Engineering of synthesis of Eu,Ca-α-sialon phosphor via the solid-liquid synthesis

The aim of this research was to find out the way of the synthesis temperature reduction without deterioration of the phosphors optical properties. Since crystallization of Eu,Ca-α-sialon occurs by means of sialon crystallization from the oversaturated oxynitride liquid, thus a rise of the liquid phase amount could be performed not only via an increase of temperature but also through the application of the low eutectic additives. Al₂O₃ and AlF₃ additives have been chosen as the sources of liquid at the reaction temperature. The syntheses were carried out in a graphite furnace at 1650°C and the powders were characterized for their phase composition, particles morphology, excitation and emission properties and their quantum yield of luminescence was compared. It has been found that alumina addition to the initial mixture of nitrides was the most effective in formation of sialon solid solution with a minor contamination with AlN. Emission intensity of sialon phosphor was doubled if they were synthesized with each of additives. Quantum yield of tested phosphors was over 0.85 if excited at 380 nm for alumina and similar for AlF₃ modified composition. A significant particles refinement was observed if AlF₃ was applied.