Powder of magnetoplumbite-type hexagonal ferrite, method for producing the same, and radio wave absorber

Patent metadata

Field	Value
Publication number	US-12260977-B2
Application number	US-202117173437-A
Country	US
Kind code	B2
Filing date	Feb 11, 2021
Priority date	Aug 28, 2018
Publication date	Mar 25, 2025
Grant date	Mar 25, 2025

Abstract

The powder of the magnetoplumbite-type hexagonal ferrite is an aggregate of particles of a compound represented by Formula (1), and, in a particle size distribution based on number measured by a laser diffraction scattering method, in a case where a mode value is defined as a mode diameter, a diameter at a cumulative percentage of 10% is defined as D10 and a diameter at a cumulative percentage of 90% is defined as D90, the mode diameter is equal to or greater than 5 μm and less than 10 μm and an expression of (D90−D10)/mode diameter≤3.0 is satisfied. In Formula (1), A represents at least one metal element selected from the group consisting of Sr, Ba, Ca, and Pb, and x satisfies 1.5≤x≤8.0.

AFe (12-x) Al x O 19   Formula(1)

First claim

What is claimed is:

1. A powder of a magnetoplumbite-type hexagonal ferrite which is an aggregate of particles of a compound represented by Formula (1), and
wherein, in a particle size distribution based on number measured by a laser diffraction scattering method, in a case where a mode value is defined as a mode diameter, a diameter at a cumulative percentage of 10% is defined as D 10 and a diameter at a cumulative percentage of 90% is defined as D 90 , the mode diameter is equal to or greater than 5 μm and less than 10 μm and an expression of (D 90 −D 10 )/mode diameter≤3.0 is satisfied,
AFe (12-x) Al x O 19   Formula (1)

in Formula (1), A represents at least one metal element selected from the group consisting of Sr, Ba, Ca, and Pb, and x satisfies 1.5≤x≤8.0.

2. The powder of a magnetoplumbite-type hexagonal ferrite according to claim 1 ,
wherein x in Formula (1) satisfies 1.5≤x≤6.0.

3. The powder of a magnetoplumbite-type hexagonal ferrite according to claim 1 ,
wherein a crystal phase is a single phase.

4. The powder of a magnetoplumbite-type hexagonal ferrite according to claim 1 ,
wherein the powder of the magnetoplumbite-type hexagonal ferrite is used for a radio wave absorber.

5. A method for producing the powder of a magnetoplumbite-type hexagonal ferrite according to claim 1 , the method comprising:
a step A of obtaining a reaction product containing Fe, Al, and the at least one metal element selected from the group consisting of Sr, Ba, Ca, and Pb by a liquid phase method; and
a step B of drying the reaction product obtained in the step A, thereby obtaining a dried product; and
a step C of any one of a step of obtaining a fired product by firing the dried product obtained in the step B and pulverizing the obtained fired product or a step of obtaining a pulverized product by pulverizing the dried product obtained in the step B and firing the obtained pulverized product.

6. The method for producing the powder of a magnetoplumbite-type hexagonal ferrite according to claim 5 ,
wherein the step A includes a step of mixing an aqueous solution containing an Fe salt, an Al salt, and a salt of the at least one metal element with an alkali aqueous solution, thereby obtaining a reaction product.

7. A radio wave absorber comprising:
the powder of a magnetoplumbite-type hexagonal ferrite according to claim 1 ; and
a binder.

8. The powder of a magnetoplumbite-type hexagonal ferrite according to claim 1 ,
wherein A in Formula (1) is at least one metal element selected from the group consisting of Sr, Ba, and Ca.

9. The powder of a magnetoplumbite-type hexagonal ferrite according to claim 1 ,
wherein A in Formula (1) includes Sr.

10. The powder of a magnetoplumbite-type hexagonal ferrite according to claim 1 ,
wherein the mode diameter is 5 μm to 9 μm.

Assignees

• Fujifilm Corp

Inventors

• Hashimoto Hirokazu

Classifications

• H01Q17/00

  Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems · CPC title

• C01P2004/02

  obtained by optical microscopy · CPC title

• C01P2002/72

  by d-values or two theta-values, e.g. as X-ray diagram · CPC title

• C01G49/0072

  containing manganese · CPC title

• H05K9/00

  Screening of apparatus or components against electric or magnetic fields (devices for absorbing radiation from an antenna H01Q17/00) · CPC title