# US 11,440,848 B2 · Ferrite sintered magnet

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- Number: US 11,440,848 B2
- Document ID: US11440848B2
- Status: Granted
- Kind: B2
- Application number: 16/782,343
- Filed: 2020-02-05
- Published: 2020-08-13
- Granted: 2022-09-13
- Earliest claimed: 2019-02-07
- Assignees: TDK Corporation
- Applicants: TDK Corporation
- Inventors: Masanori Ikeda; Hiroyuki Morita; Yoshitaka Murakawa; Shogo Muroya
- Web page: https://patentgrep.com/patent/US11440848B2

## CPC

- C04B 35/2633: {containing barium, strontium or calcium}
- C01G 51/68: containing rare earths, e.g. (La0.3Sr0.7)CoO3
- C01G 51/70: containing rare earths, e.g. LaCoO3 (C01G51/68 takes precedence)
- C04B 35/2608: {Compositions containing one or more ferrites of the group comprising manganese, zinc, nickel, copper or cobalt and one or more ferrites of the group comprising rare earth metals, alkali metals, alkaline earth metals or lead}
- C04B 35/2641: {Compositions containing one or more ferrites of the group comprising rare earth metals and one or more ferrites of the group comprising alkali metals, alkaline earth metals or lead}
- C04B 35/6261: {Milling}
- C04B 35/6263: {characterised by their solids loadings, i.e. the percentage of solids}
- H01F 1/10: non-metallic substances, e.g. ferrites {, e.g. [(Ba,Sr)O(Fe2O3)6] ferrites with hexagonal structure}
- H01F 1/11: in the form of particles {(for magnetic record carriers G11B5/70626)}
- H01F 41/0266: {Moulding; Pressing (H01F41/0273 takes precedence; hard magnetic particles H01F1/06, H01F1/11)}
- C01P 2002/50: Solid solutions
- C01P 2002/76: by a space-group or by other symmetry indications
- C01P 2004/04: obtained by TEM, STEM, STM or AFM
- C01P 2006/12: Surface area
- C01P 2006/42: Magnetic properties
- C04B 2235/3208: Calcium oxide or oxide-forming salts thereof, e.g. lime
- C04B 2235/3213: Strontium oxides or oxide-forming salts thereof
- C04B 2235/3217: Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina
- C04B 2235/3227: Lanthanum oxide or oxide-forming salts thereof
- C04B 2235/3272: Iron oxides or oxide forming salts thereof, e.g. hematite, magnetite
- C04B 2235/3274: Ferrites
- C04B 2235/3275: Cobalt oxides, cobaltates or cobaltites or oxide forming salts thereof, e.g. bismuth cobaltate, zinc cobaltite
- C04B 2235/3298: Bismuth oxides, bismuthates or oxide forming salts thereof, e.g. zinc bismuthate
- C04B 2235/3409: Boron oxide, borates, boric acids, or oxide forming salts thereof, e.g. borax
- C04B 2235/5409: expressed by specific surface values
- C04B 2235/5436: micrometer sized, i.e. from 1 to 100 micron
- C04B 2235/5445: submicron sized, i.e. from 0,1 to 1 micron
- C04B 2235/605: Making or treating the green body or pre-form in a magnetic field
- C04B 2235/6562: Heating rate
- C04B 2235/6565: Cooling rate
- C04B 2235/767: Hexagonal symmetry, e.g. beta-Si3N4, beta-Sialon, alpha-SiC or hexa-ferrites
- H02K 1/02: characterised by the magnetic material
- C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE
- C01G: COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F (metal hydrides {monoborane, diborane or addition complexes thereof} C01B6/00; salts of oxyacids of halogens C01B11/00; peroxides, salts or peroxyacids C01B15/00; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium, or tellurium C01B19/00; binary compounds of nitrogen with metals C01B21/06; azides C01B21/08; {compounds containing nitrogen, other non-metals and metal C01B21/082}; metal amides C01B21/092; nitrites C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; carbides C01B32/90; compounds containing silicon C01B33/00; compounds containing boron C01B35/00; compounds having molecular sieve properties but not having base-exchange properties C01B37/00; compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites, C01B39/00; cyanides C01C3/08; salts of cyanamide C01C3/16; thiocyanates C01C3/20)
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53})

## Abstract

This ferrite sintered magnet comprises metallic elements at an atomic ratio represented by formula (1): Ca1-w-xRwSrxFezCom (1) in formula (1), R is at least one element selected from the group consisting of rare-earth elements and Bi, and R comprises at least La, in formula (1), w, x, z and m satisfy formulae (2) to (5): 0.360≤w≤0.420 (2) 0.110≤x≤0.173 (3) 8.51≤z≤9.71 (4) 0.208≤m≤0.269 (5), and in a section parallel to an axis of easy magnetization, when the number of total ferrite grains is N and the number of ferrite grains having a stacking fault is n, 0≤n/N≤0.20 is satisfied.

## Claims

### Claim 1

A ferrite sintered magnet comprising ferrite grains having a hexagonal structure,
wherein the ferrite sintered magnet comprises metallic elements at an atomic ratio represented by formula (1):
Ca1-w-xRwSrxFezCom (1)
in formula (1), R is at least one element selected from the group consisting of rare-earth elements and Bi, and R comprises at least La, in formula (1), w, x, z and m satisfy formulae (2) to (5):
0.360≤w≤0.420 (2)
0.110≤x≤0.173 (3)
8.51≤z≤9.71 (4)
0.208≤m≤0.269 (5), and
in a section parallel to an axis of easy magnetization, when a number of total ferrite grains is N and a number of ferrite grains having a stacking fault is n, 0≤n/N≤0.20 is satisfied.

### Claim 2 (depends on 1)

The ferrite sintered magnet according to claim 1, further comprising 0.03 to 0.3% by mass of Al in terms of Al2O3.

### Claim 3 (depends on 1)

The ferrite sintered magnet according to claim 1, further comprising 0.037 to 0.181% by mass of B in terms of H3BO3.

### Claim 4 (depends on 2)

The ferrite sintered magnet according to claim 2, further comprising 0.037 to 0.181% by mass of B in terms of H3BO3.