Manufacturing method

PROBLEM TO BE SOLVED : To obtain an abrasive which has an improved cutting capability and enables a flawless finished surface to be obtd. by subjecting a cerium-contg. rare earth material to treatment with a mineral acid, then to treatment with ammonium fluoride, and to roasting. SOLUTION : A cerium-contg. rare earth material ground to an average particle size of 0.5-3 μm is treated with a mineral acid selected from hydrgchloric, sulfuric, and nitric acids having a concn. of about 0.1-2 N to give a cerium- contg. rare earth material slurry. The slurry is treated with an aq. ammonium fluoride soln. having a fluorine concn. of 5-60 g/l, then filtered, dried, roasted at 600-1, 100 deg.C for 1-10 hr, allowed to cool, ground, and classified to give an abrasive having an average particle size of 0.4-3.0 μm and a fluorine content of 0.5-15 wt.%. The abrasive is dispersed in water or an aq. org. solvent to give a slurry having a concn. of 5-30 wt.%, and the slurry is mixed with 0.1-0.8 wt.% org. dispersant [e.g. poly(sodium acrylate)] for preventing foaming and then used.