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
  • C04B35/2625—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
  • C04B35/2608—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
  • C04B35/2683—Other ferrites containing alkaline earth metals or lead

Definitions

• the ferromagnetic materials consist of crystals or mixed crystals of compounds having a chemical composition according to the formula where Me represents at least one of the bivalent metals from the series comprising Fe, Ni, Zn and Mg and where which compounds have a rhombohedral crystal structure the lementary cell of which can be described in the hexagonal crystal system by a c-axis of about 113.1 A. and an a-axis of about 5.9 A.
• a small part of ferric ions (Fe also can be replaced by trivalent chromium Cr and aluminum -(Al ions.
• These materials have valuable electrical and magnetic properties. For example, they exhibit a saturation magnetisation of the same order of magnitude as the ferromagnetic ferrites having the crystal structure of the mineral spinel, the so-called spinel structure. Like most of these ferrites, most of the materials in accordance with the invention have a high specific resistivity. Thus these materials can be fabricated into cores for use at high frequencies, in many cases at frequencies of 200 mc./ sec. and more, since the high specific resistivity gives rise to small losses.
• the initial permeability for many of these materials is constant up to much higher frequencies. Since the use of ferromagnetic cores in a frequency range in which the initial permeability is not constant generally involves the occurrence of high electro-magnetic losses, the novel materials can be used as ferromagnetic bodies up to the above-mentioned higher frequencies in all cases where low electro-magnetic losses are required.
• the crystal anisotropy is given as a first approximation by the expression (see R. Becker and W. Doring, Ferromagnetismus, 1939, page 114). If K is positive (so-called positive crystal anisotropy), the hexagonal axis of the crystal is the preferred direction of magnetisation. negative (which condition will hereafter be referred to as negative crystal anisotropy), this means that the spontaneous magnetisation is directed at right angles to the hexagonal axis and consequently parallel to the basal plane of the crystal. In the latter case, the crystal has a so-called preferred plane of magnetisation (there may, however, still be a comparatively weak preference of the magnetisation for certain directions in the basal plane).
• K is negative. In this event, in each crystal the direction of the spontaneous magnetisation lies in the basal plane and in this plane the direction of magnetisation is more read- If, however, K is 6 ily rotatable than in a direction which does not lie in this plane.
• the initial permeability has values which are high enough to be of interest for electromechanical use. This initial permeability is constant up to a far higher frequency than in ferromagnetic ferrites of spinel structure having an equal value of the initial permeability at low frequency.
• the materials in accordance with the invention having positive crystal anisotropy offer novel possibilities of manufacturing, for example, ferro-magnetic bodies having permanent magnetic properties and ferro-magnetic bodies for use in microwave-apparatus.
• a small amount, for example 25 mgs., of the crystal material to be examined is mixed as a fine powder with a few drops of a solution of an organic binder or adhesive 'in acetone, the mixture being spread on a glass slide.
• This slide is arranged between the poles of an electromagnet so that the lines of magnetic force are at right angles to the surface of the slide.
• the magnetic field strength is increased, so that the powder particles rotate in the field in a manner such that either the preferred direction of the magnetisation or the preferred plane of the magnetisation becomes substantially parallel to the direction of the lines of magnetic force.
• the crystal anisotropy constant K deepnds upon the chemical composition and also for each material, upon the temperature.
• a temperature can be determined below which the crystal anisotropy is negative and above which it is positive.
• the temperature of the reversing point of the crystal anisotropy depends mainly upon the content of bivalent cobalt.
• the reversal point lies at room temperature, if the material contains a certain amount of Co, which amount slightly depends upon the other small bivalent ions but is about /3 of the total amount of small bivalent ions. If more than about /3 of the small bivalent ions is Co (d greater than or about equal to 0.6), the crystals of the materials have a preferred plane of the magnetisation at room temperature.
• the crystals of the materials have a preferred direction of the magnetisation at room temperature.
• the choice of the material is determined by the fact Whether a positive or a negative crystal anisotropy is desired within the operating range.
• the value of the initial permeability can be further increased if in the formula 3 ferric-ions are partly replaced by trivalent Co-ions, but this is only possible to about 1.5 atomic percent expressed by 0.2g0.5. Comparatively high values of the initial permeability are also found in the materials containing Fe as the bivalent metal; however, these materials naturally have a low specific resistivity which involves the production of eddy-current losses at high frequencies.
• the production of the materials according to the invention is preferably eifected by heating (sintering) a finely powdered mixture of the component metal oxides of the novel compounds in about correct proportions.
• at least one of the component metal oxides can be wholly or partially replaced by compounds which can be converted into metal oxides by heating, for example carbonates, oxalates and acetates.
• the component metal oxides can also be wholly or partially replaced by one or more reaction products of at least two of the component metal oxides, for example BaFe O
• correct proportions as used herein is to be understood to mean proportions of the amounts of the metals in the initial mixture equal to those in the materials to be produced.
• the finely powdered initial material may be presintered, the reaction product being ground again and the powder thus obtained being re-sintered, and this sequence of operations may be repeated once or several times.
• This mehod of sintering is known per se, for example in the production of ferro-magnetic ferrites having spinel structure (see for example J. I. Went and E. W. Gorter, Philips Technical Review, 13, page 183, 1951-1952).
• the temperature of the sintering or final sintering process is between about 1000 C. and about 1450 0., preferably between 1200 C. and 1350 C.
• sintering agents for example silicates and fluorides
• Bodies consisting of the above-described ferromagnetic materials can be formed either by immediately sintering the initial mixture of the metal oxides or the like in the desired shape or by pulverizing the reaction product of the presintering process and shaping it, if required after the addition of a binder, into the desired form, after which it may be re-sintered or hardened.
• a material By sintering at a temperature materially exceeding 1200 C. and/or by sintering in a gas-atmosphere containing comparatively little oxygen, a material can be produced having a comparatively high proportion of Fe so that the specific resistivity can be reduced to values of less than ohm-cm. If this is not desired, because the material is to be used in magnetic cores for use at high frequencies without the production of excessive eddy-current losses at those frequencies, excessive formation of ferrous ions must be avoided or any excessive amount of ferrous ions must subsequently be oxidized to ferric ions in known manner, for example by heating again in oxygen at a temperature between 1000 C. and 1250 C.
• EXAMPLE I A mixture of BaCO CoCO and Fe O in proportions of 2 mols of BaCO 1 mol of CoCO and 9 mols of Fe O which corresponds to the desired compound Ba Co Fe O was mixed with ethyl-alcohol in a ball mill for half an hour. After drying, the mixture was pre-fired in air at 1000" C. for 15 hours, and the reaction product then ground together with ethyl alcohol in a ball mill for 1 hour. After drying, at small amount of a solution of an organic binder was added to the product and part of this mixture was compressed into a tablet which was fired in oxygen at 1260 C. for 1 hour.
• tablets were produced from mixtures comprising, in addition to BaCO and Fe O COCO3 and MgO, COCO3 and MgO, MgO, NiO and ZnO, respectively in a ratio of 2 mols of BaCO and 9 mols of Fe O to 0.5 mol of Coco and 0.5 mol of MgO, 0.25 mol of CoCO and 0.75 mol of MgO, 1 mol of MgO, 1 mol of NiO and 1 mol of ZnO, respectively, corresponding to the desired compounds Ba CoMgFe O a oe rs se sm 4 2 36 60, 4 2 36 60 and Ba Zn Fe O respectively.
• a third ring was fired in oxygen at 1270 C. for three hours, cooled at room temperature and subsequently heated again in oxygen at 1180 C. for 4 hours.
• the properties of this third ring are given in Table 2 under 3. Examination by means of X-rays showed that all the reaction products consist entirely of crystals having the desired structure.
• the measurements given in this and the following tables were obtained from rings in the demaguetised condition at room temperature according to the method described by C. M. van der Burgt, M. Gevers and H. P. J. Wijn in.
• a d g; 4 a 1 Z g' drying and the addition of a small amount of an organic 2 l gf, E 3 1 g t er rmg binder part of the product was compressed into a ring was E m an a e 0 room and fired in oxygen at 1260 C. for 1 hour.
• EXAMPLE V consisted entirely of crystals having the desired structure.
• a is at most 1
• b is at most 0.7
• c is at most 0.6
• d is at most 2
• e is at most 0.6
• f is at most 0.6
• g is at most 0.5
• said crystals having a rhombohedral structure, the elementary cell of'which can be described in the hexagonal crystal system by a c-axis of about 113.1 A., and an axis of about 5 .9 A.
• a ferromagnetic material consisting essentially of crystals having the composition:
• Me is at least one bivalent metal selected from the group consisting of Fe, Ni, Zn and Mg and in which Table 5 kc./s. 80 mc./s. 260 trials. 500 rnc.ls.
• 2 0.06 5. 3 0.15 narooigznmreat.tcofgom 6.0 6. 7 0. 03 6. 8 0.14 e. 4 0. 51 BmoofiM o.aremcofgow 5.
• EXAMPLE VI 0 is at most 1
• b is at most 0.7
• c is at most 0.6
• d is at The compounds oc 'oz tz m t].85 0.15 12 l9 and Ba Ca Fe O were produced by heating mixtures of BaCO Fe O and one of the compounds SrCO PbCO and CaCO respectively, in ratios corresponding to those compounds at 1-000 C. for 15 hours.
• rings were pressed from the products, which were fired at 1260 C. in oxygen for 1 hour with the exception of the ring containing lead, which is fired at 1240 C. in oxygen most 2, e is at most 06, f is at most 0.6, g is at most 0.5, said crystals having a rhombohedral structure, the elementary cell of which can be described in the hexagonal crystal system of a c-axis of about 113.1 A., and an a-axis of about 5.9 A., said crystals having at room temperature a preferred plane of magnetization.
• a ferromagnetic material consisting essentially of crystals having the composition:
• Me is at least one bivalent metal selected from the group consisting of Fe, Ni, Zn and Mg and in which a is at most 1, b is at most 0.7, c is at most 0.6, d is at least about 0.6 and at most 2, e is at most 0.6, f is at most 0.6, g is at least 0.2 and at most 0.5, said crystals having a rhombohedral structure, the elementary cell of which can be described in the hexagonal crystal system 12y eke-axis of about 113.1 A., and an a-axis of about 4.
• a ferromagnetic material consisting essentially of crystals having the composition:
• Table 6 10 kc.ls. 80 mc./s. 260 mc./s. 500 mc./s.
• a ferromagnetic material consisting essentially of crystals having the composition:
• Me is at least one bivalent metal selected from the group consisting of Fe, Ni, Zn and Mg and in which in which Me is at least one bivalent metal selected from the group consisting of Pe Ni, Zn and Mg and in which a is at most 1, b is at most 0.7, c is at most 0.6, d is at most 0.6, e is at most 0.6, f is at most 0.6, g is at most 0.5, said crystals having a rhombohedral structure, the elementary cell of which can be described in the hexagonal crystal system by a c-axis of about 113.1 A., and an a-axis of about 5.9 A., said crystals having at room temperature a preferred direction of magnetization.
• a ferromagnetic material consisting essentially of crystals having the composition:
• Me is at least one bivalent metal selected FOREIGN PATENTS from the group consisting of Pe Ni, Zn and Mg and in 78,889 Netherlands Aug 15' 1955 which a is at most 1, b is at most 0.7, c is at most 0.6, 661,721 Great Britain Nov. 28 1951 d is at most about 0.6, e is at most 0.6, f is at most 0.6, 751,623 Great England July 4, 1956 g is at most 0.5, said crystals having a rhombohedral 5 165,447 Australia Oct 4, 1955 structure, the elementary cell of which can be described in the hexagonal crystal system by a c-axis of about OTHER REFERENCES 113.1 A.
• FOREIGN PATENTS from the group consisting of Pe Ni, Zn and Mg and in 78,889 Netherlands Aug 15' 1955 which a is at most 1, b is at most 0.7, c is at most 0.6, 661,721 Great Britain Nov. 28 1951 d is at most about

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Ceramic Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Structural Engineering (AREA)
• Organic Chemistry (AREA)
• Compounds Of Iron (AREA)
• Magnetic Ceramics (AREA)
• Hard Magnetic Materials (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=19750803

Family Applications (1)

Country Status (8)

Citations (6)

• 1956
  • 1956-10-19 NL NL92523D patent/NL92523C/xx active
• 1957
  • 1957-10-14 US US689740A patent/US3020235A/en not_active Expired - Lifetime
  • 1957-10-15 DE DEN14197A patent/DE1174673B/de active Pending
  • 1957-10-16 GB GB32345/57A patent/GB824072A/en not_active Expired
  • 1957-10-16 FR FR1184419D patent/FR1184419A/fr not_active Expired
  • 1957-10-17 ES ES0238128A patent/ES238128A1/es not_active Expired
  • 1957-10-18 CH CH5172157A patent/CH387820A/de unknown
  • 1957-10-19 BE BE561767D patent/BE561767A/xx unknown

Patent Citations (6)

Also Published As

Similar Documents