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  • 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
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• • C—CHEMISTRY; METALLURGY
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  • C01G51/00—Compounds of cobalt
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  • 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
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  • 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
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  • 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
  • C04B35/2641—Compositions containing one or more ferrites of the group comprising rare earth metals and one or more ferrites of the group comprising alkali metals, alkaline earth metals or lead
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
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  • 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
• • 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
  • H01F1/10—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 non-metallic substances, e.g. ferrites, e.g. [(Ba,Sr)O(Fe2O3)6] ferrites with hexagonal structure
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2002/00—Crystal-structural characteristics
  • C01P2002/50—Solid solutions
  • C01P2002/52—Solid solutions containing elements as dopants
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
  • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/12—Surface area
• • C—CHEMISTRY; METALLURGY
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  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/42—Magnetic properties

Definitions

• the invention relates to the field of permanent magnets, and more particularly ferrite type magnets comprising the magnetoplumbite phase.
• the present invention relates to permanent magnets of ferrite type based on the magnetoplumbite phase of formula M Fe 12 O 19 with M equal to Sr, Ba, etc., in which the element M is partially substituted by an element R, chosen among rare earths or bismuth, and in which the element Fe is partially substituted by at least one transition metal T.
• Such magnets are already known to have high magnetic properties, as disclosed in Japanese application J10-149910 or in European application EP-0 905 718 or in international application WO99 / 34379. In these applications, it is common to use lanthanum La as element R, and cobalt Co as element T.
• the manufacture of such magnets comprises the following stages: a) formation of a mixture of the raw materials either by a wet process to form a dispersion, or by a dry process to form granules, b) calcination of the mixture around 1250 ° C.
• a clinker, or chamotte comprising the desired magnetoplumbite phase, said mixture, either in the form of a dispersion or of granules, being introduced into a calcination oven, c) wet grinding of the clinker until an aqueous dispersion of particles is obtained with a particle size close to 1 ⁇ m, in the form of a paste with around 70% dry extract, d) the paste is concentrated and compressed under an orienting magnetic field of approximately 1 Tesla and under a pressure of 30 to 50 MPa so as to obtain a green tablet, called "green compact" in English, anisotropic and 87% extract dry, e) after drying and removal of the remaining water, sintering of the green tablet, f) final machining to obtain the magnet of predetermined shape.
• the object of the invention is a method for simultaneously achieving these goals, as well as the magnets obtained by this method. DESCRIPTION OF THE INVENTION
• a mixture MP of the raw materials MP M , MP F , MP R and MP T relating respectively to the elements M, Fe, R and T, typically in the form of powders, is formed in a mixing means, typically a mixer operating batchwise of oxide, carbonate or hydroxide, consisting of particles P, denoted respectively P M , PR, PF and P_, the raw material MP F relating to the element Fe, typically iron oxide Fe 2 O 3 , and the raw material MP M constituting so-called main raw materials, the raw materials MP R and MP T constituting raw materials MPs
• c) wet grinding of said clinker is carried out, typically in a dispersing apparatus in an aqueous medium, to obtain a homogeneous dispersion C of fine deagglomerated particles with an average particle size of less than 1.2 ⁇ m, d) concentrates and compresses said particles under orienting magnetic field to form a tablet with green D, anisotropic, manipulable and of predetermined shape, e) sintering said tablet with green D anisotropic to obtain a sintered element E, f) optionally carrying out final dimensions of said sintered element E, typically by machining.
• This process is characterized in that, in the mixture MP in step a) of the process, at least one of the substitution raw materials MP R OR MP T has a particle size Gs, typically measured by the BET specific surface in m 2 / g and specifically noted GR OR GT for respectively the substitute raw materials MPR OR MPT, chosen according to the particle size G F of the main raw material MP F and according to the mass percentage% S of said raw material of substitution MPs with respect to said main raw material MP F taking into account said formula of ferrite M ⁇ -X R x Fe 12-y T y O 19 , so as to obtain a mixture MP comprising, statistically and ideally, whatever the formula of ferrite, a predetermined proportion of particles P R OR P T compared to those of particles P F.
• Gs typically measured by the BET specific surface in m 2 / g and specifically noted GR OR GT for respectively the substitute raw materials MPR OR MPT, chosen according to the particle size G F of the main raw material MP F and according to the mass percentage% S of said
• the Applicant has recognized the importance of the relative GR and / or Gr particle size of the alternative raw materials considered in relation to both the GF particle size of the ferric oxide constituting the main raw material MP F , and with the composition of ferrite which varies with the substitution indices x and y in the formula of ferrite M 1-x R x Fe 12-y T y O 19 .
• the Applicant has observed significant increases in the ratio b. ⁇ , all other things being equal, both with regard to the manufacturing process which is not found to be substantially modified, as with regard to the final properties of the magnets ferrites. Indeed, as the tests will show, it is remarkable to note that the method according to the invention not only makes it possible to obtain high values of the hK ratio but also that it also retains the high levels reached for the magnetic induction Br and the coercive field HcJ, which is particularly interesting in practice.
• FIG. 1 is a diagram indicating the particle sizes G R on the abscissa and G ⁇ on the ordinate - expressed in m 2 / g, of the various tests 1 to 4.
• FIG. 2 is a recording of the square character for magnets obtained according to the different tests 1 to 4.
• G F denoting the particle size of the main raw material MP F , namely ferric oxide, the constant K s being equal to (100 /% S) 1 3 . (dp / ds) 273 , d F and d s .
• sub-domains are also defined, such as the set of domains A + B + C defined by the unique condition G R > 2.53GF in which tests 2 and 3 are situated, or even the set domains A + D + G defined by the unique condition G ⁇ > 3.38GF in which trials 2 and 4 are situated.
• the particle size Gs of at least one substitution raw material MPs can be at least equal to 0.7. GS T H; OR also at least equal to 0.8, or also at least equal to 0.9, and preferably at least equal to G STH .
• Said particle size Gs can correspond to the particle size G R of the substitution raw material MP R.
• said particle size Gs may correspond to the particle size Gr of the substitute raw material MPT-
• G ⁇ > G ⁇ H 3.38G F
• the set of domains B + E + H is defined by the unique condition 0.7.
• said particle size G s can correspond simultaneously to the particle size GR of the substitute raw material MP R and to the particle size G ⁇ of the substitute raw material MP T.
• a preferred domain is thus defined, domain A in FIG. 1, and sub-domains B, D and E for which at least one substitution raw material is such that 0.7 G OR _TH ⁇ G R and / or G s ⁇ G OR TTH -
• the particle size G F of the raw material MP F can be between 1 and 10 m 2 / g.
• the invention is not limited to a particular formula of magnetoplumbite type ferrite, by the nature of the elements M, R and T in the general formula of ferrite indicated above.
• the method according to the invention can be applied to the manufacture of any ferrite in any one of claims 1 to 10 in which the values of x and of y relating respectively to the element R and to the element T can range from 0.05 to 0.5, and preferably from 0.10 to 0.25.
• the element R can be chosen equal to La and the element T can be chosen equal to Co.
• the constant K is taken equal to 3.38 for the substitution element T equal to cobalt, and the constant K is taken equal to 2.53 for the substitution element R taken equal to lanthanum.
• Another subject of the invention comprises the ferrite magnets obtained by the method of the invention.
• the performance index DP Br + 0.5.HcJ, with Br in mT and HcJ in kA.m '1 , is at least equal at 580, and preferably greater than 590, at least equal to 595
• the square character h ⁇ Hk HcJ in% of the demagnetization curve, with Hk and HcJ being expressed in kA.m "1 and with Hk being equal at H (Br-10%), is at least equal to 0.89, and preferably greater than 0.90, or even greater than 0.92.
• raw material MP M Also used as raw material MP M , source of the element Sr, strontium carbonate SrCO 3 in powder of specific surface equal to 1.38 m 2 / g.
• source of the element Sr, strontium carbonate SrCO 3 in powder of specific surface equal to 1.38 m 2 / g.
• Test 1 is to be considered as a test belonging to the state of the art.
• the manufacturing process comprises the following stages: a) a wet-phase mixing was carried out for 2 hours, so as to obtain a homogeneous mixture, b) after having isolated and dried the mixture formed, the mixture was calcined at 1250 ° C for 2 h in an oven, to form a ferrite clinker, c) the clinker was finely ground with the incorporation of additives (1% by weight of CaSiO 3 and 0.94% by weight of SrCO 3 ), in two stages: during a first stage, wet grinding was carried out for 9 hours with 6 mm balls, and during a second stage, wet grinding was carried out for 7 hours with 3 mm balls , 2 mm.
• Hk The values of Hk are plotted on FIG. 3 on the ordinate (in kA.ni "1 ) and on the abscissa the different tests 1 to 4, also spaced and ordered so as to have Hk increasing from one test to the next.
• the curve marked "MP R " relating to the element La, passes through the lower point ("black” diamond) with ordinate 0.875 and abscissa "-" because the average of h K of the two tests - tests 1 and 4 - in which the raw material MP R relating to the element La has a "low” particle size is worth: (0.86 + 0.89) / 2, or 0.875.
• the preponderant influence of the particle size of the raw material relative to the element La compared to that of the element Co could be explained by the differences in size and atomic weight between the two elements Co and La.
• the results obtained could be explained if one considers the speed of diffusion of the various chemical elements necessary for the synthesis of ferrite: the influence of the particle size would be all the greater as the chemical element in question would be cumbersome and large, so that the lower intrinsic diffusion would somehow be "compensated" for by a smaller particle size.
• G TTH 3.38.
• Q F 12.33 m 2 / g and ordinate equal to 0.7.
• the preferred domain of the invention is defined by the double condition G ⁇ > G TTH and GR> G RTH , domain A corresponding to the rectangle with crossed lines at the top right of Figure 1, while the domain excluded from l
• the invention is defined by the double condition G ⁇ 0.77GTTH and GR ⁇ 0.77G RT H, area corresponding to the "white" rectangle at the bottom left of Figure 1.
• domains noted B to H in FIG. 1 there are different intermediate domains, domains noted B to H in FIG. 1.
• domain C of test 3 is preferable to domain G of test 4.
• the invention has the following advantages: - on the one hand, it can be applied to all magnets of the ferrite type.

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• 2001
  • 2001-04-25 FR FR0105569A patent/FR2824178B1/fr not_active Expired - Fee Related
• 2002
  • 2002-04-09 US US10/118,451 patent/US6811718B2/en not_active Expired - Fee Related
  • 2002-04-23 EP EP02735479A patent/EP1381578A1/fr not_active Withdrawn
  • 2002-04-23 WO PCT/FR2002/001378 patent/WO2002085810A1/fr not_active Application Discontinuation
  • 2002-04-23 CN CNB028088263A patent/CN1330605C/zh not_active Expired - Fee Related
  • 2002-04-23 BR BR0209180-1A patent/BR0209180A/pt not_active Application Discontinuation
  • 2002-04-23 KR KR1020037013966A patent/KR100870690B1/ko not_active IP Right Cessation
  • 2002-04-23 MX MXPA03009726A patent/MXPA03009726A/es active IP Right Grant
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