US2893830A

US2893830A - Ferromagnetic material of the formula bafe3o5f and its preparation

Info

Publication number: US2893830A
Application number: US672883A
Authority: US
Inventors: Brixner Lothar Heinrich
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1957-07-19
Filing date: 1957-07-19
Publication date: 1959-07-07
Anticipated expiration: 1976-07-07

Description

United States Patent FERROMAGNETICMATERIAL OF THE FORMULA BaFe O F AND ITS PREPARATION Lothar' Heinrich Brixner, Wilmington, Del'., assignor to E. I. du' Pont de Nemours and Company, Wilmington, Deh, a corporation of Delaware No Drawing. Application July 19, 1957 Serial No. 672,883

5 Claims. (Cl. 23-50) This invention relates to a new ferromagnetic composition represented by the formula BaFe O F.

Ferromagnetic materials might broadly be classified into two groups: those with low coercivities, and those with high coercivities. Materials of the former type are useful in transformers, magnetic amplifiers, memory cores, and microwave devices, and include such well-known substances as the Permalloys, silicon irons, and certain ferritesthe ferrites being materials having the general formula MO-Fe' O- where M is a divalent metal. The ferromagnetic materials with high coercivities include the permanent magnetic materials, such as BaO-6Fe O and manganese bismuthide (MnBi). It follows, obviously, that ferromagnetic materials of high coercivity provide better permanent magnet characteristics than those with low coercivity. The ferromagnetic material described in this invention possesses an exceptionally high intrinsic coercive force, and it is represented by the chemical formula BaFe O F. It has a crystalline structure, but this structure is unlike that of such known ferromagnetic materials as the ferrites and BaO-6Fe O which is of the magneto plumbite type. X-ray analysis indicates that the composition contains none of the uncombined starting materials, and that it is different from the pattern of BaFeO F which might be considered to be an intermediate product in the preparation of my new crystalline material.

The ferromagnetic material of my invention may be prepared by starting with a mixture of BaCO BaF and Fe O in a molecular ratio of 1:1:1; i.e., in amounts required to form 2 mols BaFeO F with the evolution of 1 mol of CO This mixture is heated at a temperature of approximately 1000 C., and then cooled to room temperature and pulverized. The pulverized product is mixed with powdered Fe O in a stoichiometric quantity based on the formation of BaFe O P. This mixture is then fired and cooled. The resulting crystalline material is also pulverized, and then compacted into a unitary mass of desired shape by pressing or extruding. This mass is subjected to firing to produce the ferromagnetic material of this invention.

For a clearer understanding of the invention, the following specific example is given. This example is intended to be merely illustrative of the invention and not in limitation thereof. Unless otherwise specified all parts are by weight.

Example According to the equation BaCO +BaF +Fe O ZBaFeO F-l-CO stoichiometric amounts of reactants were ground together in an agate ball mill to a fineness of 200 mesh. These amounts by weight were 5.454 gms. of BaCO 4.8468 gms. of BaF and 4.4129 gms. of Fe O After thorough mixing, the powder was placed in a platinum crucible and heated in air at a temperature of approximately 1000 C. for 4 hours. The crucible was taken from the furnace, allowed to cool to room temperature, and the reaction 2,893,830 Patented July- 7, 1959 "ice was ground with 1 .9226 gms. ofthe fired material in an agate ball mill to a fineness: of -200 mesh. The mixture was then transferred toxa platinum crucible and was heated in air to a temperature of approximately 1200 C. and held. at this temperature for two hours. The crucible was removed from: the furnace, allowed to cool to room: temperature, and the contents pulverized to a -200 mesh by grindin'g. in the agate ball mill. The ground material was shaped intorapellet /2 inch in diameter at a pressure of 190,000 p.s.i. This pellet was subjected to an additional firing at approximately 1200 C. for one hour. The material. thus produced was a dark brown-black compactpellet which was useful as a mag.- net. When examined. by X-ray analysis, there was no indication of the uncombined components which were present prior to the last firing. The magnetic properties as determined with. a pressed cylindricalw specimen of density 3.96 gm./ cc. were as. follows:

B saturationma'gneti'zation (4rd,) 970 gauss.

The above values of the magnetic properties were obtained with a Sanford-Bennett high field permeameter from the Rubicon Company. A cylindrical sample /2" diameter and about 1% long) was butted between the pole pieces of the permeameter and subjected to the standard operating procedure for obtaining the demagnetizing curve.

Alternatively, other decomposable compounds like Fe(NO and Ba(NO might be used as alternative starting compounds. Commercially available products of the highest purity are preferred as starting materials. Although the example specifies firing temperatures of 1000 C. for the first firing and 1200 C. for the subsequent two firings, both of these temperatures may vary as much as C. without effecting any substantial change in the results obtained. Similarly, the times of heating which have been given in the example as four hours for the first heating, two hours for the second, and one hour for the third, may vary as much as, say, :1 hour for the first and second heating and 1 /2 hour for the third firings, the shorter times being used with the higher temperatures.

It will be seen from the above data on my novel magnetic crystalline material, particularly the values which were obtained for remanent magnetization and for intrinsic coercivity, that this material is valuable as a permanent magnet and would be useful in the many applications known for such a material. Among these would be rotating mechanical couplings, television focusing yokes, refrigerator and cabinet door latches, motors, and generators.

Since it is obvious that many changes and modifications can be made in the above-described details without departing from the spirit and scope of the invention, it is to be understood that the invention is not to be limited to said details except as set forth in the appended claims.

I claim:

1. As a composition of matter, a ferromagnetic material of the chemical formula BaFe O F.

2. As a composition of matter, a ferromagnetic material of the chemical formula BaFe O F, with an intrinsic coercivity of about 3700 oersteds, a remanent magnetization of about 750 gauss, a maximum energy product of about 135,790 gauss-oersteds and a specific resistance of about ohm-cm.

3. A process for producing a ferromagnetic material which comprises heating at a temperature of about 900 C.-1100 C. for about 3-5 hours a powdered mixture comprising (1) BaF (2) an inorganic iron compound selected from the group consisting of Fe O and Fe(NO and (3) an inorganic barium compound selected from the group consisting of BaCO and Ba(NO said barium and iron compounds being present in a molecular ratio of 1:1:1, cooling the product thus obtained, grinding the product to a powder, and incorporating with said powder, powdered Fe O in a stoichiometric amount according to the equation:

heating the latter mixture at a temperature of about 1100 C.1300 C. for about 1 hour-3 hours, cooling the product thus obtained, grinding the product to a powder, compacting the powder into a unitary mass and heating said mass at a temperature of about 1100 C.- 1300 C. for about V2 hour-1V2 hours to convert said latter mixture to ferromagnetic material of the formula BaFe O F and recovering said BaFe 'O F material.

4. A process for producing a ferromagnetic material which comprises heating at a temperature of about 900 C.-1100 C. for about 3-5 hours a powdered mixture comprising BaF R2 0 and BaCO said barium and iron compounds being present in a molecular ratio of 1:1:1, cooling the product thus obtained, grinding the product to a powder, and incorporating with said powder, powdered Fe O in a stoichiometric amount according to the equation:

heating the latter mixture at a temperature of about 1100 C.-1300 C. for about 1 hour3 hours, cooling the product thus obtained, grinding the product to a powder, compacting the powder into a unitary mass and heating said mass at a temperature of about 1100 C.1300 C. for about /2 hour-1V2 hours to convert said latter mixture to ferromagnetic material of the formula BaFe O F and recovering said BaFe O F material.

5. A process for producing a ferromagnetic material which comprises heating at a temperature of about 1000 C. for about 4 hours a powdered mixture comprising BaF Fe O and BaCO said barium and iron compounds being present in a molecular ratio of 1:1: 1, cooling the product thus obtained, grinding the product to a powder, and incorporating with said powder, powdered Fe O in a stoichiometric amount according to the equation:

heating the latter mixture at a temperature of about 1200 C. for about two hours, cooling the product thus obtained, grinding the product to a powder, compacting formula BaFe O F and recovering said BaFe O F ma terial.

No references cited.

Claims

1. AS A COMPOSITION OF MATTER, A FERROMAGNETIC MATERIAL OF THE CHEMICAL FORMULA BAFE3O5F.