Synthesis, crystal structure and photoluminescence of novel blue-emitting Eu²⁺-doped (SiC)_x-(AlN)_1-x phosphors by a nitriding combustion reaction

Novel blue-emitting phosphors with the chemical composition of (SiC)_x-(AlN)_1-x:yEu²⁺ (x = 0.06-0.50, y = 0.001-0.01) were synthesized by a nitriding combustion reaction route, and the crystal structure, luminescence properties and thermal stability of the (SiC)_x-(AlN)_1-x:yEu²⁺ phosphors were investigated by theoretical and experimental approaches. First-principles calculation results prove that the solid solution of SiC with AlN promotes the doping of Eu²⁺ ions into the (SiC)_x-(AlN)_1-x host lattice, and Eu²⁺ ions tend to occupy Al sites of the host. The synthesized (SiC)_x-(AlN)_1-x:yEu²⁺ phosphors absorb light in the region of 250-425 nm and show a single and symmetric broadband emission centered at about 470 nm due to the 4f⁶5d-4f⁷ transitions of Eu²⁺. The luminescence intensity increases with the SiC content and reaches its maximum at x = 0.20. The critical quenching concentration of Eu²⁺ in the (SiC)_0.20-(AlN)_0.80:yEu²⁺ phosphor is about y = 0.006. The composition-optimized (SiC)_0.20-(AlN)_0.80:0.006Eu²⁺ phosphor shows a small thermal quenching, retaining the luminance of 91.1% at 150 °C. The CIE coordinates were measured as (0.135, 0.167) with high color purity. The above results indicate that (SiC)_x-(AlN)_1-x:yEu²⁺ is a promising candidate as a blue-emitting ultraviolet convertible phosphor for white LEDs, and the combustion reaction route is expected to be applicable to the synthesis of other kinds of nitride phosphors.