Effects of pre-treatment of starting powder with sulfuric acid on the fabrication of yttria transparent ceramics

The effects of pre-treating a nano-sized Y2O3 powder with sulfuric acid were studied. Both the structural evolution and sintering behavior as a function of SO42−-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 Y2O3 nanopowder with excellent sintering property was obtained by calcinating the powders treated with 7 mol% sulfuric acid. The optimum sulfate dosage can be well correlated with a single layer coverage of SO42−-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.