Bonded magnet, magnet roll, a ferrite powder used therefor and method for producing same

An anisotropic granulated powder for bonded magnets constituted by an aggregate of ferrite powder, said ferrite powder having a substantially magnetoplumbite-type crystal structure, an average diameter of 0.9-2 μm, and a basic composition represented by the following general formula:

• (A1-xRx)O.n[(Fe1-yMy)2O3] by atomic ratio,
• wherein A is Sr and/or Ba;
• R is at least one of rare earth elements including Y, La being indispensable;
• M is at least one element selected from the group consisting of Co, Mn, Ni and Zn;
• and x, y and n are numbers meeting the following conditions:
• 0.01≦x≦0.4,
• [x/(2.6n)]≦y≦[x/(1.6n)], and
• 5≦n≦6,
• said anisotropic granulated powder having an average diameter of more than 2 μm and 10 μm or less, and the total of an Si content (calculated as SiO2) and a Ca content (calculated as CaO) being 0.2 weight % or less, and the total of an Al content (calculated as Al2O3) and a Cr content (calculated as Cr2O3) being 0.13 weight % or less.

A magnet roll having a plurality of magnetic poles on a surface thereof, at least one magnetic pole portion thereof being constituted by a bonded magnet composed of 85-95 weight % of ferrite powder and 15-5 weight % of a binder, said ferrite powder having a substantially magnetoplumbite-type crystal structure, an average diameter of 0.9-2 μm, and a basic composition represented by the following general formula:

• (A1-xRx)O.n[(Fe1-yMy)2O3] by atomic ratio,
• wherein A is Sr and/or Ba;
• R is at least one of rare earth elements including Y, La being indispensable;
• M is at least one element selected from the group consisting of Co and/or Zn;
• and x, y and n are numbers meeting the following conditions:
• 0.01≦x≦0.4,
• [x/(2.6n)]≦y≦[x/(1.6n)], and
• 5≦n≦6,
• the total of an Si content (calculated as SiO2) and a Ca content (calculated as CaO) being 0.2 weight % or less, and the total of an Al content (calculated as Al2O3) and a Cr content (calculated as Cr2O3) being 0.13 weight % or less in said ferrite powder.

A magnet roll having a plurality of magnetic poles on a surface thereof, at least one magnetic pole portion thereof being constituted by a bonded magnet composed of 85-95 weight % of an anisotropic granulated powder having an average diameter of more than 2 μm and 10 μm or less and 15-5 weight % of a binder, said anisotropic granulated powder being an aggregate of a ferrite powder having a substantially magnetoplumbite-type crystal structure, an average diameter of 0.9-2 μm, and a basic composition represented by the following general formula:

• (A1-xRx)O.n[(Fe1-yMy)2O3] by atomic ratio,
• wherein A is Sr and/or Ba;
• R is at least one of rare earth elements including Y, La being indispensable;
• M is at least one element selected from the group consisting of Co and/or Zn;
• and x, y and n are numbers meeting the following conditions:
• 0.01≦x≦0.4,
• [x/(2.6n)]≦y≦[x/(1.6n)], and
• 5≦n≦6,
• the total of an Si content (calculated as SiO2) and a Ca content (calculated as CaO) being 0.2 weight % or less, and the total of an Al content (calculated as Al2O3) and a Cr content (calculated as Cr2O3) being 0.13 weight % or less in said ferrite powder.

A method for producing a ferrite powder for bonded magnets having a substantially magnetoplumbite-type crystal structure and an average diameter of 0.9-2 μm, said ferrite powder having a basic composition represented by the following general formula:

• (A1-xRx)O.n[(Fe1-yMy)2O3] by atomic ratio,
• wherein A is Sr and/or Ba;
• R is at least one rare earth element including Y, La being indispensable;
• M is at least one element selected from the group consisting of Co, Mn, Ni and Zn;
• and x, y and n are numbers meeting the following conditions:
• 0.01≦x≦0.4,
• [x/(2.6n)]≦y≦[x/(1.6n)], and
• 5≦n≦6,
• the total of an Si content (calculated as SiO2) and a Ca (calculated as CaO) being 0.2 weight % or less, and the total of an Al content (calculated as Al2O3) and a Cr content (calculated as Cr2O3) being 0.13 weight % or less, wherein said basic composition is prepared by mixing an iron oxide with a compound containing an A element, a compound containing an R element and a compound containing an M element and then calcining the resultant mixture for solid-state reaction, wherein iron oxide obtained by spray-roasting a waste liquid generated by washing steel with hydrochloric acid is used as said iron oxide.

A method for producing a ferrite powder for bonded magnets having a substantially magnetoplumbite-type crystal structure and an average diameter of 0.9-2 μm, said ferrite powder having a basic composition represented by the following general formula:

• (A1-xRx)O.n[(Fe1-yMy)2O3] by atomic ratio,
• wherein A is Sr and/or Ba;
• R is at least one rare earth element including Y, La being indispensable;
• M is at least one element selected from the group consisting of Co, Mn, Ni and Zn;
• and x, y and n are numbers meeting the following conditions:
• 0.01≦x≦0.4,
• [x/(2.6n)]≦y≦[x/(1.6n)], and
• 5≦n≦6,
• the total of an Si content (calculated as SiO2) and a Ca content (calculated as CaO) being 0.2 weight % or less, and the total of an Al content (calculated as Al2O3) and a Cr content (Calculated as Cr2O3) being 0.13 weight % or less, said method comprising the steps of preparing a magnetically isotropic ferrite composition having said basic composition by calcination;
• finely pulverizing the resultant calcined powder;
• and heat-treating the pulverized ferrite powder, wherein said finely pulverizing is carried out by a dry method or by a wet method under the condition that a slurry concentration is adjusted to 60 weight % or more.

A method for producing a ferrite powder for bonded magnets having a substantially magnetoplumbite-type crystal structure and an average diameter of 0.9-2 μm, said ferrite powder having a basic composition represented by the following general formula:

• (A1-xRx)O.n[(Fe1-yMy)2O3] by atomic ratio,
• wherein A is Sr and/or Ba;
• R is at least one rare earth element including Y, La being indispensable;
• M is at least one element selected from the group consisting of Co, Mn, Ni and Zn;
• and x, y and n are numbers meeting the following conditions:
• 0.01≦x≦0.4,
• [x/(2.6n)]≦y≦[x/(1.6n)], and
• 5≦n≦6,
• the total of an Si content (calculated as SiO2) and a Ca content (calculated as CaO) being 0.2 weight % or less, and the total of an Al content (calculated as Al2O3) and a Cr content (calculated as Cr2O3) being 0.13 weight % or less, said method comprising the steps of preparing a magnetically isotropic ferrite composition having said basic composition by calcination;
• finely pulverizing the resultant calcined powder;
• and heat-treating the pulverized ferrite powder, wherein coarse pulverization is carried out before said finely pulverizing.

A method for producing a ferrite powder for bonded magnets having a substantially magnetoplumbite-type crystal structure and an average diameter of 0.9-2 μm, said ferrite powder having basic composition represented by the following general formula:

• (A1-xRx)O.n[(Fe1-yMy)2O3] by atomic ratio,
• wherein A is Sr and/or Ba;
• R is at least one rare earth element including Y, La being indispensable;
• M is at least one element selected from the group consisting of Co, Mn, Ni and Zn;
• and x, y and n are numbers meeting the following conditions:
• 0.01≦x≦0.4,
• [x/(2.6n)]≦y≦[x/(1.6n)], and
• 5≦n≦6,
• the total of an Si content (calculated as SiO2) and a Ca content (calculated as CaO) being 0.2 weight % or less, and the total of an Al content (calculated as Al2O3) and a Cr content (calculated as Cr2O3) being 0.13 weight % or less, said method comprising the steps of preparing a magnetically isotropic ferrite composition having said basic composition by calcination;
• finely pulverizing the resultant calcined powder;
• and heat-treating the pulverized ferrite powder, wherein said magnetically isotropic ferrite powder is dry-pulverized to said average diameter, and immersed in water after the heat-treating.

A method for producing a ferrite powder for bonded magnets having a substantially magnetoplumbite-type crystal structure and an average diameter of 0.9-2 μm, said ferrite powder having a basic composition represented by the following general formula:

• (A1-xRx)O.n[(Fe1-yMy)2O3] by atomic ratio,
• wherein A is Sr and/or Ba;
• R is at least one rare earth element including Y, La being indispensable;
• M is at least one element selected from the group consisting of Co, Mn, Ni and Zn;
• and x, y and n are numbers meeting the following conditions;
• 0.01≦x≦0.4,
• [x/(2.6n)]≦y≦[x/(1.6n)], and
• 5≦n≦6,
• the total of an Si content (calculated as SiO2) and a Ca content (calculated as CaO) being 0.2 weight % or less, and the total of an Al content (calculated as Al2O3) and a Cr content (calculated as Cr2O3) being 0.13 weight % or less, said method comprising the steps of preparing a magnetically isotropic ferrite composition having said basic composition by calcination;
• finely pulverizing the resultant calcined powder;
• and heat-treating the pulverized ferrite powder, wherein said heat-treating is at a temperature of 750-900° C.

A method for producing a ferrite powder for bonded magnets having a substantially magnetoplumbite-type crystal structure and an average diameter of 0.9-2 μm, said ferrite powder having a basic composition represented by the following general formula:

• (A1-xRx)O.n[(Fe1-yMy)2O3] by atomic ratio,
• wherein A is Sr and/or Ba;
• R is at least one rare earth element including Y, La being indispensable;
• M is at least one element selected from the group consisting of Co, Mn, Ni and Zn;
• and x, y and n are numbers meeting the following conditions:
• 0.01≦x≦0.4,
• [x/(2.6n)]≦y≦[x/(1.6n)], and
• 5≦n≦6,
• wherein the total of an Si content (calculated as SiO2) and a Ca content (calculated as CaO) is 0.15 weight % or less, and the total of an Al content (calculated as Al2O3) and a Cr content (calculated as Cr2O3) is 0.1 weight % or less in said ferrite powder, said method comprising the steps of preparing a magnetically isotropic ferrite composition having said basic composition by calcination;
• finely pulverizing the resultant calcined powder;
• and heat-treating the resulting pulverized ferrite powder.

A method for producing a ferrite powder for bonded magnets having a substantially magnetoplumbite-type crystal structure and an average diameter of 0.9-2 μm, said ferrite powder having a basic composition represented by the following general formula:

• (A1-xRx)O.n[(Fe1-yMy)2O3] by atomic ratio,
• wherein A is Sr and/or Ba;
• R is at least one rare earth element including Y, La being indispensable;
• M is at least one element selected from the group consisting of Co, Mn, Ni and Zn;
• and x, y and n are numbers meeting the following conditions:
• 0.01≦x≦0.4,
• [x/(2.6n)]≦y≦[x/(1.6n)], and
• 5≦n≦6,
• 5≦n≦6,
• the total of an Si content (calculated as SiO2) and a Ca content (calculated as CaO) being 0.2 weight % or less, and the total of an Al content (calculated as Al2O3) and a Cr content (calculated as Cr2O3) being 0.13 weight % or less, said method comprising the steps of preparing a magnetically isotropic ferrite composition having said basic composition by calcination;
• finely pulverizing the resultant calcined powder;
• and heat-treating the pulverized ferrite powder, wherein said M element is Co and/or Zn.