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
  • C04B35/2616—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

Definitions

• the invention relates to a method of manufacturing magnet cores consisting of representatives of a'special class of lithium-, copper-, zinc-, (cobalt-) ferrites, by sintering at temperatures which do not exceed 1 100C. These cores may serve to replace, nickel-containing and hence more expensive, ferrite cores which may serve as yoke rings or as aerial rods.
• the temperature factor (TF) is the most reliable
• the invention relates to a method of manufacturing 5 tandard for the temperature dependence of the magmagnet cores consisting of a soft magnetic ferrite and to ferrite cores manufactured by this method.
• Magnet cores which consist of a soft-magnetic ferrite and which on the one hand satisfy three quality require ments to be defined in detail below and which on the other hand are distinguished by comparatively low manufacturing costs formed the object of the examination which has resulted in the present invention.
• the said quality requirements are:
• the initial permeability (m), measured at a temperature of 23 C and a frequency of 4 kHz, is higher than 150;
• the specific resistivity (p), measured at a temperature of 23 C, is higher than 10 ohm cm;
• the Curie temperature (T is higher than I30 C; the Curie temperature is to be understood to mean herein that value of the temperature at which the initial permeability, as a function of the temperature, after having reached its maximum value has fallen with increasing temperature to a value of 10 percent of the said maximum value.
• the magnet cores in question may not contain nickel and that they can be manufactured by means of a sintering process which requires no temperatures higher than i 100C and which can be carried out in air.
• magnet cores in which all the said requirements which mutually are more or less conflicting can be satisfied simultaneously.
• magnet cores consisting of manganese-zinc-ferro-ferrite are distinguished by a comparatively high initial permeability, they show a comparatively low specific resistivity, in the order of magnitude of 10 ohm.cm, while the sintering temperatures required for the manufacture of said magnet cores are rather high, namely from 1200 "C to 1350 C.
• the invention is particularly suitable for the preparation of so-called yoke rings" and aerial rods.
• Yoke rings are to be understood to mean magnet cores consisting of soft-magnetic ferrite and to be used at frequencies varying from 4 to 1000 kHz in deflection coils for television display tubes. Besides the abovementioned quality requirements b and c, said yoke rings must preferably also satisfy the requirement that the initial permeability should be higher than 300 (a, 300).
• Aerial rods to be used at frequencies higher than 1 MHz must satisfy, besides the above-mentioned quality requirements a, b and c, preferably also the following quality requirements:
• (m) is the value of the magnetic initial permeability of the magnet core in question at the temperature t while 1 is the value of the magnetic initial permeability at the reference temperature t,..
• room temperature (23 C) is chosen for the reference temperature t,.
• the magnet cores manufactured according to the invention consists of soft-magnetic ferrites built up from ferric oxide,Fe2O3, copper oxide, CuO, lithium oxide LizO, zinc oxide, ZrO, and, possibly, cobalt oxide, C00.
• This ferrite is a known material the composition of which in the technical literature is usually referred to by means of the formula LiZO-S Fe2O3(see, for example, Naturwissenschaften 26, p7 431 (i938) and Dutch Pat. specification No. 77,389) which formula is a different notation for the abovementioned formula: (Lima-LP e0 05 )O-Fe O
• the composition of this material in the technical literature is also sometimes referred to by the formula Li Fe 0., (see again the above-mentioned Dutch Pat. specification No. 77,389).
• a part of the iron oxide of the starting mixture thus takes part in the formation of the bivalent complex oxide (Li Fe )O which, like the other oxides CuO, ZnO and possibly C00, forms, with the rest of the iron oxide, a ferrite of the formula MCO'FC2BD3 (wherein Me is one of the above-mentioned bivalent metal oxides or the above-mentioned complex metal oxide).
• MCO'FC2BD3 wherein Me is one of the above-mentioned bivalent metal oxides or the above-mentioned complex metal oxide.
• Stoichiometric composition is to be understood to mean a composition in which the molecular percentage of the iron oxide is equal to the molecular percentage of the oxide MeO (with a single ferrite) and is equal to the sum of the molecular percentages of the oxides Me() (with a mixed ferrite), respectively, or, in other words, a composition with 50 mol.% Fe2 0 not counting iron which would cooperate in the formation of a complex bivalent oxide.
• a second advantage of the above-described manner of indicating the composition of the starting mixture is related to the condition that the ratio of the molecular percentages of the complex oxide (Li Fe )0 on the one hand and the ZnO on the other hand, in the starting mixtures has been found to be of importance in relation to the magnet cores manufactured from these starting mixtures either or not fulfilling the above-mentioned quality requirements.
• the magnetic quality properties of the resulting magnet cores also depend upon the ratio in the starting mixture.
• the method according to the invention is characterized in that a finely divided mixture of iron oxide, Fe O copper oxide, CuO, lithium oxide Li 0, Zinc oxide, ZnO, and, possibly, cobalt oxide, CoO, having a composition expressed in molecular percentages of the metal oxides, in which the lithium is deemed to be present exclusively as a component of a bivalent complex oxide having a composition according to the formula (Li Fe )O, and in which the iron which would be required for the formation of said complex bivalent oxide is not included in the notation of the quantity of iron, expressed in molecular percentages Fe O which mixture has a composition defined in this manner of:
• the mixture of the above-mentioned metal oxide is prefired at a temperature of at most approximately 950 C after which the prefired product is cooled, pulverized and compressed in the form of the magnet core to be manufactured, and the resulting compressed product is sintered again in air or in a mixture of air and oxygen at a temperature which does not exceed 1 100 C.
• one or more of the said oxides in the starting mixture may be replaced by another compound of the same metal, which compound can be converted into the corresponding metal oxide during the heating required for the sintering.
• Such compounds are, for example, carbonates, oxalates and acetates.
• the starting material preferably are mixtures having a composition, defined in the same manner, of
• a number of magnet cores were prepared as follows: Starting materials were iron oxide, Fe O copper carbonate CuCO zinc oxide, ZnO, lithium carbonate, Li (O and, possibly, cobalt carbonate, Co(O). The starting materials were mixed in the desired ratio. The mixture was ground in a ball mill using ethanol as a grinding liquid for 6 hours. The ground product was then filtered off, dried and prefired for one hour by heating it at a temperature of 850 C. As is known, such a prefiring is a rather universally used measure in manufacturing methods of the type in question. The prefired product was then ground for 16 hours in a ball mill using water as a grinding liquid. The ground product was then filtered off and dried.
• a binder was added which consisted of 2 percent solution of ammonium alginate in water.
• the resulting doughy mass was granulated by forcing it through the meshes of a sieve.
• From the granulate rings were compressed with a pressure of compression of 0.5 ton/cm?
• the rings were then sintered in air. For that purpose they were heated up to the peak temperature (sintering temperature) at a rate of approximately 150 C per hour.
• the rings were maintained at the peak temperature for approximately 15 minutes after which, again at a rate of approximately l50 C per hour, they were cooled to room temperature.
• the specific resistivity, p at a temperature of 23 the quotient of the loss factor and the initial permeability tgp/;t,, at a temperature of 23 C and a frequency of 1.5 MHz.
• the temperature factor, TF in the temperature range from 5 C to 55 C, with room temperature (23 C) as a reference point.
• compositions of the starting mixtures, the sinter ing temperatures (T used, and the measured quality values of the resulting magnet cores are recorded in the two following tables, (Tables A and B).
• Tables A and B the abovementioned ratio (Li Fe )O/ZnO is briefly denoted as Li /Zn".
• the following tables C and D relates to magnet cores in that the starting mixture has a composition of the manufacture of which the starting mixture was not 47.5 mOl 0f F6 0 prefired but was mixed with the binder after prolonged 35 5 15 mol% of CuO, grinding in a ball mill or a vibratory mill, and processes 0.7-2 mol Of COO, to a granulate, from which granulate rings were then remainder (Li0.5+Feo.5 )O a ,i Ii v rying compressed in the above-described manner, which from 0.25 l to l 1. rings were sintered in air, during which the peak tem- 4O 4.
• a method a claimed in claim 1, characterized in perature was again maintained for approximately l5 that at least one of the metal oxides composing the minutes. starting mixture is replaced by a compound of the same TABLE 0 metal, which is convertible into the corresponding M t l M 1 ercent Xmfi metal oxide during smterlng.
• a soft-magnetic ferrite core consisting essentially 42 0.5 40.0 1,083 500 170 330 43 0, 5 4g 5 1,083 550 160 340 of a sintered reaction product of 44 0.5 48.0 1,083 500 140 340 5 45 0. 5 47. 5 1 083 540 135 32 mol Of F6203 5 20 mol of CuO,
• a method of manufacturing a soft-magnetic ferrite (Li +Fe0,5 )O and 200 in a ratio varying from 0.25: core,characterized in thatafinely divided starting mix- I to 1.5 l, the iron required for the formation of ture of iron oxide, F8 0 copper oxide, CuO, lithium (Li -i- Fe f )0 not being included in the the quantity Oxide, Li O, zinc oxide, ZnO, and, Cobalt Oxide, COO, of iron, expressed in molecular percentages as Fe O having a composition expressed in molecular percentages of the metal oxides of 45.0- 52.55101 of F8103.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Ceramic Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Structural Engineering (AREA)
• Organic Chemistry (AREA)
• Soft Magnetic Materials (AREA)
• Magnetic Ceramics (AREA)
• Hard Magnetic Materials (AREA)
• Formation Of Various Coating Films On Cathode Ray Tubes And Lamps (AREA)
• Compounds Of Iron (AREA)

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Cited By (2)

Citations (8)

• 1970
  • 1970-06-26 NL NLAANVRAGE7009421,A patent/NL170678C/xx not_active IP Right Cessation
• 1971
  • 1971-06-22 CA CA116,260A patent/CA956453A/en not_active Expired
  • 1971-06-23 SE SE08196/71A patent/SE363690B/xx unknown
  • 1971-06-23 GB GB2942371A patent/GB1331685A/en not_active Expired
  • 1971-06-24 US US00156573A patent/US3709822A/en not_active Expired - Lifetime
  • 1971-06-24 ES ES392596A patent/ES392596A1/es not_active Expired
  • 1971-06-25 JP JP46045770A patent/JPS5231557B1/ja active Pending
  • 1971-06-28 FR FR7123461A patent/FR2099988A5/fr not_active Expired

Patent Citations (8)

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