TW202408969A - Ferrite particles and method for producing ferrite particles - Google Patents

Abstract

The present invention relates to ferrite particles containing molybdenum. The present invention also relates to a method for producing the ferrite particles, the method including firing a metal compound and an iron compound in the presence of a molybdenum compound.

Description

Ferrite particles and method for producing ferrite particles

The present invention relates to ferrite particles and a method for producing ferrite particles.

Ferrite is a complex oxide mainly containing iron _oxide ( _Fe2O3 ), and is mainly used as a magnetic material in various fields. In recent years, with the overcrowding of the electromagnetic environment in motor vehicles (e.g., cars) caused by the increase in the use of electronic devices in motor vehicles, the demand for noise suppression boards has continued to increase. Although noise suppression boards are currently mainly used for vehicle navigation and car cameras, there is also an expectation that there will be demand for millimeter wave radars in the future. In the telecommunications field, with the transition to the 5th generation Mobile Communication Technology (5G), the demand for high shielding effectiveness in noise suppression boards used in smartphones is also increasing.

Patent Document 1 discloses a method for producing hexagonal ferrite powder in which an aqueous solution containing a hexagonal ferrite precursor is heated to 300°C or higher and pressurized to 20 MPa or higher to convert the precursor into hexagonal ferrite, thereby obtaining ferrite represented by the general formula AFe ₁₂ O ₁₉ . It is also disclosed that A in the general formula is a divalent metal atom, and the divalent metal atom is a metal atom that can be a divalent cation as an ion and includes an alkaline earth metal atom (eg, barium, strontium, calcium, and lead).

Patent document 2 discloses a method for producing hexagonal ferrite magnetic powder, in which a raw material mixture containing a glass-forming component and a hexagonal ferrite-forming component is melted, the obtained molten material is quenched to obtain a solid, and the obtained solid is subjected to a heat treatment to precipitate hexagonal ferrite magnetic particles and a glass component. Citation list Patent document

Patent Document 1: Japanese Unexamined Patent Application Publication No. 2016-222517 Patent Document 2: Japanese Unexamined Patent Application Publication No. 2020-100561

[Technical Issue]

However, conventional knowledge about ferrite particles and the methods used to make ferrite particles is limited and there is still room for further research. In addition, traditional methods for making ferrite particles usually use a wet process or sol-gel reaction, and it is difficult to control the particle size in the wet process or sol-gel reaction. And it is therefore difficult to obtain ferrite particles having a specific particle size or a specific particle size distribution by applying conventional methods.

The present invention is made to solve the above-mentioned problem, and its purpose is to provide a ferrite particle having excellent properties and a method for producing ferrite particles that can easily produce ferrite particles. [Solution to the problem]

The inventor of the present invention has conducted careful research to solve the subject and found that ferrite particles can be easily produced by dry mixing using a molybdenum compound as a flux and ferrite particles containing molybdenum can be easily produced, thereby completing invention. Specifically, the present invention has the following aspects.

[1] A ferrite particle containing molybdenum.

[2] The ferrite particles as described in [1] above, wherein the ferrite particles have a spinel structure.

[3] The ferrite particles as described in [2] above, wherein the spinel structure is represented by the _{formula AFe2O4} , wherein A is one or more elements selected from Ni, Mn, Cu, Zn, Mg, Ca and Co.

[4] The ferrite particles as described in [1] or [2] above, wherein the molybdenum content in the ferrite particles is 0.1 mass% to 30 mass%, and the molybdenum content in the ferrite particles is It is the content in MoO ₃ (Mo ₁ ) relative to 100 mass % of ferrite particles determined by X-ray fluorescence (XRF) analysis of ferrite particles.

[5] The ferrite particles as described in [1] or [2] above, wherein the molybdenum content in the surface layer of the ferrite particles is 2.0 mass % to 95.0 mass %, wherein the molybdenum content in the surface layer of the ferrite particles is the content (Mo ₂ ) in terms of MoO ₃ relative to 100 mass % of the surface layer of the ferrite particles determined by performing X-ray photoelectron spectroscopy (XPS) surface analysis on the ferrite particles.

[6] The ferrite particles as described in [1] or [2] above, wherein molybdenum is confined in the surface layer of the ferrite particles.

[7] The ferrite particles as described in [1] or [2] above, wherein the molybdenum surface layer localization ratio ( _Mo2 / _Mo1 ) is 1.0 to 80.0, wherein the molybdenum surface layer localization ratio is the ratio of the content (Mo2) calculated as MoO3 in the surface layer of the ferrite particles relative to 100 mass% determined by performing X-ray photoelectron spectroscopy ( _XPS ) surface analysis on the ferrite particles to the content ( _Mo1 ) calculated as _MoO3 in the surface layer of the ferrite particles relative to 100 mass% determined by performing _XRF analysis on the ferrite particles.

[8] The ferrite particles as described in [1] or [2] above, wherein the average particle size of the primary particles of the ferrite particles is 0.1 μm to 100 μm.

[9] The ferrite particles as described in [1] or [2] above, wherein the ferrite particles have a property measured by the Brunauer-Emmett-Teller (BET) method The specific surface area is 0.1 m2/g to 2.5 m2/g.

[10] A method for producing the ferrite particles described in [1], the method comprising: sintering a metal compound and an iron compound in the presence of a molybdenum compound.

[11] The method for producing ferrite particles as described in [10] above, which method includes firing a metal compound and an iron compound in the presence of a molybdenum compound and further adding a zinc compound.

[12] The method for producing ferrite particles as described in [10] or [11] above, wherein the molybdenum compound is selected from the group consisting of molybdenum trioxide, lithium molybdate, potassium molybdate and sodium molybdate. at least one compound in the group.

[13] The method for producing ferrite particles as described in [10] or [11] above, wherein the firing temperature during firing is 800°C to 1,500°C. [Beneficial effects of the invention]

The present invention can provide ferrite particles having excellent properties and a method for producing ferrite particles that can be easily produced.

The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

＜＜Ferrite particles＞＞ The ferrite particles of this example contain molybdenum. The ferrite particles of this example contain molybdenum and have excellent properties, such as magnetism derived from molybdenum. The ferrite particles of this embodiment may also have excellent properties of controlled particle shape. The ferrite particles of this embodiment may also have excellent properties of low or no cohesion.

The ferrite particles of this example may contain molybdenum obtained from the molybdenum compound used in the production method described below. The particle shape of the ferrite particles to be produced can be controlled by using a molybdenum compound in the production method described below.

Regarding the molybdenum contained in the ferrite particles of this embodiment, the existence state and amount of the molybdenum are not limited to specific ones, and the molybdenum may be contained in the ferrite particles as molybdenum metal, molybdenum oxide, partially reduced molybdenum compound, etc. Molybdenum is considered to be contained in the ferrite particles as MoO ₃ , but may be contained in the ferrite particles as MoO ₂ , MoO, etc. instead of MoO ₃ .

The inclusion form of molybdenum is not limited to a specific form. Molybdenum may be included in a form adhering to the surface of the ferrite particles, in a form of a substitution part of the crystal structure of the ferrite particles, in an amorphous state, or in a combination of these forms.

Therefore, the ferrite particles of the present embodiment may contain molybdenum and, specifically, may contain molybdenum obtained from a molybdenum compound used in the preparation method described below, and thus, it is expected that the magnetic performance can be improved compared to the magnetic performance of conventional ferrite particles.

In this specification, controlling the particle shape of ferrite particles means that the particle shape of the produced ferrite particles is not amorphous. In this specification, ferrite particles with controlled particle shape means ferrite particles whose particle shape is not amorphous. The ferrite particles of this embodiment may have a polygonal shape. The ferrite particles of this embodiment have a controlled crystal shape and may have a polygonal eumorphic shape. The ferrite particles with controlled crystal shape can be produced by the production method described below.

The aggregate (powder) of ferrite particles may contain ferrite particles of any shape other than a polygonal shape in any state. The content of polygonal-shaped ferrite particles is preferably 80% or more, more preferably 90% or more, relative to the total amount of aggregates (powder) of ferrite particles by weight or by number. %, and even better is 95% or greater. Scanning electron microscopy (SEM) can be used to determine the morphology of the ferrite particles.

For the ferrite particles of this embodiment, the particle size and molybdenum content of the ferrite particles to be obtained can be controlled by controlling the amount and type of the molybdenum compound used in the preparation method described below, the firing temperature, etc.

The average particle size of the primary particles of the ferrite particles of this embodiment may be 0.1 μm to 100 μm, 0.1 μm to 50 μm, 1.0 μm to 40 μm, or 1.5 μm to 30 μm.

Regarding the average particle size of primary particles of ferrite particles, ferrite particles were photographed using a scanning electron microscope (SEM), and for particles that are the smallest unit on a two-dimensional image (i.e., primary particles), the average value of the maximum length measured among the distances between two points on the outlines of 50 randomly selected primary particles was adopted.

The median diameter D ₅₀ calculated by performing laser diffraction and scattering on the ferrite particles of this embodiment may be 0.5 micron to 50 micron, 1 micron to 40 micron, or 1.5 micron to 35 micron.

In the particle size distribution measured in dry form using a laser diffraction particle size analyzer, the median diameter D ₅₀ calculated by laser diffraction and scattering of the ferrite particles can be determined as The cumulative volume percentage is proportional to 50% of the particle size.

The specific surface area of the ferrite particles of this embodiment determined by the BET method may be 0.1 m2/g to 2.5 m2/g, 0.15 m2/g to 2.5 m2/g, 0.1 m2/g to 2.0 m2/g, or 0.2 m2/g to 2.0 m2/g.

The specific surface area is measured using a specific surface area meter (e.g., BELSORP-mini manufactured by Microtrac Bell Corporation), and the surface area per gram of the sample measured from the adsorption amount of nitrogen by the Bronnauer-Emmett-Teller method (BET method) is calculated as the specific surface area (m2/g).

The ferrite particles of this embodiment contain ferrite. Although the ferrite particles can adopt various crystal structures (for example, spinel structure and garnet structure), in this embodiment, it is preferred to have a spinel structure. The _spinel structure is represented by _AFe2O4 , for example (where A is one or more elements selected from Ni, Mn, Cu, Zn, Mg, Ca and Co). The _spinel structure is usually represented by _AFe2O4 (where A is one or two elements selected from Ni, Mn, Cu, Zn, Mg, Ca and Co).

Relative to 100 mass % of ferrite particles, the ferrite particles of this embodiment preferably contain AFe ₂ O ₄ in an amount of 65 mass % to 99.95 mass %, and more preferably in an amount of 70 mass % to 99.5 mass %. AFe ₂ O _{4 is} contained _in an amount of 90 to 99 mass %.

The ferrite particles may contain nickel. The nickel content in the ferrite particles can be measured by X-ray fluorescence (XRF) analysis. The nickel content in the ferrite particles of the present embodiment (the content (Ni ₁ ) in terms of NiO relative to 100% by mass of the ferrite particles determined by performing XRF analysis on the ferrite particles) is preferably 5% by mass to 50% by mass, more preferably 10% by mass to 40% by mass, and even more preferably 15% by mass to 30% by mass.

The iron content contained in ferrite particles can be measured by XRF analysis. The iron content in the ferrite particles of this example (the content in terms of Fe ₂ O ₃ (Fe ₁ ) relative to 100% by mass of the ferrite particles determined by XRF analysis of the ferrite particles) is relatively Preferably it is 35 mass% to 80 mass%, more preferably 40 mass% to 75 mass%, and even more preferably 45 mass% to 70 mass%.

The molybdenum content contained in the ferrite particles can be measured by XRF analysis. The molybdenum content in the ferrite particles of the present embodiment (the content (Mo ₁ ) calculated as MoO ₃ relative to 100% by mass of the ferrite particles determined by performing XRF analysis on the ferrite particles) is preferably 0.1% by mass or more, more preferably 0.1% by mass to 30% by mass, more preferably 0.5% by mass to 25% by mass, and even more preferably 0.75% by mass to 20% by mass.

The upper limits and lower limits of the above-exemplified contents (Ni ₁ ), (Fe ₁ ) and (Mo ₁ ) in the ferrite particles of this embodiment can be freely combined. The corresponding values of the contents (Ni ₁ ), (Fe ₁ ) and (Mo ₁ ) can also be freely combined.

When the spinel structure is represented by NiFe ₂ O ₄ , examples of the ferrite particles of the present embodiment may be ferrite particles having a content (Ni ₁ ) of 15 to 45 mass %, a content (Fe ₁ ) of 35 to 75 mass %, and a content (Mo ₁ ) of 0.1 to 30 mass % relative to 100 mass % of the ferrite particles as determined by performing XRF analysis on the ferrite particles; and ferrite particles having a content (Ni 1 ) of 17.5 to 40 mass %, a content (Fe ₁ ) of 40 to 70 mass %, and a content (Mo ₁ ) of 0.5 to 25 mass % relative to 100 mass % of the ferrite particles as determined _by performing XRF analysis on the ferrite particles. ) ferrite particles; or ferrite particles having a content of (Ni ₁ ) of 20 to 35 mass %, a content of (Fe ₁ ) of 45 to 65 mass %, and a content of (Mo ₁ ) of 0.75 to 20 mass % relative to 100 mass % of the ferrite particles as determined by performing XRF analysis on the ferrite particles.

The ferrite particles may further contain zinc. The zinc content in the ferrite particles may be measured by XRF analysis. The zinc content in the ferrite particles of the present embodiment (the content ( _Zn1 ) calculated as _ZnO2 relative to 100% by mass of the ferrite particles determined by performing XRF analysis on the ferrite particles) is preferably 0.5% by mass to 25% by mass, more preferably 0.75% by mass to 20% by mass, and even more preferably 0.1% by mass to 15% by mass.

The corresponding upper limit values and the corresponding lower limit values of the above-exemplified content (Ni ₁ ), content (Fe ₁ ), content (Zn ₁ ), and content (Mo ₁ ) in the ferrite particles of this embodiment can be mutually exclusive. Free combination. The corresponding values of the content (Ni ₁ ), the content (Fe ₁ ), the content (Zn ₁ ) and the content (Mo ₁ ) can also be freely combined with each other.

When the spinel structure is represented by NiFe ₂ O ₄ , an example of the ferrite particles of the present embodiment may be one having 10% by mass relative to 100% by mass of the ferrite particles as determined by performing XRF analysis on the ferrite particles. Content of mass % to 40 mass % (Ni ₁ ), 45 mass % to 60 mass % content (Fe ₁ ), 0.5 mass % to 20 mass % content (Zn ₁ ), and 0 mass % to 5 mass % content Ferrite particles of (Mo ₁ ); having a content of 12.5 to 35 mass % (Ni ₁ ) and 47.5 mass % relative to 100 mass % of ferrite particles as determined by XRF analysis of the ferrite particles % to 57.5 mass% (Fe ₁ ), 0.75 to 17.5 mass% (Zn ₁ ), and 0.1 to 3 mass% (Mo ₁ ) ferrite particles; or by The ferrite particles were determined by XRF analysis to have a content of 15% to 30% by mass (Ni ₁ ), a content of 50% to 55% by mass (Fe ₁ ), and 1.0% by mass relative to 100% by mass of ferrite particles. % to 15% by mass (Zn ₁ ) and 0.5% to 2.5% by mass (Mo ₁ ).

The ferrite particles may contain manganese instead of nickel. The manganese content contained in ferrite particles can be measured by XRF analysis. The manganese content in the ferrite particles of this embodiment (the content in MnO ₂ based on 100 mass % of the ferrite particles determined by XRF analysis of the ferrite particles (Mn ₁ )) is preferably: 10 to 60 mass%, more preferably 20 to 50 mass%, and even more preferably 30 to 40 mass%.

The corresponding upper limit values and the corresponding lower limit values of the above-exemplified content (Mn ₁ ), content (Fe ₁ ), and content (Mo ₁ ) in the ferrite particles of this embodiment can be freely combined with each other. The corresponding values of content (Mn ₁ ), content (Fe ₁ ) and content (Mo ₁ ) can also be freely combined with each other.

When the spinel structure is represented by MnFe ₂ O ₄ , examples of the ferrite particles of the present embodiment may be ferrite particles having a content (Mn ₁ ) of 10 to 60 mass %, a content (Fe _{1 ) of 30 to 80 mass %, and a content (Mo 1 )} of 0 mass % relative to 100 mass % of the ferrite particles as determined by performing XRF analysis on the ferrite particles; and ferrite particles having a content (Mn 1 ) of 20 to 50 mass %, a content (Fe ₁ ) of 40 to 75 mass %, and a content (Mo ₁ ) of 0 mass % relative to 100 mass % of the ferrite particles as determined _by performing XRF analysis on the ferrite particles. ) ferrite particles; or ferrite particles having a content of (Mn ₁ ) of 30 to 40 mass %, a content of (Fe ₁ ) of 50 to 70 mass %, and a content of (Mo ₁ ) of 0 mass % relative to 100 mass % of the ferrite particles as determined by performing XRF analysis on the ferrite particles.

For XRF analysis, an X-ray fluorescence analyzer (eg, Primus IV manufactured by Rigaku Corporation) may be used.

The content in NiO (Ni ₁ ) refers to the value of the nickel content determined by performing XRF analysis on ferrite particles from the NiO amount converted using a calibration line in NiO.

The content in terms of Fe ₂ O ₃ (Fe ₁ ) refers to the iron content determined by performing XRF analysis on ferrite particles from the amount of Fe ₂ O ₃ converted using a calibration line in terms of Fe ₂ O ₃ value.

The content in terms of MoO ₃ (Mo ₁ ) refers to a value of the molybdenum content determined from the amount of MoO ₃ converted using a calibration line in terms of MoO ₃ , determined by performing XRF analysis on ferrite particles.

The content in ZnO ₂ (Zn ₁ ) refers to the value of the zinc content determined by performing XRF analysis on ferrite particles from the ZnO ₂ amount converted using a calibration line in ZnO ₂ .

The content in MnO ₂ (Mn ₁ ) refers to the value of the manganese content determined by performing XRF analysis on ferrite particles from the amount of MnO ₂ converted using a calibration line in MnO ₂ .

The nickel content contained in the surface layer of the ferrite particles can be measured by X-ray photoelectron spectroscopy (XPS) surface analysis. The nickel content in the surface layer of the ferrite particles of the present embodiment (the content (Ni _{2 )} in terms of NiO relative to 100% by mass of the surface layer of the ferrite particles determined by performing XPS surface analysis on the ferrite particles) is preferably 0% by mass to 65% by mass, more preferably 0% by mass to 60% by mass, and even more preferably 0% by mass to 55% by mass.

The iron content contained in the surface layer of the ferrite particles can be measured by X-ray photoelectron spectroscopy (XPS) surface analysis. The iron content in the surface layer of the ferrite particles of the present embodiment (the content (Fe 2 ) in terms of Fe ₂ O ₃ relative to 100% by mass of the surface layer of the ferrite particles determined by performing XPS surface analysis on the _ferrite particles) is preferably 5% by mass to 65% by mass, more preferably 10% by mass to 60% by mass, and even more preferably 12.5% by mass to 57.5% by mass.

The molybdenum content contained in the surface layer of the ferrite particles can be measured by X-ray photoelectron spectroscopy (XPS) surface analysis. The molybdenum content in the surface layer of the ferrite particles of the present embodiment (the content (Mo ₂ ) in terms of MoO ₃ relative to 100% by mass of the surface layer of the ferrite particles determined by performing XPS surface analysis on the ferrite particles) is preferably 1% by mass or more, preferably 2.0% by mass to 95% by mass, more preferably 2.5% by mass to 90% by mass, and even more preferably 3.0% by mass to 87.5% by mass.

The upper limits and lower limits of the above-mentioned contents (Ni ₂ ), (Fe ₂ ) and (Mo ₂ ) in the ferrite particles of this embodiment can be freely combined with each other. The corresponding values of the contents (Ni ₂ ), (Fe ₂ ) and (Mo ₂ ) can also be freely combined with each other.

When the spinel structure is represented by NiFe ₂ O ₄ , an example of the ferrite particles of the present embodiment may be the value determined by performing XPS surface analysis on the ferrite particles relative to 100 mass % of the ferrite particles. The surface layer has ferrite particles with a content of 0% to 60% by mass (Ni ₂ ), a content of 5% to 65% by mass (Fe ₂ ), and a content of 2.5% to 90% by mass (Mo ₂ ); The surface layer of the ferrite particles, as determined by performing XPS surface analysis on the ferrite particles, has a content of 3 to 57.5 mass % (Ni ₂ ) and 10 to 60 mass %, relative to 100 mass % of the ferrite particles. Ferrite particles with a content (Fe ₂ ) and a content (Mo ₂ ) of 5% by mass to 87.5% by mass; or determined by performing XPS surface analysis on the ferrite particles relative to 100% by mass of the ferrite particles The surface layer has ferrite particles with a content of 5% to 55% by mass (Ni ₂ ), a content of 12.5% to 55% by mass (Fe ₂ ), and a content of 7.5% to 85% by mass (Mo ₂ ) .

As mentioned above, the ferrite particles may further contain zinc. The zinc content contained in ferrite particles can be measured by X-ray photoelectron spectroscopy (XPS) surface analysis. The zinc content in the surface layer of the ferrite particles of this example (the content in ZnO ₂ relative to the surface layer of 100 mass % of the ferrite particles determined by performing XPS surface analysis on the ferrite particles) ( Zn ₂ )) is preferably 0.1 mass% to 10 mass%, more preferably 0.25 mass% to 8 mass%, and even more preferably 0.5 mass% to 6 mass%.

The corresponding upper limit values and the corresponding lower limit values of the above-exemplified content (Ni ₂ ), content (Fe ₂ ), content (Zn ₂ ), and content (Mo ₂ ) in the ferrite particles of this embodiment can be mutually exclusive. Free combination. The corresponding values of content (Ni ₂ ), content (Fe ₂ ), content (Zn ₂ ) and content (Mo ₂ ) can also be freely combined with each other.

When the spinel structure is represented by _NiFe2O4 , examples of the ferrite particles of the present embodiment may be ferrite particles having a content of ( _Ni2 ) of 0.5 to 25 mass%, a content of ( _Fe2 ) of 20 to 70 mass%, a content of ( _Zn2 ) of 0.1 to 10 mass%, and a content of ( _Mo2 ) of 20 to 75 mass% relative to 100 mass% of the surface layer of the ferrite particles determined by performing XPS surface analysis on the ferrite particles; and a content of ( _Ni2 ) of 1.0 to 20 mass%, a content of ( _Fe2 ) of 25 to 65 mass%, relative to 100 mass% of the surface layer of the ferrite particles determined by performing XPS surface analysis on the ferrite _particles . ), 0.25 mass % to 8 mass % (Zn ₂ ) and 25 mass % to 70 mass % (Mo ₂ ) of a ferrite particle; or a ferrite particle having a content of (Ni ₂ ) of 1.5 mass % to 10 mass %, a content of (Fe ₂ ) of 30 mass % to 60 mass %, a content of (Zn 2 ) of 0.5 mass % to 6 mass % and a content of (Mo ₂ ) of 30 mass % to 65 mass % relative to 100 mass % of the ferrite particle's surface layer as determined _by performing XPS surface analysis on the ferrite particle.

When the ferrite particles contain manganese in place of nickel, the manganese content contained in the ferrite particles can be measured by X-ray photoelectron spectroscopy (XPS) surface analysis. The content in the surface layer of the ferrite particles of the present embodiment (the content (Mn ₂ ) in terms of MnO ₂ relative to 100% by mass of the surface layer of the ferrite particles determined by performing XPS surface analysis on the ferrite particles) is preferably 10% to 80% by mass, more preferably 20% to 70% by mass, and even more preferably 30% to 60% by mass.

The upper limits and lower limits of the above-mentioned contents (Mn ₂ ), (Fe ₂ ) and (Mo ₂ ) in the ferrite particles of this embodiment can be freely combined. The corresponding values of the contents (Mn ₂ ), (Fe ₂ ) and (Mo ₂ ) can also be freely combined.

When the spinel structure is represented by MnFe ₂ O ₄ , an example of the ferrite particles of the present embodiment may be relative to 100 mass % of the ferrite particles determined by performing XPS surface analysis on the ferrite particles. The surface layer has ferrite particles with a content of 10 to 80 mass% (Mn ₂ ), a content of 5 to 75 mass% (Fe ₂ ), and a content of 10 to 95 mass% (Mo ₂ ); The surface layer of the ferrite particles, as determined by performing XPS surface analysis on the ferrite particles, has a content (Mn ₂ ) of 20 mass % to 70 mass % and 7.5 mass % to 65 mass % relative to 100 mass % of the ferrite particles. Ferrite particles with a content (Fe ₂ ) and a content (Mo ₂ ) of 12.5% by mass to 90% by mass; or determined by performing XPS surface analysis on the ferrite particles relative to 100% by mass of the ferrite particles The surface layer has ferrite particles with a content of 30% to 60% by mass (Mn ₂ ), a content of 10% to 60% by mass (Fe ₂ ), and a content of 15% to 87.5% by mass (Mo ₂ ) .

For XPS analysis, a scanning X-ray photoelectron spectrometer (such as the QUANTERA SXM manufactured by ULVAC Phi, Inc.) can be used.

Content (Ni ₂ ) is determined by performing XPS surface analysis on ferrite particles through X-ray photoelectron spectroscopy (XPS) to obtain the presence ratio (atomic %) of the corresponding element and determine the nickel content in terms of oxides It is the value of the NiO content in the surface layer of ferrite particles relative to 100% by mass.

The content (Fe ₂ ) refers to the value determined as the content of Fe 2 O 3 in the surface layer of the ferrite particles relative to 100 mass % by performing _XPS surface analysis on the _ferrite particles to obtain the existence ratio (atomic %) of the corresponding element and determine the iron content in terms of oxide.

Content (Mo ₂ ) is determined by performing XPS surface analysis on ferrite particles through X-ray photoelectron spectroscopy (XPS) to obtain the presence ratio (atomic %) of the corresponding element and determine the molybdenum content in oxide terms. It is the value of the MoO ₃ content in the surface layer of ferrite particles relative to 100% by mass.

The content (Mn ₂ ) refers to the value determined as the MnO 2 content of the surface layer of the ferrite particles relative to 100 mass % by performing XPS surface analysis on the ferrite particles to obtain the existence ratio (atomic %) of the corresponding element and determine the _manganese content in terms of oxide.

In the ferrite particles of this embodiment, molybdenum is preferably localized in the surface layer of the ferrite particles.

The “surface layer” in this specification refers to a region within 10 nanometers on the surface of the ferrite particles in this embodiment. This distance corresponds to the XPS detection depth used for measurements in the example.

"Confined to the surface layer" refers to a state in which the mass of molybdenum or molybdenum compounds per unit volume in the surface layer is greater than the mass of molybdenum or molybdenum compounds per unit volume outside the surface layer.

In the ferrite particles of the present embodiment, the fact that molybdenum is localized in the surface layer of the ferrite particles can be confirmed by the fact that the molybdenum content (Mo ₂ ) calculated as MoO ₃ of the surface layer of the ferrite particles relative to 100 mass % determined by performing XPS surface analysis on the ferrite particles is greater than the molybdenum content (Mo ₁ ) calculated as MoO ₃ of the ferrite particles relative to 100 mass % determined by performing X-ray fluorescence (XRF) analysis on the ferrite particles, as shown in the examples described below.

In the ferrite particles of the present embodiment, as a sign that molybdenum is localized in the surface layer of the ferrite particles, the ferrite particles of the present embodiment have a molybdenum surface layer localization ratio (Mo ₂ /Mo ₁ ), which is a ratio of the content (Mo 2 ) calculated as MoO 3 of the surface layer of the ferrite particles relative to 100 mass % to the content (Mo ₁ ) calculated as MoO ₃ of the ferrite particles relative to 100 mass % determined by performing XPS surface analysis on the ferrite particles, preferably 1.0 to 80, more preferably _3.0 to 60, and even more preferably 5.0 to ₅₀ .

By confining molybdenum or a molybdenum compound in the surface layer of ferrite particles, superior properties (for example, catalytic activity) can be imparted more efficiently than when molybdenum or a molybdenum compound is uniformly present not only in the surface layer but also in the outer layer (inner layer).

The ferrite particles of this embodiment can be provided as aggregates of ferrite particles, and for the above-mentioned values of nickel content, iron content, and molybdenum content, for example, values determined using aggregates as samples can be used. Similarly, for the values of nickel content, iron content, zinc content and molybdenum content mentioned above, the values determined using aggregates as samples can be used. In addition, for the values of manganese content, iron content and molybdenum content described above, values determined using aggregates as samples can be used.

In addition to molybdenum, the ferrite particles of this embodiment may further contain lithium, potassium or sodium.

＜Method for producing ferrite particles＞ The method for producing ferrite particles in this embodiment includes firing a metal compound and an iron compound in the presence of a molybdenum compound. More specifically, the manufacturing method of this embodiment is a method for manufacturing ferrite particles, and may include mixing a metal compound, an iron compound, and a molybdenum compound together to prepare a mixture and firing the mixture.

Compared with the case where the molybdenum compound is not used, by firing the metal compound and the iron compound in the presence of the molybdenum compound, the formation reaction efficiency of the ferrite particles can be improved. Therefore, high-quality ferrite particles with reduced impurity content can be efficiently produced, and in addition, ferrite particles with a low degree of cohesion can be easily produced.

As the metal compound, there can be used a metal compound containing any element selected from Ni, Mn, Cu, Zn, Mg, Ca, and Co. Examples of the metal compound include nickel compounds, manganese compounds, copper compounds, zinc compounds, magnesium compounds, calcium compounds, and cobalt compounds.

By calcining metal compounds and iron compounds in the presence of molybdenum compounds and further adding zinc compounds, a specific proportion of paramagnetic substances is added, thereby appropriately reducing the magnetic properties of the A site and increasing the magnetism obtained from the A-B site interaction.

The case of using a compound containing molybdenum and nickel (for example, nickel molybdate) is also considered as the case of using a molybdenum compound and a nickel compound.

The method for producing ferrite particles of this embodiment can easily produce the ferrite particles of the above-mentioned embodiments.

A preferred method for producing ferrite particles includes: a step of mixing a metal compound containing any element selected from Ni, Mn, Cu, Zn, Mg, Ca and Co, an iron compound and a molybdenum compound to produce a mixture (mixing step); and a step of firing the mixture (firing step). The following is an example of using a nickel compound as an example of a metal compound.

[Mixing step] The mixing step is a step of mixing the nickel compound, the iron compound and the molybdenum compound together to prepare a mixture. The content of the mixture is described below.

(nickel compound) The type of nickel compound is not limited to a specific type. Examples of nickel compounds include nickel hydroxide, nickel oxide, nickel carbonate, nickel molybdate, nickel chloride, nickel nitrate, nickel sulfate, and nickel acetate. Nickel oxide, nickel hydroxide or nickel carbonate is preferable, and from the viewpoint of reactivity and no toxic gas generation, nickel oxide or nickel hydroxide is more preferable.

The shape of the ferrite particles after firing hardly reflects the shape of the raw material nickel compound, and therefore, as the nickel compound, spherical nickel compounds, amorphous nickel compounds, structures with a high aspect ratio (wires, fibers, ribbons, tubes, etc.), sheets, etc. can also be suitably used.

(Iron compound) The type of iron compound is not limited to a specific type and any known type can be used. Specific examples of the types include iron (II) oxide (FeO) or so-called wüstite, black iron (II, III) oxide (Fe ₃ O ₄ ), and red or brown iron (III) oxide (Fe ₂ O ₃ ). Examples of iron (III) oxide include α-Fe ₂ O ₃ , β-Fe ₂ O ₃ , γ-Fe ₂ O ₃ , and ε-Fe ₂ O ₃ . Examples of hydroxy iron oxide include α-hydroxy iron oxide, β-hydroxy iron oxide, γ-hydroxy iron oxide, and δ-hydroxy iron oxide. Examples of iron hydroxide include iron (II) hydroxide (Fe(OH) ₂ ) and iron (III) hydroxide (Fe(OH) ₃ ). As the iron oxide, iron (III) oxide (Fe ₂ O ₃ ) is preferred.

The shape of the iron compound is not limited to a specific shape, and for example, a spherical shape, a rod shape, or a plate shape can be suitably used.

(Molybdenum compound) Examples of the molybdenum compound include molybdenum oxide, molybdenum acid, molybdenum sulfide, molybdenum silicide and molybdenum oxide compounds, and preferably molybdenum oxide or molybdenum oxide compounds.

Examples of molybdenum oxides include molybdenum dioxide (MoO ₂ ) and molybdenum trioxide (MoO ₃ ), and molybdenum trioxide is preferred.

The molybdate compound is not limited as long as the molybdate compound is a molybdate anion (for example, MoO ₄ ^2- , Mo ₂ O ₇ ^2- , Mo ₃ O ₁₀ ^2- , Mo ₄ O ₁₃ ^2- , Mo ₅ O ₁₆ ^2- , Mo ₆ O ₁₉ ^2- , Mo ₇ O ₂₄ ^6- or Mo ₈ O ₂₆ ^4- ) salt compounds may be used. The molybdate compound may be an alkali metal salt, an alkaline earth metal salt, or an ammonium salt of the molybdenum oxyanion.

The molybdate compound is preferably an alkali metal salt of a molybdenum oxide anion, more preferably lithium molybdate, potassium molybdate or sodium molybdate, even more preferably potassium molybdate or sodium molybdate, and particularly preferably sodium molybdate.

In the method for producing ferrite particles of this embodiment, the molybdate compound may be a hydrate.

The molybdenum compound is preferably at least one compound selected from the group consisting of molybdenum trioxide, lithium molybdate, potassium molybdate, and sodium molybdate, and more preferably is selected from the group consisting of molybdenum trioxide, potassium molybdate, and sodium molybdate. At least one compound of the group, and even better is molybdenum trioxide and/or sodium molybdate.

(zinc compound) In the mixing step, the nickel compound, the iron compound and the molybdenum compound are mixed together, and a zinc compound may be further added to make a mixture. The types of zinc compounds are not limited to specific types. Examples of zinc compounds include zinc hydroxide, zinc oxide, zinc carbonate, zinc molybdate, zinc acetate, zinc chloride, zinc nitrate and zinc sulfate, and are preferred from the viewpoint of self-reactivity and the viewpoint of not generating toxic gases. It is zinc hydroxide or zinc oxide.

(manganese compound) In the mixing step, a manganese compound may be used instead of the nickel compound, and the manganese compound, the iron compound, and the molybdenum compound may be mixed together to form a mixture. The type of manganese compound is not limited to a specific type. Examples of manganese compounds include manganese carbonate, manganese oxide, manganese acetate, manganese chloride, manganese nitrate, manganese sulfate and hydrates thereof, and from the perspective of reactivity and the absence of toxic gas generation, manganese carbonate or manganese carbonate is preferred. Manganese oxide.

The method for producing ferrite particles in this embodiment may include the step of firing a nickel compound and an iron compound in the presence of a molybdenum compound, a sodium compound and/or a potassium compound.

The method for producing ferrite particles in this embodiment may include a step of mixing a nickel compound, an iron compound, a molybdenum compound and a sodium compound and/or a potassium compound together to prepare a mixture before the firing step (mixing step) , and may include a step of firing the mixture (firing step).

In the manufacturing method of this embodiment, by using a sodium compound and/or a potassium compound, the particle size of the ferrite particles to be manufactured can be easily adjusted and ferrite particles with low or no agglomeration can be manufactured.

A compound containing molybdenum and sodium (e.g., sodium molybdate) may be used to replace at least part of the molybdenum compound and the sodium compound. Similarly, a compound containing molybdenum and potassium (e.g., potassium molybdate) may be used to replace at least part of the molybdenum compound and the potassium compound. Therefore, the step of mixing a nickel compound, an iron compound, and a compound containing molybdenum, potassium, and/or sodium together to prepare a mixture is also regarded as the step of mixing a nickel compound, an iron compound, a molybdenum compound, a potassium compound, and/or a sodium compound together to prepare a mixture.

During the firing process, for example, molybdenum compounds and sodium compounds that are less expensive and more readily available can be used as raw materials to produce compounds containing molybdenum and sodium that are suitable as fluxes. In this example, the use of molybdenum compounds and sodium compounds as fluxes and the use of compounds containing molybdenum and sodium as fluxes are both collectively regarded as the use of molybdenum compounds and sodium compounds as fluxes, that is, there are molybdenum compounds and Sodium compounds.

During the firing process, for example, molybdenum compounds and potassium compounds that are less expensive and more readily available can be used as raw materials to produce compounds containing molybdenum and potassium that are suitable as fluxes. In this example, the use of molybdenum compounds and potassium compounds as fluxes and the use of compounds containing molybdenum and potassium as fluxes are both collectively regarded as the use of molybdenum compounds and potassium compounds as fluxes, that is, there are molybdenum compounds and Potassium compounds.

The above-mentioned molybdenum compounds may be used alone or in combination of two or more.

Sodium molybdate (Na ₂ Mo _n O _3n+1 , n = 1 to 3) contains sodium and can also function as a sodium compound as described below.

Potassium molybdate (K ₂ Mo _n O _3n+1 , n = 1 to 3) contains potassium and can also function as a potassium compound described below.

(Sodium compound) The sodium compound is not limited to a specific compound. Examples of the sodium compound include sodium carbonate, sodium molybdate, sodium oxide, sodium sulfate, sodium hydroxide, sodium nitrate, sodium chloride, and metallic sodium. Among these sodium compounds, sodium carbonate, sodium molybdate, sodium oxide, and sodium sulfate are preferably used from the viewpoint of industrial availability and ease of disposal.

The sodium compounds described above may be used alone or in combination of two or more.

In the same manner as above, sodium molybdate contains molybdenum and thus can also function as a molybdenum compound as described above.

(Potassium compound) Potassium compounds are not limited to specific compounds. Examples of potassium compounds include potassium chloride, potassium chlorite, potassium chlorate, potassium sulfate, potassium hydrogen sulfate, potassium sulfite, potassium hydrogen sulfite, potassium nitrate, potassium carbonate, potassium hydrogen carbonate, potassium acetate, potassium oxide, potassium bromide, potassium bromate, potassium hydroxide, potassium silicate, potassium phosphate, potassium hydrogen phosphate, potassium sulfide, potassium hydrogen sulfide, potassium molybdate, and potassium tungstate. In this case, the potassium compound includes isomers as in the case of the molybdenum compound. Among these potassium compounds, potassium carbonate, potassium bicarbonate, potassium oxide, potassium hydroxide, potassium chloride, potassium sulfate and potassium molybdate are preferably used, and potassium carbonate, potassium bicarbonate, potassium chloride, potassium sulfate and potassium molybdate are more preferably used.

The potassium compounds described above may be used alone or in combination of two or more.

In the same manner as above, potassium molybdate contains molybdenum and thus can also function as the molybdenum compound described above.

When the spinel structure in the ferrite particles is represented by NiFe ₂ O ₄ , in the method for making the ferrite particles of the present embodiment, examples of preferred combinations of raw materials include using nickel oxide, iron oxide (III) and molybdenum trioxide. Similarly, in the method for making ferrite particles of the present embodiment, examples of preferable combinations of raw materials include using nickel oxide, iron (III) oxide, and sodium molybdate or its hydrate. Similarly, in the method for making ferrite particles of the present embodiment, examples of preferred combinations of raw materials include using nickel oxide, iron (III) oxide, molybdenum trioxide, and sodium molybdate or its hydrate. Similarly, in the method for making ferrite particles of the present embodiment, examples of preferred combinations of raw materials include using nickel oxide, iron (III) oxide, zinc oxide, molybdenum trioxide, and sodium molybdate or their Hydrate.

In addition, when the spinel structure in the ferrite particles is represented by MnFe ₂ O ₄ , in the method for making the ferrite particles of the present embodiment, examples of preferred combinations of raw materials include using manganese carbonate or Its hydrate, iron oxyhydroxide and sodium molybdate or its hydrate.

By firing the nickel compound and the iron compound in the presence of the molybdenum compound and the sodium compound or in the presence of the molybdenum compound and the potassium compound, the particle size of the ferrite particles to be produced can be easily adjusted, and ferrite particles with low or no agglomeration can be produced. Although the reason for this is not clear, the following reasons can be conceived. For example, K ₂ MoO ₄ and Na ₂ MoO ₄ are stable compounds and are difficult to volatilize by the firing step, and therefore K ₂ MoO ₄ and Na ₂ MoO ₄ are less likely to participate in a rapid reaction during the volatilization step, making it easier to control the growth of ferrite particles. It is also believed that the molten K ₂ MoO ₄ and Na ₂ MoO ₄ exhibit functions similar to those of a solvent and that the value of the particle size can be increased, for example, by increasing the reaction time. It is also believed that the molten K ₂ MoO ₄ and Na ₂ MoO ₄ exhibit functions similar to those of a solvent and that therefore the ferrite particles are dispersed, making it difficult to agglomerate.

In the method for producing ferrite particles of the present embodiment, a molybdenum compound is used as a flux. In this specification, such a production method using a molybdenum compound as a flux may be referred to as a "flux method" hereinafter. It is believed that after the nickel compound, the iron compound, and the molybdenum compound react with each other at a high temperature to form iron molybdate and nickel molybdate by such firing, when the iron molybdate and the nickel molybdate are further decomposed into nickel-iron composite oxide and molybdenum oxide at a higher temperature, the molybdenum compound is incorporated into the ferrite particles. It is believed that the molybdenum oxide is sublimated and removed from the system, and in this process, the molybdenum compound and the nickel-iron composite oxide react with each other to form a molybdenum compound in the surface layer of the ferrite particles. More specifically, regarding the formation mechanism of the molybdenum compound contained in the ferrite particles, it is believed that the formation of Mo-O-Ni and Mo-O-Fe occurs in the surface layer of the ferrite particles by the reaction of molybdenum with nickel atoms and iron atoms, and Mo is desorbed by high-temperature sintering, and molybdenum oxides or molybdenum compounds having Mo-O-Ni-O-Fe bonds are formed in the surface layer of the ferrite particles.

Molybdenum oxide that is not incorporated into the ferrite particles can be recovered and reused by sublimating the molybdenum oxide. In this way, the amount of molybdenum oxide adhering to the surface of the ferrite particles can be reduced, and the original properties of the ferrite particles can be given to the greatest extent.

On the other hand, alkali metal salts of molybdenum oxyanions do not evaporate even within the firing temperature range and can be easily recovered by washing after firing, thereby reducing the amount of molybdenum compounds released outside the firing furnace. And significantly reduce manufacturing costs.

In the flux method, it is believed that, for example, when a molybdenum compound and a sodium compound are used in combination, the molybdenum compound and the sodium compound first react with each other to form sodium molybdate. It is believed that at the same time, the molybdenum compound and the iron compound react to form iron molybdate. It is believed that, for example, nickel molybdate and iron molybdate decompose in the presence of liquid sodium molybdate to grow crystals, and thus ferrite particles with low or no cohesion can be easily obtained, while the evaporation of the flux (sublimation of MoO ₃ ) described above is controlled.

(Other metal compounds) If desired, other metal compounds can be used during firing. The method for making ferrite particles in this embodiment may include mixing nickel compounds, iron compounds, molybdenum compounds, sodium compounds and/or potassium compounds with other metal compounds before the firing step to make a mixture. step (mixing step), and may include a step of firing the mixture (firing step).

The other metal compound is not limited to a specific metal compound, but preferably contains at least one selected from the group consisting of a Group II metal compound and a Group III metal compound.

Examples of Group II metal compounds include calcium compounds, strontium compounds, and barium compounds.

Examples of Group III metal compounds include scandium compounds, yttrium compounds, lanthanum compounds, and cerium compounds.

The other metal compounds mentioned above refer to oxides, hydroxides, carbonates and chlorides of metal elements. Examples of yttrium compounds include yttrium oxide (Y ₂ O ₃ ), yttrium hydroxide and yttrium carbonate. Among these yttrium compounds, the metal compound is preferably an oxide of a metal element. Note that these metal compounds also include isomers thereof.

Among the other metal compounds, the other metal compounds are preferably metal compounds of elements of the third period, metal compounds of elements of the fourth period, metal compounds of elements of the fifth period or metal compounds of elements of the sixth period. , more preferably a metal compound of a fourth period element or a fifth period element, and even more preferably a metal compound of a fifth period element. Specifically, it is preferable to use a calcium compound, an yttrium compound and a lanthanum compound, more preferably to use a calcium compound and an yttrium compound, and particularly preferably to use an yttrium compound.

For example, the other metal is preferably used in a proportion of 0 to 1.2 mass % (for example, 0 to 1 mol %) relative to the total amount of the metal compound used in the mixing step. compound.

In the method for producing ferrite particles of the present embodiment, the mixing amounts of the nickel compound, iron compound and molybdenum compound used are not limited to specific mixing amounts. For example, the ratio of the total mass of the nickel compound and the iron compound to the mass of the molybdenum compound in the raw material or in the mixture may be 0.1 to 40, 0.2 to 20 or 0.4 to 10.

In the method for producing ferrite particles of the present embodiment, when the zinc compound is further mixed, the mixing amounts of the nickel compound, iron compound, zinc compound and molybdenum compound used are not limited to specific mixing amounts. For example, the ratio of the total mass of the nickel compound, iron compound and zinc compound to the mass of the molybdenum compound in the raw material or in the mixture may be 0.1 to 40, 0.2 to 20 or 0.4 to 10.

In the method for producing ferrite particles in this embodiment, the mixing amounts of the manganese compound, iron compound and molybdenum compound used are not limited to specific mixing amounts. For example, the ratio of the total mass of the manganese compound and the iron compound to the mass of the molybdenum compound in the raw material or in the mixture may be 0.1 to 40, 0.2 to 20, or 0.4 to 10.

In the method for producing ferrite particles of the present embodiment, the molar ratio of nickel to iron (Ni/Fe) in the raw material or in the mixture may be, for example, 0.2 to 0.6 or 0.25 to 0.5.

[Firing steps] The firing step is the step of firing the mixture. As mentioned above, the manufacturing method of this embodiment includes firing the nickel compound and the iron compound in the presence of the molybdenum compound. Alternatively, when the mixture containing the zinc compound is obtained in the mixing step, it may include firing the nickel compound and the iron compound in the presence of the molybdenum compound and further adding the zinc compound. When the mixture containing the nickel compound, manganese compound, copper compound and/or cobalt compound is obtained in the mixing step, it may include firing the nickel compound, manganese compound, iron compound, copper compound and/or cobalt in the presence of the molybdenum compound compound. In the mixing step, manganese compounds may be used instead of nickel compounds. When the mixture containing the manganese compound and the copper compound and/or the cobalt compound is obtained, it may include firing the manganese compound, the iron compound, the copper compound and/or the cobalt compound in the presence of the molybdenum compound. The ferrite particles according to this embodiment are obtained by firing the mixture. As mentioned above, this manufacturing method is called the flux method.

The flux method is classified as a solution method. More specifically, the flux method is a method of crystal growth that exploits the fact that the crystal-flux two-component state diagram shows a eutectic state. The mechanism of the flux method is hypothesized as follows. That is, when a mixture of a solute and a flux is heated, the solute and the flux change into a liquid phase. In this process, the flux is a melting agent, or in other words, the solute-flux two-component state diagram shows a eutectic state, and therefore the solute melts at a lower temperature than the melting point of the solute to form a liquid phase. When the flux evaporates in this state, the concentration of the flux decreases, or in other words, the effect caused by the flux in lowering the melting point of the solute decreases, and the evaporation of the flux acts as a driving force for crystal growth of the solute (assisted in Flux evaporation method). Note that solutes and fluxes can also cause crystal growth of solutes by cooling the liquid phase (slow cooling method).

The flux method has advantages such as the ability to grow crystals at temperatures much lower than the melting point, the ability to precisely control the crystal structure, and the ability to form crystal bodies with euhedral shapes.

In the flux method using a molybdenum compound as a flux to produce ferrite particles, although the mechanism is not necessarily clear, it is presumed to be due to, for example, the following mechanism. That is, when a nickel compound and an iron compound are fired in the presence of a molybdenum compound, nickel molybdate and iron molybdate are first formed. In this process, nickel molybdate and iron molybdate, as can be understood from the above explanation, grow nickel ferrite crystals as their composite oxides at a temperature lower than the melting point of nickel oxide and iron oxide or nickel ferrite. Then, for example by evaporating the flux, the nickel molybdate and iron molybdate decompose and grow crystals to produce ferrite particles. That is, the molybdenum compound functions as a flux and nickel ferrite particles are produced from intermediates or nickel molybdate and iron molybdate.

The flux method can produce ferrite particles containing molybdenum, where the molybdenum is confined to the surface layer of the ferrite particles.

The firing method is not limited to a specific method and can be carried out by any known and conventional method. It is believed that when the firing temperature is higher than 800° C., the nickel compound, the iron compound, and the molybdenum compound react with each other to form nickel molybdate and iron molybdate. In addition, it is believed that when the firing temperature reaches 950° C. or higher, nickel molybdate and iron molybdate decompose to form nickel ferrite particles. It is believed that in the nickel ferrite particles, when nickel molybdate and iron molybdate decompose into nickel ferrite and molybdenum oxide, the molybdenum compound is incorporated into the nickel ferrite particles.

The states of the nickel compound, iron compound, and molybdenum compound during firing are not limited to a specific state, and the molybdenum compound only needs to exist in the same space so that the molybdenum compound can act on the nickel compound and the iron compound. Specifically, the state may be a simple mixing in which a powder of the molybdenum compound, a powder of the nickel compound, and a powder of the iron compound are mixed together, a mechanical mixing using a pulverizer or the like, or a mixing using a mortar or the like, and the mixing may be performed in a dry state or a wet state.

When the mixture containing the zinc compound is fired, the states of the nickel compound, iron compound, zinc compound and molybdenum compound are not limited to a specific state, and the molybdenum compound only needs to exist in the same space, so that the molybdenum compound can act on the nickel compound, Iron compounds and zinc compounds. Specifically, the state may be simple mixing in which powder of a molybdenum compound, a powder of a nickel compound, a powder of an iron compound, and a powder of a zinc compound are mixed together, mechanical mixing using a pulverizer or the like, or mixing using a mortar or the like. , and can be mixed in dry or wet conditions.

There is no particular limitation on the conditions of the firing temperature, and the firing temperature is appropriately determined in consideration of the particle size of the target ferrite particles, the formation of molybdenum compounds in the ferrite particles, the shape of the ferrite particles, etc. The firing temperature may be 950° C. or higher (close to the decomposition temperature of nickel molybdate and iron molybdate), 1,000° C. or higher, 1,050° C. or higher, or 1,100° C. or higher.

A higher firing temperature tends to be more likely to obtain ferrite particles having a controlled particle shape and a large particle size. From the viewpoint of efficiently producing such ferrite particles, the firing temperature is preferably 950° C. or higher, more preferably 1,000° C. or higher, even more preferably 1,050° C. or higher, and particularly preferably 1,100° C. or higher.

Generally speaking, when trying to control the shape of ferrite particles obtained after firing or improve magnetic properties, high-temperature firing at higher than 1,200°C or preferably higher than 1,500°C is required. However, there are major challenges in terms of the burden of firing furnaces and energy costs for industrial use.

For example, an embodiment of the present invention can form ferrite particles efficiently and at low cost even when the maximum firing temperature for firing the nickel compound and the iron compound is 1,500° C. or lower, thereby helping to reduce energy costs and reduce environmental load.

The method for producing ferrite particles of the present embodiment can form ferrite particles having an eumorphic shape regardless of the shape of the precursor even when the firing temperature is 1,500° C. or lower, which is lower than the melting point of iron oxide. From this point of view, the firing temperature is preferably 1,500° C. or lower, more preferably 1,400° C. or lower, even more preferably 1,300° C. or lower, and particularly preferably 1,200° C. or lower.

As an example, the firing temperature for firing the nickel compound and the iron compound in the firing step may range from 800°C to 1,500°C, 900°C to 1,500°C, 950°C to 1,400°C, 1,000°C to 1,300°C, or 1,000°C to 1,200°C.

From the perspective of manufacturing efficiency, the temperature rise rate can be 20°C/hour to 600°C/hour, 40°C/hour to 500°C/hour, or 80°C/hour to 400°C/hour.

Regarding the firing time, the temperature rise time to reach a specific firing temperature is preferably carried out in the range of 15 minutes to 10 hours. The holding time of the firing temperature may be 5 minutes or more, preferably in the range of 5 minutes to 1,000 hours, and more preferably in the range of 1 hour to 30 hours. In order to efficiently form ferrite particles, the firing temperature holding time is even more preferably 2 hours or more, and the firing temperature holding time is particularly preferably 2 hours to 24 hours.

As an example, by selecting conditions such that the firing temperature is 800°C to 1,500°C and the firing temperature holding time is 2 hours to 24 hours, ferrite particles containing molybdenum can be easily obtained.

The firing atmosphere is not limited to a specific atmosphere as long as the effect of the present invention can be achieved. For example, an oxygen-containing atmosphere (e.g., air or oxygen) or an inert atmosphere (e.g., nitrogen, argon or carbon dioxide) is preferred, and an air atmosphere is more preferred in consideration of cost.

The equipment for performing the firing is not necessarily limited, and a so-called firing furnace may be used. The firing furnace is preferably formed of a material that does not react with the sublimated molybdenum oxide, and further, it is preferred to use a highly sealed firing furnace, thereby enabling efficient use of the molybdenum oxide.

[Cooling step] The method for making ferrite particles may include a cooling step. The cooling step is a step of cooling the ferrite particles crystal-grown in the firing step.

The cooling rate is not limited to a specific rate, and is preferably 1°C/hour to 1,000°C/hour, more preferably 5°C/hour to 500°C/hour, and even more preferably 50°C/hour to 100°C/hour. The cooling rate is preferably 1°C/hour or more than 1°C/hour because the production time can be shortened. On the other hand, the cooling rate is preferably 1,000°C/hour or less since the firing container is less likely to be broken due to thermal shock and can be used for a longer period of time.

The cooling method is not limited to a specific method, and may be natural cooling or use of cooling equipment.

[Molybdenum Removal Step] The method for producing ferrite particles of this embodiment may further include a molybdenum removal step of removing at least part of the molybdenum as needed after the firing step.

Examples of the method include washing treatment and high temperature treatment. These treatments may be performed in combination.

As described above, molybdenum participates in sublimation during firing, and therefore by controlling the firing time, firing temperature, etc., the molybdenum content present in the surface layer of the ferrite particles can be controlled, and the ferrite particles can be controlled. The content and state of molybdenum present outside the surface layer (inner layer) of the bulk particles are controlled.

Molybdenum can adhere to the surface of ferrite particles. As a method other than sublimation, molybdenum can be removed by washing with water, ammonia aqueous solution, sodium hydroxide aqueous solution, or the like.

In this process, the molybdenum content in the ferrite particles can be controlled by appropriately changing the concentration and dosage of water, ammonia solution or sodium hydroxide solution, washing location, washing time, etc.

Examples of the high temperature treatment method include a method of raising the temperature to or above the sublimation point or boiling point of the molybdenum compound.

[Crushing steps] In the fired product obtained by the firing step, the ferrite particles may agglomerate and not necessarily meet the appropriate particle size range for the application under consideration. Therefore, ferrite particles can be pulverized to meet the desired suitable particle size range. Since the method of pulverizing the fired product is not limited to a specific method, and conventionally known pulverizing methods such as ball mill, jaw crusher, jet mill, disk mill, spectrum mill ( Spectromill, grinder and mixer mill.

[Classification step] The fired product containing ferrite particles obtained by the firing step may be subjected to appropriate classification treatment to adjust the particle size range. "Classification treatment" refers to the operation of grouping particles according to their sizes.

Sorting can be done in a wet or dry form, but dry sorting is preferred from the perspective of yield. Dry sorting includes sorting using a screen and wind sorting, where the sorting is performed by the difference between centrifugal force and fluid resistance. From the perspective of sorting accuracy, wind sorting is preferred, which can be performed using a sorter (e.g., an airflow sorter using the Coanda effect, a vortex airflow sorter, a vortex centrifugal sorter, and a semi-free vortex centrifugal sorter).

The pulverization step and the classification step may be performed at a necessary stage. For example, the average particle size of the ferrite particles to be obtained may be adjusted by the presence or absence of pulverization and classification and by selecting the conditions of pulverization and classification.

The ferrite particles of the present embodiment or the ferrite particles obtained by the manufacturing method of the present embodiment have little or no agglomeration, and are therefore better from the following perspectives: the ferrite particles of the present embodiment or the ferrite particles obtained by the manufacturing method of the present embodiment are easy to show their original properties, are excellent in their own disposability, and have better dispersibility when the ferrite particles of the present embodiment or the ferrite particles obtained by the manufacturing method of the present embodiment are dispersed in a dispersed medium for use.

The method for producing ferrite particles of the present embodiment can easily produce ferrite particles with little or no agglomeration, and therefore has an excellent advantage that ferrite particles having desired excellent properties can be produced at a high yield even without performing a pulverization step or a classification step.

The method for producing ferrite particles of the above-described embodiment can produce ferrite particles containing molybdenum and having high quality because of its easy control of shape and high efficiency. [Example]

The present invention is described in more detail below with reference to examples. The present invention is not limited to the following examples.

<Production of ferrite particles> [Example 1] Into an 80 ml zirconia pot were charged 5.63 g of nickel oxide (manufactured by Kanto Chemical Co., Inc.), 12.45 g of iron (III) oxide (manufactured by Kanto Chemical Co., Inc.), 3.6 g of molybdenum trioxide (manufactured by Nippon Inorganic Colour & Chemical Co., Ltd.) and 100 g of 5 mm diameter (mmφ) zirconia beads, which were mixed together and pulverized using a planetary ball mill (P-5 manufactured by Fritsch) at 200 revolutions per minute (rpm) for 60 minutes to obtain a mixture. The obtained mixture was placed in a crucible and fired in a ceramic electric furnace at 1,100°C for 10 hours. The temperature was raised at 5°C/min. After the temperature dropped, the crucible was taken out to obtain a black powder. The obtained black powder was transferred to a beaker, 200 g of 0.5% ammonia water was added thereto, stirred and washed for 3 hours to dissolve the remaining molybdenum trioxide. The obtained particles filtered by suction filtration using 5C filter paper were then dried at 120°C to obtain 17.1 g of white powder. The obtained particles were NiFe ₂ O ₄ .

[Example 2] A black powder was obtained in the same manner as in Example 1 except that the amount of molybdenum trioxide charged was 1.8 g.

[Example 3] Into a 100 ml polypropylene bottle, 3.19 g of nickel oxide (manufactured by Kanto Chemical Co., Ltd.), 6.81 g of iron (III) oxide (manufactured by Kanto Chemical Co., Ltd.), 13.94 g of sodium molybdate dihydrate (manufactured by Kanto Chemical Co., Ltd.), 8.23 g of molybdenum trioxide (manufactured by Japan Inorganic Pigments & Chemicals Co., Ltd.) and 100 g of 5 mm diameter zirconia beads were charged, mixed together and pulverized for 120 minutes using a paint mixer (manufactured by Toyo Seiki Seisaku-sho, Ltd.) to obtain a mixture. The obtained mixture was put into a crucible and fired at 1,300°C for 10 hours in a ceramic electric furnace. The temperature was increased at 5°C/min. After the temperature was lowered, the crucible was taken out to obtain a black powder. The obtained black powder was transferred to a beaker, 200 g of ion exchange water was added thereto, stirred and washed for 3 hours to dissolve the remaining sodium molybdate. Then, the obtained particles filtered by suction filtration using 5C filter paper were dried at 120°C to obtain 9.2 g of black powder. The obtained particles were NiFe ₂ O ₄ .

[Example 4] A black powder was obtained in the same manner as in Example 3 except that the firing temperature was 1,500°C and the temperature rise rate was 2°C/min.

[Example 5] A black powder was obtained in the same manner as in Example 3 except that the firing temperature was 900°C and the temperature rise rate was 2°C/min.

[Example 6] Black powder was obtained in the same manner as in Example 3 except that the firing temperature was 1,100°C.

[Example 7] The charging amount of nickel oxide was 3.02 g, and 0.17 g of zinc oxide (ZnO vs. (NiO + ZnO)) was further added to the nickel oxide, iron (III) oxide, sodium molybdate dihydrate and molybdenum trioxide. A black powder was obtained in the same manner as in Example 6 except that the molar ratio: 0.05). The obtained particles are particles mainly containing NiZnFe ₂ O ₄ .

[Example 8] A black powder was obtained in the same manner as in Example 7 except that the charge amount of nickel oxide was 2.86 g and the charge amount of zinc oxide was 0.35 g (molar ratio of ZnO to (NiO + ZnO): 0.1).

[Example 9] Black powder was obtained in the same manner as in Example 7 except that the charging amount of nickel oxide was 2.23 g and the charging amount of zinc oxide was 1.04 g (molar ratio of ZnO to (NiO + ZnO): 0.3).

[Example 10] A black powder was obtained in the same manner as in Example 7 except that the charge amount of nickel oxide was 1.59 g and the charge amount of zinc oxide was 1.73 g (molar ratio of ZnO to (NiO + ZnO): 0.5).

[Example 11] A 100 ml polypropylene bottle was charged with 6.65 g of manganese carbonate-n-hydrate (manufactured by Kanto Chemical Co., Ltd.), 8.89 g of iron oxyhydroxide (manufactured by Kanto Chemical Co., Ltd.), 15.5 g of sodium molybdate dihydrate (manufactured by Kanto Chemical Co., Ltd.), 100 g of 5 mm diameter zirconia beads and 20 g of ion-exchanged water were mixed together and pulverized in wet form using a paint stirrer 120 minutes to obtain the mixture. The obtained mixture was dried at 120 degrees Celsius, put into a crucible, and fired at 800°C for 10 hours in a nitrogen atmosphere using an atmospheric electric furnace. The temperature rise was performed at 5°C/min. After the temperature was lowered the crucible was taken out to obtain a black powder. The obtained black powder was transferred to a beaker, 200 grams of ion-exchange water was added thereto, stirred and washed for 3 hours to dissolve the remaining sodium molybdate. The obtained particles filtered out by suction filtration using 5C filter paper were then dried at 120° C. to obtain black powder. The obtained particles are particles mainly containing MnFe ₂ O ₄ .

[Comparative Example 1] An 80 ml zirconia pot was charged with 5.63 g of nickel oxide (manufactured by Kanto Chemical Co., Ltd.), 12.45 g of iron (III) oxide (manufactured by Kanto Chemical Co., Ltd.) and 100 g 5 mm diameter zirconia beads were mixed together and crushed using a planetary ball mill (P-5 manufactured by Feichi Corporation) at 200 rpm for 60 minutes to obtain a mixture. The obtained mixture was put into a crucible and fired in a ceramic electric furnace at 1,100°C for 10 hours. The temperature rise was performed at 5°C/min. After the temperature was lowered, the crucible was taken out to obtain 17.5 grams of black powder. The particles obtained were NiFe ₂ O ₄ containing a small amount of unreacted material.

＜Evaluation＞ The powders obtained in Examples 1 to 11 and Comparative Example 1 were used as sample powders to conduct the following evaluations.

[Crystal structure analysis: X-ray Diffraction (XRD)] The sample powder was filled into a 0.5 mm deep sample holder in a wide-angle X-ray diffraction (XRD) equipment (Ultima IV manufactured by Rigaku Corporation) for measurement, and the measurement was carried out under the conditions of Cu/Kα radiation, 40 kV/40 mA, a scanning speed of 2°/min, and a scanning range of 10° to 70°.

[Measurement of specific surface area of ferrite particles] The specific surface area of ferrite particles was measured using a specific surface area meter (Baythorpe Mini manufactured by Macchik Bayer), and the surface area per gram of sample measured from the adsorption amount of nitrogen by the BET method was calculated as the specific surface area (m2/g).

[Primary particle size] Ferrite particles were photographed using a scanning electron microscope (SEM). For the smallest unit of particles (i.e., primary particles) on a two-dimensional image, the average value of the maximum length measured between two points on the contour of 50 randomly selected primary particles was defined as the primary particle size of the ferrite particles.

[Particle size distribution measurement] The particle size distribution of the sample powder was measured in a dry form using a laser diffraction dry particle size analyzer (HELOS (H3355) & RODOS manufactured by Nippon Laser Co., Ltd.) under a dispersion pressure of 3 bar and a tensile pressure of 90 mbar. The particle size at the point where the distribution curve of the volume cumulative percentage intersects the horizontal axis at 50% was determined as _D50 .

[X-ray fluorescence (XRF) analysis] Using an X-ray fluorescence analyzer (Primus IV manufactured by Rigaku Corporation, Japan), approximately 70 mg of sample powder was placed on filter paper, covered with a polypropylene (PP) film and subjected to X-ray fluorescence (XRF) analysis under the following conditions. Measurement conditions EZ scan mode Measured elements: F to U Measuring time: Standard Measuring diameter: 10 mm Residues (other components): None

The nickel content, iron content, zinc content, and molybdenum content of the ferrite particles obtained by XRF analysis were determined in terms of oxides to obtain the NiO content (Ni ₁ ) relative to 100 mass % of the ferrite particles. Fe ₂ O ₃ content (Fe ₁ ) relative to 100 mass % of ferrite particles, ZnO ₂ content (Zn ₁ ) relative to 100 mass % ferrite particles, and Results for MoO ₃ content (Mo ₁ ).

The manganese content, iron content, and molybdenum content of the ferrite particles obtained by XRF analysis were determined in terms of oxides to obtain the MnO ₂ content (Mn ₁ ) relative to 100 mass % of the ferrite particles, relative to 100 Fe ₂ O ₃ content (Fe ₁ ) of mass % of ferrite particles and MoO ₃ content (Mo ₁ ) relative to 100 mass % of ferrite particles.

[XPS Surface Analysis] For surface element analysis of the sample powder, X-ray photoelectron spectroscopy (XPS) was performed using monochromatic Al-Kα as an X-ray source and an X-ray photoelectron spectrometer (Quatara SXM manufactured by AIFAC) ) measurement. Obtain the average of n = 3 measurements for each element in atomic % from 1,000 square micron area measurements.

The nickel content in the surface layer of the ferrite particles, the iron content in the surface layer, and the molybdenum content in the surface layer obtained by XPS analysis were determined in terms of oxides to determine the NiO content (Ni ₂ ) (mass %) of the surface layer of the ferrite particles relative to 100 mass %, the Fe ₂ O ₃ content (Fe ₂ ) (mass %) of the surface layer of the ferrite particles relative to 100 mass %, and the MoO ₃ content (Mo ₂ ) (mass %) of the surface layer of the ferrite particles relative to 100 mass %.

The manganese content in the surface layer of the ferrite particles obtained by XPS analysis, the iron content in the surface layer, and the molybdenum content in the surface layer were determined in terms of oxides to determine the content relative to 100 mass % of the ferrite particles. MnO ₂ content (Mn ₂ ) (mass %) of the surface layer, Fe ₂ O ₃ content (Fe ₂ ) (mass %) of the surface layer relative to 100 mass % of ferrite particles, and relative to 100 mass % MoO ₃ content (Mo ₂ ) in the surface layer of ferrite particles (mass %).

[Magnetic analysis] A sample with an area of 30 square millimeters, a thickness of 2.5 millimeters, and a mass of approximately 0.15 grams was measured using a vibrating sample magnetometer (BHV-50 manufactured by Riken Denshi Co., Ltd.) at a magnetic field strength of 7.96 × 10 ⁴ amperes per meter (A/m) and a measurement period of 5 minutes.

＜Result＞ Table 1 lists the corresponding values obtained by the evaluation. It should be noted that "N.D." is the abbreviation of "Not Detected" and indicates that there is no detection.

[Table 1] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Example 11 Comparison Example 1 Manufacturing conditions NiO gram 5.63 5.63 3.19 3.19 3.19 3.19 3.02 2.86 2.23 1.59 - 5.63 _{Fe2O3 ​} gram 12.45 12.45 6.81 6.81 6.81 6.81 6.81 6.81 6.81 6.81 - 12.45 ZnO gram - - - - - - 0.17 0.35 1.04 1.73 - - MnCO ₃ ·nH ₂ O gram - - - - - - - - - - 6.65 - FeOOH gram - - - - - - - - - - 8.89 - Na ₂ MoO ₄ ·2H ₂ O gram - - 13.94 13.94 13.94 13.94 13.94 13.94 13.94 13.94 15.5 - MoO ₃ gram 3.6 1.8 8.23 8.23 8.23 8.23 8.23 8.23 8.23 8.23 - - (Ni compound + Fe compound + Zn compound)/Mo compound Mass ratio 10/2 10/1 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 - (Mn compound + Fe compound)/Mo compound Mass ratio 1/1 Ni/Fe Molar ratio 1/2 1/2 1/2 1/2 1/2 1/2 1/2.1 1/2.2 1/2.9 1/4 1/2 Mn/Fe Molar ratio 1/2 Zn/Fe Molar ratio 1/40 1/20 1/7 1/4 Firing temperature °C 1100 1100 1300 1500 900 1100 1100 1100 1100 1100 800 1100 Firing time Hours 10 10 10 10 10 10 10 10 10 10 10 10 evaluate Impurity Detection - - - - - - - - - - + + Degree of cohesion - - - - - - - - - - - + Specific surface area Square meter/gram 0.45 0.55 0.60 0.31 1.24 0.98 0.82 0.78 0.80 0.91 1.67 2.52 Primary particle size Micrometer 12 8 7 17 2 5 5 5 5 5 1 4 D ₅₀ Micrometer 18.3 17.9 10.9 34.1 7.4 9.2 8.5 8.0 7.1 6.3 1.7 1.8 XRF MoO ₃ (Mo ₁ ) Quality% 8.6 7.1 10.9 12.7 19.8 1.4 1.8 1.6 0.8 2.1 0.0 Not detected NiO (Ni ₁ ) Quality% 28.5 29.7 25.5 21.5 23.6 31.3 28.6 27.7 21.8 16.2 31.6 Fe ₂ O ₃ (Fe ₁ ) Quality% 61.9 62.5 48.4 49.2 45.5 56.5 52.6 52.5 52.1 51.8 66 68.1 ZnO ₂ (Zn ₁ ) Quality% 1.3 2.5 8.2 13.6 MnO ₂ (Mn ₁ ) Quality% 33.5 XPS MoO ₃ (Mo ₂ ) Quality% 16.1 8.5 81.7 87 80.1 38 45.4 42.9 30.6 61.5 3.23 Not detected NiO ( _Ni2 ) Quality% 38.2 53.2 0 0 0 7.4 6.7 7.2 8.3 1.5 0 30.6 Fe ₂ O ₃ (Fe ₂ ) Quality% 45.6 38.3 18.3 13 19.9 54.6 47.2 47.7 55.6 32.1 40 ZnO ₂ (Zn ₂ ) Quality% 0.7 2.2 5.4 4.9 MnO ₂ (Mn ₂ ) Quality% 56.7 MoO ₃ surface layer uneven distribution ratio (Mo ₂ /Mo ₁ ) Mass ratio 1.9 1.2 7.5 6.9 4.0 27.1 25.2 26.8 38.3 29.3 - - Stubbornness A/m - 7.2E+02 - - - - - - - 1.2E+03 1.4E+03 2.5E+03

FIG. 1 to FIG. 12 show SEM images of the powders of the examples and the comparative examples obtained by photographing using a scanning electron microscope (SEM). In the powders of the corresponding examples of Examples 1 to 10, many beautiful polygonal particles were identified and the crystal shape of the particles was controlled during the manufacturing process (FIG. 1 to FIG. 10). In the powder of Example 11, many beautiful polygonal particles were also identified and the crystal shape of the particles was controlled during the manufacturing process (FIG. 11). In contrast, in the powder of Comparative Example 1, amorphous particles in which no specific shape was observed were observed (FIG. 12).

FIG13 shows the results of XRD analysis of Examples 1 to 10 and Comparative Example 1. In the samples of Examples and Comparative Examples, peaks derived from ferrite (Ni ₂ Fe ₂ O ₄ ) were identified (peaks not labeled). FIG14 shows the results of XRD analysis of Example 11. In the sample of this Example, peaks derived from ferrite (Mn ₂ Fe ₂ O ₄ ) were identified (peaks not labeled).

According to the results of SEM observation and XRD analysis, it was confirmed that the powders obtained in the examples and comparative examples were ferrite particles containing ferrite.

In the sample powders of Examples 1 to 11, the peaks derived from impurities were almost not identified (Figures 13 and 14, the detection of impurities in Table 1 is "-"). On the contrary, in the sample powder of Comparative Example 1, the peaks derived from impurities (e.g., nickel oxide and iron oxide, i.e., unreacted raw materials) were clearly detected (peaks with circle "●" in Figure 13) (the detection of impurities in Table 1 is "+"). Based on this result, it is inferred that in the sample powder of Comparative Example 1, the ferrite formation reaction is incomplete and unreacted substances remain.

According to this result, in the example in which the nickel compound and the iron compound are fired in the presence of the molybdenum compound, the ferrite formation reaction proceeds smoothly even at a relatively low firing temperature of 900° C. to 1,500° C. and high-quality ferrite particles with reduced impurity content and controlled shape can be efficiently produced.

The degree of particle agglomeration was evaluated from the SEM images of the corresponding ferrite particles based on the following criteria. ++: Particle agglomeration was identified. +: Some particle agglomeration was identified. -: No obvious particle agglomeration was identified.

In the ferrite particles of Comparative Example 1, obvious agglomeration fusion was recognized between the particles (agglomeration degree: +), while no obvious agglomeration was recognized in the ferrite particles of Examples 1 to 11 (agglomeration degree: -). This result indicates that in the example in which the nickel compound or the manganese compound and the iron compound are fired in the presence of the molybdenum compound, ferrite particles with low or no agglomeration can be easily produced.

In the examples (for example, see Examples 3, 5, and 6), a higher firing temperature tends to give ferrite particles with a larger particle size. Therefore, it was found that by controlling the firing temperature, the particle size of the ferrite particles can be controlled and ferrite particles with a desired particle size can be produced.

Table 1 lists the values of NiO content (Ni ₁ ), Fe ₂ O ₃ content (Fe ₁ ), ZnO ₂ content (Zn ₁ ), MoO ₃ content (Mo ₁ ), NiO content (Ni ₂ ), Fe ₂ O ₃ content (Fe ₂ ), ZnO ₂ content (Zn ₂ ) and MoO ₃ content (Mo ₂ ). Table 1 also lists the values of MnO ₂ content (Mn ₁ ), Fe ₂ O ₃ content (Fe ₁ ), MoO ₃ content (Mo ₁ ), MnO ₂ content (Mn ₂ ), Fe ₂ O ₃ content (Fe ₂ ) and MoO ₃ content (Mo ₂ ).

Based on the results of the MoO ₃ content (Mo ₁ ), it was confirmed that molybdenum-containing ferrite particles were obtained.

According to the results of the MoO ₃ content (Mo ₂ ), the ferrite particles of Examples 1 to 11 contain molybdenum in the surface layer of the ferrite particles and can be expected to exhibit various effects of molybdenum, such as magnetic properties.

Table 1 lists the calculation results of the surface layer localization ratio (Mo ₂ /Mo ₁ ) of the MoO ₃ content (Mo ₂ ) relative to the MoO ₃ content (Mo ₁ ).

According to the results of the surface layer localization ratio (Mo ₂ /Mo ₁ ), in the ferrite particles of Examples 1 to 11, the molybdenum content of the surface layer of the ferrite particles determined by XPS surface analysis was greater than the molybdenum content determined by XRF analysis. From this result, it was confirmed that molybdenum was localized in the surface layer of the ferrite particles and that molybdenum could be expected to efficiently exhibit various effects.

In the ferrite particles obtained in Examples 1 and 2 in which _MoO3 was used in the raw material, the molybdenum content determined by XRF analysis varied with the ratio of (Ni compound + Fe compound)/Mo compound in the raw material. increases and tends to decrease. In Examples 3 to 6 in which Na ₂ MoO ₄ was used in combination in the raw materials, when the ratio of (Ni compound + Fe compound)/(Mo compound) in the raw materials was constant at 1/2, it was determined by XRF analysis The molybdenum content and the molybdenum content in the surface layer of the ferrite particles, determined by XPS surface analysis, change with changes in firing temperature.

Therefore, by controlling the amount and type of the molybdenum compound used or the firing temperature, the amount of molybdenum contained in the ferrite particles can be controlled and ferrite particles containing a desired amount of molybdenum can be produced.

In Examples 7 to 10 in which Na ₂ MoO ₄ was used in combination with ZnO in the raw materials, when the ratio of (Ni compound + Fe compound + Zn compound)/(Mo compound) in the raw materials was constant at 1/2 , the molybdenum content determined by XRF analysis and the molybdenum content in the surface layer of the ferrite particles determined by XPS surface analysis change with the change of Ni/Fe.

Table 1 lists the coercivity values measured in Example 2, Example 10, and Example 11 as representatives. The ferrite particles of Example 2, Example 10, and Example 11 had a coercivity of 1.4 × 10 ³ A/m or ^less , which was as low as about 1/2 to 1/4 of the coercivity of Comparative Example 1 in which MoO ₃ was not used in the raw materials, and revealed that suitable ferrite particles as soft ferrite (soft magnetic material) were obtained. On the contrary, the toughness of the ferrite particles of Comparative Example 1 is a value higher than the toughness values in Examples 2, 10 and 11, namely 2.5 × 10 ³ A/m, and it is revealed that the ferrite particles of Comparative Example 1 are not suitable as soft ferrite.

Each configuration and combination in each embodiment is exemplary, and additions, omissions, substitutions and other changes may be made to the configuration without departing from the gist of the invention. The present invention is not limited to each embodiment, but is only limited to the scope of the patent application.

without

Figure 1 is a scanning electron microscope (SEM) image of the ferrite particles obtained in Example 1. Figure 2 is an SEM image of the ferrite particles obtained in Example 2. Figure 3 is an SEM image of the ferrite particles obtained in Example 3. Figure 4 is an SEM image of the ferrite particles obtained in Example 4. Figure 5 is an SEM image of the ferrite particles obtained in Example 5. Figure 6 is an SEM image of the ferrite particles obtained in Example 6. Figure 7 is an SEM image of the ferrite particles obtained in Example 7. Figure 8 is an SEM image of the ferrite particles obtained in Example 8. Figure 9 is an SEM image of the ferrite particles obtained in Example 9. FIG. 10 is an SEM image of the ferrite particles obtained in Example 10. Figure 11 is an SEM image of the ferrite particles obtained in Example 11. FIG. 12 is an SEM image of the ferrite particles obtained in Comparative Example 1. 13 is an X-ray diffraction (XRD) pattern of the ferrite particles obtained in Examples 1 to 10 and Comparative Example 1. Figure 14 is an X-ray diffraction (XRD) pattern of the ferrite particles obtained in Example 11.

Claims (13)

A ferrite particle containing molybdenum. The ferrite particles according to claim 1, wherein the ferrite particles have a spinel structure. The ferrite particles as described in claim 2, wherein the spinel structure is represented by the _{formula AFe2O4} , wherein A is one or more elements selected from Ni, Mn, Cu, Zn, Mg, Ca and Co. The ferrite particles according to claim 1 or 2, wherein the molybdenum content in the ferrite particles is 0.1 mass% to 30 mass%, and the molybdenum content in the ferrite particles is determined by The content (Mo ₁ ) of the ferrite particles in terms of MoO ₃ relative to 100 mass % of the ferrite particles is determined by X-ray fluorescence (XRF) analysis. The ferrite particles according to claim 1 or 2, wherein the molybdenum content in the surface layer of the ferrite particles is 2.0 mass % to 95.0 mass %, wherein the molybdenum content in the surface layer of the ferrite particles is the content (Mo ₂ ) in terms of MoO ₃ relative to 100 mass % of the surface layer of the ferrite particles determined by performing X-ray photoelectron spectroscopy (XPS) surface analysis on the ferrite particles. The ferrite particle as described in claim 1 or 2, wherein the molybdenum is confined in the surface layer of the ferrite particle. The ferrite particles according to claim 1 or 2, wherein a molybdenum surface layer localization ratio (Mo ₂ /Mo ₁ ) is 1.0 to 80, wherein the molybdenum surface layer localization ratio is a ratio of a content (Mo _{2 )} in terms of MoO 3 in the surface layer of the ferrite particles relative to 100% by mass determined by performing X-ray photoelectron spectroscopy (XPS) surface analysis on the ferrite particles to a content (Mo ₁ ) in terms of MoO ₃ in the ferrite particles relative to ₁₀₀ % by mass determined by performing X-ray fluorescence analysis on the ferrite particles. The ferrite particles as described in claim 1 or 2, wherein the average particle size of the primary particles of the ferrite particles is 0.1 microns to 100 microns. The ferrite particles as claimed in claim 1 or 2, wherein the ferrite particles have a specific surface area measured by the BET method of 0.1 m2/g to 2.5 m2/g. A method for producing ferrite particles, which is a method for producing ferrite particles as described in claim 1, the method comprising: firing a metal compound and an iron compound in the presence of a molybdenum compound. The method for producing ferrite particles as described in claim 10 comprises: sintering the metal compound and the iron compound and further adding a zinc compound in the presence of the molybdenum compound. A method for producing ferrite particles as described in claim 10 or 11, wherein the molybdenum compound is at least one compound selected from the group consisting of molybdenum trioxide, lithium molybdate, potassium molybdate and sodium molybdate. The method for producing ferrite particles according to claim 10 or 11, wherein the firing temperature during firing is 800°C to 1,500°C.