Abstract: Ultrafine yttrium oxide powders were prepared by homogeneous precipitation method，with urea as precipitant， Y2O3（coarse powder） and nitric acid as raw materials.The influences of temperature，pH，and different dispersants on the product′s morphology were investigated.The thermal decomposition properties of precursors were analyzed by TG-DTG.The morphologies and microstructures of the samples were characterized by X-ray diffractometer（XRD） and scanning electron microscope（SEM）.Results showed that under different conditions，nanometer yttrium oxide with the morphologies of plate， sheet，flower flocculent，and spherical could be prepared.Combined with the reaction conditions，a preliminary inference mechanism for the formation of the various morphologies was made.

Key words: yttrium oxide, different morphologies, urea, reaction mechanism