Investigation of the physical properties of a blue-emitting phosphor produced using a rapid exothermic reaction

The blue-emitting phosphor cerium activated yttrium silicate, (Y1-mCem)(2)SiO5, was prepared via a novel synthesis technique called combustion synthesis. Combustion synthesis involves a highly exothermic redox reaction between metal nitrates and an organic fuel to produce a solid powder. The combustion synthesis parameter, the fuel-to-oxidizer ratio, has a direct effect on the physical properties of the as-synthesized powders due to the reaction temperature being dependent on the variation of this ratio. Thus, varying the fuel-to-oxidizer ratio produced powders with varying crystallite sizes, carbon contamination and surface areas, which in turn affected the luminescent efficiencies of the as-synthesized powders. The reaction temperature was found to reach a maximum with a 60% fuel rich mixture, with the powders exhibiting the largest crystallite sizes, smallest surface area and carbon contamination, and highest luminescent efficiency in the as-synthesized state. As-synthesized powders exhibit a high degree porosity due to the large amount of gas to solid formed. To more accurately predict the specific surface areas of porous powders, the standard geometrical model used for gas absorption measurements was modified for porous particles and found to more accurately predict the specific surface area of highly porous powders. (C) 2002 Elsevier Science B.V. All rights reserved.