EP0278342B1 - Use of a material as a hard magnetic material - Google Patents

Use of a material as a hard magnetic material Download PDF

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EP0278342B1
EP0278342B1 EP88101333A EP88101333A EP0278342B1 EP 0278342 B1 EP0278342 B1 EP 0278342B1 EP 88101333 A EP88101333 A EP 88101333A EP 88101333 A EP88101333 A EP 88101333A EP 0278342 B1 EP0278342 B1 EP 0278342B1
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proportion
atom
use according
component
phase
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Alfred Dr. Müller
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Siemens AG
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/047—Alloys characterised by their composition
    • H01F1/053—Alloys characterised by their composition containing rare earth metals
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5

Definitions

  • the invention relates to the use of an iron-containing, magnetic material with at least three alloy components R, iron (Fe) and M, the material component of the Fe component being at least 60 atomic% and formed in the material a tetragonal ThMn12 structure is, as a hard magnetic material.
  • a material with such a structure is e.g. in the publication "Journal of Applied Physics", Vol. 52, No. 3, March 1981, pages 2077 and 2078.
  • the well-known hard magnetic ternary material neodymium (Nd) iron (Fe) boron (B) with a high energy product and relatively low Curie temperature at 300 ° C consists essentially of the tetragonal phase Nd2F14B or Nd 11.8 Fe 82.3 B 5.9 (see, for example, "J.Appl.Phys.”, Vol. 55, No. 6, Pt. 2, March 1984, pages 2083 to 2087). Of the 68 atoms in the unit cell (P42 / mm), the majority of Fe atoms form two layers with a structure similar to the sigma type.
  • R is yttrium (Y) and M is manganese (Mn).
  • M manganese
  • This three-substance system forms, inter alia, with its stoichiometric composition Y (Mn 1-x Fe x ) 12 an anisotropic, tetragonal ThMn12 structure which is antiferromagnetic.
  • Corresponding structures have intermetallic phases with 26 atoms in the unit cell (space group I4 / mmm).
  • this structure is schematically illustrated for the known binary compound MoBe12 (cf. K.Schubert: "crystal structures of two-component phases", Springer-Verlag, 1964, pages 166 and 167).
  • MoBe12 binary compound
  • the filled solid circles represent the individual lattice points occupied by Mo, while the hollow circles show the position of the loading lattice points.
  • the material thus has a high proportion of inexpensive Fe, which has a high magnetic moment, without a metalloid such as e.g. B, Si or Ge would be required.
  • the invention is based on the knowledge that the at least ternary alloys of the composition R-Fe-Mo or R-Fe-W have magnetic properties with Curie temperatures in the range of e.g. approximately 100 ° C to 200 ° C and saturation magnetizations in the range of e.g. have about 0.6 to 1.0 Tesla. With the stated percentages of the individual alloy components, it is ensured that the ThMn 12 phase which is favorable with regard to the magnetic properties is at least to a considerable extent included in the material.
  • Magnetic anisotropy also occurs with some alloy components from the group of rare earth metals, in particular with gadolinium (Gd) or samarium (Sm).
  • Gd gadolinium
  • Sm samarium
  • the Curie temperature or the saturation magnetization can optionally be increased by adding further components to the ternary system mentioned, in particular by adding cobalt (Co).
  • the material does not only have to consist of inevitable impurities from the phase with the tetragonal ThMn12 structure; rather, other phases of the alloy components mentioned can also be contained in it.
  • the material can advantageously be embedded in or attached to another material, so that it e.g. forms part of a mixed or composite material.
  • FIG. 2 graphically shows part of an isothermal section in the three-component system Fe-Mo-Nd.
  • Figure 3 shows temperature-dependent magnetization curves for special Fe80Mo12R8 alloys, while Figures 4 and 5 show the Curie temperature and saturation magnetization for these phases in comparison to the known materials Fe14R2B.
  • R means any rare earth metal, but in particular the elements cerium (Ce), neodymium (Nd), samarium (Sm), gadolinium (Gd), dysprosium (Dy) and erbium (Er). Combinations of several rare earth metals can optionally be selected for R.
  • the material of the composition R-Fe-Mo Fe and Mo with a respective content of 99.97% and the individual rare earth metals R of 99.9% with a maximum of 1000 ppm of rare earth oxides are assumed.
  • the rare earth metals are sawn into parts of suitable size immediately before processing and the surfaces are cleaned by wet grinding and ultrasound treatment in water and then in ethanol.
  • the alloy components are then melted together under argon as protective gas on a water-cooled copper ship by means of the heat generated by a high-frequency generator, with the Fe and Mo first being liquefied and then the respective rare earth metal being added.
  • the resulting ternary alloys are usually liquefied at least 5 times for complete mixing with high-frequency energy on the copper and rapidly cooled.
  • samarium alloys In the case of samarium alloys, on the other hand, one only has to remelt in an aluminum oxide crucible. In order to homogenize the ternary alloys, finally annealing is carried out at about 1050 to 1200 ° C, ie about 150 ° below the respective melting temperature, for about 1 hour.
  • annealing is carried out at about 1050 to 1200 ° C, ie about 150 ° below the respective melting temperature, for about 1 hour.
  • the individual bodies made of the alloys are under argon as a protective gas on an aluminum oxide base in a closed niobium hollow cylinder which is heated inductively.
  • the individual alloys are initially still multi-phase.
  • the rhombohedral Th2Zn17 phase can also be observed in this case in addition to other phases.
  • the alloys are practically only in one phase, with residues of oxide and other phases with a total of a maximum of 3% by volume being observed.
  • the individual phases of these alloys can be identified by metallographic and X-ray analysis.
  • FIG. 2 shows the corresponding concentration ratios for the three-component system Fe-Mo-Nd in an isothermal cut for about 1200 ° C. in a generally common graphical representation. This is based on a three-sided surface, the corner points of which are determined by the 3 alloy components Fe, Mo, Nd (each with a concentration of 100% there). The sides of the concentration triangle then reflect the compositions of the binary systems MoFe, FeNd and NdMo. The triangular surface is covered with a grid of parallels to the 3 sides, with neighboring parallels being spaced 2 atom% each. In the figure, only the Fe corner of the three-component system that is of interest here is detailed.
  • the ternary field, to which the phase Nd8Fe80Mo12 with ThMn12 structure belongs is separated from the area starting from Nd2Fe17 with Th2Zn17 structure by a two-phase field.
  • the individual crystal structures can be determined, for example, by examining corresponding powders with the aid of known X-ray diffractometers.
  • the magnetic material should have a significant proportion of the phase with the ThMn12 structure.
  • the proportions of the individual alloy components in the material are fixed from the outset. In general, a proportion between 60 and 85 atom% is chosen for the Fe component, a proportion between 2 and 20 atom% for the R component and a proportion between 4 and 35 atom% for the M component.
  • a pentagonal partial area is selected from the area of the corresponding concentration triangle, which is defined by the following 5 points P1 to P5:
  • the Curie temperatures T c listed in the table above are compared in FIG. 4 in a diagram with the Curie temperatures of known ternary alloys of the Fe14R2B type with the same rare earth components R. These known alloys are taken from the reference "Proc. 8th International Workshop on Rare Earth Magnets", Dayton, Ohio (USA), 1985, pages 423 to 440.
  • the course of the individual values with the atomic number of the rare earth metals R corresponds to that of the known series Fe14R2B.
  • the highest Curie temperature is found in the gadolinium, the highest saturation magnetization in the neodymium phase.
  • Fe80Mo12Sm8 and Fe80Mo12Gd8 have magnetic anisotropy, which is particularly pronounced in the samarium phase.
  • the M component of the material R-Fe-M is the element Mo.
  • this metal from the chromium group is at least partially replaced by the metal tungsten (W).
  • a ternary alloy was chosen as the exemplary embodiment.
  • the material can also contain a small proportion of at most about 10 atom% of at least one further alloy component.
  • cobalt (Co) up to a maximum of 8 atom% can advantageously be alloyed to the Nd and Sm alloys in order to increase the Curie temperature and / or the saturation magnetization.
  • the Co portion replaces a corresponding portion of the Fe component.
  • the resulting quaternary alloy Nd8Fe74Co8Mo10 has e.g. 100 ° C higher Curie temperature and 0.3 T higher saturation magnetization than the ternary alloy Nd8Fe82Mo10 without Co.
  • the ternary phases with Sm and the quaternary phases with Sm and Co are of particular interest as starting materials for hard magnetic materials.
  • Anisotropy field strengths of up to approx. 90 kOe can be achieved.
  • the material with 3 or more alloy components can not only be used in pure form. Rather, it can advantageously also be part of a mixed or composite material.
  • storage in or addition to inorganic substances such as glasses or ceramics, for example Al2O3, SiC or B, and also in or on organic materials is possible.

Abstract

The new magnetic material containing iron contains at least three alloy components R, iron (Fe) and M, a tetragonal ThMn12 structure being formed. The material proportion of the Fe component is intended to be at least 60% by atomic weight. According to the invention, it is provided that at least one rare-earth metal is selected for R, and molybdenum (Mo) and/or tungsten (W) are selected for M, the Fe proportion being at most 85% by atomic weight and the R and M proportion being between 2 and 20% by atomic weight and 4 and 35% by atomic weight, respectively. As well as the phase with the ThMn12 structure, the material can have at least one further phase of the R-Fe-M system. In particular, it can also be a component of mixed or composite materials. <IMAGE>

Description

Die Erfindung bezieht sich auf die Verwendung eines eisenhaltiges, magnetischen Materials mit mindestens drei Legierungskomponenten R, Eisen (Fe) und M, wobei der Material-Anteil der Fe-Komponente mindestens 60 Atom-% beträgt und in dem Material eine tetragonale ThMn₁₂-Struktur ausgebildet ist, als hartmagnetischer Werkstoff. Ein derartiges Material mit einer solchen Struktur ist z.B. in der Veröffentlichung "Journal of Applied Physics", Vol. 52, No. 3, März 1981, Seiten 2077 und 2078 beschrieben.The invention relates to the use of an iron-containing, magnetic material with at least three alloy components R, iron (Fe) and M, the material component of the Fe component being at least 60 atomic% and formed in the material a tetragonal ThMn12 structure is, as a hard magnetic material. Such a material with such a structure is e.g. in the publication "Journal of Applied Physics", Vol. 52, No. 3, March 1981, pages 2077 and 2078.

Der bekannte hartmagnetische ternäre Werkstoff Neodym(Nd)-Eisen(Fe)-Bor (B) mit hohem Energieprodukt und verhältnismäßig niedriger Curie-Temperatur bei 300°C besteht im wesentlichen aus der tetragonalen Phase Nd₂F₁₄B bzw. Nd11,8Fe82,3B5,9 (vgl. z.B. "J.Appl.Phys.", Vol. 55, No. 6, Pt. 2, März 1984, Seiten 2083 bis 2087). Dabei bildet von den 68 Atomen in der Elementarzelle (P4₂/mm) die Mehrzahl der Fe-Atome zwei Lagen von Sigma-Typ-ähnlicher Struktur. Die enge Packung und der hohe Anteil von Eisen werden als Ursache für die hohe Sättigungsmagnetisierung Ms der Phase (1,6 T bei 300 K) gegesehen, während die Beteiligung des leichten Seltenerdmetalls zusammen mit der komplizierten Struktur der Elementarzelle für die ausgeprägte magnetische Kristallanisotropie (Anisotropiefeldstärke Ha ca. 9 T bei 300 K) verantwortlich gemacht wird (vgl. z.B. "Solid State Commun.", Vol. 51, No. 11, Sept. 1984, Seiten 857 bis 860). Darüber hinaus sind auch substituierte Legierungen mit anderen Seltenerdmetallen, Übergangselementen bzw. Metalloiden anstelle von Nd, Fe bzw. B untersucht worden. So ist z.B. in der eingangs genannten Veröffentlichung aus "J.Appl.Phys." auf die strukturellen und magnetischen Eigenschaften eines besonderen Dreistoffsystems vom Typ R-Fe-M eingegangen. Hierbei sind R Yttrium (Y) und M Mangan (Mn). Dieses Dreistoffsystem bildet unter anderem mit seiner stöchiometrischen Zusammensetzung Y(Mn1-xFex)₁₂ eine anisotrope, tetragonale ThMn₁₂-Struktur aus, die antiferromagnetisch ist.The well-known hard magnetic ternary material neodymium (Nd) iron (Fe) boron (B) with a high energy product and relatively low Curie temperature at 300 ° C consists essentially of the tetragonal phase Nd₂F₁₄B or Nd 11.8 Fe 82.3 B 5.9 (see, for example, "J.Appl.Phys.", Vol. 55, No. 6, Pt. 2, March 1984, pages 2083 to 2087). Of the 68 atoms in the unit cell (P4₂ / mm), the majority of Fe atoms form two layers with a structure similar to the sigma type. The close packing and the high proportion of iron are seen as the cause of the high saturation magnetization Ms of the phase (1.6 T at 300 K), while the involvement of the light rare earth element together with the complicated structure of the unit cell for the pronounced magnetic crystal anisotropy (anisotropy field strength Ha approx. 9 T at 300 K) is responsible (see, for example, "Solid State Commun.", Vol. 51, No. 11, Sept. 1984, pages 857 to 860). In addition, substituted alloys with other rare earth metals, transition elements or metalloids instead of Nd, Fe or B have also been investigated. For example, in the publication from "J.Appl.Phys." on the structural and magnetic Properties of a special three-substance system of the type R-Fe-M. Here, R is yttrium (Y) and M is manganese (Mn). This three-substance system forms, inter alia, with its stoichiometric composition Y (Mn 1-x Fe x ) ₁₂ an anisotropic, tetragonal ThMn₁₂ structure which is antiferromagnetic.

Entsprechende Strukturen besitzen intermetallische Phasen mit 26 Atomen in der Elementarzelle (Raumgruppe I4/mmm). In Figur 1 der Zeichnung ist diese Struktur für die bekannte binäre Verbindung MoBe₁₂ schematisch veranschaulicht (vgl. K.Schubert: "Kristallstrukturen zweikomponentiger Phasen", Springer-Verlag, 1964, Seiten 166 und 167). Dabei stellen in dieser Figur die ausgefüllten Vollkreise die einzelnen durch Mo besetzten Gitterpunkte dar, während die Hohlkreise die Lage der Be-Gitterpunkte zeigen. Eine entsprechende Struktur ist auch für das genannte System Y(Mn1-xFex)₁₂ mit einem Fe-Anteil bis zu x = 0,67 festzustellen. Bei einem noch größeren Fe-Gehalt der Legierung ist zusätzlich eine zweite Phase von der hexagonalen Struktur Th₂Zn₁₇ zu beobachten.Corresponding structures have intermetallic phases with 26 atoms in the unit cell (space group I4 / mmm). In Figure 1 of the drawing, this structure is schematically illustrated for the known binary compound MoBe₁₂ (cf. K.Schubert: "crystal structures of two-component phases", Springer-Verlag, 1964, pages 166 and 167). In this figure, the filled solid circles represent the individual lattice points occupied by Mo, while the hollow circles show the position of the loading lattice points. A corresponding structure can also be found for the aforementioned system Y (Mn 1-x Fe x ) ₁₂ with an Fe component up to x = 0.67. With an even larger Fe content of the alloy, a second phase of the hexagonal structure Th₂Zn₁₇ can also be observed.

Aus der Entgegenhaltung FIZIKO MATEMATICESKIE I TECHNICESKIE NAUKI/DOKLADY AKADEMII NAUK UKRAINSKOJ SSR, No.5, 1985, Seiten 83-84, US; O.I. BODAK et. al: "CICTEMA Ce-Fe-Mo", Zusammenfassung, sind Legierungen bekannt, die der Zusammensetzung gemäß Anspruch 1 entsprechen. Aus dieser Entgegenhaltung ist jedoch kein Hinweis auf magnetische Eigenschaften dieser Materialien zu entnehmen. Demgegenüber besteht die Erfindung in der Verwendung des im Anspruch 1 angegebenen Materials als hartmagnetischer Werkstoff.From the document FIZIKO MATEMATICESKIE I TECHNICESKIE NAUKI / DOKLADY AKADEMII NAUK UKRAINSKOJ SSR, No.5, 1985, pages 83-84, US; OI BODAK et. al: "CICTEMA Ce-Fe-Mo", summary, alloys are known which correspond to the composition according to claim 1. However, no reference to the magnetic properties of these materials can be found in this document. In contrast, the invention consists in the use of the material specified in claim 1 as a hard magnetic material.

Das Material hat somit einen hohen Anteil von preisgünstigem, ein hohes magnetisches Moment besitzendem Fe, ohne daß ein Metalloid wie z.B. B, Si oder Ge erforderlich wäre. Der Erfindung liegt nun die Erkenntnis zugrunde, daß die zumindest ternären Legierungen der Zusammensetzung R-Fe-Mo bzw. R-Fe-W magnetische Eigenschaften mit Curie-Temperaturen im Bereich von z.B. ungefähr 100°C bis 200°C und Sättigungsmagnetisierungen im Bereich von z.B. etwa 0,6 bis 1,0 Tesla aufweisen. Mit den angegebenen prozentualen Anteilen der einzelnen Legierungskomponenten ist dabei gewährleistet, daß die im Hinblick auf die magnetischen Eigenschaften günstige ThMn₁₂-Phase in dem Material zumindest zu einem erheblichen Teil mit enthalten ist. Bei einigen Legierungskomponenten aus der Gruppe der Seltenerdmetalle wie insbesondere bei Gadolinium (Gd) oder Samarium (Sm) tritt zusätzlich eine magnetische Anisotropie auf. Außerdem kann durch Zusatz weiterer Komponenten zu dem genannten ternären System, insbesondere durch Zusatz von Kobalt (Co), gegebenenfalls die Curie-Temperatur oder die Sättigungsmagnetisierung erhöht werden.The material thus has a high proportion of inexpensive Fe, which has a high magnetic moment, without a metalloid such as e.g. B, Si or Ge would be required. The invention is based on the knowledge that the at least ternary alloys of the composition R-Fe-Mo or R-Fe-W have magnetic properties with Curie temperatures in the range of e.g. approximately 100 ° C to 200 ° C and saturation magnetizations in the range of e.g. have about 0.6 to 1.0 Tesla. With the stated percentages of the individual alloy components, it is ensured that the ThMn 12 phase which is favorable with regard to the magnetic properties is at least to a considerable extent included in the material. Magnetic anisotropy also occurs with some alloy components from the group of rare earth metals, in particular with gadolinium (Gd) or samarium (Sm). In addition, the Curie temperature or the saturation magnetization can optionally be increased by adding further components to the ternary system mentioned, in particular by adding cobalt (Co).

Das Material braucht unter Einschluß zwangsläufiger Verunreinigungen nicht nur allein aus der Phase mit der tetragonalen ThMn₁₂-Struktur zu bestehen; vielmehr können in ihm auch noch andere Phasen der genannten Legierungskomponenten enthalten sein.The material does not only have to consist of inevitable impurities from the phase with the tetragonal ThMn₁₂ structure; rather, other phases of the alloy components mentioned can also be contained in it.

Außerdem kann das Material vorteilhaft in einen anderen Werkstoff eingelagert oder an einen solchen angelagert sein, so daß es z.B. einen Bestandteil eines Misch-oder Verbundwerkstoffes bildet.In addition, the material can advantageously be embedded in or attached to another material, so that it e.g. forms part of a mixed or composite material.

Weitere vorteilhafte Ausgestaltungen gehen aus den Unteransprüchen hervor.Further advantageous embodiments emerge from the subclaims.

Die Erfindung wird nachfolgend anhand eines Ausführungsbeispieles noch weiter erläutert, wobei auch auf die Zeichnung Bezug genommen wird. Dabei zeigt Figur 2 graphisch einen Teil eines isothermen Schnittes in dem Dreikomponentensystem Fe-Mo-Nd. Aus Figur 3 gehen temperaturabhängige Magnetisierungskurven für spezielle Fe₈₀Mo₁₂R₈-Legierungen hervor, während die Figuren 4 und 5 die Curie-Temperatur bzw. Sättigungsmagnetisierung für diese Phasen im Vergleich zu den bekannten Materialien Fe₁₄R₂B zeigen. Dabei sind mit R jedes beliebige Seltenerdmetall, insbesondere aber die Elemente Cer (Ce), Neodym (Nd), Samarium (Sm), Gadolinium (Gd), Dysprosium (Dy) und Erbium (Er) gemeint. Für R können gegebenenfalls auch Kombinationen aus mehreren Seltenerdmetallen gewählt werden.The invention is further explained below using an exemplary embodiment, reference also being made to the drawing. FIG. 2 graphically shows part of an isothermal section in the three-component system Fe-Mo-Nd. Figure 3 shows temperature-dependent magnetization curves for special Fe₈₀Mo₁₂R₈ alloys, while Figures 4 and 5 show the Curie temperature and saturation magnetization for these phases in comparison to the known materials Fe₁₄R₂B. R means any rare earth metal, but in particular the elements cerium (Ce), neodymium (Nd), samarium (Sm), gadolinium (Gd), dysprosium (Dy) and erbium (Er). Combinations of several rare earth metals can optionally be selected for R.

Zur Herstellung des Materials der Zusammensetzung R-Fe-Mo wird von Fe und Mo mit jeweiligem Gehalt von 99,97 % und von den einzelnen Seltenerdmetallen R von 99,9 % mit maximal 1000 ppm Seltenerdoxiden ausgegangen. Die Seltenerdmetalle werden unmittelbar vor der Bearbeitung in Teile geeigneter Größe zersägt und die Oberflächen durch Naßschleifen sowie Ultraschall-Behandlung in Wasser und anschließend in Äthanol gesäubert. Anschließend werden die Legierungskomponenten unter Argon als Schutzgas auf einem wassergekühlten Kupfer-Schiff mittels der von einem Hochfrequenz-Generator erzeugten Hitze zusammengeschmolzen, wobei zunächst das Fe und das Mo verflüssigt und dann das jeweilige Seltenerdmetall zugegeben werden. Die so entstandenen ternären Legierungen werden in der Regel noch wenigstens 5 mal zur völligen Mischung mit Hochfrequenzenergie auf dem Kupfer verflüssigt und rasch abgekühlt. Im Fall von Samarium-Legierungen braucht man hingegen nur einmal in einem Aluminiumoxid-Tiegel umzuschmelzen. Zur Homogenisierung der ternären Legierungen wird schließlich bei etwa 1050 bis 1200°C, d.h. etwa 150° unterhalb der jeweiligen Schmelztemperatur, etwa 1 Stunde lang geglüht. Hierzu befinden sich die einzelnen Körper aus den Legierungen unter Argon als Schutzgas auf einer Aluminiumoxidunterlage in einem verschlossenen Niob-Hohlzylinder, der induktiv geheizt wird.For the production of the material of the composition R-Fe-Mo, Fe and Mo with a respective content of 99.97% and the individual rare earth metals R of 99.9% with a maximum of 1000 ppm of rare earth oxides are assumed. The rare earth metals are sawn into parts of suitable size immediately before processing and the surfaces are cleaned by wet grinding and ultrasound treatment in water and then in ethanol. The alloy components are then melted together under argon as protective gas on a water-cooled copper ship by means of the heat generated by a high-frequency generator, with the Fe and Mo first being liquefied and then the respective rare earth metal being added. The resulting ternary alloys are usually liquefied at least 5 times for complete mixing with high-frequency energy on the copper and rapidly cooled. In the case of samarium alloys, on the other hand, one only has to remelt in an aluminum oxide crucible. In order to homogenize the ternary alloys, finally annealing is carried out at about 1050 to 1200 ° C, ie about 150 ° below the respective melting temperature, for about 1 hour. For this the individual bodies made of the alloys are under argon as a protective gas on an aluminum oxide base in a closed niobium hollow cylinder which is heated inductively.

Nach der Synthese und dem wiederholten Schmelzen und Erstarren sind die einzelnen Legierungen zunächst noch mehrphasig. Neben der tetragonalen ThMn₁₂-Phase ist in diesem Falle auch die rhomboedrische Th₂Zn₁₇-Phase neben weiteren Phasen zu beobachten. Hingegen liegen die Legierungen nach dem abschließenden Glühen zur Homogenisierung praktisch nur einphasig vor, wobei Reste von Oxid und weiteren Phasen mit einem Anteil von insgesamt maximal 3 Vol.-% zu beobachten sind. Die einzelnen Phasen dieser Legierungen lassen sich dabei durch metallographische und röntgenographische Analysen ausmachen.After the synthesis and repeated melting and solidification, the individual alloys are initially still multi-phase. In addition to the tetragonal ThMn₁₂ phase, the rhombohedral Th₂Zn₁₇ phase can also be observed in this case in addition to other phases. On the other hand, after the final annealing for homogenization, the alloys are practically only in one phase, with residues of oxide and other phases with a total of a maximum of 3% by volume being observed. The individual phases of these alloys can be identified by metallographic and X-ray analysis.

Figur 2 gibt die entsprechenden Konzentrationsverhältnisse für das Dreikomponentensystem Fe-Mo-Nd bei einem isothermen Schnitt für etwa 1200°C in einer allgemein üblichen graphischen Darstellung wieder. Hierbei ist von einer dreiseitigen Fläche ausgegangen, deren Eckpunkte durch die 3 Legierungskomponenten Fe, Mo, Nd (jeweils dort mit einer Konzentration zu 100 %) festgelegt sind. Die Seiten des Konzentrationendreiecks geben dann die Zusammensetzungen der binären Systeme MoFe, FeNd und NdMo wieder. Die Dreiecksfläche ist mit einem Gitter aus Parallelen zu den 3 Seiten überzogen, wobei benachbarte Parallen jeweils 2 Atom-% beabstandet sind. In der Figur ist lediglich die hier interessierende Fe-Ecke des Dreikomponentensystems näher ausgeführt. Wie sich aus der Figur ablesen läßt, ist das ternäre Feld, zu dem die Phase Nd₈Fe₈₀Mo₁₂ mit ThMn₁₂-Struktur gehört, von dem Bereich, der von Nd₂Fe₁₇ mit Th₂Zn₁₇-Struktur ausgeht, durch ein Zweiphasen-Feld getrennt. Die einzelnen Kristallstrukturen können beispielsweise dadurch bestimmt werden, daß man entsprechende Pulver mit Hilfe bekannter Röntgendiffraktometer untersucht.FIG. 2 shows the corresponding concentration ratios for the three-component system Fe-Mo-Nd in an isothermal cut for about 1200 ° C. in a generally common graphical representation. This is based on a three-sided surface, the corner points of which are determined by the 3 alloy components Fe, Mo, Nd (each with a concentration of 100% there). The sides of the concentration triangle then reflect the compositions of the binary systems MoFe, FeNd and NdMo. The triangular surface is covered with a grid of parallels to the 3 sides, with neighboring parallels being spaced 2 atom% each. In the figure, only the Fe corner of the three-component system that is of interest here is detailed. As can be seen from the figure, the ternary field, to which the phase Nd₈Fe₈₀Mo₁₂ with ThMn₁₂ structure belongs, is separated from the area starting from Nd₂Fe₁₇ with Th₂Zn₁₇ structure by a two-phase field. The individual crystal structures can be determined, for example, by examining corresponding powders with the aid of known X-ray diffractometers.

Gemäß der Erfindung soll das magnetische Material zu einem erheblichen Anteil die Phase mit der ThMn₁₂-Struktur aufweisen. Um diese Forderung zu erfüllen, sind die Anteile der einzelnen Legierungskomponenten in dem Material von vornherein festgelegt. Und zwar wird allgemein für die Fe-Komponente ein Anteil zwischen 60 und 85 Atom-%, für die R-Komponente ein Anteil zwischen 2 und 20 Atom-% und für die M-Komponente ein Anteil zwischen 4 und 35 Atom-% gewählt.According to the invention, the magnetic material should have a significant proportion of the phase with the ThMn₁₂ structure. To meet this requirement, the proportions of the individual alloy components in the material are fixed from the outset. In general, a proportion between 60 and 85 atom% is chosen for the Fe component, a proportion between 2 and 20 atom% for the R component and a proportion between 4 and 35 atom% for the M component.

Um eine Existenz der ThMn₁₂-Struktur zu mindestens 50 Vol.-% zu gewährleisten, wird von der Fläche des entsprechenden Konzentrationendreiecks eine 5-eckige Teilfläche ausgewählt, die durch die folgenden 5 Punkte P1 bis P5 festgelegt ist:

Figure imgb0001
In order to ensure the existence of the ThMn₁₂ structure to at least 50% by volume, a pentagonal partial area is selected from the area of the corresponding concentration triangle, which is defined by the following 5 points P1 to P5:
Figure imgb0001

In Figur 2 sind diese 5 Punkte in das Konzentrationendreieck des Dreikomponentensystems Nd-Fe-Mo eingetragen. Dabei schließt die durch eine strichpunktierte Linie veranschaulichte 5-eckige Fläche den gestrichelt eingezeichneten Bereich mit der ThMn₁₂-Struktur ein, der sich näherungsweise durch die folgenden Punkt p1 bis p5 beschreiben läßt:

Figure imgb0002
In Figure 2, these 5 points are entered in the concentration triangle of the three-component system Nd-Fe-Mo. The 5-sided area illustrated by a dash-dotted line includes the area with the ThMn 12 structure shown in broken lines, which can be described approximately by the following points p1 to p5:
Figure imgb0002

Die Magnetisierung M in Abhängigkeit von der Temperatur T ist für erfindungsgemäße ternäre, magnetisch nicht-orientierte, einphasige Legierungen des Typs Fe₈₀Mo₁₂R₈ in dem Diagramm der Figur 3 dargestellt. Hierbei ist ein externes Magnetfeld von 10 kA/cm zugrundegelegt. Aus der Darstellung M² = f (T) läßt sich dann die jeweilige Curie-Temperatur Tc als Schnittpunkt des geraden Teiles der entsprechenden Kurve mit der Temperaturachse bestimmen. Die entsprechend ermittelten Werte gehen aus der folgenden Tabelle hervor. In dieser Tabelle sind außerdem die Sättigungsmagnetisierungen Ms der einzelnen Legierungen bei Zimmertemperatur und einem Außenfeld von 70 kOe angegeben. Die Sättigungsmagnetisierungen Ms werden z.B. mit Hilfe eines Vibrationsmagnetometers an entsprechenden kunststoffgebundenen, magnetfeldorientierten Pulvern bestimmt.

Figure imgb0003
The magnetization M as a function of the temperature T is shown in the diagram of FIG. 3 for ternary, magnetically non-oriented, single-phase alloys of the type Fe₈₀Mo₁₂R₈. This is based on an external magnetic field of 10 kA / cm. From the representation M² = f (T), the respective Curie temperature T c can then be determined as the intersection of the straight part of the corresponding curve with the temperature axis. The corresponding values determined are shown in the following table. This table also shows the saturation magnetizations Ms of the individual alloys at room temperature and an external field of 70 kOe. The saturation magnetizations Ms are determined, for example, with the aid of a vibration magnetometer on corresponding plastic-bound, magnetic field-oriented powders.
Figure imgb0003

Die in der vorstehenden Tabelle aufgelisteten Curie-Temperaturen Tc sind in Figur 4 in einem Diagramm den Curie-Temperaturen bekannter ternärer Legierungen vom Typ Fe₁₄R₂B mit denselben Seltenerdkomponenten R gegenübergestellt. Diese bekannten Legierungen sind dabei der Literaturstelle "Proc. 8th Int. Workshop on Rare-Earth-Magnets", Dayton, Ohio (USA), 1985, Seiten 423 bis 440 entnommen.The Curie temperatures T c listed in the table above are compared in FIG. 4 in a diagram with the Curie temperatures of known ternary alloys of the Fe₁₄R₂B type with the same rare earth components R. These known alloys are taken from the reference "Proc. 8th International Workshop on Rare Earth Magnets", Dayton, Ohio (USA), 1985, pages 423 to 440.

Entsprechend der Darstellung gemäß Figur 4 sind in Figur 5 die Sättigungsmagnetisierungen Ms der erfindungsgemäßen Legierungen Fe₈₀Mo₁₂R₈ und der aus der genannten Literaturstelle "Proc. 8th Int. Workshop on Rare-Earth-Magnets" zu entnehmenden Legierungen Fe₁₄R₂B verglichen.According to the representation according to FIG. 4, the saturation magnetizations Ms of the alloys Fe₈₀Mo₁₂R₈ according to the invention and the alloys Fe₁₄R₂B to be taken from the cited reference "Proc. 8th Int. Workshop on Rare Earth Magnets" are compared in FIG.

Wie aus den beiden Figuren 4 und 5 ersichtlich, weisen die Phasen Fe₈₀Mo₁₂R₈ Curie-Temperaturen Tc im Bereich von etwa 100 bis 200°C und Sättigungsmagnetisierungen Ms im Bereich von etwa 0,6 bis 1 T auf. Der Gang der einzelnen Werte mit der Ordnungszahl der Seltenerdmetalle R entspricht dabei dem der bekannten Reihe Fe₁₄R₂B. Die höchste Curie-Temperatur wird bei der Gadolinium-, die höchste Sättigungsmagnetisierung bei der Neodym-Phase gefunden. Die Vertreter mit leichten Seltenerdmetallen, bei denen ferromagnetische Kopplung zwischen R- und Fe-Momenten zu erwarten ist, besitzen dabei eine höhere Sättigungsmagnetisierung als die Phasen mit schweren Seltenerdmetallen. Dabei haben Fe₈₀Mo₁₂Sm₈ und Fe₈₀Mo₁₂Gd₈ magnetische Anisotropie, die bei der Samarium-Phase besonders ausgeprägt ist.As can be seen from the two Figures 4 and 5, the phases Fe₈₀Mo₁₂R₈ Curie temperatures T c in the range of about 100 to 200 ° C and saturation magnetizations Ms in the range of about 0.6 to 1 T. The course of the individual values with the atomic number of the rare earth metals R corresponds to that of the known series Fe₁₄R₂B. The highest Curie temperature is found in the gadolinium, the highest saturation magnetization in the neodymium phase. The representatives with light rare earth metals, in which ferromagnetic coupling between R and Fe moments can be expected, have a higher saturation magnetization than the phases with heavy rare earth metals. Fe₈₀Mo₁₂Sm₈ and Fe₈₀Mo₁₂Gd₈ have magnetic anisotropy, which is particularly pronounced in the samarium phase.

Gemäß dem vorstehend dargestellten Ausführungsbeispiel wurde davon ausgegangen, daß es sich bei der M-Komponente des Materials R-Fe-M um das Element Mo handelt. Entsprechende Verhältnisse sind jedoch auch bei einem zumindest teilweisen Ersatz dieses Metalls aus der Chrom-Gruppe durch das Metall Wolfram (W) gegeben.According to the exemplary embodiment shown above, it was assumed that the M component of the material R-Fe-M is the element Mo. Corresponding conditions also exist, however, when this metal from the chromium group is at least partially replaced by the metal tungsten (W).

Außerdem wurde als Ausführungsbeispiel eine ternäre Legierung gewählt. Neben den genannten drei Legierungskomponenten kann jedoch das Material noch einen geringen Anteil von maximal etwa 10 Atom-% mindestens einer weiteren Legierungskomponente enthalten. So kann insbesondere den Nd- und Sm-Legierungen vorteilhaft Kobalt (Co) bis maximal 8 Atom-% zulegiert sein, um die Curie-Temperatur und/oder die Sättigungsmagnetisierung zu erhöhen. Dabei ersetzt der Co-Anteil einen entsprechenden Anteil der Fe-Komponente. Die sich so ergebende quaternäre Legierung Nd₈Fe₇₄Co₈Mo₁₀ hat z.B. eine um etwa 100°C höhere Curie-Temperatur und eine um ca. 0,3 T höhere Sättigungsmagnetisierung als die ternäre Legierung Nd₈Fe₈₂Mo₁₀ ohne Co.In addition, a ternary alloy was chosen as the exemplary embodiment. In addition to the three alloy components mentioned, however, the material can also contain a small proportion of at most about 10 atom% of at least one further alloy component. For example, cobalt (Co) up to a maximum of 8 atom% can advantageously be alloyed to the Nd and Sm alloys in order to increase the Curie temperature and / or the saturation magnetization. The Co portion replaces a corresponding portion of the Fe component. The resulting quaternary alloy Nd₈Fe₇₄Co₈Mo₁₀ has e.g. 100 ° C higher Curie temperature and 0.3 T higher saturation magnetization than the ternary alloy Nd₈Fe₈₂Mo₁₀ without Co.

Als Ausgangsmaterialien für hartmagnetische Werkstoffe sind wegen der hohen Kristallanisotropie die ternären Phasen mit Sm und die quaternären Phasen mit Sm und Co von besonderem Interesse. Hierbei lassen sich Anisotropiefeldstärken bis ca. 90 kOe erreichen.Because of the high crystal anisotropy, the ternary phases with Sm and the quaternary phases with Sm and Co are of particular interest as starting materials for hard magnetic materials. Anisotropy field strengths of up to approx. 90 kOe can be achieved.

Das Material mit 3 oder mehr Legierungskomponenten läßt sich nicht nur in reiner Form verwenden. Vielmehr kann es vorteilhaft auch Bestandteil eines Misch- oder Verbundwerkstoffes sein. So ist z.B. eine Einlagerung in oder Anlagerung an anorganische Substanzen wie Gläser oder Keramiken, beispielsweise Al₂O₃ , SiC oder B, sowie auch in oder an organische Materialien möglich.The material with 3 or more alloy components can not only be used in pure form. Rather, it can advantageously also be part of a mixed or composite material. For example, storage in or addition to inorganic substances such as glasses or ceramics, for example Al₂O₃, SiC or B, and also in or on organic materials is possible.

Claims (10)

  1. Use of an iron-containing material having a tetragonal ThMn₁₂-structure, with at least the three alloy components R, iron (Fe) and M, whereby
    a) for R at least one element from the group of rare-earth metals is provided and for M molybdenum (Mo) and/or tungsten (W) is provided,
    b) the Fe proportion constitutes 60 to 85 % by atom,
    c) the R proportion lies between 2 and 20 % by atom and
    d) the Mo proportion and/or W proportion amounts to 4 to 35 % by atom,
    as magnetically hard material.
  2. Use according to claim 1, characterized in that the proportions of the alloy components are chosen such that in a graphic representation of the concentration ratios of the three-component system R-Fe-M, in a manner known per se as a triangular face with joints formed by the components, a sectional point is obtained, which lies on the pentagonal face stretched through the following points P1, P2, P3, P4 and P5: R [% by atom] Fe [% by atom] M [% by atom] P1: 4 65 31 P2: 4 85 11 P3: 9 85 6 P4: 15 79 6 P5: 15 65 20
  3. Use according to claim 1 or 2, characterized in that the Fe proportion amounts to a maximum of 82 % by atom.
  4. Use according to one of claims 1 to 3, characterized in that in addition to a phase with the ThMn₁₂-structure at least another further phase of the system R-Fe-M is present.
  5. Use according to one of claims 1 to 4, characterized in that in addition to the three alloy components R, Fe and M at least another further alloy component is provided.
  6. Use according to claim 5, characterized in that the proportion of the further alloy component constitutes a maximum of 10 % by atom.
  7. Use according to claim 5 or 6, characterized in that cobalt (Co) with a maximum proportion of 8 % by atom is provided as further component, by which a corresponding proportion of the Fe component is substituted.
  8. Use according to one of claims 1 to 7, characterized in that the R-component comprises at least two rare-earth metals.
  9. Use according to one of claims 1 to 8, characterized in that it is incorporated into or added on to another material.
  10. Use according to claim 9, characterized in that it is a constituent of a mixed or composite material.
EP88101333A 1987-02-11 1988-01-29 Use of a material as a hard magnetic material Expired - Lifetime EP0278342B1 (en)

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DE3832472A1 (en) * 1988-09-23 1990-03-29 Siemens Ag METHOD FOR PRODUCING A MATERIAL WITH A HARD MAGNETIC PHASE FROM POWDER-BASED STARTING COMPONENTS
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