US3837910A - Method of manufacturing a polycrystalline ferrite body - Google Patents

Method of manufacturing a polycrystalline ferrite body Download PDF

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Publication number
US3837910A
US3837910A US00186254A US18625471A US3837910A US 3837910 A US3837910 A US 3837910A US 00186254 A US00186254 A US 00186254A US 18625471 A US18625471 A US 18625471A US 3837910 A US3837910 A US 3837910A
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sintering
ferrite
temperature
hours
percent
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US00186254A
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English (en)
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Der Laan K Van
H Peloschek
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US Philips Corp
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US Philips Corp
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Priority claimed from NL7014697A external-priority patent/NL7014697A/xx
Priority claimed from NL7111359A external-priority patent/NL7111359A/xx
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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
    • C04B35/2658—Other ferrites containing manganese or zinc, e.g. Mn-Zn ferrites
    • 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
    • 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
    • C04B35/265—Compositions containing one or more ferrites of the group comprising manganese or zinc and one or more ferrites of the group comprising nickel, copper or cobalt
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S264/00—Plastic and nonmetallic article shaping or treating: processes
    • Y10S264/58—Processes of forming magnets

Definitions

  • the invention relates to a method of manufacturing a polycrystalline ferrite body, wherein a finely divided ferrite-forming starting mixture is formed, ground, pressed into a body having a desired shape and sintered.
  • a ferrite is to be understood to mean herein a crystalline reaction product of the oxides of iron and one or more other bivalent metals or bivalent metallic complexes.
  • bodies of sintered oxidic ferromagnetic material for which material the name ferrite is generally used, are used inter alia as cores for electromagnetic transducers for converting electric signal variations into variations of the magnetic inductance, or conversely.
  • electromagnetic transducers or magnetic heads
  • a rapidly moving magnetic record carrier for example a magnetic tape
  • the magnetic properties of the material and in particular the resistance to detrition are of great importance.
  • Two types of detrition are to be distinguished, the first type which is related to the hardness of the material used, manifests itself as a uniform overall reduction of the material of the contact surface of the transducer. The characteristics of the transducer in itself is not influenced by it.
  • the second type which is inherent to the polycrystalline structure of the material used, manifests itself as a crumbling away of ferrite crystals out of the contact surface of the transducer under the influence of the scouring effect of the record carrier.
  • the invention provides a polycrystalline ferrite, having improved resistance to crumbling away.
  • a quantity of a material promoting grain growth or a combination of such materials chosen from the group consisting of BaF SrF the oxides of B, Bi, Ca, Cu, Mg, Pb, Si, V and Fe (PO is added to the ferrite-forming system during a manufacturing step preceding the sintering, such a combination of added quantity and sintering temperature being chosen, that interdigitated crystals of an average grain size of more than 50 microns are obtained.
  • the addition of the grain growthpromoting material or combination of such materials is made to the starting material to be ground. It is to be noted in that case the spreading in the average grain size may be very small, that is to say that so-called duplex structures do not occur.
  • the ferrite-forming starting mixture after grinding is preferably first pre-sintered and ground again before it is compressed to the desirable shape and sintered.
  • a pre-sintered powder is used.
  • the method according to the invention may be varied so that the desirable crystal structure which is resistant to detrition occurs only at the surface or a part of the surface and that the internal structure is finegranular which is a condition for good electric and magnetic properties.
  • a further preferred embodiment of the method according to the invention is characterized in that the ferrite-forming starting mixture is compressed and pre-sintered, if desired, that the grain growth-promoting material or combination of materials is locally provided on the outside of the body obtained after compressing and possible pre-sintering, and that said body is then sintered.
  • the method according to the invention may also be varied so that the final product as such has a fine-granular structure but shows paths or patterns which consist of interdigitated crystals having an average grain size of more than 50 microns.
  • Another preferred embodiment of the method according to the invention is therefore characterized in that the grain growth-promoting material or combination of materials is added to the starting mixture, that same is ground, compressed and presintered, and that the body obtained after compression and presintering is locally heated, during sintering, at a sintering temperature such that the desirable crystal structure occurs only at that region.
  • Local heating to the sintering temperature can be realized, for example, by means of a laser beam or by means of a Pt-wire through which a current is conveyed.
  • Certain grain growth-promoting materials have turned out to be very effective within the scope of the present invention, provided the correct combination of added quantity and sintering temperature is found.
  • Ni-Zn ferrite body from 0.001 to 1 weight percent is added of the mixture determined by its molecular composition: X8203 ySiO zCaO, with 1 s. X s 10; s y s 0 s z s 5, the sintering temperature lying between 1,180C and 1,275 C.
  • a ferrite body can be obtained having interdigitated crystals with an average grain size of more than 50 microns. It is to be noted that the spreading in the average grain size can be very small. This means that so called duplex structures do not occur. It is furthermore to be noted that the magnetic and electrical properties of the ferrite bodies obtained in this manner are acceptable in all respects.
  • the above-mentioned addition provides the desirable crystal structure, attention should also be paid to other properties.
  • the crystal boundaries should be clean and comprise no large pores. This can be achieved by causing the addition to be 0.007 to 0.25 percent by weight of the starting mixture.
  • the addition is characterized by the following molecular composition: 213 0 SiO the sintering temperature lying between 1,180 C and 1,240 C. It has been found that, in particular after sintering of the compressed powder at a temperature between 1,220 C and 1',230 C, a product of maximum average grain size 500 microns) can be obtained.
  • the addition is characterized by the following molecular composition: B 0 2Si0 CaO.
  • the addition is characterized by the following molecular composition: B 0 2SiO and the sintering temperatures lies between 1,240 C and 1,300 C. It has been found that, after sintering of the ground and compressed powder, a product is obtained having a combination of a high initial permeability 41., and a high density.
  • Ni-Zn ferrite bodies In manufacturing Ni-Zn ferrite bodies, the addition of Ca0 B 0 has furthermore turned out to be very effective. According to a preferred embodiment of the method according to the invention from 0.01 to 0.2 percent by weight of Ca0 B 0 is added during the manufacture of a Ni-Zn ferrite body and sintering takes place at a temperature between 1,175" C and 1,250 C, preferably between 1,200 C and 1,250 C.
  • Another preferred embodiment of the method according to the invention is characterized in that during the manufacture of a Ni-Zn ferrite body from 0.05 to 0.5 percent by weight of BaF and/or SrF is added and that sintering is carried out at the temperature between 1,200 C and 1,250 C.
  • Another preferred embodiment of the method according to the invention is characterized in that during the. manufacture of a Ni-Zn ferrite body from 0.05 to 0.5 percent by weight of BiF O is added and that sintering is carried out at a temperature between 1,175 C and 1,275 C.
  • a preferred embodiment of the method according to the invention is characterized in that during the manufacture of a Mn-Zn ferrite body from 0.005 to 0.06 percent by weight of Ca0 B 0 is added and that sintering is carried out in an oxygencontaining atmosphere at a temperature between 1,350 C and 1,400 C.
  • a further preferred embodiment of the method according to the invention is characterized in that during the manufacture of a Mn-Zn ferrite body from 0.005 to 1 percent by weight of the mixture x B 0 y SiO zFe (PO,) whereinO x l;0 s y s 1;0 s 2 as 1 determined by its molecular composition is added and that sintering is carried out in an oxygencontaining atmosphere at a temperature between 1,350 C and 1,400 C.
  • Still a further preferred embodiment of the method according to the invention is characterized in that during manufacture of a Mn-Zn ferrite body from 0.005 to 0.5 percent by weight of BaF is added and that sintering is carried out in an oxygen-containing atmosphere at a temperature between 1,350 C and 1,400 C.
  • Another further preferred embodiment of the method according to the invention is characterized in that during the manufacture of a Mn-Zn ferrite body from 0.005 to 0.05 percent by weight of V 0 is added and that sintering is carried out in an oxygencontaining atmosphere at a temperature between 1,375 C and 1,400 C.
  • the invention also relates to a sintered oxidic ferromagnetic body manufactured by using one or more of the above-mentioned methods.
  • EXAMPLE 1 To ferrite-forming systems of the composition 49.50 49.99 mol percent Fe O NiO and ZnO according to the proportion 18 32 was added a series of additions (0.01 percent by weight, 0.81 percent by weight and 1 percent by weight) of grain growth promoting materials.
  • Each of the resulting mixtures was pre-ground for 6 hours in a ball mill which also contained a grinding liquid and then prefired in oxygen at a temperature of 850 C for 3 hours. The mixtures were then postground for 16 hours.
  • the powders obtained in this manner (grain size from 0.1 to a few microns) were precompressed to blocks at a pressure of 10 kg per cm and post-compressed in an isostatic pressure vessel at a pressure of 1,000 kg/cm
  • the compressed product was sintered for 24 hours at temperatures of 1,180 C, l,200 C, 1,225 C, 1,250 C and 1,275 C, respectively, in a furnace containing an oxygen-containing atmosphere, for example air or a relatively more oxygencontaining atmosphere.
  • the heating time was 16 hours and the cooling time was 24 hours.
  • the resulting products were polished and etched at one of their surfaces so as to evaluate their crystal structure.
  • An average crystal size was determined with reference to microphotographs by dividing the distance covered during traversing by the number of crystal boundaries which is passed during covering said distance, in which of course the magnification standard 5 should be taken into account.
  • the average grain sizes found in this manner are represented in Table I as a function of the addition and of the sintering temperature for a sintering time of 24 hours.
  • the average grain size of NiZn-ferrite manufactured in the usual manner is l0 to 20 microns
  • FIGURE represents the average grain size (in microns) as a function of the added quantity in percent by weight and of the sintering temperature T. It is obvious that a maximum average crystal growth (250 ,u.) is obtained with a very particular combination of sintering temperature and added quantity.
  • drawing of equal average grain size can slightly shift as chosen to be higher than in Example 1, namely from a whole relative to the axes. 1,200 to 1,400 C.
  • composition means that sintering was carried out at a temperature of l,300 C in air for 2 hours. 52'75 mol Fego Condition B means that sintering was carried out at 22 mol ZnO a temperature of 1,370 C in 100 percent oxygen for 5 25 mol Mno 5 hours so as to obtain the desirable crystal structure.
  • Condition C means that sintering was carried out at a temperature of L390 C in 100 percent oxygen for 5
  • the starting mixture was t eated I the Same manner hours so as to obtain the desirable crystal structure. as in Example I.
  • each mixture was pre- In the cases B and C, afterfining may then be carried ground in a ball mill for 6 hours and than pre-fired in 20 out at a lower temperature f example, ⁇ 290 C) f air at a temperature of 850C for 4 hours.
  • the mixture a few hours (for example 3 hours) in an atmosphere was then post-ground for 6 hours.
  • the powders obcontaining 0.1 percent oxygen so as to adjust the ferrotained in this manner were pre-compressed to blocks at ferri equilibrium, after which conditioned cooling may a pressure of 10 kg/sq.cm and post-compressed in an be carried out, for example, in a nitrogen atmosphere.
  • One half of the investigated samples were manufactured by grinding a (Ni-Zn) ferrite-forming mixture for 6 hours, presintering it at a temperature of 850 C in an oxygen-containing atmosphere for 3 hours, postgrinding for 16 hours, pre-compressing, isostatic postcompressing at a pressure of I00 kg/sq.cm, after which a layer of grain growth-promoting material was provided, and sintering for 24 hours in oxygen at a temperature of l,240 C. Samples manufactured in this manner turned out to yield no useful result.
  • the other half of the samples was manufactured by grinding a (Ni-Zn) ferrite-forming mixture for 6 hours, pre-sintering for 3 hours, post-grinding, precompressing and isostatically post-compressing at a pressure of 1,000 kg/sq.cm, after which a layer of grain growth-promoting material was provided on the surface.
  • a layer of grain growth-promoting material was provided on the surface.
  • the material to be provided is available in powder form, it can be provided directly on the compressed body.
  • the desired crystal structure occured without an exception after providing each of the above-mentioned grain growth-promoting materials followed by sintering.
  • the desired crystal structure turned out to be restricted most to the surface and the least deformation of the surface also occurred.
  • EXAMPLE IV A number of detrition experiments was carried out both in magnetic heads of normal Ni-Zn ferrite having regularly shaped crystals and an average grain size of from 10 to microns, and in magnetic heads manufactured from Ni-Zn ferrite having interdigitated crystals having an average grain size of more than 50 microns manufactured while using the method according to the invention.
  • a method of manufacturing a detrition-resistant polycrystalline ferrite body comprising the steps of forming a finely-divided mixture of iron oxide, zinc oxide, and an oxide selected from the group consisting of nickel and manganese in proportions forming upon heating at an elevated temperature a nickel-or manganese-zinc ferrite, forming a body of said mixture, covering said body with a material promoting grain growth and selected from the group consisting of Ba F Sr F an oxide selected from the group consisting of B, Bi, Ca, Cu, Mg, Pb, Si, V, and Fe (P09 and thereafter sintering said body in an oxygen-containing atmosphere at a temperature of about l,l to 1,400C to form a coherent ferrite body having a surface structure of interdigitated crystals of an average grain size of more than 50 microns.

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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)
  • Soft Magnetic Materials (AREA)
  • Magnetic Ceramics (AREA)
US00186254A 1970-10-07 1971-10-04 Method of manufacturing a polycrystalline ferrite body Expired - Lifetime US3837910A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL7014697A NL7014697A (en) 1970-10-07 1970-10-07 Polycrystalline ferrites - contg grain growth promoters added before sintering
NL7111359A NL7111359A (en) 1971-08-18 1971-08-18 Polycrystalline ferrites - contg grain growth promoters added before sintering

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US3837910A true US3837910A (en) 1974-09-24

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US (1) US3837910A (OSRAM)
JP (1) JPS5229439B1 (OSRAM)
AT (1) AT313600B (OSRAM)
BE (1) BE773528A (OSRAM)
CA (1) CA975154A (OSRAM)
DE (1) DE2148554A1 (OSRAM)
FR (1) FR2111100A5 (OSRAM)
GB (1) GB1369493A (OSRAM)

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4521323A (en) * 1984-06-27 1985-06-04 Matsushita Electric Industrial Co., Ltd. Polycrystalline ferrite and a magnetic head using the same
US4877543A (en) * 1987-06-19 1989-10-31 Mitsubishi Denki Kabushiki Kaisha Low loss oxide magnetic material
US4985167A (en) * 1988-07-18 1991-01-15 Mitsubishi Denki Kabushiki Kaisha Low-loss oxide magnetic material
US5028348A (en) * 1988-12-19 1991-07-02 Murata Manufacturing Co., Ltd. Magnetic material for high frequencies
US5498361A (en) * 1992-12-28 1996-03-12 Tdk Corporation Manganese-zinc system ferrite
US5576912A (en) * 1991-10-22 1996-11-19 Hitachi Metals Limited Floating magnetic head with reduced magnetostriction vibration noise
US5645774A (en) * 1989-09-19 1997-07-08 Ferronics Incorporated Method for establishing a target magnetic permeability in a ferrite
US6423243B2 (en) 1999-09-17 2002-07-23 Tdk Corporation Manganese-zinc base ferrite
US20030139787A1 (en) * 2002-01-18 2003-07-24 Eggers Philip E. System method and apparatus for localized heating of tissue
US20040122494A1 (en) * 2002-01-18 2004-06-24 Eggers Philip E. System, method and apparatus evaluating tissue temperature
US20050099731A1 (en) * 2003-11-12 2005-05-12 Brink Damon D. Remelted magnetic head support structure in a disk drive
US6909395B1 (en) * 1975-04-10 2005-06-21 The United States Of America As Represented By The Secretary Of The Air Force Radar absorbing coatings

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2992990A (en) * 1956-01-05 1961-07-18 Richard G Parker Soft magnetic material
US3002930A (en) * 1956-12-03 1961-10-03 Philips Corp Process of making a ferromagnetic body
US3671436A (en) * 1969-03-20 1972-06-20 Philips Corp Method of manufacturing a sintered oxidic ferromagnetic body

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2992990A (en) * 1956-01-05 1961-07-18 Richard G Parker Soft magnetic material
US3002930A (en) * 1956-12-03 1961-10-03 Philips Corp Process of making a ferromagnetic body
US3671436A (en) * 1969-03-20 1972-06-20 Philips Corp Method of manufacturing a sintered oxidic ferromagnetic body

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6909395B1 (en) * 1975-04-10 2005-06-21 The United States Of America As Represented By The Secretary Of The Air Force Radar absorbing coatings
US4521323A (en) * 1984-06-27 1985-06-04 Matsushita Electric Industrial Co., Ltd. Polycrystalline ferrite and a magnetic head using the same
US4877543A (en) * 1987-06-19 1989-10-31 Mitsubishi Denki Kabushiki Kaisha Low loss oxide magnetic material
US4985167A (en) * 1988-07-18 1991-01-15 Mitsubishi Denki Kabushiki Kaisha Low-loss oxide magnetic material
US5028348A (en) * 1988-12-19 1991-07-02 Murata Manufacturing Co., Ltd. Magnetic material for high frequencies
US5645774A (en) * 1989-09-19 1997-07-08 Ferronics Incorporated Method for establishing a target magnetic permeability in a ferrite
US5576912A (en) * 1991-10-22 1996-11-19 Hitachi Metals Limited Floating magnetic head with reduced magnetostriction vibration noise
US5498361A (en) * 1992-12-28 1996-03-12 Tdk Corporation Manganese-zinc system ferrite
US6423243B2 (en) 1999-09-17 2002-07-23 Tdk Corporation Manganese-zinc base ferrite
US20030139787A1 (en) * 2002-01-18 2003-07-24 Eggers Philip E. System method and apparatus for localized heating of tissue
US20040122494A1 (en) * 2002-01-18 2004-06-24 Eggers Philip E. System, method and apparatus evaluating tissue temperature
US6993394B2 (en) 2002-01-18 2006-01-31 Calfacion Corporation System method and apparatus for localized heating of tissue
US7048756B2 (en) 2002-01-18 2006-05-23 Apasara Medical Corporation System, method and apparatus for evaluating tissue temperature
US20050099731A1 (en) * 2003-11-12 2005-05-12 Brink Damon D. Remelted magnetic head support structure in a disk drive
US7450344B2 (en) * 2003-11-12 2008-11-11 Intri-Plex Technologies, Inc. Remelted Magnetic head support structure in a disk drive

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Publication number Publication date
FR2111100A5 (OSRAM) 1972-06-02
GB1369493A (en) 1974-10-09
AT313600B (de) 1974-02-25
DE2148554A1 (de) 1972-04-13
CA975154A (en) 1975-09-30
BE773528A (fr) 1972-04-05
JPS5229439B1 (OSRAM) 1977-08-02

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