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US 2011/0210810 A1Published application
Nd based sintered magnet and its preparation
AssigneeShin-Etsu Chemical Co., Ltd.
InventorsKoji Miyata, Takehisa Minowa, Hajime Nakamura, Koichi Hirota, Masakatsu Honshima
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Abstract
The invention provides a sintered Nd base magnet which is free of a decline of remanence, has a high coercive force, especially at the edges thereof, is unsusceptible to demagnetization even at high temperature, and is suited for use in permanent magnet rotary machines.
Claims6
A method for preparing a sintered Nd base magnet comprising the steps of:
- providing a sintered Nd base magnet block having surfaces and a magnetization direction,
- coating the surfaces of the magnet block excluding the surface perpendicular to the magnetization direction with a Dy or Tb oxide powder, a Dy or Tb fluoride powder, or a Dy or Tb-containing alloy powder,
- treating the coated block at a high temperature for causing Dy or Tb to diffuse into the block, and
- cutting the block in a plane perpendicular to the magnetization direction into a magnet segment having a coercive force distribution on the cut section that the coercive force is high at the periphery and lower toward the inside and a constant coercive force distribution in the magnetization direction.
1 more element
Dependencies are inferred from the claim text.