Classifications

• • 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
  • C04B35/2633—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 barium, strontium or calcium
• • 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
  • C04B35/2616—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 lithium
• • 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
• • 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

• Certain ferromagnetic oxidic materials exhibit permanent properties and can be used at extremely high frequencies, i.e., -l5,00030,000 megacycles/sec. These materials, which are described in detail in US. Patent 2,762,777, have a crystal structure similar to that of the mineral magneto-plumbite, that is, they have a hexagonal structure with a c-axis of about 23.3 A. and an a-axis of about 5.9 A. The crystals of these materials exhibit a large magnetic crystal anisotropy in the direction of the hexagonal axis. Consequently, where use is made of the Faraday rotation or magnetic resonance, bodies constituted of these materials may be used for various microwave applications.
• ferromagnetic oxidic materials having a spinel crystal structure are also known. These materials are magnetically soft and hence have no in ternal field of consequence. These materials also exhibit Faraday rotation and magnetic resonance at frequencies (or wave-lengths) which depend upon the strength of an external field. As a practical matter, it is possible to realize external fields of such magnitude in micro-wave apparatus, e.g. a wave-guide, such that magnetic resonance occurs in those materials in a range from 3 to 15 crns. (2,000 to 10,000 mc./s.). Thus, a range of wave-lengths, e.g. 6 mms. to 3 cms., exists in which present materials cannot be used satisfactorily.
• Another object of our invention is to provide a method of making ferromagnetic oxidic materials useful at microwave frequencies.
• D is a tetravalent ion of at least one of the metals Ti, Ge, Zr, Hf and Sn
• Me is a bivalent ion of at least one of the metals Mn, Ni, Zn, Mg and Cu, and wherein are particularly suited for use at frequencies of 10,000 to 50,000 mc./s. (6 mms. to 3 ems).
• Bodies consisting of a ferromagnetic material according to the invention and more particularly those in which a certain texture is present may be used in transmission systems for microwaves.
• anisotropy field of these materials applications of magnetic resonance are possible in the range of from 6 to 30 mms. (10,000 to 50,000 mc./s.). This range is determined not only by anisotropy, but also by demagnetization.
• the lower limit of the wave-length may be further decreased by applying an external magnetic field, the wave-length then being determined by the anisotropy field, the demagnetization and the external magnetic field.
• the materials according to the invention are manufactured preferably by heating (sintering) a finely-divided and approximately correctly proportioned mixture of the component metal oxides of the new compounds. It is naturally possible for one or more of the component metal oxides to be replaced wholly or in part by compounds which can change to metal oxides upon heating, for example carbonates, oxalates and acetates. It is also possible for the component metal oxides to be substituted wholly or in part by one or more reaction products of two or more of the component metal oxides, for example BaFe O The term correct ratio is to be understood in this case to mean a ratio of the quantities of metals in the initial mixture equal to that in the materials to be manufactured. If desired, it is possible first to pre-sinter the finely divided initial mixture, to pulverize the reaction product and to sinter again the resultant powder. This series of treatments may, if desired, be repeated once or several times.
• the temperature of the sintering or final sintering process is chosen between about C. and about 1450" C., for example between 1200 C. and 1350 C.
• sintering agents such as silicates and fluorides.
• Bodies made of the above-described ferromagnetic 3 materials may be manufactured by sintering the initial mixture of the metal oxides or the like right from the start in the desired shape and also by pulverizing the reaction product of the pre-sintering process and, if desired after the addition of a binding agent, forming it into the desired shape, followed by after-sintering.
• Bodies which consist of the described ferromagnetic materials and which exhibit a certain texture may be obtained by directing the particles of the ferromagnetic material, each particle having a preferential direction of magnetization, which can freely move to a certain extent with respect to one another, in a magnetic field to orient the particles with their preferential directions parallel to the principal direction of magnetization and fixing them into a coherent assembly as described in US. Patent 2,762,778. It is also possible for the particles fixed into a coherent assembly to be sintered to form a compact body.
• the powder preferably consists as far as possible of monocrystalline particles.
• bodies consisting of the described ferromagnetic materials and exhibiting a certain texture to be manufactured by including in the initial mixture at least one ferromagnetic compound, of which a body may be manufactured by means of a directing process. If the particles of this material are present in a relatively oriented condition, they can be directed in a magnetic field while still being freely movable to a certain extent with respect to one another. Upon heating, the mixed crystals are formed which are also magnetically oriented.
• the powder preferably consists, as far as possible, of monocryst-alline particles as far as the said ferromagnetic compound is con cerned. This method affords the advantage that the directing process may be applied to particles having an anisotropy higher than that of the particles of which the ferromagnetic body to be manufactured is built up.
• EXAMPLE I A mixture consisting of BaFe O BaCO T10 and Coco in a ratio of 0.9 mol of BaFe O 0.1 mol 'of BaCO 0.6 mol of TiO- and 0.6 mol of CoCO which corresponds to the desired compound was ground with alcohol in a shaking mill for 8 hours.
• the ground product was suspended in acetone and a portion thereof was molded at a pressure of nearly 1 ton/ cm. into a tablet in a direct magnetic field, having a field strength of 1000 oersted parallel to the direction of molding. It is possible to apply a direction process to this mixture, since a body can be manufactured of the ferromagnetic compound BaFe O in which the particles are present in a relatively oriented condition.
• the tablet was heated from room temperature up to 500 C. within 16 hours and from 500 to 1210 C. within hours and subsequently sintered at 1210 C. in oxygen for 2 hours.
• the reaction may be represented by the equation:
• a small plate of 10 x 30 x 0.15 mm. was cut firom the tablet so that the side of 3 mms. was parallel to the direction of the magnetic field during the molding of the tablet.
• This plate was glued on a small trapezium-like quartz plate of 0.7 mm. thick. The whole was arranged in a rectangular wave guide of 7.1 x 3.55 mms. in parallel to the short side-wall having a height of 3.55 mms.
• Tablets were manufactured in a similar manner according to the reaction equation specified hereinafter, the tablets being sintered at the temperatures indicated in the table. The density, the specific resistance and the effective anisotropy field H of these tablets were determined. A small plate was cut from several of these tablets in the indicated manner and tested in the abovedescribed way. The values of the damping ratio d and of the applied magnetic field H are also specified in the table.
• a ferromagnetic body particularly adaptedfor use in microwave apparatus consisting essentially of a coherent mass of mixed crystals of compounds having a hexagonal crystal structure similar to that of the compound BaFe120l9, the composition of said mixed crystals corresponding to the formula in which I) is a quadrivalent metal ion selected from the group consisting of Ti, Ge, Zr, Hf, and Sn, Me is a bivalent metal ion selected from the group consisting of Mn, Ni++, Zn++, Mg, and Cu, and in which a, b, arid e are not more than 1, c is not more than 0.4, d is between 0.4 and 2.5, and f not more than 3, said crystals having a preferred direction of magnetization and being oriented in said preferred direction whereby said body is magnetically anisotropic and resonant at wavelengths of about 6 mms. to 1 cm.
• a ferromagnetic body particularly adapted for use in microwave apparatus consisting essentially of a coherent mass of mixed crystals of compounds having a hexagonal crystal structure similar to that of the compound BaFe O the composition of said mixed crystals. corresponding to the formula (labc) a b c d gflz) g;-2df) l9 in which D is a quadrivalent metal ion selected from the group consisting of Ti, Ge, Zr, Hf, and Sn, and in which a, b, and e are not more than 1, c is not more than 0.4, d is between 0.4 and 2.5, f not more than 3, said crystals having a preferred direction of magnetization and being oriented in said preferred direction whereby said body is magnetically anisotropic and resonant at wave-lengths of about 6 mms. to 1 cm.
• a ferromagnetic material consisting essentially of hexagonal crystals whose structure is similar to those of BaFe O and having a composition:
• D is a quadrivalent metal ion selected from the group consisting of Ti, Ge, Zr, Hf, and Sn
• Me is a bivalent metal ion selected from the group consisting of Mn++, Ni++, Zn++, Mg, and Cu, and in which a, b, and e are not more than 1, c is not more than 0.4, d is between 0.4 and 2.5, and f not more than 3.
• a ferromagnetic material consisting essentially of hexagonal crystals whose structure is similar to those of BaFe O and having a composition:
• D is a quadrivalent metal ion selected from the group consisting of Ti, Ge, Zr, Hf, and Sn, and in which a, b, and e are not more than 1, c is not more than 0.4, d is between 0.4 and 2.5 and f not more than 3.
• a ferromagnetic body particularly adapted for use in microwave apparatus consisting essentially of a coherent mass of hexagonal crystals whose structure is similar to those of BaFe m, ach of said crystals having a preferential direction of magnetization and .a composition:
• D is a quadrivalent metal ion selected from the group consisting of Ti, Ge, Zr, Hf, and Sn
• Me is a bivalent metal ion selected from the group consisting of Mn Ni, Zn, Mg++, and Cu++
• a, b, and e are not more than 1
• c is not more than 024
• d is between 0.4 and 2.5
• f not more than 3
• said body being magnetically anisotropic in a principal direction and resonant at wave-lengths of about 6 mms. to 1 cm., said crystals being oriented with their preferential directions of magnetization parallel to said principal direction.
• a ferromagnetic body particularly adapted for use in microwave apparatus consisting essentially of a coherent mass of hexagonal crystals whose structure is similar to those of BaFe each of said crystals having a preferential direction of magnetization and a composition:
• D is a quadrivalent metal ion selected from the group consisting of Ti, Ge, Zr, Hf, and Sn, and in which a, b, and e are not more than 0.4, d is between 0.4 and 2.5, and f not more than 3, said body being magnetically anisotropic in a principal direction and resonant at wave-lengths of about 6 mms. to 1 cm., said crystals being oriented with their preferential directions of magnetization parallel to said principal direction.
• a method of manufacturing a ferromagnetic material comprising the steps, forming a finely-divided mixture of a material having a composition:
• a and 19 being not more than 1, 0 being not more than 0.4, an om'de of a metal selected from the group consisting of Mn, Ni, Zn, Mg, and Cu, an oxide of a metal selected from the group consisting of Ti, Ge, Zr, Hf, and Sn, and cobalt oxide, all in correct proportions and yielding upon firing hexagonal crystals similar to those of said material and having a composition corresponding to the formula:
• D is a quadrivalent metal ion selected from the group consisting of Ti, Ge, Zr, Hf, and Sn
• Me is a bivalent metal ion selected from the group consisting of Mn++, Ni++, Zn++, Mg++, and Cu++
• a, b and 2 being not more than 1
• c being not more than 0.4
• d is between 0.4 and 2.5
• f not more than 3

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Citations (10)

• 1957
  • 1957-10-21 NL NL95813D patent/NL95813C/xx active
• 1958
  • 1958-10-17 GB GB33217/58A patent/GB862135A/en not_active Expired
  • 1958-10-18 CH CH6517258A patent/CH407352A/de unknown
  • 1958-10-18 DE DEN15744A patent/DE1095900B/de active Pending
  • 1958-10-18 DE DEN15743A patent/DE1087962B/de active Pending
  • 1958-10-20 US US768039A patent/US3046227A/en not_active Expired - Lifetime
  • 1958-10-20 BE BE572208D patent/BE572208A/xx unknown
  • 1958-10-20 FR FR1212959D patent/FR1212959A/fr not_active Expired

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