Preparation of CaAlSiN₃:Eu²⁺ phosphors by the self-propagating high-temperature synthesis and their luminescent properties

Divalent europium-doped nitride phosphors, Ca_1-xEu _xAlSiN₃ (x = 0-0.2), were successfully prepared by the self-propagating high-temperature synthesis (SHS) by using Ca _1-xfu_xAlSi alloy powder as a precursor. The Rietveld refinement analysis was carried out on the CaAlSiN₃ host lattice to elucidate the luminescence properties of dopant Eu²⁺ on the tetrahedrally coordinated site. For the Eu²⁺ doped samples, strong absorption peaking at about 460 nm was observed on the excitation spectra, which matched perfectly with the current blue light of InGaN/GaN light-emitting diodes (LEDs). The optimized sample, Ca_0.98-Eu _0.02AlSiN₃, gave the red emission peaking at 649 nm of which the intensity was competitive with the sample prepared from the metal nitride raw materials (Ca₃N₂, AlN, Si₃N ₄, and EuN). The CIE chromaticity index (0.647, 0.347) with high color saturation indicated that it was a promising candidate as a redemitting phosphor for the InGaN/GaN-based down-conversion white LEDs for general illumination or displays.