US3846323A - Process for making a permanent magnet material - Google Patents

Process for making a permanent magnet material Download PDF

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Publication number
US3846323A
US3846323A US00283702A US28370272A US3846323A US 3846323 A US3846323 A US 3846323A US 00283702 A US00283702 A US 00283702A US 28370272 A US28370272 A US 28370272A US 3846323 A US3846323 A US 3846323A
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ions
product
ferrite
oxides
sintering
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US00283702A
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English (en)
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F Esper
G Kaiser
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Robert Bosch GmbH
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Robert Bosch GmbH
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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/26—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on ferrites
    • C04B35/2683—Other ferrites containing alkaline earth metals or lead

Definitions

  • the ferrite has a lattice structure of a strong uniaxial magnetic anisotropy and includes in its crystal structure a substitution element selected from the group consisting of Sb, As and P which has at least two valences of which the lowermost is 3 and which forms ions at both valenccs which have a radius substantially equal to or smaller than the radius of the Fe -ions of the ferrite which ions are unable to form a ferromagnetic coupling and which are substituted in their trivalent form for at least part of said Fe ions in at least one sublattice of said lattiee structure.
  • the material is made by sintering a finely ground mixture of the oxides or oxide furnishing compounds, then heat-treating the sintered product in such a manner that it releases part of its oxygen and that the ions are being converted in the lattice structure of the ferrite into their trivalent form; then comminuting the product to single domain grain size and finally tempering it in a nonoxidising atmosphere.
  • the object of the invention accordingly is to provide for a magnetic material and a process of making it wherein the material has a strong uniaxial magnetic anisotropy and assures a reversible temperature modification of the magnetic saturation moment.
  • the invention accordingly resides in a permanent magnet material which comprises a ferrite of the elements barium, strontium, or lead or a combination of these elements.
  • the ferrite has a lattice structure of a strong uniaxial magnetic anisotropy and includes in its crystal structure a substitution element which has at least two valences of which the lowermost is 3 and which forms ions at both valences which have a radius substantially equal to or smaller than the radius of the Fe ions of the ferrite which ions are unable to form a ferromagnetic coupling and which are substitutedin their trivalent form for at least part of said Fe ions in at least one sublattice of said lattice structure.
  • the material is made by sintering a finely ground mixture of the oxides or oxide furnishing compounds, then heat-treating the sintered product in such a manner that it releases part of its oxygen andthat the ions are being converted in the lattice structure of the ferrite into their trivalent form; then comminuting the product to single crystal grain size and finally tempering it in a nonoxidizing atmosphere.
  • FIG. 1 shows interrelation of temperature and magnetic saturation moments in barium ferrites of the invention which are substituted in FIG. 1 with arsenic and in FIG. 2 with antimony and are compared with ferrites which are not substituted in this manner.
  • the important points in the magnetic material of the invention include a substitution component which is constituted by an element, that has, at least two positive valences of which the lowermost valence is 3 while the higher valence or one higher valence preferably is 4 or 5.
  • the radius of the ions of the element at both valences approaches the ion radius of the Fe ions.
  • the mixture of the oxides used as starting products is first reacted by sintering in an oxidizing atmosphere and the product thus obtained is then subjected to a heat treatment in a suitable atmosphere for a time at a temperature to cause it to release part of its oxygen and to cause the ions of the substitution element to be converted in the crystal lattice of the ferrite into trivalent form.
  • a fine grinding is effected to single domain grain size and this is followed by a tempering operation in a nonoxidizing atmosphere.
  • the sintering operation may be effected at temperatures between l,l00 and 1,350C for 1 hour and the heat-treating step may be carried out at a temperature between l,200 and 1,350C for 1 hour in air or nitrogen.
  • substitution components are compounds of the elements Sb, As or P.
  • the substitution is made in a manner to cause 0.5 to l Fe ions to become substituted per molecular unit of ferrite. If the substitution is carried further a loss in the magnetic saturation moment will occur.
  • a heat treatment for removal of part of the oxygen preferably is effected in a manner to cause the product to release about 9% or 1 oxygen atom for each substi- 'tuted Fe ion depending upon whether 1 or 2 valences become available upon change of the substituting ion from its higher valence.
  • the magnetic material of the invention permits to cause a lowering of the temperature coefficient a of the reversible temperature change of the magnetic saturation moment afrom the value a 0.2 percent/C in normal Ba (Sr) ferrites to a value wherein a is about equal to 0.1 percent/C or below such figure and in parts of the product even to z 0. material.
  • the is accomplished without reducing the magnetic value to a level which would exclude the usefulness of the oxide magnetic material saturation moment 0 mentioned above is defined as follows:
  • FIG. 1 shows a barium ferrite substituted by arsenic as described in Example 1. Its magnetic saturation moment is interrelated with the temperature, being indicated by the solid line, while the dashed line illustrates for a comparison a barium ferrite of the same type which however is not substituted by'arsenic.
  • FIG. 2 is the same as FIG. 1 except that the barium ferrite in this case is substituted by antimony.
  • the ferrite and the-process of making it is described in Example l.
  • the comparison barium ferrite is not substituted by antimony.
  • oxides of the various elements are used or compounds may also be employed instead which furnish oxides during the sintering step.
  • the substitution element must comply with the specifications above given.
  • the components including the substitution element are then mixed in stoichiometric amounts as required by the intended final product.
  • the mixture is subjected to briquetting and in this form is sintered in air which causes a ferrite forming reaction.
  • the briquettes are then crushed, the fragments are ground and the ground product is again subjected to briquetting.
  • the product After the thermal treatment the product already has a crystal structure which is characterized by the decreased reversible temperature dependence of the magnetic saturation moment. It has however not yet a microstructure which permits to attain the optimum value of the coercive force ,H For this reason a further treatment in two steps is preferred: (1) a fine grinding is effected to single domain range and (2) a tempering is carried out in a nonoxidizing atmosphere.
  • the tempering step is in any case necessary if the material resulting from the fine grinding is intended to form a magnetic body in which a synthetic binder is used. On the other hand if sintered shaped bodies are made from the material the sintering which is necessary in this connection will have the same effect. However it will in either case be a condition that a nonoxidizing atmosphere must be used.
  • EXAMPLE 1 As substituted Ba-ferrite
  • the ferrite formed in this example has the empirical formula BaO (As O (Fe O wherein one-half As ion is substituted in each molecular unit.
  • the product then was subjected to an aftertreatment consisting of a coarse comminution followed by wet grinding (in H O) for half an hour in a disk mill down to a grain size corresponding to 4 m /g of specific surface.
  • the mass was then dried and a shaped body was formed by a pressing operation.
  • the body was then subjected to renewed sintering for 1 hour at l,l00C in nitrogen.
  • the coercive force of the final shaped body was as follows: ,H 1,550 Oe.
  • the solid curve in FIG. 1 shows the magnetic saturation moment of the As substituted ferrite and the interrelation with the temperature while as above indicated the dashed curve shows the same relation for a nonsubstituted Ba ferrite.
  • Empirical formula BaO (Sb O (Fe O substitution one-half Sb-ion per molecular unit.
  • a process of making a permanent magnet material comprising the steps of forming a particulate mixture including a substance selected from the group consisting of the oxides and oxide furnishing compounds of Fe, a substance selected from the group consisting of the oxides and oxide furnishing compounds of Ba, Sr and Pb, and a substance selected from the group consisting of the oxides and oxide furnishing compounds of Sb, As and P; sintering said mixture in air so as to effect reaction of said substances and form a first product of the formula MO(Fe O wherein Fe ions in said first product are replaced by the ions of at least one of said Sb, As and P to such an extent as to cause a lowering ofthe temperature coefficient of the reversible temperatfire change of the magnetic saturation moment from that of MO-(Fe O wherein no replacement of the Fe* ions is effected, said ions of said Sb, As and P having a valence in excess of +3, and said M of said MO-(- Fe O being at least one of said Ba, Sr and
  • tempering step comprises sintering said shaped body 5.
  • said sintering step is carried out at a temperature between substantially l,100 and 1,350C.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Hard Magnetic Materials (AREA)
  • Magnetic Ceramics (AREA)
  • Compounds Of Iron (AREA)
US00283702A 1971-09-01 1972-08-25 Process for making a permanent magnet material Expired - Lifetime US3846323A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE2143718A DE2143718C3 (de) 1971-09-01 1971-09-01 Verfahren zur Herstellung von Dauermagnetwerkstoffen aus Ferriten

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US00283702A Expired - Lifetime US3846323A (en) 1971-09-01 1972-08-25 Process for making a permanent magnet material

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US (1) US3846323A (Direct)
JP (1) JPS4835398A (Direct)
AT (1) AT329291B (Direct)
CH (1) CH568644A5 (Direct)
DE (1) DE2143718C3 (Direct)
FR (1) FR2151065B1 (Direct)
GB (1) GB1364953A (Direct)
IT (1) IT964392B (Direct)
NL (1) NL7211869A (Direct)
SE (1) SE388068B (Direct)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4308155A (en) * 1976-11-24 1981-12-29 Tdk Electronics Co., Ltd. Rubber or plastic magnet and magnetic powder for making the same
US4454494A (en) * 1981-04-07 1984-06-12 Lucas Industries Plc Oxygen sensors
WO1992020247A1 (en) * 1991-05-14 1992-11-26 Power Fardy Stephen N Self-contained display device for headwear
CN102473499A (zh) * 2009-07-08 2012-05-23 Tdk株式会社 铁氧体磁性材料

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5314675B2 (Direct) * 1973-07-27 1978-05-19

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2837483A (en) * 1954-04-20 1958-06-03 Philips Corp Method of making a permanent magnet
US2900344A (en) * 1953-07-29 1959-08-18 Philips Corp Making anisotropic permanent magnets
US3563899A (en) * 1967-06-02 1971-02-16 Lucas Industries Ltd Permanent magnet material having strontium ferrite base

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2900344A (en) * 1953-07-29 1959-08-18 Philips Corp Making anisotropic permanent magnets
US2837483A (en) * 1954-04-20 1958-06-03 Philips Corp Method of making a permanent magnet
US3563899A (en) * 1967-06-02 1971-02-16 Lucas Industries Ltd Permanent magnet material having strontium ferrite base

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4308155A (en) * 1976-11-24 1981-12-29 Tdk Electronics Co., Ltd. Rubber or plastic magnet and magnetic powder for making the same
US4454494A (en) * 1981-04-07 1984-06-12 Lucas Industries Plc Oxygen sensors
WO1992020247A1 (en) * 1991-05-14 1992-11-26 Power Fardy Stephen N Self-contained display device for headwear
CN102473499A (zh) * 2009-07-08 2012-05-23 Tdk株式会社 铁氧体磁性材料
US20120161062A1 (en) * 2009-07-08 2012-06-28 Tdk Corporation Ferrite magnetic material
EP2453449A4 (en) * 2009-07-08 2013-04-03 Tdk Corp FERRITE MAGNETIC MATERIAL
US8834738B2 (en) * 2009-07-08 2014-09-16 Tdk Corporation Ferrite magnetic material
US9336933B2 (en) 2009-07-08 2016-05-10 Tdk Corporation Ferrite magnetic material

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Publication number Publication date
IT964392B (it) 1974-01-21
ATA715072A (de) 1975-07-15
CH568644A5 (Direct) 1975-10-31
AT329291B (de) 1976-05-10
GB1364953A (en) 1974-08-29
DE2143718C3 (de) 1978-08-17
FR2151065A1 (Direct) 1973-04-13
DE2143718A1 (de) 1973-03-08
JPS4835398A (Direct) 1973-05-24
FR2151065B1 (Direct) 1976-05-21
NL7211869A (Direct) 1973-03-05
SE388068B (sv) 1976-09-20
DE2143718B2 (de) 1977-12-15

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