Synthesis of AlN: Eu²⁺ green phosphors by a simple direct nitridation method

Eu-doped aluminum nitride phosphors were successfully prepared using simple direct nitridation of a metallic aluminum and Eu₂ O₃ powder mixture in flowing ammonia. AlN formed at reaction temperatures >900°C, and Eu³⁺ transformed into the secondary oxide phase EuAl₂ O₄ in the nitridation condition. Phase pure AlN was obtained by post-heat treatment of the nitridated product at 1600°C for 3 h in a nitrogen atmosphere, with an Eu²⁺ doping concentration < 0.5%. The phosphors exhibited broad green emission centered at 521 nm under 363 nm excitation. The luminescence of the phosphor was significantly influenced by the post-heat treatment temperature, which affected the dissolution of Eu²⁺ , phase purity, crystallinity, and particle size of the AlN host.