Precipitation Of Oxalic Acid/Ammonium Bicarbonate For Preparation Of Rare Earth Oxide Powders

Rare earth oxides with micro or submicro grades are largely used in the fields of powder ceramic and fluorescent powder, in which the morphology, particle size and distribution of particle size of rare earth oxides have important effects on their application properties such as flowability, specific surface area and stacking property.Yttrium oxides with cubic, block, thick block, and spherical morphologies were prepared by precipitation of oxalic acid, in which the important factors, such as addition sequence, ammonia concentration, addition time of ammonia, stirring condition and precipitation temperature were investigated. Yttrium oxides with desired morphology and particle size were prepared by the effective control of preparation procedures. The cubic Y-Eu oxide (Eu of4.47wt%, D5o=8.7～10μm,σ/m=0.3) for company A and the block Yo.70Gd0.25Eu0.05O3powder of D50=2±.2μm for company B were prepared in the industrial scale. The spherical yttrium oxide powder of D50=2.4～5μm was prepared in the lab scale.The rare earth oxide powders of yttrium, samarium, gadolinium and holmium oxides with different particle sizes and distribution of particle size were prepared by precipitation of ammonium bicarbonate, in which the aging and hydrothermal treatments could avoid the filtering difficulty of rare earth carbonates and the agglomeration of rare earth oxide powders after calcination. By controlling the ratio of reactants, solution concentration, velocity of adding reactants, reaction temperature and hydrothermal treatment, the particle sizes of rare earth oxide powders were controlled. Gadolinium oxide powder without agglomeration and grinding for the preparation material of fluorescent powder was prepared by precipitation of ammonium bicarbonate and hydrothermal treatment.