| 简介 |
PROBLEM TO BE SOLVED : To provide a method which can inexpensively and stably produce a magnet powder containing a rare-earth element, a transition metal and nitrogen, and having high characteristics, by a reduction and diffusion reaction.
SOLUTION : This production method includes : a first step of slurrying an iron oxide powder with a water medium, charging a predetermined amount of an oxide of a rare-earth element into the slurry to dissolve the oxide while adding a dilute acid of 1 mol/L or less into the slurry so that the pH value of the slurry is maintained in a range of 2-5, adding a salt of an alkali metal or an alkaline-earth metal to the slurry to adjust the pH so as to be higher than 7.0, and consequently producing a raw mixed powder which has a hydroxide of the rare-earth element precipitated on the surface of the iron oxide; a second step of subjecting the obtained raw mixed powder to hydrogen heat-treatment; a third step of adding a predetermined amount of an alkaline-earth metal which is a component of a reducing agent, to the mixed powder which has been subjected to the hydrogen heat-treatment, mixing them, heat-treating the mixture in an inert gas atmosphere, and then cooling the mixture in the same atmosphere to obtain a rare-earth-iron based mother alloy; a forth step of subsequently nitriding the mother alloy; and a fifth step of wet-treating the nitrided material to separate and remove a byproduct of the component of the reducing agent, and then pulverizing the obtained crude powder.
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