The effects of pre-treating a nano-sized Y 2 O 3 powder with sulfuric acid were studied. Both the structural evolution and sintering behavior as a function of SO 4 2− -ion concentrations were investigated. The surface morphologies and aggregation state of particles were notably affected by the sulfuric acid-based treatment. The powder untreated revealed particle of flat surfaces and sharp edges, whereas the powders with sulfate dosage were composed of round particles of isotropic surfaces after calcination. Dispersive Y 2 O 3 nanopowder with excellent sintering property was obtained by calcinating the powders treated with 7mol% sulfuric acid. The optimum sulfate dosage can be well correlated with a single layer coverage of SO 4 2− -ions over the particle surfaces, protecting particles from forming hard agglomerates by contributing to mass transportation mechanisms leading to particle coarsening upon calcination. All the ceramics prepared using treated-powders were transparent after vacuum sintering at 1700°C, whereas it was opaque for the sample without sulfate dosage.