Process for preparing high-purity ultra-fine alumina powder

The present invention is the preparation process of high-purity superfine alumina powder for tricolor phosphor powder, long afterglow photoluminescent powder and semi-transparent luminous ceramic powder. Water solution of aluminum ammonium sulfate is added into water solution of ammonium bicarbonate slowly while stirring and the two kinds of material in the molar ratio of 2-50 are reacted at 30-60 deg.c and pH 8-10 for 1-3 hr to obtain water solution of aluminum ammonium carbonate. The water solution of aluminum ammonium carbonate is deposited, aged and filtered to obtain solid aluminum ammonium carbonate, which is washed, stoved and calcined to obtain high-purity superfine alumina powder.