Magnetic material and process for its production

Abstract

A magnetic material characterized by a chemical structural formula Fe(Al 1-x Mn x )2O4, where 0 < x < 1, and which exhibits ferromagnetism, and where a range of a value of x is represented by x ≥ 0.2.

Description

[Technical field]

[0001] The present disclosure relates to a magnetic ferrite material that is ferromagnetic and a method for producing the same. [State of the art]

[0002] There is usually a need to develop a magnetic material with high magnetic permeability µ in the high-frequency range. In recent years, ferrite has been considered as such a material.

[0003] A ferrite is a ceramic composed mainly of iron oxide, and examples of the ferrite include Mg(Fe 1-x Mn x)2O4, FeAl2O4 (hercynite), and the like. Furthermore, ferrites are divided into magnetic substances that exhibit magnetism and non-magnetic substances that do not. The magnetic substance, especially a ferromagnetic ferrite, is used in a wide variety of fields, such as high-frequency inductors, magnetic cores for transformers, and black pigment powder for applications. (See, for example, Patent Literature (PTL) 1.)

[0004] Patent Publication No. 1 discloses a ceramic burner as a technique for using a ferrite. Patent Publication No. 2 discloses a method for producing a magnetic composite powder in which the metal Fe and an oxide coexist. The method comprises heat-treating a powder formed from an M-Fe-O oxide containing the metal element M and Fe to partially reduce the oxide. A starting material is preferably an M-Fe-O oxide powder.PTL 3 discloses an insulating magnetic metal particle comprising a magnetic metal particle containing at least one metal selected from the group consisting of Co, Fe, and Ni and having a diameter of 5 to 500 nm, a first inorganic insulating layer made of an oxide covering the surface of the magnetic metal particle, and a second inorganic insulating layer made of an oxide that produces a eutectic crystal upon heating by reacting with the first inorganic insulating layer, wherein the second inorganic insulating layer is coated on the first inorganic insulating layer. PTL 4 discloses a spinel ferrite magnetic material obtained by replacing part of the Fe of MgFe2O4 ferrite with Mn and having the formula Mg(Fe) 1-x Mn x )2O4 (x denotes the amount of Mn solution, 0 <x≤0,4). [List of citations][Patent literature] [PTL 1] JP S62 - 112 907 A [PTL 2] JP 2011 - 208 184 A [PTL 3] US 2008 / 0 029 300 A1 [PTL 4] JP 2007 - 088 215 A [Summary of the invention][Technical problem]

[0005] PTL 1 discloses, as a material for the ceramic burner, a ferrite having a spinel structure of MgAl2O4, FeAl2O4, CoAl2O4, or the like. The use of hercynite FeAl2O4, which is composed of Fe and Al, is sometimes desirable, especially in fields where ferrite is used.

[0006] However, hercynite FeAl2O4 is a non-magnetic substance and therefore cannot be used when the magnetic properties of ferrite are desired. Therefore, there was a need to develop a magnetic material composed of Fe and Al with high magnetic properties.

[0007] In view of the problem described above, the object of the present invention is to provide a magnetic material with high magnetic properties and a method for producing the same. [Solution to the problem]

[0008] A magnetic material according to one aspect of the present disclosure is a magnetic material represented by a chemical structural formula Fe(Al 1-x Mn x )2O4, where 0 < x < 1, and which exhibits ferromagnetism, and where x ≥ 0.2. [Advantageous effects of the invention]

[0009] According to the present disclosure, it is possible to provide a magnetic material having high magnetic properties and a method for producing the same. [Brief description of the drawings] [ Fig. 1] Fig. 1 is a flow chart showing a process for producing Fe(Al 1-x Mnx )2O4 according to one embodiment. [ Fig. 2] Fig. Figure 2 is a diagram showing an X-ray diffraction pattern of Fe(Al 1-x Mn x )2O4 in the case of x = 0. [ Fig. 3] Fig. Figure 3 is a diagram showing an X-ray diffraction pattern of a product heat-treated under different gas atmospheres, in the case of x = 0.2. [ Fig. 4] Fig. Figure 4 is a diagram showing an X-ray diffraction pattern of a product heat-treated under different gas atmospheres, in the case of x = 0.4. [ Fig. 5] Fig. Figure 5 is a diagram showing an X-ray diffraction pattern of a product heat-treated under different gas atmospheres, in the case of x = 0.5. [ Fig. 6] Fig. Figure 6 is a diagram showing an X-ray diffraction pattern of a product heat-treated under different gas atmospheres, in the case of x = 0.6. [ Fig. 7] Fig. Figure 7 is a diagram showing an X-ray diffraction pattern of a product heat-treated under different gas atmospheres, in the case of x = 0.8. [ Fig. 8] Fig. Figure 8 is a diagram showing an X-ray diffraction pattern of a product obtained under different gas atmospheres caused by Fe(Al 1-x Mn x )2O4 with a spinel structure. [ Fig. 9A] Fig. Figure 9A is a table summarizing the products when a value of x and an amount of H2 contained are changed. [ Fig. 9B] Fig. Figure 9B is a graph showing an X-ray diffraction pattern of a product prepared by pulsed electric-current pressure sintering in the case of x = 0.5. [ Fig. 9C] Fig. Figure 9C is a graph showing X-ray diffraction patterns of products prepared by current pulse pressure sintering and atmospheric heat treatment in the case of x = 0.5. [ Fig. 10A] Fig. Figure 10A is a scanning electron microscopy (SEM) image of Fe(Al 1-x Mn x )2O4 powder in the case of x = 0. [ Fig. 10B] Fig. Figure 10B is an SEM image of Fe(Al 1-x Mn x )2O4 powder in the case of x = 0.2. [ Fig. 10C] Fig. 10C is an SEM image of Fe(Al 1-x Mn x )2O4 powder in the case of x = 0.4. [ Fig. 10D] Fig. Figure 10D is an SEM image of Fe(Al 1-x Mn x)2O4 powder in the case of x = 0.5. [ Fig. 10E] Fig. Figure 10E is an SEM image of Fe(Al 1-x Mn x )2O4 powder in the case of x = 0.6. [ Fig. 10F] Fig. 10F is an SEM image of Fe(Al 1-x Mn x )2O4 powder in the case of x = 0.8. [ Fig. 10G] Fig. 10G is an SEM image of Fe(Al 1-x Mn x )2O4 powder in the case of x = 1.0. [ Fig. 11] Fig. Figure 11 is a diagram showing a relationship between a value of x and a lattice parameter of Fe(Al 1-x Mn x )2O4 shows. [ Fig. 12A] Fig. Figure 12A is a diagram showing the BH properties of Fe(Al 1-x Mn x )2O4 in the case of x = 0. [ Fig. 12B] Fig. Figure 12B is a diagram showing the BH properties of Fe(Al 1-x Mn x )2O4 in the case of x = 0.2. [ Fig. 12C] Fig. 12C is a diagram showing the BH properties of Fe(Al 1-x Mn x )2O4 in the case of x = 0.6. [ Fig. 12D] Fig. Figure 12D is a diagram showing the BH properties of Fe(Al 1-x Mn x )2O4 in the case of x = 0.7. [ Fig. 12E] Fig. Figure 12E is a diagram showing the BH properties of Fe(Al 1-x Mn x )2O4 in the case of x = 0.8. [ Fig. 12F] Fig. 12F is a diagram showing the BH properties of Fe(Al 1-x Mn x )2O4 in the case of x = 0.9. [ Fig. 13] Fig. 13 is a diagram showing a relationship between a value of x in Fe(Al 1-x Mn x )2O4 and the magnetic mass magnetization σ s shows. [ Fig. 14] Fig. 14 is a diagram showing a relationship between a value of x in Fe(Al 1-x Mn x)2O4 and a magnetic saturation flux density B S shows. [ Fig. 15] Fig. 15 is a diagram showing a relationship between a value of x in Fe(Al 1-x Mn x )2O4 and log H C shows. [ Fig. 16] Fig. 16 is a table showing a relationship between values ​​of x in Fe(Al 1-x Mn x )2O4 and magnetic properties. [Description of embodiments]

[0010] (The knowledge of the person skilled in the art forming the basis of the present disclosure) Before describing embodiments of a magnetic material and a method for producing the same according to the present disclosure, the knowledge of the person skilled in the art forming the basis of the present disclosure will be described.

[0011] As previously described, hercynite FeAl2O4, a type of ferrite, is a non-magnetic substance and does not exhibit ferromagnetism. The present inventors attempted to develop a magnetic ferrite material exhibiting ferromagnetism and having a novel composition by adding Mn as the fourth element in addition to Fe, Al, and O to hercynite FeAl2O4 to produce a magnetic material with high magnetic properties. However, the inventors found that it is difficult to produce a powder using the conventional solid-state reaction method, sol-gel method, and citric acid gel method, and that it is not possible to produce such a complex magnetic material. Based on these experimental results, the inventors obtained the following knowledge.

[0012] If the structure of ferrite is represented by AB2O4 (where A and B are elements), then ferrite with a new composition is represented by Fe(Al 1-x Mn x )2O4. In hercynite, FeAl2O4, Fe in the A position is divalent, and Al in the B position is trivalent. Consequently, in ferrite with the new composition, Fe in the A position must be divalent, and Mn in the B position must be trivalent.

[0013] When hercynite FeAl2O4 is prepared using the solid-state reaction method, it is assumed here that after α-Fe2O3(Fe 3+ ) and fine γ-Al2O3 as starting materials were evenly mixed together, α-Fe2O3(Fe 3+ ) and γ-Al2O3 are heat-treated at 900°C in N2 gas with slightly less than 1% H2, where Fe 3+ to Fe 2+ is reduced and FeAl2O4 is produced. However, when the solid-state reaction process is applied to ferrite Fe(Al 1-x Mn x)2O4 with a new composition, then Mn is converted into Mn oxide, a raw material, to Mn 2+ reduced and consequently placed in the A-position. Therefore, it is difficult to find Fe(Al 1-x Mn x )2O4, in which part of Al is in the B-position of Fe(Al 1-x Mn x )2O4 is replaced by Mn.

[0014] Furthermore, with the sol-gel method in which metal alkoxide is hydrolyzed and the citric acid gel method in which a metal complex is formed by adding citric acid and ethylene glycol to a mixed aqueous solution of metal nitrate, then the organic components are removed by heating the metal complex in the atmosphere, and finally a powder is prepared by further heating the metal complex at high temperature, it is difficult to control a heat treatment atmosphere so that Fe 2+ and Mn 3+simultaneously, so that the desired ferrite Fe(Al 1-x Mn x )2O4 with a new composition is obtained.

[0015] In view of this, a magnetic material according to one aspect of the present disclosure is a magnetic material represented by a chemical structural formula Fe(Al 1-x Mn x )2O4, where 0 < x < 1, and which exhibits ferromagnetism, and where x ≥ 0.2.

[0016] With this configuration it is possible to provide a magnetic material with high magnetic properties.

[0017] Furthermore, a range of a value of the magnetic mass magnetization σ s [A·m 2 / kg] of the magnetic material can be given by σ s ≥ 10 can be displayed.

[0018] With this configuration, it is possible to obtain a magnetic material suitable as a material for a device that must have high magnetic properties.

[0019] Furthermore, a range of a value of x is represented by x ≥ 0.2.

[0020] With this configuration, it is possible to obtain a magnetic material suitable as a material for a device that must have high magnetic properties.

[0021] Furthermore, the magnetic material includes manganese dioxide MnO2 as a raw material.

[0022] With this configuration, it is possible to introduce Mn into the same position where Al is introduced by hercynite FeAl2O4, it is possible to produce a magnetic ferrite material characterized by the chemical structural formula Fe(Al 1-x Mn x )2O4, is easy to prepare.

[0023] Furthermore, a method for producing a magnetic material according to an aspect of the present disclosure is a method for producing a magnetic material represented by a chemical structural formula Fe(Al 1-x Mn x )2O4, where 0 < x < 1, and which exhibits ferromagnetism, the preparation method comprising: preparing a mixed aqueous solution by dissolving, in distilled water, Fe nitrate, Al nitrate, and an oxide containing Mn, the Fe nitrate, Al nitrate, and oxide being starting materials; preparing a metal-citric acid complex by mixing citric acid and ethylene glycol with the mixed aqueous solution; obtaining a precursor by boiling the metal-citric acid complex into a gel and drying the gel; and obtaining the magnetic material by sintering the precursor.

[0024] With this configuration it is possible to provide a magnetic material with high magnetic properties.

[0025] Furthermore, in obtaining the magnetic material, a trivalent Fe ion and a tetravalent Mn ion can be reduced to a divalent Fe ion and a trivalent Mn ion, respectively.

[0026] With this configuration, it is possible to introduce Mn into the same position where Al is introduced by hercynite FeAl2O4, it is possible to obtain a magnetic ferrite material represented by the chemical structural formula Fe(Al 1-x Mn x )2O4, is easy to prepare.

[0027] Furthermore, the Fe nitrate can be iron(III) nitrate nonahydrate Fe(NO3)3 9H2O, the Al nitrate can be aluminum(III) nitrate nonahydrate Al(NO3)2 9H2O and the oxide containing Mn can be manganese dioxide MnO2.

[0028] With this configuration, it is possible to introduce Mn into the same position where Al is introduced by hercynite FeAl2O4, it is possible to produce a magnetic ferrite material characterized by the chemical structural formula Fe(Al 1-x Mn x )2O4, is easy to prepare.

[0029] Furthermore, in preparing the metal-citric acid complex, a molar ratio of a metal ion, citric acid and ethylene glycol in the mixed aqueous solution may be 1:3:9.

[0030] With this configuration, it is possible to produce a single-phase magnetic ferrite material characterized by a chemical structural formula Fe(Al 1-x Mn x )2O4, is easy to prepare.

[0031] In the following, embodiments are described in more detail with reference to the drawings. (Embodiment)[1. Definitions of terms]

[0032] First, definitions of the terms used in an embodiment are given.

[0033] A citric acid gel process (or "polymerized complex" process) is defined as the following method for producing a material. First, a stable chelate complex (metal-citric acid complex) is prepared using various types of metal ions and citric acid. Ethylene glycol is added to the metal-citric acid complex, and the metal-citric acid complex is dissolved and dispersed in ethylene glycol. The ethylene glycol in which the metal-citric acid complex has been dispersed is esterified by heating and polymerization, and the metal-citric acid complex (polymer-metal complex) is uniformly enclosed in the polyester. In other words, ethylene glycol is added to the metal-citric acid complex and esterified by heating and polymerization to obtain a gel. Subsequently, the gelled metal-citric acid complex is calcined (pre-calcined or fired) to produce an oxide, i.e.the desired substance.

[0034] The network structure of the polymer-metal complex obtained by the citric acid gel process (or "polymerized complex" process) is formed primarily by ester polymerization and copolymerization and is chemically stable. Consequently, the mobility of the metal ions is low, resulting in a process advantage that reduces the aggregation or segregation of metal elements in a subsequent calcination step.

[0035] A solid-phase process is defined as the following method for producing a material. Various types of raw material powders, which serve as starting materials, are weighed in a predetermined amount and mixed together. After mixing, the mixture is first temporarily calcined and then fired. Accordingly, a desired substance is produced. It should be noted that the solid-phase process is also called a solid-state reaction process.

[0036] A lattice parameter is one of the parameters used as crystal data and a significant element for identifying a substance. Lattice parameters are represented by the lengths a, b, and c of the sides of a lattice unit in a crystal lattice and the angles α, β, and γ between the sides.

[0037] Furthermore, the action of a magnetic field on a magnetic substance causes a magnetic moment to align in a magnetic field direction, resulting in magnetization. In other words, magnetization refers to the alignment of a magnetic moment in a direction due to the action of a magnetic field on a magnetic substance. Furthermore, the magnetization properties of a magnetic substance are generally irreversible and change in a curved (nonlinear) manner. Such irreversible properties of the magnetic substance are called hysteresis.

[0038] Furthermore, the magnetic moment of a magnetized substance is also called magnetic susceptibility [emu]. In this case, the magnetic susceptibility is represented by a vector and indicates the intensity of the magnetization. A magnetic moment per unit volume is called magnetic volume susceptibility, and a magnetic moment per unit mass is called magnetic mass magnetization (emu / g = A m 2 / kg). These indicate the intensity of the magnetization. It should be noted that the magnetic mass magnetization σ s in the embodiment described below can be referred to as “magnetic susceptibility” for the sake of simplicity.

[0039] Furthermore, the intensity of magnetization when a magnetic field acts on a magnetic substance until the magnetic field is saturated is called magnetic saturation susceptibility Js.

[0040] Furthermore, the magnetic flux density B[T] denotes the surface density of the magnetic flux per unit area and can be referred to as a magnetic field strength for simplicity. In addition, a magnetic flux density B corresponding to a magnetic saturation susceptibility Js is called the magnetic saturation flux density B S [T]. It is noted that, with respect to the magnetic saturation flux density B S , a point at which the intensity of magnetization reaches saturation, is called the S-point.

[0041] Removing the magnetic field after saturation magnetization does not cause the magnetization intensity to become zero due to hysteresis, and a magnetization with a certain intensity remains. The magnetization intensity is called the residual magnetization J rFurthermore, the action of an opposing magnetic field on a magnetic substance in a state of residual magnetization causes the intensity of magnetization in an acting magnetic field with a certain intensity to become zero. The intensity of the magnetic field at this time is called the coercive field strength H C (Oe = 10 3 / (4π) A / m). A substance with a low coercive field strength is called a soft magnetic material. In contrast, a substance with a high coercive field strength is called a hard magnetic material (e.g., a permanent magnet). The value of the coercive field strength varies greatly depending on the magnetic material.

[0042] Magnetic permeability µ is an index that indicates how easily a magnetic flux penetrates a magnetic material, i.e., the degree of change in the magnetic flux when exposed to a magnetic field of a certain intensity. Magnetic permeability indicates the ease of magnetization and is one of the factors used to evaluate the properties of a magnetic substance.

[0043] An index such as magnetic permeability, which indicates a relationship between a magnetic field and magnetization, is called magnetic susceptibility (magnetizability). Magnetic susceptibility χ is usually defined by the following equation. χ=J / H

[0044] Here, H represents a magnetic field, and J represents the intensity of magnetization. The above equation expresses that when a magnetic field acts on a magnetic substance, the magnetization is a function of the magnetic field.

[0045] Furthermore, a material with high-permeability properties, through which a higher magnetic flux density is induced by the action of a weak external magnetic field, is called a high-permeability magnetic material or a soft magnetic material. A high-permeability magnetic material must have a high magnetic permeability µ, a low coercive field strength H C and a high magnetic saturation flux density B S and must have a small loss. Ferrite, as a soft magnetic material, is an oxide, usually has a high electrical resistance and can usually be used for high frequencies. [2. Composition of ferrite Fe(Al 1-x Mn x )2O 4]

[0046] A magnetic material according to the embodiment is ferrite Fe(Al 1-x Mn x )2O4, an oxide containing Fe, Al and Mn.

[0047] The structure of ferrite can usually be represented by AB2O4 (where A and B are arbitrary metal elements). Ferrite according to the embodiment has a structure in which Fe is in the A position and Al and Mn are in the B position, and a composition in which part of Al in the B position of hercynite FeAl2O4, which is known as a type of ferrite, is replaced by Mn.

[0048] Ferrite Fe(Al 1-x Mn x )2O4 according to the embodiment not only has the same properties as hercynite, which contains Fe and Al as components, but also shows, in contrast to hercynite, ferromagetism. [3. Process for producing ferrite Fe(Al1-x Mn x )2O 4]

[0049] The following describes a process for producing ferrite Fe(Al 1-x Mn x )2O4 according to the embodiment described.

[0050] The process for producing ferrite Fe(Al 1-x Mn x )2O4 according to the embodiment is obtained by modifying the previously described citric acid gel process. In the citric acid gel process, the following are used: iron(III) nitrate nonahydrate Fe(NO3)3·9H2O and aluminum(III) nitrate nonahydrate Al(NO3)3·9H2O, metal nitrate, as sources of metal elements of ferrite Fe(Al 1-x Mn x )2O4; and manganese(II) nitrate hexahydrate Mn(NO3)2·6H2O as a source of Mn.

[0051] In contrast, the process for producing ferrite Fe(Al 1-x Mn x)2O4 according to the embodiment, the following are used: iron(III) nitrate·nonahydrate Fe(NO3)3·9H2O and aluminum(III) nitrate.Nonahydrate Al(NO3)3·9H2O, metal nitrate, as sources of metal elements of ferrite Fe(Al 1-x Mn x )2O4. In addition, manganese dioxide MnO2(Mn 4+ ) as a source of Mn. More specifically, a mixed aqueous solution is prepared by uniformly mixing fine particles of manganese dioxide MnO2 with an aqueous nitrate solution in which iron(III) nitrate nonahydrate Fe(NO3)3 9H2O and aluminum(III) nitrate nonahydrate Al(NO3)3 9H2O are mixed together.

[0052] Furthermore, citric acid and ethylene glycol are mixed with the mixed aqueous solution, and the mixed aqueous solution is heat-treated under different gas atmospheres until the organic components are removed. In this way, Fe(Al 1-x Mn x)2O4 by reacting trivalent Fe ions with Fe 3+ and tetravalent Mn ions Mn 4+ to divalent Fe ions Fe 2+ and trivalent Mn ions Mn 3+ It should be noted that ferrite Fe(Al 1-x Mn x )2O4, a new material, for simplicity's sake called Fe(Al 1-x Mn x )2O4, iron(III) nitrate. Nonahydrate Fe(NO3)3·9H2O is referred to simply as Fe(NO3)3·9H2O, aluminum(III) nitrate. Nonahydrate Al(NO3)3·9H2O is referred to simply as Al(NO3)3·9H2O, and manganese dioxide MnO2 is referred to simply as MnO2.

[0053] The manufacturing process is described in more detail below.

[0054] Fig. 1 is a flowchart showing a method for manufacturing a ferrite magnetic material according to the embodiment.

[0055] As in Fig. As shown in Figure 1, first a solution 1a, a solution 1b and a solution 1c are prepared.

[0056] Solution 1a contains, as starting materials, Fe(NO3)3·9H2O and Al(NO3)3·9H2O, metal nitrate, and MnO2 as a source of Mn. Both Fe(NO3)3·9H2O and Al(NO3)3·9H2O contain H2O and are therefore soluble and miscible. In addition, Fe in Fe(NO3)3·9H2O and Al in Al(NO3)3·9H2O are ionized in an aqueous solution and are present as Fe 3+ and Al 3+ By ionization, Fe and Al are uniformly dispersed in the aqueous solution. It should be noted that it is preferable that MnO2 be made dispersible in an aqueous solution and that a particulate MnO2 powder with a diameter of at most 0.5 µm be used.

[0057] Solution 1b is a citric acid C3H4(OH)(COOH)3 solution. Please note that the citric acid used here can be anhydrous citric acid (C(CH2COOH)2(OH)(COOH)) or citric acid monohydrate C6H8O7·H2O.

[0058] Solution 1c is an ethylene glycol HOCH2CH2OH solution.

[0059] Next, solution 1a, solution 1b, and solution 1c are mixed together (step S1). It is preferable that when the total mole number of metal ions in solution 1a is 1, the mixing ratio between solution 1b and solution 1c is 3 to 9.

[0060] Subsequently, a mixed solution obtained by mixing solution 1a, solution 1b, and solution 1c is boiled at 120°C for 48 hours (step S10). At this time, the mixed solution containing solution 1a, solution 1b, and solution 1c is heated with stirring. Consequently, the mixed solution containing solution 1a, solution 1b, and solution 1c gels.

[0061] The gelled mixed solution is then dried in an atmosphere at 25°C for 12 hours. This produces a precursor of Fe(Al 1-x Mn x )2O4 is formed (step S12).

[0062] The dried precursor of Fe(Al 1-x Mn x )2O4 is heat-treated (step S14). The heat treatment is carried out in an atmosphere at 300°C for 12 hours. Consequently, organic components in the precursor are removed. Note that the precursor is amorphous after the heat treatment.

[0063] The precursor of Fe(Al 1-x Mn x )2O4 is pre-fired and crystallized. Examples of pre-firing include atmospheric heat treatment.

[0064] More specifically, the heat-treated precursor of Fe(Al 1-x Mn x )2O4 is first placed in a mold and compressed. At this time, uniaxial pressing is performed at a constant pressure of 98 MPa (step S16).

[0065] Afterwards, the compressed precursor of Fe(Al 1-x Mn x )2O4 is pre-fired for two hours at 900°C. At this time, the compressed precursor of Fe(Al 1-x Mn x )2O4 is calcined while releasing N2 gas containing H2 gas in a predetermined amount (step S18). The amount a% of H2 gas is, for example, a = 0, 0.01, 0.03, 0.05, 0.08, 0.1. Consequently, the amorphous precursor of Fe(Al 1-x Mn x)2O4 crystallizes. At this point, trivalent Fe ions Fe 3+ to divalent Fe ions Fe 2+ reduced, and tetravalent Mn ions Mn 4+ become trivalent Mn ions Mn 3+ reduced. Accordingly, the trivalent Mn ions Mn 3+ into the B-position in the structure of ferrite, represented by a general chemical structural formula AB2O4 (where A and B are any metal elements). Consequently, trivalent ions Al 3+ and Mn 3+ into the B-position. Using the previously described process steps, a ferrite Fe(Al 1-x Mn x )2O4 powder with the composition in which part of Al in hercynite FeAl2O4 is replaced by Mn.

[0066] The following is the ferrite Fe(Al 1-x Mn x)2O4 powder is sintered (step S20). Note that examples of sintering include atmospheric heat treatment performed again after a pre-fired precursor is formed by uniaxial pressing, hot pressing, and the like. Hot pressing here refers to a method in which a powder or a pre-formed material is placed in a mold, and the powder or pre-formed material is sintered under pressure while heating the powder or pre-formed material to a high temperature. By hot pressing, not only can a densely packed sintered body with a density close to the theoretical density be obtained, but it is also possible to control the microstructure of a sintered body.Therefore, by hot pressing, it is possible to produce a sintered body with excellent mechanical and physical properties, such as a sintered body with high strength. In addition, hot pressing is characterized by improving interfacial contact between different materials, thereby bonding crystals or different materials, and the like. The present disclosure is not limited to these methods, and another method for sintering an Fe(Al) may be used. 1-x Mn x )2O4 powder. Furthermore, the temperatures and times in the previously described process steps are merely examples, and other temperatures and times may be used.

[0067] Different types of Fe(Al 1-x Mn x )2O4 powders were prepared using the previously described preparation procedure, where the value of x in Fe(Al1-x Mn x )2O4 was changed. The value of x was set to one of seven values ​​of x = 0, 0.2, 0.4, 0.5, 0.6, 0.7, 0.8, where x = 0 is not included in the scope of the invention. Furthermore, the following evaluation was conducted to determine the crystal structure and magnetic properties of each Fe(Al 1-x Mn x )2O4 powder obtained during pre-firing and manufacturing. [4. Evaluation of the crystal structure of ferrite Fe(Al 1-x Mn x )2O 4]

[0068] As previously described, an evaluation of the crystal structure of each Fe(Al 1-x Mn x )2O4, where the value of x was varied as follows: x = 0, 0.2, 0.4, 0.5, 0.6, 0.7, 0.8.

[0069] Fig. 2 to Fig. 7 are each a diagram showing an X-ray diffraction pattern of a product obtained by heat treating a powder corresponding to a composition x = 0, 0.2, 0.4, 0.5, 0.6, 0.7, 0.8 under different gas atmospheres. Fig. Figure 8 is a diagram showing gas atmospheres and X-ray diffraction patterns of Fe(Al 1-x Mn x )2O4, whose crystal structure after heat treatment was a spinel-type crystal structure, in the case of x = 0, 0.2, 0.4, 0.5, 0.6, 0.7, 0.8.

[0070] Fe(Al 1-x Mn x )2O4 in the case of x = 0 corresponds to FeAl2O4 (hercynite). As in Fig. 2, the X-ray diffraction pattern of Fe(Al 1-x Mn x )2O4 in the case of x = 0 the X-ray diffraction pattern of FeAl2O4 with a spinel-type crystal structure.

[0071] In the case of x = 0.2, Fe(Al 1-x Mn x)2O4, while an amount a% of H2 gas introduced into a N2 gas atmosphere in the pre-combustion step was changed as follows: a = 0, 0.01, 0.03, 0.05, 0.08. As in Fig. 3, in the case of a = 0, 0.01, 0.03, peak patterns were observed which correspond to the X-ray diffraction patterns of spinel-type Fe(Al 1-x Mn x )2O4, Al2O3 and Fe3O4. Consequently, it was confirmed that Al2O3 and Fe3O4 in addition to Fe(Al 1-x Mn x )2O4. Furthermore, in the case of a = 0.05, 0.08, peak patterns were observed that resembled the X-ray diffraction patterns of spinel-type Fe(Al 1-x Mn x )2O4. Consequently, it was confirmed that Fe(Al 1-x Mn x )2O4 spinel-type powders had been produced.

[0072] In the case of x = 0.4, Fe(Al 1-x Mn x)2O4, while an amount a% of H2 gas introduced into N2 gas in the pre-combustion step was changed as follows: a = 0, 0.01, 0.03, 0.05, 0.065, 0.08. As in Fig. 4, in the case of a = 0, 0.01, 0.03, 0.065, peak patterns were observed which correspond to the X-ray diffraction patterns of spinel-type Fe(Al 1-x Mn x )2O4, Al2O3 and Fe2O3. Consequently, it was confirmed that Al2O3 and Fe2O3 in addition to Fe(Al 1-x Mn x )2O4. Furthermore, in the case of a = 0.05, peak patterns were observed that resembled the X-ray diffraction patterns of spinel-type Fe(Al 1-x Mn x )2O4, Fe2O3 and FeAl2O4. Consequently, it was confirmed that Fe2O3 and FeAl2O4, in addition to Fe(Al 1-x Mn x )2O4. Furthermore, in the case of a = 0.08, peak patterns were observed that resembled the X-ray diffraction patterns of spinel-type Fe(Al 1-x Mn x)2O4, Fe2O3, FeAl2O4 and MnO. Consequently, it was confirmed that Fe2O3, FeAl2O4 and MnO in addition to Fe(Al 1-x Mn x )2O4 had been produced.

[0073] In the case of x = 0.5, Fe(Al 1-x Mn x )2O4, while an amount a% of H2 gas introduced into N2 gas in the pre-combustion step was changed as follows: a = 0.01, 0.03, 0.05, 0.08, 0.1. As in Fig. 5, in the case of a = 0.01, 0.03, 0.05, peak patterns were observed which correspond to the X-ray diffraction patterns of spinel-type Fe(Al 1-x Mn x )2O4 and Al2O3. Consequently, it was confirmed that Al2O3, in addition to Fe(Al 1-x Mn x )2O4. Furthermore, in the case of a = 0.08, peak patterns were observed that resembled the X-ray diffraction patterns of spinel-type Fe(Al 1-x Mn x )2O4 and MnO. Consequently, it was confirmed that Fe(Al 1-x Mn x)2O4 and MnO. Furthermore, in the case of a = 0.1, peak patterns were observed that resembled the X-ray diffraction patterns of spinel-type Fe(Al 1-x Mn x )2O4 (a theoretical value) and MnO. Consequently, it was confirmed that Fe(Al 1-x Mn x )2O4 and MnO were prepared.

[0074] In the case of x = 0.6, Fe(Al 1-x Mn x )2O4, while an amount a% of H2 gas introduced into N2 gas in the sintering step was changed as follows: a = 0, 0.01, 0.03, 0.05, 0.08. As in Fig. 6, in the case of a = 0, peak patterns were observed that correspond to the X-ray diffraction patterns of spinel-type Fe(Al 1-x Mn x )2O4 and MnFe2O4. Consequently, it was confirmed that MnFe2O4, in addition to Fe(Al 1-x Mn x )2O4. Furthermore, in the case of a = 0.01, a peak pattern was observed that resembled the X-ray diffraction pattern of spinel-type Fe(Al1-x Mn x )2O4. Consequently, it was confirmed that Fe(Al 1-x Mn x )2O4 had been produced.

[0075] Furthermore, in the case of a = 0.03, 0.05, 0.08, peak patterns were observed which resembled the X-ray diffraction patterns of spinel-type Fe(Al 1-x Mn x )2O4 and MnO. Consequently, it was confirmed that Fe(Al 1-x Mn x )2O4 and MnO were prepared.

[0076] In the case of x = 0.8, Fe(Al 1-x Mn x )2O4, while an amount a% of H2 gas introduced into N2 gas in the pre-combustion step was changed as follows: a = 0, 0.01, 0.03, 0.05, 0.08. As in Fig. As shown in Figure 7, in the case of a = 0, 0.01, a peak pattern was observed which resembled the X-ray diffraction pattern of spinel-type Fe(Al 1-x Mn x )2O4. Consequently, it was confirmed that Fe(Al 1-x Mn x)2O4 was formed. Furthermore, in the case of a = 0.03, 0.05, 0.08, peak patterns were observed that resembled the X-ray diffraction patterns of spinel-type Fe(Al 1-x Mn x )2O4 and MnO. Consequently, it was confirmed that Fe(Al 1-x Mn x )2O4 and MnO were prepared.

[0077] In summary, the case where only spinel type Fe(Al 1-x Mn x )2O4 (single phase) was prepared as described in Fig. 8, the value of x in Fe(Al 1-x Mn x )2O4 and the amount a% of H2 gas introduced into N2 gas during pre-firing was set to (x, a) = (0.2, 0.08), (0.6, 0), (0.7, 0), (0.8, 0), (0.9, 0), the peak pattern was observed which was similar to the X-ray diffraction pattern of spinel type Fe(Al 1-x Mn x )2O4. Consequently, it was confirmed that Fe(Al 1-x Mn x)2O4. Furthermore, in the case of (x, a) = (0.2, 0.08), peak patterns were observed that resembled the X-ray diffraction patterns of spinel-type Fe(Al 1-x Mn x )2O4 and FeAl2O4. Consequently, it was confirmed that FeAl2O4, in addition to Fe(Al 1-x Mn x )2O4. Furthermore, in the case of (x, a) = (0,9, 0), peak patterns were observed that resembled the X-ray diffraction patterns of spinel-type Fe(Al 1-x Mn x )2O4 and MnFe2O4. Consequently, it was confirmed that MnFe2O4, in addition to Fe(Al 1-x Mn x )2O4 had been produced.

[0078] Fig. Figure 9A is a table summarizing the products when a value of x and a quantity of H2 are changed. Note that “S” in Fig. 9A indicates that a compound with a spinel-type crystal structure has been formed. In addition, a hatched cell for the combination (x, a) indicates a combination (x, a) for which Fe(Al 1-x Mn x )2O4 of the spinel type has been confirmed.

[0079] In summary, as in Fig. 9A it was found that the production of Fe(Al 1-x Mn x )2O4 of the spinel type in the case of (x, a) = (0.2, 0.05), (0.2, 0.08), (0.6, 0), (0.6, 0.01), (0.7, 0), (0.7, 0.01), (0.8, 0), (0.8, 0.01), (0.9, 0), (0.9, 0.01).

[0080] It is pointed out that as in Fig. 9A, although it was not confirmed that Fe(Al 1-x Mn x )2O4 spinel-type powder was prepared only by heat treatment of a precursor with a composition of x = 0.5 under one atmosphere, it was confirmed that Fe(Al 1-x Mn x)2O4 of the spinel type itself in the case of x = 0.5 had been prepared in the following cases.

[0081] Fig. Figure 9B is a graph showing an X-ray diffraction pattern of a product prepared by current pulse pressure sintering (PECPS) in the case of x = 0.5. Fig. Figure 9C is a graph showing X-ray diffraction patterns of products prepared by current pulse pressure sintering and atmospheric heat treatment in the case of x = 0.5.

[0082] In the case of x = 0.5, a precursor of Fe(Al 1-x Mn x )2O4 was formed at a pressure of 50 MPa, and the precursor was further subjected to current pulse pressure sintering under the condition of 600°C / 10 minutes / 50 MPa / vacuum. An X-ray diffraction pattern of the product at this time was measured, and the Fig. The X-ray diffraction pattern shown in Figure 9B was obtained. In the X-ray diffraction pattern shown in Fig. 9B, a peak pattern was observed that resembled a diffraction pattern of Fe(Al 1-x Mn x )2O4 of the spinel type. Consequently, it was confirmed that Fe(Al 1-x Mn x )2O4 of the spinel type. It should be noted that a sintering process is not limited to current pulse pressure sintering and can be a different sintering process.

[0083] Furthermore, the Fe(Al 1-x Mn x )2O4 spinel-type powder prepared by current pulse pressure sintering was heat-treated at 900°C for two hours under atmospheric pressure. An X-ray diffraction pattern of the product at this time was measured, and the Fig. The X-ray diffraction pattern shown in Figure 9C was obtained. It was found that although the Fig. 9C shows a stronger X-ray diffraction pattern than that shown in Fig. 9B, a part of a crystal phase had separated. Accordingly, in the case of x = 0.5, to form a Fe(Al 1-x Mn x )2O4 powder of the spinel type, it can be said that performing only PECPS is particularly suitable.

[0084] Fig. 10A to Fig. 10G are scanning electron microscopy (SEM) images of agglomerated particles of Fe(Al 1-x Mn x )2O4 powders in the case of x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, 1.0. As in Fig. 10A to Fig. 10G, the particle diameter of the primary particles contained in the agglomerated particles of Fe(Al 1-x Mn x )2O4 are contained, with increasing value of x, as at x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, 1.0.

[0085] Fig. Figure 11 is a diagram showing a relationship between a value of x and a lattice parameter of Fe(Al 1-x Mn x )2O4 shows.

[0086] As in Fig. 11, the lattice parameter of Fe(Al 1-x Mn x )2O4 increases with increasing value of x. It can be said that this is consistent with the result that the primary particles increase with increasing value of x, as in x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, 1.0 in Fig. 10A to Fig. 10G. [5. Evaluation of the magnetic properties of ferrite Fe(Al 1-x Mn x )2O4]

[0087] The magnetic properties of ferrite Fe(Al 1-x Mn x )2O4 described.

[0088] Fig. 12A to Fig. 12F are each a diagram showing the BH properties of Fe(Al 1-x Mn x )2O4 in the case of x = 0, 0.2, 0.6, 0.7, 0.8, 0.9. It is noted that although the scales of the vertical axis and the horizontal axis are shown in Fig. 12A to Fig. 12F are omitted, the size of the scales in Fig. 12A to Fig. 12F is standardized.

[0089] The BH properties show a change in the magnetic flux density (B, represented by the vertical axis) when an external magnetic field (H, represented by the horizontal axis) acts on a material. The BH properties are represented by a line (proportion) for a paramagnetic substance, and by a so-called hysteresis curve for a ferromagnetic substance. Furthermore, a material with a small difference between positive and negative values ​​(coercive field strength H C ) of the external magnetic field H when the magnetic flux density is 0 (a low coercive field strength H C) in the hysteresis curve is called a soft magnetic material, and a material with a large difference between positive and negative values ​​of the external magnetic field H when the magnetic flux density is 0 (a high coercive field strength H C ) in the hysteresis curve is called a hard magnetic material. A material is magnetized more quickly by the external magnetic field if the material has a smaller difference between positive and negative values ​​of H (lower coercive field strength H C ). Accordingly, it can be said that a material has more excellent magnetic properties if the material is soft magnetic.

[0090] In the case of x = 0, ie FeAl2O4 (hercynite) powder, as in Fig. As shown in Figure 12A, the value of B increases with increasing value of H, and the BH properties are represented by a line. FeAl2O4 is a paramagnetic substance, and therefore, the result that the BH properties are represented by a line is understandable.

[0091] Furthermore, with regard to Fe(Al 1-x Mn x )2O4 in the case of x = 0.2, as in Fig. As shown in Figure 12B, the BH properties are represented by a hysteresis curve. Accordingly, it was found that Fe(Al 1-x Mn x )2O4 is a ferromagnetic substance in the case of x = 0.2. It is noted that, with respect to a range 0 < x < 0.2 for the value of x, although it is not possible to Fig. 12A and Fig. 12B that Fe(Al 1-x Mn x )2O4 is a ferromagnetic substance, with regard to Fig. 12B it can be said that Fe(Al 1-x Mn x)2O4 is a ferromagnetic substance, at least in the case of x = 0.2.

[0092] Furthermore, with regard to Fe(Al 1-x Mn x )2O4 in the case of x = 0.6, 0.7, 0.8, 0.9, as in Fig. 12C to Fig. 12F, the BH properties are represented by a hysteresis curve. Accordingly, it was found that Fe(Al 1-x Mn x )2O4 is a ferromagnetic substance in the case of x = 0.6, 0.7, 0.8, 0.9.

[0093] Furthermore, it has been found that a difference between positive and negative values ​​of the external magnetic field H, when the magnetic flux density is 0 in the hysteresis curve, decreases (the coercive field strength H C decreases) as the value of x increases, as in x = 0.2, 0.6, 0.7, 0.8, 0.9, and the hysteresis curve shows the soft magnetism. As a result, it was found that Fe(Al 1-x Mn x)2O4 with more excellent magnetic properties is obtained when the value of x for Fe(Al 1-x Mn x )2O4 is larger.

[0094] It can be concluded that Fe(Al 1-x Mn x )2O4 is a ferromagnetic substance in the case of x ≥ 0.2.

[0095] Fig. 13 is a diagram showing a relationship between a value of x in Fe(Al 1-x Mn x )2O4 and a magnetic mass magnetization σ s (emu / g = A∙m 2 / kg).

[0096] As in Fig. 13, a value of the magnetic mass magnetization σ s when the value of x in Fe(Al 1-x Mn x )2O4 increases. Consequently, it can be said that Fe(Al 1-x Mn x )2O4 with a more excellent magnetization per unit mass is obtained when the value of x is larger. Furthermore, when Fe(Al 1-x Mn x)2O4 is used in a field where high magnetic properties are required, for example, particularly high frequency devices, it is desired that Fe(Al 1-x Mn x )2O4 is a material with an excellent saturation magnetic flux density. There is a close relationship between saturation magnetic flux density and bulk magnetic magnetization, and it is preferable that the bulk magnetic magnetization σ s for example by σ s ≥ 10. Consequently, it is desirable that Fe(Al 1-x Mn x )2O4, whose magnetic mass magnetization σ s the condition σ s ≥ 10 is fulfilled.

[0097] Fig. 14 is a diagram showing a relationship between a value of x in Fe(Al 1-x Mn x )2O4 and a magnetic saturation flux density B S shows.

[0098] As in Fig. 14, a value of the magnetic saturation flux density B S to when the value of x in Fe(Al 1-x Mn x )2O4 increases. Consequently, it can be said that Fe(Al 1-x Mn x )2O4 with a more excellent magnetic saturation flux density B S if the value of x is larger.

[0099] Fig. 15 is a diagram showing a relationship between a value of x in Fe(Al 1-x Mn x )2O4 and a coercive field strength H C It is noted that the coercive field strength (vertical axis) in Fig. 15 is plotted logarithmically.

[0100] As in Fig. 15, the coercive field strength H C (Oe = 10^3 / (4π) A / m) with increasing value of x in Fe(Al 1-x Mn x )2O4. It can be said that this means that Fe(Al 1-x Mn x)2O4 becomes further soft magnetized as the value of x increases. The coercive field strength H C shows the minimum value when the value of x is approximately 0.8. The coercive field strength H C increases again when the value of x exceeds 0.8. Consequently, it can be said that when the value of x is approximately 0.8, Fe(Al 1-x Mn x )2O4 with the best soft magnetism and with the best coercive field strength H C is received.

[0101] Fig. 16 is a table showing a relationship between values ​​of x in Fe(Al 1-x Mn x )2O4 and structures and magnetic properties of Fe(Al 1-x Mn x )2O4.

[0102] As in Fig. 16, in the case of x = 0.2, a solid solution of Fe(Al 1-x Mn x )2O4 was successfully produced for the first time using the previously described production method.

[0103] Furthermore, although a single phase was not obtained by heat treatment at normal temperature in the case of x = 0.4 or 0.5, a single-phase powder was successfully prepared, for example, by current pulse pressure sintering in the case of x = 0.5. Furthermore, also in the case of x = 0.6, 0.7, 0.8, 0.9, a solid solution of Fe(Al 1-x Mn x )2O4 was successfully produced for the first time using the previously described production method.

[0104] As described, Fe(Al 1-x Mn x )2O4, prepared using the previously described method, is a ferrite with a new composition and exhibits ferromagnetism. Fe(Al 1-x Mn x )2O4, for example, has a magnetic saturation flux density B S in a range of approximately 0.06 to 0.11 [T], and for example a coercive field strength H Cin a range of 1114.08 [A / m] to 1432.39 [A / m] (14 to 18 [Oe]). Furthermore, it has been assessed that the value of x in Fe(Al 1-x Mn x )2O4, if Fe(Al 1-x Mn x )2O4 has the best magnetic properties, for example, 0.8, and at this time the magnetic saturation flux density B S and the coercive field strength H C 0.098 [T] and 1114.08 [A / m] (14 [Oe]) respectively.

[0105] According to the magnetic material and the method for producing the same according to the embodiment, since it is possible to introduce Mn into the same position where Al of hercynite FeAl2O4 is introduced, a magnetic ferrite material represented by the chemical structural formula Fe(Al 1-x Mn x )2O4 can be easily prepared. Consequently, it is possible to produce a magnetic ferrite material Fe(Al 1-x Mn x)2O4 with high magnetic properties.

[0106] Although the magnetic material and the method for producing the same according to the embodiment of the present disclosure have been described above, the present disclosure is not limited to the embodiment.

[0107] For example, a sintering process is not limited to the hot pressing described above, and other processes such as current pulse pressure sintering can be used. Furthermore, the temperatures and times in the previously described process steps are merely examples, and other temperatures and times may be used.

[0108] Furthermore, the solution 1a, the solution 1b and the solution 1c may be mixed together at the same time, or, for example, a mixed solution obtained by mixing the solution 1b and the solution 1c may be prepared, and the mixed solution may then be further mixed with the solution 1a.

[0109] Furthermore, although Fe(Al 1-x Mn x )2O4 in the above-described embodiment is prepared by a liquid phase process in which solution 1a, solution 1b and solution 1c are mixed together, Fe(Al 1-x Mn x )2O4 can be produced using the solid phase method.

[0110] A magnetic material according to the present disclosure can be used for inductors for high frequency, magnetic cores for transformers and the like. [List of reference characters] 1a Solution (mixed aqueous solution) 1b Solution (citric acid) 1c solution (ethylene glycol)

Claims

[1] A magnetic material characterized by a chemical structural formula Fe(Al 1-x Mn x )2O4, where 0 < x < 1, and which exhibits ferromagnetism, and where a range of a value of x is represented by x ≥ 0.

2. [2] The magnetic material according to claim 1, wherein a range of a value of the magnetic mass magnetization σ s [A·m 2 / kg] of the magnetic material by σ s ≥ 10 is shown. [3] The magnetic material according to any one of claims 1 or 2, wherein the magnetic material comprises manganese dioxide MnO2 as a raw material. [4] Method for producing a magnetic material, where the magnetic material has a chemical structural formula Fe(Al 1-x Mn x )2O4, where 0 < x < 1, and shows ferromagnetism, the manufacturing process comprising: preparing a mixed aqueous solution by dissolving, in distilled water, Fe nitrate, Al nitrate and an oxide containing Mn, wherein the Fe nitrate, the Al nitrate and the oxide are starting materials; preparing a metal-citric acid complex by mixing citric acid and ethylene glycol with the mixed aqueous solution; obtaining a precursor by boiling the metal-citric acid complex to a gel and drying the gel; and obtaining the magnetic material by sintering the precursor. [5] The manufacturing method according to claim 4, wherein, in obtaining the magnetic material, a trivalent Fe ion and a tetravalent Mn ion are respectively reduced to a divalent Fe ion and a trivalent Mn ion. [6] Manufacturing process according to claim 4 or 5, where the Fe nitrate is iron(III) nitrate nonahydrate Fe(NO3)3 9H2O, the Al nitrate is aluminum(III) nitrate·nonahydrate Al(NO3)2·9H2O, and the oxide containing Mn is manganese dioxide MnO2. [7] The manufacturing method according to any one of claims 4 to 6, wherein, in manufacturing the metal-citric acid complex, a molar ratio of a metal ion, the citric acid and the ethylene glycol in the mixed aqueous solution is 1:3:9.

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