| 简介 |
PROBLEM TO BE SOLVED : To efficiently obtain fine particles with a uniform particle size which do not aggregate even in a mass-producing scale by previously heating an aq. soln. of mineral acid salts of rare earth elements to a specified temp., adding urea to the soln. while maintaining that temp. to precipitate basic carbonates of rare earth elements, separating the obtd. precipitate from the liquid and calcining at a specified temp. SOLUTION : An aq. soln. of mineral acid salts, preferably nitrates of rare earth elements selected from Nd, Gd, Tb, Dy, Ho, Er, Tm, Yb is previously heated at >=80 deg.C and lower than the boiling point. Urea is added to the soln. while that temp. is maintained so as to precipitate basic carbonates of rare earth elements. The obtd. precipitate is separated from the liquid and then calcined at 700 to 1300 deg.C, preferably 800 to 1000 deg.C to obtain particles having 0.1 to 10 μm average particle diameter D50 and 0.3 to 1.0 μm grain size distribution. The initial concn. of the mineral acid salts is preferably 0.011 to 0.08 mol/L and the add amt. of urea is preferably 3 to 100 times equiv. as the concn. of the whole rare earth elements. |
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