１ )≧(La ｓ２－ La ｃ２ It is preferable that the relationship is (La ｓ２－ La ｃ２ ) ≥ 0 is also acceptable.

[0073] On the other hand, a ferrite sintered magnet obtained by pre-adding all of the Co raw material powder, such as the ferrite sintered magnet described in Patent Document 1, is as follows: |(La ｓ１－ La ｃ１ )-(La ｓ２－ La ｃ２ )| exceeds 0.5 mass%. The reason why the compositional distribution within the main phase particles differs depending on the addition method (timing of addition) of the Co raw material powder is not clear, but by adding the Co raw material powder later, the average value La of the La content in the shell portion of the ferrite main phase particles having a core-shell structure within the main phase particles ｓ１And the average value of La content in the core part ｃ１ The difference (La ｓ１－ La ｃ１ ) and the average value of La content in the outer shell of ferrite-dominant phase particles that do not have a core-shell structure ｓ２ and the average value of La content in the central part ｃ２ The difference (La ｓ２－ La ｃ２ The difference with ) becomes smaller (the composition distribution of La becomes uniform), and as a result H ｋ / H ｃｊ It is thought that this will improve.

[0074] The average value is preferably the average value of the content based on EPMA analysis of two or more different ferrite main phase particles. More preferably, it is five or more different ferrite main phase particles, and even more preferably, ten or more different ferrite main phase particles. The outer shell portion of the ferrite main phase particle that does not have a core-shell structure refers to the portion from half the radius of the ferrite main phase particle towards the outer periphery. The central portion of the ferrite main phase particle that does not have a core-shell structure refers to the portion from half the radius of the ferrite main phase particle towards the center.

[0075] In the EPMA analysis described above, the cross-section of the ferrite sintered magnet observed can be either the c-plane (a plane perpendicular to the orientation direction) or the ab-plane (a plane parallel to the orientation direction), but the c-plane tends to be easier to observe. In the above, an example was given of a core-shell structure having a dark core and a light shell, but there are also main phase particles that have the opposite arrangement, with a dark shell and a light core.

[0076] Just as the distribution of La within the main phase particles becomes uniform, the compositional distribution of Co within the main phase particles also becomes uniform. That is, in EPMA analysis of any cross-section of the ferrite sintered magnet according to this disclosure, the average value of the Co content in the shell portion of the ferrite main phase particles having the core-shell structure (first ferrite main phase particles) (hereinafter referred to as "Co") ｓ１ " and the average value of the Co content in the core (hereinafter referred to as "Co ｃ１ The difference between (Co) ｓ１－ Co ｃ１) and the average value of the Co content in the outer shell of the ferrite main phase particles (second ferrite main phase particles) that do not have the core-shell structure (hereinafter referred to as "Co") ｓ２ ) and the average value of the Co content in the center (hereinafter referred to as "Co") ｃ２ The difference between (Co) ｓ２－ Co ｃ２ When this is the case, the above (Co ｓ１－ Co ｃ１ ) and (Co ｓ２－ Co ｃ２ The absolute value of the difference between (Co) and (Co) ｓ１－ Co ｃ１ ) - (Co ｓ２－ Co ｃ２ )| becomes 0.1 mass% or less. The above (Co ｓ１－ Co ｃ１ ) is (Co ｓ１－ Co ｃ１ It is preferable that ) > 0, and the above (Co ｓ１－ Co ｃ１ ) and (Co ｓ２－ Co ｃ２ ) is (Co ｓ１－ Co ｃ１ )≧(Co ｓ２－ Co ｃ２ It is preferable that the relationship is (Co ｓ２－ Co ｃ２ ) ≥ 0. A ferrite sintered magnet obtained by pre-adding the entire amount of Co raw material powder, such as the ferrite sintered magnet described in Patent Document 1, is the above |(Co ｓ１－ Co ｃ１ ) - (Co ｓ２－ Co ｃ２ ) | exceeds 0.1 mass%.

[0077] The ferrite sintered magnet of this disclosure obtained by the method for manufacturing a ferrite sintered magnet of the embodiment of this disclosure satisfies the following: General formula showing the atomic ratio of the metallic elements Ca, R, A, Fe, and Co (wherein R is at least one rare earth element and essentially contains La, and A is Sr and / or Ba): Ca １－ｘ－ｙ R ｘ A ｙ Fe ２ｎ－ｚ Co ｚIn this case, x, y, z, and n (where 2n is a molar ratio and is expressed as 2n = (Fe + Co) / (Ca + R + A)) satisfy the following conditions: 0.30 ≤ 1 - x - y ≤ 0.55, 0.25 ≤ x ≤ 0.40, 0.15 ≤ y ≤ 0.40, 1 - x - y > y, 0 < z ≤ 0.18, and 8.5 ≤ 2n - z < 11.0.

[0078] The reasons for limiting the atomic ratios 1-x-y (Ca content), x (R content), y (A content), z (Co content), and 2n-z (Fe content) are basically the same as those for limiting the raw material powder mixing process, although the lower limit of the Co content and preferred configurations of each content differ slightly from those for limiting the raw material powder. Therefore, an explanation is omitted. In the embodiments of this disclosure, the Fe content 2n-z in the ferrite sintered magnet is the same value as the Fe content 2n'-z' in the mixed raw material powder and the calcined ferrite body. The Co content z preferably satisfies 0 < z ≤ 0.15. Furthermore, z is preferably 0.08 ≤ z ≤ 0.18, and more preferably 0.08 ≤ z ≤ 0.15.

[0079] As described above, the ferrite sintered magnet obtained by the method for manufacturing a ferrite sintered magnet according to the embodiment of this disclosure has the characteristic that the compositional distribution within the main phase particles is different from that of the ferrite sintered magnet according to Patent Document 1. The ferrite calcined body according to the embodiment of this disclosure also has characteristics that are different from those of the ferrite calcined body according to Patent Document 1.

[0080] The ferrite calcined body of the embodiments of this disclosure is given by a general formula that shows the atomic ratio of the metallic elements Ca, R, A, Fe, and Co (wherein R is at least one rare earth element and essentially contains La, and A is Sr and / or Ba): Ca １－ｘ－ｙ R ｘ A ｙ Fe ２ｎ’－ｚ’ Co ｚ’In this mixture, x, y, z', and n' (where 2n' is a molar ratio and is expressed as 2n' = (Fe + Co) / (Ca + R + A)) satisfy the following conditions: 0.30 ≤ 1 - x - y ≤ 0.55, 0.25 ≤ x ≤ 0.40, 0.15 ≤ y ≤ 0.40, 1 - x - y > y, 0 ≤ z' < 0.18, and 8.5 ≤ 2n' - z' < 11.0, and the mixture contains 1.6 mass% or more of La orthoferrite phase.

[0081] The method for manufacturing a ferrite sintered magnet according to the embodiments of this disclosure is characterized by adding part or all of the Co raw material powder after the calcination process and before the molding process. Therefore, the atomic ratio z' (Co content) in the calcined ferrite body according to the embodiments of this disclosure is 0 ≤ z' < 0.18. In other words, the Co raw material powder is added afterwards so that the total Co content z in the ferrite sintered magnet satisfies 0 < z ≤ 0.18 and z' < z, resulting in a lower Co content than the final ferrite sintered magnet.

[0082] The ferrite calcined body of the embodiment of this disclosure contains 1.6 mass% or more of the La orthoferrite phase. On the other hand, the ferrite calcined body according to Patent Document 1, obtained by pre-adding the entire amount of Co raw material powder, contains 1.2 mass% or less of the La orthoferrite phase. The La orthoferrite phase (hereinafter sometimes referred to as "L phase") is LaFeO ３ ((Ca,La)FeO ３ It is a compound phase having a perovskite structure (including the case of ).

[0083] Furthermore, the ferrite calcined body of the embodiment of this disclosure also has the following characteristics: (a) It contains ferrite main phase particles with a c-axis length of 23.0000 Å or more. (b) It contains ferrite main phase particles with a c-axis length / a-axis length of 3.9030 or more. (c) It contains a magnetic phase in which magnetization disappears or a magnetic phase transition occurs at 454°C or higher. (d) The content ratio of ferrite main phase particles is 98.4 mass% or less.

[0084] On the other hand, in the ferrite calcined body according to Patent Document 1, obtained by pre-adding the entire amount of Co raw material powder, as shown in the experimental example described later, the c-axis length of the ferrite main phase particles is 22.9925 Å, and it does not contain ferrite main phase particles with a c-axis length of 23.0000 Å or more. Furthermore, the c-axis length / a-axis length ratio is 3.9027, and it does not contain ferrite main phase particles with a c-axis length / a-axis length ratio of 3.9030 or more.

[0085] Furthermore, the ferrite calcined body of the embodiment of this disclosure contains a magnetic phase in which magnetization disappears or a magnetic phase transition occurs at temperatures above 454°C, whereas the ferrite calcined body described in Patent Document 1 does not contain such a magnetic phase. Moreover, the ferrite calcined body of the embodiment of this disclosure has a ferrite main phase particle content of 98.4 mass% or less, whereas the ferrite calcined body described in Patent Document 1 has a ferrite main phase particle content of approximately 98.8%, which is not 98.4 mass% or less.

[0086] Thus, the ferrite calcined body of the embodiment of this disclosure has characteristics that differ from the ferrite calcined body of Patent Document 1. By adding part or all of the Co raw material powder to the ferrite calcined body of the embodiment of this disclosure having these characteristics after the calcination process and before the molding process, it is possible to obtain a ferrite sintered magnet according to the embodiment of this disclosure.

[0087] The reasons for limiting the atomic ratios 1-x-y (Ca content), x (R content), y (A content), z' (Co content), and 2n'-z' (Fe content) are the same as the reasons for limiting them in the raw material powder mixing process, so an explanation is omitted. When the Co content z in the ferrite sintered magnet is 0.18, it is preferable that the Co content z' in the calcined body is 0 ≤ z' ≤ 0.09. When the Co content z in the ferrite sintered magnet is 0.15, it is preferable that the Co content z' in the calcined body is 0 ≤ z' ≤ 0.075. In other words, it is preferable to pre-add an amount less than half the amount of z in the ferrite sintered magnet.

[0088] Embodiments of the present disclosure will be described in further detail by reference to examples, but the embodiments of the present disclosure are not limited thereto.

[0089] Experimental Example 1 As an experimental example based on the embodiment of this disclosure, the general formula Ca １－ｘ－ｙ R ｘ A ｙ Fe ２ｎ’－ｚ’ Co ｚ’ In this mixture, R = La and A = Sr, and the atomic ratios are such that x = 0.325, y = 0.25, 1 - x - y = 0.425, 2n' - z' = 9.50, z' = 0, 0.075, 0.15. ３ Powder, La(OH) ３ Powder, SrCO ３ powder, Fe ２ O ３ Powder and Co ３ O ４ The powder is weighed, and H is added to the total 100 mass% of the weighed powder. ３ BO ３ After adding 0.1 mass% of the powder, each mixture was mixed in a wet ball mill for 4 hours, then dried and granulated to obtain three types of mixed raw material powders. Each of the obtained mixed raw material powders was calcined in air at 1200°C for 3 hours to obtain three types of calcined bodies.

[0090] Each of the obtained calcined bodies was coarsely ground in a small mill to obtain coarsely ground powder. To ensure that the Co content z in the ferrite sintered magnet was 0.15, among the three types of coarsely ground powder obtained, the amount of Co was calculated based on 100 mass% of the coarsely ground powder with a z' (atomic ratio z' of the previously added material) of 0 at the time of weighing. ３ O ４ Add 1.40 mass% of the powder (added after the entire amount has been added), and Co is added to 100 mass% of the coarsely ground powder whose z' (atomic ratio z' of the previously added powder) at the time of weighing is 0.075. ３ O ４ 0.69 mass% of the powder was added (half added before, half added after). The coarsely ground powder with z' (atomic ratio z' of the pre-added powder) of 0.15 at the time of weighing contained Co ３ O ４ No powder was added (all added beforehand).

[0091] Furthermore, to the three types of coarsely ground powder obtained, the amounts of CaCO2 shown in Table 1 were added. ３Powder (amount added is in terms of CaO equivalent) and SiO ２ Six types of coarsely ground powders were prepared by adding powder, and each coarsely ground powder was finely ground for 21 hours in a wet ball mill using water as the dispersion medium to obtain six types of finely ground slurries. The average particle size of the obtained slurries was approximately 0.75 μm (measured by air permeability method using a powder specific surface area analyzer (Shimadzu SS-100)).

[0092] Each finely ground slurry obtained in the grinding process was molded at a pressure of approximately 2.4 MPa while applying a magnetic field of approximately 1 T using a parallel magnetic field molding machine (vertical magnetic field molding machine) in which the pressurizing direction and the magnetic field direction are parallel, while removing the dispersion medium, thereby obtaining six types of molded bodies.

[0093] The six types of molded bodies obtained were fired under the following firing conditions. Firing condition A involved increasing the temperature from 100°C to 1100°C at an average rate of 6.67°C / min while air was flowing at a flow rate of 10 L / min, then increasing the temperature from 1100°C to the firing temperature at a rate of 1°C / min, and firing for 1 hour at the firing temperatures shown in Table 1 (1210°C, 1220°C, 1230°C). After firing, the air flow rate was kept at 10 L / min, and the temperature was decreased from the firing temperature to 800°C at an average rate of 5°C / min, and then cooled to room temperature in the furnace. Under firing condition B, the temperature is raised from 100°C to the firing temperature at an average rate of 6.67°C / min while air is flowed at a rate of 10 L / min, and the firing is performed for 1 hour at the firing temperatures shown in Table 1 (1210°C, 1220°C, 1230°C). After firing, the material is cooled in the same manner as under firing condition A.

[0094] Of the 36 types of fired bodies (ferrite sintered magnets) obtained, B ｒ , H ｃＪ , H ｋ (95) / H ｃＪ and H ｋ (90) / H ｃＪ The measurement results are shown in Table 1. In Table 1, samples without an asterisk (*) next to the sample number (samples No. 13 to 36) are experimental examples based on the embodiments of this disclosure, while samples with an asterisk (*) next to the sample number (samples No. 1* to 12*) are experimental examples that do not satisfy the embodiments of this disclosure (reproduction experiments of the total pre-addition of the Co raw material powder described in Patent Document 1). As mentioned above, H ｋ (95) / HｃＪ This means that in the second quadrant of the J (magnetization magnitude) - H (magnetic field strength) curve, J is 0.95 J. ｒ The value of H at the position where the value is obtained is H ｋ H using ｋ / H ｃｊ H ｋ (90) / H ｃＪ This means that in the second quadrant of the J (magnetization magnitude) - H (magnetic field strength) curve, J is 0.90 J. ｒ The value of H at the position where the value is obtained is H ｋ H using ｋ / H ｃｊ (J ｒ This is remanent magnetization, J ｒ = B ｒ ). H ｋ (90) / H ｃＪ H ｃＪ , H ｋ (95) / H ｃＪ This represents a stricter indicator.

[0095] Furthermore, the method of adding Co (full amount added beforehand, half amount added beforehand / half amount added afterhand, full amount added afterhand) and the magnetic properties (B ｒ , H ｃＪ , H ｋ (95) / H ｃＪ and H ｋ (90) / H ｃＪ The relationship between the two is shown in Figures 1 to 8. Figure 1 shows the Co addition configuration and B under firing condition A. ｒ This figure shows the relationship between the two. Figure 2 shows the Co addition method and H under firing condition A. ｃＪ This figure shows the relationship between the addition of Co and H under firing condition A. Figure 3 shows the relationship between the addition of Co and H ｋ (95) / H ｃＪ This figure shows the relationship between the two. Figure 4 shows the Co addition method and H under firing condition A. ｋ (90) / H ｃＪ This figure shows the relationship between the two. Figure 5 shows the Co addition method and B under firing condition B. ｒ This figure shows the relationship between the two. Figure 6 shows the Co addition method and H under firing condition B. ｃＪ This figure shows the relationship between Co and H under firing condition B. Figure 7 shows the Co addition method and H ｋ (95) / H ｃＪ This figure shows the relationship between Co and H under firing condition B. Figure 8 shows the Co addition method and Hｋ (90) / H ｃＪ This diagram shows the relationship.

[0096] In Figures 1 to 8, the horizontal axis represents the Co addition method, and the vertical axis represents the magnetic properties. To facilitate comparison of magnetic properties based on the Co addition method under the same conditions (firing conditions, firing temperature, and CaO addition amount), each figure is divided into (A) to (F). The sample numbers at the top of each figure correspond, from left to right, to half pre-addition, half pre-addition / half post-addition, and full post-addition. For example, in Figure 1(A), sample No. 1 corresponds to full pre-addition, sample No. 13 corresponds to half pre-addition / half post-addition, and sample No. 25 corresponds to full post-addition. The correspondence is the same for the other figures. Furthermore, in each figure, the left side of the figure ((A) to (C)) shows the case when the amount of CaO added is 0.70 mass%, and the right side of the figure ((D) to (E)) shows the case when the amount of CaO added is 0.75 mass%. The upper part of the figure ((A), (D)) shows the case when the firing temperature is 1210°C, the middle part of the figure ((B), (E)) shows the case when the firing temperature is 1220°C, and the lower part of the figure ((C), (F)) shows the case when the firing temperature is 1230°C.

[0097] Furthermore, the atomic ratio (composition of the sintered magnet) in the sintered body (ferrite sintered magnet) after firing is based on the atomic ratio at the time of mixing, for example, the additive (H) added before the calcination process. ３ BO ３ The amount of additives such as, and the amount of Co added after the calcination process and before the molding process. ３ O ４ and sintering aid (CaCO3 ３ o SiO ２ The amount of additives (such as) can be considered and calculated, and the calculated value will be basically the same as the result of analyzing a ferrite sintered magnet with an ICP emission spectrometer (for example, Shimadzu ICPV-1017).

[0098]

[0099] As is clear from Table 1 and Figures 1 to 8, in samples No. 1* to 12* in which the entire amount of Co was added beforehand (experimental examples that do not satisfy the embodiments of this disclosure, reproduction experiments of the entire amount of Co raw material powder added beforehand as described in Patent Document 1), H ｋ (95) / H ｃＪ 86.0% or less, H ｋ(90) / H ｃＪ However, while the percentage is 92.8% or less, in samples No. 13-24, in which half of Co was added beforehand and half was added afterward, and in samples No. 25-36, in which the entire amount of Co was added afterward, except for samples No. 21 and 24, H ｋ (95) / H ｃＪ Over 86.0% of respondents reported a positive response rate, with the majority exceeding 90.0%. ｋ (90) / H ｃＪ Even looking at the data, with the exception of samples No. 21 and 24, the percentage exceeds 93%.

[0100] Furthermore, as is clear from Table 1 and Figures 1 to 8, samples No. 1* to 12* with all Co added beforehand, samples No. 13 to 24 with half Co added beforehand and half after, and samples No. 25 to 36 with all Co added afterwards are B ｒ and H ｃＪ These are almost equivalent. Thus, according to the embodiments of this disclosure, in a ferrite sintered magnet having the same components and composition as Patent Document 1, B ｒ and H ｃＪ While suppressing the decrease in H, even when the composition (amount of sintering aid added), firing temperature, firing conditions, etc. are changed, a stable high H is maintained. ｋ / H ｃｊ This makes it possible to provide ferrite sintered magnets that can achieve the desired result.

[0101] On the other hand, samples No. 21 and 24 were fired at a firing temperature of 1230°C, and under the same conditions, samples No. 19 and 22 were fired at a firing temperature of 1210°C, and samples No. 20 and 23 were fired at a firing temperature of 1220°C. ｒ Although H ｃｊ H has decreased slightly. ｋ (95) / H ｃＪ H has also decreased. However, compared to No. 9* and 12*, which have the same conditions except for the different method of Co addition (half Co added before / after and full Co added before) (see Figures 7(C) and (F)), H is clearly lower. ｋ / H ｃｊ The decrease in H is suppressed. Furthermore, in samples No. 33 and 36, where Co was added after the entire amount was added, even when the firing temperature was increased, H ｋ / H ｃｊ There is almost no decrease (see Figures 7(A) to (F)).

[0102] These trends are similar for samples other than those listed above. Table 2 rearranges the samples from Table 1 that were fired at a temperature of 1230°C, had the same manufacturing conditions other than the firing temperature, but differed in the method of Co addition (all Co added beforehand, half Co added beforehand / half added afterward, all Co added afterward), and for each, the H values ​​for the sample fired at 1210°C are shown. ｋ (95) / H ｃＪ The rate of decrease (decrease rate) and H for a sample fired at a temperature of 1220°C ｋ (95) / H ｃＪ This shows the rate of decrease (decrease).

[0103]

[0104] As shown in Table 2, the manufacturing conditions (atomic ratio z = 0.15, CaCO3) ３ Addition amount = 0.70 mass%, SiO ２ For samples No. 3*, 15, and 27, which had the same addition amount (0.966 mass%) and firing conditions (A), but differed in the form of Co addition, the H2 levels were different for samples fired at 1210°C and 1220°C when all Co was added beforehand. ｋ (95) / H ｃＪ The decrease rate is approximately 22%, but with half Co added before or after, the decrease rate is approximately 5%, and with all Co added after, the decrease rate is almost 0%. Samples No. 6*, 18, 30, No. 9*, 21, 33, No. 12*, 24, and 36 show similar trends. In particular, with all Co added after, H ｋ (95) / H ｃＪ The effect of suppressing the decrease is high, and the decrease rate is 3.2% or less regardless of the manufacturing conditions. As described above, according to the embodiment of the present disclosure, in a ferrite sintered magnet having the same components and composition as Patent Document 1, B ｒ Even when the firing temperature is increased for improvement, H ｋ / H ｃｊ This makes it possible to provide ferrite sintered magnets that can suppress the decrease in performance.

[0105] Experimental Example 2 For the ferrite sintered magnets of samples No. 1*, No. 3*, No. 25, and No. 27 from Experimental Example 1, 10 ferrite main phase particles with a core-shell structure and 10 ferrite main phase particles without a core-shell structure were selected in a specific field of view of the cross-section (c-plane) of each sample. The composition of the shell portion (see Table 3) and core portion (see Table 4) of the selected ferrite main phase particles with a core-shell structure, and the composition of the outer shell portion (see Table 5) and central portion (see Table 6) of the ferrite main phase particles without a core-shell structure were analyzed using EPMA (Electron Probe Microanalyzer, JEOL Ltd. JXA-8530F). The analysis results for each sample and their average values ​​are shown in Tables 3 to 6. Note that the analysis results for each analysis field are shown as measured values ​​to one decimal place, while the average value is calculated to two decimal places and then rounded to one decimal place.

[0106]

[0107]

[0108]

[0109]

[0110] Next, for sample No. 1*, based on the average values ​​in Tables 3 to 6 above, we calculated (s1-c1), which is the difference between the average content of each element in the shell portion (s1) and the average content of each element in the core portion (c1) of ferrite main phase particles having a core-shell structure, and (s2-c2), which is the difference between the average content of each element in the outer shell portion (s2) and the average content of each element in the central portion (c2) of ferrite main phase particles without a core-shell structure. Furthermore, we calculated the absolute value of the difference between (s1-c1) and (s2-c2), which is |(s1-c1)-(s2-c2)|. The results are shown in Table 7.

[0111]

[0112] Similarly to sample No. 1*, for sample No. 3*, sample No. 25, and sample No. 27, the average values ​​of the content of each element in the shell portion of ferrite main phase particles having a core-shell structure (s1), the average value of the content of each element in the core portion (c1), and the difference between the average values ​​(s1) and (c1) (s1-c1) were determined. For ferrite main phase particles without a core-shell structure, the average value of the content of each element in the outer shell portion (s2), the average value of the content of each element in the central portion (c2), and the difference between the average values ​​(s2) and (c2) (s2-c2) were also determined. Furthermore, the absolute value of the difference between (s1-c1) and (s2-c2), |(s1-c1)-(s2-c2)|, was calculated. The results are shown in Tables 8 to 10. Table 11 also shows the results of summarizing only the absolute values ​​of the difference between (s1-c1) and (s2-c2), which is |(s1-c1)-(s2-c2)|, in Tables 7 to 10. Note that the average values ​​(s1, c1, s2, c2), (s1-c1), (s2-c2), and |(s1-c1)-(s2-c2)| in Tables 7 to 10 are calculated to two decimal places and rounded to one decimal place. Therefore, for example, in the Si with core shell in Table 7, the value of (s1-c1) may not match (0.2-0.2=-0.1, while the value to the second decimal place is 0.16-0.21=-0.05).

[0113]

[0114]

[0115]

[0116]

[0117] As shown in Table 11, samples No. 25 and 27, which are ferrite sintered magnets of the present disclosure obtained by the method for manufacturing ferrite sintered magnets of the embodiment of the present disclosure, showed that in EPMA analysis of any cross-section, the average value La content in the shell portion of ferrite main phase particles having a core-shell structure was ｓ１ and the average value of La content in the core part ｃ１ The difference (La ｓ１－ La ｃ１) and the average value of La content in the outer shell of ferrite-dominant phase particles that do not have a core-shell structure ｓ２ and the average value of La content in the central part ｃ２ The difference (La ｓ２－ La ｃ２ The absolute value of the difference between (La) ｓ１－ La ｃ１ )-(La ｓ２－ La ｃ２ )| becomes 0.5 mass% or less.

[0118] On the other hand, samples No. 1* and 3*, which are ferrite sintered magnets obtained by pre-adding the entire amount of Co raw material powder according to Patent Document 1, are |(La ｓ１－ La ｃ１ )-(La ｓ２－ La ｃ２ )| exceeds 0.5 mass%. In other words, it is thought that the compositional distribution of La within the main phase particles becomes uniform by adding the raw material powder of Co afterwards. As a result, as shown in Table 1 of Experimental Example 1, H ｋ (95) / H ｃＪ 86% or less, H ｋ (90) / H ｃＪ It is less than 93%, B ｒ If the firing temperature is increased to improve performance (the firing temperature is raised from 1210°C to 1230°C), B ｒ H improves ｋ / H ｃｊ It decreases significantly. In contrast, in samples No. 25 and 27, H ｋ (95) / H ｃＪ over 92%, H ｋ (90) / H ｃＪ H is consistently high at over 95% ｋ / H ｃｊ B ｒ Even when the firing temperature is increased for improvement, H ｋ / H ｃｊ The decline is suppressed.

[0119] Furthermore, as is clear from Table 11, samples No. 1* and 3* are |(Co ｓ１－ Co ｃ１ ) - (Co ｓ２－ Coｃ２ While sample No. 25 exceeds 0.1 mass%, samples No. 25 and 27 are 0.1 mass or less. This suggests that the compositional distribution of Co within the main phase particles becomes more uniform due to the subsequent addition of the Co raw material powder.

[0120] Experimental Example 3 Three types of calcined bodies with different Co content prepared in Experimental Example 1 were subjected to X-ray diffraction measurements using an X-ray diffractometer (SmartLab, manufactured by Rigaku). Rietveld analysis was performed from the obtained diffraction patterns to determine the phase ratio of the main phase (M phase) and the La orthoferrite phase (L phase), the a-axis length, c-axis length, and c-axis length / a-axis length (c / a) of the M phase, and the lattice constant of the L phase. A Rigaku SmartLab Studio II Powder XRD was used for the Rietveld analysis. The results are shown in Table 12. Sample No. 101* is a calcined body for pre-addition of the entire amount of Co according to Patent Document 1, and samples No. 102 and 103 are calcined bodies for half-addition of Co before and half-addition of Co after addition, and calcined bodies for full-addition of Co after addition, respectively, according to embodiments of this disclosure.

[0121]

[0122] As shown in Table 12, the calcined body of sample No. 101* has a main phase ratio of 98.8 mass% and a La orthoferrite phase ratio of 1.2 mass%. In contrast, the calcined bodies of samples No. 102 and 103 have a main phase ratio of 98.4 mass% or less and a La orthoferrite phase ratio of 1.6 mass% or more. Furthermore, the calcined body of sample No. 101* has a main phase c-axis length of 22.9925 Å and a c-axis length / a-axis length (c / a) ratio of 3.9027. In contrast, the calcined bodies of samples No. 102 and 103 have a main phase c-axis length of 23.0000 Å or more and a c-axis length / a-axis length (c / a) ratio of 3.9030 or more.

[0123] For the calcined samples No. 101*, 102, and 103, the Curie temperature T of the magnetic phase including the main phase (M phase) was determined using a magnetic field thermogravimetric analyzer (magnetic field TG analyzer). ｃ The following measurements were taken. The measurement results are shown in Table 13. The measurements were taken at temperatures ranging from 50°C to 650°C and a heating rate of 10°C / min.

[0124]

[0125] As shown in Table 13, in the calcined sample No. 101*, only the Curie temperature of the main phase was confirmed. However, in the calcined samples No. 102 and 103, a different magnetic phase, clearly distinct from the main phase, was confirmed, which has a Curie temperature of 454°C or higher (magnetization disappears above 454°C or a magnetic phase transition occurs above 454°C). Based on the phase ratios shown in Table 12, this magnetic phase is thought to be a hexagonal magnetoplumbite (M-type) ferrite compound (second M phase) with a lower La and Co content than the main phase.

[0126] In a ferrite sintered magnet having the same components and composition as in Patent Document 1, B ｒ and H ｃＪ While suppressing the decline, maintain a stable high H ｋ / H ｃｊ The ferrite sintered magnet obtained by the embodiment of this disclosure can be suitably used in various motors and the like.

Claims

1. General formula showing the atomic ratios of metallic elements Ca, R, A, Fe, and Co (where R is at least one rare earth element and must contain La, and A is Sr and / or Ba): Ca １－ｘ－ｙ R ｘ A ｙ Fe ２ｎ’－ｚ’ Co ｚ’ The process includes: a raw material powder mixing step to obtain a mixed raw material powder by mixing raw material powders that satisfy the following conditions: 0.30 ≤ 1 - x - y ≤ 0.55, 0.25 ≤ x ≤ 0.40, 0.15 ≤ y ≤ 0.40, 1 - x - y > y, 0 ≤ z' < 0.18, and 8.5 ≤ 2n' - z' < 11.0; a calcination step to obtain a calcined body by calcining the mixed raw material powder; a grinding step to obtain a calcined body powder by grinding the calcined body; a molding step to obtain a molded body by molding the calcined body powder; and a firing step to obtain a sintered body by firing the molded body. A method for manufacturing a ferrite sintered magnet, characterized by adding raw material powder of Co to the calcined body or the powder of the calcined body after the calcination step and before the molding step, such that the total Co content z in the ferrite sintered magnet satisfies 0 < z ≤ 0.18 and z' < z.

2. The H of the ferrite sintered magnet ｋ (95) / H ｃＪ is more than 86%, and the method for manufacturing a ferrite sintered magnet according to claim 1 is characterized in that. However, H ｋ (95) is the value of H at the position where J becomes 0.95 × J in the second quadrant of the J-H curve (J is the magnitude of magnetization, H is the strength of the magnetic field, and J ｒ is the residual magnetization). ｒ ​ 3. H of the ferrite sintered magnet ｋ (95) / H ｃＪ A method for manufacturing a ferrite sintered magnet according to claim 2, wherein the content is 90% or more.

4. The method for manufacturing a ferrite sintered magnet according to claim 1, wherein 1-x-y is 0.30 ≤ 1-x-y ≤ 0.

45.

5. The method for manufacturing a ferrite sintered magnet according to claim 1, wherein x is 0.30 ≤ x ≤ 0.

35.

6. The method for manufacturing a ferrite sintered magnet according to claim 1, wherein y is 0.20 ≤ y ≤ 0.

30.

7. The method for manufacturing a ferrite sintered magnet according to claim 1, wherein z' and z are z' / z ≤ 0.

5.

8. The method for manufacturing a ferrite sintered magnet according to claim 7, wherein z is 0 < z ≤ 0.

15.

9. The method for manufacturing a ferrite sintered magnet according to claim 1, wherein 2n'-z' is 9.0 ≤ 2n'-z' ≤ 10.

0.

10. After the calcination process and before the molding process, 1.5 mass% or less (excluding 0 mass%) of SiO per 100 mass% of the calcined body or the powder of the calcined body is added. ２ A method for manufacturing a ferrite sintered magnet according to claim 1, further comprising the step of adding a substance.

11. After the calcination process and before the molding process, CaCO3 is added in an amount of 1.5 mass% or less (excluding 0 mass%) in terms of CaO, relative to 100 mass% of the calcined body or the powder of the calcined body. ３ A method for manufacturing a ferrite sintered magnet according to claim 1, further comprising the step of adding a substance.

12. A ferrite sintered magnet containing a plurality of first ferrite main phase particles having a core-shell structure and a plurality of second ferrite main phase particles not having a core-shell structure, wherein in EPMA analysis of any cross-section of the ferrite sintered magnet, the average value of the La content in the shell portion of the plurality of first ferrite main phase particles (La ｓ１ ) and the average value of the La content in the core (La ｃ１ The difference between (La ｓ１－ La ｃ１ ) and the average value of the La content in the outer shell of the plurality of second ferrite main phase particles (La ｓ２ ) and the average value of La content in the center (La ｃ２ The difference between (La ｓ２－ La ｃ２ When that is the case, the above (La ｓ１－ La ｃ１ ) and (La ｓ２－ La ｃ２ The absolute value of the difference between (La) ｓ１－ La ｃ１ )-(La ｓ２－ La ｃ２ A ferrite sintered magnet in which the | is 0.5 mass% or less.

13. The average value of the Co content in the shell portion of the plurality of first ferrite main phase particles (Co ｓ１ ) and the average value of the Co content in the core (Co ｃ１ The difference between (Co ｓ１－ Co ｃ１ ) and the average value of the Co content in the outer shell of the plurality of second ferrite main phase particles (Co ｓ２ ) and the average Co content in the center (Co ｃ２ The difference between (Co ｓ２－ Co ｃ２ ) When this is the case, the above (Co ｓ１－ Co ｃ１ ) and (Co ｓ２－ Co ｃ２ The absolute value of the difference between (Co) and (Co) ｓ１－ Co ｃ１ ) - (Co ｓ２－ Co ｃ２ The ferrite sintered magnet according to claim 12, wherein the | is 0.1 mass% or less.

14. General formula showing the atomic ratios of metallic elements Ca, R, A, Fe, and Co (where R is at least one rare earth element and must contain La, and A is Sr and / or Ba): Ca １－ｘ－ｙ R ｘ A ｙ Fe ２ｎ－ｚ Co ｚ The ferrite sintered magnet according to claim 12 or 13, wherein x, y and z, and n (where 2n is a molar ratio and is expressed as 2n = (Fe + Co) / (Ca + R + A)) satisfy 0.30 ≤ 1 - x - y ≤ 0.55, 0.25 ≤ x ≤ 0.40, 0.15 ≤ y ≤ 0.40, 1 - x - y > y, 0 < z ≤ 0.18, and 8.5 ≤ 2n - z < 11.

0.

15. H ｋ (95) / H ｃＪ A ferrite sintered magnet according to claim 14, wherein H is more than 86%. ｋ (95) is the second quadrant of the J-H curve, where J is 0.95 × J ｒ This is the value of H at the position where the value is obtained (J is the magnitude of magnetization, H is the strength of the magnetic field, J ｒ (This refers to remanent magnetization.) 16. H ｋ (95) / H ｃＪ The ferrite sintered magnet according to claim 15, wherein the content is 90% or more.

17. The ferrite sintered magnet according to claim 14, wherein 1-x-y is 0.30 ≤ 1-x-y ≤ 0.

50.

18. The ferrite sintered magnet according to claim 14, wherein x is 0.30 ≤ x ≤ 0.

35.

19. The ferrite sintered magnet according to claim 14, wherein y is 0.20 ≤ y ≤ 0.

30.

20. The ferrite sintered magnet according to claim 14, wherein z is 0 < z ≤ 0.

15.

21. The ferrite sintered magnet according to claim 14, wherein 2n-z is 8.5 ≤ 2n-z ≤ 10.

0.

22. General formula showing the atomic ratios of metallic elements Ca, R, A, Fe, and Co (where R is at least one rare earth element and must contain La, and A is Sr and / or Ba): Ca １－ｘ－ｙ R ｘ A ｙ Fe ２ｎ’－ｚ’ Co ｚ’ In this ferrite calcined body, x, y, z', and n' (where 2n' is a molar ratio and is expressed as 2n' = (Fe + Co) / (Ca + R + A)) satisfy the following conditions: 0.30 ≤ 1 - x - y ≤ 0.55, 0.25 ≤ x ≤ 0.40, 0.15 ≤ y ≤ 0.40, 1 - x - y > y, 0 ≤ z' < 0.18, and 8.5 ≤ 2n' - z' < 11.0, and containing 1.6 mass% or more of La orthoferrite phase.

23. The ferrite calcined body according to claim 22, wherein z' is 0 ≤ z' ≤ 0.

09.

24. The ferrite calcined body according to claim 22, which contains ferrite main phase particles having a c-axis length of 23.0000 Å or more.

25. The ferrite calcined body according to claim 22, which contains ferrite main phase particles having a c-axis length / a-axis length of 3.9030 or more.

26. The ferrite calcined body according to claim 22, which contains a magnetic phase in which magnetization disappears or a magnetic phase transition occurs at 454°C or higher.

27. The ferrite calcined body according to claim 22, wherein the content of ferrite main phase particles is 98.4 mass% or less.

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