Synthesis of Red‐Emitting, Small Particle Size Luminescent Oxides Using an Optimized Combustion Process

A novel ceramic synthesis technique, combustion synthesis, was explored to produce red-emitting Cr{sup 3+}-doped Y{sub 3}Al{sub 5}O{sub 12} and Eu{sup 3+}-doped Y{sub 2}O{sub 3} phosphors with improved physical and luminescent properties. This technique involves the reaction of metal nitrates (oxidizers) and an organic fuel (urea, carbohydrazide, glycine) at 500 C. Resulting powders are well-crystallized, with a large surface area and small particle size. The spectral energy distribution was observed using photoluminescence measurements. The effects of processing parameters such as type of fuel, fuel-to-oxidizer ratio, furnace temperature, and batch water content were studied. An increase in phosphor brightness with increasing reaction temperature was observed. Postreaction heat treatments (1000, 1300, and 1600 C) increased the luminous intensity of as-synthesized powders. Residual carbon content and chromium site symmetry were investigated as possible explanations for the increase in brightness with increasing heat treatment temperature. By tailoring the reaction chemistry, the optimal conditions for producing the most luminescent phosphors have been identified.