Red-emitting oxonitridosilicate phosphors Sr2SiNzO4−1.5z:Eu2+ for white light-emitting diodes: structure and luminescence properties

Abstract

A novel red-emitting oxonitridosilicate phosphors, Sr₂SiN_zO_4−1.5z:Eu²⁺ (0.7 < z < 1.2), was prepared by solid state reaction in NH₃–N₂ atmosphere. The crystal structure was determined by Rietveld analysis on powder X-ray data. Sr₂SiN_zO_4−1.5z (0.7 < z < 1.2) crystallizes in an orthorhombic structure with the space group of Pmnb: ba−c (no. 62), and cell parameter a = 5.67366(5) Å, b = 7.09777(4) Å, c = 9.75112(1) Å. Sr₂SiN_zO_4−1.5z:Eu²⁺ (0.7 < z < 1.2) exhibited broad-band red emission centred at ∼620 nm (FWHM ≈ 95 nm) under blue light irradiation with a high QE value of 78.0% and good thermal stability, its emission intensity remains 87% at 150 °C of that measured at room temperature. The outstanding luminescent properties allow it to be an attractive red luminescent material for white LEDs.