Y2O3 hollow spheres are prepared by coating the anionic poly (styrene-methyl acrylic acid) (PSA-A) latex with an amorphous yttrium layer and subsequent calcining at elevated temperatures in air. The aging temperature, aging time, the concentrations of Y(III) and urea are systematically varied to establish the optimum conditions for the formation of the coating shell. Zeta potential measurement, transmission electron microscopy, scanning electron microscopy, X-ray diffraction and infrared measurements are used to characterize the PSA-A latex, core-shell spheres and Y2O3 hollow spheres. A mechanism for the formation of the PSA-A/yttrium compounds core-shell spheres is suggested. The key factor to prepare smooth-coated spheres is obtained. (c) 2006 Springer Science + Business Media, Inc.