Powder synthesis of Ca-α'-SiAlON as a host material for phosphors

Fine powders of Ca-alpha'-SiAlON have been synthesized from the system CaO-Al2O3-SiO2, by using an NH3-CH4 gas mixture as a reduction-nitridation agent. Completion of the reduction-nitridation was achieved at low temperatures of 1400-1500 degreesC without unfavorable particle coarsening or carbon contamination, while the phase purity and crystallinity of the powders were markedly improved by a postsynthesis heat treatment. The resulting fine Ca-a'-SiAlON powders possessed high purity and uniform discrete particle morphology, which meet the requirements for the new application of SiAlON ceramics as a host material for phosphors. The reduction-nitridation synthesis of the yellow-emitting Ca-alpha'-SiAlON:Eu powder phosphor was also performed for the first time, and better photoluminescence property was demonstrated compared to that of the conventionally prepared powder.