US3846322A - Method of producing large single crystals of mixed ferrites - Google Patents

Method of producing large single crystals of mixed ferrites Download PDF

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US3846322A
US3846322A US00048848A US4884870A US3846322A US 3846322 A US3846322 A US 3846322A US 00048848 A US00048848 A US 00048848A US 4884870 A US4884870 A US 4884870A US 3846322 A US3846322 A US 3846322A
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ferrite
single crystal
oxygen
molten
mixed
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H Watanabe
M Sugimoto
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    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
    • 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
    • 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
    • C04B35/265—Compositions containing one or more ferrites of the group comprising manganese or zinc and one or more ferrites of the group comprising nickel, copper or cobalt
    • 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
    • C04B35/2658—Other ferrites containing manganese or zinc, e.g. Mn-Zn ferrites
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B13/00—Single-crystal growth by zone-melting; Refining by zone-melting
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/16—Oxides
    • C30B29/22—Complex oxides
    • C30B29/26—Complex oxides with formula BMe2O4, wherein B is Mg, Ni, Co, Al, Zn, or Cd and Me is Fe, Ga, Sc, Cr, Co, or Al

Definitions

  • the present invention relates to a method for produc- May 23, 1964 Japan 39-28833 ing a large Single crystal of a mixed ferrite containing May 23, 1964 Japan 39-28834 ZnO and having a Spine] Structure by melting the raw materials under an oxygen atmosphere with a pressure [52] US Cl. 252/62.62, 23/301 SP, 23/305 of from L to atmospheres at a temperature of [51] Int. Cl.
  • the present invention relates to a new and improved method of producing a large single crystal of a mixed ferrite with a spinel structure containing 2 30 mol percent zinc oxide and having the dimensions of at least about 20 mm in diameter and at least about 30 mm in length.
  • the method of this invention comprises melting the raw materials of ferrite at a temperature of from 1,600 to 1,800C in an oxygen atmosphere with a pressure of from 1.5 to 20 atmospheres and subsequently cooling the molten ferrite at the rate of from 2 to 8 C/hour in an oxygen atmosphere with a pressure of from 1.5 to 20 atmospheres to carry out the crystal growth using a furnace of the Bridgman type.
  • the mixture of oxides or compounds and the pulverized powder after sintering may be used for the raw materials;
  • the detailed explanation of the present invention is as follows:
  • ferric oxide accounts for a large portion of its components, that is, about 70 wt. percent.
  • FeO ferrous oxide
  • 1,300C which is the dissociation temperature of ferric oxide
  • the amount of ferrous oxide increases with increasing temperature.
  • 1,600C all kinds of ferrites having spinel structures are molten and contain a comparatively large amount of ferrous oxide. A small amount of ferrous oxide formed in the molten ferrite can be dissolved into the spinel structure during the cooling step and does not prevent the crystal growth.
  • the difference of the equilibrium oxygen pressure depends on the fact that a ferrite is either solid or liquid, based on the binary system Fe O Fe O after Darken and Gury (Journal American Chemical Society, 68, 798 816 (1946)), as shown in FIG. 1.
  • the equilibrium oxygen pressure must follow a line a in the solid phase, a line b in the solid plus liquid phases and a line c in the liquid phase. Therefore, the equilibrium atmosphere after Blank in the solid phase (the line a in FIG. 2) can not be extrapolated to the liquid phase (a line a in FIG. 2).
  • FIG. 1 shows the binary system Fe O.,Fe O after Darken and Gury
  • FIG. 2 shows the controlling method of the oxygen pressure of atmosphere according to the present invention
  • FIG. 3 is a schematic representation of the structure of an induction furnace of the Bridgman type for growing single crystals according to the present invention
  • FIG. 4 shows the amount of ferrous ion formed when Mn-Zn ferrite (mol ratio: 30 MnO/20 ZnO/SO Fe Og) is molten at 1,650C in an oxygen atmosphere at various pressures;
  • FIG. 5 shows the evaporation loss of zinc when MnZn ferrite is molten at 1,630C in an atmosphere of oxygen at various pressures
  • FIG. 6 shows the experimental result on the optimum melting temperature for MnZn and NiZn ferrites when raw materials were molten in an oxygen atmosphere with a pressure of from 1.5 to 20 atms'
  • FIG. 7 shows a sample cut in the form of a plate along a preferred direction of magnetization from a single crystal
  • FIG. 8 shows the rectangular hysteresis characteristics
  • FIG. 9 shows the inside temperature gradient of the induction furnace in FIG. 1 (the Bridgman type);
  • FIG. 10 shows the oxidation rate of Fe Fe in Mn-Zn ferrite at 1,300C in air as measured from the increase by weight
  • FIG. 11 shows the magnetic characteristics of a memory core cut from a single crystal of MnZn ferrite.
  • FIG. 12 shows the electric properties of a memory core cut from a single crystal of MnZn ferrite.
  • l is a induction coil
  • 2 is a support for the induction coil
  • 3 is a suscepter made of Pt-Rh alloy (containing percent Rh) with a cylindrical hollow shape (40 mm in diameter, 420 mm in length and 2 mm in thickness) and with a thickness such that the highfrequency induction current (420 K.C.) is perfectly shielded and the molten ferrite is not agitated by the leakage current
  • 4 is a crucible made of Pt-Rh alloy (20 mm diameter X 50 mm). On growing the crystal, the induction coil is slowly pulled upward with a gear 5 while the crucible is rotated once per minute.
  • 6 is a thermocouple and 7 is a autoclave vessel made of steel.
  • the amount of ferrous ion formed decreases as the oxygen pressure of the atmosphere increases. From an observation of microscopic structure, it was confirmed that the secondary phase (Wustite phase) appeared when the formation of ferrous ion became 7 wt. percent or more. Therefore, the crystal growth of a mixed ferrite should be carried out in an oxygen atmosphere of more than 1.5 atms. In the case of CuZn ferrite, the reduction of CuO-- Cu O can easily take place at a lower temperature, that is, the reduction progresses at about 1,050C or more in air. Then, an atmosphere of sufficiently high oxygen pressure is required for producing a single crystal of CuZn ferrite.
  • the second problem for producing a large single crystal of a mixed ferrite is the evaporation of zinc. It has been well known that the vapour pressure of zinc oxide is very large and zinc oxide in a mixed ferrite has the tendency of vaporizing as zinc at a higher temperature. Zinc content influences markedly the magnetic and electric properties of the produced single crystals. However, the evaporation of zinc in a mixed ferrite at a temperature higher than 1,600C has not heretofore been investigated.
  • FIG. 5 shows the amount of evaporation of zinc when Mn-Zn ferrite is kept at 1,630C for IS minutes.
  • the percent evaporation of zinc shows a remarkable decrease.
  • the present inventors have investigated the minimum oxygen pressure necessary for producing a large single crystal of a mixed ferrite having good magnetic and electric properties, and found, as the result that a large crystal could well be produced by melting the raw materials of ferrite and subsequently cooling the molten ferrite, even at such a low oxygen pressure as 1.5
  • zinc content is limited as follows:
  • the amount of zinc contained in a mixed ferrite of the present invention should be in the range of from 2 to 30 mol percent.
  • FIG. 6 shows the experimental result on the optimum melting temperature for MnZn and Ni-Zn ferrites when raw materials were molten in an oxygen atmosphere with a pressure of from 1.5 to 20 atms.
  • the zero point on the horizontal axis indicates the composition of MnFe O or NiFe O (containing no ZnO).
  • the optimum melting temperature was limited to the range of from l,600 to about I,730C and the melting temperature rose as the content of ZnO increases. And also, it was found that this temperature range can be applied to the case of CuZn ferrite. Furthermore, it is found that the melting temperature rises about 5C for the increase of one atmospheric oxygen pressure.
  • raw materials of MnZn ferrite were molten at a temperature lower than l,600C, an aggregation of small crystals was produced. Therefore, raw materials of MnZn ferrite should be molten at a temperature higher than 1,600C to obtain a large single crystal of a mixed ferrite.
  • the optimum melting temperature is from about 1,700 to about l,800C and the temperature falls as the content of ZnO increases.
  • the consumption of Pt or Rh of the crucible and the evaporation of zinc are remarkable at a temperature higher than 1,800C, it is desirable to melt raw materials of a ferrite at a temperature lower than 1,800C.
  • the fourth important problem for producing a large single crystal of a mixed ferrite is the rate of cooling the molten ferrite for growing the crystals.
  • the molten ferrite was cooled very quickly, that is, at a rate of more than 8C/hour, many cracks were formed in the produced crystal by the thermal shock of such quick cooling, and an aggregation of small crystals was produced.
  • the rapid cooling of the molten ferrite is not satisfactory for the growth of a large single crystal.
  • the raw materials should be molten under an oxygen atmosphere with a pressure of from l.5 to 20 atms., and the molten ferrite should be cooled at the rate of from 2 to 8C/hour in an oxygen atmosphere with a pressure of from 1.5 to 20 atms.
  • the just grown single crystal should be cooled very slowly to room temperature in equilibrium with the oxygen pressure of the atmosphere so that it has no net gain or loss of oxygen and no modification of the crystal structure.
  • the influence of the oxygen pressure on the grown single crystal during cooling to room temperature was negligibly small, because many parts of the crystal are closely covered with the crucible made of PtRh alloy, except for the upper.
  • the mixed ferrite produced by the method of the present invention includes, of course, mixed ferrites having a little deviation from the strictly stoichiometric composition.
  • a single crystal of a mixed ferrite produced by the method of the present invention has the advantage that the magnetic and electric properties can be provided as desired by proper selection of the kind and composition of ferrite.
  • a single crystal of a mixed ferrite containing zinc oxide of the present invention has properties superior to those of a single crystal of a conventional single ferrite or polycrystal ferrite. Therefore, the mixed ferrite is quite useful as a core material in electronic application.
  • its hysteresis loop is rectangular, the core of a single crystal cut from a large crystal can be used as a memory core of a computer. Many memory cores with the same properties can be produced from a parent large single crystal at the same time.
  • the preferred direction of magnetization of spinel-type ferrites containing no Co is in the direction of (111) which it is in the direction of 100) in the case of Co ferrite or spinel-type ferrites containing Co as one component.
  • the plate should be cut off along the preferred direction of magnetization (111) for a ferrite containing no Co and along the direction of for a ferrite containing Co as shown in FIG. 7. Then, a ferrite core with a ring shape'or a diamond shape is cut from the plate shape specimen by an appropriate method (for example, the supersonic technique, the etching method, etc.)
  • a memory core of a single crystal of a mixed ferrite obtained by the method of the present invention containing the preferred direction of magnetization has the following excellent characteristics, compared with a ferrite core of a polycrystal specimen prepared by a conventional sintering method.
  • a single crystal core of the mixed ferrite prepared by the method of the present invention has an ideal rectangular hysteresis characteristic, compared with a ferrite core of a polycrystal prepared by a conventional sintering method.
  • the rectangular hysteresis characteristics are represented, as shown in FIG. 8, in terms of the ratio of the residual flux density (Br) to the saturation flux density (Bm), i.e., Br/Bm.
  • the ratio of the flux density B at the magnetic field Hm/2 which is slightly smaller than the coercive 'force (I-lc) to the maximum flux density Bm at the magnetic field Hm, i.e., B /l3m, is often used;
  • the abovementioned ratio is about 0.93 0.95 and it is difficult to produce a ferrite core having a ratio more than 0.95.
  • a ratio of about 0.98 is easily attained.
  • the switching time is short and the driving power is small.
  • the kind and the composition of the ferrite should be strictly limited to a composition of MnMg ferrite. Therefore, it is difficult to change the switching time and the driving current in a wide range.
  • the rectangular hysteresis characteristic becomes more ideal.
  • various switching times and driving powers are attained by changing the kind and the composition of the ferrite employed. For example, when a large amount of Zn ferrite is dissolved, it is possible to make the He and the driving power smaller.
  • a switching time of less than 0.4 11. second was attained as shown in FIG. 12.
  • the rectangular hysteresis characteristic tends to be lost appreciably.
  • a single crystal core of a mixed ferrite of the present invention even if a large amount of Zn ferrite is dissolved, the rectangular hysteresis characteristic is not reduced at all, and a ferrite core having an excellent rectangular hysteresis characteristic and quite small driving power, which can not be attained by a conventional method, can be produced.
  • a ferrite core which has been cut from a single crystal of a conventionally known single ferrite, such as Cu, Mn, Ni or Zn ferrite in the preferred direction of magnetization is not so'desirable.
  • a ferrite core prepared from a single crystal of a conventional single ferrite has the rectangular hysteresis characteristic, but it is difficult to make the driving power and the switching time as small as in the case of a core of a single crystal of a mixed ferrite prepared by the method of the present invention.
  • a plurality of single crystal cores of the mixed ferrite prepared by the method of the present invention have such characteristics that each specimen is uniform in its size and the magnetic and the electric properties since each is cut mechanically from the same large single crystal. It has been a very difficult problem from the commercial point of view in the case of a core of polycrystal prepared by a conventionally known sintering method.
  • the single crystal of the present invention has such characteristics that for example, about 50,000
  • pieces of ferrite cores having the same properties and the size of 50 mils can be obtained from a single crystal of the ferrite having a diameter of about 30 mm and a length of 50 mm.
  • composition of the ferrites is given in terms of mol ratio of oxides.
  • EXAMPLE 2 About 35 grams of ferrite (composition: NiO/25 ZnO/50 Fe O was put in platinum-rhodium crucible 4 in FIG. 3, heated at 1,680C (in an oxygen pressure of 3.5 atms.) and made molten. Thereafter, it was cooled slowly to 1,5 50C at the rate of 8C/hour. As the result, a large single crystal of 20 X 35 mm was obtained, i.e., 20 mm diameter X 35 mm length.
  • EXAMPLE 3 A single crystal of MnZn ferrite of the invention containing about 7 wt. percentof Fe was divided into 4 pieces as shown in FIG. 10, and heated at 1,300C in an atmosphere of air for about 20 hours.
  • FIG. 10 shows the oxidation rate of Fe in Mn-Zn ferrite at 1,300C in air, as measured from increase of the weight. As is clear from the Figure, most of the Fe could be reoxidized by such heating for about 20 hours even at such a low temperature. Before reheating, the Laue photograph of the specimen containing Fe showed a spinel phase but the spots were big and obscure. However, after reheating, the spots were very sharp.
  • Electrolytic iron, electrolytic manganese and electrolytic zinc were weighted to form a composition of MnO/20 Zno/50 Fe O and then dissolved in nitric acid.
  • the single crystals contained about 5 wt. percent of Fe.
  • the preferred direction of magnetization (111) was determined by the X-ray Laue method, and plateshaped specimens having a thickness of 0.6 mm were cut by a precision diamond cutter including the direction of (111). Ring and diamond-shaped cores of single crystals having about 5 mm outer diameter were cut from the plate-shaped specimens by employing a supersonic cutting machine. According to this experiment, 5 pieces of ferrite core of single crystals were obtained from the crystal at the same time. These cores had characteristics very similar to one another.
  • the magnetic properties were as follows:
  • a method for producing a large single crystal of a mixed ferrite which is a member selected from the group consisting of manganese-zinc ferrite and nickel zinc ferrite with a spinel structure, containing zinc oxide in the amount of between 2 and 30 mole per cent, which comprises melting raw materials for the ferrite in a heating zone at a temperature above l,600 to 1,800C in an atmosphere consisting essentially of oxygen having a partial pressure of oxygen of from 1.5 to 20 atmospheres to reduce the content of ferrous ion in the molten ferrite to less than 7 wt.

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US00048848A 1964-05-23 1970-06-11 Method of producing large single crystals of mixed ferrites Expired - Lifetime US3846322A (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4057458A (en) * 1974-09-17 1977-11-08 Hitachi, Ltd. Method of making nickel zinc ferrite by liquid-phase epitaxial growth
DE3012180A1 (de) * 1979-03-28 1980-10-09 Fuji Electrochemical Co Ltd Verfahren zum erzeugen von ferrit- einkristallen
EP0018111A1 (en) * 1979-04-02 1980-10-29 Hitachi, Ltd. Method of producing ferrite single crystals
EP0106547A3 (en) * 1982-09-18 1986-01-22 Sony Corporation A method of manufacturing an oxide single crystal
US20080236706A1 (en) * 2007-03-30 2008-10-02 Tdk Corporation Method of producing mnzn-base ferrite

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2692978A (en) * 1951-10-05 1954-10-26 Bell Telephone Labor Inc Ferrite inductor
US3027327A (en) * 1957-10-08 1962-03-27 Gen Electric Preparation of ferromagnetic ferrite materials
US3115469A (en) * 1959-06-22 1963-12-24 Monsanto Chemicals Production of single crystals of ferrites
US3150925A (en) * 1961-04-20 1964-09-29 Richard J Gambino Method of growing single crystals

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2692978A (en) * 1951-10-05 1954-10-26 Bell Telephone Labor Inc Ferrite inductor
US3027327A (en) * 1957-10-08 1962-03-27 Gen Electric Preparation of ferromagnetic ferrite materials
US3115469A (en) * 1959-06-22 1963-12-24 Monsanto Chemicals Production of single crystals of ferrites
US3150925A (en) * 1961-04-20 1964-09-29 Richard J Gambino Method of growing single crystals

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Popova The Preparation of Single Crystals of Ferrites by the Vernevil Method, Soviets Physics Doklady Vol. 3, No. 4, 1958, pages 711 712. *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4057458A (en) * 1974-09-17 1977-11-08 Hitachi, Ltd. Method of making nickel zinc ferrite by liquid-phase epitaxial growth
DE3012180A1 (de) * 1979-03-28 1980-10-09 Fuji Electrochemical Co Ltd Verfahren zum erzeugen von ferrit- einkristallen
US4382839A (en) * 1979-03-28 1983-05-10 Fuji Electrochemical Co., Ltd. Process for producing ferrite single crystals
EP0018111A1 (en) * 1979-04-02 1980-10-29 Hitachi, Ltd. Method of producing ferrite single crystals
EP0106547A3 (en) * 1982-09-18 1986-01-22 Sony Corporation A method of manufacturing an oxide single crystal
US20080236706A1 (en) * 2007-03-30 2008-10-02 Tdk Corporation Method of producing mnzn-base ferrite
US7713465B2 (en) * 2007-03-30 2010-05-11 Tdk Corporation Method of producing MnZn-base ferrite

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GB1073034A (en) 1967-06-21
NL6506497A (enrdf_load_stackoverflow) 1965-07-26
DE1646932B1 (de) 1972-01-20

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