Improved Thermal and Chemical Stability of Oxynitride Phosphor from Facile Chemical Synthesis for Vehicle Cornering Lights.

Orange Eu -doped phosphors are essential for light-emitting diodes for cornering lights to prevent fatal road accidents at night, but such phosphors require features of high thermal, chemical stability and facile synthesis. This study reports a series of yellow-orange-red emitting SrAl Si ON :Eu oxynitride phosphors, derived from the SrAlSi N nitride iso-structure by replacing Si -N with Al -O . The introduction of a certain amount of oxygen enabled the facile synthesis under atmospheric pressure using the air-stable raw materials SrCO , Eu O , AlN and Si N . SrAl Si ON has a smaller band gap and lower structure rigidity than SrAlSi N (5.19 eV vs 5.50 eV, Debye temperature 719 K vs 760 K), but exhibits higher thermal stability with 100 % of room temperature intensity remaining at 150 °C compared to 85 % for SrAlSi N . Electron paramagnetic resonance, thermoluminescence and density functional theory revealed that the oxygen vacancy electron traps compensated the thermal loss. Additionally, no decrease in emission intensity was found after either being heated at 500 °C for 2 hours or being immersed in water for 20 days, implying both of the thermal and chemical stability of SrAl Si ON :Eu phosphors. The strategy of oxynitride-introduction from nitride promotes the development of low-cost thermally and chemically stable luminescent materials.