US2565111A - Ceramic magnetic material with a small temperature coefficient - Google Patents

Ceramic magnetic material with a small temperature coefficient Download PDF

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US2565111A
US2565111A US95582A US9558249A US2565111A US 2565111 A US2565111 A US 2565111A US 95582 A US95582 A US 95582A US 9558249 A US9558249 A US 9558249A US 2565111 A US2565111 A US 2565111A
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Albers-Schoenberg Ernst
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Steatite Research Corp
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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
    • C04B35/2608—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
    • C04B35/2625—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 containing magnesium

Definitions

  • This invention relates to a ceramic magnetic material, especially for transformer and inductance coils, with ;a small temperature coefficient and to the process of making the material.
  • ferrite compounds have been developed and described in the technical literature, i. e. ferromagnetic oxides of the general formula MFe2O4, where M represents a bivalent metal as, for instance, manganese, copper of magnesium.
  • M represents a bivalent metal as, for instance, manganese, copper of magnesium.
  • ferromagnetic oxides of the general formula MFe2O4, where M represents a bivalent metal as, for instance, manganese, copper of magnesium.
  • M represents a bivalent metal as, for instance, manganese, copper of magnesium.
  • An object of the invention is to provide a ferromagnetic compound having better than average magnetic properties such as permeability, initial permeability, Curie point and magnetic losses and at'the same time having a very small temperature coefficient of n. 1
  • Another object of the invention is to provide a ferromagnetic compound having better than average magnetic properties such as permeability,
  • Another object of the invention is to provide a shaped ferromagnetic body having a Curie point of 250 C. or higher, small magnetic losses and at the same time having a very small temperature coefficient and said body consisting of a crystalline cubic phase and a glassy intercrystalline phase.
  • Another object of the invention is to provide a process of making such products.
  • Such ferrite compounds have an initial permeability of between about and 150, small magnetic losses over the frequency range of cs. to about 30 mos, a Curie point of 250 C. or higher, a temperature coefficient measured on toroidal cores of not more than 10% for C. temperature increase. This figure of 10% corresponds to a much smaller figure of 1 to 2% only, if the material is used as a cylindrical core in an inductance coil.
  • Coils equipped with cores of such materials show no higher temperature coeii'icient than an air coil.
  • the fired product would consist of a polycrystalline aggregate presenting only one phase. Materials of this kind are somewhat unfavorable on two accounts. It is known that crystalline aggregates without any intermediate glassy phase sometimes have a tendency to disintegrate. This effect, for instance, is well known from the magnesium silicates which, if formed of merely MgSiOs crystals lacking a protective glassy phase, can disintegrate within a few days after firing into a fine powder. Even if the disintegration does not progress to completion a noticeable change of the physical properties may take place.
  • silica In the second place, in the special case of magnetic iron oxides an intermediate glassy phase created by the addition of silica improves not only the insulating properties, diminishing some losses, but eifects also a considerable decrease of the temperature-coefficient of the magnetic permeability. It goes without saying that the silica has to be added in a very finely divided state to be sufiiciently reactive. To facilitate and to support the formation of the glassy phase one or more oxides of univalent elements such as lithium, sodium or potassium may be added in amounts up to about 0.05 mol.
  • the components which appear in the final product are not necessarily added to the composition in that form.
  • manganese is usually added in the form of the dioxide, but during the firing process it is changed to the monoxide.
  • lithium, sodium and potassium oxides are desired in the final product the carbonates of these metals are usually added to the original composition.
  • the various components of the powder from which the products are molded are ground and mixed together by milling, etc.
  • the powders are preferably ground ver fine, to less than 0.010 m. m., for example.
  • the mixed powders are moistened with just enough aqueous liquid to make the unfired product adhere when molded.
  • the aqueous liquid may be ordinary water or it may be water having wax or other binding material emulsified therein.
  • the moistened powder may be molded in a steel die or other ceramic molding machine such as an extrusion machine. The molded product must be fired at a temperature high enough to cause a phase separation between the cubic crystalline ferrite materials and the glassy
  • Example 1 A mix of the following ingredients in the proportions indicated is compounded:
  • Example 3 A mix is made up of the following ingredients in the proportions indicated:
  • a ferromagnetic ceramic material consisting mainly of iron oxide compounds of the magnetitetype, suitable for the use at frequencies between 60 es. and about 30 mos, composed of the four bivalent metal oxides, MgO, MnO, ZnO, and NiO, silica and F6203, in the mol ratio of .05-.35 MgO .10-.25 MnO .15-.30 ZnO .15-.40 N10 .10-.20 S102 about 1 F6203 the total mol proportion of the bivalent metal oxides to F8203 being approximately 1:1 said material having'a Curie point of at least 250 C. an initial permeability between 50 and and a temperature coefficient of a (measured on a toroid) of less than 10% between room temperature and 120 C.
  • a shaped ferromagnetic ceramic article consisting mainly of iron oxide compounds of the magnetite type, composed of MgO, MnO, ZnO, NiO, F8203 the total mol proportion of the bivalent metal oxides being approximately equal to the mol proportion of F9203 and an amount of about .2 mol of silica (per mol proportion of F8203) said material forming a heterogeneous body of a crystalline cubic phase and a glassy intercrystalline phase, the material of said article having a Curie point of at least 250 C'. an initial permeability of about 50 to 150 and a temperature coefiicient of a (measured on a toroid) of less than 10% between room. temperature and 3.
  • a ferromagnetic ceramic material consisting essentially of iron oxide compounds of the magnetite type, composed of about 1 mol proportion of MgO, MnO, ZnO and N10, 1 mol total proportion of F6203 and an amount of about .1.2 mol of silica and about 0.05 mol of an univalent metal oxide, per mol proportion of F8203, said material consisting of a heterogeneous body of a crystalline cubic phase and a glassy intercrystalline phase and 9, having a Curie point of at least 250 0., an initial permeability of about 50 to 150 and a temperature coefiicient of ,1 (measured on a toroid) of less than between room temperature and 100 C.
  • a process of makin a shaped ferromagnetic body consisting essentially of iron oxide compounds of the magnetite type, which body consists of a heterogeneous body having a crystalline cubic phase and a glassy intercrystalline phase comprising the steps of mixing together F6203 and compounds of Mg, Mn, Zn, and Ni adapted to appear in the final prdouct after firing as MgO, MnO, ZnO, NiO the mol proportion of the Fezos being approximately equal to the total mol proportion of the first four oxides, adding about 0.10 to 0.20 mol proportion of the finely divided SiOz based on the mols of Fe2o3 present,
  • a process of making a shaped ferromagnetic body consisting essentially of iron oxide compounds of the magnetite type, which body consists of a heterogeneous body having a crystalline cubic phase and a glassy intercrystalline phase comprising the steps of mixing together powdered MgO, MnOz, ZnO, N10, and F8203 the mol proportion of the F6203 being approximately equal to the total mol proportion of the first four oxides, adding about 0.10 to 0.20 mol proportion of finely divided 8102 based on the mols of F6203 present, and less than 0.05 mol proportion of L (on the same basis) moistening and plasticizing the mix, with a wax emulsion, molding the mix to the desired shape and firing the molded product at a temperature to produce a two phase system consisting of a cubic crystalline phase and a glassy intercrystalline phase.

Description

pounds are not those Patented Aug. 21, 1951 CERAMIC MAGNETIC MATERIAL WITH A SMALL TEMPERATURE. COEFFICIENT Ernst Albers-Schoenberg, Metuchen, N. J., as-
signor to Steatite Research Corporation, 1Keasbey, N. J., a corporation of Delaware No Drawing. Application May 26, 1949,
1 Serial No. 95,582
6 Claims. (01. 252 -625) This invention relates to a ceramic magnetic material, especially for transformer and inductance coils, with ;a small temperature coefficient and to the process of making the material.
Recently a number of ferrite compounds have been developed and described in the technical literature, i. e. ferromagnetic oxides of the general formula MFe2O4, where M represents a bivalent metal as, for instance, manganese, copper of magnesium. Each of these ferrites which form crystals of the same shape as the magnetite, F8304, has a different magnetic permeability ohmic resistance, Curie point and magnetic losses. On the whole, these compounds or suitable mixtures of them cover a rangeo'f initial permeability (,uo) from very low figures below 30 up to high values of more than 1000, the ohmic resistance varying between 10 to 10 ohms cm. As a rough rule it has been found that the highest initial permeability is associated with a fairly low Curie point, while Curie temperatures above 200 C. are found to be related to a medium or a low initial permeability and the conductivity, which always shows an increasing tendency with an increase f 11..
There exists an analogy in some extent between the dielectrics based on titania and titania compounds and the ferromagnetic ceramic bodies, as the dielectric constant K can be compared to the permeability and the dielectric losses to the magnetic losses. But in the field of dielectrics it I has been proved,- that the most valuable comwith the highest possible K because the variation of K with temperature of these bodies is so large that condensers, made of such bodies have an intolerable deficiency in temperature constancy. The most valuable dielectrics, therefore, especially for high frequencydevices, have been found on a lower K-level, where, besides a low-power factor, temperatures coefficients of K close to zerocan be obtained.
1 An object of the invention is to provide a ferromagnetic compound having better than average magnetic properties such as permeability, initial permeability, Curie point and magnetic losses and at'the same time having a very small temperature coefficient of n. 1
Another object of the invention is to provide a ferromagnetic compound having better than average magnetic properties such as permeability,
initial permeability, Curie point and magnetic losses and at the same time having a temperature coefficient which is no higher than that of an air coil.
Another object of the invention is to provide a shaped ferromagnetic body having a Curie point of 250 C. or higher, small magnetic losses and at the same time having a very small temperature coefficient and said body consisting of a crystalline cubic phase and a glassy intercrystalline phase.
Another object of the invention is to provide a process of making such products.
These objects and others ancillary thereto are obtained by combining four bivalent oxides, MgO, MnO, ZnO and NiO and F8203 and a small amount of $5.02. The mol ratio between the total amount of bivalent oxides and the F8203 must be approximately 1:1. The mol ratio between the bivalent oxides and the S102 lies within the limits of 05-35 MgO .10-.25 MnO .15-.30 ZnO: .5-.40 NiO .10-.20 SiOz. Extremely small temperature coefilcients are attained, if the mol ratio lies within the range of .20-.30 MgO .l0-.15 MnO .20-.30 ZnO .15- -.20 NiO .15.20 S102.
Such ferrite compounds have an initial permeability of between about and 150, small magnetic losses over the frequency range of cs. to about 30 mos, a Curie point of 250 C. or higher, a temperature coefficient measured on toroidal cores of not more than 10% for C. temperature increase. This figure of 10% corresponds to a much smaller figure of 1 to 2% only, if the material is used as a cylindrical core in an inductance coil.
Coils equipped with cores of such materials show no higher temperature coeii'icient than an air coil.
If these bodies would be prepared of only the pure bivalent oxides and the trivalent F8203 the fired product would consist of a polycrystalline aggregate presenting only one phase. Materials of this kind are somewhat unfavorable on two accounts. It is known that crystalline aggregates without any intermediate glassy phase sometimes have a tendency to disintegrate. This effect, for instance, is well known from the magnesium silicates which, if formed of merely MgSiOs crystals lacking a protective glassy phase, can disintegrate within a few days after firing into a fine powder. Even if the disintegration does not progress to completion a noticeable change of the physical properties may take place. In the second place, in the special case of magnetic iron oxides an intermediate glassy phase created by the addition of silica improves not only the insulating properties, diminishing some losses, but eifects also a considerable decrease of the temperature-coefficient of the magnetic permeability. It goes without saying that the silica has to be added in a very finely divided state to be sufiiciently reactive. To facilitate and to support the formation of the glassy phase one or more oxides of univalent elements such as lithium, sodium or potassium may be added in amounts up to about 0.05 mol.
The components which appear in the final product are not necessarily added to the composition in that form. For example, manganese is usually added in the form of the dioxide, but during the firing process it is changed to the monoxide. When lithium, sodium and potassium oxides are desired in the final product the carbonates of these metals are usually added to the original composition. The various components of the powder from which the products are molded are ground and mixed together by milling, etc. The powders are preferably ground ver fine, to less than 0.010 m. m., for example. The mixed powders are moistened with just enough aqueous liquid to make the unfired product adhere when molded. The aqueous liquid may be ordinary water or it may be water having wax or other binding material emulsified therein. The moistened powder may be molded in a steel die or other ceramic molding machine such as an extrusion machine. The molded product must be fired at a temperature high enough to cause a phase separation between the cubic crystalline ferrite materials and the glassy constituents.
The novel features characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of specific embodiments when read in connection with the accompanying examples:
Example 1 A mix of the following ingredients in the proportions indicated is compounded:
Mol ratio: .20 MgO:.15 MnO:.25 ZnO:.20 NiOZ.15 $1021.05 LizOZLO F6203.
Composition 3.5 MgO 6.0 M1102 8.5 ZnO 6.5 NiO 1.5 LizCOz 4.0 SiOz 70.0 FezOs uct are the following:
Initial permeability (l-3 megacycles) 115 Curie point C 270 Temperature coeflicient of (toroid) 10% change between room temperature and 120 4 Example 2 A mix is made of the following ingredients in the proportions indicated:
M01 ratio: .08 Mg0:0.19 MnO:.19 ZnO:.36
NiO:.05 Li2O:.14 8102:.92 Fezoa.
Composition 1.5 MgO 7.5 M1102 7.0 ZnO 12.5 M0
1.5 LizCOs 4.0 SiOz 68.0 F8203 The preparation and molding is done in the same way as mentioned in Example 1.
The properties of the fired material are these: Initial permeability (1-3 mos.) Maximum permeability (D. C.) 300 Curie point C 275 Temperature coefiicient of (toroid) 5% change between room temperature and C.
Example 3 A mix is made up of the following ingredients in the proportions indicated:
Mol ratio: .25 MgO:.14 MnO:.25 ZnO:.16 NiO:.20 81022.92 F6203.
Composition 5.0 MgO 6.0 MnOz 10.0 ZnO 6.0 N10 73.0 FezOa 6.0 S102 The preparation and molding is done in the same way as mentioned in Example 1.
The physical properties of this material are shown in the following table:
Initial permeability (1-3 mos.) 90 Curie point C 265 Temperature coeflicient of (toroid) 1-3% change between room temperature and 120 C.
I claim:
1. A ferromagnetic ceramic material consisting mainly of iron oxide compounds of the magnetitetype, suitable for the use at frequencies between 60 es. and about 30 mos, composed of the four bivalent metal oxides, MgO, MnO, ZnO, and NiO, silica and F6203, in the mol ratio of .05-.35 MgO .10-.25 MnO .15-.30 ZnO .15-.40 N10 .10-.20 S102 about 1 F6203 the total mol proportion of the bivalent metal oxides to F8203 being approximately 1:1 said material having'a Curie point of at least 250 C. an initial permeability between 50 and and a temperature coefficient of a (measured on a toroid) of less than 10% between room temperature and 120 C.
2. A shaped ferromagnetic ceramic article consisting mainly of iron oxide compounds of the magnetite type, composed of MgO, MnO, ZnO, NiO, F8203 the total mol proportion of the bivalent metal oxides being approximately equal to the mol proportion of F9203 and an amount of about .2 mol of silica (per mol proportion of F8203) said material forming a heterogeneous body of a crystalline cubic phase and a glassy intercrystalline phase, the material of said article having a Curie point of at least 250 C'. an initial permeability of about 50 to 150 and a temperature coefiicient of a (measured on a toroid) of less than 10% between room. temperature and 3. A ferromagnetic ceramic material consisting essentially of iron oxide compounds of the magnetite type, composed of about 1 mol proportion of MgO, MnO, ZnO and N10, 1 mol total proportion of F6203 and an amount of about .1.2 mol of silica and about 0.05 mol of an univalent metal oxide, per mol proportion of F8203, said material consisting of a heterogeneous body of a crystalline cubic phase and a glassy intercrystalline phase and 9, having a Curie point of at least 250 0., an initial permeability of about 50 to 150 and a temperature coefiicient of ,1 (measured on a toroid) of less than between room temperature and 100 C.
4. A ferromagnetic ceramic material consisting essentially of iron oxide compounds of the magnetite-type, composed of the four bivalent oxides, MgO, MnO, ZnO, and NiO, silica and F8203, in the mol ratio of 20-30 MgO .10-.15 MnO 20-.30 ZnO .15-.20 NiO .15-.20 S102 about 1.0 F6203, the total mol proportion of the bivalent metal oxides to F6203 being approximately 1:1 said material having a Curie point of at least 250 C. an initial permeability of 70-100 and a temperature coefficient of u (measured on a toroid) of less than 3% between room temperature and 120 C.
5. A process of makin a shaped ferromagnetic body consisting essentially of iron oxide compounds of the magnetite type, which body consists of a heterogeneous body having a crystalline cubic phase and a glassy intercrystalline phase comprising the steps of mixing together F6203 and compounds of Mg, Mn, Zn, and Ni adapted to appear in the final prdouct after firing as MgO, MnO, ZnO, NiO the mol proportion of the Fezos being approximately equal to the total mol proportion of the first four oxides, adding about 0.10 to 0.20 mol proportion of the finely divided SiOz based on the mols of Fe2o3 present,
moistem'ng and plasticizin the mix, molding the mix to the desired shape and firing the molded product at a temperature to produce a two phase system consisting of a cubic crystalline phase and a glassy intercrystalline phase.
6. A process of making a shaped ferromagnetic body consisting essentially of iron oxide compounds of the magnetite type, which body consists of a heterogeneous body having a crystalline cubic phase and a glassy intercrystalline phase comprising the steps of mixing together powdered MgO, MnOz, ZnO, N10, and F8203 the mol proportion of the F6203 being approximately equal to the total mol proportion of the first four oxides, adding about 0.10 to 0.20 mol proportion of finely divided 8102 based on the mols of F6203 present, and less than 0.05 mol proportion of L (on the same basis) moistening and plasticizing the mix, with a wax emulsion, molding the mix to the desired shape and firing the molded product at a temperature to produce a two phase system consisting of a cubic crystalline phase and a glassy intercrystalline phase.
ERNST ALBERS-SCHOENBERG.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 1,881,711 Lathrop Oct. 11, 1932 2,382,136 Crowley et a1 Aug. 14, 1945 2,452,531 Snoek Oct. 26, 1948 OTHER REFERENCES Snoek: New Development in Ferromagnetic Materials, (1944), Elsevier Publishing Co., Inc., New York, pp. 69-71.

Claims (1)

1. A FERROMAGNETIC CERAMIC MATERIAL CONSISTING MAINLY OF IRON OXIDE COMPOUNDS OF THE MAGNETITETYPE, SUITABLE FOR THE USE AT FREQUENCIES BETWEEN 60 CS. AND ABOUT 30 MCS., COMPOSED OF THE FOUR BIVALENT METAL OXIDES, MGO, MNO, ZNO, AND NIO, SILICA AND FE2O3, IN THE MOL RATIO OF.05-.35 MGO : .10-25 MNO : .15-.30 ZNO : .15-.40 NIKO : .10-20 SIO2 : ABOUT 1 FE2O3 THE TOTAL MOL PROPORTION OF THE BIVALENT METAL OXIDES TO FE2O3 BEING APPROXIMATELY 1:1 SAID MATERIAL HAVING A CURIE POINT OF AT LEAST 250* C. AN INITIAL PERMEABILITY BETWEEN 50 AND 150 AND A TEMPERATURE COEFFICIENT OF U (MEASURED ON A TOROID) OF LESS THAN 10% BETWEEN ROOM TEMPERATURE AND 120* C.
US95582A 1949-05-26 1949-05-26 Ceramic magnetic material with a small temperature coefficient Expired - Lifetime US2565111A (en)

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GB11666/50A GB668699A (en) 1949-05-26 1950-05-10 Ceramic magnetic material with a small temperature coefficient
FR1018562D FR1018562A (en) 1949-05-26 1950-05-24 Magnetic ceramic material
CH289183D CH289183A (en) 1949-05-26 1950-05-25 Ceramic, ferromagnetic body and process for its manufacture.
NL76660D NL76660C (en) 1949-05-26 1950-05-26

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Cited By (20)

* Cited by examiner, † Cited by third party
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US2670331A (en) * 1951-09-28 1954-02-23 Steatite Res Corp Magnesium-zinc ceramic ferrite containing copper
US2734034A (en) * 1956-02-07 Magnetic compositions
US2764552A (en) * 1952-02-22 1956-09-25 Int Standard Electric Corp Ferromagnetic materials
US2830162A (en) * 1954-06-22 1958-04-08 Raytheon Mfg Co Heating method and apparatus
US2846655A (en) * 1955-08-19 1958-08-05 Hughes Aircraft Co Impregnated ferrite
DE1064412B (en) * 1952-02-28 1959-08-27 Centre Nat Rech Scient Process for the production of an iron-manganese-magnesium-zinc ferrite
US2980617A (en) * 1956-03-13 1961-04-18 Indiana General Corp Ferrite compositions and method of making same
US2981903A (en) * 1954-02-26 1961-04-25 Bell Telephone Labor Inc Gyromagnetic wave transmission devices
US2981690A (en) * 1957-06-18 1961-04-25 Steatite Res Corp Ferrites with square hysteresis loops
US2992990A (en) * 1956-01-05 1961-07-18 Richard G Parker Soft magnetic material
US3007875A (en) * 1959-06-23 1961-11-07 Steatite Res Corp Square loop ferrites
US3023165A (en) * 1956-08-17 1962-02-27 Bell Telephone Labor Inc Magnesium ferrite containing aluminum and method of making same
US3033792A (en) * 1957-05-28 1962-05-08 Kikuchi Yoshimitsu Method of manufacturing ferrite magnetostriction vibrators
US3039964A (en) * 1957-05-06 1962-06-19 Du Pont Preparation of ilmenite-type compounds
US3039965A (en) * 1957-05-06 1962-06-19 Du Pont Ilmenite-type complex manganese oxides and preparation thereof
US3061546A (en) * 1960-03-02 1962-10-30 Rca Corp Magnetic cores
US3066233A (en) * 1957-07-25 1962-11-27 Clevite Corp Ferrite transducers
DE976406C (en) * 1951-10-30 1963-08-29 Steatite Res Corp Using a fired product as a ferromagnetic mass
US5346638A (en) * 1992-09-14 1994-09-13 Murata Manufacturing Co., Inc. Oxide magnetic material
US5523549A (en) * 1994-05-25 1996-06-04 Ceramic Powders, Inc. Ferrite compositions for use in a microwave oven

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DE1176544B (en) * 1957-09-18 1964-08-20 Hermsdorf Keramik Veb Process for the production of magnetically hard oxide materials
US3096288A (en) * 1957-12-23 1963-07-02 Union Carbide Corp Ferri-magnetic spinel bodies
US2934667A (en) * 1958-06-17 1960-04-26 Gen Electric Controlled resistivity glaze for ignitor plugs
NL273242A (en) * 1962-01-05

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US2382136A (en) * 1943-03-13 1945-08-14 Henry L Crowley & Company Inc Ceramic bodies and method of producing same
US2452531A (en) * 1943-05-31 1948-10-26 Hartford Nat Bank & Trust Co Process of manufacturing a magnetic material and magnetic core

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US1881711A (en) * 1931-08-14 1932-10-11 Bell Telephone Labor Inc Magnetic structure
US2382136A (en) * 1943-03-13 1945-08-14 Henry L Crowley & Company Inc Ceramic bodies and method of producing same
US2452531A (en) * 1943-05-31 1948-10-26 Hartford Nat Bank & Trust Co Process of manufacturing a magnetic material and magnetic core

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2734034A (en) * 1956-02-07 Magnetic compositions
US2670331A (en) * 1951-09-28 1954-02-23 Steatite Res Corp Magnesium-zinc ceramic ferrite containing copper
DE976406C (en) * 1951-10-30 1963-08-29 Steatite Res Corp Using a fired product as a ferromagnetic mass
US2764552A (en) * 1952-02-22 1956-09-25 Int Standard Electric Corp Ferromagnetic materials
DE1064412B (en) * 1952-02-28 1959-08-27 Centre Nat Rech Scient Process for the production of an iron-manganese-magnesium-zinc ferrite
US2981903A (en) * 1954-02-26 1961-04-25 Bell Telephone Labor Inc Gyromagnetic wave transmission devices
US2830162A (en) * 1954-06-22 1958-04-08 Raytheon Mfg Co Heating method and apparatus
US2846655A (en) * 1955-08-19 1958-08-05 Hughes Aircraft Co Impregnated ferrite
US2992990A (en) * 1956-01-05 1961-07-18 Richard G Parker Soft magnetic material
US2980617A (en) * 1956-03-13 1961-04-18 Indiana General Corp Ferrite compositions and method of making same
US3023165A (en) * 1956-08-17 1962-02-27 Bell Telephone Labor Inc Magnesium ferrite containing aluminum and method of making same
US3039964A (en) * 1957-05-06 1962-06-19 Du Pont Preparation of ilmenite-type compounds
US3039965A (en) * 1957-05-06 1962-06-19 Du Pont Ilmenite-type complex manganese oxides and preparation thereof
US3033792A (en) * 1957-05-28 1962-05-08 Kikuchi Yoshimitsu Method of manufacturing ferrite magnetostriction vibrators
US2981690A (en) * 1957-06-18 1961-04-25 Steatite Res Corp Ferrites with square hysteresis loops
US3066233A (en) * 1957-07-25 1962-11-27 Clevite Corp Ferrite transducers
US3007875A (en) * 1959-06-23 1961-11-07 Steatite Res Corp Square loop ferrites
US3061546A (en) * 1960-03-02 1962-10-30 Rca Corp Magnetic cores
US5346638A (en) * 1992-09-14 1994-09-13 Murata Manufacturing Co., Inc. Oxide magnetic material
US5523549A (en) * 1994-05-25 1996-06-04 Ceramic Powders, Inc. Ferrite compositions for use in a microwave oven
US5665819A (en) * 1994-05-25 1997-09-09 Ceramic Powders, Inc. Ferrite compositions for use in a microwave oven

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CH289183A (en) 1953-02-28
GB668699A (en) 1952-03-19
NL76660C (en) 1954-12-15
FR1018562A (en) 1953-01-09

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