Preparation of Highly Crystallized Yttrium Oxysulfide Suspension via a Novel Colloidal Processing.

High-crystallized Y2O2S suspension was synthesized by a novel two-step method of high temperature solid-state reaction and subsequent colloidal processing. The synthesis method proposed in this study retains all advantages of the high temperature solid-state reaction method. The obtained data agrees with that of the PDF card, which indicates the product is pure Y2O2S crystals. The results show that the prepared Y2O2S particles are highly crystallized without any significant defects. The fine smooth particles were almost regular, exhibiting an approximately subspherical shape. Quantitative image analysis of particles suggests a mean particle size of 120±34 nm. That is to say, the yttrium oxysulfide colloid prepared by this method have a very narrow size distribution. The obtained ethanol suspension shows Tyndall effect when irradiated with laser of wavelength 532 nm. In addition, the particles exhibit excellent dispersibility in ethanol solution. This is rarely observed for the covalent compounds, which generally present poor dispersibility in solution. As is known to all, the state of the dispersion depends on the acid leaching process. The acid leaching process facilitates the adsorption of ethanol molecules on the surface of the particles. The electrostatic repulsive force among colloidal particles will improve their rheological properties and dispersibility in solution. In this study, the particles can be dispersed well in ethanol after acid leaching. The method'proposed in this study can be extended for the preparation of mono-dispersed oxysulfide nanophosphors and may provide an efficient way for the preparation of stable covalent compound dispersions.