JPH07315844A - Production of ferrite powder - Google Patents

Abstract

PURPOSE:To obtain high-purity ferrite powder at low cost by adding an aqueous NH4OH solution at a specific concentration to a solution containing a ferrous metal salt and a salt of a metal other than the Fe constituting the final ferrite to produce a precipitate. CONSTITUTION:An aqueous NH4OH solution at a concentration of 0.05-5mol/l is added to an aqueous metal salt solution containing (A) a ferrous metal salt and (B) a second metal salt, a sulfate, chloride or nitrate of at least one kind of metal selected from Sr, Ba, Pb, Zn, Ni, Mn, Co, Cu, Mg, Y, Al, Bi and Ti to produce a precipitate. The above-mentioned addition is conducted in the presence of an enough amount of oxygen to convert the Fe<2+> into Fe<3+>. The precipitate is then taken after filtration and heat treated at 500-1000 deg.C for 0.1-10hr either directly or after dried to obtain the objective ferrite powder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing ferrite powder by a wet method.

[0002]

2. Description of the Related Art Conventionally, Ni--Zn ferrite and Mn--Z are used.
In order to obtain powder of ferrite such as n, powders of oxides and carbonates of constituent metal elements are mixed, and the mixture is mixed with 800 to 1
Although a dry method by powder metallurgy that performs heat treatment at 000 ° C. is performed, at present, heat treatment is often performed at a high temperature of 1000 ° C. or higher, and the ferrite powder obtained by this method is a material for electronic parts, For example, it is used as a raw material for a ferrite sintered body (magnetic porcelain) as a magnetic material. Since the ferrite powder obtained by this dry method is obtained through the steps of mixing the raw material powders and the step of performing heat treatment, unnecessary substances are easily mixed in these steps,
The distribution of the metal element in the crystal grains becomes non-uniform, which not only adversely affects the electromagnetic characteristics and performance of the obtained porcelain, but also the impurities mixed therein impede the sintering during the production of the porcelain. Moreover, when heat-treated at a high temperature of 1000 ° C. or higher,
Since the lumps generated by the heat treatment are crushed into powder,
The shape and particle size of the powder particles become non-uniform, and when the powder is observed with an electron microscope, the average particle size is 0.1 μm to 10 μm.
m, and the particle size distribution is wide. For this reason, even if the obtained ferrite powder is used for molding, the powder is not uniformly filled, and densification occurs in the molded body. As a result, when the molded body is sintered to manufacture a porcelain, voids remain inside the porcelain and the size of the crystal particles in the porcelain becomes uneven. Further, heat treatment at a high temperature not only causes non-uniformity of particles but also causes particles to coagulate. Therefore, voids exist unevenly in the molded body created using the obtained ferrite powder, density variation in the structure also occurs, and the porcelain obtained by sintering the molded body has many voids. , Its dimension control becomes difficult. Furthermore, a furnace for heat treatment at high temperature is required, and the equipment is expensive.

[0003]

Since the ferrite powder produced by such a dry method cannot meet the demands for high coercive force of magnetic powders due to the recent demands for miniaturization and high performance of electronic parts, impurities of impurities cannot be satisfied. Is less mixed, the composition in the crystal grains is uniform, the grain size is small, it is a ferrite powder with a narrow grain size distribution width, also when obtaining a porcelain using this, does not hinder its sintering, There is a demand for a ferrite powder that does not easily form voids in the obtained porcelain, is easy to control in size, and can be obtained without requiring a furnace.
A method of obtaining ferrite powder by a wet method is being studied as one that satisfies these demands. This wet method is generally one in which an alkaline metal hydroxide solution of an alkali metal is added to an ionic solution of a constituent metal of ferrite to coprecipitate these metals as hydroxides, and the precipitate is dried to obtain a ferrite powder. is there. However, the ferrite powder obtained by this wet method is unavoidably non-uniform in composition and often deviates from the desired composition, and therefore it is difficult to produce a powder having a stable composition. A ferrite sintered body obtained by using a ferrite powder whose composition is not stable does not have stable electromagnetic properties and is difficult to use. Also,
Since the alkali metal alkali hydroxide is used as the precipitant,
Even if the alkali metal hydroxide is removed by washing when the metal hydroxide is co-precipitated, it is inevitable to remain. In particular, when synthesizing a ferrite powder of a system composed of two or more components, a composition shift is likely to occur. Therefore, in order to prevent this, the reaction is often performed under highly alkaline conditions, and the residual amount of alkali metal further increases. When applying the ferrite sintered body to a thin film, the uniformity of the composition is strictly required, and when plating is applied to the molded body made of the ferrite sintered body, the plating should be performed. Since it is required not to interfere, it is not preferable that alkali metal remains in the ferrite powder, and development of a method for producing ferrite powder by a wet method that does not use alkali hydroxide of alkali metal is desired. As a solution to this problem, a synthetic method for obtaining high-purity and high-quality ferrite powder from a metal alkoxide has been studied, but it has not been put into practical use because the metal alkoxide is expensive.

A first object of the present invention is to provide a method for producing a ferrite powder in which impurities are unlikely to be mixed and the composition does not shift. A second object of the present invention is to provide a method for producing a ferrite powder that does not hinder the sintering due to the inclusion of impurities or adversely affect the electromagnetic characteristics. A third object of the present invention is to provide a method for producing high-purity ferrite powder in which no alkali metal remains. A fourth object of the present invention is to provide a method for producing a ferrite powder having no nonuniform composition. A fifth object of the present invention is to provide a method for producing a single-phase high-quality ferrite powder having no crystal phase heterogeneity. A sixth object of the present invention is to provide a method for producing ferrite powder having a small particle size. A seventh object of the present invention is to provide a method for producing a ferrite powder having a narrow particle size distribution. An eighth object of the present invention is to provide a method for producing a ferrite powder that is free from coagulation, is uniformly filled with powder when a molded body is obtained, and is less likely to cause densification in its structure. A ninth object of the present invention is to provide a method for producing a ferrite powder having good crystallinity when fired. Tenth of the present invention
It is an object of the present invention to provide a method for producing a ferrite powder, which has a high degree of crystallinity when fired and can obtain a sintered body having a uniform crystal grain size. An eleventh object of the present invention is to provide a method for producing a ferrite powder in which there are few voids when fired and the size control of the sintered body is easy. A twelfth object of the present invention is to provide a method for producing a ferrite powder which realizes the above tenth object with high productivity. A thirteenth object of the present invention is to provide a method for producing a ferrite powder that can be obtained without using a furnace. A fourteenth object of the present invention is to provide a method for producing a ferrite powder that can be obtained at a low cost.

[0005]

In order to solve the above problems, the present invention provides (1), Sr, Ba, Pb, Zn, N.
i is a metal salt of Fe of the group consisting of i, Mn, Co, Cu, Mg, Y, Al, Bi, Ti and Fe and at least one other metal, and is a divalent Fe metal with respect to Fe. A step of obtaining a metal salt aqueous solution containing a metal salt which is at least one selected from the group consisting of a sulfate, a chloride and a nitrate, wherein the respective metal salt is 0.05 to 5 The present invention provides a method for producing a ferrite powder, which has a step of forming a precipitate by adding a 0.04 mol / l NH ₄ OH solution.

Further, (2), Ba, Zn, Mn, Ni,
Y is a metal salt of Fe in the group consisting of Cu, Fe and at least one other metal, and is a divalent Fe metal salt for Fe, wherein the metal salt is a sulfate salt, A step of obtaining an aqueous metal salt solution containing a metal salt which is at least one kind of a group consisting of chloride and nitrate, and 0.05 to 5.0 mol / l of N in the aqueous metal salt solution.
A method for producing a ferrite powder, comprising the step of forming a precipitate by adding a H ₄ OH solution, (3), NH ₄ O
The method for producing a ferrite powder according to (1) or (2) above, wherein the concentration of the H solution is 0.1 to 3.0 mol / l.
(4) Fe ²⁺ of a divalent Fe metal salt is calculated as Fe ³⁺ , and an NH ₄ OH solution is added in an amount of more than 0.8 equivalents and less than 3 equivalents to the metal ion in the aqueous metal salt solution. ) To (3), the method for producing a ferrite powder according to any one of (5) to (5), wherein Fe ²⁺ of a divalent Fe metal salt is calculated as Fe ³⁺ , and NH is added to the metal ion in the metal salt aqueous solution. ₄ O
The method for producing a ferrite powder according to any one of (1) to (3) above, wherein the H solution is added in an amount of more than 0.8 equivalents and less than 2.5 equivalents, (6) Fe ^{2+ of} a metal salt of divalent Fe. To F
Calculated as e ^{3+ and} adding 0.8 to 1.2 equivalents of NH ₄ OH solution to the metal ions in the aqueous metal salt solution (1)
(7) The method for producing a ferrite powder according to any one of (3) to (3), wherein (7) Fe ²⁺ of the metal salt of divalent Fe is calculated as Fe ³⁺ , and NH _{4 is} added to the metal ion in the metal salt aqueous solution.
A method for producing a ferrite powder according to any one of (1) to (3) above, wherein an OH solution is added in an amount of 1.0 equivalent, (8),
The operation of adding NH ₄ OH solution to the metal salt aqueous solution is divalent F
The method for producing a ferrite powder according to any one of the above (1) to (3) or (6) or (7), which is carried out in the presence of sufficient oxygen so that Fe ²⁺ of the metal salt of e becomes Fe ³⁺ . (8),
The step of forming a precipitate by adding an NH ₄ OH solution to an aqueous metal salt solution includes the step of stirring a mixed solution of the NH ₄ OH solution added to the aqueous metal salt solution, or (1) to (3) above, or (6) to the method for producing a ferrite powder according to any one of (8), (10), the method for producing a ferrite powder according to (9), wherein the stirring is 300 to 3000 revolutions per minute, (11), Stirring is 500 ~ per minute
The method of manufacturing a ferrite powder according to claim 9, which is a 2000 rotation, (12), to produce a precipitate by the addition of NH ₄ OH solution to the metal salt solution is added NH ₄ OH solution to the metal salt solution The method for producing a ferrite powder according to any one of the above (1) to (3) or (6) to (11), which comprises the step of heating the mixed solution under normal pressure, (13), and heating is 0. 3-10 at -40 ° C
The method for producing a ferrite powder according to (12) above, which is time, (14), the method for producing a ferrite powder according to (12), wherein heating is at 10 to 30 ° C. for 3 to 7 hours.
(15) The method for producing a ferrite powder according to any one of (1) to (3) or (6) to (14), which comprises a step of aging the precipitate, (16), and the aging is 80 to The method for producing a ferrite powder according to claim 15, which is performed at 100 ° C, (17), and aging is performed at 80 to 90 ° C for 1 to 5 ° C.
A method for producing a ferrite powder according to (15)
(18), NH ₄ to produce a precipitate by the addition of NH ₄ OH solution to the metal salt aqueous solution to the metal salt solution
The mixed solution containing the OH solution is heated to 60 ° C or higher in the presence of oxygen to 100
(4) The method for producing a ferrite powder according to the above (4) or (5), which comprises a step of heating to ℃ or less, (19), a mixed solution of an NH ₄ OH solution added to an aqueous metal salt solution in the presence of oxygen 60
The method for producing a ferrite powder according to the above (18), wherein the step of heating the mixed liquid to a gas having an oxygen content of 0.1% or more is performed in the step of heating the mixture to 100 ° C. or higher, (2).
0), to produce a precipitate by the addition of NH ₄ OH solution to the metal salt solution is NH in the metal salt solution ₄ OH
The mixed solution containing the solution is heated to 100 ° C or higher and 300 ° C in the presence of oxygen
The method for producing a ferrite powder according to the above (4) or (5), which comprises the step of heating below, (21), wherein a mixed solution obtained by adding an NH ₄ OH solution to an aqueous metal salt solution is used in the presence of oxygen.
The method for producing ferrite powder according to the above (20), wherein the step of heating to 3,000 to 300 ° C. includes the step of adding an oxidizing agent that generates oxygen and then heating, (22), filtering the liquid containing the precipitate. (1) to (21) having steps
(23), the step of filtering a liquid containing a precipitate, and the step of subjecting the filtered precipitate to a heat treatment, either directly or after drying, (1) to (3) ) Or (6) to (17), the method for producing a ferrite powder, (24), the heat treatment is 5
The above (2) which is 0.1 to 10 hours at 00 ° C to 1000 ° C.
3) Method for producing ferrite powder, (25), Heat treatment is performed at 700 ° C. to 900 ° C. for 1 to 5 hours, Method for producing ferrite powder in (24), (26), Precipitate is produced from the mixed solution. The ferrite powder according to any one of the above (1) to (3) or (6) to (17), which has a step of spray-drying a mixed solution containing the precipitate and a step of subjecting the obtained powder to a heat treatment. (27), the heat treatment is performed at 500 ° C. to 1000 ° C. for 0.1 to 10 hours, and the heat treatment is performed at 700 ° C. to 900 ° C. for 1 to 5 (28). It is time above (2
6) A method for producing a ferrite powder according to 6) is provided.

In the above (1) and (2), "the step of forming a precipitate by adding a 0.05 to 5.0 mol / l NH ₄ OH solution to an aqueous solution of a metal salt" is performed. A step of forming a precipitate by changing Fe ²⁺ to Fe ³⁺ from a mixed solution added with an NH ₄ OH solution of 0.05 to 5.0 mol / l can also be performed. In the present invention, “Sr, Ba, Pb, Zn, Ni, Mn, C
o is a metal salt of Fe in the group consisting of Cu, Mg, Y, Al, Bi, Ti and Fe and at least one other metal, and is a divalent Fe metal salt. The metal salt aqueous solution containing a metal salt in which each metal salt is at least one selected from the group consisting of sulfates, chlorides and nitrates "means divalent Fe according to the composition of the ferrite powder to be obtained. And one or more of the above-mentioned sulfates, chlorides and nitrates, and one or more of the above-mentioned other one or two or more metal sulfates, chlorides and nitrates. A metal salt solution containing a metal salt consisting of a combination, specifically a desired ferrite,
For example, Fe, Ni-Zn, Ni-Cu-Zn, Mn-
Zn, Mg-Cu-Zn, Co-Cu-Zn, Mn-M
g-Zn, Ni-Cu-Co, Ba-Sr, Ba-P
The above metal salts are used in combination according to the respective metal constituent elements of b, Sr-Pb, and Y-Al. In addition, the metal salt solution containing a metal salt may contain a salt of a trace amount of elements other than the above (including trivalent Fe) and other compounds within a range that does not substantially interfere. Of the above metal salts, Fe has been described above, but as for the other metals, salts of all ionic valences that each metal can take can be used. In this case, each salt may be one kind or two or more kinds.

The concentration of NH ₄ OH (ammonia water (NH ₃ + H ₂ O)) added to the above metal salt solution is 0.05 to
5.0 mol / l is preferable, and 0.1 to 0.1 is more preferable.
It is 3.0 mol / l. If it is less than 0.05 mol / l, a precipitate, which is a reaction product of NH ₄ OH of the metal salt solution, is less likely to occur, and if it is more than 5.0 mol / l, the metal ion of the metal salt solution forms an ammonium complex. Since it does not precipitate, the composition cannot be controlled, and the composition of the finally obtained ferrite powder deviates. An economically most suitable concentration that does not cause compositional deviation of the ferrite powder is more preferably 0.1 to 3.0 mol / l. N
When the concentration of H ₄ OH is appropriate as described above, by adding it little by little and causing precipitation sequentially,
Although after nearly compounds of all metals was precipitated possible so as not to re-dissolve the precipitate even when many amount of NH ₄ OH, the amount of NH ₄ OH added when added particularly at a time, the metal 0.8-1. With respect to the metal ion of the salt solution.
It is more preferable that the amount is 2 equivalents, particularly 1.0 equivalent. If the amount is less than this range, a precipitate, which is a reaction product of the metal salt solution with NH ₄ OH, is less likely to occur. It is effective even in the case of many less than 3 equivalents, and particularly these expanded ranges are also preferable by selecting conditions such as reaction temperature as described later.
It can be used in a range of more than 0.8 equivalents and less than 3 equivalents, preferably more than 0.8 equivalents and less than 2.5 equivalents, but if the number of equivalents is too large, compositional deviation occurs in the ferrite powder obtained as above. Sometimes.

In order to prevent metal ions from precipitating by forming an ammonium complex, which is a major cause of compositional deviation, the metal salt solution contains a divalent Fe metal salt, and Fe ^{2+ is added.} the While causing the precipitate, in the process of changing the Fe ^3+, is Fe ²⁺ in order that Fe
Under the oxidizing conditions for ³⁺ , for example, sufficient oxygen must be present. Specifically, for example, oxygen should be present in at least one of the mixed solution of this metal salt solution and NH ₄ OH and its atmosphere. Is preferable because it is a simple method. By doing so, the divalent iron ion Fe ²⁺ is easily changed to the trivalent iron ion Fe ³⁺ by the ambient oxygen, and the trivalent iron ion Fe ³⁺ is generated when the hydroxide is generated. , It gelates and incorporates other metal hydroxides and ammonium complexes of other metals into the gel, so that metal atoms that do not precipitate can be incorporated into the gel to form a precipitate, so that it is finally obtained. It is possible to suppress the composition deviation of the ferrite powder to be produced. The concentration of NH ₄ OH is important from this point as well. In this case, the metal salt of Fe is trivalent F.
When the metal salt of e is used as the raw material, the trivalent iron ion Fe ³⁺ is as much as the divalent iron ion Fe ²⁺ in the above-mentioned NH ₄ OH concentration p.
Since the solubility in the H range is not large, other metal ions may rapidly gel before forming a complex or a hydroxide, and there is a risk of causing a composition shift of the finally obtained ferrite powder. , That control is difficult. However, a metal salt of trivalent Fe can be used together with the above metal salt of divalent Fe in a range that does not cause any trouble. The presence of oxygen in at least one of the mixed solution of the metal salt solution and NH ₄ OH and the atmosphere thereof means that the mixed solution is agitated as described later, and particularly oxygen is taken in at the time of high speed agitation. Or a gas-liquid contact method in which an oxygen-containing gas is blown into the mixed solution, or both are used together, and in order to change Fe ²⁺ to Fe ³⁺ There are other oxidizing agents such as hydrogen peroxide, ozone, chlorine, and electrochemical methods. In this case, the atmosphere and the oxygen-containing gas may be either oxygen, a mixed gas of oxygen and an inert gas, or air. Thus, the reaction between the metal salt solution containing the above-mentioned metal salt of divalent Fe and NH ₄ OH is carried out in an oxygen-containing atmosphere in the presence of dissolved oxygen in the solution to oxidize Fe ²⁺ to Fe ^3+. However, if the reaction proceeds, Fe ²⁺ can be calculated as Fe ³⁺ , so NH ₄ OH
The amount of can be an amount commensurate with Fe ³⁺ . On this occasion,
When the reaction is carried out in air, the production equipment can be simplified as compared with the dry method.

In order to eliminate the composition deviation of the finally obtained ferrite powder and the nonuniformity of the composition of the particles, NH
_{When the} amount of ₄ OH added is 0.8 to 1.2 equivalents with respect to the metal ions of the metal salt solution, N 2 and the metal salt solution are added.
It is preferable to carry out the reaction by stirring the mixed solution of H ₄ OH, especially at high speed. By this high-speed stirring, it is possible to suppress the nucleus growth of the hydroxide crystal of the metal ion having a low solubility in the pH range of the NH ₄ OH concentration in the mixed solution. By this high-speed stirring, the composition deviation can be suppressed within 0.001 mol ratio, for example. The high-speed stirring speed is preferably 300 rpm (revolutions per minute) or more, more preferably 500 rpm or more. 300r
If it is slower than pm, the ferrite powder obtained through the heat treatment to be described later does not have, for example, a spinel single phase, and a different phase of hematite occurs to deteriorate the electromagnetic properties such as coercive force. 3000
If it is higher than rpm, the scale of the reaction tank cannot be increased,
Make productivity worse. The most suitable rotation speed of stirring is 3000 rpm or less, and more preferably 2000 rpm or less, in which the ferrite powder finally obtained does not have a heterogeneous phase, compositional deviation does not occur, and productivity is not reduced.

In order to prevent the composition of the ferrite powder obtained by the heat treatment described below from changing and the crystal phase to be a single phase of the spinel phase, the reaction time for causing the reaction is NH
_{When the} amount of ₄ OH added is 0.8 to 1.2 equivalents with respect to the metal ions of the metal salt solution, 3 hours or more is preferable, and if shorter than 3 hours, a different phase is likely to occur and a composition shift will occur. easy. Even if the reaction time is too long, the crystallinity of the reaction product is not improved by the heat treatment described below, and therefore the reaction time is preferably within 10 hours from the viewpoint of productivity.
For example, the reaction time is most suitable for 5 to 7 hours in consideration of the productivity for obtaining a single-phase ferrite powder such as a spinel single phase. The reaction may be carried out under heating, 0-40 ° C
In the case of, the reaction time is preferably 3 to 10 hours, and in the case of 10 to 30 ° C, the reaction time is preferably 3 to 7 hours. Reaction temperature 60 ℃
When the temperature is 100 ° C or higher and higher than 100 ° C, 30
The temperature may be 0 ° C. or lower, and in the former case, gas-liquid contact (such as a countercurrent contact device using a wetting wall or a filler) by blowing a gas having an oxygen content of 0.1% (volume%) or more. It is more preferable that the reaction is carried out in the presence of an oxidizing agent such as hydrogen peroxide, particularly an oxidizing agent that generates oxygen. In each case, the reaction time is preferably 3 to 10 hours. In these cases, it is preferable even if the amount of NH ₄ OH added is more than 0.8 and less than 3 equivalents with respect to the metal ions of the metal salt solution. When the amount of NH ₄ OH added is 0.8 to 1.2 equivalents with respect to the metal ions of the metal salt solution, the crystallinity of the obtained reaction product is crystallized by the firing step described below. In order to improve the temperature, it is preferable to carry out aging after the reaction, but the temperature is preferably 100 ° C or lower from the viewpoint of simplifying the production equipment, but 80 ° C or higher in order to improve the crystallinity. It is preferable to heat to. The most suitable aging temperature is 80 to 90 ° C. The aging time is preferably 1 hour or more for obtaining the ferrite powder having sufficient crystallinity, but it is preferably 3 hours or less in consideration of productivity.

In order to separate the obtained reaction product from the liquid containing it, the liquid is filtered with a filter press or the like,
It is sufficient to filter out the precipitate of the reaction product.
When the reaction temperature is 60 ° C or higher and 100 ° C or lower, or when the reaction temperature is higher than 100 ° C and lower than 300 ° C, the precipitate may be simply air-dried or heat-dried. The subsequent heat treatment may be carried out as it is, but it is also preferable to air-dry or heat-dry. The precipitate separated in this way is amorphous, especially in the latter case, and therefore needs to be crystallized by heat treatment. However, heat treatment of the powder after drying is performed at 500 ° C. to 10 ° C. in consideration of productivity.
The heating is preferably performed at 00 ° C. for 0.1 hours to 10 hours, more preferably 700 ° C. to 900 ° C. for 1 hour to 5 hours. Further, the drying may be spray drying in which a liquid containing the precipitate of the reaction product is sprayed, and the drying is preferably 500 ° C. or lower in consideration of production facilities and the like.
An anion annium salt of the used metal salt adheres to the obtained powder, and the powder is dried at 500 ° C to 1000 ° C for 0.1 hours to 10 hours, preferably 700 ° C to 900 ° C.
The annium salt can be sufficiently volatilized and removed by heat treatment for 1 to 5 hours. The advantage of performing spray-drying is that the powder of the dried product is spherical and therefore is easy to handle and the subsequent treatment is easy.

The ferrite powder finally obtained in this manner has no agglomeration between particles and has an average particle size of 0.5.
It can be controlled to be less than or equal to μm, for example, 0.05 μm to 0.5 μm, the particle size is small, and the distribution width is ± 20.
It can be narrowed within%. In particular, the particle size can be made smaller and the distribution can be made narrower than the ferrite powder obtained by the dry method. Since a fine powder having a small particle size is obtained in this way, for example, a molded body molded for a specific purpose such as a core is uniformly filled with the powder, and its structure is less likely to be dense or dense. Porcelain), the crystal grain size is small and uniform, and the variation in sparseness and density is small, so the mechanical strength is high, it is difficult to crack, there are few voids, and size control is easy, The sintering temperature is lower than that of the ferrite powder obtained by the ordinary powder metallurgy method, and the sintering can be performed even at 900 ° C. or lower. Also,
Since NH ₄ OH was used as a precipitant for the metal salt solution and no alkali metal hydroxide was used, the purity of the finally obtained ferrite powder is high. Further, the coercive force, which is important as the magnetic properties of the magnetic powder, takes a maximum value in the process of decreasing the grain size, and then decreases, and the grain size showing the maximum coercive force depends on the ferrite composition,
As described above, since the average particle diameter of the finally obtained ferrite powder can be controlled to 0.5 μm or less, the ferrite powder can be manufactured so that the coercive force is maximized by controlling the ferrite composition.

Since the ferrite powder according to the present invention can be fired at a low temperature as described above, it is effective as a low temperature firing material for ceramics. For example, a magnetic material using a magnetic material such as a laminated inductor or other laminated LC parts. The circuit pattern is Ag, Ag-Pd, C in the manufacture of parts.
When a film made of a conductor material having a relatively low melting point such as u is formed, the unsintered material in the base portion and the circuit pattern portion thereof can be simultaneously sintered. Further, when ceramics are used, since the crystal grains are fine and uniform, it is possible to produce ferrite cores, ferrite magnets, high-frequency elements, etc. having excellent magnetic properties such as coercive force. In addition, since it exhibits high-performance magnetic properties, it can be applied to magnetic recording media and magnetic fluids that use not only iron oxide magnetic powder but also metal magnetic powder, and because it has excellent dispersibility in resin solutions, it can be used in colloidal form. It is also possible to form a thin film by coating, and it is also promising as a magnetic thin film.

[0015]

The present dry method has a step of mixing compounds of constituent metal elements, a heat treatment step for obtaining a desired crystal phase, and a crushing step of sizing the heat-treated powder, and impurities are mixed in these steps. However, by unifying these steps by the wet method, the inclusion of impurities can be prevented, and since the high temperature heat treatment is not necessary, the particle aggregation can be reduced. In addition, a constant concentration of NH ₄ OH is used as an alkali that causes a reaction to produce a precipitate of a metal compound from a metal salt solution, and a divalent F 2 is added to a Fe metal salt.
Since the metal salt of e was used to cause the precipitation of the metal compound by changing Fe ²⁺ to Fe ³⁺ , the metal ion of the metal salt solution does not form a precipitate by forming an ammonium complex. Can be suppressed and the precipitate can be easily generated, so that the composition deviation of the ferrite powder obtained through the subsequent steps can be made difficult to occur. This composition deviation can be further improved by selecting the reaction temperature, the oxidation condition, the high speed stirring, and the condition of the equivalent ratio to the metal ion. In addition, high-speed stirring when causing precipitation can even out the composition of the particles and prevent the occurrence of heterogeneous phases. In addition, when an alkali metal hydroxide, alkali metal, is used as a precipitant, the metal is incorporated into the precipitate and remains there. You can In addition, when the above-mentioned precipitate is aged, it can be crystallized by firing it later to enhance its crystallinity. In particular, when the reaction temperature is raised, the equivalent number of ammonia added to the metal ions in the metal salt solution is increased by blowing oxygen into the reaction solution or adding an oxygen generating agent such as hydrogen peroxide to the reaction solution. It is possible to dispense with the high speed stirring, aging and heat treatment described above.

[0016]

EXAMPLES Examples of the present invention will be described below. Example 1 0.1 mol of iron (II) sulfate (divalent Fe sulfate, ie, ferrous sulfate (FeSO ₄ )), zinc sulfate (ZnS)
O ₄ ) 0.03 mol, manganese sulfate (MnSO ₄ ).
Dissolve 0.02 mol in 1 liter of distilled water to prepare a metal salt solution. This solution is placed in an air atmosphere at 20 ° C. and 800
0.4 mol / liter NH while stirring at rpm
1 liter of ₄ OH (1 equivalent to all metal ions) was added, and then stirring was continued at 20 ° C. for 6 hours. After this,
After aging at 90 ° C. for 5 hours, the formed precipitate was filtered off with a filter paper. The filtrate is treated with ICP (Inductivity C
When analyzed by open plasma,
The total detected value of Fe, Mn, and Zn was 5 ppm or less. The absolute amount of total metal lost was calculated from the total amount of this filtrate, while the initial total amount of metal charged was known.Calculating from these, the metal composition of the above-mentioned metal salt solution of the metal composition of the obtained precipitate was calculated. It can be seen that the deviation from is less than 0.001 mol ratio. At this level, it can be treated practically as if there is no compositional deviation. The obtained precipitate was heat-treated at 750 ° C. for 2 hours in an undried state to obtain a ferrite powder. The coercive force of this powder is VSM (Vi
bration Sample Magnetmete
When evaluated by r), 10 oersted (unit is 0
There is an umlaut at 0 of e. )Met. The result of X-ray diffraction (using CuKα ray, the same applies hereinafter) is shown in FIG. 1. From the peak marked with a circle in this figure, it was confirmed that the spinel had a single phase. In addition, electron micrograph (magnification 1
As a result of actually measuring each particle with a magnification of 0,000 and calculating from the magnification of an electron microscope, it can be seen that the average particle diameter is about 0.1 μm and the particle diameter distribution is 0.9 μm to 1.2 μm. Starting compounds of Mn and Zn are Ni, Co, Mg, Ti,
Similar results were obtained even when selected from each compound of Bi. When the composition in the synthesized particles was confirmed by an analytical electron microscope, no nonuniform composition was observed. The synthesized powder was dissolved in hydrochloric acid and qualitatively analyzed by ICP.
No elements other than e, Mn, and Zn were detected.

Example 2 0.12 mol of iron (II) chloride (divalent Fe hydrochloride, ie, ferrous chloride (FeCl ₂ )), barium chloride (Ba)
Cl ₂ ) 0.01 mol is dissolved in 1 liter of distilled water,
Prepare a metal salt solution. This solution is placed in an air atmosphere for 20
0.38 mol / g with stirring at 1000 ° C. and 1000 rpm
1 liter of NH ₄ OH (1 equivalent to all metal ions) was added, and then stirring was continued while blowing air at 20 ° C. for 3 hours. Then, after aging at 90 ° C. for 3 hours, the formed precipitate was filtered off with a filter paper. The filtrate is I
When analyzed by CP, the total detected value of Fe and Ba was 5 ppm or less. The absolute amount of total metal lost was calculated from the total amount of this filtrate, while the initial total amount of metal charged was known.Calculating from these, the metal composition of the above-mentioned metal salt solution of the metal composition of the obtained precipitate was calculated. It can be seen that the deviation from is less than 0.001 mol ratio. At this level, it can be treated practically as if there is no compositional deviation. The obtained precipitate was heat-treated at 850 ° C. for 1 hour without drying, to obtain a ferrite powder. When the coercive force of this powder was evaluated by VSM, it was 2800 oersted. In addition, as a result of performing X-ray diffraction in the same manner as in Example 1, it was found that it was a magnetobranbite single phase,
When an electron micrograph was taken in the same manner as in Example 1, the average particle size was 0.15 μm, and the particle size distribution was 0.1 μm to 0.2 μm.
It turned out to be m. Starting compound of Ba is S
Similar results were obtained even when selected from r and Pb compounds. When the composition in the synthesized particles was confirmed by an analytical analysis electron microscope, no nonuniform composition was observed. When the synthesized powder was dissolved in hydrochloric acid and qualitatively analyzed by ICP, elements other than Fe and Ba were not detected.

Example 3 0.1 mol of iron (II) sulfate, yttrium nitrate (Y (N
O ₃ ) ₂ ) Dissolve 0.02 mol in 1 liter of distilled water to prepare a metal salt solution. 2 this solution under air atmosphere
0.36 mol while stirring at 0 ° C. and 1000 rpm
1 liter of NH ₄ OH / liter (1 equivalent to all metal ions) was added, and then stirring was continued at 20 ° C. for 5 hours. Then, after aging at 90 ° C. for 5 hours, the formed precipitate was filtered off with a filter paper. When the filtrate was analyzed by ICP, the total detected value of Fe and Y was 5 ppm or less. The absolute amount of total metal lost was calculated from the total amount of this filtrate, while the initial total amount of metal charged was known.Calculating from these, the metal composition of the above-mentioned metal salt solution of the metal composition of the obtained precipitate was calculated. It can be seen that the deviation from is less than 0.001 mol ratio. At this level, it can be treated practically as if there is no compositional deviation. The obtained precipitate was heat-treated at 900 ° C. for 3 hours in an undried state to obtain a ferrite powder. When the saturation magnetization of this powder was evaluated by VSM, it was 20 emu / g. Further, as a result of X-ray diffraction performed in the same manner as in Example 1, it was found to be a garnet single phase, and when an electron micrograph was taken in the same manner as in Example 1, the average particle size was 0.3 μm and the particle size distribution was 0.27
It was found to be from μm to 0.35 μm. Similar results were obtained when an Al compound was added to the starting material. When the composition in the synthesized particles was confirmed by an analytical analysis electron microscope, no nonuniform composition was observed. When the synthesized powder was dissolved in hydrochloric acid and qualitatively analyzed by ICP, elements other than Fe and Y were not detected.

Example 4 Iron nitrate (divalent Fe nitrate, ie ferrous nitrate (F
_{e (NO 3) 2) 0.2mol} , zinc sulfate (ZnSO ₄₎
0.03 mol, nickel sulfate (NiSO ₄ ) 0.06
5 mol, 0.005 mol of copper sulfate (CuSO ₄ ) 3
Weigh in a liter beaker and add 1 liter of water to prepare a metal salt solution. This solution at 20 ℃, 10
Stir at 00 rpm, 0.96 mol / l NH
1 liter of ₄ OH (1.2 equivalents to metal ions) was added, and the mixture was reacted at room temperature for 5 hours and then aged at 80 ° C. for 2 hours. The precipitate was filtered off and dried at 80 ° C for 3 hours to obtain a powder. When the metal composition of the obtained powder was confirmed by fluorescent X-ray, it was Ni _0.650 Zn _O.300 Cu _0.005 Fe _2.00004 . Saturation magnetization (σ _s ) evaluated by VSM is 8
It was emu / g, and the particle size from the specific surface area was 12 nm. The result of X-ray diffraction is shown in FIG. ○ in this figure
It was confirmed from the peak marked that the spinel had a single phase.

Example 5 Fe, Ni, Z to obtain Ni _0.5 Zn _0.5 Fe ₂ O ₄
Each sulfate of n (Fe is a divalent sulfate) was dissolved in water, and 2 equivalents of NH ₄ OH was added to the metal ion. This mixed solution was heated to 90 ° C., and air was introduced into the mixed solution with a compressor. After reacting for 10 hours, the mixed solution was filtered and dried to obtain a ferrite powder. From ICP analysis,
The composition of the powder was Ni _0.5 Zn _0.5 Fe ₂ O ₄ , and it was found by X-ray diffraction that the powder had a spinnel single phase. TEM
(Transmission Electron Mi
Crosscopy) observation showed that a uniform cubic Ni—Zn ferrite having a particle size of 0.2 μm was synthesized without aggregation between particles.

Example 6 Fe, Mn, Z so as to be Mn _0.5 Zn _0.5 Fe ₂ O ₄
Each sulfate of n (Fe is a divalent sulfate) was dissolved in water, and 2.2 equivalent of NH ₄ OH was added to the metal ion. This mixed solution was heated to 80 ° C., and oxygen was introduced into the mixed solution from an oxygen cylinder. After reacting for 5 hours, the mixed solution was filtered and dried to obtain a ferrite powder. From ICP analysis,
The composition of the powder was Mn _0.5 Zn _0.5 Fe ₂ O ₄ , and it was found from X-ray diffraction that the powder had a spinnel single phase. TEM
From the observation, a uniform cubic Mn-Zn ferrite having a particle size of 0.5 μm was synthesized without condensation between particles.

Example 7 Fe, Ni, Z so as to be Ni _0.5 Zn _0.5 Fe ₂ O ₄
Each sulfate of n (Fe is a divalent sulfate) was dissolved in water, and 2 equivalents of NH ₄ OH was added to the metal ion. The mixture was heated to 200 ° C. After reacting for 8 hours, the mixed liquid was filtered and dried to obtain a ferrite powder. From the ICP analysis, the composition of the powder was Ni _0.5 Zn _0.5 Fe ₂ O ₄ , and it was found from the X-ray diffraction that the powder had a spinnel single phase. From TEM observation, particle size of 0.0
A uniform cubic Ni—Zn ferrite of 5 μm was synthesized.

Example 8 Fe, Ni, Z so as to be Ni _0.5 Zn _0.5 Fe ₂ O ₄
Each sulfate of n (Fe is a divalent sulfate) was dissolved in water, and 2 equivalents of NH ₄ OH was added to the metal ion. Hydrogen peroxide solution (10% by weight) was added to this mixed solution and heated to 200 ° C. After reacting for 8 hours, the mixed liquid was filtered and dried to obtain a ferrite powder. From the ICP analysis, the composition of the powder was Ni _0.5 Zn _0.5 Fe ₂ O ₄ , and it was found from the X-ray diffraction that the powder had a spinnel single phase. As a result of TEM observation, uniform cubic Ni—Zn ferrite having a particle size of 0.3 μm was synthesized without aggregation between particles.

Comparative Example 1 Iron nitrate (III) (trivalent Fe nitrate, ie, nitric acid No. 2
Iron (Fe (NO ₃ ) ₃ ) 0.1 mol, zinc nitrate (ZnN
O ₃ ) 0.03 mol, manganese nitrate (Mn ((NO ₃ )
₂ ) Dissolve 0.02 mol in 1 liter of distilled water to prepare a metal salt solution. This solution was placed in an air atmosphere at 20 ° C. for 8 hours.
While stirring at 00 rpm, 1 liter of NH ₄ OH at 0.4 mol / liter (1 equivalent to all metal ions) was added, and then stirring was continued at 20 ° C. for 10 hours. After that, the formed precipitate was filtered off with a filter paper. The filtrate is ICP
When analyzed by, Mn is 1000 ppm or more, Z
420 ppm of n was detected. The absolute amount of total metal lost was calculated from the total amount of this filtrate, while the initial total amount of metal charged was known.Calculating from these, the metal composition of the above-mentioned metal salt solution of the metal composition of the obtained precipitate was calculated. It can be seen that the deviation from is more than 0.05 mol ratio. In this range, the composition is practically treated as a compositional deviation. The obtained precipitate was heat-treated at 900 ° C. for 3 hours in an undried state to obtain a ferrite powder. When the coercive force of this powder was evaluated by VSM, it was 3 Oersted. Further, as a result of X-ray diffraction performed in the same manner as in Example 1, it was found that the spinel phase and the corundum phase were observed, and when an electron micrograph was taken in the same manner as in Example 1, the average particle size was 0.3 μm, It was found that the diameter distribution was 0.1 μm to 0.7 μm.

Comparative Example 2 In order to prepare Ni _0.5 Zn _0.5 Fe ₂ O ₄ by the solid phase method (dry method), α-Fe ₂ O ₃ , ZnO and NiO were weighed in a predetermined ratio, and water and iron having a diameter of 1 mm were used. Mixing was performed by a ball mill method using spheres. After drying, heat treatment at 1000 ℃ for 2 hours,
It was crushed by water and a ball mill method. The powder obtained is I
The Ni-Zn ferrite powder was found to have Fe and Cr impurities by CP analysis, and had a wide particle size distribution with an average particle size of 2 [mu] m and agglomeration between particles, as observed by TEM.

According to the present invention, when NH ₄ OH is used as a precipitant for the metal salt solution, the metal ion produces ammonium ion when it is highly alkaline due to the excessive amount of NH ₄ OH used. In order to solve the problem that precipitation is unlikely to occur, the generation of metal ions by ammonium ions is suppressed by selecting either or both of the concentration of NH ₄ OH and the amount used, the reaction temperature, and the presence or absence of an oxidizing agent. It can also be said that the precipitation was easily caused.

[0027]

EFFECTS OF THE INVENTION According to the present invention, since a constant concentration of ammonia water is used as a precipitating agent for causing precipitation from a predetermined metal salt solution, the chemical equivalent conditions are controlled, so that the conventional dry method is used. There is no mixing of impurities from each process,
In addition, unlike the conventional wet method, high-purity and composition-free ferrite powder free of impurities such as alkali metals can be obtained, and these properties are further improved by high-speed stirring and selection of the equivalent ratio of aqueous ammonia to metal ions. It is also possible to obtain a high-quality powder with a uniform composition and no out-of-phase by stirring at high speed. The coercive force of a magnetic material made of a ferrite sintered body obtained from such a ferrite powder as a raw material. It is possible to improve and stabilize the electro-magnetic properties and mechanical properties of.
Further, by aging the precipitate, the crystallinity of the ferrite powder obtained by the subsequent firing can be increased, and the above characteristics can be further improved. At this time, by selecting the reaction temperature and the oxidation conditions, it is possible to broaden the selection range of the equivalent ratio of ammonia water to the metal ions without particularly requiring the above high-speed stirring, and especially for aging and subsequent heat treatment. It is possible to eliminate the need for it, and it is possible to improve the above-mentioned electro-magnetic properties and mechanical properties and to stabilize it, so that it can be used as a high-performance and highly-functional component material. . The ferrite powder thus obtained has a uniform particle size,
Since the particles are fine and there is no coagulation of the particles, the powder is uniformly packed when the molded body is obtained, and the sintered body also has a uniform crystal grain size so that dense ceramics can be obtained at a lower temperature than usual. became. In addition, since metal salts and ammonia water, which are low in cost, are used as the raw material and the reaction can be carried out in air under normal pressure, it can be produced with simple production equipment, and if the conditions such as reaction temperature are selected, the process will be It can be manufactured at a low temperature of 100 ° C. or lower mainly by one step of precipitation formation, and does not require a furnace for obtaining a high temperature of 1000 ° C. or higher as in the dry method, and can reduce the manufacturing cost. Further, since the ferrite powder of the present invention has a small particle size, a ferrite sintered body using this as a raw material can be obtained at a temperature lower than a normal firing temperature, and can be co-fired with a low melting point metal. When obtained, it can be fired at the same time with the unfired material to form electrodes and conductor portions of the circuit pattern, and is optimal as a low-temperature fired material. This is combined with the high purity and further enhances its suitability. Further, since the ferrite powder of the present invention has a small grain size, it is possible to manufacture a dense ferrite sintered body with uniform crystal grains, and the mechanical strength thereof is high, and at the same time, the electromagnetic properties such as coercive force can be improved. It is possible to provide high-performance parts and members such as various inductors, coils, LC parts, magnets, magnetic bodies for magnetic recording media, magnetic fluids, and magnetic shields. Further, since it has excellent dispersibility in resin and the like, it is also promising as a material for thin films and plating. These performances are further enhanced by the narrow width of the particle size distribution of the ferrite powder. Further, the above performance is further enhanced together with the fact that there is no compositional deviation and the nonuniformity of composition.

[Brief description of drawings]

FIG. 1 is an X-ray diffraction diagram of a ferrite powder obtained by the method of the first example of the present invention.

FIG. 2 is an X-ray diffraction diagram of a ferrite powder obtained by the method of the fourth embodiment of the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H01F 1/34 B

Claims (28)

[Claims] 1. Sr, Ba, Pb, Zn, Ni, Mn,
Fe is a metal salt of Fe in the group consisting of Co, Cu, Mg, Y, Al, Bi, Ti and Fe and at least one other metal, and Fe is a metal salt of divalent Fe. A step of obtaining a metal salt aqueous solution containing a metal salt in which each of the metal salts is at least one selected from the group consisting of sulfates, chlorides and nitrates, and 0.05 to 5.0 mol / l in the metal salt aqueous solution. A method for producing a ferrite powder, the method including the step of forming a precipitate by adding the NH ₄ OH solution of 1. 2. A metal salt of Fe in the group consisting of Ba, Zn, Mn, Ni, Y, Cu and Fe and at least one other metal, and a divalent Fe metal salt with respect to Fe. And the respective metal salts are sulfates,
A step of obtaining an aqueous metal salt solution containing a metal salt which is at least one kind of a group consisting of chloride and nitrate; and precipitation by adding 0.05 to 5.0 mol / l NH ₄ OH solution to the aqueous metal salt solution. A method for producing a ferrite powder, the method including the step of producing a product. 3. The NH ₄ OH solution has a concentration of 0.1 to 3.0.
It is mol / l, The manufacturing method of the ferrite powder of Claim 1 or 2. 4. Fe ²⁺ of a divalent Fe metal salt is calculated as Fe ³⁺ , and NH _{4 is} added to the metal ion in the metal salt aqueous solution.
The method for producing a ferrite powder according to claim 1, wherein the OH solution is added in an amount of more than 0.8 equivalents and less than 3 equivalents. 5. A NH ₄ 2-valent to Fe ²⁺ metal salt of Fe with respect to the metal ions of the calculated in metal salt solution as Fe ³⁺
The method for producing a ferrite powder according to claim 1, wherein the OH solution is added in an amount of more than 0.8 equivalents and less than 2.5 equivalents. 6. A Fe ²⁺ of a divalent Fe metal salt is calculated as Fe ³⁺ , and NH _{4 is} added to a metal ion in the metal salt aqueous solution.
4. Addition of 0.8 to 1.2 equivalents of OH solution.
5. The method for producing a ferrite powder according to any one of 1. 7. NH ₄ the Fe ²⁺ divalent Fe metal salt to the metal ions of the calculated in metal salt solution as Fe ³⁺
The method for producing a ferrite powder according to claim 1, wherein 1.0 equivalent of an OH solution is added. 8. The operation of adding an NH ₄ OH solution to an aqueous metal salt solution is performed in the presence of sufficient oxygen so that Fe ²⁺ of a metal salt of divalent Fe becomes Fe ³⁺ . Alternatively, the method for producing the ferrite powder according to 6 or 7. 9. The step of adding a NH ₄ OH solution to the aqueous metal salt solution to form a precipitate comprises adding NH _{3 to the} aqueous metal salt solution.
_The method for producing a ferrite powder according to any one of claims 1 to 3 or 6 to 8, which has a step of stirring a mixed solution containing a ₄ OH solution. 10. The method for producing a ferrite powder according to claim 9, wherein the stirring is 300 to 3000 rpm. 11. The method for producing a ferrite powder according to claim 9, wherein the stirring is performed at 500 to 2000 rpm. 12. The step of forming a precipitate by adding an NH ₄ OH solution to an aqueous metal salt solution comprises the step of heating a mixed solution of the aqueous NH ₄ OH solution to the aqueous metal salt solution under atmospheric pressure. Any one of to 3 or 6 to 11
5. The method for producing a ferrite powder according to any one of 1. 13. The method for producing a ferrite powder according to claim 12, wherein the heating is performed at 0 to 40 ° C. for 3 to 10 hours. 14. The method for producing a ferrite powder according to claim 12, wherein the heating is performed at 10 to 30 ° C. for 3 to 7 hours. 15. The method for producing a ferrite powder according to claim 1, further comprising the step of aging the precipitate. 16. The aging is performed at 80 to 100 ° C.
5. The method for producing a ferrite powder according to item 5. 17. The method for producing a ferrite powder according to claim 15, wherein the aging is performed at 80 to 90 ° C. for 1 to 5 hours. 18. The step of forming a precipitate by adding an NH ₄ OH solution to an aqueous metal salt solution comprises heating a mixed solution of the aqueous NH ₄ OH solution to the aqueous metal salt solution to 60 ° C. or higher and 100 ° C. or lower in the presence of oxygen. The method for producing a ferrite powder according to claim 4 or 5, further comprising: 19. The step of heating a mixed solution obtained by adding an NH ₄ OH solution to an aqueous solution of a metal salt to 60 ° C. or higher and 100 ° C. or lower in the presence of oxygen is performed by gasifying the mixed liquid with a gas having an oxygen content of 0.1% or more. The method for producing a ferrite powder according to claim 18, further comprising a step of performing liquid contact. 20. A process of producing a precipitate by the addition of NH ₄ OH solution to the metal salt solution is heated NH ₄ OH solution below mixture 300 ° C. under presence of oxygen 100 ° C. or more plus to the metal salt solution 4. The method according to claim 4 or 5, which comprises a step of
The method for producing a ferrite powder according to item 1. 21. The step of heating a mixed solution obtained by adding an NH ₄ OH solution to an aqueous solution of a metal salt to 100 ° C. or higher and 300 ° C. or lower in the presence of oxygen includes a step of heating after adding an oxidizing agent that generates oxygen. 20. The method for producing a ferrite powder as described in 20. 22. The method for producing a ferrite powder according to claim 1, further comprising a step of filtering a liquid containing a precipitate. 23. The ferrite according to any one of claims 1 to 3 or 6 to 17, which has a step of filtering a liquid containing a precipitate and a step of subjecting the filtered precipitate to heat treatment directly or after drying. Powder manufacturing method. 24. The heat treatment is carried out at 500 ° C. to 1000 ° C.
The method for producing a ferrite powder according to claim 23, wherein the method is for 1 to 10 hours. 25. The heat treatment is performed at 700 to 900 ° C. for 1 to 5
The method for producing a ferrite powder according to claim 24, which is time. 26. The method according to claim 1, further comprising a step of spray-drying a mixed solution containing the precipitate after the precipitate is formed from the mixed solution, and a step of heat-treating the obtained powder. 5. The method for producing a ferrite powder according to any one of 1. 27. The heat treatment is performed at 500 ° C. to 1000 ° C.
27. The method for producing a ferrite powder according to claim 26, which is 1 to 10 hours. 28. The heat treatment is performed at 700 ° C. to 900 ° C. for 1 to 5
The method for producing a ferrite powder according to claim 26, which is time.