Hitachi Metals, Ltd.

Neomax Co., Ltd.

Etsushi Oda

Seiichi Hosokawa

Yoshinori Kobayashi

Sachio Toyota

Hiroshi Iwasaki

Yasunobu Ogata

A sintered ferrite magnet comprising (a) a ferrite phase having a hexagonal M-type magnetoplumbite structure comprising Ca, an element R which is at least one of rare earth elements and indispensably includes La, an element A which is Ba and/or Sr, Fe, and Co as indispensable elements, the composition of metal elements of Ca, R, A, Fe and Co being represented by the general formula of CaRAFeCo, wherein the atomic ratios (1-x-y), x, y and z of these elements and the molar ratio n meet the relations of 0.3&#x2266;(1-x-y)&#x2266;0.65, 0.2&#x2266;x&#x2266;0.65, 0&#x2266;y&#x2266;0.2, 0.03&#x2266;z&#x2266;0.65, and 4&#x2266;n&#x2266;7, and (b) a grain boundary phase indispensably containing Si, the amount of Si being more than 1% by mass and 1.8% or less by mass (calculated as SiO) based on the entire sintered ferrite magnet, and its production method.

Method for producing sintered ferrite magnet, and sintered ferrite magnet

A method comprising the steps of mixing raw material powders to a composition comprising metal elements of Ca, La, Sr, Ba, Fe and Co, whose atomic ratios are represented by the general formula of CaLa(SrBa)FeCo, wherein 1&#x2212;x&#x2212;y, x and y are values in a region defined by a coordinate a: (0.470, 0.297, 0.233), a coordinate b: (0.300, 0.392, 0.308), a coordinate c: (0.300, 0.300, 0.400), a coordinate d: (0.400, 0.200, 0.400) and a coordinate e: (0.470, 0.200, 0.330) in a ternary diagram of x, y, and 1&#x2212;x&#x2212;y, y' and z, and n representing a molar ratio meet 0.5&#x2266;y&#x2032;&#x2266;1, 0.2&#x2266;z&#x3c;0.25, and 5.2&#x3c;n&#x3c;5.6; calcining the raw material powder mixture; pulverizing the calcined body; molding the calcined powder; and sintering the resultant green body; 0.1% or more and less than 1.5% by mass of SiObeing added to the raw material powder mixture, the calcined body or the calcined powder; and 0-2% by mass (as CaO) of CaCObeing added to the calcined body or the calcined powder.

Calcined ferrite, sintered ferrite magnet and its production method

A sintered ferrite magnet comprising main phases of ferrite having a hexagonal M-type magnetoplumbite structure, first grain boundary phases existing between two main phases, and second grain boundary phases existing among three or more main phases, the second grain boundary phases being dispersed in its arbitrary cross section, and the second grain boundary phases having an average area of less than 0.2 &#x3bc;m, are produced by calcining, pulverizing, molding and sintering raw material powders having the general formula of CaLaAFeCo, wherein 1&#x2212;x&#x2212;y, x, y and z and n representing a molar ratio are in desired ranges; 1.8% or less by mass of SiOand 2% or less by mass (as CaO) of CaCObeing added to a calcined body after calcining and before molding; and the sintering step being conducted with a temperature-elevating speed of 1-4&#xb0; C./minute in a range from 1100&#xb0; C. to a sintering temperature, and a temperature-lowering speed of 6&#xb0; C./minute or more in a range from the sintering temperature to 1100&#xb0; C.

Sintered ferrite magnet and its production method

A sintered ferrite magnet comprising (a) a ferrite phase having a hexagonal M-type magnetoplumbite structure comprising Ca, an element R which is at least one of rare earth elements and indispensably includes La, an element A which is Ba and/or Sr, Fe, and Co as indispensable elements, the composition of metal elements of Ca, R, A, Fe and Co being represented by the general formula of CaRAFeCo, wherein the atomic ratios (1-x-y), x, y and z of these elements and the molar ratio n meet the relations of 0.3&#x2266;(1-x-y) &#x2266;0.65, 0.2&#x2266;x&#x2266;0.65, 0&#x2266;y&#x2266;0.2, 0.03&#x2266;z&#x2266;0.65, and 4&#x2266;n&#x2266;7, and (b) a grain boundary phase indispensably containing Si, the amount of Si being more than 1% by mass and 1.8% or less by mass (calculated as SiO) based on the entire sintered ferrite magnet, and its production method.

A sintered ferrite magnet comprising a first granular ferrite compound phase containing Ca, La, Fe and Co and having a Curie temperature Tcbetween 415&#xb0; C. and 430&#xb0; C., and a second granular ferrite compound phase containing Sr, La, Fe and Co and having a Curie temperature Tcbetween 437&#xb0; C. and 455&#xb0; C., the volume ratio of the first ferrite compound phase being 50-90%, and the volume ratio of the second ferrite compound phase being 10-50%, with their total volume ratio being 95% or more.

An oxide magnetic material includes a ferrite with a hexagonal structure as its main phase. Metallic elements included in the oxide magnetic material are represented by the formula:CaLaSrFeCo,where atomic ratios x, x' and y and a molar ratio n satisfy 0.4&#x2266;x&#x2266;0.6, 0.01&#x2266;x&#x2032;&#x2266;0.3, 0.2&#x2266;y&#x2266;0.45 and 5.2&#x2266;n&#x2266;5.8, respectively.

Oxide magnetic material

A ferrite magnet obtained by adding a ferrite having a hexagonal W-type magnetoplumbite structure to a ferrite having a hexagonal M-type magnetoplumbite structure, in which a portion of Sr, Ba, Pb or Ca is replaced with at least one element that is selected from the group consisting of the rare-earth elements (including Y) and Bi and that always includes La, during the fine pulverization process thereof. By adding a small amount of the element such as Co, Ni, Mn or Zn to the ferrite already having the hexagonal M-type magnetoplumbite structure during the fine pulverization process thereof, the magnetic properties can be improved.

Permanent magnet and method for preparation thereof

A ferrite magnet obtained by adding at least one element selected from the group consisting of Co, Ni, Mn and Zn to a ferrite having a hexagonal M-type magnetoplumbite structure, in which a portion of Sr, Ba, Pb or Ca is replaced with at least one element that is selected from the group consisting of the rare-earth elements (including Y) and Bi and that always includes La, during the fine pulverization process thereof, and then subjecting the mixture to re-calcining and/or sintering process(es). By adding a small amount of the element such as Co, Ni, Mn or Zn to the ferrite already having the hexagonal M-type magnetoplumbite structure during the fine pulverization process thereof, the magnetic properties can be improved.

A ferrite magnet obtained by adding a ferrite having a spinel-type structure to a ferrite having a hexagonal M-type magnetoplumbite structure, in which a portion of Sr, Ba, Pb or Ca is replaced with at least one element that is selected from the group consisting of the rare-earth elements (including Y) and Bi and that always includes La, during the fine pulverization process thereof. By adding a small amount of the element such as Co, Ni, Mn or Zn to the ferrite already having the hexagonal M-type magnetoplumbite structure during the fine pulverization process thereof, the magnetic properties can be improved.

A ferrite magnet obtained by adding either an oxide of Mn or oxides of Mn and Co to a ferrite having a hexagonal M-type magnetoplumbite structure, in which a portion of Sr, Ba, Pb or Ca is replaced with at least one element that is selected from the group consisting of the rare earth elements (including Y) and Bi and that always includes La, during the fine pulverization process thereof, and then subjecting the mixture to re-calcining and/or sintering process(es). By adding a small amount of the element Mn or elements Mn and Co to the ferrite already having the hexagonal M-type magnetoplumbite structure during the fine pulverization process thereof, the magnetic properties can be improved.

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Mishima-gun, Japan

Etsushi Oda