Gas-Reduction–Nitridation Synthesis of CaAlSiN₃:Eu²⁺ Fine Powder Phosphors for Solid-State Lighting

CaAlSiN 3:Eu 2+ fine powder phosphors were successfully synthesized from the fully oxidic system CaO/Al 2 O 3 /SiO 2 using the gas-reduction–nitridation (GRN) method. The GRN reaction was conducted at low temperatures of ∼1370 °C to obtain nitrided precursor powders that could be converted into nearly single-phase CaAlSiN 3 by a moderate heat treatment at 1600 °C for 4 h in a N 2 atmosphere of 0.92 MPa. Highly efficient CaAlSiN 3:Eu 2+ red-emitting phosphors were obtained using a fluoride activator, with external quantum efficiencies of up to 72%.