Powder Synthesis of Y-α-SiAlON and Its Potential as a Phosphor Host

The Y-α-SiAlON fine powders have been successfully synthesized from the system Y 2 O 3 −Al 2 O 3 −SiO 2, by using the gas-reduction−nitridation method. Completion of the nitridation was achieved at temperatures <1500 °C without unfavorable carbon contamination and SiC formation. While the presence of Y-containing intermediate phases inhibited the formation of pure α′ phase in the as-synthesized state, transient liquid-phase formation promoted under the postsynthesis heat treatment enabled the preparation of near single-phase Y-α-SiAlON powders. The synthesized Y-α-SiAlON:Eu 2+ powder exhibited a bright orange emission under near-UV to blue light excitation showing the applicability to the phosphor-converted white light-emitting diodes, whereas the quantum efficiency and the thermal stability were found to be low compared to the Ca-stabilized analogue. The first-principles calculations on the electronic structures of Y- and Ca-α-SiAlON:Eu 2+ were performed for the first time, which clearly demonstrated the effects of modifying cations on their photoluminescent properties.