Magnetoplumbite-type hexagonal ferrite powder, radio wave absorber, and method of controlling resonance frequency of magnetoplumbite-type hexagonal ferrite powder

Patent metadata

Field	Value
Publication number	US-12125622-B2
Application number	US-202117469166-A
Country	US
Kind code	B2
Filing date	Sep 8, 2021
Priority date	Mar 19, 2019
Publication date	Oct 22, 2024
Grant date	Oct 22, 2024

Abstract

A magnetoplumbite-type hexagonal ferrite powder containing a powder of a magnetoplumbite-type hexagonal ferrite represented by Formula (1) and a powder of a compound represented by Formula (2), in which a magnetic field strength Hα, which corresponds to 90% of a magnetization quantity obtained in a case where an external magnetic field of 50 kOe is applied, satisfies 19 kOe≤Hα≤28 kOe, a radio wave absorber, and a method of controlling resonance frequency of a magnetoplumbite-type hexagonal ferrite powder are provided. 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. In Formula (2), Aa represents at least one metal element selected from the group consisting of Sr, Ba, Ca, and Pb.AFe(12-x)AlxO19  Formula (1)AaAl2O4  Formula (2)

First claim

What is claimed is:

1. A magnetoplumbite-type hexagonal ferrite powder, comprising:
a powder of a compound represented by Formula (1); and
a powder of a compound represented by Formula (2),
wherein a magnetic field strength Ha, which corresponds to 90% of a magnetization quantity obtained in a case where an external magnetic field of 50 kOe is applied, satisfies 19 kOe≤Hα≤28 kOe:
AFe (12-x) Al x O 19   Formula (1)

wherein 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; and
A a Al 2 O 4   Formula (2)

wherein in Formula (2), A a represents at least one metal element selected from the group consisting of Sr, Ba, Ca, and Pb,
wherein a ratio x′ of aluminum atoms with respect to 100 atom % of iron atoms in the magnetoplumbite-type hexagonal ferrite powder is from 1.80 to 2.65.

2. The magnetoplumbite-type hexagonal ferrite powder according to claim 1 ,
wherein A in Formula (1) comprises Sr.

3. The magnetoplumbite-type hexagonal ferrite powder according to claim 1 ,
wherein the magnetoplumbite-type hexagonal ferrite powder has been subjected to a surface treatment.

4. The magnetoplumbite-type hexagonal ferrite powder according to claim 1 ,
wherein the surface treatment comprises at least one selected from the group consisting of an oil treatment, a silicone treatment, a fluorine compound treatment, a silane coupling agent treatment, a titanium coupling agent treatment, a metal soap treatment, an amino acid treatment, a lecithin treatment, a polyethylene treatment, a mechanochemical treatment, and a phosphoric acid compound treatment.

5. A radio wave absorber, comprising:
the magnetoplumbite-type hexagonal ferrite powder according to claim 1 ; and
a binder,
wherein the radio wave absorber has a planar shape.

6. A radio wave absorber, comprising:
the magnetoplumbite-type hexagonal ferrite powder according to claim 1 ; and
a binder,
wherein the radio wave absorber has a three-dimensional shape.

7. A method of controlling a resonance frequency of a magnetoplumbite-type hexagonal ferrite powder, the method comprising:
adjusting a magnetic field strength Ha which corresponds to 90% of a magnetization quantity obtained in a case where an external magnetic field of 50 kOe is applied to a magnetoplumbite-type hexagonal ferrite powder within a range satisfying 19 kOe≤Hα≤28 kOe, the magnetoplumbite-type hexagonal ferrite powder comprising a powder of a compound represented by Formula (1):
AFe (12-x) Al x O 19   Formula (1)

wherein 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
wherein the magnetoplumbite-type hexagonal ferrite powder comprises a compound represented by Formula (2):
A a Al 2 O 4   Formula (2)

wherein in Formula (2), A a represents at least one metal element selected from the group consisting of Sr, Ba, Ca, and Pb, and
wherein a ratio x′ of aluminum atoms with respect to 100 atom % of iron atoms in the magnetoplumbite-type hexagonal ferrite powder is from 1.80 to 2.65.

Assignees

• Fujifilm Corp

Inventors

• Hashimoto Hirokazu

Classifications

• H05K9/0075

  Magnetic shielding materials · CPC title

• C01P2006/42

  Magnetic properties · CPC title

• C01P2002/76

  by a space-group or by other symmetry indications · CPC title

• C01G49/06

  Ferric oxide [Fe2O3] · 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