Powder Synthesis of Ca-α‘-SiAlON as a Host Material for Phosphors

Fine powders of Ca-α‘-SiAlON have been synthesized from the system CaO−Al 2 O 3 −SiO 2, by using an NH 3 −CH 4 gas mixture as a reduction−nitridation agent. Completion of the reduction−nitridation was achieved at low temperatures of 1400−1500 °C 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-α‘-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-α‘-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.