The narrow-band green-emitting phosphor Ba 2 LiSi 7 AlN 12 :Eu 2+ was discovered by analyzing a single particle in a powder mixture, which we call the Single Particle Diagnosis Approach. Single crystal X-ray diffraction (XRD) analysis of the particle revealed that Ba 2 LiSi 7 AlN 12 :Eu 2+ crystallizes in the Pnnm space group (No. 58) with a = 14.0941 Å, b = 4.8924 Å, c = 8.0645 Å, and Z = 2. The crystal structure is composed of a corner-sharing (Si,Al)N 4 corrugated layer and edge-sharing (Si,Al)N 4 and LiN 4 tetrahedra. Ba(Eu) occupies the one-dimensional channel in a zigzag manner. The luminescence properties were also measured using a single crystalline particle. Ba 2 LiSi 7 AlN 12 :Eu 2+ shows a green luminescence peak at approximately 515 nm with a narrow full-width at half-maximum (FWHM) of 61 nm. It shows high quantum efficiency (QE) of 79 % with 405-nm excitation and a small decrease of luminescence intensity, even at 300 °C.

Luminescent particles of Ba2LiSi7AlN12:Eu2+ are selected from polycrystalline material obtained by firing Ba3N2, EuN, Si3N4, AlN, and Li3N under N2 in the molar ratio of Eu:Si:Al:Li = 0.8:0.2:0.58:6.42:3 (BN crucible, 1800 °C, 2 h, 1 MPa N2).